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.
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Li et al. (2017) studied this question.
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