Mechanism insights into the role of the support mineralization layer toward ultrathin polyamide nanofilms for ultrafast molecular separation

Abstract

In this study, a highly perm-selective thin-film composite (TFC) nanofilm was successfully developed via silicification interlayer-mediated interfacial polymerization. The silicification interlayer, fabricated in situ, significantly improved the surface hydrophilicity of the polysulfone (PSf) substrate and facilitated the high-density uptake of amine monomers. The interlayer also served as a quasi-molecular-scale regulator that decelerated the diffusion of amine monomers into the organic phase to polymerize with the acyl chloride of 1,3,5-benzenetricarbonyl trichloride (TMC). The synergistic effects triggered self-sealing and inhibited the membrane growth, which promoted the formation of ultrathin polyamide (PA) nanofilms (approx. 13 nm) with enhanced crosslinking properties. The best-performing PA_SiO₂/PSf membrane exhibited a high water permeance of 14.5 L m⁻² h⁻¹ bar⁻¹, which was approximately three times the permeance of the pristine PA membrane (4.8 L m⁻² h⁻¹ bar⁻¹). Furthermore, the membrane exhibited a high rejection capability toward divalent salts (98.7% against Na₂SO₄) and mono/divalent ion selectivity of 60.9. Hence, the newly developed PA_SiO₂/PSf membrane exhibits competitive separation properties compared to the state-of-the-art desalination membranes. The technique is applicable to the majority of conventional interfacial polymerizations, which highlights its use in the development of high-performance membranes for water remediation.