To see the other types of publications on this topic, follow the link: Extraction of metal ores.
Dissertations / Theses on the topic 'Extraction of metal ores'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Extraction of metal ores.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Stewart, Neil Stuart. "The technology and control of mining in Roman Britain." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249933.
Full text
2
Hung, Laurence. "Etude d’un procédé d’extraction en milieu CO2 supercritique de l’uranium à partir de minerais." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4310.
Full textAbstract:
La recherche de nouveaux procédés propres et durables pour extraire l’uranium des minerais en alternative à l’extraction liquide-liquide conduit à s’intéresser aux procédés d’extraction en milieu CO2 supercritique. L’objectif de ce travail est donc d’étudier la faisabilité de l’extraction de l’uranium des minerais en milieu CO2 supercritique, à l’aide de molécules extractantes adaptées. Dans un premier temps, des mesures de solubilité des ligands sélectionnés pour cette étude préliminaire, trioctylamine et PC88A (acide 2-éthylhexyl 2-éthylhexyl phosphonique), et des complexes métalliques que ces molécules forment avec le molybdène utilisé comme simulant inactif de l’uranium et l’uranium, ont été effectuées en milieu CO2 supercritique. L’étude du procédé d’extraction dynamique en milieu CO2 supercritique a ensuite été réalisée en inactif, d’abord sur une solution aqueuse sulfurique de molybdène puis sur des poudres d’oxydes de molybdène. Les étapes de solubilisation du complexe ligand-Mo en CO2 supercritique et d’attaque du solide par le système extractant (ligand/acide/oxydant) sont les étapes limitantes à contrôler. Le choix d’un système extractant adapté devient alors primordial. En tenant compte des résultats obtenus en inactif (Mo), des essais d’extraction sur minerai d’uranium à partir de PC88A en milieu CO2 supercritique ont finalement été réalisés en présence d’acide sulfurique et d’oxyde de manganèse. Le procédé a ainsi pu être validé, plus de 60 % de l’uranium du minerai a été collecté en sortie de montage. Toutefois, l’effet de certains paramètres opératoires reste à étudier ainsi que la synthèse/sélection de nouvelles molécules extractantes cibléesThe research of clean and sustainable new processes to extract uranium from ores as an alternative to solvent extraction leads one to consider extraction processes using supercritical carbon dioxide. The aim of this work is to study the extraction feasibility of uranium ores by supercritical CO2, using suitable ligands. First, solubility measurements of selected ligands, trioctylamine and PC88A (2-ethylhexyl 2-ethylhexylphosphonic acid), and metal complexes formed between these ligands and molybdenum (uranium surrogate) or uranium, are performed in supercritical CO2. Supercritical CO2 extractions are then carried out on sulfuric aqueous solutions containing molybdenum and on molybdenum oxides powder. Solubilization of the extractant system (ligand/acid/oxidant) and solid leaching are the key steps which need to be controlled. Well-suited extractant system selection is therefore fundamental. The hypothetical mechanisms, describing supercritical carbon dioxide extraction, seem to be quite different from those usually observed in solvent extraction, especially in terms of selectivity and formed complex structure. Based on the results obtained with molybdenum, extraction trials on uranium ores were then conducted using PC88A in supercritical carbon dioxide with sulfuric acid and manganese oxide. More than 60% of uranium was recovered, which confirmed this new process feasibility. However, the influence of some operating parameters and the synthesis/selection of new suitable ligands remain to be further studied
3
Buyukakinci, Ergin. "Extraction Of Nickel From Lateritic Ores." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609291/index.pdf.
Full textAbstract:
The aim of this study was to extract nickel and cobalt from the lateritic nickel ores of Gördes region by hydrometallurgical methods under the optimum conditions. Limonitic and nontronitic types of Gö
rdes lateritic nickel ores were used during experiments. Agitative and column leaching experiments at atmospheric pressure were conducted with various parameters
these were duration, temperature and initial sulfuric acid concentration of leach solution. It was shown that in agitative leaching, under the optimum conditions that were determined as 24 hours of leaching at 95°
C with initial sulfuric acid concentration of 192.1 g/L for nontronite and 240.1 g/L for limonite, nickel and cobalt extractions were 96.0% and 63.4% for nontronite
93.1% and 75.0% for limonite, respectively. Overall acid consumptions of ores were calculated as 669 kg H2SO4/ton dry ore for nontronitic type nickel ore and 714 kg H2SO4/ton dry ore for limonitic type nickel ore. Column leaching experiments also showed that nickel and cobalt could be extracted from both ore types by heap leaching. Nontronite type of laterite was found to be more suitable for column leaching by sulfuric acid. In column leaching, the calculated nickel and cobalt extractions were 83.9% and 55.2% for nontronite after 122 days of leaching with 100 g/L sulfuric acid concentration. Acid consumption of nontronite was found to be 462 kg H2SO4/ton dry ore.
4
Faux-Mallet, Marie-Sabine. "Extraction du gallium(iii) en milieu acide : comparaison des methodes d'extraction liquide-liquide et d'echange d'ions sur resines." Paris 6, 1988. http://www.theses.fr/1988PA066234.
Full textAbstract:
Comparaison des avantages et des inconvenients de l'extraction a l'aide de resines et de l'extraction liquide-liquide en vue de preciser leur domaine respectif d'utilisation en hydrometallurgie. Etude de la separation du gallium contenu dans les solutions d'attaque des minerais de zinc. Utilisation de la resine duolite es467 et pour l'extraction liquide-liquide de l'hydroxy-8 quinoleine et d'une alpha-hydroxy-oxime
5
Mwase, James Malumbo. "Hydrometallurgical extraction of platinum group metals from a low-grade ore concentrate." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/8966.
Full textAbstract:
Includes bibliographical references (leaves 143-153).The aim of this study is to investigate the economic and technical feasibility of processing platinum group metals (PGMs) and base metals (BMs) from a low-grade ore concentrate produced in the concentrator plant at Lonmin Pic. The PGMs of particular interest are platinum, palladium, ruthenium and rhodium, while the BMs of interest are copper and nickel. The ore concentrate, as a by-product, represents only 5 % of the total PGM value but as much as 70 % of the total tonnage of material processed in the concentrator plant. Further upgrading this material is not considered a viable route. However, even this low PGM content in the concentrate material accumulates to appreciable value on an annual basis motivating the need to develop alternative methods of extracting value from it. Initial estimates indicate that extraction levels of at least 50 % of the PGMs and 50 % of the BMs would need to be achieved, using low cost hydrometallurgical processes, to make the venture economically viable. These methods would exclude treatment via the smelter and pressure leaching: which are costly. energy intensive and result in leaching of large quantities of non-valuable elements. Previous studies revealed that organic acids had the potential to economically extract the PGMs under alkaline conditions, and BMs under acidic conditions, from various ores and concentrate materials. A literature survey confirmed that certain organic acids can be used to leach metals from ores and concentrates via chemical complexation. It further revealed that other chemical agents. namely cyanide, thiosulphate and bisulphide, were similarly capable of strongly complexing PGMs under various conditions of pH and temperature. The survey also revealed industrially established methods for extracting BMs from low-grade ores and concentrates. Based on this material, this study experimentally evaluated these options with the intent to propose a flowsheet to treat the concentrate material. This was conducted in two phases of experimental work.
6
Gendall, Ian Richard. "The porphyry copper system and the precious metal-gold potential." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1005604.
Full textAbstract:
It has been established that porphyry copper/copper-gold deposits have formed from I Ma to 2 Ga ago. Generally, they are related to the Mesozoic-Cenozoic interval with few reported occurrences from the Palaeozoic or Precambrian. A reason cited is the erosion of these deposits which are often related to convergent plate margins and orogenic belts. Observations of the alteration and mineralisation within and around porphyry copper/copper-gold systems have been included in numerous idealised models. These alteration and mineralisation patterns are dependent on the phases of intrusion, the tectonic setting and rock type, depth of emplacement and relationship to coeval volcanics, physiochemical conditions operative within and surrounding the intrusive and many other mechanical and geochemical conditions. Island arc and cratonic arc/margin deposits are generally considered to be richer in gold than their molybdenum-rich, intra-cratonic counterparts. Metal zonation may occur around these copper/copper-gold deposits, e.g. copper in the core moving out to silver, lead, zinc and gold. This zonation is not always present and gold may occur in the core, intermediate or distal zones. Examples of gold-rich porphyry deposits from British Columbia, Chile and the SW Pacific Island regions suggest gold is closely associated with the potassic-rich zones. Generally these gold-rich zones have greater than 2% magnetite and a high oxygen fugacity is considered to be an important control for gold deposition. High Cl contents within the magma are necessary for gold mobility within the host intrusive centres. Beyond this zone HS₂ becomes an important transporting ligand. Exploration for porphyry copper-gold deposits includes an integrated geological, geophysical and geochemical approach. Petrographic work through to Landsat imagery may be used to determine the chemical conditions of the system, ore association, favourable structural zones and alteration patterns, in order to focus exploration activities.
7
Trenholme, W. J. F. "Metal-organic frameworks for platinum group metal extraction." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32795/.
