Abstract
Two different types of 2D nanosheets, including hydrophobic graphene (GR) and hydrophilic graphene oxide (GO), were filled into poly (vinyl alcohol) (PVA) polymers to prepare mixed matrix membranes (MMMs) for ethanol dehydration via pervaporation. The relationship between the physical/chemical properties of graphene and pervaporation performance of MMMs was investigated by a comparison of GR/PVA and GO/PVA MMMs in microstructure and PV performance. The incorporation of GO nanosheets into PVA reduced PVA crystallinity and enhanced the membrane hydrophilicity, while the incorporation of GR into PVA led to the opposite results. The incorporation of GR/GO into PVA depressed the PVA membrane swelling degree, and the incorporation of GR showed a more obvious depression effect. GR/PVA MMMs showed a much higher separation factor than GO/PVA MMMs, while they exhibited a much lower permeation flux than GO/PVA MMMs and pristine PVA membranes. The huge difference in microstructure and performance between GO/PVA and GR/PVA MMMs was strongly associated with the oxygen-containing groups on graphene lamellae. The higher permeation flux of GO/PVA MMMs was ascribed to the facilitated transport of water molecules induced by oxygen-containing groups and exclusive channels provided by GO lamellae, while the much lower permeation flux and higher separation factor GR/PVA MMMs was resulted from the smaller GR interplanar spacing (0.33 nm) and hydrophobicity as well as barrier effect of GR lamellae on the sorption and diffusion of water molecules. It was presumed that graphene intercalated with an appropriate number of oxygen-containing groups might be a good choice to prepare PVA-based MMMs for ethanol dehydration, which would combine the advantages of GR’s high interlayer diffusion selectivity and GO’s high permeation properties. The investigation might open a door to achieve both of high permeation flux and separation factor of PVA-based MMMs by tuning the microstructure of graphene.
Highlights
Ethanol dehydration via pervaporation (PV) has attracted increasing attention due to the rapid development and application of ethanol biofuel [1,2,3]
The relationship between the physical/chemical properties of graphene and pervaporation performance of matrix membranes (MMMs) was investigated by comparison of GR/PVA and graphene oxide (GO)/PVA MMMs in microstructure and PV performance
GO was well exfoliated by PVA and homogeneously dispersed in the PVA matrix, benefiting from the good solubility of GO, and a strong interaction existed between the GO nanosheet and PVA polymer due to oxygen-containing groups
Summary
Ethanol dehydration via pervaporation (PV) has attracted increasing attention due to the rapid development and application of ethanol biofuel [1,2,3]. When dealing with the ethanol dehydration, hydrophilic polymers are the most commonly used membrane materials [4,5,6,7,8,9,10,11,12,13,14,15,16,17], and the PVA membrane is the only one to realize industrial application due to its high hydrophilicity, good solubility in water, excellent film-forming property, biodegradability, and eco-friendly properties [18]. The PV performance of pristine PVA membranes showed a trade-off effect between permeability and selectivity. One. Separations 2022, 9, x FOR PEER REVIEW of the most effective methods for improving the PV performance of PVA membranes is the incorporation of inorganic fillers into polymers to fabricate mixed matrix membranes (MprMistMines)P[V1A9–m24e]m.
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