Dissertations / Theses: 'Hydrometallurgy'

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Oguh, Ukachukwu I. "Multiphase contacting in PGM hydrometallurgy." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3375/.

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This thesis describes hydrodynamic studies of the leach and solvent extraction stages of a Platinum Group Metal (PGM) hydrometallurgical flowsheet. The studies were motivated by the need to increase PGM throughput in Johnson Matthey’s PGM refining business. In the leach stage, key components in the feed are selectively dissolved using acids in a stirred tank before they are recovered by liquid-liquid (L-L) solvent extraction and finally purified. The work described in this thesis tackles four main areas: hydrodynamic studies of L-L PGM solvent extraction in both mixer and settler stages, whilst for the leach stage, studies of particle behaviour in gas evolving solid-liquid (S-L) reactions and gas-liquid-solid (GLS) characterisation by a novel Electrical Resistance Tomography (ERT) technique are performed. In the mixer-settler, the effects of impeller diameter, D, to vessel diameter, T, ratio (D/T), the phase flow ratio, cφ/dφ; (where cφis the continuous phase flow fraction and dφ is the dispersed phase flow fraction) and the specific power input,Tε, upon the droplet size distribution in a L-L system and their phase separation were investigated. Changing a smaller D/T impeller for a larger D/T impeller at constant P/V and cφ/dφincreased droplet size because the maximum shear rate decreased as a result of increasing ratio of impeller pumping capacity (Q) with tip speed (Utip). Changing a larger cφ/dφfor smaller cφ/dφat a fixed P/V and D/T impeller increased droplet size because turbulent dampening increased since the average density, ρ ∝ dφ. Meanwhile, Kolmogoroff-Hinze’s theory was shown to apply for the measured relationship between Tε and droplet size. A settler design criterion, which relates the dispersed phase concentration (Ca) in the dispersion band to the dispersed phase throughput (Qd/A) agreed with the model by Ryon et al. (1959). Ca was significantly dependent on P/V and Qd/A, whilst the effects of Qc/Qd (where Qc is the continuous phase flowrate and Qd is the dispersed phase flowrate) and D/T were minimal. Droplet size analysis of the sedimenting region of the dispersion band and dense packed layer revealed a transitional distribution of droplet sizes due to the counteracting effects of droplet sedimentation, hindered settling and droplet-droplet coalescence. Particle behaviour in gas evolving S-L systems were quantified using the Zwietering ‘just-suspended’ impeller speed (Njs) condition in a sponge nickel® and sodium hypochlorite system. The presence of gas caused Njs to increase, however a coherent relationship between Njs in an ungassed and gassed system 3 could not be easily ascertained. Further work with Positron Emission Particle Tracking (PEPT) was advised to quantify the relationship. A well-known electrical concept called skin effect, which describes how the effective resistance of an electrical conductor varies as the frequency of an alternating current (AC) increases and decreases, was used to investigate GLS behaviour via a novel ERT spectroscopic technique. The process relies on the change in effective resistance of conducting objects with changing AC frequency to selectively detect different phases. The concept was initially validated with static phantoms of a stainless steel and plume of gas before being applied to dispersible stainless steel particles and gas. ERT spectroscopy showed that two AC frequencies (0.3 kHz and 9.6 kHz) could successfully isolate and simultaneously detect the gas and solid phases at a fixed current. By subtracting solids and gas conductivity, the change in solids and gas holdup were obtained.

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Zhang, Wensheng. "SO2/O2 as an oxidant in hydrometallurgy." Thesis, Zhang, Wensheng (2000) SO2/O2 as an oxidant in hydrometallurgy. PhD thesis, Murdoch University, 2000. https://researchrepository.murdoch.edu.au/id/eprint/458/.

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Zhang, Wensheng. "SO2/O2 as an oxidant in hydrometallurgy." Murdoch University, 2000. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20080115.141151.

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Matthews, Craig J. "Metal extractants based on benzimidazoles." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297532.

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MacLean, Donald William John. "The kinetics of zinc extraction in the di(2-ethylhexyl) phosphoric acid, n-heptane-zinc perchlorate, perchloric acid, water system." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30023.

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The kinetics of zinc extraction from perchlorate solutions with di(2-ethylhexyl) phosphoric acid in n-heptane have been measured using the rotating diffusion cell technique. The extraction of zinc is controlled by the mass transfer of reactants (Zn²⁺ and D2EHPA) to the interface. At low zinc concentrations, the system is controlled by the aqueous transport of Zn²⁺ to the interface; at higher zinc concentrations transport of D2EHPA becomes rate controlling. For the range of D2EHPA concentrations examined, the transport of D2EHPA is rate controlling. Bulk pH has a negligible effect, except perhaps at the lowest pH values examined, where there may be a slight decrease in extraction rate. This decrease was attributed to less favourable thermodynamics at low interfacial pH values. It appears that the chemical reaction rate is fast enough that it has a negligible effect on the overall extraction rate. A basic mathematical model was developed which is adequate for predicting the extraction rate under variable conditions of zinc concentration, D2EHPA concentration, and pH. The effect of using a partially loaded organic extractant was also investigated, and the system was found to be mass transfer controlled. An extended mathematical model was developed which predicts that the speciation of organic complexed zinc changes with increasing preload, and at high loadings the direction of ZnL₂HL and ZnL₂(HL)₂ flux reverses, with these species providing extractant to the interface. At very high loadings, ZnL₂HL provides almost all the extractant to the interface. Experimental studies of the effect of temperature on the rate of zinc extraction resulted in a calculation of the activation energy which was consistent with a diffusion controlled mechanism. Finally, the effect of different filter pore sizes on extraction was examined. The extraction rate decreases significantly with a very small filter pore size, while there appeared to be little or no effect for larger filter pore sizes. For the filter pore size used in this study, it was therefore concluded that the filter pores do not pose an additional resistance to mass transfer.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate

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De, Santis Donato. "Hydrogen reduction of lead from Kelex 100." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66077.

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7

Forgan, Ross Stewart. "Modification of phenolic oximes for copper extraction." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2764.

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The thesis deals with the modification of salicylaldoxime-based reagents used in hydrometallurgical extraction, addressing rational ligand design to tune copper(II) extractant strengths and also the development of reagents which are capable of transporting transition metal salts. Chapter 1 reviews current solvent extractant technology for metal recovery, including the limited knowledge of the effect of substituents on extractive efficacy. Advances in leaching technology have led to systems wherein increases in process efficiency could be obtained using reagents which can transport both a transition metal cation and its attendant anion(s), and the potential advantages of metal salt extractants are discussed. The problems encountered when trying to extract hydrophilic anions selectively into organic media are also considered. Chapter 2 discusses techniques used in industry to tune reagent properties, many of which depend on the importance of H-bonding in non-polar solvents. Synthesis of a series of 5-alkyl-3-X-2-hydroxybenzaldehyde oximes (X = a range of substituents) is described and copper extraction experiments are reported. 3-Substitution is found to alter reagent strength by two orders of magnitude, with 3-bromo-5-tert-butyl-2- hydroxybenzaldehyde oxime the strongest extractant. An analysis of X-ray structures of several ligands and copper(II) complexes is given in an attempt to establish whether trends in the solid state structures can account for variations in extractant strength. A more detailed analysis of the hydrogen bonding in salicylaldoximato copper(II) complexes and ligand dimers is carried out in Chapter 3, with the aim of defining how substituent effects could be used to design reagents with appropriate extractive behaviour. 3-X-2-Hydroxybenzaldehyde oximes with no 5-alkyl substituent are synthesised and subjected to a detailed study by X-ray crystallography and computational techniques, which, alongside evidence provided by CID-MS experiments, suggest that the dominant substituent effect in determining extractant strength is the ability to “buttress” the pseudomacrocyclic hydrogen bonding motif involving the oximic hydrogen and phenolic oxygen. Ligands with 3-substituents capable of accepting H-bonds were found to be stronger extractants than those which could not, and the steric hindrance afforded by bulky substituents made 3,5-di-tert-butyl-2-hydroxybenzaldehyde oxime the weakest extractant. Ligand acidity is also noted to have a significant effect on reagent strength, with electronwithdrawing substituents lowering the pKa of the phenolic proton and increasing extractive efficacy. Chapter 4 focuses on metal salt extraction, and the development of selective, robust and hydrolytically stable reagents. Six novel extractants, based on a salicylaldoxime scaffold with a pendant dialkylaminomethyl arm, are described. Only 5-tert-butyl-3- dihexylaminomethyl-2-hydroxybenzaldehyde oxime and 3-tert-butyl-5- dihexylaminomethyl-2-hydroxybenzaldehyde oxime have sufficient solubility to be effective reagents. The former extracts CuCl2 and ZnCl2 in a highly efficient manner, with one mole of metal salt extracted per mole of ligand, twice the expected capacity. X-ray structure determination of complexes of the related ligand 5-tertbutyl- 2-hydroxy-3-piperidin-1-ylmethylbenzaldehyde oxime defines the binding mode, with the chloride anions bound to the inner sphere of the metal cations. Loading and stripping experiments show it to be an extractant with potential commercial application. Cation and anion selectivity of the two extractants defined above is the focus of Chapter 5, which begins with an overview of techniques and attempts to attenuate the Hofmeister bias, the main factor in the selective extraction of hydrophilic anions into organic media. pH loading profiles show the 3- dihexylaminomethyl isomer to be an effective CuCl2 and CuSO4 extractant, but the cation extractive efficacy of the 5-isomer is hampered by the 3-tert-butyl group. Both ligands are found to be selective for Cl- > SO4 2-, following the Hofmeister bias. Further information on anion binding is provided by solid state structures of copper salt complexes, showing that in all cases the copper(II) cation interacts in some way with the anion. Cation extraction is affected significantly by the anion present, with FeIII selectively extracted against CuII in the presence of SO4 2- which is consistent with cation-anion interactions having great influence on the overall stability of the ligand-metal salt assembly.

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Mwewa, Brian. "Upgrading of PGM-rich leach residue by high pressure caustic leaching." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97876.

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Thesis (MEng)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: There is a lack of clear understanding of the rate of selenium (Se), arsenic (As) and sulphur (S) dissolution during caustic (NaOH) batch leaching of PGM-rich leach residue in the presence of oxygen. This has been a limitation in the optimisation of hydrometallurgical processes for the upgrading of PGM concentrates before refining the precious metals. Conditions to improve the rate of leaching of amphoteric elements while minimizing PGM losses were examined to enhance the performance of the leaching process. Development of intrinsic leaching rate equations represent the core of the overall batch leaching model developed in this study. The robustness of the model was assessed by its ability to accurately simulate the effects of changing operating parameters on the reaction extents. The effects of the interfacial oxygen mass transfer rate and temperature on the leaching rates were therefore also included in the overall model. The first part of the experimental program focussed on the interfacial oxygen mass transfer rate in the test autoclave. This enabled an accurate mathematical description of the interfacial mass transfer rate of the primary oxidant, diatomic oxygen (O2) molecule from the gas to the liquid phase. Mass transfer tests were conducted using the sodium sulphite method at 60°C, 100 kPa oxygen partial pressure and agitation speed of between 500 to 1000 rev/min. Cobalt(II) was used as the catalyst with a concentration range of 1 to 5 mg/L. Oxidation of amphoteric elements was investigated by leaching of PGM-rich leach residue (residue from sulphuric acid leaching of converter matte) in caustic solution. The test work was conducted to determine the intrinsic leaching rates in 0.125, 0.25 and 0.5 mol/L NaOH solutions in the 160° to 190°C temperatures range over a period of 6 hours. Oxygen partial pressure was maintained at 11 atm in the factorial experiments. The effect of oxygen partial pressure was quantified by conducting tests with oxygen partial pressure ranging from 7 to 16 atm. The intrinsic rate constants and activation energies derived from this test work were incorporated in the overall kinetic model to simulate the batch leaching profiles under real plant conditions. During the caustic pressure oxidation of amphoteric elements, the rate of oxidation was rapid during the first 10 minutes and decreased steadily over the course of experiment. The experimental results suggest that the oxidation kinetics are controlled by product layer diffusion with sulphur, selenium and arsenic (Arrhenius) activation energies of 31.8 kJ/mol, 26.1 kJ/mol and 10.7 kJ/mol respectively over the temperature range of 160 to 190°C. The reaction mechanism, as well as the observed kinetic behaviour, is most likely due to the base metal/PGMs hydroxide layer that formed as a result of precipitation. An increase in temperature increased the sulphur and arsenic reaction rates. The selenium reaction rate also increased as the temperature was increased from 160 to 175°C. A further increase in temperature above 175°C did not yield a significant increase in the reaction rate. An increase in the caustic concentration increased the reaction rates of all the elements. Increased oxygen partial pressure also improved the reaction rates, with the most significant change observed for sulphur oxidation; the extent of sulphur oxidation increased from 75 to 85% when oxygen partial pressure was increased from 7 to 16 atm. Reaction orders of 0.25, 0.12 and 0.21 with respect to hydroxide concentration and 0.37, 0.29 and 0.36 with respect to dissolved oxygen concentration were obtained for sulphur, selenium and arsenic respectively. Kinetic models were developed for sulphur, selenium and arsenic extraction. The sulphur and selenium simulation gave better agreement between the experimental and model predicted values, while the arsenic simulation gave a relatively poor prediction of the extractions. The caustic concentration had a notable effect on the dissolution of the PGMs. An increase in the caustic concentration increased the dissolution of platinum, palladium and ruthenium. Ruthenium dissolution also increased with an increase in temperature. To the contrary, platinum and palladium dissolution decreased with an increase in temperature. Rhodium and iridium precipitated and did not report in the solution phase while osmium could not be traced. The oxygen partial pressure did not have a significant effect on the dissolution rate of platinum, palladium and ruthenium.
AFRIKAANSE OPSOMMING: Daar is ‘n tekort aan die begrip van die tempo van seleen (Se), arseen (As) en swawel (S) oplosbaarheid gedurende bytsoda (NaOH) enkelladingsloging van platinum groep metaal (PGM)-ryk oorskot materiaal in die teenwoordigheid van suurstof. Hierdie inligting word benodig wanneer die optimisering van tipiese hidrometallurgiese prosesse wat PGM oorskot materiaal opgradeer verlang word. Hierdie bytsoda druklogingsproses vind tipies voor raffinering van die PGM metale plaas. Kondisies wat die tempo van amfoteriese element-loging verbeter, terwyl die PGM verliese geminimaliseer word, was in hierdie werk geondersoek om sodoende die effektiwiteit van die logingsproses te verbeter. Die ontwikkeling van intrinsieke logingtempo vergelykings vorm die kern van die algemene enkelladingsloging model wat ontwikkel was. Die robuustheid van hierdie model word geevalueer op sy vermoë om akkuraat die effekte van veranderende bedryfstelsel parameters op die logingstempo van betrokke reaksies te simuleer. Die effekte van suurstof tussenvlak massaoordrag en temperatuur was ook in die algehele model ingesluit. Die eerste deel van die eksperimentele program het gefokus op die suurstof tussenvlak massaoordrag in die outoklaaf. ‘n Akkurate wiskundige model wat die massaoordrag van die primêre oksidant, diatomiese suurstof (O2), van die gas fase na die vloeistof fase beskryf, was gebruik om die suurstof oordragtempo te kwantifiseer. Suurstof massaoordrag toetse het van die natrium sulfiet metode gebruik gemaak by 60°C, 100 kPa suurstof parsiële druk en tussen 500 en 1000 rev/min roerspoed. Kobalt(II) het gedien as katalis wat tussen 1 tot 5 mg/L gevarieer was. Die amfoteriese element oksidasie was volgende ondersoek deur die PGM-ryk oorskot materiaal te loog met bytsoda (wat stroomop onderwerp was aan swawelsuur loging van omskakelaar mat). Die toetswerk wou die intrinsieke logingtempo’s met 0.125, 0.25 en 0.5 mol/L NaOH oplossings by temperature 160 en 190°C oor 6 uur residensie tyd vasstel. Die suurstof parsiële druk was konstant gehou op 11 atm in hierdie faktoriale eksperimente. Die effek van suurstof parsiële druk was apart vasgestel, deur die suurstof parsiële druk te varieër vanaf 6 tot 16 atm. Die intrinsieke tempokonstantes en aktiveringsenergieë wat in hierdie toetswerk afgelei is, was in ‘n algehele kinetiese model ingekorporeer wat die enkellading logingsprofiele gesimuleer het by aanleg kondisies. Die tempo van oksidasie was vinnig in die eerste 10 minute en het geleidelik afgeplat, gedurende die bytsoda druk oksidasie van amfoteriese elemente. Die eksperimentele resultate suggereer dat produklaagdiffusie die oksidasie kinetika beheer met swawel, seleen en arseen (Arrhenius) aktiveringsenergieë as volg bereken in die temperatuur interval 160 tot 190°C: 31.8 kJ/mol, 26.1 kJ/mol en 10.7 kJ/mol. Die reaksie meganisme en kinetiese gedrag word hoogs waarskynlik veroorsaak deur die onedelmetaal/PGM hidroksied laag wat deur middel van presipitasie gevorm het. Temperatuur toename het die swawel en arseen se reaksietempo’s verhoog. Met seleen het die reaksietempo met temperatuur toename tussen 160 en 175°C ook verhoog, maar afplatting het by 175°C opwaarts plaasgevind. Oor die algemeen het die bytsoda konsentrasie die amfoteriese elemente se reaksietempo’s verhoog. Die verhoging van die suurstof parsiële druk het ook die reaksietempo’s verhoog. Swawel oksidasie het van 75 tot 85% verhoog vanaf 6 tot 16 atm, wat die mees noemenswaardige verandering was. Swawel, seleen en arseen reaksieordes van 0.25, 0.12 en 0.21 met hidroksied konsentrasie en 0.37, 0.29 en 0.36 met opgeloste suurstof konsentrasie het die beste paslyn op die eksperimentele data tot gevolg gehad. Hierdie data was gebruik om die kinetiese modelle van swawel, seleen en arseen ekstraksie te ontwikkel. Terwyl swawel en seleen ‘n goeie paslyn vir die eksperimentele data tot gevolg gehad het, kon passing van arseen ekstraksie nie ‘n goeie model oplewer nie. Varierende bytsoda konsentrasie het ‘n noemenswaardige effek op die PGM ontbinding gehad. Wanneer die bytsoda se konsentrasie vermeerder word, los daar meer platinum, palladium en rutenium op. Rutenium ontbinding het tydens ‘n temperatuur toename verhoog. In kontras het platinum en palladium ontbinding velaag tydens temperatuur toename. Rodium en iridium het gepresipiteer en was nie ontbind nie. Osmium kon nie gemeet word nie. Die suurstof parsiële druk het nie ‘n noemenswaardige effek op platinum, palladium en rutenium ontbinding gehad nie.

