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The adsorption of thorium on paddy soil surrounding the tailing reservoir was studied. The effects of solution pH, adsorption time, initial Th(IV) mass concentration and organic acid-inorganic salts on adsorption behavior of thorium was investigated by static adsorption tests. The adsorption kinetics model and isothermal adsorption model were fitted to analyze the adsorption mechanism. The results show that under the conditions of initial Th(IV) mass concentration of 100 mg/E, wastewater pH = 4~5, and adsorption time of 6 h, the adsorption capacity of Th(IV) can reach 1.99 mg/g and the adsorption rate can reach 99.59%. The adsorption process of Th(IV) on paddy soil is physico-chemical adsorption, and the adsorption mechanism is mainly homogeneous monolayer adsorption and heterogeneous multimolecular layer adsorption. [ABSTRACT FROM AUTHOR]

Uranium bioleaching has been rapidly developed in China during recent years. However, some problems during bioleaching, such as low uranium leaching efficiency for rocks lacking pyrite, remain to be solved. A granite type uranium deposit from southern China was selected for the study of U bioleaching with addition of pyrite. Experiments using four approaches, including (i) pyrite ores mixing with culture, (ii) pyrite tiled on the surface of ores with culture, (iii) no pyrite ores with culture, and (iv) pyrite ores without culture were examined in this study. Results showed that bacteria can improve U leaching efficiency, particularly by adding pyrite into ore. Approach (i) pyrite ores mixing with culture had the highest U concentration and the highest recovery rate of the four approaches. No significant difference was observed between approaches (ii) pyrite tiled on the surface of ores with culture and (iii) no pyrite ores with culture.

Uranium is an important strategic resource of the country, which is of great significance to national economy and national defense security. The chemical toxicity and radioactivity of uranium can cause long-term, sustained and irreversible harm to human and environment, the point-to-surface pollution caused by the migration of uranium in the environment and groundwater system has attracted extensive attention. Many scholars have studied the sources of uranium, the forms of uranium in groundwater system, the enrichment and migration of uranium and the treatment of uranium pollution, and used models and related software to evaluate and predict the impact of the migration of radionuclide uranium on human and environment. This paper will provide a more comprehensive theoretical basis for the mechanism of uranium contamination. [ABSTRACT FROM AUTHOR]

Geochemical characterization studies and batch leaching experiments were conducted to explore the effects of a CO2 + O2 leaching system on uranium (U) recovery from ores obtained from an eastern limb of Zinda Pir Anticline ore deposit in Pakistan. The mineralogy of the ore was identified by Electron Probe Micro-analyzer (EPMA) and Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), showing that pitchblende is the main ore mineral. XRD was also used along with EPMA and SEM characterization data. Experimental results indicate that U mobility was readily facilitated in the CO2 + O2 system with Eh 284 mV and pH 6.24, and an 86% recovery rate of U3O8 was obtained. U speciation analysis implied the formation of UO2 (CO3)22− in the pregnant solution. The plausible mechanism may be attributed to the dissolved CO2 gas that forms carbonate/bicarbonate ion releasing oxidized U from the ore mineral. However, U recovery in the liquid phase was shown to decrease by higher U(VI) initial concentration, which may be due to the saturation of Fe adsorption capacity, as suggested by an increase in Fe concentration with increasing initial U(VI) concentration in the solid phase. However, further studies are needed to reveal the influencing mechanism of U(VI) initial concentration on U recovery in the solid phase. This study provides new insights on the feasibility and validity of the site application of U neutral in situ leaching. [ABSTRACT FROM AUTHOR]