The two most common commercial copper baths are the acid sulfate copper bath and the alkaline cyanide copper bath. Alkaline copper baths are mostly used to coat parts with complex geometry and to avoid galvanic deposition when depositing a metal on a less noble substrate. Because of the toxicity of cyanide compounds, alternative baths have been developed using different complexing agents. The starting point of the present study is a cyanide-free strike bath developed for copper plating on Zamak substrates developed by the Institute for Technological Research of the State of São Paulo/ Brazil. The replacement of a raw material such as cyanide must be economically advantageous and technically feasible. Therefore, this study intended to propose an alternative to the treatment of liquid wastes from the mentioned bath, aiming at simultaneous water reclamation and chemicals recovery in a closed system. The electrodialysis membrane separation process was studied, using a laboratoryscale system operating with a synthetic solution simulating the rinsing waters from the HEDP-based bath. The feasibility of the technique was evaluated by analyzing operational parameters such as ion extraction, demineralization rate, concentration rate, current efficiency for each anionic specie and average energy consumption. Because HEDP is a chelating agent, the transport of Cu(II)-HEDP chelates through anion-exchange membranes was also evaluated by means of electrochemical methods. Chronopotentiometric and current-voltage curves were constructed for different model solutions containing the same compounds as the original bath. A relation between the presence of chelates in the solutions and the fixed ion exchange group could be established. Lastly, deposition tests were performed using electrolytes containing the recycled inputs and the characteristics of the coatings were analyzed. The results showed that an electrodialysis stack using strongly basic anion-exchange membranes was suitable to produce treated solutions and a concentrate containing the ions from the bath. The concentrate could be added to the copper bath to compensate eventual drag-out losses without affecting the quality of the coatings. Thus, the application of electrodialysis was shown to be a feasible alternative for recovering water and inputs from the evaluated solution, reducing the wastewater generation and saving natural resources. / Os dois banhos de cobre comerciais mais comuns são o banho ácido à base de sulfato e o banho alcalino à base de cianeto. Os banhos alcalinos são usados principalmente para recobrir peças com geometria complexa e para evitar a deposição por deslocamento galvânico quando se deposita um metal em um substrato menos nobre. Por causa da toxicidade dos compostos cianídricos, banhos alternativos vêm sendo desenvolvidos usando diferentes agentes complexantes. O ponto de partida do presente estudo é um banho toque isento de cianeto para deposição de cobre em substratos de Zamak, desenvolvido pelo Instituto de Pesquisas Tecnológicas / Brasil. A substituição de matérias-primas como o cianeto deve ser economicamente vantajosa e tecnicamente viável. Desta forma, este estudo pretendeu propor uma alternativa para o tratamento de resíduos líquidos do banho mencionado, visando à recuperação simultânea da água e das matérias-primas em um sistema fechado. Foi estudado o processo de separação por membranas de eletrodiálise, usando um sistema em escala laboratorial operando com uma solução sintética que simulava as águas de lavagem do banho à base de HEDP. A viabilidade da técnica foi avaliada por meio da análise de parâmetros operacionais, como a extração dos íons, a taxa de dessalinização, o percentual de concentração, a eficiência de corrente calculada para cada espécie iônica e o consumo médio de energia. Devido ao HEDP ser um agente quelante, o transporte de quelatos Cu(II)-HEDP através de membranas aniônicas foi avaliado por meio de métodos eletroquímicos. Curvas cronopotenciométricas e curvas corrente-potencial foram construídas para diferentes soluções sintéticas que continham os mesmos compostos que o banho original. A relação entre a presença de quelatos nas soluções e os grupos fixos de troca iônica pôde ser estabelecida. Por fim, testes de deposição foram realizados usando eletrólitos contendo os compostos reciclados e as características dos depósitos foram analisadas. Os resultados mostraram que o sistema de eletrodiálise usando membranas aniônicas contendo grupos de troca fortemente básicos pôde produzir soluções tratadas e um concentrado contendo os íons do banho. O concentrado pôde ser adicionado ao banho original para compensar eventuais perdas por arraste sem afetar a qualidade dos depósitos. Assim, a aplicação da eletrodiálise se mostrou uma alternativa viável para a recuperação de água e de insumos da solução avaliada, reduzindo a geração de efluentes e economizando recursos naturais.