Full textAbstract:
This Thesis describes the synthesis and characterisation of a variety of functionalised metal-organic frameworks (MOFs). These MOFs have been used for the extraction of platinum group metal (PGM) compounds from aqueous and organic solvents and for the storage of gases such as CO2, CH4 and the C2 hydrocarbons. Chapter 1 contains an introduction to PGM properties and uses with specific focus on the chemical properties which allow for separation of PGMs from base metal compounds and for separation between different PGM compounds. The synthesis and structure prediction of MOFs is then introduced, leading into an overview of the use of functionalised MOFs, especially those used for the encapsulation and extraction of metal ions from solution. General experimental techniques and details are described, as is the theory behind inductively coupled plasma optical emission spectrometry (ICP-OES), the most widely used analytical technique reported in this work. Chapter 2 describes the synthesis of chemically stable amine-functionalised Zr(IV) MOFs; UiO-68-NH2 and UiO-66-NH2, for extraction of PGM anions from aqueous and acidic solutions. ICP-OES was used to show that both materials exhibit close to 100% uptake of PtCl62- when present in just 3.5 equivalents per anion, comparable to the best materials reported for PtCl62- extraction. Furthermore, UiO-66-NH2 exhibited consistently higher PtCl62- uptake from aqueous solutions than four industrially used materials supplied by Johnson Matthey. Back-extraction of PtCl62- was demonstrated simply by heating the doped MOF in 4 M HCl, removing 99% of the PGM while maintaining the phase and crystallinity of UiO-66-NH2. Separation of PdCl62- from PtCl62- from acidic HCl solutions was exhibited by UiO-66-NH2, showing an exceptional selectivity of 20:1 for Pd:Pt from 2 M HCl. Likewise, 100% selectivity for PtCl62- and PdCl62- over CuCl2 and CuSO4 from acidic solutions was demonstrated, even in cases in which Cu was in 100-fold excess. Solid state NMR was employed to confirm the interaction between the framework and the PGM anions, with XPS results suggesting that the encapsulated Pt species within UiO-66-NH2 may be PtCl3(NH2)3 or PtCl4(NH2)2. Chapter 3 describes the synthesis and characterisation of a series of functionalised Cu(II) MOFs, NOTT-151, -155, -125 and -150, for the removal of neutral PGM complexes, Pd(OAc)2, PtCl4 and Rh2(OAc)4, from THF. The design of the MOFs allowed for an investigation into the effect of different topologies (ssa and fof), cage sizes and functional groups (amine, oxamide and methyl) on the uptake of each PGM complex. ICP-OES analysis showed that the MOFs were capable of extracting each PGM complex. The oxamide-functionalised NOTT-125 exhibited the most consistent uptake of Pd(OAc)2 with a maximum capacity of 35 mg g-1 (7 NH(CO)2NH groups per PtCl4). The amine-functionalised NOTT-155 showed the highest uptake of PtCl4, with a maximum capacity of 73 mg g-1 (4 NH2 groups per PtCl4). Uptake of Rh2(OAc)4 was generally low, however NOTT-125 showed a maximum extraction of 87 mg g-1 (3 NH(CO)2NH groups per PGM). The larger pore fof MOFs, NOTT-155 and NOTT-125, were more effective for each extraction than the MOFs of ssa topology, NOTT-151 and NOTT-150. However, of the ssa MOFs, amine-functionalised NOTT-151 was shown to give higher uptake of each PGM than the isostructural methyl-functionalised NOTT-150. This demonstrated the importance of incorporating a functional group capable of coordinating to the metal complex. Chapter 4 introduces the use of a nitrogen-rich triazine core in the synthesis of a variety of organic linkers to prepare MOFs for gas storage applications. The preparation of a novel 3,24-connected Cu(II) MOF of rht topology, denoted NOTT-160, is described and the structure characterised using X-ray crystallography. The material is shown to exhibit good uptake of C2 hydrocarbons with uptake of 128 cc g-1, 115 cc g-1, 110 cc g-1 for C2H2, C2H4, C2H6 respectively at 298 K and 1 bar (this becomes 212 cc g-1, 175 cc g-1 and 201 cc g-1 at 273 K and 1 bar). The selectivities of 79:1 and 70:1 calculated using Henry’s law for the separations of C2H2:CH4 and C2H4:CH4 respectively at 298 K are the third and second highest reported values for a MOF under these conditions. Ideal adsorbed solution theory (IAST) was also employed to calculate and predict these selectivities and shows agreement with the results obtained using Henry’s law. In addition, NOTT-160 shows an exceptional volumetric working capacity for CH4 of 221 cm3 cm-3 at 80 bar and 298 K. This is the second highest working capacity reported for a MOF under these conditions, with the excellent performance attributed to the high porosity and comparatively high crystal density of the material. Chapter 5 contains a summary of the work presented in this thesis.
8
Goveli, Ahmet. "Nickel Extraction From Gordes Laterites By Hydrochloric Acid Leaching." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607738/index.pdf.
Full textAbstract:
Leaching is the most widely used process for extraction of nickel metal from lateritic ores.
In this study, nickel extraction from Manisa-Gördes region laterites by hydrochloric acid leaching is aimed. The mineralogical analysis of sample showed that hematite, goethite, dolomite, quartz and smectite are the main minerals in the ore. Attrition scrubbing, cycloning and magnetic separation with permroll were used as preconcentration processes but results were unsatisfactory. HCl leaching experiments were conducted both at room temperature and at elevated temperatures. The effects of various parameters such as leaching duration, particle size, concentration of HCl, pulp density, Cl- concentration and temperature on nickel recovery were examined. The results showed that under the optimised leaching conditions (particle size: 100 % -1 mm, HCl concentration: 3 N, leaching duration: 3 hours, leaching temperature: 100 oC, pulp density: 1/30 solid to liquid ratio by volume) it was possible to extract 87.26 % of nickel in the ore.
9
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.
Full textAbstract:
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
10
Escudero, Castejon Lidia. "Novel reductive alkali roasting for Cr6+-free extraction of Cr2O3 from chromite ores." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/22530/.
Full textAbstract:
Chromite ore is the raw material used in the manufacturing of ferrochromium, which is an important metallurgical product employed in the stainless-steel industry. Chromium-based chemicals have also a wide range of applications, including pigments industry, leather tanning processes and surface treatments. The production of chromium chemicals is based on the alkali roasting of chromite ore in oxidising atmosphere in order to extract chromium as water soluble alkali chromate (Na2CrO4, K2CrO4). The main drawback of this process is the inevitable generation of a hazardous processing waste containing highly toxic hexavalent chromium. This residue needs to be landfilled and presents a serious environmental concern due to the lethal effects of Cr6+ in flora and fauna. With the purpose of avoiding the formation of highly toxic Cr6+, a novel process for extraction of Cr2O3 based on the carbothermal reduction of chromite ore in the presence of alkali, is proposed. During the reductive alkali roasting (or alkali reduction) of chromite, iron is reduced to metallic form and chromium reacts with Na2O to form sodium chromite (NaCrO2). Reduced samples are subjected to wet magnetic separation obtaining a magnetic fraction rich in metallic iron and a non-magnetic fraction which contains the NaCrO2 formed. The non-magnetic fraction is further treated to extract a Cr2O3-rich product, which may be used as raw material for manufacturing of high grade Cr2O3. 85.6% Cr2O3 recovery was achieved after chromite reduction with Na2CO3 and activated charcoal (1050oC, 2.5 hours), followed by magnetic separation and leaching of the non-magnetic fraction with water and 0.5 M sulfuric acid. A final 83.6% Cr2O3-rich product was obtained. This process does not generate toxic waste in gas, liquid or solid form, as the formation of Cr6+ is completely avoided by maintaining chromium in (3+)-state at all stages of the process. The fundamentals of the different stages of the process were investigated, including the thermodynamics, kinetics and physico-chemistry of the reduction reaction as a function of the process parameters. Mass balance and energy balance, and the environmental aspects of the process were also studied based on the proposed flowsheet of the reductive alkali roasting process.
11
Murahwi, Charley Zvinaiye. "The geology of the Unki platinum-base metal deposit, Selukwe subchamber, great dyke, Zimbabwe." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005574.
Full textAbstract:
This thesis focuses on platinu'm group element (PGE) mineralization in the Unki Section of the Selukwe Subchamber of the Great Dyke (Zimbabwe), and is based on drill hole intersections and underground and surface exposures of the Main Sulphide Zone (MSZ) which hosts significant concentrations of PGE. The petrological and geochemical data presented are part of a broader study currently underway and the present are restricted to the 2m section of the PGE-rich MSZ encountered in drill hole MR126. The PGE-rich MSZ at Unki is unique in having a shear, locally referred to as the Footwall Shear, developed at or close to its base . It is however, similar to the other PGE occurrences on the Great Dyke (MSZ) in having its hanging-wall restricted to within 1m of the websterite/bronzitite contact. Slight axial tilting to t he west is indicated by steeper dips on the eastern flank. The sulphide concentration wit hin the MSZ can be used as a rough guide to the PGE-rich zone, but is not sufficiently precise to be used in stope control. The visual identification of the potentially mineable zone remains a problem that is unlikely to be solved. Based on petrological evidence, the bulk of the sulphides with which the PGE are associated, are cumulus in status. This provides unequivocal evidence for an orthomagmatic origin of the MSZ. The dominant platinum group mineral (PGM) phase is the Arsenide/Sperrylite group which is most commonly found at the contact zones between base metal sulphides (BMS) and gangue. The PGM range up to 90 ~m in length. Geochemical evidence from the analyses of cumulate orthopyroxenes through the 2m PGE-rich MSZ interval at Unki reveals a trend of arked Fe enrichment upwards which corresponds to an enrichment in sulphide. This indicates that precipitation of sulphide was caused by fractionation with lowering of temperature in the magma. The Fe enrichment is followed by a reversal in Mg# of orthopyroxene which corresponds to the decrease in sulphide content, suggest i ng that the termination of the PGE-rich MSZ was due to an increase in temperature associated with an influx of new magma. Coupled with these magmatic events are a complex interplay of chemical and physical processes occurring at a critical stage in the overall fractionation of the Great Dyke magma chamber. The overall persistence and continuity of t he PGE zone as observed in the Unki area is consistent with the inferred orthomagmatic origin of the mineralization
12
Mwase, James Malumbo. "An investigation of cyanide-based heap leaching for extracting precious metals from Platreef ore." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/28335.
