Interaction mechanism between ion and graphene oxide based membrane in brine for robust anti-swelling properties

Two-dimensional graphene oxide (GO) based membranes have gained great attention in recent decades. However, the poor anti-swelling property greatly hinders its practical application in brine due to the swelling-induced weak nanoconfinement and the complicated interaction between membrane and salt ions. In this work, Al3 + and Sc3+ cross-linked membranes were successfully fabricated, and the impacts of metal ions in real salt lake brine on the stability and separation performances of the Al/GO/PES and Sc/GO/PES membranes were investigated in detail. Results showed that monovalent ion played an important role in reducing the interlayer spacing, but the interlayer spacing can not be effectively maintained. Divalent ions illustrated strong ability to stabilize the interlayer spacing, no matter how low the concentration especially Mg2+, exhibiting strong interaction with GO nanosheets. Furthermore, Sc3+ exhibited superior interaction with GO nanosheets with only 1.8 angstrom interlayer spacing changes from dry to wet state, owing to the strong covalent interaction and cation-It effects. After immersion in West Taijinar brine with high concentration of Mg2+, the stability can be enhanced significantly with only 0.30 angstrom changes lower than the Sc/GO/PES membrane without immersion in brine. Most importantly, the resultant membrane exhibited dramatic separation performances with the permeate flux of 900 L center dot m-2 center dot h-1, and robust stability in DI water. These findings suggest a potential construction strategy to break the practical application of GO-based membrane in brine.