Etching Strategy for Nanofiltration Membranes Prepared with Two-Dimensional Nanochannels for Seawater Desalination

Abstract

Up to now, developing nanofiltration (NF) membranes with outstanding salt rejection and excellent permeability has become a crucial challenge. In this work, thin film composite (TFC) membranes containing two-dimensional nanochannels were successfully prepared using 2D Mg(OH)2 nanosheets as sacrifice templates. The nanosheets were dispersed in trimethyl chloride/n-hexane and then incorporated into the polypiperamide layer by interfacial polymerization. The introduction of Mg(OH)2 and etching with H2SO4 (pH = 3) can increase membrane flux without rejection loss. The 2D nanochannels provided additional transport routes for water molecules. The prepared TFC membranes formed a root-like morphology on the surface, along with a thinner selective layer and lower cross-linking, contributing to the increase in water flux. Therefore, the desalination performance of etched membranes was better than control membranes. The membrane made from 0.05 wt % Mg(OH)2 shows a Na2SO4 rejection of 98.25%, and water flux increases by 72.8%. The TFC membranes prepared in this work have high stability in operation and have even better antifouling properties. This approach provides a new strategy for the preparation of high-performance NF membranes, which is applied in seawater desalination.