Full textAbstract:
Cyanide heap leaching had been proposed as an alternative to the classic crush-mill-loatsmelt-refine route for processing platinum group metals (PGMs) from the Platreef ore body. Overall the process includes two stages of leaching. The first stage involves the thermophile bioleaching of the base metal (BM) sulphide minerals and acts as a form of pre-treatment to oxidise sulphur compounds and recovery valuable metals such as Cu, Ni and Co. The second stage focuses on cyanide-based heap leaching for the recovery of precious metals (PGMs +gold) from the solid residue of the first stage. Exploration and optimisation of this second stage in the context of a whole ore Platreef material is the focus of the present study. The first part of the study used a series of laboratory tests simulating heap leaching, conducted on coarse ore. The initial tests showed high recoveries of base metals (Cu, Ni and Co) could be achieved in a pre-treatment bioleach process, while in the second stage cyanide leach high levels of Pd and Au were extracted, but only 58% of the Pt after 60 days from the whole ore. It was observed that during the 60 day leaching period the rate of Pt leaching decreased considerably after 35 days. From the trajectory of the Pt leach curve from the 35 day mark onwards, it was observed that the leaching would not cease even after 60 days but would likely proceed but at that slow pace which indicated further Pt extraction would not be commercially viable in the long run. Mineralogical analysis has indicated that a significant component of the Pt in the ore is in the form a mineral sperrylite (PtAs2), which appears to leach slowly in cyanide as compared to other mineral forms such as certain tellurides and sulphides in the ore. Subsequently, efforts were made to investigate methods to improve the second stage leach process, in terms of Pt leaching from sperrylite, through further work on a pure mineral sample. The key focus was on finding a suitable oxidant that can be used in cyanide solutions, from among air, oxygen and ferricyanide, to facilitate the dissolution. Various tests using sperrylite mineral samples micronized to 5 μm in batch stirred tank reactors (BSTR) at 50°C were conducted. It was found that a combination of ferricyanide with cyanide extracted as much as 16 times more Pt than tests using only cyanide. The presence of air or pure oxygen did not contribute significantly to the amount of Pt leached in this system and made no difference at all in the leach tests using only cyanide. Further bench-scale studies focused on characterising the leaching mechanism of sperrylite in cyanide-ferricyanide solutions. It was found that the reaction, after proceeding at appreciable rates initially, tended to cease after 1 day, indicating some form of surface passivation, tentatively related to some form of solution equilibrium being achieved. However after re-leaching the sample with fresh solution, the Pt dissolution improved tremendously. This was further investigated in continuous leaching of a sample of the mineral using a small bed of sperrylite fixed in mini-columns. The results from the minicolumns showed the same leaching pattern as the experiments using BSTRs. It was eventually revealed that a suitable wash of the sperrylite sample using water removes the inhibiting layer and facilitates further and improved leaching. Unlike the cyanide-only system where the passivation was attributed to As build-up at the surface, in the cyanide-ferricyanide system it was attributed to adsorption of unknown reaction products on the mineral surface. Residual samples from batch leach experiments were analysed using X-ray photoelectron spectroscopy and showed samples from the cyanide-ferricyanide tests had less As on the surface than the untreated sample and the sample leached in cyanide. To some degree this supported the hypothesis that Pt leaching is eventually hindered by As passivation in a cyanide system. The presence of ferricyanide serves to oxidise As and thereby release more Pt in solution. Additionally, electrochemical techniques using a sperrylite electrode were employed to further understand the redox reaction under varying oxidation conditions. While the tests indicated a weak current under mildly oxidising conditions in cyanide solutions, this became rapidly limiting at potentials expected in a ferricyanide solution, indicating a form of surface passivation. An attempt was made to determine the number of electrons transferred during Pt dissolution to indicate the primary reaction mechanism through a long-term test held at constant potential, but dissolution rates were too small to be conclusive. Hence the study has shown that the cyanide-based heap leaching of PGMs from Platreef type ores is feasible in principle, but the dissolution of PtAs2 remains limited. While the study has given valuable pointers to understanding this observation, the conclusion is that PtAs2 is refractory in the given context and further development of this process remains promising through further investigation into the use of the cyanide-ferricyanide combination.
13
Pornsinlapatip, Pornpun. "Flow-injection solvent extraction of metal chelates." Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284394.
Full text
14
Ge, Xinlei. "Extraction of Metal Values : Thermodynamics of Electrolyte Solutions and Molten Salts Extraction Process." Doctoral thesis, Stockholm : Skolan för industriell teknik och management, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10638.
Full text
15
Healy, Mary Rose. "Outer-sphere interactions in metal solvent extraction systems." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28712.
Full textAbstract:
This work aims to define the modes of action of a series of metal extraction ligands with particular focus on how these depend on the formation of supramolecular assemblies. Though solvent extraction processes are well established industrially often the understanding, particularly of the metal coordination chemistry, is less so. A greater understanding of a variety of solvent extraction systems can lead to the development of stronger and more specific extractants. Chapter 2 examines the role of inter-ligand interactions in the extraction of copper by phenolic oximes and pyrazoles. Computational methods are used to understand the importance of inter-ligand outer-sphere interactions in square-planar copper complexes. It is shown that functionalisation at different positions on the phenol ring can either stabilise or destabilise the copper complex and it is possible to predict the strength of extractants from DFT calculations. Substitution ortho to the phenolic oxygen in the oximes and pyrazoles can have a major effect of enhancing the strength of extractants by “buttressing” the H-bonding between ligands. However, in the amino-methyl substituted oximes buttressing is so strong that is has an adverse effect on complex formation. Crystal structures are confirmed by both ENDOR EPR spectroscopy and DFT structures. A series of 6-X-4-methyl-2-(5-alkyl-1H-pyrazol-3-yl)- phenols (X = H, OMe, Br and NO2) was synthesised and characterised (X = H, OMe, Br and NO2) and the copper extractant found to be 6-nitro-4-methyl-2-(5-(1,3,5-tri-methyl-pentyl)- 1H-pyrazol-3-yl)-phenol extractants. Computational DFT studies in the gas phase were carried out to calculate the formation energies of analogous phenolic pyrazole copper complexes. The predicted order of these energies followed the same trend shown by experimental solvent extraction studies. Studies also showed that substitution can affect not only complex stability through inter-ligand interactions through hydrogen bonding in the outer-sphere but also the strength of metal-ligand bonds. Chapter 3 looks at synergistic solvent extraction systems: where more than one extractant works together to provide additional strength and selectivity. Combinations of neutral N and O donor ligands with carboxylic, phosphinic and sulfonic acids were studied by solvent extraction, crystallographic and computational methods. Crystal structures and DFT-optimised structures show that ligands and acid form pseudo-tridentate ligands where both the neutral ligand and the deprotonated acid are coordinated directly to the metal centre with inter-ligand hydrogen bonding allowing for a more flexible backbone than a classic tridentate system. Although synergistic extractions systems often utilise carboxylic acids many of the structures show the similarities with systems containing phosphinic acids and it was shown experimentally that some extraction systems show greater synergism with phosphinic than carboxylic acid in the recovery of nickel. Chapter 4 deals with the extraction of molybdenum with commercial phosphinic acid extractant Cyanex 600. The propensity for molybdenum to form oxo clusters in aqueous solutions and the influence pH in both the speciation of the Mo species and extraction conditions contributes to a complex extraction profile. The pH dependence of extraction shows that different mechanisms operate at low (pH < 0) and high (pH > 0) pH. The extraction curve shows a conventional S-curve between pH 0 and 1.5 and slope analysis within this pH range gives a value very close to two but identification of structures which match this profile is complex. Maximum pH extraction is see at ~ pH 1.5. ESMS studies identified very similar species in the organic phase despite the variation seen in the S-curve. A survey of the structures of metal complexes of phosphinate ligands suggests that molybdenum-phosphinate complexes can often form cubane-like structure and negative ion ESMS data supports the concept of cluster formation in the organic phase. A common feature of the spectra are tetra- tri- and bi-metal- oxo species and spectra show a large number of peaks. It is very probable that the extraction of molybdenum(VI) with phosphinic acids is a dynamic system as extraction is influenced by the molybdenum speciation in the aqueous phase which is in turn influenced by both the pH and the molybdenum concentration both of which change over the course of a conventional extraction.
16
Roy, Mimi. "A detailed sequential extraction study of selenium in coal and coal-associated strata from a coal mine in West Virginia." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4431.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains x, 93 p. : ill. (some col.), map (part col.). Vita. Includes abstract. Includes bibliographical references (p. 75-78).
17
Davis, Lauren Elizabeth. "Extraction : one woman's epilepsy." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/3281.
Full text
18
Brown, Stanley. "Heavy metal detoxification of sewage sludge." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302700.
Full text
19
Chamupathi, Virittamulla Gamage. "Role of the interface in metal solvent extraction kinetics." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184256.
