Incorporating amphiphilic modifier into PVDF membrane through in-situ electrostatic crosslinking for efficient oil-water separation

Constructing stable amphiphilic membrane surfaces in a facile and controlled way is highly desired for fabrication of antifouling water purification membranes. Herein, inspired by adhesives of sandcastle worms, we proposed an in-situ electrostatic crosslinking method to incorporate amphiphilic modifiers into poly (vinylidene fluoride) membranes. Pluronic F127 grafted with positively charged quaternary ammonium groups are added into the casting solution, while perfluorosulfonic acid bearing negatively charged sulfonic acid groups and perfluorocarbon chains are dissolved in the coagulation bath. During non-solvent induced phase separation process, electrostatic crosslinking between quaternary ammonium and sulfonic acid led to the in-situ formation of amphiphilic modifiers on membrane surfaces and pore walls. The resulting membrane exhibits high water permeance up to 625 Lm-2h-1 bar-1 and superior antifouling performance with total flux decline ratio of 2 % and flux recovery ratio of 99.3 % for oil-water separation. Besides, the membrane displays excellent structural stability and self-cleaning properties against highly viscous crude oils.