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Bezuidenhout, Chandon. "An electrochemical reduction process for the recovery of copper powder from a refinery effluent stream." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/24393.

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In recent years a significant amount of research has gone into the development of a feed pretreatment process for the concentrate refined at Anglo American Platinum's Precious Metals Refiners (PMR). Such a process has the potential to significantly simplify the downstream refining process and reduce the number of unit processes required for purification. One of the considered options involves a high temperature oxidative roast process followed by a high temperature hydrochlorination process to volatilise base metal chlorides and other impurities. The resulting precious group metal (PGM) concentrate is cleaner and thus requires significantly less process steps to final product. The off-gas from hydrochlorination contains predominantly silver, copper, nickel and iron. This off-gas undergoes a quench-scrub to condense the base metal chlorides. The quench-scrub liquor undergoes a dechlorination process with sulfuric acid to precipitate AgCl(s). The filtrate from this process then undergoes an electrochemical reduction process to recover copper metal concentrate. The objectives of this study were to: i. Determine the operating conditions for an electrochemical reduction process aimed at recovering copper as a copper powder from a sulfuric acid stream containing copper, nickel and iron. ii. Develop a conceptual flowsheet for a batch electrochemical process and estimate the capital cost and operating cost.

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Nesbitt, Allan Bernard. "A study of the decay of acid cationic ion exchange resin." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/24496.

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A study was undertaken on the decay of acid ion exchange resin from both a qualitative and quantitative perspective. The qualitative study concentrated on observing the impact on resin strength of varying electrolyte concentrations and varying di-vinyl benzene contents, during the loading phase. The phenomenon of osmotic shock in addition to resin cracking and swelling is clearly observed. A further qualitative study bore out the change in resin rigidity as the resin is artificially degraded through repeated loadings and regenerations performed by using a specially constructed device that cyclically loads and regenerates resin up to 1000 times in a three week period. Loss of resin rigidity was observed under these circumstances and was measured by means of observing changes in degree of swelling/contraction and changes in translucence. Quantitative study of the resin was limited to its characterisation through measurement of the equilibrium through the Mass-Action Law, capacity and resin kinetics. A study, of existing kinetic rigorous modelling methods and in particular the extensively published challenge of the multiple mechanism adsorption process, was undertaken. A rigorous model, that divorces the external and internal mass-transport parameters from the traditionally utilised lumped parameter, is proposed. All kinetic measurements were performed in a 1 litre closed circuit (finite system) consisting of a variable-pump, a five mL zero length column (ZLC) and a reservoir, allowing for the insertion of probes and sample extraction. An original method of model simulation for the purposes of fitting to kinetic data was developed and consists of determining the resin surface concentration from flux data assuming the applicability of Newton's Law of Cooling to the ionic flux through the external laminar layer. Simulation of flux inside the resin was achieved by assuming an internal homogeneous environment and the applicability of the Nernst-Plank equation that combines transport effects of both Fick's Law of Diffusion and inter-ion electrical forces to the flux of both the adsorbing and desorbing ions simultaneously, during the transient adsorption process.

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Spurr, Nicholas Robert Louis. "Interrelationship of hydrology, microbial colonisation and hydrometallurgy in a simulated chalcopyrite heap leach." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/11278.

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Includes bibliographical references (leaves 104-115).
Chalcopyrite is the most abundant primary copper sulphide mineral found worldwide. As copper grades of ores available for extraction decrease, heap bioleaching is gaining interest as a potential operating alternative to traditional methods of roasting and smelting. The efficiency by which bacteria assist leaching chalcopyrite is governed by their interaction and association to the sulphide mineral in the ore. While both planktonic and mineral-associated micro-organisms contribute to the bioleaching of mineral sulphides through the oxidation of ferrous iron little information exists as to their ability to adhere and leach low grade chalcopyrite ore. This study was undertaken to determine the association of defined and mixed microbial species on a chalcopyrite concentrate and a chalcopyrite ore. At. ferrooxidans, At. caldus, At. thiooxidans and L. ferrooxidans were grown in pure culture and used to investigate the mineral-microbe association within defined experimental parameters of two experimental operations.

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Ellis, Ross Johannes. "Chlorometallate extraction (base metals)." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/5938.

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The work outlined in this thesis was sponsored, in part, by Anglo American and concerns the development of new technologies to achieve the concentration and separation of base metal values in chloride hydrometallurgical circuits. New processes for the production of zinc, cobalt and nickel aim to use solvent extraction to achieve the separation of metal values in highly concentrated acid chloride feeds containing iron and this thesis involves new extractants for potential use in these circuits. Anion exchange solvent extraction was chosen as the most practical approach and so a range of new reagents are described which remove zinc(II), cobalt(II) and iron(III) chlorometallates from acid chloride solutions via the reaction: nL(org) + nH+ + MClx n- [(LH)nMClx](org) Chapter 1 reviews the literature which concerns base metal chloride hydrometallurgy, presents a range of commercial processes and discusses the chemistry which underpins them. This chapter also outlines the new Anglo American circuits and the general approach to the design of base metal chlorometallate extractants. In Chapter 2, the analytical methods are discussed. These methods include the solvent extraction experiments that were used to define the behaviour of the new ligands and the techniques that were employed to examine the interactions between an extractant and a chlorometallate anion. Chapter 3 presents a series of five new amido-functionalised pyridine reagents that were designed to investigate the affect of hydrogen bond donor functionality on the extraction of zinc, cobalt and iron chlorometallates. The pyridine nitrogen atom is sterically hindered in the new reagents to suppress formation of inner-sphere complexes. Solvent extraction performance was found to vary considerably with hydrogen bond donor functionality and ligand structure. The ligand 2-(4,6-di-tertbutylpyridin- 2-yl)-N,N’-dihexylmalonamide (L2) was the strongest and most efficient extractant in this series and this was attributed to a ‘proton chelate’ six-membered ring interaction between the malonamide oxygens and the protonated pyridine nitrogen that resulted in a pre-organised array of N-H and C-H donors that could interact favourably with the chlorometallate anion. Chapter 4 explores a series of six new tertiary amine-based ligands which contain varying amido-functionality, e.g. 3-(di-2-ethylhexylamino)-N-hexylpropanamide (MAA). Zinc, cobalt and iron chlorometallate extraction studies show the amide and malonamide-functionalised ligands are notably stronger than the tertiary alkylamine control, tris-2-ethylhexylamine (TEHA). Platinum(IV) extraction is also discussed, showing that some of the new reagents are more efficient than the tren-based ligands previously described,{Bell Katherine, 2008 #93} which were the most efficient known. The enhanced extraction performance of the new ‘MAA-type’ ligands was again attributed to the formation of a ‘proton chelate’ six-membered ring forming [(LH)2MCl4] assemblies in the organic phase. Conditions have been identified which would allow separation of Fe(III), Co(II) and Zn(II) in circuits which use the ‘MAAtype’ reagents. Chapter 5 explores a series of three new malonamide reagents which contain varying alkyl-chain functionality, e.g. N,N’-dimethylhexylpentadecylmalonamide (M1), which are thought to extract chlorometallate anions via protonation of the carbonyl oxygens. Zinc, cobalt and iron chlorometallate extraction studies demonstrate that the malonamide ligands show high efficiency and selectivity for iron over zinc and cobalt. Performance as chlorometallate extractants was found to vary considerably with ligand structure and hydrogen bond donor functionality in all three ligand series, with a number of ligands showing potential for commercial application. Analysis of anion-host interactions suggests that chlorometallate binding in the organic phase probably proceeds via an array of both N-H and C-H weak hydrogen bonding interactions between the extractant and the outer-sphere of the metallate complex.

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Edlin, Christopher David. "Tailored ligands for zinc coordination." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4787/.

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Selective coordination to zinc over other members of the first row transition metal series is important for the commercial application of lipophilic ligands for the hydrometallurgic recovery of the metal. In order to achieve selectivity for zinc(n) over other ions, particularly copper(II) and iron(III), ligands have to be designed which take advantage of zinc's preferred tetrahedral coordination geometry and the borderline donor atom preference of the metal. With such ligands in mind, three new classes of ligand system have been designed and synthesised based on the benzimidazole, quinoline and pyridine ring systems with appended phosphinic and thiophosphinic acid anionic donor groups. Benzimidazole ligands which bind zinc in a 2:1 manner in solution have been made and their complexation ability assessed by ESMS, (^31)p NMR, liquid-liquid extraction, fluorescence and UV absorption spectroscopic methods. A bisbenzimidazole ligand with a C(_3) spacer in the 2,2' position was synthesised and shown to bind zinc initially in a 2:1 manner, at low metal concentrations, and predominantiy as a 1:1 species at higher metal concentrations. The formation constant for the ML complex was shown to be logK(_ML)=5 by analysis of the NMR titration curve, which was in close agreement with the value obtained from liquid-liquid extraction studies. A directly linked 2,2'- bisbenziraidazole system was also synthesised as an extension to previous work, however isolation of the target ligand proved to be difficult due to the insolubility of the desired bis-acid.8-(Quinolinyl)phenylphosphinic acid and 8-(2-metiiylquinolinyl)phenylphosphinic acid were also synthesised and their solution complexation behaviour studied in detail. The unsubstituted ligand appeared to form 1:1 complexes with zinc at all the metal concentrations studied, and the absence of the methyl substituent does not inhibit coordination to the ferric ion. In contrast the metiiyl substituted ligand initially forms a 2:1 L:M complex, and 1:1 complexes at higher metal concentrations. The initial ML(_2) complex probably involves coordination of two of the phosphinic acid moieties. Three pyridyl derived ligand systems were also synthesised varying the bulk of the C-6 substituent and the effect of the phosphinic versus the thiophosphinic acid moiety towards zinc coordination was examined. Both of the methyl appended ligands were shown to bind zinc in a 2:1 manner, with the thiophosphinic acid exhibiting a greater avidity for zinc. In contrast, the unsubstituted ligand predominantly forms 1:1 complexes at all metal concentrations.

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Sarver, Emily Allyn. "The Ferrous Regeneration Process for Use in Alternate Anode Reaction Technology in Copper Hydrometallurgy." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34291.

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The Fe(II) regeneration process is an important aspect of Alternate Anode Reaction Technology (AART) using Fe(II)/Fe(III)-SO2 reactions for copper hydrometallurgy; however little has been done to study it specifically. The process regenerates Fe(II) via Fe(III) reduction by SO2(aq), catalyzed by activated carbon particles. To better understand and improve the process, two studies have been conducted with respect to variable factors and their affects on the regeneration. A study of fundamental kinetics confirms that the regeneration reaction is mass transfer-controlled, requiring adsorption of reactants onto the catalyst surface for reaction. The reaction rate is limited by the diffusivity of Fe(III). Initial Fe(III) concentration and carbon particle size are determined to be the most influential factors on the rate under the condition studied. Furthermore, it is observed that flow rate may inhibit the reaction by reducing ion diffusivity. A rate expression for the regeneration is derived and experimentally validated, and the Fe(III) diffusivity is determined to be 1.1x10-7 cm2/s. An optimization problem is also developed and solved for the process, constrained by the requirement that negligible SO2 could be present in the process effluent. Before optimization, a relationship is developed between regeneration rate and variable factors. Again, carbon size and initial Fe(III) are the most influential factors on the regeneration rate, related to it linearly; temperature is significant with a squared relationship to the rate; initial SO2 is insignificant. Optimal conditions are found with minimum carbon particle size, maximum initial Fe(III) concentration, and moderate temperature.
Master of Science

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15

Lin, Tai. "Strength, transport efficiency and selectivity of novel extractants for the recovery of base metals." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3927.

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This thesis concerns the development of new types of solvent extractants for use in the hydrometallurgical recovery of base metals, and addresses the ligand design features which are needed to control the strength, transport efficiency and selectivity of these extractants. Chapter 1 provides background on the development of extractive metallurgy, e.g. pyrometallurgy and hydrometallurgy, and introduces the history, basic terminology and various processes and reagents involved. Solvent extraction as a hydrometallurgical technique to achieve the recovery of base metals is discussed in most detail. The design criteria of extractants are highlighted as the focus of the whole thesis. Chapter 2 investigates the potential of salicylaldehyde hydrazones as cation exchange extractants for hydrometallurgical recovery of copper, and studies substituent effects, e.g. electronic, steric and particularly “buttressing” of ligand-ligand hydrogen bonding, on the strength and efficacy of the extractants. A series of 3-substituted (X) and N-substituted salicylaldehyde hydrazones has been developed. Solvent extraction experiments show that the 3-substitution can increase the distribution coefficient of the methylhydrazone for copper extraction by more than three orders of magnitudes along the series (X) Me < OMe ≤ H < Br < NO2. Both the phenol acidity and intermolecular hydrogen bonding are significantly influenced by the 3-substituent as judged by a systematic NMR study on the solution speciation of the free ligands. Electron-withdrawing groups which also act as hydrogen bond acceptors (X = NO2 or Br) are particularly effective in enhancing the strength of the methylhydrazones. Compared to the commercially applied salicylaldoximes, the hydrazones are weaker extractants, and the strength varies in the order: oximes > methylhydrazones > phenylhydrazones. This order probably arises from a combination of variations in the phenol acidities and the strength of the hydrogen bonding motifs, which are also probed in the free ligands using NMR techniques. Chapter 3 considers reagents capable of extracting metal salts and deals with the development of polytopic salicylaldimine ligands bearing pendant tertiary amine groups for the hydrometallurgical recovery of zinc chloride. These extractants show extremely high transport efficiency of metal salts with more than two moles of ZnCl2 loaded per mole of ligand, and high chloride over sulfate selectivity in solvent extraction experiments. The unusual multiple loading suggests the extraction of chlorozincate as anion species, which is supported by the elemental analysis and ESI MS spectra of the formed complexes. The zinc chloride dependent extraction and stripping experiments further indicate that the extraction process is controlled by the Cl- activities in the aqueous solutions. 1H NMR studies show that two different complexes are successively formed in solution as the ligand to zinc stoichiometry is increased to 1L : 2ZnCl2, with the first formed by extracting the zinc cation at low ZnCl2 concentrations and the second likely resulting from the further extraction of chlorozincate at high ZnCl2 concentrations. An extraction mechanism is proposed in which a tritopic assembly [ZnLCl2] forms by binding the Zn2+ cation with the N2O2 2- site of the “salen” type ligands and two Cl- anions with the protonated pendant amine groups and then a ditopic assembly [ZnL(ZnCl4)] forms by extracting the [ZnCl4]2- anion when the reagent is contacted with high tenor ZnCl2 feed. The possible formation of tritopic assemblies [ZnL(ZnCl3)2] accounts for Zn-loadings higher than 200%. The ligand design features such as the benefits of combining cation and anion binding sites in the same molecule are indicated by comparing the polytopic ligands with a series of dual host pairs of the salen ligand and hydrophobic amines. The polytopic ligands show potential for industrial application as ZnCl2 extractants. Finally chapter 4 focuses on the anion binding and selectivity involving simple anions and chlorometallates in solvent extraction by the polytopic ligands discussed in chapter 3 and their metal complexes. A novel and reliable method for chloride analysis in the presence of complexing metal cations has been developed using excess silver(I) to precipitate chloride and then analyze the silver content by ICP-OES technique. Multiple loadings of chloride are achieved by the polytopic ligands, which confirms the uptake of metal salt as ZnCl2, and is desirable for excellent material balances in hydrometallurgical processes. The anion binding of the copper-only complex [Cu(L-2H)] supports the proposed extraction mechanism by indicating that one mole of zinc is extracted in the likely form of chlorozincate anions when the cation binding site is occupied by Cu2+. The polytopic ligands and their copper-only complexes [Cu(L-2H)] show the same anion selectivity following the order [ZnCl4]2- > Cl- > SO4 2-, which can be explained by the hydration energies of these anions. Extractions from ZnCl2, ZnSO4, Zn(NO3)2 or mixed feed solutions indicate that the zinc transport efficiency is also dependent on the nature of counter anions.

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16

Sampson, Mark Ian. "Influence of the cell properties of acidophilic bacteria during attachment to mineral sulfides and consumption during the oxidation of ferrous iron." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297789.

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17

Taggart, Diane. "Evaluating the effect of alternative neutralising agent and seeding on the zinc recovery through the Zincor iron removal circuit." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20326.

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Zincor's average zinc recovery was 90.29 % (for the period of 1 January 2009 to 30 September 2011), which was well below the industry standard of 96 %. Due to limitations in Zincor's iron removal technology, the maximum achievable recovery was 94 %. The zinc loss through the iron residue was the second biggest contributor to the overall zinc losses, so that there was much room for improvement. The calcine used for neutralisation in the Iron Removal Stage contained a portion of insoluble zinc ferrite. The insoluble zinc loss through the iron residue was associated with the presence of the insoluble zinc ferrite, as well as the phenomenon of coating of unleached neutralising agent by iron precipitate. The soluble zinc loss was a function of the dewatering characteristics of the precipitate. The work included the evaluation of alternative neutralising agents to supplement or replace calcine, as well as the implementation of a seed recycle. A review of literature found that the use of an alternative neutralising agent that contained little or no zinc could potentially reduce the insoluble portion of the zinc loss. Secondly, the presence of seed could potentially reduce both the soluble and insoluble zinc losses by promoting agglomeration growth and providing additional surface area for precipitation to occur (thereby reducing coating of zinc-rich neutralising agents). The laboratory work evaluated a number of alternative neutralising agents, but focused on the use of DRC oxide and limestone for neutralisation. These were evaluated separately and in combination, with and without a seed recycle.

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18

Owusu, Gyebi Prince. "Investigating the rheological behavior of Witbank coal water mixtures." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20984.

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South Africa has large low-grade coal reserves. With the prospect of expanding its coal demands for exports and power generation, it is important that the beneficiation and transport of coal in the country are economical. The current mode of transporting coal has some drawbacks, which include inefficient rail infrastructure, long distances, and several environmental concerns related to air pollution, water pollution, and traffic risks. It is, therefore, important to investigate efficient means of coal transportation, which will also reduce environmental impacts. The transport of highly concentrated coal-water slurries through pipelines has attracted the attention of many researchers as an efficient and economical means of fine coal utilization. The primary objectives of this study are to investigate the importance of surface charge, solids concentration and particle size on the stability and rheological behaviour of Witbank coal. This work was carried out to arrive at a sounder discernment of the function of dispersion addition on coal-water mixtures rheology and stability.

