Intelligent graphene oxide membranes with pH tunable channels for water treatment

Abstract

• The pH tunable two dimensional graphene oxide channels were achieved. • The nano-gating ratios of smart graphene oxide membranes reach ∼ 5. • The smart graphene oxide membranes can reject different sized species. • The smart graphene oxide membranes exhibit promising acid (or alkaline) recovery performance. Adaptive membranes that can intelligently control their permeability or selectivity depending on the surrounding environments are of extraordinary importance in the separation technology area. Herein, we report the pH responsive membranes through covalently grafting weak Polyelectrolytes (poly(acrylic acid) (PAA) or poly(4-vinylpyridine) (P4VP)) onto the regular two dimensional (2D) channels stacked by Graphene oxide (GO) nanosheets. Attributed to the reversible shrinking/stretching function of PAA (or P4VP) chains with the variation of external pH, the switchable 2D GO channels are thus established successfully. Correspondingly, the resulting PAA@GO and P4VP@GO 2D membranes show promising nano-gating ratios of ∼ 5 accompanied by satisfactory water permeances. Furthermore, the pH responsive 2D channels render these two types of membranes with the adaptive ability of rejecting different sized species according to separation requirements. For disposing industrial alkaline (or acid) effluents, PAA@GO (or P4VP@GO) membranes exhibit outstanding alkaline (or acid) recovery performance as well.