Enhancing the permselectivity of thin-film composite poly(vinyl alcohol) (PVA) nanofiltration membrane by incorporating poly(sodium-p-styrene-sulfonate) (PSSNa)

Thin-film composite poly(vinyl alcohol) (PVA) nanofiltration membranes with improved permselectivity were prepared by incorporating poly(sodium-p-styrene-sulfonate) (PSSNa). Membranes were prepared through surface coating and in situ cross-linking procedure with porous polysulfone (PSf) membrane as support, PVA and PSSNa as coating materials, and glutaraldehyde as cross-linking agent. The effects of the incorporation of PSSNa on the membrane property and performance were investigated experimentally through ATR-FTIR spectroscopy, AFM analysis, streaming potential analysis, contact angle measurement and cross-flow permeation test. It was found that the incorporation of PSSNa resulted in increased membrane pore size, surface hydrophilicity and negative charge and thereby improved membrane permeability and solute selectivity. The PVA–PSf composite membrane exhibited a pure water flux of about 21.0 l/m2 h, NaCl rejection of 69.8% and Na2SO4 rejection of 96.5% when tested with 500 mg/l electrolyte aqueous solution at neutral pH and 5.0 bar, while the desired PSSNa/PVA–PSf composite membrane exhibited a higher pure water flux of 41.7 l/m2 h, lower NaCl rejection of 55.7% and higher Na2SO4 rejection of 98.3%. Moreover, compared with the PVA–PSf composite membrane, the PSSNa/PVA–PSf composite membrane possessed increased water flux and dye removal to anionic dye aqueous solution and improved fouling resistance to BSA aqueous solution.