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19

Rademan, Johan Andries Muller. "The simulation of a transient leaching circuit." Thesis, Link to the online version, 1995. http://hdl.handle.net/10019/3146.

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20

Littlejohn, Patrick Oliver Leahy. "The enhancing effect of pyrite on the kinetics of ferrous iron oxidation by dissolved oxygen." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/3324.

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The oxidation of ferrous in acidic sulfate media by dissolved oxygen is an important reaction in any sulfide mineral leach process that uses ferric as a surrogate oxidant. Ferric is reduced as it oxidizes metal sulfides, and the resulting ferrous is re-oxidized by dissolved oxygen. The oxidation of ferrous to ferric by dissolved oxygen is quite slow outside of elevated pressure-temperature autoclaves. However, pyrite in solution has been found to have a catalytic effect on the reaction, speeding it up significantly. This effect is particularly significant in the context of the Galvanox™ acidic sulphate atmospheric leach process. To quantify the kinetics of this reaction and the effect of pyrite, tests were run in an atmospheric batch reactor with constant tracking of pH and redox potential. The kinetics of this reaction were quantified with respect to primary variables such as acidity, pyrite pulp density, temperature, and total iron concentration. Secondary factors such as copper concentration, gas liquid mixing rate and the source of pyrite mineral were also considered. Redox potential is a logarithmic function of the ratio of the activity of free ferric to free ferrous and is complicated by speciation within the Fe(III)-Fe(II)-H₂SO₄-H₂O system. Correlating redox potential data with extent of reaction was achieved by using permanganate redox titration and the isokinetic technique to link redox potential data directly to the fraction of ferrous reacted. This technique is effective over the potential range of interest – 360 to 510 mV vs Ag/AgCl. Under these conditions the leaching rate of pyrite is appreciable, so the rate of pyrite dissolution was predicted with the shrinking sphere model developed by Bouffard et al. Ferrous oxidation in solution was simulated with an adjusted version of the model of Dreisinger and Peters, which also accounts for the catalytic effect of dissolved copper. Oxygen solubility was predicted using the model of Tromans. Experimental data show a clear enhancing effect of pyrite on ferrous oxidation. A mathematical model of this effect applicable to the conditions of Galvanox™ leaching is presented.

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21

Lack, Barbara Anne. "Electrochemical studies of gold bioaccumulation by yeast cell wall components." Thesis, Rhodes University, 1999. http://hdl.handle.net/10962/d1004969.

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Gold, amongst other group 11 metals, was almost certainly one of the first three metals known to man. In addition to the economic importance of the metal, gold has a wide variety of applications in the medical, electrocatalytical and micro-electronics fields. However, the determination of gold ions in solution, with accuracy, precision, sensitivity and selectivity is still an interesting and much debated topic in analytical chemistry. A system whereby gold ions have been successfully detected employing an electrochemical technique, known as stripping voltammetry, has been developed. The electrochemical method was chosen over other available techniques for the sensitivity, particularly at low concentrations, and selectivity properties; notably in the presence of other metal ions. Under acidic conditions, the electrochemical technique was applied and the presence of gold(III), at a concentration of 2.53 x 10⁻⁵ mol dm⁻³ in a mine waste water sample, was detected. Biomass, in particular yeast and algal types, have been successfully employed in extracting low concentrations of gold ions from industrial effluents. The manipulation of the biological facility for mineral interaction, biohydrometallurgy, may yield numerous potential new technologies. South Africa in particular would benefit from this area of research, since the country is a major ore and metal refining country and if the output and the efficiency of the mines could be improved, even by a small percentage, the financial rewards would be vast. In this study, the application of adsorptive cathodic stripping voltammetry (AdCSV) of gold(III) in the presence of various Saccharomyces cerevisiae cell wall components, was investigated to determine which, if any, were involved specifically in the chemical binding of the gold ions. The chitin and mannan extracts showed the most promise with detection limits of 1.10 x 10⁻⁶ mol dm⁻³ and 9 x 10⁻⁹ mol dm⁻³, respectively; employing the AdCSV technique. A modification of the stripping voltammetry technique, Osteryoung square wave stripping voltammetry (OSWSV), provided the lowest detection limit, for gold(IIl) in the presence of mannan, of 1.70 x 10⁻¹¹ mol dm⁻³ ; utilising a modified carbon paste electrode. The detection of gold(III) has been shown to be dependent on the type of electrode employed, the electrolyte solution and the presence of interfering agents. The effect of copper(II) and silver(I) on the detection of the gold(III) in solution was investigated; whilst the silver(I) has shown no detrimental effects on gold (III) detection systems, copper(II) has indicated the possibility of forming an inter-metallic compound with the gold(III). However, mannan has shown to selectively and preferentially bind the gold(III) in the presence of a ten-fold excess of copper(II). Nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy, as well as computer modelling techniques were employed to further investIgate the mannan-gold(III) interaction and proposed complex formed. The NMR, IR and computer modelling data are in agreement with the electrochemical data on proposing a mannan-gold(III) complex. The co-ordination site was established to be in the vicinity of the H-I and H-2 protons and the gold(III) adopts a square-planar geometry upon co-ordination. The benefits of the research are useful from a biological perspective (i. e. as more is known about the binding sites, microbiologists/biochemists may work on the optimisation of parameters for these sites or work could be furthered into the enhanced expression of the sites) and an industrial one. In addition to the' two major benefits, an improved understanding of gold and its chemistry would be achieved, which is advantageous for other fields of research as well.

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22

Tong, Libin. "Sulfur dispersing agents for nickel sulfide leaching above the melting point of sulfur." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/3427.

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The effects of sulfur dispersing agents (SDAs) in the oxygen pressure leaching of nickel concentrate at medium temperature were investigated. Liquid sulfur-aqueous solution interfacial tensions and liquid sulfur-sulfide mineral contact angles were measured at 140ºC, 690 kPa overpressure by nitrogen, and 1.0 mol/L NiSO₄. The effects of SDAs including lignosulfonate, Quebracho, o-phenylenediamine (OPD), and humic acid were evaluated by the calculation of the work of adhesion in the liquid sulfur-sulfide mineral-aqueous solution systems. It was found that the sulfide mineral surface is sulfophobic at pH from 4.1 to 4.5 due to the hydrolysis of nickel (II) ions to nickel hydroxide and the deposition of nickel hydroxide on the mineral surface. These findings apply to four different sulfide mineral systems, including pentlandite, nickeliferous pyrrhotite, pyrrhotite, and chalcopyrite. Lignosulfonate, Quebracho, and humic acid were found to significantly reduce the work of adhesion indicating they should be effective SDAs. OPD is ineffective in changing the work of adhesion of sulfur on the mineral sulfides indicating that it is not a good candidate for sulfur dispersion. The adsorption behavior of SDAs, including lignosulfonate, Quebracho, OPD, and humic acid on elemental sulfur and on nickel sulfide concentrate was investigated. Lignosulfonate, Quebracho, and humic acid were characterized by their infrared spectra. The charge changes on elemental sulfur surface were characterized by the measurement of the electrokinetic sonic amplitude (ESA) in the absence or presence of SDAs. The adsorption of lignosulfonate on molten sulfur surface was calculated by the Gibbs Equation. The adsorption of lignosulfonate, Quebracho, and humic acid on the nickel concentrate was investigated at ambient temperature. The adsorption of lignosulfonate, Quebracho, and humic acid on the nickel concentrate was found to be monolayer adsorption, which was fitted to the Langmuir adsorption isotherm. Electrostatic interaction and ion-binding are the possible mechanisms for the adsorption of lignosulfonate and humic acid on the nickel concentrate. Quebracho is adsorbed on the nickel concentrate through hydroxyl and sulfonate groups. OPD cannot adsorb on the molten sulfur surface. OPD undergoes chemical change in aqueous solution in the presence of ferric at ambient temperature. Oxygen pressure leaching experiments were performed at 140 or 150ºC under 690 kPa oxygen overpressure. The particle size of the nickel concentrate was found to be an important factor in leaching. During the leaching of nickel concentrate with P₈₀ of 48 µm, the SDAs were believed to be fully degraded before nickel was fully extracted. At most 66% nickel was extracted in the presence of 20 kg/t OPD. Fine grinding (P₈₀ of 10 µm) was sufficient for 99% nickel recovery at low pulp density while at high pulp density, the nickel extraction increased from 95% to 99% with addition of SDAs. Based on the leaching results on a nickel concentrate sample (-44 µm), OPD had the effect of increasing the nickel extraction to about 99%, followed by Quebracho (83%), lignosulfonate (72%), and humic acid (61%). It is suggested that the oxidation product of OPD is effective in solving the sulfur wetting problem in leaching. 97% nickel was recovered in the presence of 5 g/L chloride ion. Chloride ion has an effect to enhance the performance of lignosulfonate under leaching conditions.

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23

Alvarado, Blohm Fernando Jose. "Determination of Hydraulic Conductivities through Grain-Size Analysis." Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:106982.

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Thesis advisor: Alfredo Urzua
Thesis advisor: John Ebel
Nine empirical equations that estimate saturated hydraulic conductivity as a func- tion of grain size in well-graded sands with gravels having large uniformity coecients (U > 50) are evaluated by comparing their accuracy when predicting observed conduc- tivities in constant head permeability tests. According to the ndings of this thesis, in decreasing order of accuracy these equations are: USBR (Vukovic and Soro, 1992; USBR, 1978), Hazen (Hazen, 1892), Slichter (Slichter, 1898), Kozeny-Carman (Carrier, 2003), Fair and Hatch (Fair and Hatch, 1933), Terzaghi (Vukovic and Soro, 1992), Beyer (Beyer, 1966), Kruger (Vukovic and Soro, 1992), and Zunker (Zunker, 1932). These re- sults are based on multiple constant head permeability tests on two samples of granular material corresponding to well-graded sands with gravels. Using the USBR equation sat- urated hydraulic conductivities for a statistical population of 874 samples of well-graded sands with gravels forming 29 loads from a heap leaching mine in northern Chile are calculated. Results indicate that, using the USBR equation, on average the hydraulic conductivity of the leaching heaps has a two standard deviation range between 0.18 and 0.15 cm/s. Permeability tests on the actual material used in the heaps provided by the mine shows that the results presented in this thesis are consistent with actual observa- tions and represent saturated conductivities in heaps up to 3 m high under a pressures of up to 62 Kpa. In future work hydraulic conductivities can be combined with water retention curves, discharge rates, irrigation rates, porosities, and consolidation so as to evaluate the relationship between copper yields and the hydraulic conductivities of the heap
Thesis (MS) — Boston College, 2016
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Geology and Geophysics

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24

Rodarte, Alma Isabel Marín. "Predispersed solvent extraction." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/45173.

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A new solvent extraction method has been developed for the extraction of metal and organic ions from very dilute aqueous solutions. The new method, which has been named Predispersed Solvent Extraction (POSE), is based on the principle that 1 there is no need to comminute both phases. All that is necessary is to comminute the solvent phase prior to contacting it with the feed. This is done by converting the solvent into aphrons, which are micron-sized globules encapsulated in a soapy film. Since the aphrons are so small, it takes a long time for the solvent to rise to the surface under the influence of gravity alone. Therefore, the separation is expedited by piggy-back flotation of the aphrons on specially prepared gas bubbles, which are somewhat larger than aphrons and are called colloidal gas aphrons (CGA).

Copper, uranium and chromium ions, and alizarin yellow were extracted from very dilute aqueous solutions using PDSE. Tests were performed in a vertical glass column in both batch and continuous modes, and in a continuous horizontal trough. The new solvent extraction procedure worked very efficiently and very quickly under laboratory conditions. Higher than 99% extraction was achieved in many of the tests performed.

Master of Science

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25

Barton, Isabel Fay, and Isabel Fay Barton. "Mineralogical and Metallurgical Study of Supergene Ores of the Mike Cu-Au(-Zn) Deposit, Carlin Trend, Nevada." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/625323.

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This paper presents the results of a mineralogical and metallurgical study of supergene ores at the Mike Cu-Au(-Zn) deposit on the Carlin trend of Nevada, USA, currently held by Newmont Gold Corporation. With a metal endowment totaling >8.5 M oz. Au, 1027 M lbs. Cu, and 809 M lbs. Zn, Mike is one of the largest deposits on the Carlin trend, but it is currently uneconomic to develop. It contains an unusual and complicated suite of metals and ore minerals. This study was undertaken as a first step to investigate process options for recovering both its Cu and Au by 1) comparing the metal recoveries achieved from the supergene ores by six different lixiviants, and 2) identifying which minerals failed to dissolve in each lixiviant. The reagents selected were sulfuric, sulfurous, and methanesulfonic acids, to recover Cu, and cyanide, thiourea, and glycine, to recover Cu and Au. QEMSCAN and SEM study of six samples of different ore types and grades indicate that the Au occurs as varieties of native gold, including auricupride and electrum. Major Cu minerals are native Cu, cuprite, malachite, chrysocolla, and conichalcite (Ca-Cu arsenate), with locally significant Cu in jarosite and goethite. Gangue mineralogy is dominated by quartz, sericite, chlorite, alunite, smectite and kaolinite, K-feldspar, jarosite, and iron oxides. Bottle roll testing indicates that no single-step leaching process is likely to provide economic recovery of both Cu and Au. Sulfuric and methanesulfonic acid both recovered > 70% of the Cu except from the samples dominated by conichalcite, which was not leached effectively by any of the reagents tested. Only cyanide and thiourea recovered significant Au. Reagent consumption for cyanide, sulfuric acid, and methanesulfonic acid was generally within acceptable levels. Glycine and sulfurous acid are both uneconomic based on low recovery. Further work will focus on developing an economic process in two steps. Mineralogical study of QEMSCAN residue indicates that the non-leaching ore minerals are conichalcite and Cu-bearing Fe oxides. In addition, native Cu and cuprite do not leach well in glycine and chrysocolla does not leach well in thiourea or cyanide. Other observed mineralogical changes include the total loss of dolomite and partial loss of alunite and iron oxide from all samples, with apparent gains in jarosite.

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26

Chinyama, Luzendu Gabriel. "Recovery of Lithium from Spent Lithium Ion Batteries." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-59866.

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Batteries have found wide use in many household and industrial applications and since the 1990s, they have continued to rapidly shape the economy and social landscape of humans. Lithium ion batteries, a type of rechargeable batteries, have experienced a leap-frog development at technology and market share due to their prominent performance and environmental advantages and therefore, different forecasts have been made on the future trend for the lithium ion batteries in-terms of their use. The steady growth of energy demand for consumer electronics (CE) and electric vehicles (EV) have resulted in the increase of battery consumption and the electric vehicle (EV) market is the most promising market as it will consume a large amount of the lithium ion batteries and research in this area has reached advanced stages. This will consequently be resulting in an increase of metal-containing hazardous waste. Thus, to help prevent environmental and raw materials consumption, the recycling and recovery of the major valuable components of the spent lithium ion batteries appears to be beneficial. In this thesis, it was attempted to recover lithium from a synthetic slag produced using pyrometallurgy processing and later treated using hydrometallurgy. The entire work was done in the laboratory to mimic a base metal smelting slag. The samples used were smelted in a Tamman furnace under inert atmosphere until 1250oC was reached and then maintained at this temperature for two hours. The furnace was then switched off to cool for four hours and the temperature gradient during cooling was from 1250oC to 50oC. Lime was added as one of the sample materials to change the properties of the slag and eventually ease the possibility of selectively leaching lithium from the slag. It was observed after smelting that the slag samples had a colour ranging from dark grey to whitish grey among the samples.The X - ray diffractions done on the slag samples revealed that the main phases identified included fayalite (Fe2SiO4), magnetite (Fe3O4), ferrobustamine (CaFeO6Si2), Kilchoanite (Ca3Si2O7), iron oxide (Fe0.974O) and quartz (SiO2). The addition of lime created new compound in the slag with the calcium replacing the iron. The new phases formed included hedenbergite (Ca0.5Fe1.5Si2O6), ferrobustamine (CaFeO6Si2), Kilchoanite (Ca3Si2O7) while the addition of lithium carbonate created lithium iron (II) silicate (FeLi2O4Si) and dilithium iron silicate (FeLi2O4Si) phases.The Scanning Electron Microscopy (SEM) micrographs of the slag consisted mainly of Fe, Si and O while the Ca was minor. Elemental compositions obtained after analysis was used to identify the different phases in all the slag samples. The main phases identified were the same as those identified by the XRD analysis above except no phase with lithium was identified. No lithium was detected by SEM due to the design of the equipment as it uses beryllium planchets which prevent the detection of lithium.Leaching experiments were done on three slag samples (4, 5 and 6) that had lithium carbonate additions. Leaching was done for four hours using water, 1 molar HCl and 1 molar H2SO4 as leaching reagents at room temperature. Mixing was done using a magnetic stirrer. The recoveries obtained after leaching with water gave a lithium recovery of 0.4%. Leaching with HCl gave a recovery of 8.3% while a recovery of 9.4% was obtained after leaching with H2SO4.It can be concluded that the percentage of lithium recovered in this study was very low and therefore it would not be economically feasible. It can also be said that the recovery of lithium from the slag system studied in this work is very difficult because of the low recoveries obtained. It is recommended that test works be done on spent lithium ion batteries so as to get a better understanding of the possibilities of lithium recovery as spent lithium ion batteries contain other compounds unlike the ones investigated in this study.

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27

Roach, Benjamin David. "Phenolic oxime copper complexes : a gas phase investigation." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/7582.

