Development of graphene oxide-based membrane as a pretreatment for thermal seawater desalination

Scaling constitutes a major concern in seawater desalination. In thermal desalination, scaling is limiting the top brine temperature (TBT). Brine temperature limitation depends on the concentration of divalent ions. This paper reports the synthesis of graphene oxide (GO)/polyacrylamide (PAM)/polyethersulfone (PES) membrane, in which GO layer is deposited on the surface of PES substrate using PAM as an adhesive layer, to be used as a pretreatment step to filter the divalent ions in thermal seawater desalination application. GO/PAM-PES membrane is prepared via spin coating technique, then reduced to rGO/PAM-PES by subjecting the membrane to hydrogen iodide (HI). PAM is used as an adhesive layer onto PES membrane (an ultrafiltration membrane) to improve rGO layer attachment onto its surface. The results indicate that increasing pressure increases both the rejection and the permeate flux. Using seawater, rGO/PAM-PES yields a higher rejection for Mg²⁺ and Ca²⁺ ions compared with commercial nanofiltration membrane (NF270). The pretreatment step allows the increase in TBT to 148 °C using NF, 160 °C using NF-GO and 166 °C using rGO membranes.