Enhanced performance of forward osmosis membranes by incorporating PVDF substrates with hydrophilic nanofillers

Abstract

Hydrophilic attapulgite (AT) and functional oxidized multi-walled carbon nanotubes (O-MWCNTs) are introduced to the polyvinylidene fluoride (PVDF) substrates to prepare improved performance of thin-film composite (TFC) membranes for forward osmosis (FO) process. The improved hydrophilicity of substrates can make for forming free-defect polyamide (PA) layer and enhance the permeability performance of the as-prepared TFC membranes. The effects of the single or composite addition of two nanofillers on the hydrophilicity, membrane morphology, porosity and mechanical strength of as-prepared substrates are investigated in detail. The results show that hydrophilic, porous and high-flux substrates are prepared and the corresponding TFC membranes own improved water flux and better selectivity. In a word, the PVDF/AT/O-MWCNTs TFC membrane receives a better water flux (Jv) of 28.23 and 20.37 L.m–2.h–1 and a lower reverse salt flux (Js) of 9.5 and 6.5 g.m-2.h-1 in pressure-retarded osmosis (PRO) mode (active layer facing draw solution, AL-DS) and FO mode (active layer facing feed solution, AL-FS). The draw solution and feed solution are 2M NaCl aqueous solution and deionized (DI) water, respectively. This study develops a brand-new way for preparing substrate for FO process.