Tesis: "Metals Equilibrium"

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Evans, Paul Vincent. "Solidification of metals and alloys far from equilibrium". Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254068.

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Hörnis, Helmut Georg. "Equilibrium structures of clean and alkali covered metal (110) surfaces". Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/30284.

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3

Coetzee, Colette. "Solidification behaviour of titania slags". Diss., Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-02282007-152308.

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4

Benavente, Martha. "Adsorption of Metallic Ions onto Chitosan : Equilibrium and Kinetic Studies". Licentiate thesis, Stockholm : Kemiteknik, Chemical and Engineering and Technology, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4746.

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Olds, William. "Lignite Derived Humic Substances for Treatment of Acid Mine Drainage". Thesis, University of Canterbury. Civil and Natural Resources, 2011. http://hdl.handle.net/10092/6583.

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Addition of alkalinity to acid mine drainage (AMD) results in the neutralisation of acidity and precipitation of dissolved metals as insoluble hydroxides. Two aspects of the current AMD treatment practice at the Stockton Mine could be enhanced. Firstly, residual water quality may be poor due to unreacted alkalinity reagents, particularly CaCO3, resulting in poor water clarity and elevated suspended solids (SS). Secondly, neutralisation to circum-neutral pH may not avoid the discharge of residual metals (Ni and Zn) due to incomplete adsorption and hydroxide precipitation. The aim of this project was to enhance the conventional neutralisation of AMD through addition of humic substances (HS) to reduce residual SS and trace metal concentrations. Humic substances are organically derived and have a high molecular weight. Functional groups on the surface of HS are capable of binding dissolved metals, forming HS-metal complexes. Incorporation of HS complexed metals into settling floc could result in increased metal removal from the dissolved phase. Modified jar testing was used to investigate the effects of HS addition before, after and during (pH 4.5) neutralisation of AMD in two treatment scenarios at the Stockton Mine; the Blackwater Treatment Plant (BTP) using NaOH and Ca(OH)2 and the Mangatini Stream-sump System (MSS) using CaCO3. Supernatant samples collected during the sedimentation period were analysed for basic water quality parameters (turbidity and suspended solids) and dissolved (< 0.45 µm) metal concentrations. The addition of HS to the BTP process before (pH 2.8) and during (pH 4.5) neutralisation resulted in HS precipitation. Precipitated HS subsequently acted as a nucleation site, triggering flocculation of precipitating metal hydroxides, resulting in low turbidity and suspended solids (SS) of less than 2 NTU and 5 mg/L, respectively. The addition of HS after neutralisation (pH 7) did not result in HS precipitation. Intermolecular bridging of HS by the divalent Ca resulted in incorporation of HS into floc when neutralised by Ca(OH)2, resulting in low turbidity and SS. However, in NaOH neutralised conditions, the monovalent Na was unable to bridge HS molecules, resulting in HS remaining dissolved and contributing to elevated turbidity and SS of up to 24.4 NTU and 18.4, respectively. The neutralisation efficiency of CaCO3 is relatively low, thus approximately 1000 mg/L CaCO3 remained unreacted in MSS scenarios, resulting in elevated turbidity and SS. When added after neutralisation, dissolved Solid Energy Humic Acid (SEHA) facilitated flocculation of residual CaCO3 SS, resulting in an up to 75% lower suspended solids than CaCO3 neutralisation alone conditions. Although the results are good, the efficiency of SEHA as a polymer compared unfavorably in a cost: benefit analysis to two commercially available polymers for the removal of residual CaCO3. Neutralisation of AMD in control samples resulted in decreased concentrations of the target metal group (Ni, Zn, Cu, Cd, and Pb) by hydroxide precipitation, co-precipitation, and adsorption. Equilibrium speciation modeling showed that the HS-metal binding affinity controlled the effectiveness of HS addition for metal removal. The low HS complexation affinity of Ni and Zn resulted in no additional metal removal by HS dosing. The removal of Cu was enhanced by over 50% for SEHA 20 during-neutralisation conditions neutralised by both NaOH and Ca(OH)2. Up to 80% lower Cd concentrations were observed for all HS dose conditions when neutralised by Ca(OH)2. Data for CaCO3 HS dosed metal removal was statistically indeterminate. The high detection limit for Pb made any HS dosed removal enhancement difficult to identify, which was unfortunate as Pb has a high HS complexation affinity (Čežı́ková, Kozler et al. 2001; Milne, Kinniburgh et al. 2003). A simple cost: benefit analysis showed that the additional removal of metals by HS dosing was less efficient than conventional neutralisation alone, on a cost basis. Overall, incorporation of HS into AMD treatment results in improved water quality for CaCO3 neutralisation and lower concentrations of metals with a high HS binding affinity, for some conditions. However, further investigation is required to improve the feasibility of HS incorporation into the AMD neutralisation process.

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6

Pissetti, Fabio Luiz. "Preparação de redes modificadas de poli(dimetilsiloxano) com ion piridinio ou etilenodiamina : estudo da adsorção de ions metalicos em etanolico". [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249701.

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Orientador: Yoshitaka Gushikem
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Neste trabalho foram preparadas redes poliméricas com propriedades elastoméricas a partir do poli(dimetilsiloxano) (PDMS), modificadas com íon piridínio ou etilenodiamina. Os materiais preparados foram caracterizados por espectroscopia no infravermelho, análise termogravimétrica, calorimetria diferencial de varredura e ressonância magnética nuclear de C e Si. Os resultados destas análises mostraram que ambos os materiais apresentam boa estabilidade térmica e uma temperatura de transição vítrea de ~ 160 K. Os dados de RMN indicaram que rede foi formada pela reticulação das cadeias lineares de PDMS por ¿clusters¿ de siloxanos do tipo T, provenientes da hidrólise/condensação de 3-cloropropiltrimetoxissilano e do 2-aminoetil-3- aminopropiltrimetoxissilano. Além disso, por ensaios de intumescimento foi calculada a massa molecular média entre os nós da rede polimérica e também a densidade de reticulação dos materiais. Os valores encontrados sugerem um alto grau de reticulação para ambos os materiais estudados. A rede modificada com etilenodiamina apresentou a maior densidade de reticulação. Com intuito de avaliar a potencialidade dos materiais como adsorventes de íons metálicos de uma solução etanólica, foram obtidas isotermas de adsorção. Para o material modificado com o íon piridínio os metais estudados foram o Co, Cu e Fe, que foram retirados da solução com boa eficiência, 0,25, 0,29 e 0,45 mmol g, respectivamente. Os haletos metálicos foram adsorvidos pela rede polimérica modificada na forma de complexos aniônicos FeCl4¨, CuCl4 e CoCl4. Os resultados de UV-Vis sugeriram que os complexos formados na interface têm uma simetria tetraédrica ou tetraédrica distorcida. Para a rede modificada com etilenodiamina foram estudados os metais Cu, Ni e Fe. Neste caso o material apresentou uma elevada capacidade de adsorção para os cloretos de Fe (1,35 mmol g) e Cu (1,25 mmol g), enquanto que, para o Ni a capacidade de adsorção foi consideravelmente menor, 0,36 mmol g. Os resultados de espectro eletrônico para este material sugeriram que o cobre é adsorvido pela rede polimérica modificada na forma do complexo, [Cu(en)], com uma estrutura tetraédrica distorcida, enquanto que para o níquel os resultados sugeriram formação de um complexo octaédrico. Os dados obtidos nas isotermas de adsorção foram usados para calcular as constantes de equilíbrio para a adsorção dos íons metálicos. Estes resultados permitiram verificar que no material modificado com o íon piridínio a adsorção de CoCl2 e CuCl2 segue o modelo descrito por Langmuir. Para a adsorção do FeCl3 outro modelo, em que centro adsorvedor é composto por dois grupos ligantes, foi necessário para descrever o processo de adsorção. Neste caso, há um efeito cooperativo entre as espécies formadas na superfície. Para o material modificado com etilenodiamina, os cálculos mostraram que a adsorção dos três íons metálicos pode ser descrito adequadamente pelo modelo de Langmuir
Abstract: In this work elastomeric polymeric networks based on poly(dimethilsiloxane) PDMS, modified with pyridine ion or ethylenediamine, were prepared. These materials were characterized by infrared spectrometry, thermogravimetric analysis, differential scanning calorimetry and nuclear magnetic resonance (NMR) of Si and C. The results showed that both materials presented a good thermal stability and a glass transition temperature at ~ 160 K. The NMR data indicated that the polymeric network was formed by PDMS linear chain crosslinked with siloxane clusters of T Si units formed from hydrolyses/condensation of 3-chloropropyltrimethoxysilane or 2-aminoethyl-3- aminopropyltrimethoxysilane. Using the swelling measurements, the average molecular weight between crosslinking points and the polymeric network crosslinking density were calculated. The results obtained suggested a high degree of crosslinking for the prepared materials, which was higher for the ethylenediamine. To evaluate the potential use of the prepared materials as adsorbents, adsorption isotherms were obtained from an ethanolic solution. For the polymeric network modified with pyridine ion the metallic ions studied were Cu, Co and Fe, which were adsorbed with high efficiency of 0.25, 0.29 e 0.45 mmol g, respectively. Metal halides were adsorbed by the modified polymeric network as an anionic complex, FeCl4¨, CuCl4 and CoCl4. The UV-Vis data suggested that the formed complexes at surface presented a tetrahedral symmetry or distorted tetrahedral symmetry. For The polymeric network modified with ethylenediamine, the metallic ions studied were Cu, Ni and Fe. In this case, the material showed a higher capacity of adsorption for Fe (1.35 mmol g) and Cu (1.25 mmol g), while, to Ni that capacity was significantly lower, 0.36 mmol g. The electronic spectra data suggested that the copper was adsorbed by the modified polymeric network as [Cu(en)], with a distorted tetrahedral symmetry, while the nickel was adsorbed with a octahedral symmetry. From the isotherm data, the equilibrium constants of the metallic ion adsorption were calculated. These results allowed verifying that the adsorptions of CoCl2 e CuCl2 are appropriate described by Langmuir equation. For the FeCl3 another model, which two adsorptions centers are envolved was necessary to describe the adsorption process. In this case, there was a cooperative effect among the adsorbed species. The results for polymeric network modified with ethylenediamine showed an adsorption described by the Langmuir equation for all metallic ions studied
Doutorado
Quimica Inorganica
Doutor em Ciências

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7

Norman, Per-Albin. "Filter Materials for Sorption of Cu and Zn in Stormwater Treatment: A Batch Equilibrium and Kinetic study". Thesis, Luleå tekniska universitet, Arkitektur och vatten, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-68059.

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Urban stormwater is today recognized as a significant source of pollution that has contributed to the deterioration of water quality in lakes and streams. Of the pollutants, metals are commonly occurring in stormwater and can cause major damage when released into the receiving waters. A promising treatment method for removing these metals before it reaches the receiving waters is to filter the water in various filter technologies such as catch basin inserts. In this study, the potential of five materials to remove dissolved copper (Cu) and zinc (Zn) from stormwater was investigated. The study was initiated with batch equilibrium tests to assess the sorption capacity of the materials at different metal concentrations relevant for stormwater. This was done in both single and binary batches to investigate whether or not any competitive sorption occurred between the metals. Langmuir, Freundlich and Sips isotherm models were adapted to the obtained data. Through geochemical modelling, it was also possible to investigate whether precipitation of metals was likely. Finally, kinetic studies were conducted to investigate whether the reaction rate of Cu and Zn was relevant in the context of catch basin inserts. The results showed that the biochar had the highest sorption capacity followed by peat, bark, milkweed, and polypropylene. It could also be noted that Cu competed with Zn binding sites at high concentrations and that the sorption capacity of biochar, peat and bark, at concentrations between 50-100 μg/l Cu and 50-500 μg/l Zn, was sufficient to meet the limits set for stormwater emissions. For these sorbents, the reaction rate was also significant. Kinetics tests showed that at an initial concentration of 1,000 μg/l, 83% of the metals were sorbed after 5 minutes and after 10 minutes this number was 93%. Bark and peat also showed low effluent pH and leaching of dissolved organic carbon (DOC). The Langmuir and pseudo-second order equation could be well adapted to the data while geochemical modelling showed that precipitation of metals was unlikely. This suggests that chemical adsorption may be the mechanism that largely accounted for the removal of Cu and Zn. The results of this study can hardly be used to estimate the field performance of stormwater filters, but can be used as a basis for comparing and selecting sorbents for subsequent column tests.
I denna studie undersöktes potentialen för fem material att avskilja löst koppar (Cu) och zink (Zn) från dagvatten. Studien inleddes med skaktest för att testa sorptionsförmågan hos materialen vid olika metallkoncentrationer relevant för dagvatten. Detta gjordes i både singel och binära test för att undersöka om någon konkurrerande sorption skedde mellan metallerna. Langmuirs, Freundlichs och Sips isotermmodeller anpassades även till resultatet. Genom geokemisk modellering var det även möjlig att undersöka om utfällning av metaller var sannolik. Till sist gjordes kinetiska studier för att undersöka om reaktionshastigheten för sorption av Cu och Zn till filtermaterialen var relevanta i ett brunnsfiltersammanhang. Resultaten visar att biokol hade den största sorptionsförmågan följt av torv, bark, sidenört och polypropylen. Det kunde även konstateras att koppar konkurrerade om sorptionsplatser för zink vid högre koncentrationer och att sorptionskapaciteten för biokol, torv och bark, vid koncentrationer mellan 50-100 µg/l Cu och 50-500 µg/l Zn, är tillräckligt hög för att uppfylla gränsvärdena för utsläpp av dagvatten. För dessa sorbenter var reaktionshastigheten betydande. Kinetiktesten visade att vid en initial koncentration på 1,000 µg/L var 83% av metallerna sorberade efter 5 minuter och efter 10 minuter var denna siffra uppe i 93%. Bark and torv uppvisade även ett lågt uppmätt pH och lakade löst organisk kol (DOC). Langmuir och pseudo-andra ordningens ekvation kunde anpassas väl till datat samtidigt som den geokemiska modelleringen visade att utfällning av metaller var osannolikt. Detta antyder att kemisk adsorption kan vara den mekanism som till störst del stod för avskiljningen av Cu och Zn. Studien kan inte fastställa något om filtermaterialens fältprestanda, men kan användas som underlag för att jämföra och att välja sorbenter för efterföljande kolumntester.
Formas project 2016-75

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8

Nunes, Carlos Angelo. "Estabilidade de fases em ligas Mo-B-Si ricas em molibdenio". [s.n.], 1997. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264163.

