Selective and multicycle removal of Cr(VI) by graphene oxide–EDTA composite: Insight into the removal mechanism and ionic interference in binary and ternary associations

Abstract

Graphene-based composite has demonstrated great potential in environmental remediation and wastewater treatment. Herein, graphene oxide was modified with ethylenediaminetetraacetic acid aimed to augment heterogeneous functional groups on the composite i.e., [email protected] for aqueous Cr(VI) adsorption. The characterization materials revealed that EDTA linked with GO through an amide bond, and N, O, and C are present in [email protected] in 3.25, 19.98, and 76.77%, respectively, and the specific surface area of 100.93 m2/g. Tts maximum adsorption capacity of [email protected] towards C(VI) was 36.59 mg/g, at pH 1.8. The classical isotherm and kinetic models were best correlated with the Freundlich isotherm and pseudo-second-order kinetics, respectively. The electrostatic interaction was the predominant force involved Cr(VI) adsorption onto [email protected], followed by the reduction into Cr(VI) and its complexation. The adsorption of Cr(VI) in binary and ternary association with Pb2＋, Cd2＋, and Cl−, seemed unaffected. However, the presence of S2− has a profound effect on Cr(VI) adsorption. More interestingly, the presence of Cl− with S2− in the ternary association (Cr(VI) + Cl− + S2−) suppresses the antagonistic behavior of S2− up to a certain extent that leads to enhance Cr(VI) removal. Overall, the thermodynamics and reusability study advocate the potential of [email protected] for multiple cycle Cr(VI) removal — pave the way for its application in wastewater treatment.