Facile and novel fabrication of high-performance loose nanofiltration membranes for textile wastewater recovery

Loose nanofiltration (LNF) membranes can be used to treat textile wastewater if the membranes meet stringent criteria on permeability, selectivity, and structural stability. In this work, a novel LNF membrane was developed by interfacial polymerization (IP) process between 1,3,5-tris(4-aminophenyl) benzene (TAPB) and trimesoyl chloride (TMC). The structure of TAPB, which is a symmetric and non-planar triamine monomer with four benzene rings, is beneficial for the formation of a rigid active layer with a uniform pore size and high porosity. This novel LNF membrane was fabricated in two steps. First, TAPB was blended with polyether sulfone (PES) to prepare a substrate via the phase inversion process. Second, TMC was cross-linked with the TAPB-embedded PES substrate via the IP reaction. The microstructure, surface properties, and dye/salt separation performance of the novel LNF membranes were systematically investigated in this study. The optimized membrane showed outstanding water permeance (185.8 L m-2 h-1 bar-1), low salt rejections (22.4 % for Na2SO4 and 12.4 % for NaCl), and excellent rejection for various dyes (99.8 % for Congo Red, 99.1 % for Direct Red 23, 98.1 % for Reactive Black 5 and 88.8 % for Reactive Orange 16). Moreover, the resultant membrane showed excellent stability and antifouling properties during a long-term filtration test of 72 h using aqueous dye/salt mixtures. This study provides a facile and novel IP strategy to fabricate high-performance LNF membranes by using water -insoluble amine monomers, which have a high potential for dye/salt separation applications.