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Orientador: Ana Maria Martinez Nazar
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Em trabalhos recentes têm-se proposto que materiais formados por um metal refratário em equilíbrio com uma fase intermetálica constituem a melhor opção para aplicações estruturais em temperaturas acima de 1400°C. Baseado em informações disponíveis na literatura foi identificada a existência de um campo bifásico envolvendo as fases Mo (solução sólida) e o intermetálico 'Mo IND. 5¿ ¿Si¿ ¿B IND. 2¿ ('T IND. 2¿) A 1600 º C no sistema Mo-B-Si. Tendo em vista o limitado número de informações relacionadas a este sistema objetivamos neste trabalho uma avaliação sistemática sobre estabilidade de fases na região rica em Mo. O trabalho consistiu em: determinar a relação de fases a 1600°C; desenvolver métodos de análise via microssonda eletrônica (WDS) para determinação da composição das fases; determinação da projeção liquidus; determinação da seção vertical Mo-'T IND. 2¿.A determinação da relação de fases a 1600°C confmnou a existência do campo bifásico Mo+ 'T IND. 2¿ naquela temperatura.A fase ternária 'T IND. 2¿ é rodeada pelos campos trifásicos ... Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital
Abstract: In recent investigations it has been proposed that equilibrium microstructures constituted by a refractory metal and an intermetallicphase are the best choice for high temperature structural applications at temperatures higher than 1400°C. Based on the information available in the literature it has been identified the existence of a Mo (solid solution) + intermetallic 'Mo IND. 5¿ ¿Si¿ ¿B IND. 2¿ two-phase field in the Mo-B-Si system. Considering the limited information related to this system it was the objective of this study to systematically evaluate the phase stability in the Mo-rich region. Specific objectives were: determination of the phase relations at 1600°C; development of microprobe methods of analysis to determine phase compositions; determination of the liquidus projection; determination of the Mo-'T IND. 2¿ vertical section. The Mo+ 'T IND. 2¿ two-phase field was confirmed to exist at 1600°C. The ternary phase ('T IND. 2¿) is surrounded by the following three-phase field ... Note: The complete abstract is available with the full electronic digital thesis or dissertations
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica

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9

Andrews, Lesley. "Base metal losses to furnace slag during processing of platinum-bearing concentrates". Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-01222009-172643/.

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10

Rydholm, Fredrik. "Sorption of Stormwater Pollutants for Five Material Mixtures: A batch Equlibrium Study". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-86150.

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Blue-green infrastructure have been more lucrative during the last 30 years, since urbanizationbrings more impervious surfaces that increases stormwater runoff volumes. Amongst thedifferent blue-green infrastructures there are e.g., constructed wetlands and swales. Blue-greeninfrastructure means more natural management of the stormwater, such as infiltration. Forinfiltration of water, the hydraulic conductivity is an important parameter, but also the abilityto remove dissolved pollutants. In literature, various studies of filter materials are only testedfor single dissolved pollutants, which might be a disadvantage as this does not represent fieldconditions where metals usually co-exist. Economic costs are also an important parameter,unfortunately not always targeted in research. In this thesis, the efficiency of five different material mixtures for removing typical dissolvedstormwater pollutants: chromium (Cr), copper (Cu), nickel (Ni), phosphorus (P), lead (Pb) andzinc (Zn) were studied. The mixtures were following: 1) crushed rock + soil (RO_SO) 2)crushed rock + soil + LECA 4/10 + biochar (RO_SO_BC_LC4). 3) crushed rock + soil + LECA10/20 + biochar (RO_SO_BC_LC10). 4) Soil (SO). 5) crushed rock + soil + biochar(RO_SO_BC). This study was a part of blue-green investments that is being made in Östersundmunicipality and the use of low-cost materials for stormwater treatment are examined. The study was made using batch equilibrium tests, to determine the sorption capacity fordifferent material mixtures, using dissolved metal- and P-solutions. The measured data werefitted to Freundlich, Langmuir, Temkin, Dubinin-Radushkevich and Redlich-Petersonisotherms. Economic feasibility has also been compared between the material mixtures.Results showed that SO had the best sorption capacity for all metals and P, with rankingPb > Cr > Cu > Ni > Zn for the metals. All material mixtures showed a removal efficiency of79-99%, at the lowest concentration (1mg/L) for the metals and 31-62% for the lowestconcentration of P-single solution (1mg/L). Using additional materials in the mixtures, such asbiochar, slightly improved the sorption capacities of Pb and P. Redlich-Peterson isothermsprovided the best fits to the data. An economic evaluation of the ingoing materials shows thatSO and RO_SO are undoubtedly the most feasible alternatives for removal of targeted metalsand P.

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11

Said, Marwa. "Comportements et rôles des métaux lourds au cours de la pyro-gazéification de la biomasse : études expérimentales et thermodynamiques". Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2016. http://www.theses.fr/2016EMAC0015/document.

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Malgré sa disponibilité, la biomasse de troisième génération est peu utilisée pour la production d’énergie en raison notamment de sa forte contamination en métaux lourds. Afin d’améliorer la compréhension du comportement et de l’éventuel rôle catalytique ou inhibiteur de ces métaux au cours de la pyro-gazéification, et optimiser ainsi la valorisation énergétique de la biomasse contaminée, une approche intégrée expérimentale et thermodynamique a été utilisée. Pour mener à bien ces travaux, une méthode d’insertion dans le bois du métal spécifiquement étudié pour son rôle catalytique, le nickel, a été développée. Cette méthode permet de maîtriser la composition et l’homogénéité des échantillons étudiés, sans altérer la structure du bois. Les essais de pyro-gazéification de bois brut et contaminés dans un réacteur à lit fixe, montrent que, même à faibles teneurs en nickel (entre 0,016 et 0,086 mol/ kg de bois), celui-ci a une activité catalytique importante. Les analyses des phases gaz et solides confirment que l’augmentation de la teneur en Ni dans le bois favorise les réactions de pyro-gazéification qui ont ainsi lieu à des températures plus basses (d’environ 100 °C). En parallèle, une étude thermodynamique a été réalisée afin de conforter les résultats expérimentaux et d’aider à mieux comprendre le comportement des métaux lourds présents dans le bois. Les calculs thermodynamiques, basés sur la minimisation de l’enthalpie libre de Gibbs d’un système constitué de 28 éléments (C, H, O, N et 24 éléments mineurs ou traces), fournissent la spéciation et la répartition dans les différentes phases (gaz, liquides et cendres) des métaux lourds, dont le Ni. Ces calculs, et des analyses spécifiques, ont notamment permis de déterminer la spéciation chimique et physique du nickel au cours de la pyro-gazéification et fournir ainsi une base théorique à son activité catalytique en fonction de la température
Despite its availability, contaminated biomass is not widely used for energy production due to its high contamination with heavy metals. Understanding the role and behavior of those heavy metals in the pyro-gasification process is a major scientific challenge for optimizing the thermochemical valorization of contaminated biomass. For this purpose, experimental and thermodynamic approaches were used. To carry out this work, a methodology for inserting the studied metal (nickel) in the wood matrix was developed without modifying its structure and controlling the composition and homogeneity of the studied samples. The pyro-gasification tests in a fixed bed reactor have shown that nickel has a catalytic performance even at low concentrations (between 0.016 and 0.086 mol / kg wood). The analysis of gas and solid products confirmed that the increase of Ni content in the wood generated a decrease in the samples pyro-gasification temperature by 100°C. In parallel, a thermodynamic study was conducted to confirm the experimental results and improve the understanding of heavy metals behaviors during pyro-gasification reactions. Thermodynamic calculations based on the Gibbs free energy minimization of a system consisting of 28 elements provide speciation and distribution in the different phases of heavy metals, including Ni. These calculations and specific analyses have made it possible to determine the chemical and physical speciation of nickel during pyro-gasification and thus provide a theoretical basis for its catalytic activity as a function of temperature

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12

Da'na, Enshirah Azmi Mahmoud. "Amine-Modified SBA-15 (Prepared by Co-condensation) for Adsorption of Copper from Aqueous Solutions". Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20636.

