Polymer Nanocomposites Reinforced with Modified Graphene Oxide: A Promising Material for Water Filtration

Abstract

Nanomaterial based polymer membranes are widely applicable for separation and purification industries. The present study is devoted to the fabrication of highly hydrophilic and antifouling polymer membranes based on graphene oxide (GO) and modified graphene oxide. Graphene oxide was prepared from graphite powder by Hummer’s method. Silver functionalized GO (GO-Ag), polyethylene glycol (PEG) functionalized GO-Ag (PEG-GOAg), magnetic iron oxide functionalized GO (GO/Fe3O4) and silver functionalized magnetic graphene oxide (Ag-GO/Fe3O4) were synthesized and used to fabricate six different series of polymer membranes by using vacuum filtration assembly. Fabricated membranes include PVC/GO and PVC-GO-Ag based membranes (0, 0.25, 0.5, 1.0 wt.%), PVDF-co-HFP/GO-Ag, and PVDF-co-HFP/PEG-GO-Ag membranes, (0, 0.2, 0.6, 1.0 ,1.4 wt.%) and PVDF-co-HFP/GO/Fe3O4 and PVDF-co-HFP Ag-GO/Fe3O4 (1.0 wt.%) based nanocomposite membranes. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to explore the structural and chemical features of nanocomposites and their perspective membranes. The dead-end filtration assembly was used to investigate the membranes performance. Water flux and BSA rejection was found to increase for all the nanocomposite based membranes as compared to pure polymer membranes. Besides this, GO-Ag nanocomposite showed appreciable antibacterial properties against Escherichia coli. PEG-GO-Ag (1.0 wt.%) nanocomposite was proved to be highly effective for enhancing the hydrophilicity of PVDF-co-HFP membrane by lowering the water contact angle from 115°.02 to 38°.77. The water flux of PVDF-co-HFP/PEG-GO-Ag (1.0 wt.%) membrane increased upto 906 Lm-2h-1 as compared to pristine PVDF-co-HFP which showed a water flux of 216 Lm-2h-1. GO/Fe3O4 and Ag-GO/Fe3O4 also enhances the water flux and BSA rejection of PVDF-co-HFP membrane. Flux recovery ratio for PVC/GO-Ag (0.5 wt.%) membrane was 85% while that of PVDF-co-HFP/PEG-GO-Ag (1.0 wt.%) membrane was 91% and PVDF-co-HFP/Ag- GO/Fe3O4 was 92%. Furthermore, the antifouling properties and reversible fouling ratios of all the fabricated membranes increased drastically. Thermo-gravimetric analysis (TGA) of the fabricated membranes confirms their high thermal stability as well. Reusability of fabricated membranes was also explored by cyclic filtration tests. The present study is a gateway to fabricate highly hydrophilic, antifouling and cost effective polymer membrane filters for high performance applications.