Polyarylene thioether sulfone/sulfonated sulfone nanofiltration membrane with enhancement of rejection and permeability via molecular design☆

Abstract Further improvement of nanofiltration is significantly hindered by the trade-off between the permeability and selectivity. This study proposes a new strategy of significantly improving performance by enhancing the effective membrane area, hydrophilicity, membrane porosity, negative charges of a membrane, and decreasing pore size through designing a new polyarylene thioether sulfone/sulfonated sulfone (PATS/SS) copolymer. Via copolymerization, thioether (-S-) and sulfonic groups were integrated in one polymer, endowing it with oxidizable properties, in combination with improved hydrophilicity, negative charges and membrane porosity. Nanofiltration membranes prepared from this copolymer are hydrophilic (contact angle: 69.1°) and negatively charged. After the -S- groups were altered to sulfone (–SO2–) units by a simple oxidization treatment, both hydrophilicity (contact angle: 37.9°) and surface charge were enhanced, rendering improved antifouling properties. Furthermore, the solvent stability of oxidized membranes was significantly improved, maintaining the structure intact even in N-methyl-2-pyrrolidone (NMP) for 24 h. Most importantly, a simultaneous enhancement of rejection (by 85.2%) and permeability (by 105%) of the membrane was observed when applied in nanofiltration for water purification and dye desalination, significantly improving performance compared to currently reported membranes.