▎ 摘　　要

Graphene oxide (GO) membranes are an ideal candidate for ethanol (EtOH) dehydration. EtOH rejection is typically obtained by controlling the GO's structural order, sometimes in combination with large concentrations of ions, but the mechanisms responsible for EtOH rejection are poorly understood. Here we show that GO membranes drop-cast from suspensions containing a small concentration of ions are impermeable to EtOH vapor. Backed by in situ experimental evidence, acid-base titrations and calculations based on percolation theory matching the results obtained at different ionic concentrations, we propose that the ions prevent hydrogen-bonding-driven intercalation by screening the GO's oxygen-containing groups, a more effective mechanism than the one previously based on in silico simulations.