Modification of GO-based pervaporation membranes to improve stability in oscillating temperature operation

Graphene oxide (GO)-based pervaporation membranes have great potential for desalination and lithium containing brine enrichment. However, they experienced critical challenges when used in aqueous solution and exposed to oscillating temperatures due to swelling and microdefects. In this work, the GO-based membranes were fabricated by the filtration of GO suspension with sulfonate-containing diamine molecules on porous substrates, then dip-coated with chitosan and polyvinyl alcohol (PVA). The resultant GO-based membranes demonstrated 99.99% salt rejection during pervaporation using NaCl or lithium-containing concentrated inland brine with humic acid as the feed solution under oscillating temperature. The intercalation of diamine molecules inside the GO nanochannels was able to increase water flux by 20% while the coated chitosan/PVA layer reduced structural defects and undesired scaling/fouling on the membrane surface resulting in minimal reduction of water flux (16%) over 72 h of oscillating temperature pervaporation. Moreover, the membrane exhibited good stability after chemical cleaning. The proposed GO-based membranes provided significant performance sustainability in concentrated inland brine and oscillating feed temperature condition.