The adsorption of U(VI) on magnetite, ferrihydrite and goethite

Abstract During the long-term disposal of radioactive waste, ferrous waste containers and building materials are tending to corrode to produce a large number of iron oxides. The formed iron oxides would bring significant effects on the diffusion and migration of radionuclides through adsorption and reduction. This study aimed to evaluate the interaction of U(VI) on iron oxides under anaerobic conditions, where goethite, magnetite, and ferrihydrite were used as adsorbents. The results showed that the adsorption of U(VI) on iron oxides was chemical adsorption, and the adsorption capacity of U(VI) on ferrihydrite was much higher than that on goethite and magnetite. Humic acid (HA) promoted the adsorption of U(VI) on iron oxides under acidic conditions, while U(VI) adsorption was inhibited by HA in the neutral to alkaline conditions. The adsorption of U(VI) on iron oxides was an endothermic process, and higher temperature was beneficial for the adsorption. Surface complexation modelling (SCM) fitting revealed that monodentate inner complexes of ≡ FeOUO 2 + and ≡ FeOUO 2 ( OH ) 0 were mainly formed on the surface of iron oxides. Finally, the reduction of U(VI) to U(IV) on magnetite under anaerobic condition was confirmed by X-ray photoelectron spectroscopy (XPS) and Mossbauer spectroscopy.