O principal impacto causado pela atividade de mineração de carvão é a poluição hídrica proveniente da drenagem ácida de minas (DAM), que pode ter efeitos toxicológicos nos ecossistemas aquáticos, como mortalidade, disfunções no crescimento, menores taxas de reprodução, deformidades e lesões. A DAM é formada através da oxidação de minerais de sulfeto, principalmente pirita (FeS2) e caracteriza-se por uma solução de pH ácido e metais dissolvidos (Fe, Al e Mn). Novas metodologias para o tratamento de efluentes contaminados com metais estão sendo estudadas e a eletrodiálise (ED) surge como uma destas tecnologias que tem se mostrado eficaz para a recuperação de água e concentração de eletrólitos. É considerada uma tecnologia atrativa aos mais diversos segmentos, uma vez que apresenta muitas vantagens sobre os processos tradicionais, tais como: não exige mudanças de fases; funciona de forma contínua; não necessita da adição de reagentes e não gera resíduos poluentes ao ambiente. A ED é uma técnica de separação por membranas, no qual espécies iônicas em solução são transportadas através de membranas de troca-iônica por influência da aplicação de um campo elétrico que permite a separação de ânions e cátions metálicos com a vantagem de remover os metais contaminantes e simultaneamente recuperar água e outros compostos de interesse industrial, como o ácido sulfúrico. No entanto, para a aplicação da ED alguns parâmetros devem ser estudados, buscando as melhores condições de uso. O parâmetro mais importante a ser analisado é o transporte dos íons através das membranas, avaliado no presente estudo através da cronopotenciometria e da obtenção das curvas de corrente-potencial (CVCs). Curvas cronopotenciométricas foram obtidas a partir de soluções sintéticas que representavam a composição de uma DAM a fim de se avaliar a passagem de ânions sulfato através de uma membrana aniônica (HDX 200), e o transporte de cátions metálicos, tais como Na+ e Fe3+, através de uma membrana catiônica (HDX 100). E as CVCs foram obtidas a partir das próprias DAMs também para a avaliação do transporte de íons e determinação de densidade de corrente limite a ser empregada na ED. Os resultados mostraram que os cátions avaliados desempenharam um papel significativo para o equilíbrio químico que leva à formação de diferentes espécies de complexos de cargas e mobilidade distintas. Diagramas de especiação em conjunto com os cronopotenciogramas permitiram a identificação de espécies complexas que conduzem a um transporte lento de íons através das membranas. A ED mostrou-se eficaz para a recuperação de água, removendo mais de 97,00 % dos contaminantes, e para a recuperação de ácido sulfúrico a partir da DAM, sendo obtidos percentuais de concentração de sulfatos superiores a 38,55 % e incrementos na acidez de até 236,88 %. / The main impact caused by coal mining activity is water pollution from acid mine drainage (AMD), that can have serious toxicological effects on aquatic ecosystems, such as mortality, growth disorders, lower rates reproduction, deformities and injuries. The AMD is formed by the oxidation of sulfide minerals, mainly pyrite (FeS2) and is characterized by a acid pH and dissolved metals (Fe, Al and Mn). New approaches for the wastewater contaminated with metals treatment are being studied and electrodialysis (ED) emerges as a new technology and has proven effective for the recovery of water and electrolyte concentration. The ED is considered an attractive technology to some segments since it presents several advantages on the traditional processes, such as: does not require phase changes; runs continuously, does not need reagents addition and does not generate waste polluting environment. Electrodialysis is a membrane separation technique in which ionic species in solution are transported, through ion-exchange membranes, under the influence of an electric field which allows anions and metallic cations separation, possessing the advantages of removing contaminant metals and simultaneously recovering water and other compounds of industrial interest, such as sulfuric acid. However, to implement the ED some parameters should be studied seeking the best conditions. The most important parameter to be studied is the ions transport across membranes, assessed in this study by chronopotentiometry and obtaining the current-voltage curves (CVCs). Chronopotentiometry curve were obtained from synthetic solutions representing the AMD composition in order to assess the passage of anions sulfate through a membrane anion (HDX 200), and transport of metallic cations such as Na+ and Fe3+, through a cation membrane (HDX 100). The CVCs were obtained from raw AMD also to evaluate the ions transport and determination of threshold current density to be employed in ED. The results showed that the cations evaluated played a significant role in the chemical balance which leads to the formation of different species of complexes of different fillers and mobility. Speciation diagrams with chronopotentiograms allowed the identification of complex species that lead to a slow ions transport across membranes. The ED was effective for water recovery removing more than 97.00 % of contaminants and to sulfuric acid recovery from the AMD, where has been obtained percentage of sulfate concentration above 38.55 % and an increase in acidity up to 236.88 %.