The aim of the present work was to develop synthesis routes to produce synthetic zeolites with industrial attractiveness from non-expensive Bolivian raw materials, such as clays and diatomite. In particular, the work was focused on the synthesis of low-silica zeolites with the LTA and FAU structures. The raw materials as well as intermediate and final zeolite products were structurally characterized by different techniques, namely scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen gas adsorption, inductively coupled plasma mass spectrometry (ICP-MS). Besides, the final properties were evaluated for intended applications i.e. brightness by UV-VIS spectroscopy for LTA-type zeolite A in detergents and the CO2 breakthrough adsorption of FAU-type zeolite X for gas separation.   The first part of this study deals with the synthesis of low silica zeolite A from Bolivian montmorillonite clay (Paper I). The clay was fused at high temperature with NaOH to render the material more reactive. The raw montmorillonite had a SiO2/Al2O3 ratio of 4 and sodium aluminate was added to the mixture to decrease this ratio to 2. An optimization of the synthesis time was performed. For the sake of comparison, the same treatment was applied to commercial kaolin. The final zeolite product from Bolivian montmorillonite exhibited high brightness despite the presence of iron in appreciable amount in the starting material and the final product. It was concluded that magnesium, present in the raw material, exerted a masking effect on iron. The latter was incorporated into extraneous magnesium aluminosilica compounds, thereby increasing brightness and strongly decreasing the overall yellowness. This simple method appears as a promising alternative to the complex and costly techniques suggested to reduce the iron content in natural raw materials, especially kaolin.   The second part of the study addresses the synthesis, characterization and evaluation of FAU-type zeolites i.e. Y and X from diatomite and chemical grade reagents, respectively. With regard to the synthesis of zeolite Y, the diatomite was leached in sulfuric acid to remove impurities prior to synthesis, this step also resulted in dealumination, which rendered possible the synthesis of ZSM-5 zeolite (Paper II). However, extra aluminum had to be added in the form of aluminum sulfate for the synthesis of zeolite Y (Paper III). In this case, the raw materials were reacted hydrothermally at 100°C in aqueous medium with sodium hydroxide. Variations in parameters such as the Na2O/SiO2 ratio and synthesis time were investigated. As a result, micro-sized crystals of zeolite Y were obtained at a Na2O/SiO2 ratio of 0.9, which produced zeolite Y with a SiO2/Al2O3 ratio of 3.9. Also, zeolite Y with a SiO2/Al2O3 ratio of 5.3 in low yield at a Na2O/SiO2 ratio of 0.6 was achieved. In this way, diatomite behaved similarly to colloidal silica in traditional syntheses having a high degree of polymerization. Zeolite Y with a SiO2/Al2O3 ratio of 5.3 might be useful for the production of ultra-stable zeolite Y for use as FCC catalyst. Addition of NaCl to this system was also found to completely inhibit the formation of zeolite P and to retard the effects of overrunning by a synergic effect of Na and Cl ions (Paper IV).   As an innovate application, FAU-type zeolite X films were growth on steel monoliths as structured adsorbent for CO2 removal (Paper V). Thicknesses 3 and 10 µm on steel monoliths of 1600 cells per square inches (c.p.s.i.) were investigated. The produced structured adsorbents showed reasonable CO2 adsorption capacity but with a very low pressure drop compared with traditional packed beds of zeolite beads. The CO2 breakthrough fronts were very sharp and the mass transfer resistance was very low compensating the presence of less adsorbing material by reducing cycle time and increased cycle frequency to increase throughput.     To summarize, zeolites with promising characteristics were successfully synthesized from Bolivian raw materials in this thesis work. However, further characterization is required to qualify these products for industrial applications. Moreover, this study might help the development of poor regions of the Bolivian Altiplano and open up for large scale production, since the methods developed in this work are simple and non-expensive. / Characterisation of clays and feldspars from the Altiplano and development of methods for conversion of these materials to valuable zeolites and evaluation in applications

Ion selectivity of minerals has traditionally been utilized in industry as a catalyst, metal separation, and environmental reclamation/sequestration tool. There is an increased interest in understanding ion selectivity mechanisms of micro-porous minerals and mineral-like structures and how they can be applied in various industries: environmental and, potentially, pharmaceutical. This study seeks to understand the ion exchange mechanisms in micro-porous zirconosilicates using time-resolved Raman spectroscopy and X-ray diffraction. The thesis material was exchanged with H+, Na+, K+, and Cs+ in order to better understand structural changes as well as the influence of the H+-bonding during the exchange process. It is hypothesized that the host (H+) ion strongly influences the ion selectivity of the mineral by changing framework polyhedra and ring geometry, and the geometry of the interstitial the OH…H2O bond network to only allow cations of certain sizes through the channels. In addition, the H+ may repel cations with high charge densities from entering the extra-framework sites in the crystal structure by protonating the channel pathways.

