Guanidinium-based loose nanofiltration membranes for dye purification and chlorine resistance

Loose nanofiltration membranes with high water permeance are desirable for the separation of dyes and salts; however, most membranes tend to be unstable when in contact with sodium hypochlorite solution, which has a significant influence on their properties. In this study, an innovative polymer membrane was fabricated on porous polyacrylonitrile substrates via interfacial polymerization, and a novel hydroxyl-containing guanidinium monomer (SaTGCl) were employed as an aqueous monomer. The fabricated polyester (PE) membranes exhibited high water permeance (97.2 L m−2 h−1 bar−1), high dye retention (99.4 %), and low salt retention (<15.8 %). Furthermore, the PE membranes exhibited exceptional molecular sieving for dye/salts or dye/dye mixtures. The SaTGCl-based PE membranes displayed prominent chlorine resistance when soaked in aqueous NaClO. The PE membranes also exhibited distinct antifouling properties. Hence, the newly developed guanidinium-based PE membranes have enormous application prospects in dye purification. This work lays the foundation for the use of hydroxyl monomers in constructing thin-film composite membranes for various separations.