Nitrile derivative functionalized graphene oxide membranes for efficient separation of strontium from aqueous waste

Abstract

Graphene oxide (GO) layers were functionalized with nitrile derivatives through acetonitrile vapour exposure and repercussions of N-functionalization on strontium (Sr(II)) adsorption performance of GO membranes were evaluated. Acetonitrile exposure reduces oxygen content of GO, integrates nitrile (CN), amine (–NH2), multiple highly reactive N-moieties on GO yet, preserves intactness of GO lamellar structures. Nitrile derivative functionalization escalates Sr(II) adsorption ability of GO membranes by nearly two fold and an optimal sorption of ∼610 mg/g was obtained at limited GO mass (∼0.1 mg) and Sr(II) concentration of 60–100 µg/mL. N-modified GO membranes displayed confinement of ∼70% percolated Sr2+ ions, considerable Sr(II) adsorption of ∼200 mg/g even after six filtration cycles, limited desorption of 7–24% and competent Sr (II) uptake in presence of Mg2+/Ba2+ ions. Inferences obtained from N-integration and Sr(II) adsorption studies were validated through benzonitrile/nitromethane subjected GO membranes as well, where, adequately amended nitromethane-GO membranes exhibited an enhanced Sr(II) sorption of ∼485 mg/g. Pronounced Sr(II) adsorption performances witnessed for variety of N-GO membranes in the present work re-emphasize the eminence of N-groups in Sr(II) capture, efficacy of N-reagent selection, significance of vapour exposure method and demonstrate the potential of N-modified GO membranes in Sr(II) separation.