Multistage nanofiltration membranes with adsorptive substrate for enhanced removal of emerging organic pollutants

Nanofiltration (NF) membranes, characterized by a molecular weight (MW) cut-off above 350 Da, demonstrate excellent water permeance and efficient rejection of large molecules. However, these membranes are inadequate for the removal of emerging organic pollutants (EOPs) around or below 300 Da. The presence of these EOPs is an increasing public concern due to their potential chronic health impacts and ecological disruptions, even at trace levels. In this study, we report a three-dimensional Kevlar hydrogel modified with polyaniline (PANI) nanofibers, which serves as the support membrane for creating multistage NF membranes with adsorptive substrate. These membranes feature an ultrathin polyamide active layer with a uniform distribution of pore size. Furthermore, the doping/dedoping chemistry of polyaniline endows the NF membrane with a tunable charge, allowing for improved selective [adsorption and small organic molecule separation from pharmaceutical and municipal wastewater. The prepared NF membranes have high adsorption capacity, enabling selective and fast molecular separation, and exhibit excellent dynamic processing capacity. The NF adsorption membrane achieves over 95 % removal of various EOPs (such as Methyl Orange, Bisphenol A, Tramadol) far exceeding the around 50 % rejection of commercial NF membranes and offers double the water permeance. Efficient EOPs capture through combined adsorption and NF rejection offers a strategy for preparing high-performance NF membranes for precise separation.