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During the last few decades, concerns about water shortages and pollution have increased. Consequently, environmental legislations and regulations for wastewater discharge have been issued. The objective of this work was to contribute in developing an efficient dsorbent for removing heavy metal ions from wastewater. The thesis focused on evaluating amine-modified SBA-15 as copper and other heavy metal ions adsorbent, by determining a variety of adsorptive properties with the aim of gaining a deep understanding of its behavior and to outline its advantages and limitations. The influence of synthesis conditions on the mesostructural stability of the resultant materials after different water treatments was systematically investigated. N2 adsorption results indicated that the material prepared via co-condensation and aged at 100 ºC was not stable and lost its ordered mesoporous structure after contacting water even at room temperature. Aging at 130 ºC and addition of inorganic salts resulted in materials that maintained their mesporous structure under different water treatments. The material synthesized in the presence of KCl was used as adsorbent for the rest of the thesis work. It was shown that the structural collapse observed in amine-modified SBA-15 prepared by conventional method when contacted with aqueous solutions is associated with the drying process, and not the treatment itself. This structural collapse was avoided by replacing water with more volatile liquids such as acetone, before drying. Amino-functionalized SBA-15 was tested for the removal of copper ions from aqueous solutions under different temperatures, pH, initial concentrations and agitation speeds. The obtained results indicated that the amino-functionalized SBA-15 was very efficient and equilibrium was achieved in less than 30 min at room temperature. The adsorption capacity increased dramatically with increasing temperature, initial copper concentration and pH. Under suitable conditions, the material exhibited high adsorption capacity even at very low copper concentration. To further investigate the effect of dsorption parameters, a 24 factorial design experiments were used to screen the factors affecting the copper removal efficiency. All the parameters main effects were significant within a 95 % confidence level. Surface composite design was used to develop a reliable model representing the adsorption process. The statistical tests used proved the adequacy of the second order model. Optimization of the factors levels was carried out and the recommended optimum conditions are: copper concentration of 20 mg/L, adsorbent/solution ratio of 1.57 g/L, pH of 6.5, and T = 294 K with 95% copper removal. The effect of regeneration conditions was investigated after three adsorption–desorption cycles, under different batchwise regeneration conditions. Using a composite surface design methodology, the effect of the regeneration conditions on the performance of the adsorbent was investigated. It was found that all the studied parameters have a statistically significant influence on the working dsorption capacity. With respect to structural properties and amine content, none of the factors was found to be significant. Regeneration using EDTA was found to be more efficient than acid treatment. Amino-functionalized SBA-15 was studied as potential absorbent for Cd2 +, Co2 +, Cu2 +, Zn2 +, Pb2 +, Ni2 +, Al3+ and Cr3 +. The adsorption capacity and selectivity of the material were investigated in single and multi-metal solutions. Using very dilute solutions, i.e., 10 ppm, more than 95% of cations were removed, except for Co2+ and Cr3 +, indicatingthe high sensitivity of the current adsorbent. The adsorption capacities in multi-metal solutions were lower than in single-metal ones because of competition between metallic elements for the amine groups. The adsorbent was not affected in the presence of sodium, potassium, and calcium, indicating that the ionic strength does not affect the adsorption properties. Application of this material to remove copper in tap water, river water, and electroplating wastewater was shown to be successful. Dynamic experiments were carried out on the adsorption of copper ions in a laboratory packed-bed of amine-modified SBA-15. Breakthrough curves were analyzed at different flowrates and after two adsorption-desorption cycles. Furthermore, a model based on mass balance was developed and tested for predicting the breakthrough curves under different experimental conditions used. The results suggested that the developed model was in good agreement with the experimental data. Bed regeneration was performed by circulating 0.2 M EDTA solution through the column for 30 min. Résumé Durant les quelques dernières décennies, les préoccupations concernant les pénuries d'eau et la pollution en général ont augmenté. Par conséquent, des législations et des réglementations environnementales pour les rejets d'eaux usées ont été introduites. L'objectif de ce travail était de contribuer au développement d'un adsorbant efficace pour éliminer les ions de métaux lourds des eaux usées. Cette thèse porte sur l'évaluation de SBA-15 modifiée avec des amines comme adsorbant pour le cuivre et d'autres ions de métaux lourds par la détermination d'une multitude de propriétés d'adsorption dans le but d'acquérir une profonde compréhension de son comportement et d’identifier ses avantages et ses limites. L'influence des conditions de synthèse sur la stabilité des matériaux mésoporeux obtenus après différents traitements a été étudié de façon systématique. Les résultats d'adsorption de N2 ont indiqué que le matériel préparé par co-condensation et vieilli à 100 °C n'était pas stable et a perdu sa structure mésoporeuse ordonnée après avoir été en contact avec l'eau même à température ambiante. Le vieillissement à 130 °C, avec ajout de sels inorganiques, a abouti à des matériaux qui ont maintenu leur structure mésoporeuse sous différents traitements en présence d'eau. Le matériau synthétisé en présence de KCl a été utilisé comme adsorbant pour le reste du travail de cette thèse. Il a été démontré que l'effondrement de la structure observé dans la SBA-15 modifiée aux amines, préparée par la méthode conventionnelle en contact avec des solutions aqueuses est associé avec le processus de séchage, et non le traitement lui-même. Cet effondrement de structure a été évité en remplaçant l'eau avec des liquides plus volatils tels que l'acétone, avant le séchage. La SBA-15 amino-fonctionnalisée a été testée pour l'élimination des ions de cuivre des solutions aqueuses à différentes températures, pH, concentrations initiales et vitesses d'agitation. Les résultats obtenus ont indiqué que la SBA-15 amino-fonctionnalisée était très efficace et l'équilibre a été atteint en moins de 30 min à température ambiante. La capacité d'adsorption a considérablement augmenté avec la température, la concentration initiale de cuivre et le pH. Sous des conditions appropriées, le matériau a manifesté une grande capacité d'adsorption, même à des concentrations très faibles en cuivre. Afin d’étudier l'effet des paramètres d'adsorption, un plan factoriel de 24 expériences a été utilisé pour dépister les facteurs affectant l'efficacité d'élimination du cuivre. Tous les effets principaux des paramètres étaient importants à 95% de niveau de confiance. La méthodologie de la surface composite a été utilisée pour développer un modèle fiable qui représente le processus d'adsorption. Les tests statistiques utilisés ont prouvé la pertinence du modèle de second ordre. L’optimisation des niveaux des facteurs a été effectuée et les conditions optimales recommandées sont: la concentration en cuivre de 20 mg/L, le rapport adsorbant/solution de 1.57 g/L, pH de 6.5 et T = 294 K pour l'élimination de 95% de cuivre. L'effet des conditions de régénération a été étudié après trois cycles d'adsorption-désorption, sous différentes conditions de régénération. En utilisant la méthodologie de la surface composite, l'effet des conditions de régénération sur la performance de l'adsorbant a été étudié. Il a été constaté que tous les paramètres étudiés ont une influence statistiquement significative sur la capacité de travail d'adsorption. En ce qui concerne les propriétés structurelles et la teneur en amine, aucun des facteurs n’a été jugé significatif. La régénération à l'aide d'EDTA a été jugée plus efficace que le traitement acide. La SBA-15 amino-fonctionnalisée a été étudiée comme absorbant potentiel de Cd2+, Co2+, Cu2+, Zn2+, Pb2+, Ni2+, Al3+ and Cr3+. La capacité d'adsorption et la sélectivité du matériau ont été étudiées dans des solutions mono- et multi-métalliques. En utilisant des solutions très diluées, soit 10 ppm, plus de 95% de cations ont été enlevés, sauf pour le Co2+ et Cr3+, indiquant la forte sensibilité de l'adsorbant. Les capacités d'adsorption dans les solutions multi-métalliques étaient inférieures à celles des solutions mono-métalliques en raison de la concurrence entre les éléments métalliques pour les groupes amine. L'adsorbant n'a pas été affecté par la présence de sodium, de potassium et de calcium, ce qui indique que la force ionique n'affecte pas les propriétés d'adsorption. L’usage avec succès de ce matériau pour éliminer le cuivre dans l'eau de robinet, l’eau de rivière et les eaux usées de galvanoplastie a été démontré. Des expériences dynamiques ont été réalisées sur l'adsorption des ions de cuivre par la SBA-15 amine-modifiée sur une colonne à lit fixe de laboratoire. Les courbes de perçage ont été analysées à des débits différents et après deux cycles d'adsorption-désorption. De plus, un modèle basé sur le bilan de matière a été développé et testé pour prédire les courbes de perçage sous les différentes conditions expérimentales utilisées. Les résultats suggèrent que le modèle développé est en bon accord avec les données expérimentales. La régénération du lit a été réalisée en faisant circuler une solution EDTA à 0.2 M à travers la colonne pendant 30 min.

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13

Rejaldien, Moegamat Zain. "Base metal equilibrium prediction on ion exchange resin". Thesis, Cape Technikon, 2002. http://hdl.handle.net/20.500.11838/875.

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Thesis (MTech (Chemical Engineering)--Cape Technikon, Cape Town, 2002
This study is the first phase of an investigation into an alternative process to recover base metals from solution, namely ion exchange. An identified ion exchange resin was employed to study the recovery of copper, nickel and cobalt from electrolytic solutions. The main focus of the investigation was the prediction of equilibrium conditions in this multi-component system using a batch configuration. In order to predict equilibrium conditions. existing multi-component isotherms such as Fritz and Schleunder were tested. It has been shown that traditional isothem15 did not accurately predict equilibrium conditions. hence the need for development of new isotherms. Essentially two approaches were followed in the development of new isotherms namely. an effective concentration approach as well as a heat transfer approach. Both yielded positive outcomes with the effective concentration approach proving to be the most accurate. In addition to these two approaches a thermodynamical approach was also tested which also showed favourable predictions for Cu loading

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14

Chakraborty, Suman. "Studies On Momentum, Heat And Mass Transfer In Binary Alloy Solidification Processes". Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/287.

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The primary focus of the present work is the development of macro-models for numerical simulation of binary alloy solidification processes, consistent with microscopic phase-change considerations, with a particular emphasis on capturing the effects of non-equilibrium species redistribution on overall macrosegregation behaviour. As a first step, a generalised macroscopic framework is developed for mathematical modelling of the process. The complete set of equivalent single-phase governing equations (mass, momentum, energy and species conservation) are solved following a pressure-based Finite Volume Method according to the SIMPLER algorithm. An algorithm is also developed for the prescription of the coupling between temperature and the melt-fraction. Based on the above unified approach of solidification modelling, a macroscopic numerical model is devised that is capable of capturing the interaction between the double-diffusive convective field and a localised fluid flow on account of solutal undercooling during non-equilibrium solidification of binary alloys. Numerical simulations are performed for the case of two-dimensional transient solidification of Pb-Sn alloys, and the simulation results are also compared with the corresponding experimental results quoted in the literature. It is observed that non-equilibrium effects on account of solutal undercooling result in an enhanced macrosegregation. Next, the model is extended to capture the effects of dendritic arm coarsening on the macroscopic transport phenomena occurring during a binary alloy solidification process. The numerical results are first tested against experimental results quoted in the literature, corresponding to the solidification of an Al-Cu alloy in a bottom-cooled cavity. It is concluded that dendritic arm coarsening leads to an increased effective permeability of the mushy region as well as an enhanced eutectic fraction of the solidified ingot. Consequently, an enhanced macrosegregation can be predicted as compared to that dictated by shrinkage-induced fluid flow alone. For an order-of-magnitude assessment of predictions from the numerical models, a systematic approach is subsequently developed for scaling analysis of momentum, heat and species conservation equations pertaining to the case of solidification of a binary mixture. A characteristic velocity scale inside the mushy region is derived, in terms of the morphological parameters of the two-phase region. A subsequent analysis of the energy equation results in an estimation of the solid layer thickness. It is also shown from scaling principles that non-equilibrium effects result in an enhanced macro-segregation compared to the case of an equilibrium model For the sake of assessment of the scaling analysis, the predictions are validated against computational results corresponding to the simulation of a full set of governing equations, thus confirming the trends suggested by the scale analysis. In order to analytically investigate certain limiting cases of unidirectional alloy solidification, a fully analytical solution technique is established for the solution of unidirectional, conduction-dominated, alloy solidification problems. The results are tested for the problem of solidification of an ammonium chloride-water solution, and are compared with those from existing analytical models as well as with the corresponding results from a fully numerical simulation. The effects of different microscopic models on solidification behaviour are illustrated, and transients in temperature and heat flux distribution are also analysed. An excellent agreement between the present solutions and results from the computational simulation can be observed. The generalised numerical model is subsequently utilised to investigate the effects of laminar double-diffusive Rayleigh-Benard convection on directional solidification of binary fluids, when cooled and solidified from the top. A series of experiments is also performed with ammonium chloride-water solutions of hypoeutectic and hypereutectic composition, so as to facilitate comparisons with numerical predictions. While excellent agreements can be obtained for the first case, the second case results in a peculiar situation, where crystals nucleated on the inner roof of the cavity start descending through the bulk fluid, and finally settle down at the bottom of the cavity in the form of a sedimented solid layer. An eutectic solidification front subsequently progresses from the top surface vertically downwards, and eventually meets the heap of solid crystals collected on the floor of the cavity. However, comparison of experimental observations with corresponding numerical results from the present model is not possible under this situation, since the associated transport process involves a complex combination of a number of closely interconnected physical mechanisms, many of which are yet to be resolved. Subsequent to the development of the mathematical model and experimental arrangements for macroscopic transport processes during an alloy solidification process, some of the important modes of double-diffusive instability are analytically investigated, as a binary alloy of any specified initial composition is directionally solidified from the top. By employing a close-formed solution technique, the critical liquid layer heights corresponding to the onset of direct mode of instability are identified, corresponding two a binary alloy with three different initial compositions. In order to simulate turbulent transport during non-equilibrium solidification processes of binary alloys, a modified k-8 model is subsequently developed. Particular emphasis is given for appropriate modelling of turbulence parameters, so that the model merges with single-phase turbulence closure equations in the pure liquid region in a smooth manner. Laboratory experiments are performed using an ammonium chloride-water solution that is solidified by cooling from the top of a rectangular cavity. A good agreement between numerical and experimental results is observed. Finally, in order to study the effects of three-dimensionality in fluid flow on overall macrosegregation behaviour, the interaction between double-diffusive convection and non-equilibrium solidification of a binary mixture in a cubic enclosure (cooled from a side) is numerically investigated using a three-dimensional transient mathematical model. Investigations are carried out for two separate model systems, one corresponding to a typical metal-ally analogue system and other corresponding to an actual metal-alloy system. As a result of three-dimensional convective flow-patterns, a significant solute macrosegregation is observed in the transverse sections of the cavity, which cannot be captured by two-dimensional simulations.

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15

Ekengård, Johan. "Aspects on slag/metal equilibrium calculations and metal droplet characteristics in ladle slags". Licentiate thesis, KTH, Materials Science and Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1788.

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In the present work the mixing between the metal and slagphase during the ladle refining process from tapping from theelectric arc furnace to casting in two different Swedish steelplants has been studied.

Three slag models and the sulphur-oxygen equilibrium betweenslag and steel was used together with the dilute solution modelfor the liquid steel phase to predict the equilibrium oxygenactivity in steel bulk and metal droplets in top slag inequilibrium with the top slag. The predicted oxygen activitieswere compared with measured oxygen activities from the steelbulk. The results show significant discrepancies between thecalculated and measured oxygen activities and the reasons forthe differences are discussed.

Metal droplet distribution in slag samples have also beendetermined using classification according to the Swedishstandard SS111116. It was found that most metal droplets arefound in the slag samples taken before vacuum degassing. Thetotal area between steel droplets and slag has been determinedto be 3 to 14 times larger than the projected flat interfacearea between top slag and steel. The effect of slag viscosityand reactions between steel and slag on the metal dropletformation in slags is also discussed.

