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

We report the fabrication of cross-linked graphene oxide (GO) membranes and their use for dehydration of ethanol by vapor permeation. Two compounds with branched structures, namely, a humic acid-like substance derived from urban waste and a synthetic hyperbranched polyol, were used as cross-linkers. Relatively small amounts of branched cross-linkers are able to stabilize GO membranes as compared with previously reported poly(ethylene glycol) (PEG). Supported cross-linked GO films were prepared by rod coating on polyethersulphone ultrafiltration membranes. The membranes showed a significantly higher permeance for water than for ethanol, and the water selectivity factor was found to increase with temperature in the range 30-60 degrees C, with the branched cross-linkers showing a higher water flux than that of PEG and similar to that of pristine GO, indicating lesser hindrance to water transport. The membranes were also able to dehydrate ethanol-water mixtures, producing retentates that had an ethanol fraction greater than the azeotropic composition.