Effective removal of hexavalent chromium from aqueous solutions using ionic liquid modified graphene oxide sorbent

Abstract

Ionic liquid modified reduced graphene oxide (IL-rGO) was prepared and examined for chromate removal. The sorbent was characterized by N2 adsorption-desorption measurement (BET), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. The sorption behavior of chromate on the ionic liquid modified reduced graphene oxide sorbent from an aqueous medium was studied by varying the parameters such as contact time, initial chromate concentration, pH, and agitation speed. The results showed that sorption kinetics of chromate by IL-rGO follows the pseudo second order, which indicates that the sorption mechanism is both chemical and physical interaction. The sorption isotherm studies revealed that Langmuir model provided the best fit to all the experimental data with an adsorption capacity of 232.55 mg g-1for IL-rGO. Thermodynamic parameters, such as Gibbs free energy (-2.85 kJ mol-1 at 298 K), enthalpy (55.41 kJ mol-1), and entropy (11.64 J mol-1 K-1) of sorption of the chromate on ionic liquid modified reduced graphene oxide was evaluated, and it was found that the reaction was spontaneous and endothermic in nature.