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This thesis explores the use of mass spectrometry to define the strengths, and understand solution phase speciation of phenolic oxime-based solvent extractants of the types used in the hydrometallurgical recovery of copper. Chapter 1 reviews briefly the current extraction technology for copper and focuses on hydrometallurgy and the use of phenolic oximes such as 5-nonylsalicylaldoxime. The modification of the latter to improve extraction efficiency is discussed, focussing on the introduction of X-substituents in the 3 position of the benzene ring. Modern mass spectrometry techniques are also discussed with a focus on their application to inorganic systems and their use in achieving the aims of this thesis, as defined above. The work described in chapter 2 involves the development of collision induced dissociation (CID) techniques to determine the relative gas phase stabilities of copper complex anions of the type [Cu(L)(L-H)]-, where LH is a 5-alkyl-3-X-2- hydroxybenzaldehyde oximes and X a range of substituents. The importance of interligand interactions in the outer-coordination sphere and their influence on gas phase anion stability, as defined by CID, is reported. The work described in Chapter 2 on CID is extended in chapter 3 and looks at the effect of charge, of ligand type, LH, and of the nature of the metal on the stability of ionic forms of [M(L)2] complexes, where LH is extended to include 5-alkyl-2- hydroxyphenylethanone oximes. The effects of substitution at the azomethine carbon atom and at the 3-position of the benzene ring and of variation of the nature of the metal on the ion dissociation mechanisms are shown to have a major influence on ion stability under CID conditions. In chapter 4 density functional theory calculations have been used to investigate the influences of substitution at the azomethine carbon atom and at the 3-position of the benzene ring and of variation of the nature of the metal on the gas phase structures of the neutral complexes, [M(L)2]. Gas phase deprotonation and dimerisation enthalpies of the ligands, LH, and enthalpies of formation of [M(L)2] complexes have been calculated and correlates with experimentally determined ligand extraction strength. The ligand type has been extended to include 3-X-2-hydroxybenzaldehyde hydrazones, which have previously been shown to have lower distribution coefficients for copper than the analogous 3-X-substituted oximes. The calculated gas phase formation enthalpies for [M(L)2] show a strong correlation with the strengths as extractants LH, measured as their pH0.5 values for metal uptake. Chapter 5 considers whether mass spectrometry can be used to define the solution equilibria when two different oxime-based ligands, LXH and LYH, compete for Cu(II) in a single phase solution. It has been established that shifts in the relative peak intensities of deprotonated ions derived from the Cu(II) complexes, [Cu(LX)2], [Cu(LY)2] and [Cu(LX)(LY)] reflect changes in the solution composition. The work described in chapter 6 extends the study of solution phase speciation using mass spectrometry. When the Cu(II) and proton concentrations of solutions were varied distinct changes in the resulting electrospray mass spectra were observed and the resulting species were identified using CID and high resolution mass spectrometry. A novel, [Cu3(L-H)3-μ3-O/OH]- species is determined to be a major component of solutions where Cu(II) concentrations are equal to/greater than the LH concentration. Various 3-X-2-hydroxybenzaldehyde oximes (X = CH2NR2) were synthesised. The incorporation of a protonatable arm in the 3-position enabled trinuclear complexes, [Cu3(L-H)3-μ3-OH], to be isolated and fully characterized, including two X-ray determined crystal structures.

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28

Pelser, Max. "The control of calcium and magnesium in a base metal sulphate leach solution." Thesis, Stellenbosch : University of Stellenbosch, 2003. http://hdl.handle.net/10019.1/16409.

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Thesis (MScIng)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: This thesis investigates the control of calcium and magnesium in a base metal sulphate leach solution containing nickel and cobalt. The presence of calcium and magnesium in the hydrometallurgical processing of base metals, result in a number of difficulties. These problems range from the contamination of the final product, to high energy consumption and large bleed streams during electrowinning. Calcium poses a greater problem in sulphate solutions due to the low solubility of its sulphate salts. No conventional method exists for the control of calcium and magnesium. As part of this study a review of possible control methods was conducted, which is listed within. From this list the precipitation of fluorides was selected for further investigation. The results showed that it is possible to control calcium and magnesium through the precipitation of their respective fluorides, without the co-precipitation of nickel and cobalt. For 10% stoichiometric excess of fluoride 96.5% calcium and 98.5% magnesium were removed during batch experiments. It is known that mixing and hydrodynamics plays an important role on the characteristics of the formed precipitate, making these processes inherently difficult to scale-up. To evaluate these effects on a continuous process, the three-zone model proposed by Gösele and Kind (1991) was used. A precipitate with consistent characteristics was produced while varying the mixing on the macro, meso and micro scale. Additionally, methods were investigated for the removal or possible recycling of the unreacted fluoride, for which activated alumina was identified. It was observed that activated alumina could adsorb fluoride to low levels in the presence of the base metal solution, after which it could be regenerated again. The activated alumina (AA) had a capacity of 8.65 gF/lAA at a 10 mg/l fluoride breakthrough level during column tests. Based on the experimental results a conceptual process was devised whereby only a portion of the leach stream is subjected to the fluoride precipitation process, after which it is returned to lower the overall calcium and magnesium concentrations. This method would reduce the effect of the observed dominance of magnesium precipitation, in processes where the maximum removal of both elements is not required. The fluoride precipitation process consisted of three steps being precipitation, solid-liquid separation and adsorption of the unreacted fluoride. Sufficient information is provided on the process for a cost estimation to be carried out. Should this found to be feasible, a continuation of the project is recommended. Different reactor configurations could be evaluated for precipitation. The scaling observed during the continuous experiments should also be investigated to minimise its effect. The investigation of activated alumina was only a secondary project and more work is required on optimisation, particularly for the desorption cycle to enable the recycling of the unreacted fluoride.
AFRIKAANSE OPSOMMING: Saamgestel in hierdie tesis is 'n studie van die beheer van kalsium en magnesium in 'n basismetaal-sulfaatoplossing, bevattende nikkel en kobalt. Die teenwoordigheid van kalsium en magnesium in dié oplossings veroorsaak 'n verskeidenheid van probleme, wat wissel van produkkwaliteit verlaging tot hoë energieverbruik en groot bloei strome tydens platering. 'n Groter probleem word ondervind met kalsium as gevolg van die lae oplosbaarheid van sy sulfaatsoute. Geen konvensionele metode kon gevind word vir die beheer van kalsium en magnesium gedurende die oorsig van moontlike metodes nie. Hierdie moontlike metodes is geïdentifiseer en kortliks bespreek in die tesis. Van die moontlike metodes is die presipitasie van fluoried-soute gekies vir verdere eksperimentele ondersoek. Die ondersoek het getoon dat dit moontlik is om kalsium en magnesium te beheer deur die presipitasie van fluoriede sonder om die basismetale saam te presipiteer. Vir 'n 10% oormaat fluoried toevoeging is 96.5% van die kalsium en 98.5% van die magnesium gepresipiteer gedurende die enkelladingstoetse. Dit is bekend dat vermenging en hidrodinamika 'n groot rol speel in die kwaliteit van die presipitaat wat gevorm word. Dit bemoeilik die opskalering van presipitasie prosesse. Vir die ondersoek oor die invloed van vermenging op 'n kontinu proses is die drie-sel model van Gösele en Kind (1991) gebruik. Dit is gevind dat die karakter van presipitaat relatief konstant gebly het vir variasies van vermenging op die makro, meso en mikro skaal, wat opskaling behoort te vergemaklik. Addisioneel is die verwydering of moontlike hersirkulasie van die ongereageerde fluoried ondersoek, en geaktiveerde alumina is geïdentifiseer as 'n moontlike adsorbeermiddel. 'n Eksperimentele ondersoek het getoon dat geaktiveerde alumina fluoried tot lae vlakke kan adsorbeer in die teenwoordigheid van die basismetale, waarna dit weer geregenereer kan word. Die kapasiteit van die geaktiveerde alumina (GA) was bereken as 8.65 gF/lGA by 'n 10 mg/l fluoried vlak gedurende die kolom toetse. 'n Konsep-proses is opgestel na aanleiding van die eksperimentele resultate, waarvolgens slegs 'n gedeelte van die logingstroom na die fluoried presipitasie proses gestuur word, waarna dit weer teruggevoeg word om die algehele kalsium en magnesium konsentrasie te verlaag. Dié metode sal voorkom dat magnesium presipitasie domineer vir 'n toepassing waar slegs 'n gedeelte van kalsium en magnesium verwyder word. Die fluoried presipitasie proses behels drie stappe waarvolgens die fluoriede eers gepresipiteer word, waarna dit geskei word, en dan die ongereageerde fluoried geadsorbeer word. Genoeg inligting is versamel sodat 'n kosteberaming van die proses gedoen kan word. As die koste van die proses aanvaarbaar is, word dit voorgestel dat die ondersoek voortgesit word. Verskillende reaktor konfigurasies kan vir die presipitasie stap getoets word en daar moet ook ondersoek ingestel word hoe om die korslaag wat gedurende die kontinu eksperimente geobserveer is, te verminder. Die ondersoek van geaktiveerde alumina was ondergeskik in die projek en nog werk sal gedoen moet word om dit te optimiseer, spesifiek gedurende die desorpsie siklus vir die hersirkulasie van die ongereageerde fluoried.

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Takahashi, Vivian Cristina Inacio. "Reciclagem de baterias de íon de Li: condicionamento físico e extração do Co." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-01042008-112312/.

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Com o avanço da tecnologia aplicada em aparelhos celulares, são lançados no mercado modelos menores, mais leves e com maior rapidez em seu sistema operacional. Tudo isso atrai muito os consumidores, que por sua vez, trocam seus antigos aparelhos celulares por novos e modernos. Essas adesões e trocas freqüentes de aparelhos celulares geram um descarte significativo de todos os seus componentes e dentre eles a bateria. Assim, pelo fato do cobalto estar presente nesse tipo bateria e ser um metal com alto valor agregado, ele faz parte do estudo do presente trabalho. Este trabalho tem por objetivos estudar as etapas de condicionamento físico e de lixiviação como fases iniciais do processo de reciclagem de baterias de íons de lítio. Para a caracterização das baterias, as mesmas foram desmanteladas manualmente para a separação dos componentes. Os eletrodos foram caracterizados por espectrofotometria de absorção atômica, difração de raios-X e microscopia eletrônica de varredura com analise de microrregiões. Os ensaios de lixiviação foram feitos usando-se os seguintes parâmetros: pH entre 3 e 5, temperaturas de 25 e 50ºC, relação sólido/líquido de 1/5, tempos de 1 a 4h. Foram utilizados como meio lixiviante soluções de acido sulfúrico, clorídrico e nítrico. Peróxido de hidrogênio foi adicionado ao acido sulfúrico como agente oxidante. Os resultados alcançados mostraram que entre os moinhos de martelos, de facas e de bolas o que apresentou o melhor desempenho para a moagem de baterias de íons de lítio foi o moinho de facas. O bombardeamento com ultra-som faz com que haja a liberação do material ativo dos eletrodos que fica aderido aos suportes de cobre e alumínio mesmo apos moagem. A diminuição do pH de 5 para 3 e o aumento da temperatura de 25 para 50ºC causam o aumento da velocidade de lixiviação em meio sulfúrico do oxido de cobalto. A presença de agente oxidante na lixiviação acida faz com que diminua o tempo de lixiviação do oxido de cobalto. A lixiviação com acido nítrico e com acido sulfúrico com adições de peróxido de hidrogênio são os melhores meios de lixiviação quando comparados ao acido clorídrico e ao acido sulfúrico sem oxidante para as mesmas condições de pH e de temperatura. Nas etapas de extração liquido-liquido e reextração foram utilizados os seguintes parâmetros: relação orgânico-aquoso de 1/1, temperatura de 50ºC, pH 4 e tempo de 5 minutos na etapa de extração e como solução aquosa na fase da reextração o acido sulfúrico 2M. Nas duas etapas foi utilizado como extratante o Cyanex 272 diluído em querosene. Os resultados alcançados mostraram que nos primeiros dois contatos das fases orgânicas e aquosas já se obtém as melhores porcentagens de extração e reextração. A eficiência global dos quatro contatos na etapa de extração foi de 94% e na etapa de reextracao foi de 98%.
The fast changes in technologies applied to mobile phones causes an incredible appearance of new and even better models each day. As a consequence, each year increase the amounts of waste of electronic and electric equipments including batteries that should be disposed of. The goal of the present work is to study methods of physical conditioning and acid leaching of Li-ion batteries. Hand disassembling Li-ion batteries was performed to identify and characterize the components of scrap Li-ion batteries. Materials extracted form the electrodes were characterized using X-ray diffraction, atomic absorption spectrophotometry and scanning electron microscopy coupled with EDS micro-probe. Leaching tests were carried out using the following parameters: pH (3 - 5), temperature (25 and 50ºC), solid/liquid ratio equal to 1/5, leaching time (1 to 4h). Sulfuric acid, chloridric acid and nitric acid were tested as leaching media. Hydrogen peroxide was tested as an oxidizing agent during leaching tests using sulfuric acid. The results obtained showed that knives mill presented better results to grind the scraps in comparison to hammer and balls mills. Ultrasonic treatment was effective to release the active cell materials from copper and aluminum. Decreasing pH from 5 to 3, and increasing the temperature from 25 to 50ºC cause the increasing of the leaching rate of cobalt oxide. Oxidizing conditions also increase the rate of cobalt oxide leaching. Nitric acid and sulfuric acid plus hydrogen peroxide leaching results in better leaching rates compared to chloridric acid and sulfuric acid.

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Okewole, Adeleye Ishola. "Application of bidentate N,N'-donor extractants in the hydrometallurgical separation of base metals from an acidic sulfate medium." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1002610.

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Bidentate imidazole-based extractants, 1-octylimidazole-2-aldoxime (OIMOX) and 1-octyl-2-(2′-pyridyl)imidazole (OPIM), along with dinonylnaphthalene sulfonic acid (DNNSA) as a synergist, were investigated as potential selective extractants for Cu²⁺and Ni²⁺ respectively from base metals in a solvent extraction system. The study was extended to evaluate the sorption and separation of Ni²⁺ from other base metals in a solid-solution system using microspherical Merrifield resins and nanofibers functionalized with 2,2′-pyridylimidazole. Copper was effectively separated with OIMOX and DNNSA as extractants from nickel with ΔpH½ ≈1.05 and the extraction order of Cu²⁺ > Ni²⁺ > Zn²⁺ > Cd²⁺> Co²⁺ was achieved as a function of pH. At pH 1.65 the extracted copper, from a synthetic mixture of the base metals reached 90.13(±0.90)%, and through a two-step extraction process 98.22(±0.29)% copper was recovered with negligible nickel and cobalt impurities. Stripping of the copper from the loaded organic phase using TraceSelect sulphuric acid at pH 0.35 yielded 96.60(±0.44)% of the loaded quantity after the second stage of stripping. The separation of Ni²⁺ from the borderline and hard acids; Co²⁺, Cu²⁺, Zn²⁺, Fe2²⁺, Fe²⁺, Mn²⁺, Mg2²⁺ and Ca²⁺ at a pH range of 0.5-3.5 with OPIM and DNNSA was acvieved to the tune of a ΔpH½≈ 1.6 with respect to cobalt from a sulfate and sulfate/chloride media. A three-stage counter-current extraction of Ni²⁺, at the optimized pH of 1.89, from a synthetic mixture of Ni²⁺, Co²⁺ and Cu²⁺, yielded 99.01(±1.79)%. The total co-extracted Cu²⁺ was 48.72(±0.24)% of the original quantity in the mixture, and it was 19.85(±0.28%) for Co²⁺. The co-extracted Cu²⁺ was scrubbed off from the loaded organic phase at pH≈8.5 by using an ammonium buffer, while co-extracted Co²⁺ was selectively and quantitatively stripped with H₂SO₄ at pH 1.64. The total recovery of Ni²⁺ by stripping at pH 0.32 was 94.05(±1.70)%. In the solid-liquid system, Ni²⁺ was separated from Co²⁺, Cu²⁺, and Fe²⁺ with the microspherical resins funtionalised with 2,2′-pyridylimidazole by a separation factor (β) in the range 22-45. Electrospun nanofibers as sorbents yielded high sorption capacity in the range of 0.97 - 1.45 mmol.g⁻¹ for the same metals ions. Thus, 1-octylimidazole-2-aldoxime (OIMOX), and1-octyl-2-(2′-pyridyl)imidazole (OPIM) can be effectively utilized alongside DNNSA as a co-extractant in the separation of Cu²⁺ and Ni²⁺ respectively from base metals in acidic sulfate medium in a solvent extraction process, and the latter as a selective ligand in the solid-liquid separation of Ni²⁺ from Co²⁺, Cu²⁺, and Fe²⁺.

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Chandra, Alind. "THERMODYNAMIC MODELING AND EQUILIBRIUM SYSTEM DESIGN OF A SOLVENT EXTRACTION PROCESS FOR DILUTE RARE EARTH SOLUTIONS." UKnowledge, 2019. https://uknowledge.uky.edu/mng_etds/53.

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Rare earth elements (REEs) are a group of 15 elements in the lanthanide series along with scandium and yttrium. They are often grouped together because of their similar chemical properties. As a result of their increased application in advanced technologies and electronics including electric vehicles, the demand of REEs and other critical elements has increased in recent decades and is expected to significantly grow over the next decade. As the majority of REEs are produced and utilized within the manufacturing industry in China, concerns over future supplies to support national defense technologies and associated manufacturing industries has generated interest in the recovery of REEs from alternate sources such as coal and recycling. A solvent extraction (SX) process and circuit was developed to concentrate REEs from dilute pregnant leach solutions containing low concentrations of REEs and high concentrations of contaminant ions. The separation processes used for concentrating REEs from leachates generated by conventional sources are not directly applicable to the PLS generated from coal-based sources due to their substantially different composition. Parametric effects associated with the SX process were evaluated and optimized using a model test solution produced based on the composition of typical pregnant leach solution (PLS) generated from the leaching of pre-combustion, bituminous coal-based sources. Di-2(ethylhexyl) phosphoric acid (DEHPA) was used as the extractant to selectively transfer the REEs in the PLS from the aqueous phase to the organic phase. The tests performed on the model PLS found that reduction of Fe3+ to Fe2+ prior to introduction to the SX process provided a four-fold improvement in the rejection of iron during the first loading stage in the SX circuit. The performances on the model system confirmed that the SX process was capable of recovering and concentrating the REEs from a dilute PLS source. Subsequently, the process and optimized parametric values were tested on a continuous basis in a pilot-scale facility using PLS generated from coal coarse refuse. The continuous SX system was comprised of a train of 10 conventional mixer settlers having a volume of 10 liters each. A rare earth oxide (REO) concentrate containing 94.5% by weight REO was generated using a two- stage (rougher and cleaner) solvent extraction process followed by oxalic acid precipitation. The laboratory evaluations using the model PLS revealed issues associated with a third phase formation. Tributyl Phosphate (TBP) is commonly used as a phase modifier in the organic phase to improve the phase separation characteristics and prevent the formation of a third phase. The current study found that the addition of TBP affected the equilibrium extraction behavior of REE as well as the contaminant elements., The effect on each metal was found to be different which resulted in a significant impact on the separation efficiency achieved between individual REEs as well as for REEs and the contaminant elements. The effect of TBP was studied using concentrations of 1% and 2% by volume in the organic phase. A Fourier Transform Infrared (FTIR) analysis on the mixture of TBP and DEHPA and experimental data quantifying the change in the extraction equilibrium for each element provided insight into their interaction and an explanation for the change in the extraction behavior of each metal. The characteristic peak of P-O-C from 1033 cm-1 in pure DEHPA to 1049 cm-1 in the 5%DEHPA-1%TBP mixture which indicated that the bond P-O got shorter suggesting that the addition of TBP resulted in the breaking of the dimeric structure of the DEHPA and formation of a TBP-DEHPA associated molecule with hydrogen bonding. The experimental work leading to a novel SX circuit to treat dilute PLS sources was primarily focused on the separation of REEs from contaminant elements to produce a high purity rare earth oxide mix product. The next step in the process was the production of individual REE concentrates. To identify the conditions needed to achieve this objective, a thermodynamic model was developed for the prediction of distribution coefficients associated with each lanthanide using a cation exchange extractant. The model utilized the initial conditions of the system to estimate the lanthanide complexation and the non-idealities in both aqueous and organic phases to calculate the distribution coefficients. The non-ideality associated with the ions in the aqueous phase was estimated using the Bromley activity coefficient model, whereas the non-ideality in the organic phase was computed as the ratio of the activity coefficient of the extractant molecule and the metal extractant molecule in the organic phase which was calculated as a function of the dimeric concentration of the free extractant in the organic phase. To validate the model, distribution coefficients were predicted and experimentally determined for a lanthanum chloride solution using DEHPA as the extractant. The correlation coefficient defining the agreement of the model predictions with the experimental data was 0.996, which is validated the accuracy of the model. As such, the developed model can be used to design solvent extraction processes for the separation of individual metals without having to generate a large amount of experimental data for distribution coefficients under different conditions.

