The stability of graphene oxide (GO) nanofiltration (NF) membrane in aqueous environment: Progress and challenges
Recently, advanced membranes based on 2D material of graphene oxide (GO) for NF have drawn great attentions due to their striking, dramatic separation performances which are much higher than traditional membranes. However, stability, which is a precondition for practical applications, has become the bottleneck of the GO membranes for water treatment. Fortunately, the stability of GO membranes in water has received significant attentions, and many fruitful efforts have been devoted to solve this problem most recently. It is therefore critical to update the broader scientific community on the important advances in this interdisciplinary field. Herein, we review recent progress in improving the stability of GO membranes in water. Fundamental issues, including the origin of the instability of GO membranes in water, and influences of the chemical and physical properties of GO itself on the stability of the resultant membranes have been discussed. We also explore the diverse structural design and surface/interface engineering strategies for improving the stability of GO membranes in water, including the introduction of hydrogen bonding or intermolecular interaction via insertion of polyelectrolytes, cross-linking by molecules or ions, or blending of graphene-based materials, as well as improving the interaction between GO selective layers and substrates. The existing challenges and a forward-looking perspective are also discussed, suggesting directions to design GO and other 2D material-based membranes with outstanding stability and high separation performance for practical applications.