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / Because of the constant introduction of new technologies to market growth of electronic waste generation has gained importance on the world stage, among these residues are cell phones. Deliver useful life increasingly short. Mobile phones are made up of several components, including LCD screens. In these screens there is a mixture of indium oxide (In) and tin (Sn), known as ITO, which 80-90% consists of In and 10-20% by Sn. There are already several studies that show ideal conditions for comminution and leaching of LCD screens, therefore, this study aims to establish an effective method for concentrating In present in aqueous solution coming from the acid leaching processes and thus regain In the form metal. Tests were conducted electrodialysis (ED), using synthetic solution In2(SO4)3 in order to work with a more environmentally acceptable method. Thus, initially tested for different current densities in a time of 120 minutes, monitoring pH and conductivity and varying the concentration of In every 30 minutes. The In concentration was determined by atomic absorption (AAS). The optimal current density was 0.96 mA/cm2, where was obtained 62.77% current efficiency. After setting the optimal current density applied in the same test of 131 hours, which resulted in a concentration of 521 mg/L In. Despite the use of electrodialysis have been able to concentrate the solution, the value of 521 mg/L is still not enough to recover In for electrowinning. Thus, we apply the solvent extraction method. Was used as DEHPA extractant diluted in commercial kerosene and evaluated the best contact time between the aqueous phase (A) and organic (O), pH, ratio A:O, better DEHPA concentration in the organic phase. For stripping evaluated the best molar concentration of HCl, relative A:O and contact time between phases. The best conditions laid down have been applied in real solution In, obtained leaching LCD screens, with concentration 32.44 mg/L. The best conditions are obtained in the extraction ratio A:O of 40:1, in 20 minutes, at pH 0,5 e obtained a 96,67% efficiency applied after the stripping in the loaded organic solution with In, with respect to 1:10 with concentration of HCl 4M in 10 minutes, resulting in a efficiency of 61,10% and concentration of 7,712 g/L In. Also performed were tests electrowinning (EO) evaluated three different current densities, and 150 A/m² was obtained a 50.71% efficiency at a concentration of 7 g/L. Therefore, two further phases in In recovery process were developed in recovering In its metallic form giving opportunity for new applications, reducing the consumption of natural resources. / Devido a constante introdução de novas tecnologias no mercado, o crescimento da geração de resíduos eletroeletrônicos tem ganhado importância no cenário mundial, dentre esses resíduos estão os telefones celulares. Estes equipamentos apresentam um tempo de vida útil cada vez mais curto. Os celulares são constituídos por diversos componentes, dentre eles as telas de LCD. Nessas telas há uma mistura de óxido de índio (In) e estanho (Sn), conhecida como ITO, onde de 80-90% é composta por In e 10-20% por Sn. Já existem diversos estudos que mostram condições ideais para cominuição e lixiviação das telas de LCD, assim sendo, este trabalho tem por objetivo estabelecer um método eficaz para concentrar o In presente em solução aquosa oriunda dos processos de lixiviação ácida e assim recuperar o In na forma metálica. Foram realizados testes de eletrodiálise (ED), utilizando solução sintética de In2(SO4)3, a fim de trabalhar com um método mais ambientalmente aceitável. Desta forma, inicialmente testou-se diferentes densidades de corrente em um tempo de 120 minutos, monitorando pH e condutividade e variação da concentração do In a cada 30 minutos. A concentração de In foi determinada por absorção atômica (AAS). A densidade de corrente mais adequada dentro das condições experimentais foi de 0,96 mA/cm2, onde se obteve 62,77% de eficiência de corrente. Após a definição da densidade de corrente ideal aplicou-se a mesma num ensaio de 131 horas, onde resultou em uma concentração 521 mg/L de In. Apesar do emprego da eletrodiálise ter conseguido concentrar a solução, o valor de 521 mg/L ainda não é suficiente para recuperar o In por eletro-obtenção. Desta forma, aplicou-se o método de extração por solventes. Utilizou-se como extrator DEHPA diluído em querosene comercial e avaliou-se o melhor tempo de contato entre as fases aquosa (A) e orgânica (O), pH, relação A:O, melhor concentração de DEHPA na fase orgânica. Para a re-extração avaliou-se a melhor concentração molar de HCl, relação A:O e tempo de contato entre as fases. As melhores condições estabelecidas foram aplicadas em solução real de In, obtida de lixiviação de telas de LCD, com concentração 32,44 mg/L. As melhores condições obtidas foram na extração a relação A:O de 40:1, em 20 minutos, com pH 0,5 e obteve-se uma eficiência de 96,67%, após aplicou-se a re-extração na solução orgânica carregada com o In, com relação de 1:10, HCl com concentração 4 M em 10 minutos, resultando em uma eficiência de 61,10% e uma concentração de 7,712 g/L de In. Também foram realizados testes de eletro-obtenção (EO), avaliando três diferentes densidades de corrente, sendo que com 150 A/m² obteve-se uma eficiência de 50,71%, com concentração de 7 g/L. Sendo assim, duas novas etapas no processo de recuperação de In foram desenvolvidas, recuperando In em sua forma metálica dando oportunidade para novas aplicações, reduzindo o consumo de recursos naturais.