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32

Kaya, Serif. "High Pressure Acid Leaching Of Turkish Laterites." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612896/index.pdf.

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ABSTRACT HIGH PRESSURE ACID LEACHING OF TURKISH LATERITES Kaya, Serif M.Sc., Department of Metallurgical and Materials Engineering Supervisor: Prof. Dr. Yavuz A. Topkaya January 2011, 91 pages The aim of this thesis study was to investigate and find the most cost effective way of extracting nickel and cobalt into the pregnant leach solution (PLS) from Gö
rdes lateritic nickel and cobalt ore by means of sulphuric acid leaching under high temperature and high pressure conditions.The high pressure acid leach (HPAL) experiments were conducted with nontronitic and limonitic types of Gö
rdes lateritic nickel ore, respectively. Leaching experiments of nontronite ore have shown that almost all of the nickel and cobalt contained in the nontronitic ore were easily extracted into the (PLS). Therefore, the rest of the experiments were concentrated on difficult to leach limonitic sample when compared with the nontronitic one, and higher nickel and cobalt extractions were aimed to be obtained. By taking economic and technical considerations into account, the basic (HPAL) process parameters for the limonitic sample were optimized as
leaching at 255 °
C with a particle size of 100% -850 &mu
with 0.30 sulphuric acid to ore weight ratio in 1 hour of leaching duration. The experiments were conducted with 30% solids ratio and it was found that 87.3% of nickel and 88.8% of cobalt present in the limonitic ore could be extracted into the pregnant leach solution. Nevertheless, these results were found to be below the desired values. Therefore, the possible reasons of this behavior were investigated and the presence of hematite mineral in the limonitic ore was found to be the most probable one. Therefore, in order to dissolve the nickel and cobalt present in the hematite mineral, the additions of HCl, ferrous ions, cuprous ions and sulphur were tried, respectively and they were found to be beneficial in order to increase the degree of nickel and cobalt extractions.

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Moraes, Viviane Tavares de. "Recuperação de metais a partir do processamento mecânico e hidrometalúrgico de placas de circuito impresso de celulares obsoletos." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-19042011-100037/.

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O avanço da tecnologia de aparelhos eletro-eletrônicos favorece a troca constante dos equipamentos. O freqüente descarte de aparelhos obsoletos se torna um problema de sustentabilidade e também um problema ambiental devido ao seu acúmulo em aterros. A solução para minimizar estes impactos é a reciclagem de seus componentes. Por esta razão, o principal objetivo deste trabalho é estudar o processamento das placas de circuito impresso de telefones celulares através de operações unitárias de Tratamento de Minérios e hidrometalurgia a fim de se recuperar o cobre contido nas placas. Para isso, inicialmente, placas de circuito impresso foram processadas em moinho de martelos, a fim de liberar os materiais, em seguida foi feita a separação magnética do material cominuído. Com a fração não magnética foi feita a separação eletrostática e o material foi separado em: fração condutora, mista e não condutora, com cada fração foi feita a classificação granulométrica e, posteriormente, realizaram-se ensaios de caracterização como pirólise, digestão em água régia e análise química de espectroscopia de emissão óptica por indução de plasma. Os processos hidrometalúrgico aplicados para a recuperação de cobre nas placas de circuito impresso de aparelhos celulares obsoletos envolvem etapas lixiviação com ácido sulfúrico na ausência e na presença de peróxido de hidrogênio. Os resultados da caracterização mostraram que as placas de circuito impresso de celulares após a moagem possuem 24% de cerâmicas; 12,7% de polímeros e 63,3% de metais. Além disso, após a classificação granulométrica e a separação eletrostática os materiais não se concentraram em nenhuma fração especifica, portanto o processamento mecânico visando a recuperação de metais deve contemplar a moagem e a separação magnética.
The technology advancement of electro-electronics devices favors the constant equipment exchange. The frequent disposal of obsolete equipment becomes a sustainability problem and also an environmental problem due to their accumulation in landfills. One possible solution to minimize these impacts is the recycling of their components. For this reason the aim goal of this study is processing of printed circuit boards of mobile phones utilizing unit operation of ore treatment and hydrometallurgy to recover the copper contained in the printed. Therefore, initially printed circuit boards were processed on a hammer mill to release the materials, then it was made magnetic separation of comminuted material. With the non-magnetic fraction was made electrostatic separation in which the material was separated into: conductive, mixed and non-conductive fraction, with each fraction was made grain sized classification and then assays were performed analysis of characterize as pyrolysis, digestion in aqua regia and chemical analysis of inductively coupled plasma atomic emission spectroscopy. Hydrometallurgical processes applied to the cooper recovery in printed circuit boards of obsolete mobile phones, involve steps leaching with sulfuric acid in the absence and presence of hydrogen peroxide. The characterization results showed that the printed circuit boards of mobile phones after grinding have ceramics 24%, polymers 12.7% and metals 63.3%. Moreover, after grain sized classification and electrostatic separation the materials didn\'t concentrate in no specific fraction, therefore the mechanical processing in order to recover metals should include grinding and magnetic separation.

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Santanilla, Adriana Johanny Murcia. "Recuperação de níquel a partir do licor de lixiviação de placas de circuito impresso de telefones celulares." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-20032012-155039/.

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Os resíduos de equipamentos elétricos e eletrônicos é um dos fluxos de resíduos que mais cresce no mundo. O aumento na produção destes equipamentos como resultado dos avanços tecnológicos e a sua rápida obsolescência promovem o aumento de geração deste tipo de resíduos. Portanto, este trabalho tem como objetivo estudar a recuperação de níquel presente no licor de lixiviação de placas de circuito impresso de telefones celulares obsoletos, através da aplicação de processos hidrometalúrgicos e eletrometalúrgico. Inicialmente, foram preparadas soluções sintéticas a partir da composição química do licor de lixiviação das frações magnética (MA) e não magnética (NMA) das placas de circuito impresso cominuídas. Os elementos presentes nas soluções são: ferro, zinco, níquel e alumínio. Posteriormente, foi realizada uma etapa de remoção do ferro, através de precipitação seletiva. A morfologia e a composição química do precipitado foram analisadas através de Microscopia Eletrônica de Varredura (MEV) e EDS, respectivamente. A composição química das soluções resultantes da precipitação foi determinada através da técnica de espectrofotometria de absorção atômica. Através do processo de precipitação conseguiu-se uma porcentagem de remoção de ferro na solução NMA de 99,6% e na solução MA de 99,9%, porém, observou-se também a coprecipitação de zinco, alumínio e níquel. Com as soluções resultantes desta etapa, foi realizada a purificação das soluções através de extração por solvente, utilizando Cyanex 272 como agente extratante. As variáveis estudadas nos ensaios de extração por solvente foram: pH, concentração do extratante, relação fase aquosa/orgânica (A/O) e temperatura. . Além disso, também foi determinado o número de contatos necessários para a extração de ferro, zinco e alumínio, obtendo assim, uma solução aquosa contendo unicamente níquel. Finalmente, foram realizados os ensaios de eletrodeposição para a obtenção de níquel metálico. Foi avaliado o efeito da temperatura sobre o filme depositado. A morfologia dos depósitos e a espessura da camada foram analisadas através do MEV, verificando que o aumento da temperatura influencia nas características do depósito obtido.
Electric and electronic waste (e-waste) is one of the fastest growing waste streams in the world. Continuous increasing production owing to the technological advances and the products consumption rise, all together with the rapid obsolescence of this scrap promotes the necessity of exchange and the increasing of generate waste. Therefore, the aim of this work is to study a recovering of nickel from leach liquor of cell phones printed circuit boards, through of hydrometallurgical and electrometallurgical process application. Firstly, was prepared synthetic solutions of both magnetic (MA) and nonmagnetic (NMA) fractions of printed circuit boards. The metal ions present in the synthetic solutions are: iron, zinc, nickel and aluminium. Afterwards was realized the iron removal stage, through both selective precipitation and solvent extraction process, in order to make a comparison of these techniques. The precipitates were analyzed across of scanning electron microscope (SEM), and the chemical composition of these solutions through atomic absorption spectrometry (AAS). With selective precipitation it was obtained 99,6% and 99,9% of iron removal with selective precipitation in NMA and MA solutions, respectively. Therefore, it was also observed co-precipitation of zinc, aluminium and nickel. With solutions after precipitation stage was carried out the solutions purification through solvent extraction using cyanex 272 as extractant. Solvent extraction test were studied different parameters, such as: equilibrium pH, extractant concentration, aqueous-organic (A/O) ratio and temperature. It was also determinates the stages number required for iron, zinc and aluminium extraction, to obtain nickel in aqueous solution uniquely. Finally, was carried out the electrodeposition test for obtain metallic nickel. Was analyzed the effect of temperature on the deposited layer. Surface Morphology and thickness of the deposits were evaluated by MEV, verifying that temperature increasing influences on deposited layer.

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Ricknell, Jonas. "Recovery of valuable metals from spent HEV NiMH battery leach solutions." Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-216397.

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As the demand on resources is increasing worldwide, the process of recycling material has become more important. The specific recycling of metals used in car batteries, and more specifically in the large batteries used in hybrid electric vehicles, is a rising concern where the industrially implemented recycling processes concerning these batteries that exist today are often highly pollutant and energy consuming. In the present study, an alternative hydrometallurgical recycling process of the previously and to some extent presently widely used battery type for hybrid electric vehicle applications, namely the Nickel Metal Hydride (NiMH) battery, has been investigated. The focus was to evaluate different routes of recovering Ni, Co, Mn, Zn, Al and residual Y from a NiMH battery leach solution as obtained in a priorly conducted leaching study. Three different possible products were chosen for closer investigation, a mixed metal hydroxide where all of the metals would be precipitated together, a new NiMH cathode material where a controlled precipitation of Ni, Co and Zn together would be implemented and last a pure Ni salt product where a selective separation of Ni from the other metals would be required. Two of the three products, the mixed metal hydroxide and the pure Ni salt, were found suitable for the specific system and it was concluded that a pure Ni salt production would be most justifiable. The separation of Ni from the other metals present in the solution was here proposedly achieved by an extraction process using supported liquid membranes. A mathematical model was used in Matlab in order to evaluate the separation efficiency and to determine the optimum process conditions for the extraction process and a hydroxide precipitation experimental study was conducted in order to determine both the process streams in the production of a mixed metal hydroxide and the solution behavior during the pH increase in the Ni salt production extraction process. The results suggested a low loss of valuable metals and due to this, both the process of producing a mixed metal hydroxide and the process of producing a pure Ni salt could be found to be economically justifiable.
I samband med den ökande efterfrågan på råmaterial världen över så har processer för att återvinna material blivit mer och mer viktiga. Den specifika återvinningen av metaller som använts i bilbatterier, och än mer specifikt återvinningen av de stora batterier som används i hybridbilar är just nu en ökande oro då de rådande återvinningsprocesser som används idag ofta är högst energikrävande och har en stor förorenande inverkan på naturen. I denna studie har en alternativ hydrometallurgisk återvinningsprocess granskats i syfte att återvinna de metaller som används i nickelmetallhydridbatterier (NiMH) som brett har använts för just hybridbilsapplikationer. Fokus har legat på att utvärdera olika möjligheter att återvinna Ni, Co, Mn, Zn, Al och överbliven Y från en laklösning som är ett resultat av en tidigare genomförd lakstudie angående NiMH-batterierna. Tre möjliga produkter valdes för närmare granskning, en blandad metallhydroxid där alla metaller samutfälls ur lösningen, en ny NiMH-katod där en kontrollerad samutfällning av Ni, Co och Zn implementeras och sist ett rent nickelsalt där a selektiv separation av Ni från de övriga metallerna är nödvändig. Två av de tre produkterna, den blandade metallhydroxiden och det rena nickelsaltet, befanns vara lämpliga för det specifika systemet och slutsatsen drogs att en nickelsaltsproduktion var mest berättigad. Den föreslagna separationstekniken för att separera Ni från de andra metallerna i lösningen var en extraktionsprocess användandes av en vätskemembranteknik. En matematisk modell användes med hjälp av Matlab för att utvärdera separationseffektiviteten och för att bestämma optimala processförhållanden. En experimentell hydroxidutfällningsstudie genomfördes även för att bestämma både procesströmmarna i en produktion av en blandad metallhydroxid och för att undersöka lösningens beteende under pH-ökningen i den föreslagna produktionsprocessen av ett nickelsalt. Enligt resultaten är förlusten av värdefulla metaller låga i båda processerna och i enlighet med detta kunde både produktionsprocessen av en blandad metallhydroxid och av ett rent nickelsalt befinnas ekonomiskt hållbara.

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36

Lorenzen, Leon. "A fundamental study of the dissolution of gold from refractory ores." Thesis, Stellenbosch : Stellenbosch University, 1992. http://hdl.handle.net/10019.1/69492.

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Thesis (PhD)--Stellenbosch University, 1992.
ENGLISH ABSTRACT: The dissolution of gold from refractory ores is a complex kinetic problem involving a number of chemical, mass transport and mineralogical factors. In most Witwatersrand ores in South Africa more than 97 % of the gold is dissolved in cyanide medium after a residence time of about 16 hours in pachuca tanks. This high percentage may be the reason why so little fundamental research has been done into the mechanism and kinetics of the leaching process. With the increasingly lower grades of ore mined, the introduction of backfill mining, and the reduction of profit margins, it has become imperative to increase the efficiency of gold dissolution. The effects of the chemistry and particle size on the dissolution of gold in each sample of ore were studied in detail. The emphasis in this study is on the effect of the leaching behaviour of various ore constituents on the rate of gold dissolution. Interferences with the leaching of gold in contact with other minerals or metals could be attributed to the galvanic interaction (electrical conductivity) between the gold and the mineral and to the formation of a surface film on the gold surface. Sulphide minerals and their oxidation products cause the largest decrease in gold dissolution rate. Galena enhances the rate of gold dissolution owing to dissolved Pb(II)-ions. Gold in contact with conductive minerals passivates as a result of the enhanced magnitude of the cathodic cu1Tent. In all experiments the rotating disc of gold passivated so that the rate of dissolution was much slower than that predicted by a mass-transport limiting model. The various films that form on the surface of the gold and associated minerals, as well as the galvanic interaction, depend largely on the pretreatment of the ore. Pre-elimination of host minerals from the gold bearing ore increases the dissolution rate of gold, and explains the kinetics of reaction on the gold surface to a large extent. The selective destruction of the various minerals with oxidative acid leaches destroys and/or decomposes certain minerals which may form films on the gold surface by precipitation. The chemical composition of these films and precipitates depends on the mineralogy of the sample. These films may be oxides, sulphides, carbonates and cyanide complexes. The complexes can be destroyed, depending on the nature of the film, by interstage dilute acid and/or cyanide washes in an agitated vessel. The destruction of the films exposes the gold surface for cyanidation. A simple distribution function similar to the King liberation model is proposed and tested to describe the dissolution step in the multi-step leaching mechanism. For the King model, good agreement is shown with experimental results. For the liberation results obtained by leaching in this study, the trend is co1Tect, but calibration is required for a close fit. A potentially important use for the liberation model by leaching is to predict the leachable or free gold in an ore from the free gold in the complete sample. This approach for studying the leaching behaviour of different gold bearing minerals has provided reasons why some ores leach better than others.
AFRIKAANSE OPSOMMING: Die loging van goud vanuit weerbarstige ertse is 'n komplekse kinetiese probleem wat verskeie faktore soos massa-oordrag, chemiese aspekte en mineralogiese ingeweefdheid insluit. Goud ekstraksies so hoog as 97 % in sianied oplossings in Pachuca reaktore na ongeveer 16 uur logingstyd word behaal in die meeste Witwatersrand ertse in Suid-Afrika. Hierdie hoë ekstraksies mag dalk die rede wees vir die min fundamentele navorsing oor die ekstraksie van goud vanuit minerale in 'n spesifieke erts. Die dalende erts grade, die verlaging van winsgrense en die terugplaas van geloogde erts in die myn noodsaak verbeterde goud ekstraksie. Verkeie faktore nl., chemie, diffusie, partikelgrootte en oplosbaarheid van goud in elke monster erts is in hierdie studie ondersoek. Die sentrale tema was om die logingsgedrag van goud vanuit verskeie minerale in 'n erts te bepaal. Galvaniese interaksie (hou verband met elektriese geleidingsvermoeë) en film vorming is die belangrikste faktore wat die loging van goud in kontak met minerale nadelig beïnvloed. Sulfied minerale en hul oksidasie produkte speel die grootste rol in die verlaging van die tempo van goudloging. Galena verhoog die tempo van goudloging as gevolg van die Pb (II)- ione in oplossing. Goud in kontak met geleidende minerale passiveer as gevolg van die verhoogde katodiese stroomdigtheid. In alle eksperimente met die roterende skyf (goudskyf) apparaat, passiveer die goudskyf in so 'n mate dat die logingstempo baie stadiger is as wat voorspel word met die massa-oordrags model. Die onderskeie films wat vorm op die goud- en geassosieerde minerale se oppervlaktes, asook die galvaniese interaksies, is 'n funksie van die voorafbehandeling van die erts. Die selektiewe eliminering van minerale vanuit 'n gouddraende erts verhoog die tempo van goudloging drasties en dit beskryf die kinetika van goudloging op die goudoppervlak in 'n groot mate. Die selektiewe eliminering van minerale deur gebruik te maak van oksiderende suurlogings, vernietig sekere van die minerale wat films op die goudoppervlakte kan veroorsaak deur middel van presipitasie. Die chemiese samestelling van hierdie films hang af van die mineralogie van die monster. Dit bestaan meestal uit oksiedes, sulfiedes, karbonate en sianiedkomplekse en hulle kan vernietig word deur middel van inter-stadia verdunde suur-en/of sianied wasse. 'n Eenvoudige distribusiefunksie, soortgelyk aan die King bevrydingsmodel word voorgestel en eksperimenteel getoets om die logingstap in die multi-stadia logingsmeganisme te beskryf. Vir bevryding deur loging, is die neiging van King se model korrek, maar kalibrasie word benodig vir goeie passing. 'n Potensiele gebruik van die aangepaste model is om vrye of loogbare goud in 'n spesi fieke partikel grootte fraksie van 'n erts te voorspel as die vry goud in die totale fraksie bekend is. Die resultate uit hierdie studie kan gebruik word om die logingsgedrag van gouddraende minerale te voorspel en te beskryf, en dus veduidelik hoekom goud uit sekere ertse beter loog as uit ander.

