Degradation of forward osmosis (FO) membrane in multi-effect distillation (MED) brine: change of transport, physicochemical and anti-fouling properties

Abstract

This study investigated the chemical stability of various forward osmosis (FO) after static exposure to multi-effect distillation (MED) brine. The water flux, forward salt flux (FSF), and specific reverse salt flux (SRSF) were evaluated to evaluate the membrane performance degradation. The changes in the physicochemical properties of FO membranes were elucidated via characterization techniques including Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), goniometer, and zeta potential analyzer. Moreover, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) approach was used to predict the changes in the membrane fouling propensity. The results showed that the cellulose triacetate (CTA) membrane suffered deacetylation and chain cleavage due to hydrolysis, whereas the thin-film composite (TFC) membrane experienced degrafting due to oxidation. The selectivity reductions of both membranes were observed according to the increase in FSF and SRSF. Furthermore, the decreasing attractive XDLVO interaction energies of the degraded CTA membrane indicated the improvement of anti-fouling properties. In contrast, the anti-fouling properties of the TFC membrane were severely reduced since the attractive XDLVO interaction energies increased.