The interfacial polymerization reaction induced by intermolecular dipole–dipole interaction for the preparation of nanofiltration membrane under the low concentration of the aqueous monomers

Abstract

In the process of interfacial polymerization for the fabrication of composite membrane, the addition of non-reactive materials in the aqueous or organic phase environment were often used to regulate the reaction rate in order to prepare composite membranes with a good performance, while ignoring the problem of difficult recycle of materials resulting in a waste of resources and secondary pollution. Herein, a reactive aqueous monomer 2-hydroxyethylhydrazin (0.05 % v/v) could combine with an ultra-low concentration piperazine (0.005 % w/v) to form a “transition state” coupling unit by the polar intermolecular dipole–dipole interaction, which could regulate the interfacial polymerization state under the concentration of impossible-formed membrane for forming a complete polyester-amide active layer. The membrane showed excellent performance with a Na₂SO₄ rejection of 96.76 % and a pure water flux of 12.77 L⋅m⁻²⋅h⁻¹⋅bar⁻¹. The mechanism of dipole–dipole interaction induced regulation of interfacial polymerization reaction rate was revealed through multi-scale assisted analyses such as the physicochemical characterization, the molecular dynamics simulation and the density functional theory calculation. This study provided a novel method for preparing nanofiltration membranes with low energy consumption and high efficiency, which could have a positive effect on the development of membrane technology.