Boosting organic micropollutant removal and separation performance of polyamide nanofiltration membranes through...

The widespread occurrence of organic micropollutants (OMPs) has become a critical issue for water safety and the protection of public health. While nanofiltration (NF) offers a promising solution for OMP removal, most NF membranes prioritize high OMP rejection at the expense of water permeance, limiting their scalability. In this study, we presented highly selective NF membranes featuring a chitosan/polyvinyl alcohol/polyethylene glycol hydrogel interlayer that achieved both efficient OMP rejection and enhanced water permeance. The hydrogel interlayer facilitated the formation of a thinner, less cross-linked polyamide selective layer with optimized pore size, which synergistically enhanced water permeance. As a result, the pure water permeance increased substantially to 21.5 LMH/bar, more than double that of the control membrane (9.4 LMH/bar). Additionally, Na₂SO₄ rejection improved from 98.3 % to 99.3 %, and NaCl/Na₂SO₄ selectivity increased from 38 to 107, attributed to the enhanced negative charge. Molecular dynamics simulations indicated that the hydrogel interlayer modulated membrane properties by retarding piperazine monomer diffusion during interfacial polymerization. Additionally, the optimized membrane exhibited enhanced OMP rejection compared to control membrane, attributed to stronger electrostatic repulsion and reduced hydrophobic interactions due to enhanced negative surface charge and hydrophilicity. This work demonstrates an effective strategy for developing NF membranes with tailored properties, enabling advanced OMP removal and high water permeance for sustainable water reuse and production.