Tuning interlayer spacing of graphene oxide membranes with enhanced desalination performance

A series of aliphatic terminal diamines with different kinetic diameter length, including 1,2-diaminoethane (A2), 1,3-diaminopropane (A3), 1,4-diaminobutane (A4), 1,5-diaminopentane (A5), 1,6-diaminlhexane (A6), 1,7-diaminoheptane (A7), and 1,8-diaminooctane (A8), were selected as built-in molecules of graphene oxide (GO) to fabricate diamine modified graphene oxide nanosheets (Ax-GO). Through vacuum filtration method, diamine modified Ax-GO membranes with tunable interlayer spacing were deposited on the polydopamine (PDA) modified α-Al₂O₃ supports. The separation performances of the Ax-GO membranes were evaluated for seawater desalination by pervaporation. It is found that the water fluxes of the Ax-GO membranes increase with the enhancement of the interlayer spacing of the Ax-GO. Impressively, A4-GO membrane displays the best performance with water flux of 19.7 kg·m⁻²·h⁻¹ and ion rejection of 99.9% at 90 °C for desalination of 3.5 wt% seawater. Further, A4-GO membrane shows high stability for seawater desalination, and the desalination performance keeps unchanged up to 168 h at 75 °C.