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Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia Química e Bioquímica This work covers experimental and theoretical research related to the impact of the polymer structure of commercially available polyimide and polyetherimides as well as the formation conditions on the performance and structure of polyimide Organic Solvent Nanofiltration membranes. The influence in some membrane formation parameters such as polymer choice, solvent system composition, chemical crosslinking, solubility, humidity and coagulation bath temperature on the performance of PI membranes was investigated. A series of integrally skinned asymmetric membranes were prepared using different polyimide polymers, like Lenzing P84, P84 HT, Matrimid 5218 polyimide membranes and also polyetherimides membrane Ultem 1000. Non-crosslinked membranes were used to evaluate the influence of the polyimide choice and solvent system choice- DMF/1,4-Dioxane, NMP/THF and DMSO/Acetone in terms of performance and morphology. Non chemically modified membranes in DMF/1,4-Dioxane solvent system demonstrated low reproducibility. Polyimide P84 was found to generate tighter membranes with better rejection and higher flux performance than the other polyimides in study. Calculations were made to test the hypothesis that solubility parameters interaction can be a useful tool in theoretical predictions of PI OSN membranes performance and structure. Membrane formation conditions influenced membrane performance, but not to such extension as polymers and solvent system composition choice. SEM pictures revealed a significant difference in membranes morphology. The presence of macrovoids was higher in P84 and HT than in Matrimid and Ultem. These studies open up future possibilities for controlling the MWCO of different PI OSN membranes. |
