Application of diazonium-induced anchoring process on ultrafiltration substrate for the fabrication of nanofiltration membrane with enhanced desalination performance

Abstract

In membrane process, the lateral transport path of water molecule through substrate has a great impact on the permeance of thin-film composite (TFC) membrane, thus the optimization of substrate by constructing interlayer without affecting its pore structure is desired. Here, we report a facile, scalable and universal surface grafting strategy based on a diazonium-induced anchoring process (DIAP), for which an ultra-thin polyaminophenylene (PAP)-like layer is covalently grafted on the substrate. The PAP-like layer significantly increases the wettability of surface and pore as well as surface positive charges of substrate, but has little influence on its surface pore size and structure. Moreover, the effects of the anchored PAP-like layer on the distribution, release and uptake of piperazine (PIP) monomers during interfacial polymerization (IP) process are investigated systematically. The polyamide (PA) nanofiltration (NF) membrane made on this substrate features a highly cross-linked, thinner and smoother PA layer with less PA invasive, and highlights a 2-fold water flux increase and simultaneously enhanced divalent salts (Na2SO4, MgSO4 and MgCl2) rejections (above 98.0%). Thus, combined with the superior structural stability and antifouling property, the obtained TFC membrane holds great potential in water softening and household water purification.