Titanium dioxide (TiO2) attracts extensive attention due to its widespread technological and environmental applications. This study seeks to investigate the surface charging behavior of the two TiO2 polymorphs, anatase and rutile, using Flow Adsorption Microcalorimetry (FAMC). FAMC allows direct quantitative measurement of the heat of a surface reaction; these calorimetric heats are directly proportional to the surface charge. Determining the magnitude of positive and negative charges at the surface over a range of pHs allows for the determination of the point of zero net charge (PZNC) via a unique calorimetric method that removes many of the shortcomings related to the other analytical techniques used for such measurements.

The objective of this research is to further define the relationship between the charge state of insulin, and the self assembly properties of insulin and PEGylated insulin in solution. Polyethylene glycol (PEG) chains were covalently attached to insulin in order to evaluate their impact on insulin's systemic duration of action after pulmonary dosing. This thesis will focus on the assembly properties of the PEG-insulin and insulin, and also demonstrate how the charge state, which was modified by the covalent attachment of PEG, relates to different modes of behavior by anion and cation exchange chromatography. In addition, explain how modifying the assembly state extends to improving formulation properties of spray-dried insulin powders. This thesis is an investigation into the relationship of insulin's charge state controlled by pH and how the charge state affects the self assembly of insulin, especially when the zinc ion is removed. Ionic interaction is one of the major forces affecting insulin assembly. The theory that a change in the charge state of insulin could modulate the ionic interaction and reduce hexamer formation at alkaline conditions was investigated. Experiments were designed to measure the level of hexamer with light scattering, and the amount of hexamer was then correlated with the pH and zinc content of the solutions. The importance of the charge state of the monomer and its behavior extends to chromatography and purification modes as well. Specifically, the purification of various species of PEGylated insulin presents a challenge. By varying mobile phase pH which induces the charge to insulin, an ion exchange method demonstrated very high resolution and controllable interaction between the ion exchange media and the insulin derivatives. A highly accurate method for determining molecular weight and thus the average associated state of insulin in solution has been developed using the MALS (Multi-Angle Light Scattering). Insulin concentration, pH, and metal ion concentrations, were in pharmaceutically relevant ranges. The MALS method was developed to evaluate how the parameters above affect the self-assembly properties of insulin, and use the assembly properties to improve formulations of insulin or PEGylated insulin. To use the light scattering technique the dn/dc (change in refractive index with change in concentration) is required. During the method development, the dn/dc of insulin was measured at 690 nm, and a value of 0.185 mL/g based on theory was confirmed. A novel approach for preparing insulin powders with improved chemical stability, based on maintaining the dissociation of hexamers in solution during the spray drying process was developed. The mode presented here is to remove the zinc ions from solution, increase the pH from 6.6 to 7.8, and maintain a low concentration of insulin approximately 2 to 15 mg/mL. Each of these factors alone decreases the hexamer population in solution, but by combining all three factors, hexamers are driven to very low levels of equilibrium. The increased stability of the powders is predominately related to the decrease in covalent insulin dimer (CID). The data presented correlates a reduced hexamer population in the solution with lower levels of CID's in the dry powder compared to controls. The CID formation rate was reduced by 40% compared to a control.

