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

Publication date: 10 February 2017
Source:Polymer, Volume 110
Author(s): Sungil Lim, Myoung Jun Park, Sherub Phuntsho, Leonard D. Tijing, Grace M. Nisola, Wang-Geun Shim, Wook-Jin Chung, Ho Kyong Shon
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-PSfdGO) exhibited high water permeability, and ion selectivity was enhanced by the presence of well dispersed hydrophilic GO in the PSf substrate. The TFC-PSfdGO also exhibited the lowest specific reverse salt flux (Js/Jv = 0.19 g L^-1) and a more favorable structural parameter (S = 130 μm) compared to GO-free membranes. Using deionized water as feed solution and 1 M NaCl as draw solution (DS), TFC-PSfdGO had Jv = 33.8 L m⁻² h⁻¹ and Js = 6.9 g⁻² h⁻¹ under AL-FS mode, and Jv = 61.5 L m⁻²h⁻¹ and Js = 14.0 g⁻² h⁻¹ under AL-DS mode. The potential of TFC-PSfdGO for commercial application was further evaluated by fabricating it with a fabric backing support (denoted as TFC-PSfdGOf). Compared to TFC-PSfdGO, TFC-PSfdGOf 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.

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