Fabrication of anti-fouling thin-film composite reverse osmosis membrane via constructing heterogeneous wettability surface

Anti-fouling properties are tightly related to the surface properties of reverse osmosis (RO) membranes. In our study, fluorinated polyethyleneimine (FPEI) was synthesized by introducing perfluoroalkyl groups into a hydrophilic polyethyleneimine (PEI) matrix, and the heterogeneous wettability surface with hydrophilic and low-surface-energy properties was constructed by grafting FPEI on membrane surface via the carbodiimide-induced method. Verified by the result analysis of SEM, AFM, and zeta potentials measurements, the fluorinated RO membrane surface presented denser, smoother, and reduced negative charge. The surface free energy of RO membrane surface after grafting FPEI decreased from 45.5 to 38.7 mJ/m(2). By using bovine serum albumin (BSA), humic acid (HA), and dodecyltrimethyl ammonium bromide (DTAB) as model foulants, the fluorinated RO membrane exhibits optimal fouling resistance and fouling release properties compared to pristine membrane and membrane modified by surface grafting hydrophilic PEI. Especially, the high recovery ratio (99%) and low total flux decline ratio (17.2%) were acquired during the filtration of BSA solution. These results manifested that the construction of a heterogeneous wettability surface can further improve the anti-fouling properties of RO membranes compared to a pure hydrophilic surface, and the corresponding anti-fouling mechanism was put forward.

Automated summary

The study synthesized fluorinated polyethyleneimine (FPEI) by introducing perfluoroalkyl groups into a hydrophilic polyethyleneimine (PEI) matrix, creating a heterogeneous wettability surface on reverse osmosis (RO) membranes. The fluorinated membrane exhibited improved anti-fouling properties compared to membranes with purely hydrophilic surfaces, with higher recovery ratios and lower flux decline ratios during filtration of foulants such as bovine serum albumin, humic acid, and dodecyltrimethyl ammonium bromide. These results suggest that surface modification with FPEI can enhance the fouling resistance of RO membranes.