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37

Afonso, Larissa Cardillo. "Biolixiviação de cobre a partir de rejeito de processo de flotação de calcopirita empregando consórcio de microrganismos." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-15012018-153426/.

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Biolixiviação é um processo econômico para a recuperação de metais que exige baixo custo de investimento e operação. Além disso, é geralmente mais ambientalmente amigável do que muitos processos físico-químicos de extração de metal. O presente trabalho visou a extração de cobre a partir de rejeito da etapa Scavenger (SCV) de circuito de flotação de calcopirita. Foram realizados ensaios de biolixiviação utilizando o rejeito SCV, que contém em torno de 0,73% de cobre, e um consórcio de microrganismos denominado ABL, selecionado a partir de amostras coletadas na Mina do Sossego. Um tratamento ácido do rejeito foi realizado prévio à biolixiviação para redução de carbonatos. Os ensaios em frascos agitados foram realizados variando-se parâmetros como agitação, densidade de polpa, tamanho de partícula e pH. Os resultados mostraram extração de cobre de 70% para a biolixiviação de rejeito Finos Tratado (100% das partículas com tamanho inferior a 0,045 mm) nas seguintes condições: densidade de polpa de 40% (m/v), agitação de 130 rpm e temperatura 35°C. Ensaios em biorreator tipo batelada com rejeito SCV Tratado (82% das partículas com tamanho inferior a 0,045 mm) alcançaram extração de 59% de cobre, resultado parecido ao observado para a biolixiviação de rejeito SCV Tratado em frascos agitados, 55%. Os resultados de extração de cobre encontrados nesse trabalho estão entre os maiores reportados na literatura de biolixiviação de cobre de rejeitos.
Bioleaching is an economical process for metal recovery that requires low investment and operational costs. Furthermore, it is in general more eco-friendly than many other physicochemical metal extraction processes. The present work aimed at the extraction of copper from scavenger tailing (SCV) of chalcopyrite flotation circuit. Bioleaching tests were carried out using the SCV tailing, which contains around 0.73% of copper, and a microbial consortium called ABL, selected from samples collected at Sossego Mine. An acid treatment of tailings was carried out, prior to bioleaching, to reduce carbonates, which consume acid during the bioleaching. Shake flasks tests were performed by varying parameters such as agitation, pulp density, particle size and pH. The results showed 70% copper extraction for the bioleaching of Treated Fine Particles (100% of the particles being smaller than 0.045 mm) under the following conditions: pulp density of 40% (w/v), agitation of 130 rpm and temperature of 35°C. Batch reactor tests with Treated SCV (82% of particles smaller than 0.045 mm) reached a 59% copper extraction, a result similar to that reached through the bioleaching of Treated SCV in shake flasks, 55%. The copper extraction results found in this work are among the highest ones reported on bioleaching of copper from tailings.

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38

München, Daniel Dotto. "Recuperação de neodímio a partir de ímãs de neodímio-ferro-boro por meio de processos mecânicos e hidrometalúrgicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/149837.

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O elemento químico neodímio (Nd) atualmente está em evidência pois é parte fundamental em aplicações produzidas por empresas ligadas a tecnologias limpas e de ponta. Porém, é classificado como crítico pelo departamento de energia dos EUA em função do monopólio chinês atuante em sua exploração e comercialização. Devido à crescente demanda frente à restrita disponibilidade, a recuperação deste metal está em ascensão. Uma das aplicações do neodímio é o ímã permanente de neodímio-ferro-boro, utilizado em hard disk drives (HDs) de computadores. Desta forma, este estudo visou caracterizar os ímãs provenientes de HDs de computadores e estabelecer uma rota de recuperação do neodímio por meio de processos mecânicos e hidrometalúrgicos. Por meio da pesagem dos HDs e seus ímãs obteve-se massa média de 3,04 g e 7,91 g para laptop e desktop, respectivamente, representando menos de 3% da massa total do HD. A desmagnetização foi atingida por meio de aquecimento até a temperatura de Curie, em torno de 312 °C, e a cominuição realizada em moinho de facas, onde foram obtidas três granulometrias classificadas em frações A, B e C. Qualitativamente as amostras, foram analisados por meio de difração de raios-X (DRX), onde a fase tetragonal Nd2Fe14B foi o constituinte dominante, e por meio de análise em microscópio eletrônico de varredura (MEV). Semi-quantitativamente os ímãs, seus revestimentos e o precipitado final foram avaliados por meio de espectrometria de fluorescência de raios-X (FRX). A composição média de 21,5% de neodímio e 65,1% de ferro em massa, além de outros elementos químicos, obtida por meio de espectrometria de emissão óptica com plasma (ICP-OES), mostrou teor de neodímio superior aos minérios explorados, tornando este resíduo interessante em relação à recuperação deste metal. O procedimento hidrometalúrgico adotado envolveu a lixiviação das amostras em ácido sulfúrico 2M e a variação de três parâmetros: razão sólido/líquido, temperatura e tempo, em dois níveis. Posteriormente foi realizada a precipitação seletiva por meio de NaOH, formando o duplo sal NaNd(SO4)2.nH2O. Os resultados mostraram que a lixiviação de neodímio atingiu eficiência média acima de 94%, porém todos os experimentos apresentaram material não lixiviado, majoritariamente composto por níquel e cobre.
The chemical element neodymium (Nd) currently is in evidence as it is a fundamental part in applications manufactured by clean and advanced technology companies. However, it is classified as critical by the United States Department of Energy due to Chinese monopoly in its exploration and commercialization. Due to increasing demand in contrast with scarce supply, the recovery of neodymium is growing. One of the applications of this metal is the neodymium-iron-boron permanent magnet, used in hard disk drives (HDDs) of computers. Therefore, this study aimed magnets characterizing from HDDs of computers and then establishing a recovery route for neodymium by mechanical and hydrometallurgical processes. By weighing the HDDs and their magnets it was obtained the average weight of 3.04 g and 7.91 g for laptop and desktop, respectively, representing less than 3% of the HDDs total mass. Demagnetizing was achieved by heating up to Curie temperature of around 312 °C, and the comminution in knives mill resulted in three granulometries classified into fractions A, B and C. Qualitatively, magnets were analyzed by X-ray diffraction (XRD), where the tetragonal phase Nd2Fe14B was the dominant constituent of the sample, and through analysis in a scanning electron microscope (SEM). Semi-quantitatively, the magnets, its covers, and the final precipitate were evaluated by X-ray fluorescence spectrometry (XRF). The average composition of neodymium and iron showed 21.5% and 65.1% by weight, respectively, among other chemical elements. This results were obtained by optical emission spectrometry (ICP-OES), representing a higher neodymium content compared to the ores content, which makes this waste interesting from a neodymium recovery point of view. The procedure adopted involved hydrometallurgical leaching of the samples in 2M sulfuric acid varying three parameters: liquid/solid ratio, temperature and time, each one on two levels. Subsequently, the selective precipitation by NaOH was performed to form the double salt NaNd(SO4)2.nH2O. The results showed that neodymium leaching efficiency reached above 94%, but the experiments showed as well some material left, mainly composed of nickel and copper.

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39

Manfoumbi, Christian. "Précipitation des gels de silice en solution aqueuse sursaturée à forte acidité : mécanismes et mésostructures, application à la filtrabilité des pulpes dans les procédés hydrométallurgiques." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30251/document.

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La formation de gels de silice dans les procédés hydrométallurgiques est très souvent problématique pour la performance des étapes de séparation solide-liquide, en raison du colmatage des filtres. Ces étapes interviennent en aval des étapes de lixiviation visant à mettre en solution les éléments d'intérêts, notamment dans des milieux à forte acidité. Egalement mis en solution au cours de ces attaques acides, le silicium précipite alors sous forme d'oxyde de silicium et forme des gels extrêmement préjudiciables à la filtration. Dans le cadre d'une collaboration avec ERAMET Research, centre de recherche d'ERAMET, groupe minier français qui conçoit des procédés hydrométallurgiques, nous avons étudié l'influence des conditions de lixiviation d'un minerai spécifique sur la cinétique de dissolution du silicium ainsi que sur les mécanismes de précipitation de la silice en milieu acide. Nous avons montré qu'en-dessous d'une valeur de pH égale à 2, la silice polymérise pour former des gels suivant des mécanismes indépendants de la composition ionique de la solution. L'étude structurale des gels obtenus, réalisée par diffusion de rayonnement aux petits angles (SAXS) nous a conduit à proposer un modèle pour la mésostructure qui permet de comprendre leur impact sur les vitesses de filtration. Par la suite, des stratégies consistant à modifier la mésostructure des gels par des approches physiques ou physico-chimiques ont été considérées. Les résultats obtenus ont montré la possibilité d'utiliser à court terme ces stratégies pour améliorer la filtrabilité des gels de silice dans un procédé hydrométallurgique
The formation of silica gels in hydrometallurgical processes is very often problematic for the performance of the solid-liquid separation steps, due to clogging of the filters. These steps are carried out downstream of leaching aiming to solubilize the elements of interests, in particular in solutions with strong acidity. Also dissolved during acidic leaching, the silicon then precipitates in the form of silicon oxide and forms gels extremely detrimental to filtration. In collaboration with ERAMET Research, a research center of ERAMET, a french mining group that designs hydrometallurgical processes, we studied the influence of the leaching conditions of a specific ore on the dissolution kinetics of silicon as well as on the mechanisms of precipitation of silica in an acidic solution. We have shown that below a pH value of 2, silica polymerizes to form gels following mechanisms independent of the ionic composition of the solution. Based, on the structural study of the gels, carried out by small angle radiation scattering (SAXS) we proposed a model for the mesotructure, which explain the impact on filtration rates. Subsequently, strategies to modify the mesostructure of the gels by physical or physicochemical approaches were considered. The results have shown the potentialities of these strategies in the short term to improve the filterability of precipitated silica gels in a hydrométallurgical process

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40

Alberts, Estelle. "Stripping rare earth elements and iron from D2EHPA during zinc solvent extraction." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17999.

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Thesis (MScEng)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: At Skorpion Zinc mine, in south-west Namibia, zinc oxide ore is refined through sulphuric acid leaching, solvent extraction, electrowinning and casting of the final 99.995 % Zn metal. Over the last four years, the rare earth element concentrations, with particular reference to Y, Yb, Er and Sc, have significantly increased in the circulating electrolyte and the zinc-stripped organic phase streams in the electrowinning and solvent extraction processes. This project had two main objectives: firstly, the effect(s) of rare earths on the zinc solvent extraction and electrowinning processes were to be determined; based on these results, the second objective was to find a suitable method for removing rare earth elements from the organic phase during zinc solvent extraction. The investigation into the effect of the rare earths on zinc electrowinning showed that an increase of 100 mg/l in the electrolyte Y concentration caused a decrease of 6 % in current efficiency. The elemental order of decreasing current efficiency was found to be: Y > Yb > Er > Sc. In the zinc solvent extraction process, it was found that an increase in the total organic rare earth elements and iron concentration from 3100 to 6250 mg/l resulted in doubled viscosity and an increase in phase disengagement time from 100 to 700 seconds. The organic zinc loading capacity after two extraction stages was reduced by 1 – 3 g/l depending on the pregnant leach solution used. The detrimental effect of rare earth elements on solvent extraction and electroplating of zinc therefore justified the development of a rare earth element removal process. Stripping of low concentrations of rare earth elements from 40% D2EHPA diluted in kerosene to produce a clean organic for zinc extraction was investigated using bench-scale experiments in a glass jacketed mixing cylinder. For the rare earths, the best stripping agent was found to be H2SO4, followed by HCl and then HNO3. Hydrochloric acid achieved better Fe stripping than sulphuric acid. Acid concentration was tested in the range of 1 to 7 M, organic-to-aqueous ratio for the range of 0.25 to 6.0 and temperatures between 30 and 55 °C. More than 80% stripping of yttrium and erbium could be achieved at an optimum hydrochloric acid concentration of 5 M and more than 90% rare earth element (specifically Y, Er, Yb) stripping from the organic phase could be achieved with 5 M sulphuric acid. Stripping was improved by reducing the organic-to-aqueous ratio to as low as 0.5 and increasing the temperature. Stripping increased with increasing temperature in an S-shaped curve, flattening off at 50°C. The effect of O:A ratio was more significant than the effect of temperature on rare earth stripping. The results showed good repeatability, and were not limited by the rare earth concentration, agitation rate or equilibrium time in the range of set points used in the experiments. Statistical models were compiled to fit the experimental data obtained for Y, Yb, Er and Fe when stripped with sulphuric and hydrochloric acid respectively. All models showed dependence on the acid concentration and squared-concentration and interaction effects between the O:A ratio and temperature and stripping agent concentration were significant. The models were compiled for the experimental data obtained from stripping synthetically prepared organic and then tested on results obtained when stripping the plant organic phase. The following three process solutions were discussed for implementation on a plant scale for the removal of rare earths from the organic phase during zinc solvent extraction: Sulphuric acid stripping mixer settler or stripping column, improvement of available HCl stripping section and replacement of the organic inventory. The possibility of an oxalic acid precipitation process to obtain value from the rare earths as by-product was also discussed. It was concluded that the current process that uses HCl to strip off iron and rare earths would be the best practically and financially feasible process. Value can be gained from the rare earths if a rare earth element - oxalic acid precipitation section that is financially feasible can be established.
AFRIKAANSE OPSOMMING: By Skorpion Zinc myn, in suidwes Namibië, word sinkoksied erts gesuiwer deur middel van swaelsuur-loging, oplosmiddel ekstraksie, elektroplatering en gieting van die finale 99.995 % Zn metaal. Oor die afgelope vier jaar het die seldsame aardmetale konsentrasie, spesifiek Y, Yb, Er en Sc, noemenswaardig in die sirkulerende elektroliet en sink-gestroopte organiese fase toegeneem. Hierdie projek het twee hoofdoelstellings gehad: eerstens moes die effek van seldsame aardmetale op die sink oplosmiddel ekstraksie en elektroplatering prosesse bepaal word; gebaseer op hierdie resultate, was die tweede doelstelling om ‘n geskikte metode vir die verwydering van seldsame aardmetale vanaf die organiese fase gedurende sink oplosmiddel ekstraksie te vind. Die ondersoek na die effek van seldsame aardmetale op sink elektroplatering het gewys dat ‘n verhoging van 100 mg/l in die elektroliet Y konsentrasie ‘n verlaging van 6 % in kragdoeltreffendheid veroorsaak het. Die element-orde van verminderende kragdoeltreffendheid was Y > Yb > Er > Sc. Vir die sink oplosmiddel ekstraksie proses, is gevind dat ‘n verhoging in die totale organiese seldsame aardmetaal- en yster konsentrasie van 3100 tot 6250 mg/l ‘n verdubbelde viskositeit en ‘n verlenging in faseskeidingstyd van 100 tot 700 sekondes tot gevolg gehad het. Die organiese sink ladingskapasiteit na twee ekstraksie stappe is met 1 – 3 g/l verminder afhangende van die logings oplossing wat gebruik is. Die nadelige effek van seldsame aardmetale op oplosmiddel ekstraksie en sink elektroplatering het die ontwikkeling van ‘n seldsame aardmetale verwyderingsproses regverdig. Die verwydering van lae konsentrasies seldsame aardmetale vanaf die D2EHPA-keroseen organiese fase om ‘n skoon organiese fase vir sink-ekstraksie te verkry is ondersoek deur banktoetsskaal eksperimente. Vir die seldsame aardmetale is bevind dat H2SO4 die beste stropingsagent is, gevolg deur HCl en dan HNO3. Soutsuur het beter yster verwydering as swaelsuur bewerkstellig. Suurkonsentrasies van 1 tot 7 M, O:A verhoudings van 0.25 tot 6 en temperature tussen 30 en 55°C is getoets. Meer as 80% verwydering van yttrium en erbium kon bereik word met ‘n optimum HCl konsentrasie van 5 M en meer as 90% seldsame aardmetale (spesifiek Y, Er en Yb) verwydering vanaf die organiese fase met 5 M swaelsuur. Seldsame aardmetale en yster verwydering kon verbeter word deur die organies-tot-waterfase (O:A) verhouding te verminder tot so laag as 0.5 en deur die temperatuur te verhoog. Stroping het in ‘n S-kurwe verhoog soos die temperatuur verhoog het, en het afgeplat teen 50°C. Die effek van die O:A verhouding was belangriker as die effek van temperatuur op stroping. Die resultate het goeie herhaalbaarheid gewys, en is nie deur massaoordrag beperk nie. Statistiese modelle is saamgestel om die eksperimentele data wat vir Y, Yb, Er en Fe verkry is vir stroping met swaelsuur en soutsuur te pas. Al die modelle het afhanklikheid van die suurkonsentrasie en kwadratiese suurkonsentrasie gewys en interaksie effekte tussen die O:A verhouding, temperatuur en suurkonsentrasie was belangrik. Die modelle is saamgestel vir die eksperimentele data wat verkry is vanaf stroping van ‘n sintetiese organiese fase en is toe getoets op resultate wat verkry is vanaf stroping van die aanleg se organiese fase. Die volgende drie proses-oplossings is oorweeg vir implementering op ‘n aanlegskaal vir die verwydering van seldsame aardmetale vanaf die organiese fase gedurende sink oplosmiddel ekstraksie: Swaelsuur stroping menger-afskeidingstenk of stropingskolom, verbetering van die bestaande HCl aanleg en vervanging van die organiese inventaris. ‘n Moontlike oksaalsuur presipitasie proses om waarde vanaf die seldsame aardmetale as by-produk te verkry is ook bespreek. Daar is tot die gevolgtrekking gekom dat die huidige proses wat HCl gebruik om yster en seldsame aardmetale van die organiese fase af te stroop, die beste praktiese en finansieel vatbare proses huidiglik is. Waarde kan vanaf die seldsame aardmetale verkry word as ‘n seldsame aardmetale – oksaalsuur presipitasie afdeling wat finansieel haalbaar is daargestel kan word.

