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(-2)h(-1)bar(-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 center dot 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.

Automated summary

A highly ordered mesostructured flexible silica-based nanofiltration membrane was successfully fabricated using TEOS and Pluronic F127 copolymer as the silica source and structure directing agent, respectively. The membrane showed different mesostructures depending on the mass ratios of TEOS/F127, and exhibited a negatively charged and hydrophilic surface. It demonstrated excellent permeability, high rejections to methyl blue and multivalent salts, and satisfactory resistances to fouling and bacteria adhesion. The membrane also exhibited stability in acid and active chlorine solutions, and showed long-term performance stability.