Full textAbstract:
Interfacially active reagents are utilized in metal solvent extraction processes and it is therefore important to understand the role of the liquid-liquid interface in the study of the kinetics and equilibria of extraction. The diffusion problems encountered in the traditional apparatus were overcome by using a high speed stirring apparatus. The microporous teflon membrane phase separator permitted more accurate measurements of interfacial areas, characterization of extraction kinetics of metal chelates, and a greater understanding of the phase separation mechanism. In contrast to the neutral ligands, the anionic ligand of dithizones and substituted dithizones showed significant interfacial adsorption at the chloroform/water interface as monitored spectro-photometrically. Equilibrium studies on p-halodithizones indicated that the adsorption constant increased as the substituent was altered from chloro to bromo to iodo, and with the distribution ratio of the ligand. Kinetic studies on dithizone and p-iododithizone with Ni(II) and Zn(II) indicated that the extent of participation of the interface in solvent extraction kinetics of these metal ions is dictated by the interfacial activity of the extractant and the mechanisms of the rate limiting step in the bulk aqueous and interfacial regions.
20
Boodhoo, Kishore. "Functionalised cyclodextrins for multi-metallic assemblies : towards metal extraction." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273554.
Full text
21
Ca, Diep Vu. "NANOSTRUCTURED ASSEMBLIES FOR SOLID PHASE EXTRACTION OF METAL IONS." Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1107552000.
Full text
22
Barker, Michael H. "Electrochemistry at liquid/liquid interfaces for metal ion extraction." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367192.
Full textAbstract:
The aim of this project was to produce a selective extraction system for the separation of precious metal ions from waste electrolyte streams utilising liquid/liquid electrochemical techniques. During the course of this project the work partitioned into three different aspects of charge transfer: electron transfer, ion transfer and membrane studies. Some fundamental physicochemical properties of liquid/liquid systems were explored. For electron transfer reactions the dependence of the rate of electron transfer on supporting electrolyte concentration in the organic phase for the water/1,2-DCE interface was measured using the technique of interfacial electrochemical impedance spectroscopy. No dependence of the rate of electron transfer on the concentration of the supporting electrolyte in the organic phase was observed. The effect of the solvent on the kinetics of electron transfer has also been examined. The results show that the rate does not follow the expected Marcusian dependence. Several solvents previously unused for liquid/liquid studies have been screened; one solvent in particular, 1,2-difluorobenzene, shows great promise for future work. The ion transfer studies show that platinates can be separated under potential control across the water/1,2-DCE and the water/methyl isobutyl ketone interfaces. Ion transfer and separation of chloroaurate and chloroplatinates have been discussed on the basis of the Galvani potential of ion transfer. Evidence of ion pairing between the platinates and the organic supporting electrolyte cation was found. The thermodynamics of the platinate transfer have also been explored and, in collaboration with Dr Robert Deeth, preliminary density functional theory calculations have been performed to explain the experimental results in terms of a model accounting for the surface charge density of the platinates. This goes further than the classical Born approach of treating the ion as a hard sphere of charge in a dielectric continuum. The ion transfer across membranes has been studied and the results were applied to single and dual membrane supported liquid/liquid interfaces for separating platinates from base metals. [PtCl6]2- transfer across a supported liquid membrane was demonstrated. The scale–up experiments were not successful, but if certain points can be addressed, it may be possible for future studies to build on what has been achieved here. Additional to the three traditional sections of liquid/liquid work, a method of preparing gold nanoparticles has been found using ketones as the reducing agent at the water/ketone interface. The formation of gold mirrors has been observed and nanoparticles have been isolated and characterised.
23
Smith, Kate Jennifer. "Ditopic ligands for the extraction of divalent metal salts." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/12982.
Full textAbstract:
This thesis extends earlier work at the University of Edinburgh aimed at opening up new flowsheets for the hydrometallurgical recovery of base metals using tetradentate ligands which are capable of transporting metal salts {both a metal cation and its attendant anion(s)}. Prototypes were based on salicylaldimine derivatives of diamines, “salen” ligands in which coordination of a metal dication releases the two phenolic protons which are captured by pendant secondary amine groups generating a preorganised dicationic binding site for the anion(s). The thesis initially deals with the design, synthesis and evaluation of ligands to improve the strength, selectivity and speed of binding of nickel(II) sulfate by incorporating two additional donors in the salen unit to generate N2X2O22- binding sites for the nickel yielding pseudo octahedral complexes. The ligands N,N or O,O or S,S o-aminophenyl-substituted 1,2-diaminoethane, 1,2-dioxaethane, 1,3-dioxapropane or 1,2-diethioethane were also used in a screening study with some other divalent metal salts (calcium, cobalt, copper, magnesium, manganese and zinc) commonly found in the feed solutions in commercial processes. Chapter two deals with the nickel(II) coordination chemistry of a series of sexadentate (N2X2O22-) ligands. Nickel-ligand-anion complexes have been synthesised for sulfate, nitrate and chloride salts and neutral nickel-ligand complexes have been made. Crystal structures of complexes all contain the same isomer which has a planar mer arrangement of the salicylaldimato XNO- units. A “nickel only” complex for an X2N2O22- ligand with pendent piperidine groups shows that these could provide a cavity to encapsulate a single sulfate anion. All the ligands were found to be very weak extractants and showed slow complexation kinetics and phase transfer of nickel sulfate. The synthesis and characterisation of a series of tridentate ligands related to the sexadentate ligands, with NXO- binding sites, are reported in chapter three. In theory these could form complexes with a ligand: nickel ratio of 2:1, with a more nearly “ideal” octahedral donor set. Solid state structures of the ligands show them to be pre-organised with an approximately 90° X˙˙˙N˙˙˙O angle. Nickel complexes have been synthesised for sulfate, chloride and acetate salts. Analysis indicates that complexes with ligand: nickel: dianion ratios of 2:1:1 were formed. The tridentate ligands were found to be very weak extractants for nickel sulfate. Chapter four describes the screening of the potentially sexadentate N2X2O22-, tridentate NXO- and the tetradentate “salen” ligands N2O22- in which the complexation and phase transfer of calcium(II), cobalt(II), copper(II), magnesium(II), manganese(II), nickel(II) and zinc(II) sulfates and chlorides were studied.
24
Rashid, Salman Ghanem. "Studies on copper extraction with hydroxyoxime extractants for the design of hollow fibre membrane based extraction processes." Thesis, University of South Wales, 1999. https://pure.southwales.ac.uk/en/studentthesis/studies-on-copper-extraction-with-hydroxyoxime-extractants-for-the-design-of-hollow-fibre-membrane-based-extraction-processes(7e631b77-71e2-4d6e-8c03-4636d42f9f69).html.
Full textAbstract:
This work has included a review of the most relevant aspects of measurement techniques and mathematical models proposed in the literature to assess the equilibrium and mass transfer data of metal extraction by the use of chelating agents. The limitations of these techniques and models have been highlighted. Three chelating extractants diluted in EscaidllO were used to study the extraction equilibrium of copper. The extractants are 5-nonylacetophenone oxime (LIX84®), 5- dodeylsalicylaldoxime (LIX860®) and 50/50 v/v mixture of both oximes (LIX984®). The copper concentration changes in the aqueous and the organic phases were monitored by using atomic absorption spectrophotometer. Two mathematical models (a chemical model and a semi-empirical model) have been developed in this study to predict the equilibrium data of copper sulfate/hydroxyoxime system. The chemical model was found to fit all the three equilibrium systems (CuSO4/LIX84®, LIX860®and LIX984®) equally. The semi-empirical model based on Freundlich's adsorption equation was also found to fit the three systems but with less accuracy. The mass transfer characteristics and properties of copper extraction and recovery from an aqueous solution using LIX984® were studied using dispersion-based (rising drops) and dispersion-free techniques. In the dispersion-based technique the organic phase was dispersed in form of drops at the tip of hypodermic needle while the aqueous solution was used as a continuous phase. The extraction process was carried out in four different height columns under wide range of conditions. The effects of the columns' height, the dispersed and the continuous phases concentrations on the metal rate of mass transfer were investigated. It has been found in that the metal's rate of mass transfer and system's overall mass transfer coefficient have remained constant in all four columns. A model utilising the two-film theory, some of the dimensionless groups and the experimental results has been proposed in this work to calculate the local mass transfer coefficients in the dispersed phase and the continuous phase. The overall mass transfer coefficient and the calculated local coefficients were used to account for the reaction rate constant at the interface from the sum of the individual resistances to mass transfer. A dispersion-free technique consisting of a microporous hollow fibre module was used in this study to examine the mass transfer properties of the extraction and stripping processes of copper across an immobilised interface system. The extraction and re-extraction (stripping) processes in this system were conducted under a wide range of operating conditions and produced satisfactory results. In general it has been found that counter current flow arrangement gave higher concentration driving forces which were reflected in form higher metal concentrations at the extract phase. A generalised mathematical model was developed in this study which utilised Wilson's method, the experimental data, some dimensionless groups and the two-film theory to account for local resistances and predict the system's overall mass transfer coefficient. A correlation was established first to calculate mass transfer coefficients using a form of Leveque's equation which relates the two phase's physical properties and the system's parameters. The membrane mass transfer coefficient was calculated from the structural properties of the membrane material. While the resistance at the reaction interface was calculated under set of experimental conditions. The individual coefficients were then used to predict the overall mass transfer coefficient under any set of conditions by using the aditivity approach of the individual resistances to mass transfer. However, further checks and investigations are necessary to validate this model over variety of extraction systems and membrane configurations.
25
Lin, Qingyang. "Use of X-ray computed microtomography to measure the leaching behaviour of metal sulphide ores." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/25274.
