Enhanced Photocatalytic Removal of Uranium(VI) from Aqueous Solution by Magnetic TiO₂/Fe₃O₄ and Its Graphene Composite

Abstract

The separation and recovery of uranium from radioactive wastewater is important from the standpoints of environmental protection and uranium reuse. In the present work, magnetically collectable TiO₂/Fe₃O₄ and its graphene composites were fabricated and utilized for the photocatalytical removal of U(VI) from aqueous solutions. It was found that, under ultraviolet (UV) irradiation, the photoreactivity of TiO₂/Fe₃O₄ for the reduction of U(VI) was 19.3 times higher than that of pure TiO₂, which is strongly correlated with the Fe⁰ and additional Fe(II) generated from the reduction of Fe₃O₄ by TiO₂ photoelectrons. The effects of initial uranium concentration, solution pH, ionic strength, the composition of wastewater, and organic pollutants on the U(VI) removal by TiO₂/Fe₃O₄ were systematically investigated. The results demonstrated its excellent performance in the cleanup of uranium contamination. As graphene can efficiently attract the TiO₂ photoelectrons and thus decrease their transfer to Fe₃O₄, the photodissolution of Fe₃O₄ in the TiO₂/graphene/Fe₃O₄ composite can be largely alleviated compared to that of the TiO₂/Fe₃O₄, rendering this ternary composite a much higher stability. In addition, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES), and X-ray photoelectron spectroscopy (XPS) were used to explore the reaction mechanisms.