Hyperbranched poly(ionic liquid) functionalized poly(ether sulfone) membranes as healable antifouling coatings for osmotic power generation

Membrane fouling and membrane deterioration are two major concerns since they greatly worsen membrane performance in pressure retarded osmosis (PRO) and shorten the membrane lifetime. Herein, inspired by biological systems where microdamage induces an autonomous repair process, intrinsically healable poly(ionic liquid) (PIL) coating layers with sufficiently high mobility from short-distance electrostatic interactions have been fabricated by sequential immobilization of sulfonated hyperbranched polyglycerol (hbSPG) and quaternized polyethylenimine (QPEI) on polydopamine (PDA) pretreated poly(ether sulfone) (PES) membranes. XPS, SEM, and AFM results confirmed the successful incorporation of a PIL polymer pair onto the PES supports. Zeta potential analysis validated the charge alteration by electrostatic conjugation of the QPEI polymer onto the hbSPG modified surface. The antifouling and self-healing characteristics of the resultant PES-g-hbSPG-QPEI hollow fiber membranes were demonstrated by the excellent anti-protein adsorption behaviors and improved antibacterial performances on both non-aged and aged samples that were soaked in real municipal wastewater (WWRe) for two months. In PRO tests, the pristine PES membranes were contaminated seriously under high pressure operation, leading to a significant flux drop of 60%. In comparison, a flux reduction of 30% and a recovery rate of 98% after backflushing and hydraulic pressure impulsion on the non-aged membrane and a flux reduction of 40% on the aged membranes were observed. The intrinsically healable and antifouling PIL coating layers exhibit great potential of the developed strategy for the fabrication of high-performance PRO membranes toward osmotic power generation.