New method for silica embedding on a PES membrane surface via in situ sol gel process and immobilization in a polyamide thin film composite

Abstract

A novel method to incorporate silica on a polyethersulfone (PES) membrane surface was successfully developed. An in situ hydrolysis/condensation of tetraethylorthosilicate (TEOS) precursor was carried out, followed by coating as thin film composite (TFC) via interfacial polymerization. PES membranes casted from 20 and 23wt.% PES in N-methyl-pyrrolidone (NMP) solutions were prepared by phase inversion. The membrane surfaces were modified by TEOS silica precursors, dispersed in ethanol at different concentrations (0.1, 0.3 and 0.5w/v%) and catalyzed by a NH3/H2O mixture. Immobilization of the prepared silica on the membrane surface was obtained by adding a polyamide coating. The modified membranes were characterized by FTIR, SEM, AFM, and TGA, which confirmed the successful embedding of silica particles by the in situ sol gel process. In the best conditions, rejection of MgSO4 and Na2SO4 reached 85 and 94.2% respectively. This was consolidated by a proportionally high water flux of 62.2 and 64.15Lm−2h−1 for MgSO4 and Na2SO4 salt solutions, respectively, at an operational pressure of 5bar.