Providing an energy efficient recycle for the Teflon® synthesis process is of great interest due to environmental and economic reasons. This recycle step involves separating CO2 from a stream containing scCO2 and valuable monomer (C2F4). Membranes provide economical and environmental friendly separations compared to conventional methods (e.g. distillation, amine absorption). Therefore, I am investigating membrane materials that are well-suited for this important separation. Developing a robust membrane that can withstand the aggressive scCO2 environment (~1070 psi of CO2) is a key challenge. Supercritical CO2 swells traditional polymeric membrane materials, thereby increasing segmental mobility of the polymer chains which leads to a decrease in separation capacity. There have been no polymeric membrane materials identified in the literature which are suitable for this separation. In this work, I have identified an advanced polymer, Torlon® (a polyamide-imide), that solves this problem. After determining the appropriate material, it is important to choose a membrane morphology that is industrially desirable. The asymmetric hollow fiber membrane morphology provides the highest productivity. I have successfully produced defect-free asymmetric hollow fiber membranes using Torlon® that withstand high pressure feeds. These membranes have been shown to provide selective separations under scCO2 conditions without being plasticized. To further improve the separation performance of Torlon® membranes, mixed matrix concept was explored. Zeolite 4A, which is relatively more permeable and selective compared to Torlon®, was chosen as the sieve material. Mixed matrix membranes from Torlon® and zeolite 4A were made and their separation performance was measured. Based on these experimental measurements and Maxwell modeling, challenges in making successful mixed matrix membranes were identified and feasible solutions for these challenges are suggested.

La anodización es un proceso electrolítico que convierte la superficie metálica en un recubrimiento de óxido insoluble. El aluminio es el material anodizado con más frecuencia. El llamado “abrillantado” del aluminio se realiza comúnmente con baños de ácido fosfórico concentrado. Después de la anodización, las piezas deben enjuagarse cuidadosamente, y es en ésta operación en la que se produce una dilución de la solución del baño arrastrada en la capa de óxido formada. Es en este aspecto donde se plantea la mejora de la calidad medioambiental del sector mediante un plan de recuperación y reutilización de los ácidos diluidos en las aguas de lavado, especialmente del ácido fosfórico. Las membranas son una herramienta atractiva que ofrece un amplio rango de aplicaciones, especialmente en el campo de la alimentación, bebidas, bioquímica, etc. Hay muchos ejemplos que pueden encontrarse en el tratamiento de efluentes, la desalinización de aguas o la concentración de soluciones. La separación de diferentes componentes se consigue por la acción de una membrana separadora y por la influencia de una fuerza impulsora a ambos lados de la membrana (presión, concentración, campo eléctrico). Son objetivos de este trabajo: Realizar un aporte a la investigación sobre la recuperación de materia prima en efluentes industriales mediante técnicas de membrana El eficaz aprovechamiento de la materia prima mediante el reciclado de los ácidos a los baños de anodizado La reducción del volumen de aguas residuales finales, con la correspondiente reducción en la contaminación ambiental del medio receptor La elaboración de una propuesta técnico-económica innovadora en el sector del recubrimiento metálico Los principales resultados obtenidos son: Se ha encontrado que las membranas de nanofiltración DK de Osmonics y la MPF-34 de Koch permiten una adecuada separación entre el Al3+ y los ácidos fosfórico y sulfúrico de las aguas de lavado. Los rechazos promedio (del ensayo de concentración) de Al3+ y H3PO4 para la membrana MPF-34 son de 99,7% y de 66,9% respectivamente y para la membrana DK de 99,5% y de 32,3% respectivamente. - Se han desarrollado expresiones para poder estimar adecuadamente los rechazos de Al3+, H3PO4 y H2PO4- en función de la composición del alimento con la membrana MPF-34. Se ha visto que estos valores son los intrínsecos de la membrana. Estas expresiones se obtuvieron mediante un estudio fenomenológico debido a que la complejidad del problema no permite hacerlo desde el punto de vista mecanístico. Se ha encontrado que la estabilidad de la membrana DK en el medio ácido del alimento es suficiente para asegurar un funcionamiento adecuado a nivel industrial. Un tratamiento utilizando la membrana DK permite una recuperación del 73% del ácido fosfórico. En el ácido