Comparison of Chemical Cross-Linkers with Branched and Linear Molecular Structures for Stabilization of Graphene Oxide Membranes and Their Performance in Ethanol Dehydration

Removal of endocrine disruptors and pharmaceuticals by graphene oxide-based membranes in water: A review

Membrane-based water treatment has emerged as a promising solution to address global water challenges. Graphene oxide (GO) has been successfully employed in membrane filtration processes owing to its reversible properties, large-scale production potential, layer-to-layer stacking, great oxygen-based functional groups, and unique physicochemical characteristics, including the creation of nano-channels. This review evaluates the separation performance of various GO-based membranes, manufactured by coating or interfacial polymerization with different support layers such as polymer, metal, and ceramic, for endocrine-disrupting compounds (EDCs) and pharmaceutically active compounds (PhACs). In most studies, the addition of GO significantly improved the removal efficiency, flux, porosity, hydrophilicity, stability, mechanical strength, and antifouling performance compared to pristine membranes. The key mechanisms involved in contaminant removal included size exclusion, electrostatic exclusion, and adsorption. These mechanisms could be ascribed to the physicochemical properties of compounds, such as molecular size and shape, hydrophilicity, and charge state. Therefore, understanding the removal mechanisms based on compound characteristics and appropriately adjusting the operational conditions are crucial keys to membrane separation. Future research directions should explore the characteristics of the combination of GO derivatives with various support layers, by tailoring diverse operating conditions and compounds for effective removal of EDCs and PhACs. This is expected to accelerate the development of surface modification strategies for enhanced contaminant removal.

Effect of Temperature and Branched Crosslinkers on Supported Graphene Oxide Pervaporation Membranes for Ethanol Dehydration

We describe the performance of graphene oxide (GO) membranes stabilized by crosslinkers and supported on polyethersulfone films in the dehydration of ethanol in a continuous cross-flow pervaporation set-up. We used two crosslinker species with branched structures (humic acid-like substances derived from urban waste and a synthetic hyperbranched polyol). The supported crosslinked GO films were prepared by rod coating on a polyethersulfone ultrafiltration membrane. Pervaporation experiments were carried out at temperatures of 40, 50, 60 and 70 °C. When the feed comprised pure water and ethanol, a much higher flux of water than ethanol was observed at all temperatures through GO films stabilized by the two crosslinkers (humic acid, GO-HAL, and the synthetic hyperbranched polyol, GO-HBPO), indicating the separation ability of these crosslinked membranes. For feed mixtures of water and ethanol, the GO-HAL and GO-HBPO membranes showed good separation performances by producing permeates with a significantly higher water content than the feed at all temperatures.