Mechanically strong Janus tri-bore hollow fiber membranes with asymmetric pores for anti-wetting and anti-fouling membrane distillation

Wetting, fouling and mechanical robustness are three major challenges constraining the commercial applications of membrane distillation (MD). Herein, we have developed a robust Janus tri-bore hollow fiber membrane with anti-wetting/fouling resistance. The unique membrane was fabricated by an oxidant-induced deposition of polydopamine/polyethylenimine (PDA/PEI) and a subsequent grafting of sodium-functionalized carbon quantum dots (Na+-CQDs) on top of a hydrophobic tri-bore polyvinylidene fluoride (PVDF) hollow fiber membrane. The PDA/PEI deposition resulted in a nanoporous top layer, and the Na+-CQD grafting significantly enhanced the membrane surface hydrophilicity. In MD operations, the nanoporous PDA/PEI layer endowed the membrane with an excellent rejection to surfactants, thus reducing the wetting propensity, while the grafted Na+-CQDs facilitated the formation of a surface hydration layer, thereby mitigating the oil fouling. This study may expand the applications of mechanically robust tri-bore MD hollow fiber membranes to desalinate hypersaline and harsh wastewaters containing amphiphilic and hydrophobic contaminants.