Synergistically performing graphene oxide-crown ether composite membrane structures for efficient strontium separation from aqueous solutions

Abstract

Graphene oxide (GO)-crown ether (CE) composite preparation was carried out using diverse CE/GO configurations where, composite/structural suitability and adsorption characteristics of these composites were evaluated to derive optimal strontium (Sr(II)) separation conditions. Initial characterization and Sr(II) sorption studies evidenced the eminence of GO-18-crown-6-ether (GO-18C6) composites among those explored and, a comprehensive investigation on compositing procedure, ambience, affecting parameters was undertaken to deduce relevant interaction mechanism. 18C6 molecules interact with GO layers via CH-π, hydrogen bond, dipole-dipole and covalent interactions, reduce graphitic content, deteriorate structural order and induce aggregate formation. Sr(II) sorption at composite membranes is determined by GO/18C6 composition and structure, composite mass, Sr(II) concentration and pH of the ambience. Composite membranes prepared at optimal interaction conditions exhibited maximum Sr(II) adsorption capacity of ∼890 mg/g, attributed to development of profusive Sr(II) reactive sites and effective amendment of permeation channels. Inferences on optimal Sr(II) adsorption at composite membranes were validated further via sorption studies on extended and N-functionalized GO/CE structures. The rapid, economic and competent Sr(II) adsorption demonstrated in the present work evidence synergetic performance of GO-CE in composite, re-emphasize the potential of membranes in Sr(II) separation and finds significance in removal of alkali/alkaline earth metal ions from aqueous waste solutions.