The chemical composition of the metal droplets in the topslag was determined and possible reactions taking place betweenthe steel droplets and the slag was studied. Differencesbetween steel droplet compositions and the bulk steelcomposition are discussed. The results show significantdifferences between steel droplet and bulk steelcomposition.

Key words:oxygen activity, metal droplets, sulphur,slag, ladle, refining, distribution.

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16

Chen, Jiaping. "Sorption of metal ions from aqueous solutions : equilibrium, kinetics, and transport". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/21467.

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17

Welter, Rosilene Andrea. "Estudo do equilibrio dos sistemas binarios e ternario de troca ionica dos ions cobre, cadmio e calcio pelo biopolimero alginato". [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267090.

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Orientadores: Meuris Gurgel Carlos da Silva, Edson Antonio da Silva
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-13T05:52:33Z (GMT). No. of bitstreams: 1 Welter_RosileneAndrea_M.pdf: 2156279 bytes, checksum: 6cee14e80d11df1707c2f90723d31b09 (MD5) Previous issue date: 2009
Resumo: Neste trabalho, estudou-se o processo de troca iônica envolvendo os íons Cobre, Cádmio e Cálcio, sendo que os metais pesados, Cobre e Cádmio, foram avaliados devido a alta toxicidade, à sua presença em efluente industriais e a dificuldade na sua remoção quando em baixas concentrações, entretanto, acima do permitido pela legislação vigente. O trocador iônico utilizado foi o Alginato, que na presença de íons divalentes possui a capacidade de gelificar-se formando partículas aptas à utilização em operações de troca iônica. As partículas foram obtidas por diferentes formas: gotejamento, atomização ou ainda, emulsificação, contudo, cada método apresentou partículas com propriedades físicas distintas. O método de emulsificação resultou em partículas com diâmetro e granulometria satisfatórios para o processo de troca iônica em leito poroso, além de, dentre os métodos analisados, apresentar maior capacidade de troca iônica para o ensaio realizado em banho finito sob as mesmas condições operacionais. Portanto, os ensaios de equilíbrio de troca iônica para os sistemas binários envolvendo os íons Cu-Ca, Cd-Ca e Cu-Cd e para o ensaio ternário Cu-Cd-Ca, foram realizados em leito poroso, utilizando partículas obtidas por emulsificação, a vazão de 3 mL/min e pH de 4,5, sendo estes parâmetros operacionais definidos por estudos prévios. Os dados experimentais para os sistemas binários foram avaliados utilizando Isotermas de Adsorção Monocomponente que apresentaram comportamento satisfatório, entretanto os modelos de Isotermas de Adsorção Binária apresentaram melhor ajuste. O tratamento dos sistemas binários utilizando LAM Ideal e LAM, foram satisfatórios para o comportamento dos dados experimentais, entretanto, houve uma variação considerável do valor de Keq. Os coeficientes de atividade envolvendo os íons ligados a fase sólida apresentaram-se próximos a 1, ou seja, o sistema Metal-Alginato, está próximo à idealidade. O sistema ternário apresentou resultado insatisfatório para seu tratamento utilizando Isotermas de Adsorção Binária e o modelo Preditivo de LAM, sendo que apenas os modelos de Isotermas de Adsorção Ternária, Langmuir 4 parâmetros, Langmuir 6 parâmetros e Langmuir-Freundlich apresentaram resultados satisfatórios.
Abstract: In this work, it was studied the ion exchange process involving copper, cadmium and calcium ions. The heavy metals, copper and cadmium, were evaluated due to its high toxicity, its presence in industrial effluent and difficulty in its removal when in low concentrations, however, above permitted levels by law. Alginate was used as ionic exchanger. In the presence of high affinity ions, such as calcium, it has the ability to gelate and form rigid particles which are suitable for ion exchange operations. These particles were obtained from different methods, such as dripping, atomization and emulsification, however, each method resulted in particles with different physical properties. Emulsification method resulted in particles of suitable diameter and size for the ion exchange process in porous bed. Among the considered methods, it showed to be the one with higher ion exchange capacity, under the same operating conditions, for batch system experiments. Therefore, ion exchange equilibrium experiments for binary systems, involving Cu-Ca, Cd-Ca and Cu-Cd ions, and ternary system Cu-Cd-Ca, were conducted in porous bed, using particles obtained by emulsification, at a flow rate of 3 mL/min and pH 4.5. These operational parameters were defined by previous studies. Binary systems experimental data were evaluated using monocomponent adsorption isotherms, which showed good behavior, however, binary adsorption isotherms models showed higher accuracy. Binary systems treatment using Ideal LAM and LAM, were satisfactory for the experimental data behavior, however, there was a considerable variation in Keq values. Activity coefficients involving ions attached to the solid phase were close to 1, which means that the alginate-metal system is close to ideality. The ternary system showed unsatisfactory results for its treatment using binary adsorption isotherms and LAM predictive model, where just ternary adsorption isotherms, Langmuir 4 parameters, Langmuir 6 parameters and Langmuir-Freundlich models showed satisfactory results.
Mestrado
Engenharia de Processos
Mestre em Engenharia Química

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18

Elofsson, Viktor. "Nanoscale structure forming processes : Metal thin films grown far-from-equilibrium". Doctoral thesis, Linköpings universitet, Nanodesign, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-132895.

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Thin film growth from the vapor phase has for a long time intrigued researchers endeavouring to unravel and understand atomistic surface processes that govern film formation. Their motivation has not been purely scientific, but also driven by numerous applications where this understanding is paramount to knowledge-based design of novel film materials with tailored properties. Within the above framework, this thesis investigates growth of metal films on weakly bonding substrates, a combination of great relevance for applications concerning e.g., catalysis, graphene metallization and architectural glazing. When metal vapor condenses on weakly bonding substrates three dimensional islands nucleate, grow and coalesce prior to forming a continuous film. The combined effect of these initial growth stages on film formation and morphology evolution is studied using pulsed vapor fluxes for the model system Ag/SiO2. It is shown that the competition between island growth and coalescence completion determines structure evolution. The effect of the initial growth stages on film formation is also examined for the tilted columnar microstructure obtained when vapor arrives at an angle that deviates from the substrate surface normal. This is done using two metals with distinctly different nucleation behaviour, and the findings suggest that the column tilt angle is set by nucleation conditions in conjunction with shadowing of the vapor flux by adjacent islands. Vapor arriving at an angle can in addition result in films that exhibit preferred crystallographic orientations, both out-of-plane and in-plane. Their emergence is commonly described by an evolutionary growth model, which for some materials predict a double in-plane alignment that has not been observed experimentally. Here, an experiment is designed to replicate the model’s growth conditions, confirming the existence of double in-plane alignment. New and added film functionalities can further be unlocked by alloying. Properties are then largely set by chemistry and atomic arrangement, where the latter can be affected by thermodynamics, kinetics and vapor flux modulation. Their combined effect on atomic arrangement is here unravelled by presenting a research methodology that encompasses high resolution vapor flux modulation, nanoscale structure v vi probes and growth simulations. The methodology is deployed to study the immiscible Ag-Cu and miscible Ag-Au model systems, for which it is shown that capping of Cu by Ag atoms via near surface diffusion processes and rough morphology of the Ag-Au growth front are the decisive structure forming processes in each respective system. The results generated in this thesis are of relevance for tuning structure of metal films grown on weakly bonding substrates. They also indicate that improved growth models are required to accurately describe structure evolution and emergence of a preferred in-plane orientation in films where vapor arrives at an angle that deviates from the substrate surface normal. In addition, this thesis presents a methodology that can be used to identify and understand structure forming processes in multicomponent films, which may enable tailoring of atomic arrangement and related properties in technologically relevant material systems.

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19

Assis, Andre N. "The Phosphorus Reaction in Oxygen Steelmaking: Thermodynamic Equilibrium and Metal Droplet Behavior". Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/464.

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Low phosphorus content steels are essential for steel applications where high ductility is required, such as thin sheets, deep drawn, pipelines and automobile exteriors. In the past, phosphorus control was not considered a big challenge in steel production in the US because iron ores with low phosphorus contents were readily available and considered cheap. However, in the last decade, the iron ore price has risen by roughly 400% and lower cost iron sources generally have higher phosphorus content. In integrated steel plants, phosphorus removal usually takes place during the oxygen steelmaking process (OSM) but in Japan a intermediate step for hot metal dephosphorization is commonly used. There are various types of OSM furnaces but the most widely used remains the top-blown Basic Oxygen Furnace (BOF). The BOF slag can be recycled to a sinter plant or directly to the blast furnace, ultimately increasing the phosphorus input in the process. In order to meet new demands for phosphorus control, it is necessary to improve our understanding on the thermodynamics and kinetics of the phosphorus partitioning reaction between slag and metal melts during steelmaking. Therefore, the present work has been divided in three strongly correlated sections: phosphorus equilibrium between metal and slag; analysis of plant data; and observations of the reaction kinetics. Phosphorus equilibrium between liquid metal and slag has been extensively studied since the 1940's. It is well known that CaO and FeO are the main slag constituents that help promote dephosphorization. On the other hand, dephosphorization decreases with temperature due to the endothermic nature of the reaction. Many correlations have been developed to predict the phosphorus partition ratio as a function of metal and slag composition as well as temperature. Nevertheless, there are still disagreements in the laboratory data and the equilibrium phosphorus partition can be predicted with an uncertainty of a factor of up to 5. The first part of the present work focuses on generating more reliable equilibrium data for BOF-type slags by approaching equilibrium from both sides of the reaction. The experimental results were combined with two other sets of data from different authors to produce a new correlation that includes the effect of SiO2 on the phosphorus partition coefficient, LP . Although the quantification of phosphorus equilibrium is extremely important, most industrial furnaces do not operate at equilibrium, usually due to liquid slag formation, kinetics and time constraints. Thus, it is important to know how close to equilibrium different furnaces operate in order to suggest optimal slag compositions to promote dephosphorization. The present work analyzed four large sets of data containing the chemical compositions of both slag and metal phase as well as the tapping temperature of each heat. Each set of data corresponded to different furnaces: one AOD (Argon Oxygen Decarburization), two top-blown BOFs and one Q-BOP or OBM. It was found that the bulk slag composition can greatly \mask" the data due to solid phases coexisting with the liquid slag. The author used the software package FactSage to estimate the amount of solids in the slag and liquid slag composition. It was found that the AOD is the reactor closest to equilibrium, followed by the Q-BOP (OBM) and the two top-blown BOFs. It was noted that the stirring conditions and slag composition are two key variables to enable optimum phosphorus removal. Also, over saturating the slag with CaO and MgO does not seem to benefit the process to any extent. Lastly, interesting observations on the behavior of small metal droplets reacting with slag are presented and discussed. It was found that dynamic interfacial phenomena at the metal-slag interface is likely to play a significant role in the kinetic behavior of the system, due to the exchange of surface active elements, such as oxygen, which dramatically lowers the interfacial tension and cause spontaneous emulsification. Although this phenomenon has been studied, actual quantification of changes in interfacial area remain a challenge. The author developed an experimental method to enable better quantification of spontaneous emulsification and two sets of experiments were carried. One with an Fe containing 0.2 wt.% P and another in a P-free system where pure iron was oxidized. It was found that phosphorus did not play a role in spontaneous emulsification and it was rapidly removed before the onset of dynamic interfacial phenomena. Emulsificaion was maybe caused by de-oxidation of the metal after phosphorus removal took place and the metal became super saturated with oxygen by an unknown reason. The estimated surface area rapidly increases by over an order of magnitude during the beginning and intermediate periods of the reaction. The metal drop breaks into hundreds of small droplets, effectively emulsifying the metal into the slag. With time, the surface area decreases and the metal droplets coalesce. Similar results were observed for an Fe droplet being oxidized. Spontaneous emulsification takes place regardless of the direction of oxygen transfer and the changes in surface area are similar for both cases. The last chapter describes the industrial relevance of the present work, summarizes the findings, revisits the hypotheses and presents potential future work where further research is encouraged.

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20

Chamupathi, Virittamulla Gamage. "Role of the interface in metal solvent extraction kinetics". Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184256.

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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.

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21

Kuo, Long-Sheng 1969. "Non-equilibrium energy transfer and phase change during intense picosecond laser-metal interactions". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/34346.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
Includes bibliographical references (leaves 55-57).
Laser interactions with metals involve absorption of photon energy by electrons, energy coupling between electrons and the lattice, and energy transport by diffusion of electrons and lattice vibrations. During picosecond laser irradiation of metal films, electrons and the lattice are not in thermal equilibrium. On the other hand, rapid laser heating produces a large degree of superheating and undercooling during melting and solidification. First, this work investigates experimentally non-equilibrium heating processes during intense picosecond laser heating of metal films. Results show excellent agreement with predictions of the two-step radiation heating model. Second, this work develops a general model to characterize both non-equilibrium energy deposition and phase change processes. The predictions show that the non-equilibrium heating processes significantly increase the laser melting threshold, enlarge the thermal-affected region, reduce the lattice temperature rise, prolong the phase change duration, and reduce the solidification speed. These results are important for materials processing using ultrashort pulsed lasers.
by Long-Sheng Kuo.
S.M.