Topochemical strategies, techniques that allow one to effectively manipulate the structures of nonmolecular solids once a crystal lattice is established, are effective in the low temperature (< 500 °C) modification of solid state structures, allowing the preparation of nonmolecular compounds not accessible by standard synthetic routes. Some of the techniques, ion exchange, intercalation/deintercalation, have proven to be excellent synthetic methods for preserving specific frameworks. The combination of these techniques can allow one to create a multistep approach that can be used to design new compounds with interesting properties. As an expansion to the field of topotactic reactions, a multistep approach was developed towards the synthesis of the new compounds (A xM0.5Cly)LaNb2O7 (where A = Rb, Cs; M = Fe, Ni; x ≈ 1.5;y ≈ 1) at temperatures below 400oC. The first reaction step involved the ion exchange of the host materials (ALaNb2O7, A = Rb, Cs) to form the products M0.5LaNb2O7 (where M = Fe, Ni), a structure open to further chemistry. The next step involved reductive intercalation with Rb or Cs metal to form the air sensitive mixed-valence products with the nominal compositions, A1.5M0.5LaNb2O7. The last step involved the oxidative intercalation of chlorine using chlorine gas to obtain the final compounds. This multistep approach is a design to form mix-metal halide layers, specifically those with divalent cations, within layered perovskites, opening the doors to compounds that can have interesting properties. This reaction series was also applied to the tantalate layered oxides, leading to the formation of the new compound Ni 0.5LaTa2O7 through ion exchange. The further multistep topochemical manipulation of this new compound was not successful and was indicative of the difference in chemical behavior of the tantalates versus the niobates. We have also investigated the oxidative intercalation of halogens into a series of Ruddlesden-Popper (R-P) ruthenate oxides with the formula Ae n+1RunO3n+1 (Ae = Ca, Sr; n = 1, 2, 3) using several sources of fluorine, chlorine, and bromine. A new method was developed to intercalate chlorine into layered systems; this new approach avoids the use of chlorine gas which is highly toxic. The new phase Sr3Ru2O7Cl0.7 was synthesized by the new method and further topotactic manipulations were explored. The chemistry was not limited to the n = 2 phase but was also applied to the n = 3 phase, Sr4Ru3O10.

Layered perovskites can be classified in three major groups: Dion-Jacobson AA′n-1BnO3n+1, Ruddlesden-Popper A2A′n-1BnO3n+1,and Aurivillius phase (Bi2O2)A′n-1BnO3n+1. (A: Alkali metal, Alkali-earth metal; A′: Lanthanides and Bi; B: Ti, Nb, Ta; n: thickness of slabs). For more than two decades researchers have shown much interest in this series because of their magnetic and electrical properties. Tuning synthesis parameters such as temperature, time, and host structure can be used to direct such properties. Low temperature synthetic methods (topochemical methods) allow the preparation of compounds not accessible by traditional high temperature reactions. This dissertation mainly considers the topochemical methods of ion exchange and reductive and oxidative intercalation to build new low temperature or metastable layered perovskites. The two-dimensional Dion-Jacobson ALaNb2O7 layered perovskites were intercalated reductively to produce A2LaNb2O7 andthen oxidized with water or hydro-chalcogenides (H2Ch, Ch: S, Se) to produce the novel alkali metal hydroxide, (A2OH)LaNb2O7, and alkali metal hydro-chalcogenides, (A2ChH)LaNb2O7, respectively. The synthesis and characterization of these compounds are presented in Chapters 2 and 3. In another set of studies, high temperature ceramic methods lead to the new host APrNb2O7. When this reaction is followed by ion exchange, (CuCl)PrNb2O7 can be prepared. The structural refinement, magnetic properties, and thermal stability of new phases have been studied in Chapter 4. The utility of praseodymium niobates for the formation of other metal oxyhalides was also developed; the series (MX)PrNb2O7 (M: Mn, Fe, Co, Cu and X: F, Cl) were prepared by the ion exchange of LiPrNb2O7 and the obtained phases characterized (Chapter 5). Further, to expand the library of materials and because of interesting properties of lanthanides (Ln: La, Pr, Nd, Sm), lanthanide tantalates have been explored for the preparation of oxyhalides and resulted in the compounds (CuCl)LnTa2O7 (Ln: Pr, Nd) (Chapter 6). Manipulation of Dion-Jacobson layered perovskites are not limited to lanthanides, other hosts with interesting properties have been examined (e.g. ABiNb2O7) (A: alkali metal, CuCl) and their crystal structures characterized along with thermal stability and magnetic response.