Le présent travail porte sur l’étude comparative des procédés d’électrodialyse et d’électrodéionisation. Les possibilités d’application des procédés électro-membranaires à la production d’acide lactique par voie fermentaire sont investiguées. Deux axes de recherche sont choisis : le premier consiste à extraire de manière continue le lactate de sodium hors du milieu de fermentation. Pour cela, un empilement d’électrodialyse ne comportant que des membranes anioniques est couplé au fermenteur : environ 95 % des ions lactate sont extraits lors de l’opération. Par comparaison avec une fermentation témoin en mode batch, aucune inhibition de la fermentation n’est observée, et la productivité est multipliée par 13. Le deuxième axe de recherche consiste à convertir le lactate de sodium en acide lactique : un taux de purification comparable à celui obtenu en échange d’ions est recherché. Un procédé continu d’électrodéionisation à membranes bipolaires permettant d’atteindre 99,9 % de taux de conversion est élaboré pour le traitement de produit dilué. Est présentée finalement la modélisation mathématique d’un compartiment d’électodéionisation : les points expérimentaux sont fortement similaires aux points recalculés / This work deals with the comparative study of electrodialysis and electrodeionization. The possibilities to integrate the electro-membrane processes in the lactic acid fermentive production lines are investigated. Two main research ways are chosen : the first one lies in the continuous extraction of natrium lactate out of the fermentation middle. For this, an electrodialysis stack of only anionic membranes is coupled with the fermenter : approximately 95 % of lactate are removed during the operation. By comparison with a standard fermentation in batch mode, no inhibition is observed, and the productivity is increased by 13. The second way is to convert the natrium lactate in lactic acid : a high purity rate is seeked. A continuous electrodeioniation process including bipolar membranes, leading to 99,9% conversion rate, is elaborated for the treatment of diluted solutions. Finally is presented the mathematic calculation of an electrodeionization compartment : experimental points and calculated values are very similar

Vor dem Hintergrund des steigenden Lithiumbedarfs und der Ungleichverteilung der weltweiten Lithiumvorkommen gilt es auch, kleinere, heimische Vorkommen, wie die Zinnwalditlagerstätte bei Zinnwald/Cínovec, für eine mögliche Lithiumgewinnung zu untersuchen. Hierfür wurden zur Darstellung von Lithiumcarbonat zwei Verfahren entwickelt, optimiert und ökonomisch bewertet. Dabei konnte gezeigt werden, dass insbesondere das Direktcarbonatisierungsverfahren mit überkritischem CO2 aufgrund des geringen Chemikalienverbrauchs, der hohen Selektivität für Lithium, als auch dem breiten Anwendungsspektrum für weitere primäre und sekundäre Lithiumressourcen ein vielversprechender Ansatz für eine technische Umsetzung darstellt. Des Weiteren wurde die elektrodialytische Darstellung von Lithiumhydroxid untersucht und optimiert. Mittels einer erstellten Simulation wurden hierfür nicht nur Anforderungen an prozessierbare Ausgangslösungen definiert, sondern auch ein Aufbau zur Erhöhung der Prozessstabilität entwickelt, der eine kontinuierliche Filtration eines oder mehrerer Kreisläufe der Elektrodialyse erlaubt.

[ES] El fósforo es inherente al mantenimiento de la vida y desempeña un papel fundamental en la producción de alimentos. La inminente escasez de rocas fosfóricas, principal materia prima para la producción de fertilizantes a base de fósforo ha impulsado la investigación sobre la recuperación de este nutriente a partir de fuentes alternativas, como las aguas residuales municipales. En un estudio reciente, fue posible concentrar y recuperar fosfatos de una solución que simulaba aguas residuales municipales mediante electrodiálisis, además de promover la separación de fosfatos de los aniones coexistentes. Sin embargo, este proceso de separación comprometió la estructura de la membrana aniónica. Por lo tanto, el objetivo de este trabajo fue establecer las condiciones adecuadas para recuperar fosfatos de una solución con bajo contenido de este nutriente. Se realizaron experimentos de electrodiálisis bajo intenso campo eléctrico utilizando dos membranas aniónicas diferentes, una de origen chino (IONSEP-HC-A) y otra checa (AMHPP, resistente a medios alcalinos), caracterizándolas antes y después de los ensayos. Además, se estudiaron las reacciones químicas que acompañan al transporte de fosfatos a través de membranas aniónicas mediante voltamperometría lineal, cronopotenciometría y espectroscopia de impedancia electroquímica. Los resultados de las pruebas de electrodiálisis indican la posibilidad de separación de iones de fosfato utilizando la membrana IONSEP-HC-A, condición que no se logra con la membrana AMHPP. Mediante espectros FTIR se observó que la aplicación de campos eléctricos intensos provocó la transformación parcial de los grupos funcionales de ambas membranas. Sin embargo, además de esto, se notó la degradación de la malla estructural de la membrana china. Además, las imágenes SEM indicaron la formación de cavidades en la superficie de la membrana IONSEP-HC-A, lo que no se observó en la membrana AMHPP. A través de estas imágenes también se observó que la