Novel polyarylene sulfide sulfone/amide tertiary amine membranes for organic solvent nanofiltration

Abstract

The development of membrane materials that are fouling-resistant and capable of achieving molecular separation from organic solvents is essential for industrial development. The strategy of introduction of zwitterionic compound amine oxide (AO) was proved to be an effective route. So, in this study, TA unit was introduced into polyarylene sulfide sulfone (PASS) molecular chain, then a facile one-step oxidation was conducted to convert the tertiary amine (TA) units in the membrane molecular chain to AO units. Through the oxidation treatment, the anti-fouling performance of the membranes was greatly improved with the Frr up to 95 % and F_ir down to 10 %, indicating the potential for long-term filtration. Interestingly, with the oxidation process, the thioether (−S–) units in the polymer chain were found to oxidize to strong polar sulfone groups (−SO₂–). Thus the rigidity of the molecular chain and the intermolecular interaction was significant enlarged, and the solvent resistance of the membrane was further enhanced. Also it is interesting that the membranes were transferred from ultrafiltration to loose nanofiltration membranes after the oxidation treatment. Then the oxidized membranes were conducted to organic solvent nanofiltration. The O-PASS/ATA membrane demonstrated a notable retention effect for dyes in ethanol, N, N-Dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP). The retention of Congo red was maintained at a level exceeding 95 %, while the permeance remained stable at a range of 7–16 L m⁻²h⁻¹ bar⁻¹. This work presents an effective method for the preparation of nanofiltration membranes for organic solvents and demonstrates significant potential for achieving molecular separation in organic solvents.