Development of a novel dual-bioinspired method for synthesis of a hydrophobic/hydrophilic polyethersulfone coated membrane for membrane distillation

This study presented a novel method for the surface modification of a hydrophilic polyethersulfone (PES) membrane via dip-coating. The performance of the new membrane was investigated in a membrane distillation process. The surface free energy (SFE) of the modified PES was studied by the Owens-Wendt method. A significant decrease of surface free energy from 36.1 mN/m to 16.4 mN/m was observed after modifying the membrane surface with fluoro-organothiol (1H, 1H, 2H, 2H-perfluorodecanethiol). The water contact angle of the membrane increased from 66 degrees for PES to 115 degrees for surface-modified membrane. This remarkable increase suggests a successful switch from hydrophilicity to hydrophobicity owing to the creation of hierarchical submicro/nanostructures on the surface of PES. This structure was achieved by depositing polydopamine and silver nanoparticles, followed by lowering the surface free energy by fluoro-organothiol treatment. The performance of the modified membranes was evaluated through a direct contact membrane (DCMD) process in the presence of anionic and non-ionic surfactants and high salt concentrations (4.5 wt%). The membranes reached a high and stable flux of approximately 39.37 kg/m(2)h after surface modification. Besides, the newly engineered membranes had excellent stability during long-term operation, showing a salt rejection rate of 99.80% after 36-h.

Automated summary

This study introduced a novel method for surface modification of PES membrane, successfully transforming it from hydrophilic to hydrophobic and improving membrane performance, achieving high flux under high salt concentrations, and demonstrating excellent stability during long-term operation.