Diante da redução dos teores de níquel em minérios sulfetados, novos estudos têm sido realizados para extração e processamento de minérios lateríticos. O processamento destes minérios gera soluções contendo cobalto, que poderia ser recuperado por extração por solventes. No entanto, esta tecnologia possui riscos com relação à saúde ocupacional e incêndios. Como possível alternativa, a eletrodiálise é uma tecnologia utilizada para recuperação de metais de fontes líquidas, permitindo a separação de cátions e ânions pela aplicação de uma corrente elétrica em dois eletrodos. Quando comparada à extração por solventes, possui menor consumo de produtos químicos, pouca geração de resíduos e operação com menor dispêndio energético. O objetivo deste trabalho foi avaliar uma rota hidrometalúrgica para recuperação de uma solução sintética de sulfatos de cobalto (II), magnésio (II), manganês (II) e cromo (III), simulando concentrações obtidas numa etapa do processamento industrial de minérios lateríticos. Para tanto, foi construída uma unidade de eletrodiálise em acrílico transparente, onde foram posicionadas as membranas de troca catiônicas e aniônicas. Nas extremidades da unidade foram posicionados eletrodos de titânio revestidos com óxido de titânio e óxido de rutênio (70TiO2/30RuO2), para o cátodo e ânodo. Tanto as membranas quanto os eletrodos possuíram área de 16 cm². Duas configurações de eletrodiálise foram estudadas, uma visando à recuperação de íons e de ácido sulfúrico, e outra visando à concentração de íons. Posteriormente, a partir da solução concentrada, foi avaliada a recuperação do cobalto por três sistemas, eletrorrecuperação, precipitação e troca iônica. A eletrorrecuperação utilizou cátodos de cobalto, alumínio e aço inoxidável, e ânodos de titânio revestido (70TiO2/30RuO2). A precipitação utilizou hidróxido de sódio e ditionito de sódio. A troca iônica foi realizada em batelada, utilizando cinco tipos de resinas. No caso do sistema com cinco compartimentos, após 64 h aplicando-se densidade de corrente de 6,25 mA.cm-², os resultados indicaram extração aproximada de 76 % para Co2+, 69 % para Mn2+, 79 % para Mg2+ e 32 % para Cr3+. A recuperação de ácido sulfúrico foi comprovada pelo aumento da concentração de H2SO4 de 0,01 para 0,1 mol.L-1 no compartimento anódico. No caso do sistema com seis compartimentos, após 136 h aplicando-se densidade de corrente de 6,64 mA.cm-², os resultados indicaram extração aproximada de 95 % para Co2+, Mn2+, Mg2+ e SO42-, e de 85 % para Cr3+. O aumento da concentração no compartimento concentrado foi de 178 % para Co2+, 145 % para Mn2+, 165 % para Mg2+ e 79 % para Cr3+. A eletrorrecuperação de cobalto foi alcançada somente com cátodo de aço inoxidável, permitindo extração de 80 % do cobalto da solução, com densidade de corrente de 14,3 a 28,6 mA.cm-2. Não foi detectada deposição de cromo. A precipitação por hidróxido não permitiu a separação do cobalto do cromo, e a precipitação do cobalto por ditionito de sódio não foi detectada. A resina M4195 teve o melhor rendimento de adsorção para o cobalto em relação ao cromo, alcançando quase 40 % de extração. Os resultados confirmaram a viabilidade da eletrodiálise para produzir soluções tratadas e soluções concentradas de íons. A troca iônica e a eletrorrecuperação tiveram os resultados mais promissores para recuperação de cobalto. Dessa forma, a rota proposta pode ser uma solução complementar para recuperação de cobalto advindo do processamento de minérios lateríticos, em relação à técnica de extração por solventes. / Due to the depletion of nickel contents in sulfide ores, new studies have been carried out to extract and process lateritic ores. The processing of these ores generates solutions containing cobalt, which could be recovered by solvent extraction. However, this technology has occupational health and fire hazards. As a possible alternative, electrodialysis is a technology used for the recovery of metals from liquid sources, allowing the separation of cations and anions by the application of an electric current in two electrodes. When compared to solvent extraction, it has lower consumption of chemicals, less generation of waste and energy operation. The objective of this work was to evaluate a hydrometallurgical