fosfórico recuperado la relación Al/H3PO4 es de 0,11% en peso mientras que en la disolución alimento inicial era de 6%. Se ha visto que las membranas tanto poliméricas como cerámicas con un PMC de 1000 Da o más no permiten una recuperación adecuada del ácido fosfórico, debido a que el máximo rechazo de Al alcanzado ha sido del 58%. Para las condiciones estudiadas y debido a la naturaleza del las disoluciones tratadas la electrodiálisis no permite una recuperación adecuada del ácido fosfórico Se ha visto que la UFAP no permite separar el Al debido a que no es posible formar complejos Al-Polímero en medios ácidos como el del alimento. La adición de especies que permitan variar el pH de las disoluciones complicaría la recuperación del ácido debido a la presencia de impurezas adicionales. / Most of the hazardous waste in a metal finishing operation comes from the wastewater generated by rinsing operations. The acidic solution that is dragged out from the bath into the following rinsing tanks is the primary source of contamination of rinse water. The use of acidic solutions is very common in metal processing. Sulphuric acid, hydrochloric acid, phosphoric acid, chromic acid and nitric acid are used in chemical bath for anodising, galvanising, brightening, plating and pickling process. The known strategies to reduce the pollution in the wastewater effluent are based on the recovery of contaminant compounds to be recycled to the process reducing the expense in fresh compounds. By definition, recycling includes all measures in order to reduce volume of effluent by recovery raw materials from wastewaters. Membrane separation has become a competitive technology to traditional water treatment processes because of highly effective in removing most inorganic and organic contents to produce a very pure effluent.

Este trabalho tem como objetivo preparar membranas compostas de α-alumina recobertas com paládio usando a técnica de deposição química electroless plating associada ao método sol-gel. Foram realizados tratamentos térmicos a 1450°C nos suportes cerâmicos em 6, 12, 18, 24 e 30 h visando verificar a influência do tempo na porosidade do mesmo. Foram preparadas membranas compostas, alumina-Pd com uma, duas e três camadas de paládio na superfície externa do suporte cerâmico, em que o suporte e as membranas foram caracterizados por: análise morfológica realizada por Microscopia Eletrônica de Varredura (MEV) e Microscopia Eletrônica de Varredura de Emissão de Campo (FESEM), porosidade avaliada pelo Método de Brunauer, Emmet e Teller (BET), Método de Barret-Joyner-Halenda (BJH) e porosimetria de mercúrio, quantificação de paládio em solução por Espectrometria de Massa com plasma indutivamente acoplado (ICP-MS) e a permeabilidade e seletividade dos gases mensurada a partir de um equipamento em escala de bancada. O aumento do tempo durante a sinterização não promoveu mudanças significativas na porosidade do suporte, mostrando que o tempo de 6 h de tratamento térmico é suficiente para atingir a menor distribuição de tamanho de poro do material. A formação da camada de paládio foi realizada sem e com a associação do método sol-gel, apresentando uma camada mais homogênea com o uso do método, no entanto a análise de ICP-MS indicou maior quantidade de metal paládio na deposição electroless plating. A análise morfológica indicou espaços vazios menores de acordo com o número de camadas formadas. O suporte cerâmico sem e com camada de paládio apresenta variação na permeabilidade aos gases N2, CH4 e CO2 nas pressões de 100 a 400 kPa e quanto mais espessa a camada de paládio formada, menor é a permeabilidade dos gases. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-02-23T18:54:16Z No. of bitstreams: 1 Dissertacao Tatiana Bisoto.pdf: 546380 bytes, checksum: b684b58eaa3e2af8b355719394be7208 (MD5) / Made available in DSpace on 2015-02-23T18:54:16Z (GMT). No. of bitstreams: 1 Dissertacao Tatiana Bisoto.pdf: 546380 bytes, checksum: b684b58eaa3e2af8b355719394be7208 (MD5) / Within this context, this work aims to prepare membranes composed of α-alumina coated with palladium using the electroless plating technique associated with the sol-gel method. To achieve the objectives of the paper, analyzes of porosity of the ceramic support with and without heat treatment of 1450°C for 6; 12; 18; 24 and 30 h, the formation of one, two and three layers of palladium on the external surface of the ceramic support, the effect of the sol-gel method, the chemical and physical properties, permeability and selectivity of the gases were performed. Morphological analysis were performed by Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscope (FESEM), the membrane porosity was evaluated by the Brunauer, Emmet and Teller (BET) theory, Barret-Joyner-Halenda (BJH) method and by mercury porosimetry, the palladium quantification in solution was given by mass spectrometry with inductively coupled plasma (ICP-MS) analysis and gas permeability and selectivity were measured by a bench scale equipment. The time increase during the sinterization did not promote representing changes in the support porosity, which shows that the 6 h time of heat treatment is sufficient to achieve the lowest porosity of the material. The palladium layer formation was realized without and with the combination of the sol-gel method, presenting a more homogeneous layer with the use of the method. However, the ICP-MS analysis indicated a greater amount of palladium deposition without sol-gel method. The morphological analysis showed smaller empty spaces according to the number of layers formed. The ceramic support without and with palladium layer showed variation in permeability to N2, CH4 and CO2 gases at pressures of 100 to 400 kPa and the higher the palladium layer formed, the smaller the gas permeability

Este trabalho tem como objetivo preparar membranas compostas de α-alumina recobertas com paládio usando a técnica de deposição química electroless plating associada ao método sol-gel. Foram realizados tratamentos térmicos a 1450°C nos suportes cerâmicos em 6, 12, 18, 24 e 30 h visando verificar a influência do tempo na porosidade do mesmo. Foram preparadas membranas compostas, alumina-Pd com uma, duas e três camadas de paládio na superfície externa do suporte cerâmico, em que o suporte e as membranas foram caracterizados por: análise morfológica realizada por Microscopia Eletrônica de Varredura (MEV) e Microscopia Eletrônica de Varredura de Emissão de Campo (FESEM), porosidade avaliada pelo Método de Brunauer, Emmet e Teller (BET), Método de Barret-Joyner-Halenda (BJH) e porosimetria de mercúrio, quantificação de paládio em solução por Espectrometria de Massa com plasma indutivamente acoplado (ICP-MS) e a permeabilidade e seletividade dos gases mensurada a partir de um equipamento em escala de bancada. O aumento do tempo durante a sinterização não promoveu mudanças significativas na porosidade do suporte, mostrando que o tempo de 6 h de tratamento térmico é suficiente para atingir a menor distribuição de tamanho de poro do material. A formação da camada de paládio foi realizada sem e com a associação do método sol-gel, apresentando uma camada mais homogênea com o uso do método, no entanto a análise de ICP-MS indicou maior quantidade de metal paládio na deposição electroless plating. A análise morfológica indicou espaços vazios menores de acordo com o número de camadas formadas. O suporte cerâmico sem e com camada de paládio apresenta variação na permeabilidade aos gases N2, CH4 e CO2 nas pressões de 100 a 400 kPa e quanto mais espessa a camada de paládio formada, menor é a permeabilidade dos gases. / Within this context, this work aims to prepare membranes composed of α-alumina coated with palladium using the electroless plating technique associated with the sol-gel method. To achieve the objectives of the paper, analyzes of porosity of the ceramic support with and without heat treatment of 1450°C for 6; 12; 18; 24 and 30 h, the formation of one, two and three layers of palladium on the external surface of the ceramic support, the effect of the sol-gel method, the chemical and physical properties, permeability and selectivity of the gases were performed. Morphological analysis were performed by Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscope (FESEM), the membrane porosity was evaluated by the Brunauer, Emmet and Teller (BET) theory, Barret-Joyner-Halenda (BJH) method and by mercury porosimetry, the palladium quantification in solution was given by mass spectrometry with inductively coupled plasma (ICP-MS) analysis and gas permeability and selectivity were measured by a bench scale equipment. The time increase during the sinterization did not promote representing changes in the support porosity, which shows that the 6 h time of heat treatment is sufficient to achieve the lowest porosity of the material. The palladium layer formation was realized without and with the combination of the sol-gel method, presenting a more homogeneous layer with the use of the method. However, the ICP-MS analysis indicated a greater amount of palladium deposition without sol-gel method. The morphological analysis showed smaller empty spaces according to the number of layers formed. The ceramic support without and with palladium layer showed variation in permeability to N2, CH4 and CO2 gases at pressures of 100 to 400 kPa and the higher the palladium layer formed, the smaller the gas permeability

No description available.

No description available.

