Regulating the Interlayer Spacing of Graphene Oxide Membranes and Enhancing their Stability by Use of PACl

Graphene oxide (GO) is an ideal membrane material for water treatment due to its outstanding physicochemical properties and unique lamellar structure. However, the separation performance and practical application of GO membranes are mainly affected by the interlayer spacing and stability in aqueous solutions. Here, we report a novel and facile approach to fabricating GO membranes with adjustable interlayer spacing and high stability in aqueous solutions through cross-linking with polyaluminum chloride (PACl). With this approach, the lamellar spacing can be adjusted by changing the OH/Al ratios (B values) of the PACl, and the GO nanosheets can be tightly bonded by the strong electrostatic effect that PACl provides between them. The average interlayer spacing of the GO layer could be varied approximately in the range of 0.80-1.09 nm. The PACl-GO membranes demonstrated excellent stability in water and inorganic/organic solutions when the concentration of PACl was 0.1, 1, and 10 mM, remaining unchanged for at least 2 weeks. Moreover, the PACl-GO membranes featured exceptional sieving capabilities for model and natural organic substrates, while it was also observed that increasing the interlayer spacing of the PACl-GO membranes increased both the membrane flux and the separation performance of organic matter.