route to recover a synthetic sulfate solution containing cobalt (II), magnesium (II), manganese (II) and chromium (III), simulating concentrations obtained in one step of the industrial processing of lateritic ores. For this, a transparent acrylic electrodialysis unit was constructed, with cationic and anionic ion exchange membranes. At the extremities of the unit, titanium electrodes coated with titanium oxide and ruthenium oxide (70TiO2/30RuO2), were positioned as the cathode and anode. Both the membranes and electrodes had 16 cm² of area. Two electrodialysis configurations were studied, one aiming at the recovery of ions and sulfuric acid, and the other aiming at the concentration of ions. Thereafter, from the concentrated solution, the cobalt recover was evaluated by three systems, electrowinning, precipitation and ion exchange. The electrowinning tests were performed with cobalt, aluminum and stainless steel cathodes. Titanium coated electrodes (70TiO2/30RuO2) were used as anode. In the precipitation tests, sodium hydroxide and sodium dithionite were used. The ion exchange tests were performed in batch mode, using five types of resins. For the system with five compartments, after 64 h applying a current density of 6.25 mA.cm-², the results indicated an approximate extraction of 76 % for Co2+, 69 % for Mn2+, 79 % for Mg2+ and 32 % for Cr3+. The recovery of sulfuric acid in the anode compartment was confirmed by the increase of the H2SO4 concentration from 0.01 to 0.1 mol.L-1. For the system with six compartments, after 136 h applying a current density of 6.64 mA.cm-², the results indicated an approximate extraction of 95 % for Co2+, Mn2+, Mg2+ and SO42-, and 85 % for Cr3+. The concentration increase in the concentrate compartment was 178 % for Co2+, 145 % for Mn2+, 165 % for Mg2+ and 79 % for Cr3+. The cobalt electrowinning was reached only with the stainless steel cathode, allowing an extraction of 80 % of the cobalt from the solution, with current density from 14.3 to 28.6 mA.cm-². No chromium deposition was detected. Precipitation by hydroxide did not allow the separation of cobalt from chromium, and precipitation of cobalt by sodium dithionite was not detected. The M4195 resin had the best adsorption yield for cobalt over chromium, achieving almost 40 % extraction. The results confirmed the feasibility of the electrodialysis to produce treated solutions and concentrated solutions of ions. Ionic exchange and electrowinning had the most promising results for cobalt recovery. Thus, the application of the proposed route may be a complementary solution for the recovery of cobalt from lateritic ores processing, compared to solvent extraction.

A crescente industrialização acompanhada do uso de metais pesados nos processos industriais nas últimas décadas resultou num aumento da contaminação do meio ambiente, principalmente em ambientes aquáticos. Assim, sendo a água um recurso natural de suma importância para a vida, métodos de tratamento de efluentes tornam-se indispensáveis para empresas geradoras de efluentes. O objetivo desse trabalho é a utilização de um sistema de troca iônica constituído por micro-colunas de resinas catiônicas e aniônicas para adsorção de metais pesados de soluções industriais, visando à recirculação de água de lavagem de processos de galvanoplastias. As resinas utilizadas são: Amberlyst 15 WET e Amberlyst A-21; Dowex Marathon C e Dowex Marathon A; Purolite C-150 e Purolite A-850. Também se avalia a eluição dos íons metálicos nas resinas em questão. O efeito que a temperatura possui na eluição é avaliado para as resinas catiônicas, Purolite C-150 e Dowex Marathon C. A cinética e a termodinâmica de adsorção do cromo trivalente e do zinco são avaliados. A metodologia consiste em realizar experimentos de adsorção e eluição em colunas de troca-iônica e experimentos de adsorção em batelada para análise da cinética e termodinâmica dos íons presentes em solução. Os resultados mostram que a qualidade da água após a adsorção nos três sistemas propostos está de acordo com os valores permitidos pela Resolução CONAMA 357/05. Analisando os resultados da eluição nas resinas se verifica que o aumento da temperatura favorece a remoção de íons presentes nos sítios de troca da