Full textAbstract:
Heap leaching is an important hydrometallurgical method to extract valuable metals from ores, especially low grade ores. The main disadvantages of heap leaching are the long processing time and low extraction efficiencies. Currently, a major barrier in fully understanding the leaching process is the study of the mass transport and surface chemistry at individual ore particle and mineral grain scale. This thesis describes a combined experimental and modelling approach to visualise, quantify and predict the leach behaviour based on X-ray Computed Microtomography (XMT, or micro-CT). An automatic image processing package was developed to process the 3D volume data. Individual ore particles as well as individual mineral grains can be tracked using a centroid tracking algorithm and a novel fast tracking algorithm respectively. The systematic and random errors and uncertainties in the image volume measurements were quantified. It was found that both the systematic and random errors are a strong function of the grain size relative to the voxel size. The random error can be reduced by combining the results from either multiple scans of the same object or scans of multiple similar objects while the systematic error can be eliminated by using volume standards. The leach performance for a leaching column was quantified at different scales and it was found that the leach behaviour and its variability were difficult to quantify at large scales (column and individual ore particle scale), but can be quantified at mineral grain scale by using a novel statistical analysis method. The tracked grains were divided into different size-distance categories to analyse the average leach performance and the variation for each category. Both grain size and distance dependencies were observed. The size dependency is more dominant at the early stage of leaching whereas the distance dependency can significantly influence the ultimate recovery. A method for using the data to estimate the variability in the in-situ surface kinetics was also developed. A model for simulating the grain dissolution and the resultant kinetics based directly on XMT based 3D volume is introduced. The simulations were able to accurately predict both the overall leaching trends, as well as the leaching behaviour of mineral grains in classes based on their size and distance to the particle surface.
26
Ozdemir, Veysel. "Hydrometallurgical Extraction Of Nickel And Cobalt From Caldag Lateritic Ore." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607777/index.pdf.
Full textAbstract:
In this study, an attempt has been made to hydrometallurgical extraction of cobalt and nickel by atmospheric pressure sulphuric acid leaching and a pug-roast-leach process using two stage roasting for lateritic ore. The ore used in the study was obtained from Çaldag Lateritic Ore, Manisa, Turkey. The metal contents of the ore are 2.1 % Ni, 0.12 % Co, 32.45 % Fe, 1.01 % Mn, 2.58 % Cr, 0.78 % Mg and 1.01 % Al. The reserve of lateritic ore deposit is approximately 40 million tonnes. In the study, first sulphuric acid leaching was applied at atmospheric pressure for leaching the Ç
aldag lateritic ore. The effect of various parameters, such as leaching time, leaching temperature, particle size, pulp density and acid strength on Ni and Co extractions were determined. By leaching at 80oC for 40 wt % H2SO4 addition of ore, 1/3 pulp density, Ni and Co extractions were found 44.49 % and 53.03 % respectively, yielded a pregnant solution containing 3.11 g/L Ni and 0.12 g/L Co. But the result of atmospheric pressure sulphuric acid leaching was considered insufficient from the recovery point of view. In the pug-roast-leach process, which is consisted of a two stage roasting followed by water leaching, decomposition temperature differences of sulphates of cobalt, nickel and iron are exploited. In this process, amount of acid, sulphatization and decomposition temperature, sulphatization and decomposition time, leaching temperature and time, solid/liquid ratio, and the effect of water addition during pugging were optimized. Under the optimized conditions (sulphuric acid: 25 wt % of ore
moisture: 20 wt % of ore
sulphatization temperature: 450oC
sulphatization time: 30 minutes
decomposition temperature: 700oC
decomposition time: 60 minutes
leaching temperature: 70oC
leaching time: 30 minutes and solid-liquid ratio: 1/4 by weight), Co and Ni extractions were found 91.4 and 84.4 percent, respectively. A pregnant solution containing 3.084 g/L Ni and 0.185 g/L Co was obtained. These results were considered sufficient for the leaching of lateritic nickel ores.
27
Hastings, Matthew H. "Relationship of base-metal skarn mineralization to Carlin-type gold mineralization at the Archimedes gold deposit, Eureka, Nevada." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460760.
Full text
28
Premaratne, Wijendra A. P. Jeewantha. "Mineral chemistry and metal extraction of Sri Lanka beach sands." Thesis, University of Birmingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404128.
Full text
29
Mead, D. A. "Investigation of the supported liquid membrane process for metal extraction." Thesis, University of Hertfordshire, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376472.
Full text
30
Doidge, Euan Douglas. "Designing reagents for the solvent extraction of critical metal resources." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31070.
Full textAbstract:
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.
31
Tucker, Kate Louise. "Heavy metal extraction using advanced liquid-liquid style partitioning systems." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/heavy-metal-extraction-using-advanced-liquid--liquid-style-partitioning-systems(6a238cb4-94cf-4fa8-bffe-d1a1b70adaa6).html.
Full textAbstract:
Understanding the behaviour of heavy metals involved in the nuclear fuel cycle is of paramount importance to the reprocessing and storage of spent nuclear fuel. These studies have attempted to obtain a greater understanding of the fundamental chemistry of these systems, by investigating extraction performance and speciation in current (PUREX) and proposed (GANEX) extraction processes. Various complexes have been shown to exist in the post-extracted organic fraction of the systems analysed. For Zr(IV), U(VI) and Np(VI) separated from aqueous nitric and hydrochloric using TBP, the complexes [Zr(NO3/Cl)4(TBP)4], [UO2(NO3/Cl)2(TBP)2] and [NpO2(NO3/Cl)2(TBP)2] formed, respectively. For Zr(IV) separated from aqueous mixtures of HNO3 and HCl at equal concentration, a preference was shown to [Zr(Cl)4(TBP)4] over the analogous nitrate complex. For U(VI) separated from aqueous mixtures of HNO3 and HCl, a preference was shown to [UO2(Cl)2(TBP)2], even at high aqueous nitrate concentrations. NMR data for Pu(IV) separated from aqueous HNO3, HCl and mixtures of both, using TBP were presented, where possible complexation was observed. It is thought that [Pu(NO3)4(TBP)4] or [PuCl4(TBP)4] species existed within the organic fraction for Pu(IV) separated from aqueous HNO3 and HCl, respectively. These systems showed high distribution ratios where an increase was observed with increasing aqueous acid concentration overall. Distribution ratio data were presented for the lanthanide series separated from aqueous nitric acid, using the proposed GANEX solvent system(s). The lanthanides analysed showed an increase in distribution ratio with increasing aqueous nitric acid concentration and with increasing TODGA concentration in the organic fraction. Heavier lanthanides were observed to give higher distribution ratios overall. The best distribution ratios were observed for lanthanides separated using 0.2 M TODGA with 1-octanol (5 % by volume) over the nitric acid concentration range analysed. For lanthanides separated using 0.5 M DMDOHEMA, an optimum distribution ratio was observed at around 6 M aqueous nitric acid concentration. The distribution ratio data for lanthanides separated from a range of DMDOHEMA concentrations, were observed to increase with increasing organic DMDOHEMA concentration. The distribution ratios observed for isotopes of Np, Am, Eu and Pu separated using 0.2 M TODGA, increased with increasing aqueous nitric acid concentration. The same trend was observed for the aforementioned isotopes separated using 0.5 M DMDOHEMA. However, pertechnetate separated using 0.2 M TODGA from aqueous nitric acid, showed a decrease in the distribution ratios observed over the acid concentration range analysed. This was contrary to pertechnetate separated from aqueous nitric acid using 0.5 M DMDOHEMA, where a small increase in distribution ratio was observed over the concentration range analysed. For Np(VI) separated from some proposed GANEX solvents, the 0.2 M TODGA/0.5 DMDOHEMA combination gave the best distribution of neptunium into the organic fraction. For Np(VI) separated using 0.5 M DMDOHEMA, the complex [Np(DMDOHEMA)2(NO3)4] was observed. Additional attempts to analyse Np(VI) behaviour under GANEX style conditions via EXAFS, were not successful due to immediate reduction of the Np(VI) on the beam line.
32
Crane, Martin John, University of Western Sydney, of Science Technology and Environment College, and of Science Food and Horticulture School. "Geochemical studies of selected base metal minerals from the supergene zone." THESIS_CSTE_SFH_Crane_M.xml, 2001. http://handle.uws.edu.au:8081/1959.7/232.
Full textAbstract:
Acid leaching of different natural chrysocolla samples under ambient conditions demonstrated that the chemical and chrystallographic inhomogenity significantly affects the rate and that it is virtually impossible to use the mineral as a model for the kinetics of hydrometallurgical processing of copper ores.Dissolution experiments, stability diagrams,and X-ray powder diffraction studies are undertaken and studied in this research and results are given.It is found that a complete solid solution series exists in Nature with most tungstenian wulfenites and molybdenum stolzites containing a range of compositions. The first occurrence of a molybdenum stolzite from Broken Hill, Australia, which also contains small amounts of chromium is noted.Raman microprobe spectroscopy has proven to be a very quick and effective non-destructive method for semi-quantitative analysis of the wulfenite-stolzite and powellite-scheelite solid-solution series and in detecting very small amounts of substituted chromate in wulfenite, stolzite and anglesiteDoctor of Philosophy (PhD)
33
Heckley, Philip Scott. "Extraction and separation of cobalt from acidic nickel laterite leach solutions using electrostatic pseudo liquid membrane (ESPLIM)." Curtin University of Technology, Western Australian School of Mines, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14124.