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22

Kelly, Mark Joseph. "Metal ion equilibria in biofluids - copper and rheumatoid arthritis". Doctoral thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/9584.

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Includes bibliographies.
A computer model of blood plasma has been used to evaluate the factors affecting the ability of a ligand to increase the low molecular weight copper pool in vivo. The justification for using this speciation approach is based on the assumption that the low molecular weight copper complexes are important in the reduction of the inflammation associated with rheumatoid arthritis. Based on the results of the simulation, two novel ligands, 3,6,9, 12-tetra-azatetradecanedioic acid (dtda) and 3,6,9,-triazaundecanedioic acid (dtda) have been synthesised using a three step route. Multiple carboxylation was prevented by using the tosylate protecting group. The compounds were obtained in an overall yield of 14.7 and 29.0 , respectively, and characterised using n.m.r, l.R. and mass spectrometry. The stability constants of the complexes formed by these ligands with several metal-ions were determined using glass electrode potentiometry at 25°C and an ionic strength of 0.15 mol dm3. The metals used were the divalent ions of magnesium, calcium, manganese, cobalt, nickel, copper and zinc. The values determined followed the Irvine-Williams order of stability.

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23

Contreras, Mellado Álvaro Andrés y Cortez Bryan Richard Gutiérrez. "Efectos de ciclos de precios de metales : estimación de un modelo de equilibrio general con time to build para la economía peruana, 2001-2015". Master's thesis, Universidad del Pacífico, 2016. http://hdl.handle.net/11354/1210.

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En el presente documento se estudia el desempeño que ha tenido Perú durante la última fase expansiva del ciclo de precios de commodities, específicamente entre los años 2001 y 2015. Para esto, se desarrolla un modelo de equilibrio general estocástico y dinámico, basado en Medina y Soto (2007) y Fornero y Kichner (2014), que incorpora un sector productor de commodities con inversión del tipo time to build. El modelo es estimado de forma lineal y a partir de este se muestra la importancia que tienen los choques de precios commodities sobre el resto de la actividad económica. Asimismo, se analizan distintos tipos de políticas fiscales y monetarias, ante este tipo de choques. También se obtienen políticas monetarias óptimas a partir de la función de pérdida de la autoridad monetaria. Los resultados de la investigación apuntan a que, cuando hay un incremento en el precio de los commodities, se genera una dinámica procíclica en el valor de la producción de todos los sectores, en la inversión, el consumo y el gasto del Gobierno. Además, se encuentra que la incorporación del mecanismo de time to build permite explicar mejor la dinámica observada. Dicho mecanismo ayuda a comprender que el choque en cuestión demora en propagarse, ya que los proyectos mineros toman tiempo en construirse. Este aporte metodológico es de particular relevancia en los ejercicios de modelamiento y predicción que se quieran realizar sobre la economía peruana.

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Xu, Kangcheng. "Raman spectroscopic studies of phase equilibria in binary monovalent metal nitrates". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25781.pdf.

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Duck, Matthew James William. "Solution equilibria of some multidentate phenolic ligands and their metal complexes". Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46286.

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Gallagher, Andrew James. "Modelling barium isotopes in metal-poor stars". Thesis, University of Hertfordshire, 2012. http://hdl.handle.net/2299/9224.

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The principal theory concerning the origin of the elements heavier than the Fe-peak, such as Ba, strongly suggest that for old, metal-poor environments, the rapid (r-) process is the most likely path taken in their synthesis, while the slow (s-) process becomes more substantial in younger, more metal-rich stellar populations. In this work I test this theory by evaluating the isotope ratios of Ba. It is understood that Ba consists of seven stable isotopes, five of which are synthesised by the two neutron-capture processes. The two odd isotopes, 135,137Ba, as well as 138Ba are synthesised via both the r- and s-processes while two of the even isotopes, 134,136Ba are synthesised via the s-process only. The relative contribution of the r- and s-process to these isotopes can be understood via nucleosynthesis calculations and is described using the parameter fodd, where fodd = [N (135Ba) + N (137Ba)] /N (Ba). Low values of fodd (~0.11) indicate an s-process regime, while high values of fodd (~0.46) indicate an r-process regime. In the Ba II 4554 A line the even isotopes lie close to the line centre, while the odd isotopes, which are hyperfine split because of their non-zero nuclear spin, lie in the wings of the line. From an analysis of the line profile shape, one can determine whether Ba has been synthesised primarily through the r-process or s-process; a broad, asymmetric line would indicate a high r-process contribution, while a line with a deeper core and shallower wings would indicate a high s-process contribution. Using the radiative transfer code ATLAS, which assumes local thermodynamic equilibrium (LTE) and employs 1-dimensional (1D) KURUCZ06 model atmospheres, I synthesised line profiles for six metal-poor stars: HD140283, HD122563, HD88609, HD84937, BD-04 3208 and BD+26 3578 - for a range of isotope ratios. All six are of sufficiently low metallicity that Ba was expected to have an r-process origin. These were fit to high resolution (R\equiv \lamda/\Delta\lamda = 90 000 - 95 000), high signal-to-noise to the Ba II 4554 A line which has multiple components. In the first test, synthetic spectra were computed using the non local thermodynamic equilibrium (NLTE) radiative transfer code MULTI. The synthetic line profiles were fit to a number of lines in HD140283. Although this technique might have improved the fit in the line core, it was found that such a treatment did not improve upon fitting errors associated with the best fit 1D LTE synthetic profiles. The second test used a 3-dimensional (3D) radiative transfer code (LINFOR3D) that employed 3D, time-dependent atmospheres produced with CO5BOLD. The 3D synthetic pro les were fit to a selection of Fe lines and improvements over the poor fits produced by the 1D LTE synthesis were seen. It was found that the 3D synthesis could almost completely reproduce the line asymmetries seen in the observed stellar spectrum. This result suggests that further work to refine the 3D calculations and synthesis code would be valuable.

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27

Khare, Neeraj Prasad. "Predictive Modeling of Metal-Catalyzed Polyolefin Processes". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11065.

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This dissertation describes the essential modeling components and techniques for building comprehensive polymer process models for metal-catalyzed polyolefin processes. The significance of this work is that it presents a comprehensive approach to polymer process modeling applied to large-scale commercial processes. Most researchers focus only on polymerization mechanisms and reaction kinetics, and neglect physical properties and phase equilibrium. Both physical properties and phase equilibrium play key roles in the accuracy and robustness of a model. This work presents the fundamental principles and practical guidelines used to develop and validate both steady-state and dynamic simulation models for two large-scale commercial processes involving the Ziegler-Natta polymerization to produce high-density polyethylene (HDPE) and polypropylene (PP). It also provides a model for the solution polymerization of ethylene using a metallocene catalyst. Existing modeling efforts do not include physical properties or phase equilibrium in their calculations. These omissions undermine the accuracy and predictive power of the models. The forward chapters of the dissertation discuss the fundamental concepts we consider in polymer process modeling. These include physical and thermodynamic properties, phase equilibrium, and polymerization kinetics. The later chapters provide the modeling applications described above.
Ph. D.

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28

Doostmohammadi, Hamid. "A Study of Slag/Metal Equilibrium and Inclusion Characteristics during Ladle Treatment and after Ingot Casting". Doctoral thesis, KTH, Materialvetenskap, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11596.

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Today, there is a high demand on clean steel for high performance materialproperties. Thus, steel producers try to deliver a steel product with the highestquality and cleanliness to the market. The number of parameters that affect thesteel cleanliness may vary depending on the required material properties of thefinal product. However, the non-metallic inclusion characteristics represent one ofthe most important parameters. More specifically, the composition, size, numberand morphology affect steel cleanliness. In this work, selected parameters affectingthe inclusion characteristics were studied using the following methods: i)thermodynamic calculations (including computational thermodynamiccalculations), ii) inclusion determinations using a cross sectional (CS) method (2Dinvestigations) and iii) inclusion determinations using an electrolytic extraction(EE) method (3D investigations). The computational thermodynamic calculations of the slag-steel and inclusion-steelequilibriums were carried out using the Thermo-Calc software. With the help ofthese calculations, the influence of the slag carryover on the top slag, aluminumcontent in steel and sulfur distribution ratio as well as predictions of stable phasesof inclusions were studied. In addition, inclusion determinations of tool steel gradesamples collected during various stages of the ladle treatment in a scrap-based steelplant were carried out using both 2D and 3D methods. Furthermore, inclusiondeterminations of bearing steel grade samples from a runner system after ingotcasting were performed using a 2D metallographic method (CS-method). Also, theINCAFeature software was used, when using cross sectional method, in order tocollect more statistics of the inclusion characteristics. It was found that slag carryover has a large influence on the composition of theactual top slag as well as the aluminum content in the steel as well as the sulfurdistribution ratio. In addition, steel and slag were found to be in “near”-equilibriumconditions, after the completion of the vacuum degassing operation. Furthermore,the composition of small-size inclusions in samples taken from tool steel was foundto be very scattered. Moreover, the composition of the large-size inclusions wasfound to be less scattered. Furthermore, closer to the top slag composition insamples collected after vacuum degassing. Finally, the accuracy of the inclusioncomposition determinations of tool steel samples using the electrolytic extractionmethod was found to be better than for the cross sectional method. The worseaccuracy of the CS-method is due to a considerable effect of matrix elements oninclusion composition.
QC 20100709

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29

Anttila, Raimo. "Complexation thermodynamics of aluminum, beryllium, dioxouranium, and lanthanoids with ligands containing hard donor atoms". Oulu, Finland : Dept. of Chemistry, University of Oulu, 1992. http://catalog.hathitrust.org/api/volumes/oclc/35165443.html.

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Subramaniam, Kavitha. "Metal uptake and its effects on colloidal particle interactions : equilibria and rates". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/20206.

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Matthews, Kelly E. "Elucidation of the aqueous equilibrium system of IrH₂(PMe₃)₃Cl and periodic trends of the iridium (III) dihydrido tris(trimethylphosphino) series, IrH₂(PMe₃)₃X". Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164037/.

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Resende, Luis Manuel Vieira Soares de. "Solid <-> solution equilibria of cadmium and zinc in a contaminated Derbyshire woodland". Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286246.

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33

Vu, Quang Huy Verfasser], Karina [Gutachter] [Morgenstern y Ulrich [Gutachter] Köhler. "Nanostructure kinetics far from equilibrium on noble metal surfaces / Quang Huy Vu ; Gutachter: Karina Morgenstern, Ulrich Köhler". Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1116709783/34.

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34

Tsai, Suh-Jen Jane. "Equilibrium and kinetic studies of metal ion promoted hydration and enolization reactions of oxaloacetate in various buffers : the cooperativity with base catalysts /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487258254024045.

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Zambon, Gicela Ana. "Remoção de chumbo (Pb2+) utilizando zeolita natural clinoptilolita". [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267461.

