Preparation and Characterization of Organic Solvent-resistant Polybenzimidazole Membranes

Abstract

Recently, solvent-resistant nanofiltration membranes have been studied for the separation of solvents or solutes using a molecular weight cut-off system of the polymer which is resistant to a specific solvent. Required conditions for these membranes must have are excellent physical properties and solvent resistance. Polybenzimidazole, which is known to be one of the most heat-resistant commercially available polymers, has an excellent inherent solvent resistance and it is even insoluble in stronger organic solvents when cross-linked. Therefore, in this study, the applicability of polybenzimidazole as a solvent resistant nanofiltration membrane was discussed. The membrane was fabricated using the non-solvent induced phase separation method and showed a suitable morphology as a nanofiltration membrane confirmed by field emission scanning electron microscopy. In addition, the permeance of the solvent in the presence or absence of cross-linking was investigated and the stability was also confirmed through long operation. The permeance test was carried out with five different solvents: water, ethanol, benzene, N, N-dimethylacetamide (DMAc) and n-methyl-2-pyrrolidone (NMP); each of the initial flux was 6500 L/m(2)h (water, 2 bar), 720 L/m(2)h (DMAc, 5 bar), 185 L/m(2)h (benzene, 5 bar), 132 L/m(2)h (NMP, 5 bar), 65 L/m(2)h (ethanol, 5 bar) and the pressure between 2 and 5 bar was applied depending on the type of membrane.