One-step fabrication of robust polyvinyl chloride loose nanofiltration membranes by synthesizing a novel polyether amine grafted styrene-maleic anhydride copolymer

Abstract

Loose nanofiltration membrane possesses obvious advantages for treating textile wastewater to recycle the useful resources. However, the increasingly complicated composition of wastewater has raised significant challenges to the efficient separation of dye/salt mixtures and antifouling properties. Herein, a novel polyether amine grafted styrene-maleic anhydride polymer (SMA-g-PEA) was synthesized and utilized as the additive for fabricating PVC-based loose nanofiltration membranes. Segregated amphiphilic SMA-g-PEA in the membrane formation created uniform macropores on the surface due to its pore-forming ability, and the self-crosslinking and accelerated phase inversion generated a thin nanofiltration separation layer. By adjusting the grafting degree of PEA, the optimized PVC/SMA-g-PEA membrane displayed high rejections of methyl blue (96.4 %), Congo red (93.3 %) and acid fuchsin (68.6 %) and extremely low rejections of NaCl (0.18 %), Na2SO4 (4.75 %) and MgSO4 (2.24 %) due to the combination of size sieving and electrostatic interaction. Importantly, it also exhibited a permeate flux of 210 L/m2·h·bar during filtering the methyl blue/NaCl solution and a dye/salt selectivity of 31.93. Moreover, a strong and stable hydration layer was constructed on the membrane surface by integrating the amphiphilic characteristic of SMA-g-PEA and zwitterion potential in acid environment. Consequently, the antifouling properties were dramatically elevated by “fouling resistant” and “fouling release” strategies.