Layered double hydroxide/graphene oxide hybrid incorporated polysulfone substrate for thin-film nanocomposite forward osmosis membranes

Abstract

Herein, we report the use of a layered double hydroxide/graphene oxide (LDH/GO) hybrid as a nanofiller for a polysulfone (PSf) substrate in the fabrication of a thin film nanocomposite (TFN) forward osmosis (FO) membrane. The influence of the incorporation of the LDH/GO hybrid on the physicochemical properties of the PSf substrate was explored and a systematic investigation of the resultant TFN membrane performance was conducted. The results demonstrate that the addition of the LDH/GO hybrid enhanced the PSf substrate with increased porosity, hydrophilicity, surface pore diameter, and mechanical strength. Consequently, all the TFN membranes obtained increased water permeability and salt rejection, as compared to the thin film composite (TFC) membrane prepared on a conventional PSf substrate. Using 1 M NaCl as the draw solution and DI water as the feed solution, the water flux of the TFN membrane with a 2 wt% LDH/GO dosage as high as 23.6 L m⁻² h⁻¹ was obtained under the pressure retarded osmosis (PRO) mode. Compared to conventional TFC membranes, the TFN membrane with a 2 wt% LDH/GO showed a very low reverse salt flux (6.2 g m⁻² h⁻¹). The improvement in FO performance is attributed to the lower structural parameters of the modified PSf substrate, and the reduction of the internal concentration polarization. This study suggests the LDH/GO hybrid is an effective additive for modifying the PSf substrate for the development of FO membranes.