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Doidge, Euan Douglas. "Designing reagents for the solvent extraction of critical metal resources." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31070.

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The work in this thesis aims to develop new systems for the more efficient recovery of metals from aqueous solution using solvent extraction. Understanding the underlying coordination chemistry to improve hydrometallurgical methods is crucial in order to meet the demand for critical metals for use in modern technologies, reduce the environment impact of recovery from primary mining deposits, and recycle valuable metals from secondary sources (e.g. mobile phones, WEEE). Chapter 2 examines the use of a simple primary amide that can load gold and other chloridometalates into a toluene phase through an outer-sphere mechanism. The loading of a variety of metals/metalloids from varying [HCl] is reported, highlighting the selectivity for gold over other metalates and chloride due to a combination of speciation of those metals and the relative ease of extraction of lower charged species (the Hofmeister bias). The advantages in loading/stripping, toxicity and mass balances compared to commercial alternatives are also outlined, in particular the efficacy of separating gold from a mixed-metal solution representative of those found in WEEE. The mode of action of the primary amide (and secondary/tertiary analogues) is determined using slope analysis, Karl-Fischer water determinations, NMR and MS measurements, EXAFS and computational models. The extraction occurs by the dynamic assembly of multiple amide ligands and gold metalates to generate supramolecular clusters held together through hydrogen-bonding and electrostatic interactions. The secondary and tertiary amides are found to be able to extract monoanionic metalates in a similar manner as the primary amide, although clustering occurs to a lesser extent. Whilst the secondary and tertiary amides are stronger gold extractants than the primary amide, they are not observed to be as successful when extracting from a mixed-metal solution. Instead, a 3rd phase is seen to form from these amides and some metals at higher metal concentrations, which removes the ligands from solution and prevents successful extraction of gold. Chapter 3 builds on an observation in Chapter 2 that a synergistic combination of a simple primary amide and an amine can extract chloridometalates that are typically difficult to solvent extract, such as iridium(III) and rhodium(III). These metalates, complexes with increased anionic charge and varying speciation in aqueous solution, are typically recovered last in a metal production flowsheet. The combination of a primary amide and primary amine was found to be the most effective at extracting the chloridometalates; the strength and strippability of the system is of particular interest in the context of rhodium(III) recovery as this metal currently is not extracted in commercial circuits. The mode of action of the system is investigated using similar techniques to Chapter 2, and reveals that the amine is the more important component of the synergistic mixture compared to the amide, with an improvement in extraction observed when both components are present. Rh(III) is extracted as a mixture of RhCl6 3– and RhCl5(OH2)2– complexes, dependent on the initial [HCl] concentration and the age of the initial aqueous solution. Chapter 4 investigates the feasibility of the recovery of lanthanides as anionic metalates from chloride-, nitrate- or sulfate-rich feeds. Reagents that have been found to be strong chloridometalate extractants, fragmented versions of these, and ‘classic’ commercial outer-sphere reagents are studied. The variations of ligand, anion type and concentration, proton concentration and solvent for the extraction of lanthanides is investigated. However, despite these permutations, no extraction of lanthanides is observed due to the difficulty in extracting more highly hydrated species and the lack of stability of the metalates in aqueous solution.

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Smit, Danie Strydom. "The leaching behaviour of a Ni-Cu-Co sulphide ore in an oxidative pressure-acid medium / Danie Strydom Smit." Thesis, Potchefstroom University for Christian Higher Education, 2001. http://hdl.handle.net/10394/9626.

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Hydrometallurgical processing of sulphide concentrates is an attractive method for the selective extraction of valuable metals. The dissolution of minerals in a leaching process involves several electrochemical parameters that need to be investigated• to ensure the development and growth of the base metal industry in South Africa. A study has been carried out to elucidate the leaching mechanism of a nickel-coppercobalt sulphide concentrate in an oxidative pressure-acid medium. The sulphide concentrate studied in this research, comprises mainly of the minerals pyrrhotite, (Fe1_xS) with x = 0 to 0.2, pentlandite, (Ni,Fe)9S8 and chalcopyrite, (CuFeS2). The leaching behaviour of these minerals was successfully studied by means of Atomic Absorption (AA) measurements, Scanning '•Electron Microscopy (SEM) and Moss bauer spectroscopy, after leaching took place in an oxidative pressure-acid medium. The dissolution of the valuable metals was achieved effectively with recoveries of well over 90% for nickel, copper and cobalt under the specific conditions studied. Mechanical activation by means of ultra fine milling improved metal extraction with an average of approximately 40%, after a leaching period of 150 minutes. The most suitable conditions for the oxidative pressure-acid leaching of the mechanically treated nickel-copper-cobalt sulphide concentrate in a dilute sulphuric acid medium were found to be: particle size 80% - 10J.Lm; temperature l10°C; oxygen partial pressure 10 bar; sulphuric acid concentration 30 kg/ton; solids content 15% by mass and an impeller agitation rate of 800 r/min. The values of the apparent activation energies of nickel, copper and cobalt, extracted from the sulphide concentrate, were found to be 20.6 (± 4.4) kJ/mol K, 33.6 (± 4.2) kJ/mol K and 17.4 (± 3.5) kJ/mol K respectively.
Thesis (MIng (Chemical Engineering))--Potchefstroom University for Christian Higher Education, 2001

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Perez, Isadora Dias. "Recuperação de cobre de uma solução sintática baseada no licor de lixiviação atmosférica do minério limonítico de níquel por troca iônica utilizando a resina quelante Dowex." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-04052018-142357/.

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Em virtude das várias aplicações do cobre, acredita-se que a demanda por esse metal irá aumentar nos próximos anos, e consequentemente, o seu preço. Dessa forma, as mineradoras enfrentam o desafio de aprimorar e aperfeiçoar os processos produtivos a fim de atender sua futura demanda. Frações de cobre podem ser encontradas no licor de lixiviação do minério limonítico de níquel e a troca iônica com adsorvente sólido é uma das tecnologias disponíveis para promover a sua recuperação e o seu reaproveitamento. O presente trabalho teve como objetivo estudar o processo de adsorção dos íons de cobre presente em um licor sintético baseado no licor de lixiviação atmosférica do minério limonítico de níquel através de um sistema de resina de troca iônica utilizando a resina quelante Dowex XUS43605. A viabilidade da técnica escolhida foi analisada em função da influência de parâmetros por meio de ensaios em batelada e coluna de leito fixo utilizando uma solução sintética. O tempo de contato, o pH, a massa de resina e a temperatura foram avaliados. A resina quelante Dowex XUS43605 mostrou-se mais seletiva para o cobre em pH igual a 1,5, tendo sido definido esse pH como o de trabalho. Verificou-se que 1g é uma dosagem suficiente para recuperar o cobre da solução em escala laboratorial considerando 50mL de solução sintética. O incremento na temperatura não alterou a adsorção do cobre pela resina, sendo determinado que a temperatura de trabalho esteja entre 25-35°C. O modelo de isotermas de adsorção de Langmuir apresentou melhor ajuste entre a resina e o cobre do que os modelos de Freundlich e de Temkin. O modelo cinético pseudosegunda-ordem descreveu o processo de adsorção considerando a quimiossorção como a etapa limitante. Os ensaios em coluna de leito fixo possibilitaram a produção de uma solução com concentração reduzida de Cu2+ em 93% na etapa de carregamento. Pela etapa de eluição com ácido sulfúrico (H2SO4) 1mol/L, obteve-se uma solução 10 vezes mais concentrada em Cu2+ com relação à solução sintética. A solução resultante da etapa de eluição seguiu para os ensaios de precipitação, a qual permitiu a separação do cobre dos íons metálicos pela ação do agente precipitante CaCO3 e a geração de um precipitado composto por três fases: brochantite [Cu4SO4(OH)6], posnjatike [Cu4SO4(OH)6.H2O] e gesso (CaSO4.2H2O).
Considering the various applications of copper, it is believed that the demand for copper will increase in the coming years and, consequently, its price. Hence, the mining companies face the challenge of improving the productive processes to supply their future demand. Copper fractions can be found in liquor leaching nickel limonite ore and ion exchange with solid adsorbent is one of the available technologies which promote its recovery and reuse. The present work was aimed at studying the adsorption process of copper ions present in a synthetic liquor based on the atmospheric leaching liquor of the nickel limonite ore through an ion exchange resin system using Dowex XUS43605 chelating resin. The feasibility of the chosen technique was analyzed in relation to the influence of parameters by means of batch and fixed bed tests using a synthetic solution. The contact time, pH, amount of resin and temperature were evaluated. Dowex XUS43605 chelating resin showed to be more selective for copper at pH 1.5, and this pH was defined as the working pH. It has been found that 1g is a sufficient dosage to recover copper from the solution on a laboratory scale considering 50mL of synthetic solution. The increase in temperature did not change the adsorption of the copper by the resin, and it was determined that the working temperature is between 25-35°C. The Langmuir adsorption isotherms model showed a better fit between resin and copper than the Freundlich and Temkin models. The pseudosecond-order describes the sorption process and it indicates that the rate-limiting step is chemisorption. The fixed bed column tests allowed the production of a solution with reduced concentration of Cu2+ in 93% the loading step. By the elution step with 1mol/L of sulfuric acid (H2SO4), a solution 10 times more concentrated in Cu2+ was obtained in relation to the synthetic solution. The solution from the elution step followed to the precipitation tests, which allowed the separation of copper from the metal ions by the action of the precipitating agent CaCO3 and the generation of a precipitate composed of three phases: brochantite [Cu4SO4(OH)6], posnjatike [CuSO4(OH)6.H2O] and gypsum (CaSO4.2H2O).

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Caldas, Marcos Paulo Kohler. "Síntese de nanopartículas de prata a partir da reciclagem de placas de circuito impresso." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-20072017-151234/.

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A recuperação de metais presentes em equipamentos eletroeletrônicos tem atraído interesse em virtude de novas e diferentes tecnologias que visam a reutilização desses elementos químicos em novos processos produtivos. A recuperação de prata de placas de circuito impresso (PCI) na forma de nanopartículas é uma alternativa para reutilização deste metal nobre. Este trabalho teve como objetivos: recuperar a prata presente em placas de circuito impresso através de uma rota hidrometalúrgica; separar a prata dos demais metais e utilizar a prata recuperada para sintetizar nanopartículas de prata. Para desenvolvimento do trabalho, foram utilizados dois modelos de PCIs com diferentes composições: placa mãe e placa de memória de computadores obsoletos. As placas foram caracterizadas por digestão em água régia, análise granulométrica, análise em lupa binocular, microscopia eletrônica de varredura (MEV) e perda ao fogo. Foi definida uma rota hidrometalúrgica para recuperação da prata após um estudo de três rotas possíveis. A rota hidrometalúrgica definida para recuperação da prata, para os dois modelos de PCIs, envolveu uma primeira lixiviação em meio ácido sulfúrico a 95ºC, por 18 horas e uma segunda lixiviação em ácido sulfúrico em meio oxidante (adição de peróxido de hidrogênio - H2O2) a 95ºC por 6 horas. Esta rota descarta a técnica de separação magnética e separação eletrostática, pois o metal em estudo é encontrado em pequenas concentrações nos resíduos eletroeletrônicos. O licor lixiviado foi caracterizado por espectrometria de emissão óptica com acoplamento de plasma induzido (ICP-OES). Após o processo de lixiviação, a prata foi isolada dos demais metais na forma de AgCl, através de processo de precipitação seletiva utilizando NaCl. A síntese de nanopartículas de prata foi feita utilizando o citrato de sódio como agente estabilizante. Os resultados obtidos neste trabalho permitem concluir que foi possível recuperar 100% da prata presente nas placas de circuito impresso proveniente de computadores obsoletos, por meio da rota hidrometalurgica utilizada. Após a lixiviação, a prata foi isolada. Com a prata isolada, foi possível a síntese de nanopartículas de prata com diâmetro médio de 60 a 80nm.
The recovery of metals present in waste electric and electronic equipment (WEEE) has attracted interest due to the new and different technologies that aim to reuse these chemical elements in new production processes. Recovering silver from printed circuit boards (PCI) into nanoparticles form is an alternative to reuse this noble metal. This work aims to: recover the silver present in printed circuit boards through a hydrometallurgical route; to separate silver from the other metals and to use the recovered silver to synthesize silver nanoparticles. For the development of this work two models of PCIs with different compositions were used: motherboard and random-access memory (RAM) devices from obsolete personal computers. The PCIs were characterized by aqua regia digestion, particle size analysis, stereo microscope analysis, scanning electron microscopy (SEM) and loss on ignition. A hydrometallurgical route for silver recovery was defined after a study of three possible routes. The hydrometallurgical route defined to recover silver from the two models of PCIs involved a first step of leaching in sulfuric acid solution at 95ºC for 18 hours and a second leaching step in sulfuric acid in an oxidizing solution (with addition of hydrogen peroxide - H2O2) at 95° C for 6 hours. This route discards the technique of magnetic and eletrostatic separation because the metal under study is found in a small concentration in the electric and electronic waste. The leached liquor was characterized by inductively coupled plasma optical emission spectrometry (ICP-OES). After the leaching process, the silver was isolated from the other metals in the form of AgCl, through a selective precipitation process using NaCl. The synthesis of silver nanoparticles was accomplished using sodium citrate as stabilizing agent. The obtained results in this work allows to conclude that it is possible to recover 100% of the silver present in printed circuit boards from obsolete computers, through the hydrometallurgical route. After leaching, silver was isolated. It was possible to synthesize nanoparticles with an average diameter of 60 to 80 nm.

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Freitas, Regeane Martins de. "Estudo da precipitação oxidativa do manganês presente na drenagem ácida da mina." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2012. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=279.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Na drenagem ácida de mina a contaminação pelo manganês é notável e se caracteriza como um dos principais problemas ambientais vivenciados pela indústria mineradora. Este elemento tem sido frequentemente encontrado em concentrações muito acima do limite permitido para o lançamento que, de acordo Resolução CONAMA No. 430, é de 1,0 mg/L. Neste contexto, a precipitação oxidativa com KMnO4, quando empregada para recuperação e remoção do manganês, se destaca como um processo promissor. Neste trabalho, a primeira etapa constou de um planejamento estatístico onde foi possível a avaliação da influência de parâmetros de processo e a modelagem empírica da precipitação oxidativa do Mn II em amostras preparadas em laboratório. Foram avaliados quatro parâmetros: a dose de KMnO4, o pH, o tempo de reação e a concentração da solução de KMnO4. Apenas a dose de KMnO4, o pH e a interação entre estes dois fatores apresentaram influência significativa sobre o processo de precipitação oxidativa do manganês. Na etapa de otimização, a análise do aspecto das superfícies de resposta, descritas por modelos matemáticos empíricos, permitiu avaliar as combinações entre o pH e a dose de KMnO4 que contribuem para uma maior eficiência do processo. Os melhores resultados foram obtidos para doses de KMnO4 de 1,63 mg KMnO4/mg Mn II em pH 3,0 e 1,54 mg KMnO4/mg Mn II em pH 5,0. As remoções de manganês observadas nestas condições foram 99,84% e 99,90% respectivamente, para uma concentração inicial de 100 mg/L. Posteriormente, o estudo cinético do processo utilizando soluções de Mn II preparadas em laboratório, mostrou que a precipitação do manganês com KMnO4 apresenta a vantagem de ser rápida. A concentração de Mn II decresceu exponencialmente atingindo limites inferiores a 1,0 mg/L em menos de 10 minutos de reação. A cinética da reação foi favorecida com a elevação do pH. Os precipitados formados apresentaram baixa cristalinidade com pequenas diferenças morfológicas em função do pH do meio, sendo a fase mineralógica encontrada a birnessita (MnO2), de acordo com espectroscopia RAMAN. Estas observações experimentais estão de acordo com os resultados da modelagem realizada com o programa PHREEQC, na qual a presença do óxido de manganês MnO2 foi confirmada nas fases birnessita, pirolusita e nsutita. Na etapa final, amostras de drenagem ácida oriundas de uma antiga mina de urânio desativada foram caracterizadas quimicamente e submetidas ao tratamento com KMnO4 em escala laboratorial. A caracterização das amostras mostrou que os parâmetros que estão fora da especificação segundo a legislação são o manganês, o fluoreto e também o pH. Além disso, as concentrações de cálcio, alumínio e sulfato são relativamente elevadas. O ensaios de precipitação oxidativa foram conduzidos em valores de pH 3,0, 5,0 e 7,0. Em pH 7,0 o processo mostrou-se mais eficiente, não apenas em relação a remoção de Mn II, que alcançou níveis de aproximadamente 99 %, mas também em termos da velocidade de reação, sendo o equilíbrio atingido em 10 min de reação. Verificou-se uma remoção mais significativa dos outros componentes como ferro, alumínio e urânio na etapa de ajuste do pH para 7,0 com NaOH. Os precipitados formados na etapa de oxidação não apresentaram cristalinidade, contudo foram identificadas as fases birnessita (MnO2), hausmanita (Mn3O4) e manganita (MnOOH), de acordo com espectroscopia RAMAN. Além do manganês, foram detectados nos precipitados: alumínio, cálcio, zinco, urânio, terras raras, oxigênio e flúor. A simulação com o PHREEQC permitiu a identificação das fases termodinamicamente possíveis em cada etapa do processo. Na etapa de ajuste de pH foram formadas, principalmente, fases contendo ferro, urânio, alumínio e o manganês. A etapa de adição do agente oxidante foi caracterizada por remoções de manganês nas fases birnessita (MnO2), bixbyita (Mn2O3), hausmanita (Mn3O4), manganita (MnOOH), nsutita (MnO2), pirolusita (MnO2) e cálcio na forma de fluorita (CaF2)
The manganese contamination present in acid mine drainage is outstanding as one of the main environmental issues experienced by the mining sector. This element has been frequently found in concentrations much higher than the allowed limit for discharge which is 1.0 mg/L according to Brazilian legislation, CONAMA No. 430. In this context, the oxidative precipitation by KMnO4, when employed to recover and remove manganese is a promising process. In this work, throughout a statistical design it was possible to assess the influence of process parameters as well as the empirical modeling of oxidative precipitation of Mn II in laboratory prepared samples. The experiments consisted of evaluating four parameters: the KMnO4 dose, pH, reaction time and concentration of KMnO4 solution. Only the dose of KMnO4, the pH and the interaction between these two factors have shown significant influence. In the optimization stage, by observing the aspect of the response surfaces, described by empirical mathematical models, it was possible to find out the combinations between pH and KMnO4 dose that could increase the process efficiency. The best results were obtained throughout trials conduct at pH 3.0 with KMnO4 ratio of 1.63 mg KMnO4/mg Mn II and at pH 5.0 with ratio of 1.54 mg KMnO4/mg Mn II. The manganese removals under these conditions were 99.84% and 99.90%, respectively. Subsequently, the kinetics study was carried out by using solutions of Mn II prepared in the laboratory. The results have shown that the precipitation of manganese by KMnO4 has the advantage of being fast. The concentration of Mn II decreases exponentially reaching the lower limit of 1.0 mg/L around 10 minutes of reaction. Additionally, the kinetics of the reaction is favored with increasing pH. The produced precipitates have low crystallinity and show slight morphologic differences according to the pH assessed. The main mineral phase identified by RAMAN spectroscopy was birnessite (MnO2). These experimental observations match with the modeling results performed withPHREEQC, in which the presence of manganese oxide MnO2 was identified as birnessite, pyrolusite and nsutita. In the final step, samples of acid mine drainage originated from one former and inactive uranium mine were chemically characterized and underwent with KMnO4 in bench scale. The samples characterization showed that manganese, fluoride and the pH are beyond limits set by legislation. Furthermore, the calcium, aluminum and sulphate are present in relatively high concentrations. The oxidative precipitation trials were carried out at pH 3.0, 5.0 and 7.0. At pH 7.0 the process was more efficient for the removal of Mn II, which accomplished levels of approximately 99%, and also in terms of reaction rate, the equilibrium was achieved within 10 min of reaction. Under the same condition i.e., at pH 7.0, there was an increase in the removal of other components such as iron, aluminum and uranium. The precipitates formed were not crystalline; nevertheless it was possible to identified the phases birnessite (MnO2), and possibly hausmanita (Mn3O4) and manganite (MnOOH) by RAMAN spectroscopy. Besides manganese, the species aluminum, calcium, zinc, uranium, rare earths, oxygen and fluorine were also detected in the precipitated. The simulation with PHREEQC enabled the identification of thermodynamically possible phases at each stage of the process. In the step of pH adjustment, essentially, phases containing iron, uranium, manganese and aluminum are formed. The adding of KMnO4 is characterized by manganese and calcium removal as birnessite (MnO2), bixbyite (Mn2O3), hausmaninte (Mn3O4), manganite (MnOOH), nsutite (MnO2), pyrolusite (MnO2) and fluorite (CaF2).

