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Desenvolvimento de materiais híbridos metal-orgânicos (MOFs) incorporados em membranas de ultrafiltração para remoção eficiente de corantes de águas residuais
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Nesta dissertação foram desenvolvidos Metal Organic Frameworks (MOFs) e Covalent Organic Frameworks (COFs) para incorporação em membranas de acetato de celulose e posterior aplicação na adsorção de corantes. Os MOFs foram sintetizados por reações hidrotérmicas seguidos de evaporação lenta de solvente para promover a sua cristalização, os quais foram adicionados à solução polimérica para obter as membranas através do método de inversão de fases, originando uma membrana assimétrica. A estrutura dos MOFs/COFs e membranas preparados foi confirmada recorrendo a diversas técnicas de caracterização. Os MOFs foram analisados por difração de raio-X confirmando a sua estrutura tridimensional. A análise B.E.T. confirmou a microporosidade dos MOFs e COFs estudados em ensaios com adsorção de N2 e de CO2. A análise termogravimétrica (TGA) permitiu revelar uma maior estabilidade térmica para os COFs. Os espetros FTIR-ATR são semelhantes e confirmam a existência de grupos funcionais indicadores de compostos aromáticos. Por fim foi realizada análise SEM onde foi possível observar a estrutura de cada um dos COFs, evidenciando que algumas das estruturas eram filamentosas enquanto outras apresentam estrutura uniforme. Quanto às membranas de acetato de celulose estas foram analisadas estruturalmente por SEM no qual se observou a sua sua camada ativa, camada porosa e cross-section. Foi ainda avaliada a porosidade da membrana de forma extrapolada a partir da quantidade de água presente no interior de cada membrana. Quanto aos resultados de adsorção de corantes obtidos, os COFs apresentam resultados na ordem dos 80/90% de adsorção enquanto os MOFs apresentam resultados na ordem dos 70% de adsorção. Em relação aos processos de permeação com membranas de acetato de celulose o comportamento difere dependendo do corante em estudo e da natureza do mesmo.
Abstract In this dissertation, Metal Organic-Frameworks (MOFs) and Covalent Organic-Frameworks (COFs) were developed for incorporation into cellulose acetate membranes and subsequent application in the dye adsorption. MOFs were synthesized by hydrothermal reactions followed by slow solvent evaporation to promote their crystallization, which were added to the polymeric solution to obtain membranes through the phase inversion method, resulting in an asymmetric membrane. The structure of MOFs and COFs and the prepared membranes was confirmed using various characterization techniques. MOFs were analyzed by X-ray diffraction to confirme their three-dimensional structure. B.E.T. analysis confirms microporosity of MOFs and COFs studied with N2 and CO2 adsorption. The thermogravimetric analysis (TGA) allowed to reveal a greater thermal stability for the COFs. The FTIR-ATR spectra are similar and confirm the existence of functional groups indicators of aromatic compounds. Finally, a SEM analysis was performed where it was possible see the COFs structure, showing that some structures were filamentous while others had uniform structure. The cellulose acetate membranes were structurally analyzed by SEM in which its active layer, porose layer and cross-section was observed. The porosity of the membrane was also evaluated in an extrapolated way from the amount of water present inside each membrane. The adsorption results evidence that COFs present results in the order of 80/90% adsorption while the MOFs present results in the order of 70% adsorption. In relation to permeation processes with cellulose acetate membranes the behavior differs depending on the dye under study and the nature of the dye.
Abstract In this dissertation, Metal Organic-Frameworks (MOFs) and Covalent Organic-Frameworks (COFs) were developed for incorporation into cellulose acetate membranes and subsequent application in the dye adsorption. MOFs were synthesized by hydrothermal reactions followed by slow solvent evaporation to promote their crystallization, which were added to the polymeric solution to obtain membranes through the phase inversion method, resulting in an asymmetric membrane. The structure of MOFs and COFs and the prepared membranes was confirmed using various characterization techniques. MOFs were analyzed by X-ray diffraction to confirme their three-dimensional structure. B.E.T. analysis confirms microporosity of MOFs and COFs studied with N2 and CO2 adsorption. The thermogravimetric analysis (TGA) allowed to reveal a greater thermal stability for the COFs. The FTIR-ATR spectra are similar and confirm the existence of functional groups indicators of aromatic compounds. Finally, a SEM analysis was performed where it was possible see the COFs structure, showing that some structures were filamentous while others had uniform structure. The cellulose acetate membranes were structurally analyzed by SEM in which its active layer, porose layer and cross-section was observed. The porosity of the membrane was also evaluated in an extrapolated way from the amount of water present inside each membrane. The adsorption results evidence that COFs present results in the order of 80/90% adsorption while the MOFs present results in the order of 70% adsorption. In relation to permeation processes with cellulose acetate membranes the behavior differs depending on the dye under study and the nature of the dye.
Descrição
Palavras-chave
MOFs COFs Membranas de acetato de celulose Adsorção de corante Cellulose acetate membranes Dye adsorption