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Ultra-thin graphene oxide films via contra-diffusion method: Fast fabrication for ion rejection

Du, Yong, Zhang, Xi, Yang, Jing, Lv, Yan, Zhang, Chao, Xu, Zhi-Kang
Journal of membrane science 2019
artificial membranes, calcium, cations, crosslinking, electrostatic interactions, filtrates, graphene, graphene oxide, iron, magnesium, nanofiltration, potassium, sodium, sodium sulfate
Membranes based on graphene or graphene oxide (GO) have received intensive studies recently for various separation processes. However, a great challenge lies in fast and facile fabrication of GO membranes with high salt rejection. Here we report for the first time that ultra-thin GO films with a good salt rejection can be fabricated via contra-diffusion-induced crosslinking based on cation-π and electrostatic interactions between cations and GO flakes. It only takes down to 5 min to construct a defect-free GO film. Various cations, including Na+, K+, Mg2+, Ca2+ and Fe3+, can be used as “crosslinkers” to endow the as-prepared GO membranes with highly tunable separation performance. The optimized GO membranes exhibit over 90% rejection of Na2SO4 with filtrate permeance of 4.3 L m−2 h−1 bar−1 during the nanofiltration process, which reaches to the performance upper limit of previously reported graphene-based membranes. Such a high performance should be attributed to the unique packing structures of the GO flakes crosslinked by cations and the thin and uniform GO selective layers.