Chemical and surface engineered superhydrophobic patterned membrane with enhanced wetting and fouling resistance for improved membrane distillation performance

Abstract

Application of membrane distillation (MD) is still in its emerging stage due to membrane wetting and fouling issues. In this study, an anti-wetting and anti-fouling superhydrophobic patterned membrane was prepared utilizing patterned templet surface and subsequent chemical modifications with fluorine-based polymer. A uniform patterned polyvinylidene fluoride-co-chlorotrifluoroethylene (PVDF-CTFE) membrane was prepared using a template having a specific surface structure. It was found that the patterned membrane with a hierarchical microstructure was more hydrophobic than that with a flat surface. Long-term performance of the patterned membrane was determined through direct contact membrane distillation (DCMD). Results showed that such patterned membrane exhibited wetting resistance for a longer time compared to a pristine membrane. However, the patterned membrane showed rapid flux decline during a fouling test due to deposition of foulants such as humic acid (HA), alginate acid (AA), and bovine serum albumin (BSA). To overcome the fouling issue, a patterned membrane was chemically modified with 1H, 1H-perfluorooctyl methacrylate (FOMA) known to possess a low surface energy. After surface modification with FOMA, the superhydrophobic patterned membrane showed good stability in terms of water flux and salt rejection for more than 7 days in DCMD without wetting or fouling issue. Results of this study indicates the capability of a superhydrophobic patterned MD membrane for generating maximum water flux with excellent anti-fouling and wetting resistance properties.