superficie de la membrana AMHPP tiene una mayor área conductora, lo que puede facilitar la formación de vórtices electroconvectivos, mientras que la distribución de grupos funcionales en la membrana IONSEP-HC-A facilitaría la disociación del agua. Estas suposiciones se confirman mediante espectros de impedancia y curvas cronopotenciométricas. Para la membrana AMHPP, las curvas cronopotenciométricas atestiguan que la electroconvección es el mecanismo predominante de transferencia de masa, a pesar de la presencia de arcos de Gerischer que indican la ocurrencia de reacciones químicas en la capa límite de difusión. En cuanto a la membrana IONSEP-HC-A, los resultados muestran el predominio de la disociación del agua, lo que dificulta el paso de los iones fosfato a través de la membrana y permite su separación. / [CA] El fòsfor és inherent al manteniment de la vida i exerceix un paper fonamental en la producció d'aliments. La imminent escassetat de roques fosfòriques, principal matèria primera per a la producció de fertilitzants a base de fòsfor ha impulsat la investigació sobre la recuperació d'aquest nutrient a partir de fonts alternatives, com les aigües residuals municipals. En un estudi recent, va ser possible concentrar i recuperar fosfats d'una solució que simulava aigües residuals municipals mitjançant electrodiálisis, a més de promoure la separació de fosfats dels anions coexistents. No obstant això, aquest procés de separació va comprometre l'estructura de la membrana aniònica. Per tant, l'objectiu d'aquest treball va ser establir les condicions adequades per a recuperar fosfats d'una solució amb baix contingut d'aquest nutrient. Es van realitzar experiments de electrodiálisis baix intens camp elèctric utilitzant dues membranes aniòniques diferents, una d'origen xinés (IONSEP-HC-A) i una altra txeca (AMHPP, resistent a mitjans alcalins), caracteritzant-les abans i després dels assajos. A més, es van estudiar les reaccions químiques que acompanyen al transport de fosfats a través de membranes aniòniques mitjançant voltamperometria lineal, cronopotenciometría i espectroscòpia d'impedància electroquímica. Els resultats de les proves de electrodiálisis indiquen la possibilitat de separació d'ions de fosfat utilitzant la membrana IONSEP-HC-A, condició que no s'aconsegueix amb la membrana AMHPP. Mitjançant espectres FTIR es va observar que l'aplicació de camps elèctrics intensos va provocar la transformació parcial dels grups funcionals de totes dues membranes. Tanmateix, a més d'això, es va notar la degradació de la malla estructural de la membrana xinesa. A més, les imatges SEM van indicar la formació de cavitats en la superfície de la membrana IONSEP-HC-A, la qual cosa no es va observar en la membrana AMHPP. A través d'aquestes imatges també es va observar que la superfície de la membrana AMHPP té una major àrea conductora, la qual cosa pot facilitar la formació de vòrtexs electroconvectivos, mentre que la distribució de grups funcionals en la membrana IONSEP-HC-A facilitaria la dissociació de l'aigua. Aquestes suposicions es confirmen mitjançant espectres d'impedància i corbes cronopotenciométricas. Per a la membrana AMHPP, les corbes cronopotenciométricas testifiquen que la electroconvección és el mecanisme predominant de transferència de massa, malgrat la presència d'arcs de Gerischer que indiquen l'ocurrència de reaccions químiques en la capa límit de difusió. Quant a la membrana IONSEP-HC-A, els resultats mostren el predomini de la dissociació de l'aigua, la qual cosa dificulta el pas dels ions fosfate a través de la membrana i permet la seua separació. / [EN] Phosphorus is inherent in maintaining life and plays a key role in food production. The imminent scarcity of phosphate rocks, the main raw material for the production of phosphorus-based fertilizers has boosted research on the recovery of this nutrient from alternative sources, such as municipal wastewater. In a recent study, it was possible to concentrate and recover phosphates from a solution simulating municipal wastewater through electrodialysis, as well as promoting the separation of phosphates from existing anions. However, this separation process compromised the structure of the anion-exchange membrane. Therefore, the objective of this work was to establish adequate conditions to recover phosphates from a low phosphate-containing solution. Electrodialysis experiments were carried out under intense electric field using two different anion-exchange membranes, one of Chinese origin (IONSEP-HC-A) and the other Czech (AMHPP, alkali-resistant), characterizing them before and after the tests. Furthermore, chemical reactions that accompany the transport of phosphates through anion-exchange membranes were studied using linear voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The electrodialysis results indicate the possibility of phosphates separation using the IONSEP-HC-A membrane, a condition not achieved with the AMHPP membrane. Through FTIR spectra, it was observed that the application of intense electric fields caused the partial transformation of the functional groups of both membranes. However, in addition to this, the degradation of the structural mesh of the Chinese membrane was noted. Furthermore, SEM images indicated the formation of cavities on the surface of the IONSEP-HC-A membrane, which was