Highly ordered mesostructured flexible silica-based nanofiltration membrane with satisfactory acid, chlorine, and fouling resistances

In this report, a highly ordered mesostructured flexible silica-based nanofiltration membrane is fabricated using tetraethyl orthosilicate (TEOS) as a silica source and Pluronic F127 copolymer as a structure directing agent, and hydrolyzed polyacrylonitrile ultrafiltration membrane as a substrate by an evaporation induced self-assembly approach. The results show the fabricated silica/F127 (SF) composite membrane possesses ordered mesostructures with different space groups depending on the mass ratios of TEOS/F127. The membrane is negatively charged with an isoelectric point at pH 2.9, and it also has a very hydrophilic surface. The pure water permeability of the membrane is 32 Lm−2h−1bar−1. The membrane also has high rejections to methyl blue (100%) and multivalent salts (> 95%), and moderate rejection to divalent salt (78.5% for Na2SO4). The ordering of the mesostructure enhances the membrane compactness, favoring the improvement of the separation performance. Additionally, the membrane possesses satisfactory resistances to humic acid (HA) and bull serum albumin (BSA) fouling, and bacteria adhesion due to the smooth and hydrophilic surface. Additionally, the salt rejection is stable in 0.5 M HCl for 11 h and/or active chlorine solution (pH = 5) with 9000 ppm·h chlorination strength accompanied by an obvious increase in permeate flux. The membrane also exhibits satisfactory performance stability in a long-term (168 h) running.