Preparation of highly selective nanofiltration composite membranes based on a novel soluble rigidly contorted monomer

Abstract

AbstractNanofiltration composite membranes with high selectivity are one of the most critical cores in water treatment, and regulating the surface charge and pore structure of active separation layers in thin film composite membranes is one of the most effective means to improve the selectivity of composite membranes. This article synthesized a novel monomer with positive charge and a rigid twisted Tröger's base structure (named TBDA‐SO3), which was manipulated to improve the microporous structure and surface charge of the composite membrane. By interfacial polymerization, TBDA‐SO3, and piperazine were co‐reacted with trimesoyl chloride to successfully prepare positively charged, highly selective, and strongly microporous polyamide composite nanofiltration membranes. The best‐performing composite nanofiltration membrane in this article has a permeability similar to that of the control group's poly(piperazine amide) (PPA) membrane (pure water flux, 7.8 L m−2 h−1 bar−1), but has excellent divalent cation selectivity (52.57), which is 4.4 times that of the control group's PPA membrane.