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 TiO 2 /Fe 3 O 4 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 TiO 2 /Fe 3 O 4 for the reduction of U(VI) was 19.3 times higher than that of pure TiO 2 , which is strongly correlated with the Fe 0 and additional Fe(II) generated from the reduction of Fe 3 O 4 by TiO 2 photoelectrons. The effects of initial uranium concentration, solution pH, ionic strength, the composition of wastewater, and organic pollutants on the U(VI) removal by TiO 2 /Fe 3 O 4 were systematically investigated. The results demonstrated its excellent performance in the cleanup of uranium contamination. As graphene can efficiently attract the TiO 2 photoelectrons and thus decrease their transfer to Fe 3 O 4 , the photodissolution of Fe 3 O 4 in the TiO 2 /graphene/Fe 3 O 4 composite can be largely alleviated compared to that of the TiO 2 /Fe 3 O 4 , 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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A new 3-fold interpenetrated uranyl organic framework, UO2(bdc)(dmpi), was hydrothermally synthesized using 1,4-benzenedicarboxylic acid (H2bdc) and 1-(4-(1H-imidazol-1-yl)-2,5-dimethylphenyl)-1H-imidazole (dmpi). This framework, which was determined by synchrotron radiation X-ray, exhibited a new 3-fold interpenetrated (2,4)-connected topology with the Schläfli symbol of (12(6))(12)2. Additionally, large incurvation happened to the bond angle of [O=U=O](2+), which was always arranged in a rigorous line. Computational results based on density functional theory (DFT) indicated that the bent geometry of uranyl in UO2(bdc)(dmpi) was mainly due to the higher charge populations in the valence 6d shells of uranium, rendered by the electronegative imidazoles.