Reaction enhanced surface segregation method via phytic acid and Fe3+ complexation for high-performance nanofiltration membrane

Surface segregation is increasingly positioned as an in-situ modification strategy for engineering membranes with high hydrophilicity and enhanced selectivity. Herein, we propose a reaction enhanced surface segregation method mediated by complexation interaction to fabricate antifouling nanofiltration membrane for molecule/ion separation. The hydrophilic phytic acid (PA) is used as surface segregation agents in the casting solution, Fe 3+ with strong complexation capacity is used as the crosslinker in the coagulation bath. The complexation of PA with Fe 3+ improves PA surface segregation, immobilizing the PA-Fe 3+ complexes onto the membrane surface to construct hydrophilic and crosslinked separation layer. As a result, the optimized membrane possesses exceptional performance including high water permeability of 253 L/(m 2  h bar), high dye rejections (Methyl Blue: 97.9 %, Sunset Yellow: 96.3 %, Acid Fuchsin: 95.5 %, Methyl Orange: 78.8 %), dye/salt separation factor exceeding 300 and flux recovery ratio exceeding 95 % against surfactant-stabilized pump oil-in-water emulsion. Meanwhile, the membrane maintains high methyl blue rejection and low NaCl rejection during 168 h continuous filtration of a mixed solution (100 ppm methyl blue/1000 ppm NaCl). This study may establish a novel strategy for fabricating high permeability, selective and antifouling nanofiltration membrane by reaction enhanced surface segregation method.