resina, com exceção do cromo trivalente. As reações de troca-iônica dos íons Cr3+ e Zn2+ seguem os modelos de reação pseudo-segunda ordem. A natureza das reações de troca-iônica do cromo trivalente nas resinas estudadas é exotérmica e a do zinco é endotérmica. / The increasing industrialization carried out with the use of heavy metal in industrial processes over the last decades resulted in increasing environmental contamination, mainly in aquatic environments. Thus, as water is an extremely important natural resource for life, effluent treatment methods become essential for effluent generating companies. This work aims at using an ionic exchange system made of micro-columns of both cathionic and anionic resins for heavy metals adsorption of industrial solutions, for the recirculation of wastewater from electroplating processes. The resins used are: Amberlyst 15 WET and Amberlyst A- 21; Dowex Marathon C and Dowex Marathon A; Purolite C-150 and Purolite A-850. An evaluation of the metallic ions elution is also carried out for such resins. The effect of temperature on the elution is assessed for cathionic resins, Purolite C-150 and Dowex Marathon C. The adsorption kinetics and thermodynamics for trivalent chrome and zinc are assessed. The methodology consists of carrying out experiments of adsorption and elution in ion exchange columns and experiments of adsorption by batch for both kinetic and thermodynamic analyses of ions present in the solution. The results show that the water quality after the adsorption in all three systems proposed is in accordance with the values allowed by the CONAMA 357/05 Resolution. By analyzing the results of the elution in the resins, one can observe that the temperature increase favors the removal of ions present in resin-exchange sites, except for the trivalent chrome. The reactions of ionic exchange of Cr3+ and Zn2+ ions follow the models of pseudo-second order reaction. For the resins analyzed, the nature of ionic exchange reactions of the trivalent chrome is exothermic and of the zinc is endothermic.

A consideração explicita de troca iônica em soluções micelas conduz a expressões gerais que contém somente termos experimentalmente acessíveis. Estas expressões servem como marco de referência geral para a análise do efeito de micelas em reações que envolvem íons. As expressões incluem: a ligação de um íon reativo a micela na presença ou ausência de sal, a reação monomolecular de um substrato iônico na fase micelar, a reação bimolecular de um nucleófilo iônico na fase micelar e o efeito de micelas na dissociação de ácidos fracos e as suas consequências cinéticas. Estas expressões foram utilizadas para analisar quantitativamente a hidrólise alcalina de acetato de p-nitrofenila em tampão. Uma das predições do modelo, um mínimo no pK aparente de um ácido fraco na presença de micelas foi confirmado estudando o efeito de brometo de hexadeciltrimetilamônio na dissociação de n-heptilmercaptana e fenol. O efeito de sais no pK do fenol na presença de micelas, também predito pelo modelo, foi analisado quantitativamente. / The explicit consideration of specific ion exchange leads to general expressions which contain experirmentally accessible terms. These expressions serve as an unified conceptual framework for the quantitative dissection and analysis of the influence of charged interfaces on reactions which involve such specifically-bound ionic species. These include the binding of a reactive ion to the micelle in the presence ar absence of salt, the first order reaction of an ionic substrate in the micelle. a second order reaction of an ionic nucleophile solubilized in the micellar phase and the effect of micelles on the dissociation of weak acids and the reactions of the corresponding conjugate base. These expressions were used to analyze quantitatively the micellar modified hydrolysis of p-nitrophenyl acetate in the presence of buffer. One of the predictions of the model, a minimum in the pK apparent of a weak acid, was confirmed in a study of the effect of hexadecyltrimethylamonium bromide on the apparent pK's of phenol and n-heptylmercaptan. The effect of salts on the pK of weak acids in the presence af micelles, also predicted by the model, was analysed quantitatively.