Ce travail porte sur l'amélioration de la sélectivité préférentielle d'une membrane cationique à base d’ETFE pour une utilisation en électrodialyse afin de traiter des effluents industriels contenant un mélange d’acides et de sels métalliques. Pour cela, nous avons fait appel à la méthode de la modification chimique de la surface d’une membrane cationique par la formation d’un film superficiel mince portant des charges positives afin de former une barrière de répulsion électrostatique pour des cations bivalents tout en permettant le passage de cations monovalents tels que les protons.<p>La synthèse de la membrane cationique de base a été réalisée en passant par différentes étapes à savoir :le greffage du styrène - divinylbenzène (DVB), la chlorosulfonation et l’hydrolyse. <p>Au cours de ce travail, nous avons mis au point un protocole de greffage du styrène-DVB dans le film d’ETFE qui permet l’obtention d’un film ayant un taux de greffage reproductible assurant à la membrane cationique finale une bonne conductivité électrique et une capacité d’échange acceptable pour une membrane d’électrodialyse. Une étude de la réaction de greffage en fonction de la concentration en réticulant a été réalisée. <p>Nous avons procédé par la suite à la modification de la surface du film d’ETFE greffé styrène-DVB par la formation d’une couche superficielle mince fixée par des liens covalents. Les membranes modifiées ont été obtenues par la réaction d’une seule face du film d’ETFE greffé chlorosulfoné avec la 3-diméthylaminopropylamine. La modification chimique de la surface du film ETFE greffé chlorosulfoné a été suivie par la technique FTIR-ATR. L’effet de la concentration de la diamine sur les propriétés électrochimiques des différentes membranes modifiées a été étudié. La résistance électrique des membranes modifiées équilibrées au contact de solutions de chlorure de sodium et d'acide sulfurique a été mesurée par la technique d’impédance. La détermination du nombre de transport du proton et de l’ion sodium a été réalisée à partir de mesures du potentiel de membrane. La densité de courant limite des membranes a été évaluée sur base des courbes courant-tension. Les mesures de chronopotentiométrie ont été également effectuées sur les différentes membranes synthétisées.<p>Les résultats de ces caractérisations montrent que la modification de la surface engendre des changements considérables au niveau des propriétés électrochimiques des membranes résultantes. La résistance électrique, la densité de courant limite ainsi que les propriétés de transport de la membrane dépendent d’une part de la concentration de la diamine utilisée et d’autre part de la solution dans laquelle la membrane modifiée est équilibrée. <p>La sélectivité préférentielle des différentes membranes vis-à-vis des protons par rapport aux ions bivalents a été testée en réalisant des électrodialyses d’un milieu mixte H2SO4-NiSO4. Nos résultats montrent que la modification chimique de la surface de la membrane affecte d’une manière significative le transport des ions nickel tout en respectant le passage des protons. Une meilleure séparation a été obtenue pour une membrane modifiée en utilisant la diamine pure.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The use of hydrophobic porous polymer membranes to vent unwanted gas bubbles from liquid streams is becoming increasingly more common in portable applications such as direct methanol fuel cells (DMFCs) and micro-fluidic cooling of electronic circuits. In order for these portable systems to keep up with the ever increasing demand of the mobile user, it is essential that auxiliary components, like gas-liquid separators (GLS), continue to decrease in weight and size. While there has been significant progress made in the field of membrane-based gas-liquid separation, the ability to miniaturize such devices has not been thoroughly addressed in the available literature. Thus, it was the purpose of this work to shed light on the scope of GLS miniaturization by examining how the amount porous membrane required to completely separate gas bubbles from a liquid stream varies with operating pressure. Two membrane characterization experiments were also employed to determine the permeability, k, and liquid entry pressure (LEP) of the membrane, which provided satisfying results. These parameters were then implemented into a mathematical model for predicting the theoretical membrane area required for a specified two-phase flow, and the results were compared to experimental values. It was shown that the drastically different surface properties of the wetted materials within the GLS device, namely polytetrafluoroethylene (PTFE) and acrylic, caused the actual membrane area requirement to be higher than the theoretical predictions by a constant amount. By analyzing the individual effects of gas and liquid flow, it was also shown that the membrane area requirement increased significantly when the liquid velocity exceeded an amount necessary to cause the flow regime to transition from wedging/slug flow to wavy/semi-annular flow.