not observed for the AMHPP membrane. Through these images, it was also observed that the surface of the AMHPP membrane has a larger conductive area, which may facilitate the formation of electroconvective vortices, while the distribution of functional groups in the IONSEP-HC-A membrane would facilitate the dissociation of water. These assumptions are confirmed by means of impedance spectra and chronopotentiometric curves. For the AMHPP membrane, chronopotentiometric curves attest to electroconvection as the predominant mass transfer mechanism, despite the presence of Gerischer arcs indicating the occurrence of chemical reactions in the diffusion boundary layer. As for the IONSEP-HC-A membrane, the predominance of water dissociation was noted, making it difficult for phosphate ions to pass through the membrane and allowing their separation. / [PT] O fósforo é inerente à manutenção da vida e exerce um papel fundamental na produção de alimentos. A iminente escassez de rochas fosfatadas, principal matéria-prima para produção de fertilizantes a base de fósforo tem impulsionado pesquisas sobre a recuperação desse nutriente de fontes alternativas, como as águas residuárias municipais. Em estudo recente, foi possível concentrar e recuperar fosfatos de uma solução simulando uma água residuária municipal através da eletrodiálise, bem como promover a separação de fosfatos de ânions coexistentes. Entretanto, esse processo de separação comprometeu a estrutura da membrana aniônica. Assim sendo, o objetivo desse trabalho foi estabelecer condições adequadas para recuperar fosfatos de uma solução com baixo teor desse nutriente. Foram realizados experimentos de eletrodiálise mediante intenso campo elétrico utilizando diferentes duas membranas aniônicas, uma de origem chinesa (IONSEP-HC-A) e outra tcheca (AMHPP, resistente a meios alcalinos), caracterizando-as antes e após os ensaios. Ainda, foram estudadas as reações químicas que acompanham o transporte de fosfatos por membranas aniônicas empregando a voltametria linear, cronopotenciometria e a espectroscopia de impedância eletroquímica. Os resultados dos ensaios de eletrodiálise indicam a possibilidade de separação de íons fosfato usando a membrana IONSEP-HC-A, condição não atingida com a membrana AMHPP. Por meio de espectros de FTIR, observou-se que a aplicação de intensos campos elétricos ocasionou a transformação parcial dos grupos funcionais de ambas as membranas. Porém, adicionalmente a isso, notou-se a degradação da malha estrutural da membrana chinesa. Ainda, imagens de MEV indicaram a formação de cavidades na superfície da membrana IONSEP-HC-A, o que não foi observado para a membrana AMHPP. Por meio dessas imagens, observou-se também que a superfície da membrana AMHPP possui maior área condutora, podendo facilitar a formação de vórtices eletroconvectivos, enquanto a distribuição dos grupos funcionais na membrana IONSEP-HC-A facilitaria a dissociação de água. Essas suposições são confirmadas por meio de espectros de impedância e curvas cronopotenciométricas. Para a membrana AMHPP, curvas cronopotenciométricas atestam a eletroconvecção como mecanismo de transferência de massa predominante, apesar da presença de arcos de Gerischer indicando a ocorrência de reações químicas na camada limite de difusão. Já para a membrana IONSEP-HC- A, os resultados evidenciam a predominância da dissociação de água, dificultando a passagem de íons fosfato através da membrana e permitindo a sua separação. / Rotta, EH. (2023). Caracterização de membranas aniônicas e avaliação do transporte de íons fosfato em um sistema de eletrodiálise [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191741

Ce travail est une contribution à la conception d'un système portatif et intégré de type µTAS (micro-Total Analysis System) pour le traitement (préconcentration et simplification) de solution aqueuses contenant des métaux lourds et leur analyse en ligne. Pour la préconcentration amont, l'étude a porté sur la réalisation d'un micro-électrodialyseur manipulant des µL de solutions. L'optimisation des paramètres opératoires a permis d'augmenter d'un facteur 100 environ les concentrations d'analytes. Pour l'étage de détection aval, un système sur puce de type polarographique a été étudié. Le traditionnel mercure est remplacé par du diamant polycristallin dopé au bore (DDB) préparé par CVD micro-ondes. La quantification des métaux lourds par redissolution anodique sur ce matériau a été validée ainsi que les techniques de gravure compatibles avec la réalisation de microréseaux d'électrodes. / This work is a contribution to the conception of an integrated μTAS (micro-Total Analysis System) for treatment (preconcentration and simplification) of aqueous solutions containing heavy metals and their on-line analysis. For upstream preconcentration, a micro-electrodialyser handling µL of solutions was developped. The optimization of operating parameters permitted to reach an analyte pre-concentration factor of about 100. For the downstream detection step, an on-chip polarographic system, where mercury was replaced by boron doped diamond (BDD), was studied. BDD films were prepared by assited microwave plasma CVD. Quantification of heavy metals by anodic stripping on BDD was validated as well as the etching technique compatible with the realization of microarray electrodes.

