Facile preparation of NiCo2O4@rGO composites for the removal of uranium ions from aqueous solutions

Abstract

A hierarchical structure of NiCo₂O₄@rGO composite has been fabricated, with its structure and morphology well characterized by XRD, TEM, XPS and BET. The results proved that the NiCo₂O₄ nanosheets grow uniformly on both sides of the graphene sheets. In batch adsorption experiments, the effects of equilibrium time, pH and temperature on uranium(VI) adsorption were investigated. The main results show that the NiCo₂O₄@rGO composite has a higher affinity towards the uptake of uranium(VI) from aqueous solutions. The highest adsorption capacity reached 342.4 mg U g⁻¹ at pH 5.0. Kinetic analysis shows that the adsorption process is described best by a pseudo-second-order kinetic model. The uranium(VI) sorption equilibrium data correlates well with the Langmuir sorption isotherm model in the thermodynamic analysis. Thus, NiCo₂O₄@rGO composite is an excellent adsorbent for removing uranium(VI) ions.