Morphological and separation performance study of PVDF/CA blend membranes

Polymeric membranes were prepared from blends of poly (vinylidene fluoride) (PVDF)/cellulose acetate (CA) via the phase inversion method induced by immersion precipitation. N,N-dimethylacetamide (DMAc) and water were used as solvent and coagulant (non-solvent), respectively. The effects of blend ratio on permeation, morphology, pore size and anti-fouling property of PVDF/CA membranes were investigated. Different techniques such as SEM, EDX, contact angle goniometry, mechanical tensile strength and filtration experiments of water and BSA were applied to evaluate the morphology and performance of membranes. The PVDF/CA membranes exhibited superior hydrophilicity compared to the neat membranes. However, the contact angle stopped decreasing when the CA/PVDF blend ratio was over 20%. Similar trend was noticed for the permeation flux of the membranes which can be interpreted due to porosity and morphology changes. Membranes mean pore size was calculated by FESEM photographs and filtration velocity method. The stability of membranes after sewage filtration has been studied by comparing pore size and surface composition of membranes before and after filtration. The results showed that the blend membrane with a CA/PVDF ratio of 30/70 showed increase in pore size and decrease in oxygen atomic percentage. The blend membrane with a CA/PVDF ratio of 20/80 showed the highest pure water flux and the lowest total fouling ratio and selected as the optimum blend membrane.