L’électrodialyse (ED) est principalement basée sur l’action spécifique des membranes échangeuses d’ions (MEIs) et est largement répandue en industrie agroalimentaire pour la stabilisation tartrique des vins, la désacidification et le traitement des jus de fruits, la déminéralisation du lactosérum ou l’élimination et le fractionnement des protéines du lait. Le colmatage organique, accentué par la complexité de composition des effluents alimentaires et leur richesse en composés phénoliques, représente un facteur majeur de limitation de l’efficacité des procédés et des performances des MEIs. Ce phénomène provoque une diminution de la sélectivité de membranes, une augmentation de leur résistance électrique et réduit le rendement énergétique du procédé conduisant à des pertes économiques en industrie. Cette étude consiste principalement à étudier le décolmatage de MEIs par procédés chimiques et biologiques. Des lots de membranes échangeuses de cations (MECs) et d’anions (MEAs) neuves (1 lot de MEC et 1 lot de MEA) et usées (3 lots de MECs et 2 lots de MEAs) à différentes durées d’utilisation en ED dans l’industrie agroalimentaire –application confidentielle- ont été étudiés. L’ensemble des échantillons ont préalablement été caractérisés pour détermination des paramètres physicochimiques (capacité d’échange (CE), épaisseur (Tm), conductivité électrique (km), angle de contact (θ), teneur en eau (WC) ainsi que la fraction volumique de la solution inter-gel (f2) résultant de l’exploitation du modèle microhétérogène), de structure et morphologiques par spectroscopie IR-TF, microscopie optique, microscopie électronique à balayage et mécaniques par essais de traction. Les effets directs et indirects (causés par les opérations de lavage régulières en industrie) du colmatage ainsi que l’anisotropie des propriétés mécaniques de membrane ont été mis en évidence. Des méthodes de nettoyage non agressives et respectueuses de l’environnement ont été expérimentées en mode statique en ex-situ : Solutions salines (NaCl à 35 g.L-1 et eau de mer reconstituée), solution hydro-alcoolique (mélange eau-éthanol 12%, pH=3,5) et solutions biologique utilisant 3 catégories d’agents enzymatiques (Rohalase BX-BXL, β-glucanase / Corolase 7089, endo-peptidase / Tyrosinase, polyphenol-oxydase) dont les conditions opératoires d’activité enzymatiques optimale ont été déterminées. L’évolution de CE, km, θ et f2 ont été suivis en fonction de la durée de nettoyage. Les solutions salines ont un effet négligeable sur le nettoyage en profondeur mais restent efficaces pour le nettoyage de surface. Cependant, l’application de la solution hydro-alcoolique et des solutions d’enzymes se sont avérées être efficaces pour le décolmatage interne et externe et parviennent à rétablir significativement les paramètres suivis. Il a été démontré que les composés phénoliques, principaux constituants des effluents traités, sont en majeure partie responsables du colmatage des MEIs. Ceux-ci forment des nanoparticules colloïdales denses, non perméables aux ions dans les méso- et macropores des MEIs et ne pénètrent pas dans ses micropores. Une modification du modèle microhétérogène selon cette hypothèse a permis de fournir une interprétation adéquate du km et de modéliser la modification structurale de la phase inter-gel engendrée par les mécanismes de colmatages de polyphénols et expliquer les raisons de diminution du facteur f2app. Une méthode d’extraction utilisant un mélange de solvants (25%V/V, acétone/méthanol/isopropanol/eau) a été mise au point et a permis d’extraire certains composés phénoliques de différents lots de MECs et MEAs usées et ont été identifiés par chromatographie liquide à haute performance. Il a été démontré que les interactions entre les composés phénoliques et la matrice polymère étaient principalement régies par l’empilement des cycles aromatiques et des interactions électrostatiques du type CH-pi et pi-pi ainsi que les liaisons hydrogènes / Conventional electrodialysis (ED) is mainly based on the specific action of ion exchange membranes (IEMs) and is widely used in food industry for tartaric stabilization of wines, deacidification and treatment of fruit juices, demineralization of whey or elimination and fractionation of milk proteins. The organic fouling, accentuated by the complex composition of the food effluents and their richness in phenolic compounds, represents a major limitative factor of the process efficiency and the IEMs performance. This phenomenon causes a decrease in the selectivity of membranes, an increase in their electrical resistance and reduces the energy efficiency of the process leading to economic losses in industry. This study mainly consists in studying the IEMs cleaning by chemical and biological methods. Two batches of new membranes (cation- (CEMs) and anion-exchange membranes (AEMs)) and five batches of used ones (3 CEMs and 2 AEM) with different durations of use in ED units in food industry -confidential application- have been studied. All the samples have been previously characterized to determine their physicochemical parameters (ion-exchange capacity (IEC), thickness (Tm), electrical conductivity (km), contact angle (θ), water content (WC) and the volume fraction of the inter-gel solution (f2) resulting from the study of the micro heterogeneous model), structure and morphology by FTIR spectroscopy, optical microscopy, scanning electron microscopy and mechanical by tensile strength tests. The direct and indirect effects (caused by the regular cleaning operations in industry) of fouling as well as the anisotropy of the membranes mechanical properties have been highlighted. Non-aggressive and environmentally friendly cleaning methods have been experimentally tested in ex-situ static mode: Saline solutions (35 g.L-1 NaCl and reconstituted seawater), hydro-alcoholic solution (12% water-ethanol mixture, pH = 3,5) and biological solutions using 3 categories of enzymatic agents (Rohalase BX-BXL, β-glucanase / Corolase 