Structural analysis of PES nanoporous membranes under different conditions of preparation

In this study we have focused on the structure of the prepared membranes which have been fabricated under different conditions. First, the different concentrations of polyethersulfone (PES) (15, 20 and 25 wt%) for preparation of casting solution were used. Then by adding polyethyleneglycol (PEG) in different concentrations (2, 5 and 8 wt%) and different molecular weights (200, 600, 1500), the membranes were prepared via the immersion precipitation procedure in a non-solvent bath (water) with different temperatures (5 and 35°C). The flat-sheet membranes were characterized using scanning electron microscope which shows remarkable changes in the morphology and structure of prepared membranes. Flux and rejection capability of membranes were estimated using pure water and salts, respectively. Structural analysis of membranes show that the membrane including 25 wt% PES has the narrow pores or voids (nearly 3 μm) comparing to the membrane composed of 15 wt% PES (about 7 μm). Results show that introducing PEG changes the hydrophilicity and viscosity of casting solution. The membrane with 20 wt% PES which in the amount of PEG 1500 is about 2 wt% shows the best performance. The rejection of this membrane is in the order of Na2SO4 > MgSO4 > NaCl.