Solvent Activation for Building a Homogeneous Polyamide Layer to Enhance Reverse Osmosis Membrane Permeability

Abstract

Water scarcity has driven increased research on enhancing reverse osmosis (RO) membranes. Current research methods are time-consuming and not suitable for industrial applications. In this study, a more uniform PA layer with high hydrophilicity was prepared by utilizing dimethyl sulfoxide (DMSO) to optimize the interfacial polymerization process and 4-dimethylaminopyridine (DMAP) in postprocessing to improve water adsorption and transport. Characterization and molecular dynamics simulations showed that DMSO enhances the distribution state of trimesoyl chloride at the interface and acts as a cosolvent to optimize the monomer potential energy state during the interfacial reaction. This results in a thinner PA layer due to improved reaction homogeneity and monomer diffusivity. DMSO, as a polar aprotic solvent, enhances the nucleophilicity of DMAP, which effectively removes surface residues on the PA layer and weakens its spatial effects, leading to enhanced membrane permeability. The synergistic effect of DMSO and DMAP results in a high water permeance of 3.95 L m −2 h −1 bar −1 and maintains a high salt rejection of R NaCl = 98.47% (a 0.78% decrease) compared to the performance of the pristine RO membrane (1.42 L m −2 h −1 bar −1 , R NaCl = 99.25%). This study provides a simple strategy for the industrial preparation of highly permeable RO membranes and sheds light on the role of polar aprotic solvents and nucleophilic reagents in enhancing membrane permeance.