Cette recherche visait à aborder l’effet des caractéristiques des eaux usées (c’est-à-dire les Co-contaminants, métaux lourds et pH) sur la réduction biologique du Séléniate (SeO42-), et évaluer l'intégration des processus et des configurations pour le traitement des eaux usées chargé de sélénium et de Co-contaminants.La première partie de l’étude portait sur l’effet des accepteurs de Co-électrons et le faible pH sur la bioremédiation du SeO42-, les études expérimentales a montré que le rapport molaire NO3- et SO42- à SeO42- a un facteur de contrôle en augmentant ou en diminuant l'efficacité de l'élimination du sélénium (Se). De plus, l'étude sur les interactions biofilm-Se a révélé la présence de NO3 ou de SO42- influence la spéciation Se, les niveaux de Se (Se0) biogénique et l'activité de la biomasse. Le fonctionnement du réacteur UASB (upflow anaerobic sludge blanket) avec une diminution progressive du pH influent de 7,0 à 5,5 a montré une performance d'élimination stable de NO3-, SO42 et SeO42- ,avant une diminution de 20% de l'élimination de tous ces composants à pH 5,0 En plus, le fonctionnement à long terme du réacteur UASB à pH 5.0 a l'enrichissement des familles Geobacteraceae et Spirochaetaceae, qui n'ont pas été détectés à pH> 5,0.La deuxième partie de l'étude a exploré l'efficacité de différentes techniques d'élimination pour le traitement de SeO42- avec des Co-contaminants. La comparaison des performances d’élimination SeO42- en présence de SO4-2 dans un filtre biotrickling (BTF) et un réacteur UASB a révélé que SO42- a largement influencé la croissance du biofilm attaché et l'élimination de SeO42-a augmentée de> 200%. D'autre part, l'élimination de SeO42- était similaire dans le réacteur UASB indépendamment de la présence ou de l'absence de SO42-. La caractérisation de la biomasse a révélé la formation de Se0 sphérique et de sulfure de poly-sélénium dans la biomasse des deux bioréacteurs. L'addition de Ni dans les deux bioréacteurs a entraîné une diminution des performances de suppression de SO42- et SeO42- de ~ 20-30%. L'élimination du Ni était> 80% dans les deux bioréacteurs. Ni a été éliminé par précipitation sous la forme de sulfure de nickel. L’évaluation du flux de processus pour l'élimination de SeO42- et SO42- a été effectuée en couplant la colonne d'échange d'ions (IX) et le bioréacteur UASB en utilisant soit un prétraitement (IX  UASB), soit un post-traitement (UASB  IX) pour le bioréacteur. Le schéma du processus de prétraitement a montré une meilleure efficacité d'élimination globale de 99% de SO42- et 94% de S totale atteignant <100 mg L-1 de SO42-, <0,3 mg L-1 de Se total et <0,02 mg L-1 de Se dissous dans l'effluent pendant 42 jours de fonctionnement continu / This research aimed at addressing the effect of wastewater characteristics (i.e. co-contaminants, heavy metals and pH) on the biological reduction of selenate (SeO42-) and evaluating process integration and configurations for selenium-laden wastewater treatment with co-contaminants. The first part of the study focused on the effect of co-electron acceptors and low pH on the bioremediation of SeO42-. Experiments showed that the molar ratio of NO3- and SO42- to SeO42- has a controlling factor in either increasing or decreasing the selenium (Se) removal efficiency. Additionally, study on biofilm-Se interactions revealed the presence of either NO3- or SO42- influences the Se speciation, biogenic Se (Se0) levels and biomass activity. Upflow anaerobic sludge blanket (UASB) reactor operation with a gradual decrease in the influent pH from 7.0 to 5.5 showed a stable removal performance of NO3-, SO42- and SeO42-, before a 20% decrease in removal of all these components was observed at pH 5.0. Furthermore, long-term operation of the UASB reactor at pH 5.0 showed the enrichment of Geobacteraceae and Spirochaetaceae families, which were not detected at pH > 5.0.The second part of the study explored the effectiveness of different removal techniques for the treatment of SeO42- with co-contaminants. Comparing the SeO42- removal performance in the presence of SO42- in a biotrickling filter (BTF) and UASB reactor revealed that SO42- largely influenced the attached biofilm growth and increased SeO42- removal by > 200%. On the other hand, SeO42- removal was similar in the UASB reactor irrespective of the presence or absence of SO42-. Biomass characterization revealed the formation of spherical Se0 and poly-selenium sulfide in the biomass of both bioreactors. Addition of Ni in both bioreactors led to a decrease in SO42- and SeO42- removal performance by ~20-30%. Ni removal was > 80% in both bioreactors. Ni was removed via nickel sulfide precipitation. Evaluation of integrated process system for SeO42- and SO42- removal was conducted by coupling an ion exchange column (IX) and UASB bioreactor, using IX as either a pre-treatment (IX  UASB) or post-treatment (UASB  IX) unit for the bioreactor. The pre-treatment process scheme showed a better overall removal efficiency of 99% SO42- and 94% total Se reaching < 100 mg L-1 SO42-, < 0.3 mg Se L-1 total Se and < 0.02 mg Se L-1 dissolved Se in the effluent over 42 days of continuous operation