Full textAbstract:
Approximately 70% of the western world's known nickel reserves are contained in laterite ores, but only 30% of the world's nickel production comes from these ores. This is due to the lack of economically viable technology to extract the nickel from these ores. However, recent advances in pressure acid leaching technology have resulted in new commercial attempts to extract nickel and its valuable by-product, cobalt, from laterite ores. The commissioning of three nickel laterite projects in Western Australia in the late 1990s represents the first of these new generation nickel operations, with several other projects; in Australia and overseas, in various stages of development. Unfortunately, several technical issues have hindered full production in these new refineries. Some of these problems are directly attributable to the mixer-settler contactors used in the solvent extraction process. This has highlighted a need to develop alternative contactors for industrial use. Electrostatic Pseudo Liquid Membrane (ESPLIM) is an alternative, novel technique to conduct the solvent extraction process. It combines the basic principles of solvent extraction, liquid membrane and electrostatic dispersion into a simple, compact reactor that utilises many advantages of each technique. The aim of this study w as to develop a method of extracting and separating cobalt from an acidic nickel laterite leach solution using ESPLIM. Bench scale tests using synthetic and actual leach solutions have shown that: the design and construction materials of the baffle plate and electrodes have a significant effect on the performance of the reactor; an AC power supply provided better droplet dispersion than a DC power supply; an increase in the applied electric field strength above a critical value resulted in a decrease in the aqueous droplet size and an increase in residence tune.These effects increased the extraction efficiency and the concentration of the loaded strip solution. However, further increases in applied electric field strength decreased efficiency due to excessive levels of swelling and leakage; the known extraction isotherms for cobalt and nickel apply in the ESPLIM technique; salts of soluble organic acids influence extraction efficiency by changing the aqueous pH and interfacial tension; the use of ammonia was found to be effective as a replacement for salts of soluble organic acids; the ESPLIM reactor can cope with large changes in the flow rates of both feed and strip solutions. However, an increase in the feed flow rate should be accompanied by a relative increase in the ship flow rate to maintain high extraction efficiencies; the baffle design has a significant impact on the levels of swelling and leakage; provided the electrostatic field strength is maintained and flow rates are increased proportionately to the size of the reactor, no significant scale-up issues were observed, indicating that the data generated in bench scale studies could be applied to plant scale contactors. The optimum conditions, devised as a result of this investigation, to extract cobalt from an acidic nickel laterite leach solution using the ESPLIM technique are as follows: an applied electric field strength of 5.5 kV/cm. a raffinate pH of 5.5, a solvent containing 10% Cyanex 272 with 5% TBP in Solvent HF diluent, a feed to strip flow ratio of approximately 5 and a 1 M H[subscript]2S0[subscript]4 strip solution. At these conditions, almost complete cobalt extraction is achieved after only two extraction stages. A comparable extraction using conventional mixer-settlers could only be achieved after five stages.
34
Khalesi, Mohammad Reza. "Integrated modeling of grinding, liberation and leaching of gold ores." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27466/27466.pdf.
Full text
35
Jabbour, Rabih Elie. "Characterization of selected immobilized metal-ions using solid phase extraction sorbents." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282773.
Full textAbstract:
Solid phase extraction (SPE) has been developed as an alternative to liquid-liquid extraction (LLE) in the sample preparation process. The advantages of SPE over LLE are that it is a more useful, reliable tool for sample preparation, which offers greater selectivity. The selectivity of an SPE sorbent is vital for the isolation of analyte from a biological matrix containing a myriad of interferences. The use of conventional ion exchange SPE for such an extraction process might not be adequate due to the adverse effects of interfering ions. Metals immobilized on various modified silicas were investigated to determine if the addition of metals improved selectivity. The selectivity of these sorbents was studied by the extraction of analytes from high ionic strength matrices. Extraction selectivity was found to depend on different factors, including the type of bonded species, metal ions used and the analytes, counter ions, sample pH and elution solvent composition. Utilizing coordination complexation between analytes and immobilized metal ions, particularly when different phases are stacked, can increase selectivity for a particular analyte. Metals immobilized by ionic exchange sorbents were observed to retain analytes of tridentate chelation capability more than immobilized metals on bonded chelators. However, bonded chelators were observed to be advantageous because they more strongly retained metal ions, relative to ionic exchangers. The interactions of immobilized silver ions with unsaturated molecules utilizing SPE were investigated. Retention of silver ions was found dependent on the nature of bonded phase. The silver ions immobilized by coordination interactions showed weaker retention than silver immobilized by ionic interactions. Retention of alkenes by silver was found to have higher flow dependence, as compared to ionic exchange or ligand exchange processes. Retention of analytes was observed to depend on a variety of factors, including the type of bonded phase used for silver immobilization, the composition of the elution solvent, steric factors, the degree of unsaturation, the geometry and position of the double bonds of the analyte molecules. Extraction selectivity for geometrical isomers decreased when silver ions were immobilized by long chain cation exchangers versus those on conventional short chain cation exchangers.
36
Galbraith, Stuart G. "Ditopic ligands for the selective solvent extraction of transition metal sulfates." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/10911.
Full textAbstract:
The thesis considers the development of new reagents which could transport transition metal salts in extractive hydrometallurgy and addresses the ligand design features which are needed to control the strength and selectivity of binding of both a particular metal cation and its attendant anions(s). Extractive metallurgy of base metals is surveyed in chapter 1 and suggests that more efficient recovery processes are needed. One new approach, which could lead to much better materials balances in many cases, is to use hydrometallurgical techniques which involve co-extraction and transport of metal cations and their attendant anion(s). The problems in obtaining the selective extraction of anions makes the development of such a process very challenging, especially for hydrophilic anions such as sulphate which would be present in many pregnant solutions generated in processing sulfides ores. The rapidly emerging field of anion coordination chemistry and approaches to the development of selective ligands are discussed. Chapter 2 focuses on the pH dependence of sulfate-loading from an aqueous solution into chloroform solutions of a selection of zwitterionic ditopic ligands containing two 3-dialkylaminomethylsalicylaldimine units. These “salen-type2 ligands have quadridentate N2O22- binding sites for divalent metal cations and the cis-coordination of the phenolate aligns the pendant protonated 3-dialkylaminomethyl groups to bind to a sulfate dianion. Studies of the pH dependence of sulfate-loading confirm that sulfate binding is enhanced significantly by the incorporation of a divalent cation such as Cu2+ in the salen N2O22- site. Metal dication loading is very dependent on the nature of the bridging group between the two imines in the “salen” unit; Cu2+ loading follows the order ortho-phenylene > 1,2-ethane > 2,2’-biphenyl. The ethane-bridged ligand, 4,4’-di-tert-butyl-6,6’-bis(dihexylaminomethyl)-2,2’-(ethylenedinitrilodimethylidyne) diphenol, was found to have a nearly ideal loading profile for CuSo4. Stability to hydrolysis and oxidation is a key requirement for commercial metal solvent extractants. The stability of the imine bond in the “salen-type” extractants investigated in chapter 2 was tested in a two phase chloroform: water systems under conditions likely to be used for loading or stripping of metal salts. Stability is dependent on the nature of the bridging unit between the two imines varying in this order 2,2’-biphenyl > ortho-phenylene > 1,2-ethane. Two new ligands, 4,4’-di-tert-butyl-6,6’-bis(dihexylaminomethyl)-2,2’-(ethylenedinitrilo-1,1’-phenyldimethylidyne) diphenol and N,N’-dimethyl-N,N’-bis(2-hydroxy-3-[(E)-phenyliminomethyl]-5-tert-butylbenzyl)hexane-1,6-diamine, which exhibit improved stabilities at low pH are also discussed.
37
Howard, Maury Elizabeth. "Characterization of synthetic biopolymeric chelators for trace metal extraction and recovery /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Full text
38
Chatreewongsin, Urai. "Metal Extraction From Soil Samples By Chelation in a Microwave System." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/26982.
Full textAbstract:
This work involves the combination of chelation and microwave extraction as a technique for extracting adsorbed metals in soil. It has been termed in this work, Chelate Assisted Microwave Extraction (CAME). Unlike other extraction methods, CAME is able to differentiate between anthropological and geological trace metals.
The method has been applied to major sample matrices included three types of soils (Bertie Sandy Loam, Davidson Silty Clay, and Davidson Clayey Loam) as well as sea sand, alumina, and iron oxide. In order to investigate the effects of sorptive coatings on metal concentrations, a sample set was first treated with humic acids, which represented organic coated materials. Afterwards, copper (II) solutions were spiked to both untreated and treated matrices and the efficiencies of recoveries were studied. Metal determinations were performed by Inductively Coupled Plasma-Atomic Emission Spectrophotometry (ICP-AES).
Initial studies of control (untreated soil) and long-term Cu amended (spiked) Bertie Sandy Loam (BSL) indicated that extraction efficiencies were method dependent. Ethylenediaminetetraacetic acid (EDTA) was a primary chelating agent used for method comparisons. Extracting solutions having a pH range from 7.8 to 10.1 did not affect the EDTA-microwave method, but the increase in pH enhanced Cu removal by the EDTA-shaking extraction method which was a conventional chelation using a mechanical shaker. With the EDTA-microwave method, complete extraction was achieved in a short period of time (20 minutes). Compared to the EDTA-shaking method using two sandy soils, the EDTA-microwave method proved to be more efficient in extracting sorbed metals in soils (5.9 vs. 4.6 µg/g for the control BSL and 37.5 vs. 27.8 µg/g for the amended BSL.
FT-IR and C13 NMR were used to characterize extracted and commercially available humic acids. The latter was employed to prepare the humate coated materials. Iron oxide containing materials such as Davidson Silty Clay (DSC), Davidson Clayey Loam (DCL), and iron oxide (Fe2O3), showed extremely high adsorption capabilities for humic acids, while sea sand, Bertie Sandy Loam, and alumina (Al₂O₃) provided lower adsorption capabilities for humic acids. Two sets of uncoated and humate coated materials were used for Cu spiking procedures using 0.001 M Cu (II) at pH 5.3 for 24 hour-equilibration. Three original soils and alumina showed high adsorption capabilities for Cu (II). The presence of coated humate helped increase Cu adsorption capabilities of these soils, but diminished the ability of alumina to react with Cu (II) ions. For HA-uncoated matrices, iron oxide had a higher Cu adsorption capability than sea sand but less than real soils. Humate coating improved Cu adsorption capabilities of not only real soils but iron oxide and sea sand as well.
