A novel high selectivity, strong acid resistance and antifouling polyamide thin film composite nanofiltration membrane fabricated with 3,3′-diamine-Tröger's base

The conventional polypiperazinamide thin film composite (TFC) nanofiltration (NF) membrane is easy to lose its separation performance under strong acidic conditions due to the hydrolysis of piperazine-amide bonds. In order to break through the bottleneck, in this study, a novel methane-free Tröger's base diamine monomer was proposed for fabricating high-performance polyamide thin-film composite nanofiltration (TFC NF) membranes. Firstly, the novel 3,3′-diamine-Tröger's base (DATB) monomer was synthesized and added into the polyethersulfone solution to fabricate the polyamide TFC NF membrane via non-solvent induced phase inversion (NIPs) followed by interfacial polymerization (IP). Thereinto, the DATB based NF membrane prepared with 1.0 wt% DATB and 0.075 w/v% TMC exhibited favorable rejection to Na 2 SO 4 (98.1 %) under neutral conditions, as well as high rejection to heavy metal ions at pH 1 (99.6 % of Fe 3+ , 97.3 % of Ni 2+ and 96.7 % of Cr 3+ ) and good selective separation factors (68.6 of Fe 3+ /H + , 31.8 of Ni 2+ /H + and 25.8 of Cr 3+ /H + ). Meanwhile, this membrane showed high rejection to dyes at pH 1 such as 99.1 % for crystal violet (CV), 99.5 % for rhodamine B (RDB), 96.4 % for eriochrome Black T (EBT), and 99.3 % for congo red (CR), respectively. Especially, the DATB based NF membrane had excellent acid resistance, and its rejection of Na 2 SO 4 only decreased by 8.8 % and remained >89.3 % after soaking in 20 wt% H 2 SO 4 solution for 30 days. Interestingly, this NF membrane also showed good antifouling property, and its water flux always did not decrease during the recovery of FeCl 3 at pH 1. Obviously, the distinct V-shaped rigid TB configuration concurrently provided the DATB-derived nanofiltration membrane with excellent resistance to acids, enhanced selectivity, and antifouling performance. This study offers a promising strategy for manufacturing TFC NF membranes with enhanced acid stability and performance.