Dual-layered nanocomposite substrate membrane based on polysulfone/graphene oxide for mitigating internal concentration polarization in forward osmosis

A novel thin-film composite (TFC) forward osmosis (FO) membrane with dual-layered substrate membrane was fabricated by a double-blade casting technique using different polysulfone (PSf) concentrations for top (15 wt%) and bottom (7 wt%) substrate layers. Graphene oxide (GO) was incorporated in the substrate layer, and the dual casting approach resulted in a membrane support with a highly porous bottom structure and a dense top skin layer on which the polyamide active layer was effectively formed. The dual-layered TFC PSf/GO membrane (TFC-PSf(d)GO) exhibited high water permeability, and ion selectivity was enhanced by the presence of well dispersed hydrophilic GO in the PSf substrate. The TFC-PSf(d)GO also exhibited the lowest specific reverse salt flux (J(s)/J(v) = 0.19 g L-1) and a more favorable structural parameter (S = 130 mu m) compared to GO-free membranes. Using deionized water as feed solution and 1 M NaCl as draw solution (DS), TFC-PSf(d)GO had J(v) = 33.8 L m(-2) h(-1) and J(S) = 6.9 g(-2) h(-1) under AL-FS mode, and J(v) = 61.5 L m(-2) h(-1) and J(s) = 14.0 g(-2) h(-1) under AL-DS mode. The potential of TFC-PSf(d)GO for commercial application was further evaluated by fabricating it with a fabric backing support (denoted as TFC-PSf(d)GO(f)). Compared to TFC-PSf(d)GO, TFC-PSf(d)GO(f) exhibited only 14% decline in its water flux. The overall results reveal that, fabrication of TFC substrate membrane via dual-blade casting approach along with GO incorporation produced high-performance TFC FO membranes which likely reduced the internal concentration polarization effects. (C) 2016 Elsevier Ltd. All rights reserved.