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Huang, Jian Hui. "The applications of microwave energy to improve grindability and extraction of gold ores." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369344.

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Oxidation developed from the surfaces into the cores of the microwaved particles. Metallic particles were also formed during microwave exposure. Lihir gold ore, in which gold was finely disseminated in pyrite and marcasite, was an extremely refractory gold ore. Without pretreatment, only 37-39% of the gold could be extracted with sodium cyanide. However, this was improved after the head ores or floatation concentrates were pretreated by microwave radiation. 74.581.2% of the gold was extracted from the microwave treated head ore. The hydrometallurgical pretreatment of pyrite and marcasite in a microwave field and a conventional heating environment was also investigated.I,n a nitric acid solution, pyrite and marcasite can be rapidly leached. Reaction temperature and the concentration of HNO3 had a significant influence on decomposition rate. Marcasite had a substantially higher i decomposition rate than pyrite. Microwave heating could promote the dissociation of marcasite and pyrite, compared with conventional heating. This was caused by special volumetric heating during microwave exposure that may induce local overheating or improve the interactions between the high dielectric loss minerals and the leaching solution. Kinetic investigations show that the decomposition of both the minerals in a nitric acid medium is controlled by chemical reactions on the surfaces of particles. The decomposition is a second order reaction with respect to nitric acid concentration. Less than 5- 7% of the decomposed sulphur was transformed into elemental sulphur during the leaching of both the minerals

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47

Epamino, Ulisses Condomitti. "Desenvolvimento de métodos magnetoeletroquímicos para sensoriamento, remediação ambiental e nanohidrometalurgia magnética." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-09052013-081443/.

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Esta tese descreve o desenvolvimento de aplicações de nanopartículas superparamagnéticas de magnetita, devidamente funcionalizadas, nas seguintes áreas: Sensoriamento - As nanopartículas superparamagnéticas foram utilizadas em conjunto com um pequeno sistema analítico especialmente desenvolvido para esse trabalho, na análise de diversos metais pesados de grande relevância ambiental. O ponto de destaque da metodologia é o grande incremento em intensidade do sinal analítico em função da pré-concentração que pode ser realizada mediante utilização das nanopartículas superparamagnéticas e aplicação de um campo magnético externo. Remediação ambiental - A grande afinidade das nanopartículas por diversos materiais foi aproveitada na obtenção de um sistema de remediação ambiental que combina as propriedades magnéticas das nanopartículas e as propriedades adsorventes de carvão ativado. Esse sistema foi testado em contaminantes orgânicos e inorgânicos e permite uma maneira eficiente e inovadora de remoção de contaminantes em meio aquoso. Nanohidrometalurgia magnética - Os efeitos de pré-concentração de nanopartículas superparamagnéticas modificadas foram utilizados para melhorar a eficiência dos processos hidrometalúrgicos atuais para produção de cobre metálico a partir de minérios com baixa concentração do metal, chegando - se ao estado da arte da técnica.
This thesis describes the development of applications of superparamagnetic magnetite nanoparticles, properly functionalized, in the following areas: Sensing - The superparamagnetic nanoparticles were used in conjunction with a small analytical system specially developed in this work for analysis of several heavy metals of great environmental significance. The important point of this methodology is the general increase in intensity of the analytical signal as a function of pre-concentration may be performed by use of superparamagnetic nanoparticles under the influence of an external magnetic field. Environmental Remediation - The high affinity of nanoparticles for various materials was used to obtain an environmental remediation system that combines the properties of magnetic nanoparticles and the properties of activated carbon adsorbents. This system was tested in organic and inorganic contaminants and provides a novel and efficient removal of contaminants in the aqueous medium. Magnetic Nanohydrometalurgy - The effects of pre-concentration fro the funcionalized superparamagnetic nanoparticles modified were used to improve the efficiency of the actual hydrometallurgical processes used for production of metallic copper from ores with low concentration of metal, showing good perspectives of improving the state of the art of this technique.

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Zuccheratte, Ana Cristina Vieira. "Recuperação de zinco e índio de monitores de computadores sucateados." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2013. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=297.

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Este trabalho apresenta o estudo de recuperação de índio (In) e zinco (Zn) presentes em telas de monitores de computadores sucateados, por meio de técnicas hidrometalúrgicas. O trabalho foi subdividido em duas partes distintas: dissolução dos metais In e Zn mediante digestão ácida do pó de revestimento da tela de monitores e separação dos metais pela técnica de extração por solventes. Na etapa de dissolução dos metais, investigou-se a influência das seguintes variáveis de processo: tipo de reagente, relação ácido/amostra, tempo de reação e temperatura. Após a otimização dos parâmetros do processo, obteve-se uma dissolução de índio superior a 95% e de Zn superior a 99,5%. Foi obtido um licor contendo 9,8 g/L de zinco, 1,49 g/L de índio e 102 g/L de sulfato, contendo como impureza 0,016 g/L de ferro, e acidez de 2,2 mol/L (pH = 0,34). Após a definição das melhores condições de abertura química, a amostra foi processada para a obtenção do licor para a realização dos experimentos de extração por solventes. Foram realizados experimentos descontínuos de extração por solventes para a verificação da viabilidade técnica e melhores condições de separação dos metais, e um experimento contínuo para o carregamento do solvente. Na etapa de extração, as variáveis de processo investigadas foram: tipo de extratante, pH do licor e tempo de reação. Os experimentos foram realizados na relação volumétrica aquoso/orgânico (A/O) igual a 1 e concentração de extratante de 1,0 mol/L. Os extratantes investigados foram: DEHPA, IONQUEST 801 e CYANEX 272. O estudo das variáveis foi realizado apenas com os dois primeiros extratantes. Os experimentos de reextração foram realizados com HCl e H2SO4, na relação volumétrica de 1:1 e em diferentes concentrações dos ácidos. Os experimentos de bancada indicaram que a separação dos metais pode ser realizada usando DEHPA 1,0 mol/L como extratante, o H2SO4 1,0 mol/L como agente de lavagem, para a reextração dos elementos coextraídos com o índio (principalmente Zn), e HCl 3,0 mol/L para a reextração do In do orgânico carregado.
This work presents the study of recovery of indium (In) and zinc (Zn) present in computer monitor screens by means of hydrometallurgical techniques. This work was divided into two distinct parts: one is the dissolution of the metals In and Zn through acid digestion of the sample and the separation of the metals through solvent extraction technique. In the acid dissolution, the influence of the following process variables was investigated: type of reagent, acid/sample ratio, time of reaction and temperature. Following the optimisation of the parameters of the process, dissolution of indium above 98% and of Zinc over 99.5% was achieved. A liquor containing 9.8 g/L of zinc, 1.49 g/L of indium and 102 g/L of sulphate having as impurity 0.016 g/L of iron, and acidity of 2.2 mol/L (pH = 0.34) was obtained. After the optimization of the chemical opening conditions, the sample were processed in order to obtain the liquor for the solvent extraction experiments. Batch experiments of solvent extraction aiming at verifying the technical viability and best conditions for the separation of the metals and a continuous experiment to load the solvent were carried out. In the extraction phase, the process variables investigated were: type of extractant, pH of the liquor, and reaction time. The experiments were carried out at an aqueous/organic (A/O) volumetric ratio equal 1:1 and concentration of extractant 1.0 mol/L. The extractants investigated were DEHPA, IONQUEST 801 and CYANEX 272. The study of the variables was carried out with DEHPA and IONQUEST 801. The stripping experiments were carried out with HCl and H2SO4, at a volumetric ratio 1 with different acids concentrations. The batch experiments indicated that the separation of the metals In and Zn can be done using DEHPA 1 mol/L as extractant, H2SO4 1 mol/L as scrubbing agent and HCl 3 mol/L as stripping agent. After defining the best conditions for the extraction, scrubbing and stripping steps a continuous experiment was programmed. The McCabe-Thiele diagrams indicated that 3 extractions stages and 7 stripping stages was enough to extract and strip the In from the liquor and the loaded organic respectively. Due to the small amount of the liquor, the continuous experiment contemplate only the extraction and scrubbing steps. The experiment was done in mixer-settler cells, with capacity of 70 mL in the mixer and 250 mL in the settler, in a counter current system. The stripping step was carried out in batches simulating the counter current system. The continuous experiment (extraction and scrubbing steps) were carried out with the use of DEHPA 1.0 mol/L as the extractant agent and a solution of H2SO4 1.0 mol/L as the scrubbing agent in order to remove the impurities extracted. Four extraction stages and 4 stages were employed in each step, using a volumetric ratio A/O equal 5:1 in the extraction and a volumetric ration O/A equal 4:1 in the scrubbing step. A loaded organic containing 7.5 g/L of In and 0.003 g/L of Zn and a raffinad containing 9.4 g/L Zn and less than 0.001 g/L of In were obtained from a liquor containing 9.8 g/L and 1.49 g/L. The content of the metals in the stripped solution were 26.7 g/L de In e 0.001 g/L de Zn.

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49

Omelchuk, Kateryna. "Etude physicochimique de nouveaux agents d’extraction pour la récupération du cobalt, du nickel et du manganèse en milieu chlorure par extraction liquide-liquide." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEC003.

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Les ressources minérales sont actuellement au centre des préoccupations de l’Europe comme l’illustre le programme Européen Horizon 2020 qui pour la première fois met la problématique des ressources au cœur des débats. Une des priorités est notamment de développer des procédés innovants capables d’extraire sélectivement des métaux à haute valeur ajoutée (métaux critiques ou stratégiques) à partir des gisements provenant des activités minières (ressources primaires) ou du recyclage (ressources secondaires). Par exemple, en ce qui concerne les ressources secondaires, le Parlement Européen a établi une directive en 2006 qui régularise la gestion des accumulateurs en fin de vie en interdisant notamment la mise en décharge ou l'incinération des déchets électroniques. Ceci force les producteurs de batteries à gérer la fin de vie de leurs produits et favorise l’émergence de travaux de Recherche et de Développement sur la conception de procédés de recyclage innovants. Ces procédés doivent avoir un impact minimal sur l'environnement tout en étant économiquement viables. En ce qui concerne les ressources primaires, l’exploitation de ressources de plus en plus complexes forcent les entreprises minières à élaborer de nouveaux procédés qui se doivent d’être efficaces, durables et le moins coûteux possible afin de rester compétitif malgré des cours de métaux très fluctuants. Par exemple, deux des challenges des prochaines années reposent sur le développement de procédés capables de séparer à moindre coût le cobalt, le nickel et le manganèse contenus dans les latérites ou bien le cobalt, le nickel, le manganèse et le lithium contenus dans les batteries lithium-ion usagées dont la production va augmenter exponentiellement ces prochaines décennies avec l’émergence du véhicule électrique. L’objectif de cette thèse est de comprendre les phénomènes physicochimiques impliqués dans l’extraction de ces métaux par de nouvelles molécules extractantes synthétisées au laboratoire afin de développer des modèles physicochimiques pouvant être intégrés dans les modèles d’optimisation des procédés hydrométallurgiques. Ces modèles pourront trouver des applications dans l’optimisation des procédés de séparation du cobalt, du nickel, du manganèse et du lithium contenus dans des ressources primaires et secondaires comme les latérites (pour l’ensemble des métaux cités précédemment à l’exception du lithium) ou les batteries lithium-ion (pour l’ensemble des métaux cités précédemment)
Cobalt and nickel are strategic metals from many applications including alloys manufacturing, electrode materials for lithium-ion batteries (LIBs), etc. Their recovery from spent materials is a good opportunity from economical and geopolitical viewpoints as these metals are expensive and recycling reduces considerably supply risks of cobalt and nickel, particularly in the forthcoming years during which cobalt and nickel demands will likely increase significantly with the emergence of electric vehicles. Therefore, recovery of cobalt and nickel from LiBs is strategic and development of efficient and economic processes is coming to the fore. Several research activities were carried out to recycle strategic metals from spent batteries by different methods such as pyrometallurgy, hydrometallurgy and biohydrometallurgy. Pyrometallurgical processes are however energy intensive and release gases like sulfur dioxide and carbon dioxide which are harmful to the environment. In recent past, metallurgical industry has been searching for hydrometallurgical processes due to some advantages such as possibility of treating low-grade resources, easier control of wastes and lower energy consumption. Hydrometallurgical processes are based on physical separation, leaching, purification, precipitation and in some cases electrowining. The demand for high purity metals and recent trends towards environmentally friendly technology has focused more attention onto solvent extraction because this technology is mature and permits to achieve high extraction efficiency at low operating costs. Cyanex 272 is a dialkyl phosphinic acid extractant widely used for the separation of cobalt from nickel to obtain high purity cobalt salts that can be reused to produce high-grade products for lithium-ion batteries. However, extraction occurs at pH close to 4 for cobalt and 6 for nickel and addition of alkaline solutions to adjust the pH is required. In order to decrease operating expenditure, the use of extracting agents capable to recover and separate cobalt, nickel, lithium and manganese at lower pH and in few stages is mandatory. The aim of this work is to study the influence of the chemical structure of various organophosphorus compounds synthesized at the laboratory scale on the extraction efficiency of cobalt and nickel vs. pH. In particular, the influence of branching, hydrophobicity and the presence of oxygen atoms in alkyl chains has been investigated for several organophosphorus compounds such as bis(1,3-dibutoxypropan-2-yl) phosphoric acid, bis(1,3-diisobutoxypropan-2-yl) phosphoric acid, bis(5,8,12,15-tetraoxanonadecan-10-yl) phosphoric acid and bis(undecan-6-yl) phosphoric acid

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50

Kameoka, Fernando. "Reciclagem de resíduos eletroeletrônicos: um estudo cinético da lixiviação ácida de ferro de placas de circuito impresso de microcomputadores." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-07072016-144159/.

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O aumento no consumo mundial de novos aparelhos eletroeletrônicos aliado à redução no tempo de vida útil destes equipamentos tem como principal consequência ao meio ambiente a geração de resíduos. No Brasil, com a instituição da Política Nacional de Resíduos Sólidos, criou-se a obrigatoriedade legal da responsabilidade dos fabricantes pela logística reversa dos equipamentos eletroeletrônicos, incentivando pesquisas para o desenvolvimento dos métodos de reciclagem e tratamento dos materiais descartados. O processo de lixiviação foi avaliado como alternativa à etapa de separação magnética presente nas atuais rotas hidrometalúrgicas para recuperação de metais valiosos de placas de circuito impresso. Para avaliar a composição das placas, foi realizado ensaio de dissolução em água régia. As amostras foram moídas e submetidas a ensaios de lixiviação com ácido sulfúrico nas concentrações de 1 e 2mol/L, às temperaturas de 75ºC, 85ºC e 95ºC, durante 24 horas. Com ácido sulfúrico 2mol/L a 95ºC, o tempo necessário para se obter 100% de extração do ferro foi de 2 horas. Nestas condições, não foi detectada a presença de cobre dissolvido. A cinética da reação é controlada por reação química e obedece a equação .=1(1)3. A energia de ativação aparente do processo equivale a 90kJ/mol.
The increase in world consumption of new electronic equipment along with the reduction of its lifespan has brought an environmental issue due to waste generation. In Brazil, the National Solid Waste Policy establishes that manufacturers should respond for the reverse logistics of consumer electronics devices. This policy encouraged research to the development of methods of treatment and recycling of discarded materials. Acid leaching was analyzed as an alternative to the magnetic separation process widely used in hydrometallurgical routes for precious metals recovery from PCBs. Aqua regia was used to dissolve PCBs and thus characterize samples. The samples were milled and leached with sulfuric acid 1 and 2mol/L, at temperatures of 75ºC, 85ºC and 95ºC, during 24 hours. With sulfuric acid 2mol/L at 95ºC, the necessary time for 100% iron extraction was 2 hours. Under these conditions, no copper was detected. Reaction kinetics is controlled by chemical reaction and follows the expression .=1(1)3. Apparent activation energy equals 90kJ/mol.

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