Highly permeable benzene-trisulfonyl chloride-based polysulfonamide membranes fabricated by interfacial polymerization for acid-resistant nanofiltration

The fabrication of highly acid-resistant nanofiltration (NF) membranes with excellent separation performance via interfacial polymerization remains challenging due to the lack of precise pore architecture manipulation. Herein, novel acid-resistant nanofiltration membranes were fabricated based on benzene-1,3,5-trisulfonyl chloride (BTSC), which holds the characteristic resonant pi-backbonding structure and high steric hindrance, by interfacial polymerizing with polyethyleneimine (PEI) and piperazine (PIP) on the polyethersulfone (PES) substrate. The as-prepared PIP-BTSC/PES and PEI-BTSC/PES membranes displayed sub-nanometer pore sizes of 0.62 and 0.65 nm, respectively, with much narrower pore size distribution than the conventional acid-resistant NF membranes. Notably, the PEI-BTSC-H/PES membrane exhibited an MgCl2 rejection of 95.5 % and a high permeance of 43.5 L h-1 m- 2 bar-1. Besides, the PEI-BTSC/PES membrane exhibited excellent acid-resistance in the 72-day static acid soaking test and dynamic acid permeation experiment. Density functional theory calculation revealed that the outstanding acid-resistance of BTSC was ascribed to the much higher hydrolyzation energy barrier of the pol-ysulfonamide than conventional polyamide.