Abstract
Graphene oxide (GO) nanosheets were utilized as a selective layer on a highly porous polyvinyl alcohol (PVA) nanofiber support via a pressure-assisted self-assembly technique to synthesize composite nanofiltration membranes. The GO layer was rendered stable by cross-linking the nanosheets (GO-to-GO) and by linking them onto the support surface (GO-to-PVA) using glutaraldehyde (GA). The amounts of GO and GA deposited on the PVA substrate were varied to determine the optimum nanofiltration membrane both in terms of water flux and salt rejection performances. The successful GA cross-linking of GO interlayers and GO-PVA via acetalization was confirmed by FTIR and XPS analyses, which corroborated with other characterization results from contact angle and zeta potential measurements. Morphologies of the most effective membrane (CGOPVA-50) featured a defect-free GA cross-linked GO layer with a thickness of ~67 nm. The best solute rejections of the CGOPVA-50 membrane were 91.01% for Na2SO4 (20 mM), 98.12% for Eosin Y (10 mg/L), 76.92% for Methylene blue (10 mg/L), and 49.62% for NaCl (20 mM). These findings may provide one of the promising approaches in synthesizing mechanically stable GO-based thin-film composite membranes that are effective for solute separation via nanofiltration.
Highlights
In recent years, graphite-based materials such as graphene, graphene oxide (GO), and reduced graphene oxide have gained significant attention as additives or components in membrane fabrication of water purification membranes [1,2,3,4,5,6,7,8]
The composite polyvinyl alcohol (PVA) membranes were prepared by a multi-step process (Figure 1), The composite membranesofwere prepared by a support multi-step processby(Figure
Thepressure: Cross-Linked PVA Substrate (CPVA) maintained its structure when submerged in water overnight (Figure 2d) as a result of a successful GA cross-linking, which indicates the stability of the membrane
Summary
Graphite-based materials such as graphene, graphene oxide (GO), and reduced graphene oxide (rGO) have gained significant attention as additives or components in membrane fabrication of water purification membranes [1,2,3,4,5,6,7,8]. It is still impractical to prepare a large-area graphene membrane, and it remains challenging to generate high density of nanoporous GO sheets with controllable and relatively uniform GO sheets sizes To address these predicaments, an alternative approach is to use the currently available GO nanosheets by stacking them on a polymeric support to create a selective layer and produce composite water filtration membranes [1,7,24,25]. In this study, a simple approach of creating a stable and highly selective GO layer on a porous electrospun PVA nanofiber as support was first presented via chemical cross-linking with GA.
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