Ion separation with graphene oxide nanofluidic membranes: A review

Ion separation plays a vital role in physiological activities as well as in industrial processes such as desalination, resource utilization and energy conversion. Substantial progress has been made over the last decade in the research of two-dimensional (2D) graphene oxide (GO) membranes with nanofluidic channels, opening up a new horizon for membrane-based ion separation technology. This critical review focuses on the advances in GO nanofluidic membranes from ion transport behaviors to ion separation applications. Firstly, the fabrication strategies of GO membranes are summarized, involving constructions of in-plane and interlayer nanofluidic channels. Then, the mechanisms underlying ion transport behaviors through confined GO nanofluidic channels are disentangled by discussing the fundamental impact factors of internal and external channel microenvironments. In particular, the influences of physical structures (e.g. channel configurations and orientations), chemical features (e.g. functional groups, active sites and charge properties) and environmental stimuli (e.g. driving forces, pH conditions, and competing ions) are highlighted. Finally, the performances and application potentials of GO membranes for ion extraction, ion removal and ion transfer processes are showcased. It is expected to offer new insights into the future prospects of advanced 2D nanofluidic membranes, and pave the way for the development of ionic nanofluids-related science and technology.