Lastly, the developed method named Chelate Assisted Microwave Extraction (CAME) was further examined and optimized. Several samples were investigated for extraction efficiencies. A two-step extraction, applying 120 W for 5 min followed by 60 W for 10 min, was efficient in removing sorbed metals from different matrices regardless of sorptive oxide and organic components. Concentrations of chelating agents slightly affected percent metal removal; however, there was no significant difference in results obtained using EDTA or diethylenetriaminepentaacetic acid (DTPA). Recoveries of spiked metals (Cu and Cd) ranged from 96 to 107%. Using the untreated (control) Davidson Silty Clay and Bertie Sandy Loam, the comparison of other chelating solutions were made. Clearly, CAME was promising and proved to be a good alternative to classical shaking method for extracting adsorbed metals from soils.Ph. D.
39
DESHPANDE, SUSHILENDRA ARUN. "FEATURE EXTRACTION AND INTRA-FEATURE DESIGN ADVISOR FOR SHEET METAL PARTS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1070392705.
Full text
40
Hildreth, Scott A. "Statistical SPICE parameter extraction for an N-Well CMOS process /." Online version of thesis, 1995. http://hdl.handle.net/1850/12177.
Full text
41
Angarita, Fonseca Maria Paula. "Electrolytic extraction of a metal from its metal compound: estimates of optimal energy requirements and their consequences." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98004.
Full textAbstract:
Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, Engineering Systems Division, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 62-66).
To ensure the sustainability of a world whose growing population demands more materials, products, and energy, we must closely examine the sustainability of the industries that supply them. Metal-making industries encounter an opportunity space at the extraction stage of a metal life cycle when aiming at making a significant impact in energy efficiency and carbon emission mitigation. We first develop a thermodynamic model that establishes the technical criteria for the most efficient operation of an electrolytic cell for a variety of metals. Second, we explore the rigidity of the operating boundary conditions and their impact on energy consumption. We then proceed to examine the energy and carbon impact of a hypothetical electrolytic ferrochromium operation in the United States. This case study demonstrates that the thermodynamic model can serve as a reference framework through which diverse stakeholders can compare the environmental impact of existing and innovative metal extraction processes in order to make informed decisions about environmental regulation, investments, subsidies, and mineral resource management.
by Maria Paula Angarita Fonseca.
S.M. in Technology and Policy
42
Bauer, Caroline. "Metal ion extractant in microemulsion : where solvent extraction and surfactant science meet." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20041/document.
Full textAbstract:
Le but du travail est d'étudier la structure supramoléculaire de mélanges de tensioactif hydrophile, n-octyl-beta-glucoside (C8G1), et d'un extractant d'ions métalliques hydrophobe, le tributyl-n-phosphate (TBP), en présence d'eau, d'huile et de sels. Les systèmes classiques d'extraction ionique (composés d'une phase aqueuse, d'huile et d'extractant dont le but est d'extraire un soluté de la phase polaire sont passés en revue. L'aspect colloïdal et les transitions de phases que l'on retrouve dans ces systèmes sont souvent décrits singulièrement. Nous avons transposé l'approche « diagramme de phases » issue de la physico-chimie des systèmes moléculaires organisés à ces systèmes d'extractant afin d'orienter globalement l'analyse de ces systèmes complexes. La discussion est basée sur des considérations géométriques. Un modèle thermodynamique a été développé en considérant les contraintes d'empilement des ces extractants dans le film moléculaire formant les micelles inverses d'extractant dans l'huile. Ce modèle a permis de prédire la solubilité de l'eau au sein de ces micelles inverses ainsi que leurs tailles obtenues expérimentalement. Dans une deuxième partie, le comportement physico-chimique des phases aqueuses et organiques composées respectivement d'eau/C8G1 et de TBP/huile/eau ont été étudiées, en s'intéressant particulièrement aux effets de sels, par des techniques de diffusion de rayons X aux petits angles, diffusion dynamique de la lumière et de spectroscopie UV-visible. Dans la dernière partie la description complète de la microémulsion en faisant varier la balance hydrophile-hydrophobe du mélange C8G1 et TBP a été obtenue en combinant des mesures de diffusion de neutrons aux petits angles et d'analyse chimique (Karl-Fischer, Carbone Organique Total, ICP-OES…). Le comportement co-surfactant du TBP a été déterminé par comparaison aux co-surfactants classiques que sont les n-alcools (4The presented work describes the supramolecular structure of mixtures of a hydrophilic surfactant n-octyl-beta-glucoside (C8G1), and the hydrophobic metal ion extractant tributylphosphate (TBP) in n-dodecane/water as well as in the presence of salts.In the first part, basic solvent extraction system, composed of water, oil and extractant, will be introduced. The focus, however, lies on the extraction of multivalent metal ions from the aqueous phase. During this extraction process and in the following thermodynamic equilibrium, aggregation and phase transition in supramolecular assemblies occur, which are already described in literature. Notably, these reports rest on individual studies and specific conclusions, while a general concept is still missing. We therefore suggest the use of generalized phase diagrams to present the physico-chemical behaviour of (amphiphilic) extractant systems. These phase diagrams facilitated the development of a thermodynamic model based on molecular geometry and packing of the extractant molecules in the oil phase. As a result, we are now in the position to predict size and water content of extractant aggregates and, thus, verify the experimental results by calculation.Consequently, the second part presents a systematic study of the aqueous and organic phase of water/C8G1 and water/oil/TBP mixtures. The focus lies on understanding the interaction between metal ions and both amphiphilic molecules by means of small angle x-ray scattering (SAXS), dynamic light scattering (DLS) and UV-Vis spectroscopy. We confirmed the assumption that extraction of metal ions is driven by TBP, while C8G1 remains passive. In the third and last part, microemulsions of C8G1, TBP, water (and salt) and n-dodecane are characterized by small angle neutron scattering (SANS), and chemical analytics (Karl Fischer, total organic carbon, ICP-OES,...). The co-surfactant behaviour of TBP was highlighted by comparison to the classical n-alcohol (4
43
Squires, Clare. "Ligand self assembly to enhance the strength and selectivity of metal extraction." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/14470.
Full textAbstract:
The strength and selectivity of commercial phenolic oxime copper extractants are thought to be due to the hydrogen-bonded pseudo-macrocycle which this ligand forms around copper. This thesis investigates the role of hydrogen-bonding of sulfonamido ligands to determine the importance of ligand association prior to and upon complexation. Chapter 2 deals with the coordination chemistry of a series of 11 relatively simple bidentate monosulfonamidodiamine ligands. The solid state structures of these ligands are difficult to predict and illustrate that a surfeit of hydrogen-bond donors and acceptors incorporated into a relatively flexible ligand leads to a variety of hydrogen-bond interactions in the solid-state and hence a range of complicated secondary structures are observed including two and three dimensional arrays. However, these ligands do form pseudo-macrocycles around copper and nickel(II) centres. These ligands were found to be quite weak (pH1/2 4-6) extractants when used in pH-swing process. Increasing the size of the chelate ring from five to six leads to even weaker extractants. In Chapter 3 the synthesis and characterisation of a series of 6 sulfonamido-oxime ligands which have a similar backbone to the commercial ortho-phenolic oximes are described. The majority of solid-state structures contain hydrogen-bonded dimers and appear to have structures which are independent of small substituent changes in the ligand. However the E, Z isomerisation of the oxime is important. The Z isomer only forms polymeric species. Complex formation by the sulfonamido-oxime ligands is less predictable than with the monosulfonamidodiamines and both 2:1 and 1:1, ligand to metal complexes are observed. In addition to the expected bonding of the sulfonamido and oximic nitrogen atoms, the bonding of the sulfonamido oxygen atoms and the deprotonated oximic oxygen atom to metal ions is also observed. Investigation of the solution chemistry of the monosulfonamidodiamine and the sulfonamido-oxime ligands are considered in Chapter 4. ESI-MS shows evidence for dimer formation and 1H nmr, VPO and IR analyses show that self-association occurs in solution and is very concentration, temperature and solvent dependent. This chapter also discusses the development of monosulfonamidodiamine and sulfonamido-oxime ligands with higher solubility in solvents of low polarity such as toluene. The possibility of developing sulfinamido ligands is also discussed covering the synthesis of sulfinyl chlorides and the attempted preparation of prototype sulfinamido ligands. Chapter 5 deals with the development of pseudo-macrocyclic and pseudo-cage structures using ternary metal/sulfonamide/amine systems. Bis- and tris-sulfonamido ligands have been synthesised and their solid state structures were investigated. The formation of metal complexes of these ligands proved difficult and no ternary complexes were isolated.
44
Diffin, B. "The mechanism of metal detoxification of waste activated sludge by pH depression." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353776.
Full text
45
Mebrahtu, Fanuel M. "Transport and extraction of Au(lll) using thiourea ligands." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/50206.
