Photo-enhanced uranium recovery from spent fuel reprocessing wastewater via S-scheme 2D/0D C_(3)N_(5)/Fe_(2)O_(3) heterojunctions

Re-extracting environmentally transportable hexavalent uranium from wastew-ater produced by spent fuel reprocessing using the photocatalytic technology is a crucial strategy to avoid uranium pollution and recover nuclear fuel strategic resources.Here,we have designed S-scheme 2D/0D C_(3)N_(5)/Fe_(2)O_(3)heterojunction photocatalysts based on the built-in electric field and the energy band bend-ing theory,and have further revealed the immobilization process of hexavalent uranium conversion into relatively insoluble tetravalent uranium in terms of thermodynamics and kinetics.According to the results,the hexavalent uranium removal and recovery ratios in wastewater are as high as 93.38%and 83.58%,respectively.Besides,C_(3)N_(5)/Fe_(2)O_(3)heterojunctions also exhibit satisfactory cat-alytic activity and selectivity even in the presence of excessive impurity cations(including Na^(+),K^(+),Ca^(^(2+)),Mg^(2+),Sr^(2+),and Eu^(3+))or various organics(such as xylene,tributylphosphate,pyridine,tannic acid,citric acid,and oxalic acid).It is believed that this work can provide a potential opportunity for S-scheme heterojunction photocatalysts to re-enrich uranium from spent fuel wastewater.

Adsorption behavior of uranium on polyvinyl alcohol-g-amidoxime:Physicochemical properties, kinetic and thermodynamic aspects

Amidoxime-based adsorbents are widely studied as the main adsorbent in the recovery of uranium from seawater. However, the adsorption rate and loading capacity of such adsorbents should be further improved due to the economic viability consider- ation. In this paper, polyvinyl alcohol functionalized with amidoxime （PVA-g-AO） has been prepared as a new adsorbent for uranium （VI） adsorption from aqueous solution. The physicochemical properties of PVA-g-AO were investigated using infra- red spectroscopy （IR）, scanning electron microscope （SEM）, X-ray diffraction （XRD）, and X-ray photoelectron spectroscopy （XPS）. Results showed that the ligand monomers were successfully grafted onto the matrixes. The XRD and XPS analysis showed that uranium was adsorbed in metal ionic form rather than in crystal form. Uranyl （U （VI）） adsorption properties onto PVA-g-AO were evaluated. The adsorption of U （VI） by PVA-g-AO was fast, with an equilibrium time of less than 50 rnin. Additionally the maximum adsorption capacity reached 42.84 mg/g at pH 4.0.

Nuclear Minerals Plants in Brazil—Case Studies

This paper presents the process flow sheet of the main nuclear industrial units in Brazil and discusses some solvent extraction technical support required for these plants. The Center for the Development of Nuclear Technology-CDTN has been investigating alternative ways to supply the nuclear industry in order to improve the industrial processes, Some case study examples are presented, Emulsion from Uranium Solvent Extraction Plant and Itataia Uranium Developments. In Caitité industrial plant the water recirculation has caused continuous changes in the composition of pregnant liquor mainly in the sulfate and chloride concentrations. After some water recirculation cycles, a decrease in the uranium extraction efficiency was noted which was followed by the formation of stable emulsion at the uranium extraction stage. Itataia Uranium Developments were performed in a pilot plant for Itataia ore. This ore has the uranium mineral associated to the phosphate. The process consists of four main steps： 1） phosphate concentration, 2） chemical digestion of the concentrate to produce phosphoric acid with dissolved uranium, 3） uranium recovery, and 4） phosphoric acid purification by solvent extraction.