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Orientadores: Telma Teixeira Franco, Meuris Gurgel Carlos da Silva
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Uma das grandes preocupações mundiais atuais é a qualidade das águas, pois o atual nível de avanço populacional e industrial tem causado grande poluição em rios e demais corpos d'água. Neste sentido, várias tecnologias têm sido propostas para descontaminação da água. O processo estudado pelo presente trabalho baseia-se na adsorção de chumbo, um metal pesado altamente tóxico, presente em efluentes industriais, urbanos e de mineração, por meio da troca iônica em materiais adsorventes naturalmente ocorrentes como as zeólitas. A investigação consistiu na avaliação da capacidade de adsorção, Q (mg Pb2+/g zeólita), da zeólita natural c1inoptilolita em sistema de banho finito, utilizando a técnica de planejamento fatorial 23 completo com ponto central. As três variáveis foram: concentração inicial de chumbo de 200 a 600 mg/L, massa de adsorvente de 1,0 a 2,0 g e pH da solução de 3,0 a 5,0. Concentração e massa foram expressas na forma de um único fator chamado R que representou a quantidade potencial de chumbo disponível por massa de zeólita, resultando entre 20 e 120 mg Pb2+/g zeólita. Foram obtidas a cinética e a isoterma de adsorção para estas condições. A metodologia indicou a que a capacidade de adsorção depende da concentração e da massa e independe do pH e que maiores capacidades de remoção são obtidas elevando-se a concentração de. chumbo e diminuindo-se a massa de zeólita, ou seja, com maiores valores de R. Foi estudada também a capacidade de adsorção de chumbo pela zeólita c1inoptilolita em coluna de leito fixo. Neste sistema foi investigado o efeito da vazão da solução de chumbo (10 a 50 rnL/min) em alta concentração (1000 mg/L) e da granulometria do adsorvente (diâmetro médio entre 0,55 e 0,78 mm) sobre a capacidade de adsorção. Com o leito fixo, obteve-se as curvas de ruptura do sistema em diferentes vazões e diâmetro de partícula. A técnica de planejamento fatorial utilizada demonstrou que o diâmetro da zeólita não influencia na capacidade de remoção da mesma, e que vazões baixas propiciam maiores remoções. A operação de dessorção da zeólita também foi possível no leito fixo, mostrando o potencial de reutilização da mesma. Uma modelagem matemática foi feita a fim de obter uma equação empírica que reproduzisse a curva de ruptura para diversas vazões dentro da faixa de dados experimentais disponível, obtendo-se uma equação com alta capacidade de previsão de resultados. Palavras chaves: adsorção, chumbo, zeólita, banho finito, leito fixo
Abstract: The quality of water is a matter of increasing concern as the current population and industrial growth results in pollution of rivers and other water reservoirs. Thus, several technologies have been proposed to perform water decontamination. The process studied in this work is based on the adsorption of lead, which is a highly toxic heavy metal present in industrial, domestic and mining wastewater, by mean of ion exchange in adsorptive materials, such as natural zeolites. The work consists of the evaluation of the clinoptilolite zeolite adsorption capacity, Q (mg Pb2+/g zeolite), in batch equilibrium, utilizing a full experimental design 23 with central point. The three variables studied were: initiallead concentration (200, 400, 600 mg/L), adsorbent mass (1.0, 1.5, 2.0 g) and pH solution (3.0, 4.0, 5.0). Concentration and mass are expressed by a unique factor called R, representing the lead potential quantity available per mass of adsorber, with values between 20 and 120 mg Pb2+/g zeolite. For these conditions, adsorption kinetics and isothermal were obtained. The results suggested that the adsorption capacity depends on concentration and mass and not of the pH, in order that, the higher the removal capacity, the greater the lead initial concentration and the minor zeolite mass, e.g., the greater R-values. The adsorption isotherm was compared with the Langmuir and Freundlich adsorption models, being better adjusted by the former. The capacity of the c1inoptilolite zeolite to remove lead in a fixed bed was also studied. The effects of the high eoneentration lead solution (1000 mg/L) flow rate (10, 30, 50 mL/min), and the zeolite grain size (mean diameters: 0.55, 0.65, 0.78 mm) in the adsorption capacity was examined. The breakthrough eurves for different flow rates and partic1e diameters were obtained. The experimental design technique showed that zeolite removal capacity does not depend on the partic1e diameter and that low flow rates increase its eapaeity. The zeolite desorption in fixed bed was also possible, showing the possibility of reusing this zeolite. Mathematieal modeling provided an empiric function that was able to describe the breakthrough curve for the several flow rates in the range defined by the available experimental data, and this equation showed a high eapaeity to forecast results
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química

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36

Kara, Ufuoma Israel. "EFFECT OF HISTORY ON THE BINARY ADSORPTION EQUILIBRIA OF ALUMINIUM TEREPHTHALATE (MIL-53(Al))". Cleveland State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=csu1537362855278708.

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Rocha, Silvia Regina Santos. "Procedimentos e avaliação química de parâmetros de interesse nutricional de espinafre comercializado na Bahia". Programa de Pós-Graduação em Química da UFBA, 2009. http://www.repositorio.ufba.br/ri/handle/ri/10014.

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O espinafre produzido e mais consumido no Brasil, denominado como espinafre da Nova Zelândia (Tetragonia expansa), difere significativamente do espinafre verdadeiro (Spinacia oleracea) produzido em muitos países do hemisfério norte. As diferenças ocorrem não apenas na classificação botânica, mas em muitas das características químicas dos vegetais. No presente trabalho, foram avaliados os teores de alguns nutrientes e antinutrientes contidos no espinafre comercializado na Bahia, sendo avaliados quatro diferentes procedimentos de digestão das amostras de espinafre com ácido nítrico em sistema aberto. Os resultados obtidos a partir dos diversos procedimentos de pré-tratamento da amostra foram comparados para os vários analitos investigados (Al, Ca, Fe, Cu, Zn, Mn, Mg) e indicaram vantagens da inserção de uma etapa de pré-digestão. Adicionalmente, foram realizados testes de extração dos metais sob investigação em água e em soluções com diferentes níveis de acidez na presença e ausência de agente quelante (ácido etilenodiaminotetracético – EDTA) para avaliação do nível de interação dos metais com o vegetal e, por conseguinte, a disponibilidade destes minerais. Os resultados levaram a acreditar que as interações de Mg(II), Cu(II) e Mn(II) com o espinafre seco eram fracas, enquanto que as interações com Al(III), Ca(II) e Fe(III) eram mais intensas, devido a condições mais drásticas (acidez da solução ou presença de quelante) foram necessárias para maximizar a extração destes metais. Ao considerar informações previamente reportadas sobre os elevados teores de oxalato em espinafre e seus efeitos antinutricionais, foram investigados os teores de oxalato em amostras secas oriundas de amostras de espinafre verdadeiro e espinafre da Nova Zelândia cultivado na Bahia, empregando permanganometria. Para tanto foram realizados estudos sobre as melhores condições para extração de oxalato variando a acidez da solução extratora e os resultados obtidos foram comparados com os apresentados na literatura. Finalmente, foram realizados testes para avaliação da possibilidade de enriquecimento de espinafre com íons metálicos a partir de sucessivas etapas de extração (dessorção) e concentração (sorção) do íon no vegetal. Pôde ser constatado que os maiores níveis de sorção (18 ± 3 mg g-1) e repetitividade foram obtidas para íons cálcio, possivelmente devido ao oxalato existente nos espinafres.
Salvador

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38

PETRONI, SERGIO L. G. "Avaliacao cinetica e de equilibrio do processo de adsorcao dos ions dos metais cadmio, cobre e niquel em turfa". reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11138.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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39

Reis, Tadeu Cavalcante. "Distribuição e biodisponibilidade do níquel aplicado ao solo como NiCl2 e Biossólido". Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-03092003-160423/.

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O comportamento do Ni no solo, principalmente quando adicionado através de biossólidos, ainda é pouco conhecido. Este trabalho objetivou avaliar a influência dos teores totais do metal, de matéria orgânica e dos valores de pH na distribuição daquele elemento no solo e na sua biodisponibilidade. Foram conduzidos três experimentos de incubação em vasos mantidos em casa de vegetação, utilizando 3 kg de amostras da camada de 0 - 0,20 m de dois solos: ARGISSOLO VERMELHO AMARELO Distrófico (PVAd) e NITOSSOLO VERMELHO Distrófico Latossólico (NVdl). Dois experimentos foram montados em solos diferentes, em esquema fatorial 2x2x3, nos quais 2 doses de Ni (21 e 42 Kg ha 1 ) como NiCl2, foram incubadas durante 120 dias, sob dois teores de matéria orgânica e dois valores de pH, obtidos pela adição de turfa e de calcário, respectivamente. Num terceiro experimento fatorial (2x4), os mesmos dois solos foram incubados por 150 dias com a dose de 150 Mg ha -1 de quatro diferentes biossólidos. Posteriormente, cultivou-se alface em todos os vasos por 50 dias Após a incubação, amostras de solo foram analisadas quimicamente, inclusive efetuando-se extrações seqüenciais para determinar a distribuição do Ni adicionado através de NiCl2 e de biossólido. Foram consideradas as frações do metal solúvel + trocável, carbonatos, matéria orgânica, óxidos e residual. Realizou-se também a especiação do Ni baseada no equilíbrio de Donnan, no extrato de saturação das amostras, para discriminar a porção do Ni solúvel que se achava na forma de íon livre. O calcário foi o fator que mais afetou o comportamento do metal, reduzindo a concentração na fração trocável e aumentando-a nas frações matéria orgânica e óxidos. A turfa aumentou os teores do metal na fração trocável e os reduziu nas frações óxidos e matéria orgânica. O NiCl2 aumentou o teor de Ni nas três frações citadas. Os teores do metal nas frações de cada solo foram modelados por equações de regressão, em função dos teores de C-orgânico, Ni total e pH do solo. A distribuição do Ni no solo, quando adicionado através de biossólidos apresentou semelhanças com a distribuição do metal nos próprios biossólidos. Nestes casos, o Ni predominou nas frações mais fortemente retidas, conferindo ao metal comportamento distinto daquele observado pela adição do NiCl2. Tais diferenças puderam ser confirmadas pela ineficiência das equações obtidas nos experimentos com NiCl2, em predizer os teores do metal nas frações dos solos tratados com biossólidos. Na especiação, doses mais elevadas de calcário e turfa resultaram em menores teores de Ni solúvel e livre, os quais aumentaram com a dose de NiCl2. Concentração de ambas as formas de Ni se correlacionaram com os teores do metal absorvidos pelas plantas. Na aplicação de biossólidos ao PVAd, a determinação do Ni livre foi particularmente importante para se prever a biodisponibilidade de Ni para alface. Essencialmente, pode-se concluir que a extração seqüencial e a especiação em extrato de saturação foram eficientes para demonstrar diferenças do comportamento do níquel quando o metal foi aplicado como NiCl2 e como biossólido.
The role of Nickel in soils under the application of biossolids is still not very well known. The objectives of this study were to investigate the influence of total Nickel and organic carbon content, and soil pH, in the Nickel distribution among soil fractions and the bioavailability of the metal to lettuce. Three incubation pot trials were carried out in greenhouse placing in each one 3 kg of the 0-20cm layer of soil. Two soils types were considered: Typic Halpludult and Rhodic Kandiudox. In two of the trials, one for each soil type, soil samples were treated with rates of NiCl2, lime and peat as a source of organic matter and incubated during 120 days. In the third pot trial the above mentioned soils were incubated with four different types of biossolids during 150 days. Once the incubation period ended soils samples were collected and lettuce was planted in the pots of all three trials. Soils samples were submitted to a sequential extraction procedure which comprised the following fractions: exchangeable plus soluble; carbonate, organic, oxides and residual. Soil saturation extracts were also obtained for the determination of free Ni +2 concentration using the Donnan equilibrium technique. When NiCl2, peat, and lime were applied to soils, changes in pH due to lime caused exchangeable Ni to decrease and raised Ni content in organic and oxide fractions. Peat promoted an higher Ni content in the exchangeable fraction and reduced it in the oxide and organic fraction. I contrast NiCl2 raised Ni content in all of the above motioned fractions. Nickel content in all soil fractions were modeled by regression equations using total Ni, organic carbon, and pH as independent variables. Data for the Ni distribution in soils fractions under biossolids application were similar to results from sequential extraction in the biossolids in terms of percentage. In the biossolids trial Ni occurred most in residual fraction of soil, which contrasts with results obtained when Ni was supplied as NiCl2. Speciation study showed that higher rates of lime and peat promoted lower levels of soluble and free Ni in the soil solution. The opposite was detected when NiCl2 was applied. Both soluble Ni and free Ni +2 were well correlated with the Ni content in lettuce, when the metal salt was supplied as Ni source. However, free Ni +2 was a better indicator for Ni bioavailability when bissolids were applied in PVAd. In resume it may be concluded that the sequential extraction procedure and the speciation by means of the Donnan equilibrium approach were useful to express the different behavior of nickel in soil when NiCl2 or bissolids were the source of the metal.

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Yu, Zhewei. "Equilibrium and kinetics studies of hydrogen storage onto hybrid activated carbon-metal organic framework adsorbents produced by mild syntheses". Thesis, Nantes, Ecole des Mines, 2016. http://www.theses.fr/2016EMNA0236/document.

