A CO2-responsive graphene oxide/polymer composite nanofiltration membrane for water purification

Abstract

A “smart” graphene oxide (GO) based nanofiltration membrane was prepared through electrostatic and π–π interaction-driven complexation with poly(N,N-diethylaminoethyl methacrylate) bearing a pyrene end group (Py-PDEAEMA). The composite membranes show a number of attributes potentially appealing for water treatment. First, they display reversible, gas-tunable water permeability between the pore closure state under CO₂ stimulation and the pore opening state upon Ar bubbling. The water permeability remains much higher than that of a pure GO membrane even at the pore closure state. Secondly, the separation of organic dye molecules from water using this membrane is similarly efficient as that using a pure GO membrane despite the much higher water permeability. Finally, as a result of CO₂-induced reversal of the charge sign, the composite membrane shows an excellent trade-off between rejection of some salts like MgCl₂ and water permeability, with both much higher rejection and permeability compared to a pure GO membrane. This study of a CO₂-responsive, GO-based nanofiltration membrane, the first of its kind, demonstrates new perspectives in developing smart separation membranes for water purification.