Full textAbstract:
Thesis (MSc)--Stellenbosch University, 2004.ENGLISH ABSTRACT: A series of di- and mono-substituted acyl(aroyl) thioureas were examined for the extraction and transportation of Au(III). Two-phase metal ion extraction experiments were employed to investigate the extraction behaviour of these ligands. The effect of varying ligand concentration on the extraction trend of these ligands was investigated. The results show that the different substituent groups on the benzoyl ring can affect the extraction pattern of the metal. Furthermore, the alkyl substituents on the thiourea moiety and varying the ligand concentration have an influence on the percentage of metal ion extracted. With the exception of the H2L2(N,N-di-propyl-N'- benzoylthiourea ) ligand the di-alkyl substituted thioureas were more efficient for the metal ion extraction than the mono-alkyl ligands. In almost all the experimental set ups there was reduction of the Au(lIl) to Au(l) and Au(O) but it was more pronounced with HL3 (N,N-di-(2-hydroxyethyl)-N'-benzoylthiourea). Transport experiments were also conducted, the experimental set up for transportation was a concentric type cell involving a 3-phase system - 2 aqueous phases ( source and receiving phase) separated by a chloroform membrane incorporating the ligand. The transport results however only gave a satisfactory result of about 5% of gold transported by the HL1 (N,N-dibutyl-N'-benzoylthiourea). All other ligands attempted resulted in metal ion being present in the organic phase, but no metal ion present in the receiving phase. To help drive the transport of the metal ion to the receiving phase CN-, S203 2- and perchloric acid were incorporated into the receiving phase. The transport results were not enhanced with these substances being present in the aqueous receiving phase. The aqueous source and receiving phases were analyzed by flame atomic absorption spectroscopy (FAAS). Finally the N,N-diethyl-N'-camphanoylthiourea (HL10) ligand and its complex with Au(l) were synthesised. Single crystals of the complex were grown for X-ray crystallography and the crystal and molecular structure of the complex was determined. The complex crystallizes in the monoclinic space group P21. The cell parameters are a = 10.7356(7)A b = 16.3443(11)A c = 10.9268(7)A f3 = 103.1450(10t , and final R-factor of 1.76%. The coordination sphere around Au(l) shows a nearly linear arrangement of sulphur and chloride.
AFRIKAANSE OPSOMMING: In hierdie proefskrif is In aantal mono- en di-gesubstitueerde asiel(ariel) thioureums ondersoek vir die transportasie en ekstraksie van Au(III). Twee-fase metaalioon vloeistof-vloeistof ekstraksie eksperimente is gebruik om die ekstraksie patroon van hierdie ligande te ondersoek. Die effek van verskillende ligand konsentrasies op die ekstraksie neiging van hierdie ligande is ondersoek. Resultate toon dat die verskillende substituente op die benziel ring die ekstraksie patroon van die metaalioon beïnvloed. Verder, is gevind dat die alkiel substituente op die thioureum saam met varierende ligand konsentrasies geensins die metaalioon ekstraksie beïnvloed nie. Met die uitsondering van H2L2 (N,N-dipropiel-N'-benzielthioureum) is die di-alkiel gesubstitueerde ligande meer effektief vir metaalioon ekstraksie in vergelyking met die mono-alkiel ligande. In baie van die eksperimente is In reduksie van Au(llI) na Au(l) en Au(O) gesien en dit is baie duidelik met ligand HL3 (N,N-di(2- hidroksie-etiel)N'-benzielthioureum). Alle waterige fases is ge-analiseer met gebruik van Atoomabsorpsie Spektroskopie (AAS). Transportasie eksperimente is ook uitgevoer met gebruik van In drie-fase selsisteem. Twee waterige fases (bron- en ontvang-fase) is geskei met die chloroform membraan fase wat die ligande bevat. Hierdie eksperimente het net In 5% Au(lll) transportasie getoon met HL1(N,N-dibutiel-N'-benzielthioureum). Daar was geen transportasie van Au(lIl) met enige van die ander ligande. Analise van die twee waterige fases het getoon dat die metaalioon eindelik goed ge-ekstraeer is en is teenwoordig in die membraan fase. Om die transportasie van Au(lIl) aan te spoor, is CN-, s2ol- en perchloorsuur in die ontvang-fase geinkorporeer. Die resultate was geensins beïnvloed nie. N,N-di-etiel-N'-kamfonielthioureum (HL10)ligande en die kompleks daarvan met Au(l) is ook gesintetiseer. Enkel-kristalle van die kompleks is verkry en X-straal kristallografiese analiese is onderneem. Hierdie kompleks kristalliseer in die monokliniese ruimtegroep P21,met a =10.7356(7)Á, b=16.3443(11)Á, c=10.9268(7)Á en ~=103.1450(10t. Die finale R-faktor is 1.76%. Die koordinasie om Au(l) toon In liniêre geometrie met swael en chloor.
46
Adams, Robert Jonathan Watt. "The extraction of caesium and cobalt(II) from solution using inorganic ion exchangers in electrochemical ion exchange." Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385171.
Full text
47
Copham, Piers Martin. "Rotating electrodes in molten salt electrowinning." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330202.
Full text
48
Crane, Martin John. "Geochemical studies of selected base metal minerals from supergene zone /." View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030721.132607/index.html.
Full textAbstract:
Thesis (PhD) -- University of Western Sdyney, 2001."A thesis presented in accordance with the regulations governing the award of the degree of Doctor of Philosophy, University of Western Sydney" "November 2001" Bibliography: leaves 249 - 254.
49
Lopian, Tobias. "Characterization of a metal-extracting water-poor microemulsion." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT206/document.
Full textAbstract:
Le recyclage des terres rares à partir de déchets électroniques n'a toujours pas trouvé une réalisation industrielle significative. L'une des raisons est le manque de procédures de séparation optimisées en raison de connaissances fondamentales médiocres sur ces systèmes. En raison des similitudes chimiques et physiques de ces métaux, la conception d'une formulation efficace, adaptative et prédictive est toujours hors de portée des possibilités. L'interprétation supramoléculaire de la formation complexe dans la phase organique est de plus en plus importante au cours des dernières années. C'est l'approche la plus prometteuse permettant l'explication de divers phénomènes, tels que la formation de la troisième phase et les signaux forts dans de petites expériences de diffusion et de revenir à des méthodes bien connues de la science des tensioactifs. Notre contribution à une compréhension plus complète dans cette matière est l'analyse du comportement électrodynamique de ces phases et la corrélation de ces résultats avec les résultats des propriétés d'auto-assemblage et du transport de masse dans ces médias. Pour cette étude, nous avons spécifiquement conçu un modèle de référence, en passant un processus d'extraction à ses quatre composants fondamentaux: l'extracteur avant l'extraction (acide Di-(2-éthylhexyl) phosphorique, HDEHP), l'extrait après extraction (son sel de sodium, NaDEHP ), le toluène comme diluant apolaire et de l'eau. Un prisme de phase de Gibbs a été préparé (illustré sur la figure 1), où l'axe z donne le rapport de HDEHP à NaDEHP, ce qui représente le développement d'une extraction. Couvrant le domaine de basse fréquence, la spectroscopie d'impédance a été la méthode de choix afin de déterminer la conductivité dépendant de la fréquence. En utilisant la spectroscopie de relaxation diélectrique, nous révélons des processus dynamiques rapides à haute fréquence. Des mesures combinées SAXS et SANS ont été effectuées pour comparer les tendances électrodynamiques avec les propriétés d'agrégation et les interactions entre groupes. Deux phénomènes ont été identifiés comme responsables du profil de conductivité dans les systèmes micellaires inverse: la formation d'agrégats chargés par la dissimulation et la percolation. Tout au long du système de référence, ces deux processus ont été sondés en fonction de trois variables: la concentration totale d'agent d'extraction, le rapport eau-agent tensioactif et le rapport Na: H. En tant que résultat majeur, l'eau joue un rôle important dans les deux processus. En cas de percolation, les agrégats inverse ne peuvent pas fusionner en l'absence d'eau. Par conséquent, la conductivité électrique est interdite. Dans les systèmes dilués, l'eau facilite le processus de dismutation, entraînant une augmentation de la conductivitéRecycling of rare earths from electronic waste has still not found a significant industrial realization. One reason is the lack of optimized separation procedures due to poor fundamental knowledge on these systems. Due to the chemical and physical similarities of these metals, designing an efficient, adaptive and predictive formulation is still out of scope of possibilities. The supramolecular interpretation of complex-formation in the organic phase has gained an increasing importance in the last years. It is the most promising approach allowing the explanation of diverse phenomena, such as third phase formation and strong signals in small scattering experiments and to revert to methods well known from surfactant science. Our contribution towards a more complete understanding in this matter is the analysis of the electrodynamic behaviour of such phases and the correlation of these findings with the results of self-assembly properties and mass transport in these media.For this study, we specifically designed a reference model, breaking an extraction process down to its four fundamental components: The extractant before extraction (Di-(2-ethylhexyl)phosphoric acid, HDEHP), the extractant after extraction (its sodium salt, NaDEHP), toluene as apolar diluent and water. A Gibbs phase prism has been prepared (illustrated in Figure 1), where the z-axis gives the ratio of HDEHP to NaDEHP, representing the development of an extraction. Covering the low frequency-domain, impedance spectroscopy has been the method of choice in order to determine the frequency-dependent conductivity. Using dielectric relaxation spectroscopy, we reveal fast dynamic processes at high frequencies. Combined SAXS and SANS measurements have been performed to compare the electrodynamic trends with aggregation properties and intercluster interactions.Two phenomena have been identified to be responsible for the conductivity profile in reverse micellar systems: the formation of charged aggregates through dismutation and percolation. Throughout the reference system, these two processes have been probed as function of three variables: total extractant concentration, the water-to-surfactant ratio and the Na:H-ratio. As a major result, water plays a significant role in both processes. In case of percolation, reverse aggregates are not able to merge in the absence of water. Therefore, electrical conductivity is prohibited. In dilute systems, water facilitates the dismutation–process leading to an increase in conductivity
50
Ho, Mark D. "Application and assessment of sequential extraction for trace metal characterization of contaminated soil." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0009/MQ40907.pdf.
Full text