Effects of different solvents on structures and performances of PVDF ultrafiltration membranes

PVDF ultrafiltration membranes were prepared by using L-S phase inversion techniques and the effects of four different solvents on the membrane structure and performance were discussed in this paper. Results showed that the considerations based on the thermodynamic parameters alone are not sufficient for predicting or explaining the structure nor the performance of the membrane eventually obtained, the membrane formation dynamic process should be taken into consideration. The water flux of PVDF ultrafiltration membranes were closely correlated with mutual diffusivities, the water flux increased as the Dm decreased. The SEM images showed that the pure water flux of PVDF membrane was not determined by the porosity of ultrathin surface layer alone, it could also be regarded as morphology of sublayer Mixed solvents (NMP/THF,NMP/AC) experiments showed that with the increase in acetone or tetrahydrofuran concentration, water flux and the pore size of PVDF membrane decreased, owing to the decrease in mutual affinity between solvent and water, as shown in the SEM images.