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Depuis une quinzaine d’années, les matériaux poreux de type Metal Organic Frameworks (MOFs) offrent de nouvelles perspectives dans le cadre du stockage d’hydrogène par adsorption. Ces matériaux possèdent une structure et un réseau de pores particulièrement bien adaptés à l’adsorption des gaz. Ainsi, le téréphtalate de Chrome (III) (MIL-101(Cr)), composé chimiquement très stable, possède une grande capacité de stockage de l’hydrogène, du dioxyde de carbone et du méthane. Afin de renforcer sa capacité de stockage d’hydrogène, un dopage au charbon actif (AC) du matériau a été envisagé. Les synthèses des matériaux dopés et non-dopés ont été réalisées et, pour cela, différents agents minéralisants (acide fluorhydrique, acide acétique et acétate de sodium) ont été testés. Les matériaux synthétisés furent caractérisés par diffraction des rayons X (DRX), par microscopie électronique à balayage (MEB), par analyses thermogravimétriques (ATG) et par adsorption d’azote à 77K. Les capacités de stockage d’hydrogène de ces matériaux à 77 K et 100 bar ont été évaluées par mesures des isothermes d’adsorption d’hydrogène, réalisées par méthodes volumétrique et gravimétrique. Les résultats obtenus par ces deux méthodes sont en parfait accord et le matériau composite affiche une capacité d’adsorption de 13.5 wt%, qui est supérieure à celle du matériau non dopé (8.2 wt% dans les même conditions expérimentales). Les cinétiques d’adsorption ont été mesurées à 77 K par méthode volumétrique. Les résultats obtenus ont été comparés au modèle de la force motrice linéaire, Linear Driving Force (LDF). Un modèle de diffusion dépendant de la température a été développé afin de tenir compte des variations de températures qui se produisent durant le processus d’adsorption
Since the last 15 years, the porous solids such as Metal-Organic Frameworks (MOFs) have opened new perspectives for the development of adsorbents for hydrogen storage. The structure and the pore networks of these materials are especially adapted to the adsorption of gases. The chromium (III) terephthalate-based MIL-101(Cr) is a very stable material which exhibits good adsorption uptakes for hydrogen (H2), carbon dioxide (CO2) and methane (CH4).In this study, syntheses were carried out by different ways and several mineralizing agents such as hydrofluoric acid (HF), acetic acid (CH3COOH) and sodium acetate (CH3COONa) have been tested. Moreover, Activated Carbon (AC) has been introduced in the framework to create an AC incorporated composite material with an enhanced specific surface area. Conventional techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and nitrogen (N2) adsorption isotherms at 77 K were used for materials characterizations.In the aim to evaluate hydrogen storage capacities of these materials, hydrogen adsorption isotherms were measured at 77 K via both volumetric and gravimetric methods, and the obtained results are in good agreement. A hydrogen uptake value of 13.5 wt% has been measured at 77 K and 100 bar for the composite material which shows a great improvement of hydrogen capacity compared to the pristine MIL-101(Cr) (8.2 wt%).Finally, hydrogen adsorption kinetics has been measured at 77 K using volumetric method. The obtained results were compared to the Linear Driving Force (LDF) and a temperature dependent diffusion model was also considered to take into account the temperature variations which occur during the adsorption process

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41

Bechtel, Tom B. "Electrochemical partitioning of actinides and rare earths in molten salt and cadmium solvents : activity coefficients and equilibrium simulation /". free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841263.

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42

Fonseca, James Ernest. "Accurate treatment of interface roughness in nanoscale double-gate metal oxide semiconductor field effect transistors using non-equilibrium Green's functions". Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1176318345.

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43

Kakitani, Celina. "Estudo do equilíbrio de fases de hidratos de metano e da mistura metano e dióxido de carbono". Universidade Tecnológica Federal do Paraná, 2014. http://repositorio.utfpr.edu.br/jspui/handle/1/1035.

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Petrobrás
Hidratos são estruturas cristalinas constituídas por moléculas de água e gás ou líquido, sendo que a estabilização dessa estrutura cristalina requer condições de altas pressões e/ou baixas temperaturas. A formação e a aglomeração de hidratos podem causar o bloqueio de linhas de transporte de óleo e/ou gás, reduzindo a eficiência do processo, danificando os equipamentos e comprometendo a segurança da parte operacional. Neste cenário, no presente trabalho é apresentado o estudo numérico-experimental de equilíbrio de fases dos hidratos para identificar as regiões de formação e adequar as condições de operação na indústria petrolífera. Para a predição das condições de formação dos hidratos é desenvolvido um modelo termodinâmico baseado na teoria de sólido ideal de van der Waals e Platteeuw. O modelo é fundamentado na igualdade dos potenciais químicos de todas as espécies em todas as fases (água líquida, hidrato e vapor). Para os cálculos de equilíbrio da fase hidrocarboneto foi utilizada a equação de estado de Soave Redlich-Kwong e o método da secante foi utilizado para solucionar o modelo iterativamente. As medidas experimentais foram realizadas utilizando metano puro e a mistura metano (90 % em mol) e dióxido de carbono e os testes foram realizados em duas bancadas distintas, sendo os procedimentos realizados semelhantes, baseados no método isocórico pela monitoração da resposta da pressão do sistema com a variação da temperatura. Os resultados experimentais e numéricos obtidos foram comparados com dados da literatura com a finalidade de validar o modelo termodinâmico proposto, o aparato experimental e o procedimento adotado. O erro absoluto máximo entre os resultados obtidos experimentalmente e do modelo termodinâmico desenvolvido foi de 0,57%. Desta forma, nota-se os resultados apresentaram boa concordância entre os dados experimentais e os da modelagem numérica.
Hydrates are crystalline structures composed by molecules of water or liquid and gas, and the crystal structure that requires stabilization conditions of high pressure and/or low temperatures. The formation and agglomeration of hydrates can cause blockage of transmission lines oil and / or gas, reducing process efficiency, damaging the equipment and compromise the safety of the operating part. In this scenario, in this paper the numerical-experimental study of phase equilibria of hydrates is presented to identify the regions of formation and adjust the operating conditions in the oil industry. To predict hydrate formation conditions of a thermodynamic model based on the ideal solid solution theory by van der Waals and Platteeuw is developed. The model is based on the equality of the chemical potentials of all species in all phases (liquid water, vapor and hydrate). The SoaveRedlich-Kwong equation of state was employed for the phase equilibrium properties of the hydrocarbon fluid phase and the secant method was used to solve the model iteratively. Experimental measurements were performed using pure methane and methane mixture (90 mol%) and carbon dioxide, and the tests were performed on two separate stands, and similar procedures performed based on the isochoric method by monitoring the pressure response of the system with changes in the temperature. The experimental and numerical results were compared with literature data in order to validate the proposed thermodynamic model, the experimental apparatus and procedure adopted. The maximum absolute error between the experimental results and thermodynamic model was 0.57%. Thus, the results showed good agreement between experimental data and numerical modeling.

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44

Teng, Lidong. "Thermodynamic investigations of transition metal systems containing coabon and nitrogen". Doctoral thesis, KTH, Materials Science and Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24.

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In view of the important applications of carbides and carbo-nitrides of transition metals in the heat-resistant and hard materials industries, the thermodynamic activities of Cr and Mn in the Cr-C, Fe-Cr-C, Mn-Ni-C and Mn-Ni-C-N systems have been studied in the present work by the use of the galvanic cell technique. CaF₂single crystals were used as the solid electrolyte. The phase relationships in selected regions of the systems in question were investigated by the use of the equilibration technique. The phase compositions and microstructures of the alloys were analysed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM).

In the Cr-C system, the Gibbs energy of formation of Cr3C2 were obtained from ElectroMotive Force (EMF) measurements conducted in the temperature range 950-1150 K. The values of the enthalpy of formation of Cr₃C₂ were evaluated by the third-law method. The ground-state energy of the hypothetic end-member compound CrC3, in the bcc structure at 0 K, was calculated by use of the Ab-initio method. Based on the obtained results the Cr-C system was reassessed by use of the CALPHAD approach.

In the Fe-Cr-C system, 16 different alloys were quenched at 1223 K and their equilibrium phases identified by XRD. The experimental results show that the substitution of Cr by Fe in the (Cr,Fe)₇C₃ carbide changes the lattice parameters of the phase. A slight decrease of the lattice parameters with an increase in the Fe content was established. The lattice parameters of the γ-phase in the Fe-Cr solid solution did also show a decrease with an increase of the Fe content. The activities of chromium in Fe-Cr-C alloys were investigated in the temperature range 940-1155 K. The activity of chromium decreases with an increase in the Fe content when the ratio of C/(Cr+C) was constant. It was also established that the activity of chromium decreases with an increase of the carbon content when the iron content was constant. The experimental results obtained were compared with the data calculated by use of the Thermo-Calc software.

In the Mn-Ni-C system the phase relationships were investigated at 1073 K as well as at 1223 K. The experimental results obtained showed that the site fraction of Ni in the metallic sublattice of the carbides M₂₃C₆, M₇C₃ and M₅C₂ (M=Mn and Ni) was quite low (approximately 2~3 percent). The activities of manganese in Mn-Ni-C alloys were investigated in the temperature range 940-1165 K. The three-phase region γ/M₇C₃/graphite was partly constructed at 1073 K.

In the Mn-Ni-C-N system, nitrogen was introduced into Mn-Ni-C alloys by equilibrating with N2 gas. It was established that the solubility of nitrogen in the investigated alloys was effected by the carbon content, and that a (Mn,Ni)₄(N,C) compound was formed in the nitrided alloys. EMF measurements were performed on Mn-Ni-C-N alloys in the temperature interval 940-1127 K. The addition of nitrogen to Mn-Ni-C alloys was found to decrease the activity of manganese. The negative effect of nitrogen on the activity of manganese was found to decrease as the carbon content increased.

Keywords: Thermodynamic activity; Galvanic cell technique; Transition metal carbides; Transition metal nitrides; Phase equilibrium; Thermodynamics; Differential thermal analysis; Scanning electron microscopy; Transmission electron microscopy; Ab-initio calculations; CALPHAD approach;

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45

Qin, Weiwei [Verfasser] y M. [Akademischer Betreuer] Franzreb. "Insights into Metal-Organic Frameworks by High Performance Liquid Chromatography: Synthesis, Equilibrium & Mass Transfer Kinetics / Weiwei Qin. Betreuer: M. Franzreb". Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1084112574/34.

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46

Sjöstedt, Carin. "Iron and aluminium speciation in Swedish freshwaters : Implications for geochemical modelling". Doctoral thesis, KTH, Miljögeokemi och ekoteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-94528.

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Speciation governs transport and toxicity of trace metals and is important to monitor in natural waters. Geochemical models that predict speciation are valuable tools for monitoring. They can be used for risk assessments and future scenarios such as termination of liming. However, there are often large uncertainties concerning the speciation of iron and aluminium in the models, due to the complicated chemistry of these metals. Both are important in governing the speciation of other metals, due to (i) their capacity to form minerals onto which metals can adsorb and (ii) their ability to compete for binding sites to natural organic matter (NOM). Aluminium is also potentially toxic and is therefore closely monitored in acidified freshwaters. In this study different phases of iron in Swedish lakes were characterised. This required a good method for preconcentrating the iron colloids. A new method was developed in this thesis that uses an anion-exchange column to isolate the iron colloids prior to characterisation with extended X-ray absorption fine structure (EXAFS) spectroscopy. Iron was present as ferrihydrite in particles but was also strongly monomerically complexed to NOM in two Swedish lakes. Based on the results an internally consistent process-based geochemical equilibrium model was presented for Swedish freshwaters. The model was validated for pH (n = 9 400) and inorganic monomeric aluminium (Ali) (n = 3 400). The model could simulate pH and Ali simultaneously, and be used for scenario modelling. In this thesis, modelling scenarios for decreases and complete termination of liming are presented for the 3 000 limed Swedish lakes. The results suggest that liming can be terminated in 30 % of the Swedish lakes and decreased in many other lakes.

QC 20120919

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47

Franco, Pietro Escobar. "Remoção de metais pesados utilizando resina Amberlite IR-120 em sistema batelada". Universidade Estadual do Oeste do Paraná, 2011. http://tede.unioeste.br:8080/tede/handle/tede/2924.