7089, endo-peptidase / Tyrosinase, polyphenol oxidase) whose operating conditions of optimal enzymatic activity have been determined. The evolution of IEC, km, θ and f2 were followed in function of the cleaning duration. Saline solutions have a negligible effect on intern cleaning but remain efficient for extern cleaning. However, the application of the hydro-alcoholic solution and enzyme solutions have been found to be efficient for both intern and extern cleaning and led to significant recoveries of the studied parameters. It has been shown that phenolic compounds, the principal constituents of treated effluents, are mainly responsible for MEIs fouling. Apparently, they form dense colloidal nanoparticles not permeable for ions within membrane meso- and macropores, not penetrating into micropores. A modification of the micro heterogeneous model under this assumption allowed an adequate interpretation of km and the modelization of structural modifications of the inter-gel phase generated by the fouling mechanisms by polyphenols and explained the reasons why the f2app decreases. An extraction method using a mixture of solvents (25% V/V, acetone/methanol/ isopropanol/water) was developed and made it possible to extract certain phenolic compounds from different batches of used CEMs and AEMs that were identified by high performance liquid chromatography. It has also been demonstrated that the interactions between the phenolic compounds and the polymer matrix are mainly governed by the stacking of aromatic rings and electrostatic interactions of the CH-pi and pi-pi type as well as the hydrogen bonds

Le présent travail vise à étudier le couplage de l’échange d’ions et de l’électrodialyse. Cette étude est appliquée à la séparation de biomolécules. Un des objectifs est de diminuer la génération d’effluents salins produits par les étapes d’échange d’ions utilisées de façon classique dans les bioséparations. Une première approche a conduit à la conception d’une architecture avec un mode de fonctionnement cyclique en 3 étapes qui permet de purifier certaines familles de peptides sans utiliser de tampon de pH ni générer d’effluents. Le dispositif expérimental est constitué d’une cellule d’électrodialyse dans laquelle sont introduites des résines échangeuses d’anions. Les trois étapes sont les suivantes : fixation des biomolécules sur la résine initialement sous forme carbonate, élution par une solution de dioxyde de carbone dissous dans l’eau, électrorégénération de la résine sous sa forme initiale, conduisant simultanément à la régénération de la solution d’acide carbonique. L’étape d’électrorégénération a été modélisée et les simulations permettent d’améliorer la compréhension des processus couplés mis en jeu comme les équilibres d’échange d’ions, les équilibres en solution, l’électromigration. Une deuxième approche a ensuite consisté à étudier les possibilités de contrôle du pH par voie électrochimique, afin de limiter l’utilisation de solutions tampons. La dissociation de l’eau, conduisant à la formation de protons et d’ions hydroxyles, a été plus particulièrement étudiée en mettant à profit les propriétés des contacts dits « bipolaires » sous l’effet d’un champ électrique. Il s’est alors avéré que les choix du type de résine et de la densité de courant permettent de jouer sur le pH Toutefois ce travail doit être poursuivi par la recherche d’architectures et de modes opératoires qui permettent d’obtenir un pouvoir tampon adéquat / The present work aims to study the coupling of ion exchange and electrodialysis. This study is applied to the separation of biomolecules. One objective is to reduce the generation of saline wastewater produced by the ion exchange steps used conventionally in bioseparations. One approach has led to the design of architecture with a cyclic mode in 3 steps to purify some families of peptides without using a buffer pH or generate wastes. The experimental device consists of an electrodialysis cell in which are introduced anion exchange resins. The three steps are: loading of biomolecules on the resin initially in the carbonate form, elution with a solution of carbon dioxide dissolved in water, electroregeneration of the resin in its original form leading simultaneously to the regeneration of the carbonic acid solution. Using a modelling of the electroregeneration step, simulations can improve the understanding of coupled processes as the ion exchange equilibria, the equilibria in solution, the electromigration. A second approach has then been to study the possibilities of controlling the pH by electrochemical means to limit the use of buffers. The dissociation of water, leading to the formation of protons and hydroxyl ions, has been particularly studied by accounting the properties of contacts called « bipolar » as a result of an electric field. It was established that the choice of resin type and the current density can modify the pH. However this work must be pursued through research of architectures and operating procedures that deliver appropriate buffer capacity

The ability to produce potable water economically is the primary focus of seawater desalination research. There are numerous methods to desalinate water, including reverse osmosis, multi-stage flash distillation, and multi-effect evaporation. These methods cost more than potable water produced from natural resources; hence an attempt is made in this research project to produce potable water using a modified high-efficiency jet ejector in vapor-compression distillation. The greater efficiency of the jet ejector is achieved by properly mixing propelled and motive streams. From experiments conducted using air, the pressure rise across the jet ejector is better in case of one or two mixing vanes and the highest back pressure (pinch valve closed 83.33%). At other pinch valve closings, the air velocity through the jet ejector was high, so the extra surface area from the mixing vanes caused excessive friction and lowered the efficiency.