Adsorptive removal of uranium from aqueous solution using graphene oxide reinforced and Mg-doped hydroxyapatite composite

Abstract

Removal of uranium contamination in wastewater is related to ecological protection and recycling of uranium. In order to explore a better uranium adsorbent, reduced graphene oxide reinforced and magnesium-doped nano-hydroxyapatite composite microspheres (nHA-Mg@rGO) were synthesized in situ by hydrothermal method, which could be used to adsorb uranium in solution efficiently. Magnesium doping significantly increased U(Ⅵ) adsorption, which reached 1614.93 mg/g at pH = 3.5 and T = 298 K. U(Ⅵ) adsorption could be affected by pH, U(Ⅵ) concentration, adsorbent dosage, reaction time, etc. Experimental data was in accord with pseudo-second-order and Sips models. The changes before and after uranium adsorption by nHA-Mg@rGO microspheres could be found from physicochemical characterization results, indicating that hydroxyl and phosphate groups played a vital role. It was concluded that U(Ⅵ) were adsorbed and fixed through the combined effects of complexation, ion exchange and precipitation. The results are helpful for further exploring application of hydroxyapatite composites in uranium removal.