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Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2017-08-23T20:19:47Z No. of bitstreams: 1 Pietro E Franco 2011.pdf: 990760 bytes, checksum: fee1787afa670f26170e23dc070a0075 (MD5)
Made available in DSpace on 2017-08-23T20:19:47Z (GMT). No. of bitstreams: 1 Pietro E Franco 2011.pdf: 990760 bytes, checksum: fee1787afa670f26170e23dc070a0075 (MD5) Previous issue date: 2011-02-07
This study evaluated the removal of heavy metal íons Zn+2 and Ni+2 through the íon exchange process using a cationic resin Amberlite IR-120/Na+. The characterization of wastewater from an industry of electroplating was performed and the results were the basis for obtaining the aqueous solution used at work. Experiments were performed in batch system for the valuation of ion exchange kinetics of the binary systems Ni+2–Na+, Zn+2–Na+ and the ternary system Ni+2–Zn+2–Na+ in the initial concentrations of 20ppm and 200ppm, in the conditions of pH 4.5, agitation speed of 150rpm and 25ºC. Two models were tested to obtain kinetic parameters of ion exchange. In the simulation of kinetic model in which the ion exchange reaction was considered the limiting step during the model does not fit the experimental data. A second simulation, where the diffusion in the resin (linear driving force model) was assumed to be limiting step had better fit and evidence for the hypothesis that the experimental conditions the ion exchange process presents diffusional limitations. The value of mass transfer coefficients in the resin (ks) varied from 0.0032 to 0.043min-1. Kinetic studies showed that equilibrium is reached around 400 minutes for the systems with initial concentration of 20ppm and 60 minutes for systems with initial concentration of 200ppm. Experiments to obtain data of ion exchange equilibrium were performed for the binary systems Ni+2–Na+, Zn+2–Na+ and for the ternary system Ni+2–Zn+2–Na+ at concentrations of 160ppm and 300ppm (pH 4.5, agitation speed of 150rpm and 25ºC). The isotherms were modeled using the law of mass action ideal and not ideal. The Bromley and Wilson models were used to calculate the activity coefficient in solution and resin. Simulations were conducted for determining the value of the constant and equilibrium thermodynamics of the interaction parameters of Wilson. The results showed that the law of mass action is not ideal fits well the experimental data of binary systems. The simulation of the ternary equilibrium system was accomplished using a predictive, based on the interaction parameters of Wilson and equilibrium constants provided by the modeling of binary systems. The data predicted by the model were compared with experimental data and the results showed that the model was able to predict the behavior of the ternary system. The affinity of the studied ions with Amberlite IR-120 showed the following order: Zn+2 Ni+2 > Na+. For all experiments conducted in this study, the variation of pH and stoichiometry during the experiments were evaluated. For the parameter pH, speciation graphics were done using the HYDRA software and the results show that ions of interest in the solutions (Zn+2 and Ni+2) were above 95%. The average deviation from stoichiometry was less than 8%.
O presente trabalho avaliou a remoção dos íons de metais pesados Zn+2 e Ni+2 através do processo de troca iônica utilizando a resina catiônica Amberlite IR-120/Na+. A caracterização do efluente de uma indústria do ramo de galvanoplastia foi realizada e os resultados obtidos serviram de base para a obtenção da solução aquosa utilizada no trabalho. Experimentos foram realizados em sistema batelada para a avaliação da cinética de troca iônica dos sistemas binários Ni+2–Na+, Zn+2–Na+ e para o sistema ternário Ni+2–Zn+2–Na+ nas concentrações iniciais de 20ppm e 200ppm, nas condições de pH de 4.5, velocidade de agitação de 150rpm e temperatura de 25ºC. Dois modelos foram testados para obtenção de parâmetros de cinética de troca iônica. Na simulação do modelo cinético em que a reação de troca iônica foi considerada a etapa limitante o modelo não se ajustou aos dados experimentais. Uma segunda simulação, em que a difusão na resina (modelo da força motriz linear) foi assumida como etapa limitante apresentou melhor ajuste e evidencia a hipótese de que para as condições experimentais adotadas o processo de troca iônica apresenta limitações difusionais. O valor dos coeficientes de transferência de massa na resina (ks) apresentaram valores entre 0,0032-0,043min-1. Estudos cinéticos mostraram que o equilíbrio é atingido em torno de 400 minutos para os sistemas com concentração inicial de 20ppm e de 60 minutos para os sistemas com concentração inicial de 200ppm. Experimentos para obtenção de dados de equilíbrio de troca iônica foram realizados para os sistemas binários Ni+2–Na+, Zn+2–Na+ e para o sistema ternário Ni+2–Zn+2–Na+ nas concentrações de 160ppm e 300ppm (pH de 4.5, velocidade de agitação de 150rpm e temperatura de 25ºC). As isotermas foram modeladas com uso da lei da ação das massas ideal e não ideal. Os modelos de Bromley e Wilson foram utilizados para o cálculo do coeficiente de atividade na solução e na resina. Realizou-se simulação para a determinação do valor da constante termodinâmica de equilíbrio e dos parâmetros de interação de Wilson. Os resultados mostraram que a lei da ação das massas não ideal se ajustou bem aos dados experimentais dos sistemas binários. A simulação do sistema de equilíbrio ternário foi realizada de forma preditiva, baseada nos parâmetros de interação de Wilson e constantes de equilíbrio fornecidas pelas modelagens dos sistemas binários. Os dados preditos pelo modelo foram comparados com os dados experimentais e os resultados mostraram que o modelo foi capaz de prever o comportamento do sistema ternário. A afinidade dos íons estudados com a resina Amberlite IR-120 mostrou a seguinte ordem: Zn+2 Ni+2 > Na+. Para todos os experimentos realizados neste trabalho, a variação de pH e de estequiometria ao longo dos experimentos foram avaliados. Para o parâmetro pH, gráficos de especiação foram realizados com o uso do software HYDRA e os resultados mostram que os íons de interesse nas soluções (Zn+2 e Ni+2) estavam acima de 95%. O desvio médio da estequiometria não foi superior a 8%.

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48

Nicolau, Marco. "Separação dos Isómeros de Xileno em Metal-Organic Frameworks - MOFs". Master's thesis, Instituto Politécnico de Bragança, Escola Superior de Tecnologia e de Gestão, 2008. http://hdl.handle.net/10198/1718.

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A separação dos isómeros de xileno é um problema clássico da indústria petroquímica devido à sua ligação directa à produção de PET. A destilação é uma das formas possíveis de remover o o-xileno, mas falha para os restantes alquilaromáticos devido aos pontos de ebulição serem muito próximos. Além da cristalização, a qual possui uma pobre eficiência, a adsorção é largamente usada, sendo operado industrialmente em leito móvel simulado (SMB). Como adsorventes nesses processos são usados os zeólitos X e Y, permutados com catiões, tal como o Na+, K+ e Ba2+. Os metal-organic frameworks (MOFs) são uma nova classe de materiais cristalinos e recebem actualmente bastante interesse devido às suas potencialidades para serem aplicados como adsorventes. O carácter maioritariamente orgânico da superfície interna dos MOFs oferece um potencial sem precedentes para melhorar e ajustar a afinidade para adsorbatos aromáticos. Este trabalho representa um dos primeiros estudos acerca do uso de MOFs na separação por adsorção em fase gasosa dos isómeros de xileno. Neste trabalho, apresenta-se um estudo detalhado do equilíbrio de adsorção mono- e multicomponente dos isómeros de xileno e do etilbenzeno no MOF Zn(BDC)(Dabco)0:5. Os resultados obtidos, indicam que o MOF em estudo apresenta duas categorias de sítios activos de adsorção e que a forma como as moléculas se empacotam na estrutura microporosa do sólido pode ser determinante na separação. Além da baixa selectividade, o valor elevado das entalpias de adsorção, comparativamente aos zeólitos, é prejudicial do ponto de vista da operação de processos adsorptivos. The separation of mixed C8 alkylaromatic compounds is one of the most challenging issues in the chemical industry because of its direct link with PET manufacture. Distillation is only feasible for the removal of o-xylene; it fails for the other C8 alkylaromatic compounds because of the similarity of their boiling points. Besides crystallization, which has a poor efficiency, adsorption is widely used and is operated industrially in simulated moving bed processes. Zeolites X and Y exchanged with cations such as Na+, K+ e Ba2+ are used in such processes. Metal-organic frameworks (MOFs) are a new class of microporous crystalline materials and currently receive much attention in regard to adsorption applications. The mainly organic character of the inner surface of MOFs offers unprecedented potential for enhancing and fine-tuning the affinity for aromatic adsorbates. This work represents one of the first uses of MOFs in the separation by adsorption of xylene isomers under vapor conditions. This work reports a detailed experimental study of single and multicomponent adsorption equilibrium of xylene isomers and ethylbenzene in the MOF Zn (BDC)(Dabco)0:5. The results arising from this study lead us to conclude that the MOF has two categories of adsorption sites and that the stacking of the molecules in the microporous structure is crucial in the separation. Besides the poor selectivity, the high value of the adsorption enthalpy of aromatics in this MOF, in comparison to zeolites, is not beneficial with respect to the operation of adsorption processes.

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49

Serarols, i. Font Joan Lluís. "Adsorció d'or i zinc amb resines impregnades XAD-2. Superfície d'Equilibri, un nou concepte per a l'adsorció". Doctoral thesis, Universitat de Girona, 2001. http://hdl.handle.net/10803/7889.

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Dins dels processos de recuperació de metalls de dissolucions diluïdes s'ha realitzat un estudi del procés d'extracció d'or i de zinc mitjançant resines amberlite XAD-2 impregnades amb sulfur de triisobutil fosfina (TIBPS) i àcid di-(2-etilhexil) fosfòric (DEHPA) respectivament.

S'ha realitzat un estudi de l'equilibri de l'adsorció d'espècies metàl·liques d'aquests metalls amb les resines indicades anteriorment. Amb la metodologia emprada per a la determinació dels punts d'equilibri dels experiments en batch i en columna, s'ha vist que una única isoterma no podia descriure el fenomen global d'equilibri i que en funció de la metodologia emprada s'obtenien isotermes diferents.

Es va introduir una nova variable per poder explicar el fenomen observat, i per tant, amb aquesta nova variable l'equació de la isoterma es converteix amb l'equació d'una supèrfície que s'ha definit com a Superfície d'Equilibri.

S'han determinat les equacions de les Suprfícies d'Equilibri dels sistemes d'adsorció estudiats (Au(III) TIBPS/XAD-2 i Zn(II) DEHPA/XAD-2) observan una bona coincidència de tots els punts d'equilibri obtinguts sobre la superfície, així com, un bon ajust de totes les isotermes obtingudes en funció de les diferents metodologies emprades sobre les respectives superfícies d'equilibri. Aquest nou concepte generalitza el concepte d'isoterma d'un procés d'adsorció.

Fimalment, s'ha plantejat un model matemàtic d'adsorció per a determinar el coeficient efectiu de difusió (De) i el coeficient de transferància de matèria (kf) per ambdós sistemes d'adsorció estudiats mitjançant l'aplicació del model de difusió de sòlid homogeni (HSDM), utilitzant com a condició de contorn en el model la isoterma de Langmuir obtinguda mitjançant els experiments en columna de llit fix i emprant també l'equació obtinguda mitjançant el nou concepte de Superfície d'Equilibri.

Els resultats obtinguts són molt satisfactoris, per tant, es pot concloure que la Superfície d'Equilibri és una bona eina per a descriure l'equilibri en els processos d'adsorció d'or i zinc amb les resines amberlite XAD-2 impregnades amb TIBPS i DEHPA respectivament.
The study of the extraction process of gold and zinc with Amberlite XAD-2 resins impregnated with tri-isobutylphosphine sulfide(TIBPS) and di-(2-ethylhexyl) phosphoric acid (DEHPA), respectively, has been studied.

The equilibria governing the metallic ions adsorption by the studied systems have been established. Taking into account the methodology used to get the equilibria points corresponding to batch and column experiments performed, it was noticed that a unique isotherm could not describe the global equilibrium and that different isotherms were obtained in function of the experimental methodology carried out.

It was introduced a new variable for explaining the phenomenon observed. By doing this, the isotherm became a surface that it was called equilibrium isotherm.

The equations corresponding the Equilibrium Surfaces of the adsorption systems studied (Au(III) / TIBPS-XAD-2 and Zn(II) / DEHPA-XAD-2) were determined. The equilibria points obtained by batch and column experiments as well as obtained isotherms were very well placed on the surface. Thus, this new concept generalises the concept of isotherm in an adsorption process.

Finally, the homogeneous solid diffusion model (HSDM) was applied for performing an adsorption mathematical model for determining the effective diffusion coefficient (De) and the mass transfer coefficient (kf) of both studied systems.

The obtained results were very successful, so, it can be concluded that the Equilibrium Surface is a very good tool for describing the equilibria of the studied adsorption processes.

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50

Dednam, Wynand. "Atomistic simulations of competing influences on electron transport across metal nanocontacts". Thesis, Universidad de Alicante, 2019. http://hdl.handle.net/10500/26155.

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In our pursuit of ever smaller transistors, with greater computational throughput, many questions arise about how material properties change with size, and how these properties may be modelled more accurately. Metallic nanocontacts, especially those for which magnetic properties are important, are of great interest due to their potential spintronic applications. Yet, serious challenges remain from the standpoint of theoretical and computational modelling, particularly with respect to the coupling of the spin and lattice degrees of freedom in ferromagnetic nanocontacts in emerging spintronic technologies. In this thesis, an extended method is developed, and applied for the first time, to model the interplay between magnetism and atomic structure in transition metal nanocontacts. The dynamic evolution of the model contacts emulates the experimental approaches used in scanning tunnelling microscopy and mechanically controllable break junctions, and is realised in this work by classical molecular dynamics and, for the first time, spin-lattice dynamics. The electronic structure of the model contacts is calculated via plane-wave and local-atomic orbital density functional theory, at the scalar- and vector-relativistic level of sophistication. The effects of scalar-relativistic and/or spin-orbit coupling on a number of emergent properties exhibited by transition metal nanocontacts, in experimental measurements of conductance, are elucidated by non-equilibrium Green’s Function quantum transport calculations. The impact of relativistic effects during contact formation in non-magnetic gold is quantified, and it is found that scalar-relativistic effects enhance the force of attraction between gold atoms much more than between between atoms which do not have significant relativistic effects, such as silver atoms. The role of non-collinear magnetism in the electronic transport of iron and nickel nanocontacts is clarified, and it is found that the most-likely conductance values reported for these metals, at first- and lastcontact, are determined by geometrical factors, such as the degree of covalent bonding in iron, and the preference of a certain crystallographic orientation in nickel.
Physics
Ph. D. (Physics)

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Tesis sobre el tema "Metals Equilibrium"

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