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This study evaluated the effectiveness of ore particle size on column bioleaching from low-grade uranium ore using an indigenous Acidithiobacillus ferrooxidans, isolated from local uranium ore. The uranium content was 0.033% by weight and ore particle size was crushed to <50 mm, <30 mm, and <15 mm. The additive content of sulfuric acid 5 g/L, Fe 3+ dosage of 5.0 g/L, spray strength of 2.57 L/(h·m 2 ) and temperature of 25 °C were controlled. After 150 days of leaching, acid consumption amounted to 2.73 g H 2 SO 4 per kg ore, the obtained maximum uranium extraction was 64.85% with the ore particle size of <15 mm. The results showed that a smaller particle size ore had a higher uranium extraction and that an economic uranium extraction can be obtained by correctly controlling the ore granularity., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A mesophilic acidophilic consortium was enriched from acid mine drainage samples collected from several uranium mines in China. The performance of the consortium in column bioleaching of low-grade uranium embedded in granite porphyry was investigated. The influences of several chemical parameters on uranium extraction in column reactor were also investigated. A uranium recovery of 96.82% was achieved in 97 days column leaching process including 33 days acid pre-leaching stage and 64 days bioleaching stage. It was reflected that indirect leaching mechanism took precedence over direct. Furthermore, the bacterial community structure was analyzed by using Amplified Ribosomal DNA Restriction Analysis. The results showed that microorganisms on the residual surface were more diverse than that in the solution. Acidithiobacillus ferrooxidans was the dominant species in the solution and Leptospirillum ferriphilum on the residual surface., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

With the gradual depletion of high-grade uranium resources in southern China, it is necessary to recover uranium from low-grade complex and refractory uranium resources However, the traditional acid mining process has certain drawbacks such as high acid consumption, low uranium recovery, and potential environmental pollution. There is an urgent need to develop new technologies for the extraction of refractory uranium ores. A tonne-scale column bioleaching for low-grade refractory vocanogenic uranium ore containing brannerite and pitchblende was performed. The uranium leaching efficiency reached 85.86% with an acid consumption of only 10.15% after leaching for 130 d. In the bioleaching stage, the Fe3+ concentration had a good correlation with the Eh value; the higher the Fe3+ concentration, the better was the leaching of uranium. The solution pH was kept below 2.5 during the leaching process, which avoided the precipitation of iron and ensured a higher Fe3+ concentration in the solution. Efficient leaching of uranium from UTi2O6 and UO2 was achieved through oxidation of Fe3+ and the action of microorganisms. The results may provide technical support for industrial leaching of low-grade volcanogenic uranium deposits. [ABSTRACT FROM AUTHOR]

Uranium was immobilized with hydroxyapatite and the dissolution stability of the immobilization product was investigated. The immobilization efficiency and capacity of U were respectively almost 100% and 105 mg/g at the optimal conditions that were experimentally determined. Meta-autunite was found in the mineral phases of the immobilization product, and its dissolved concentration of U was below 0.1 mg/L pH of 5–7 and only 34 μg/L from the toxicity characteristic leaching procedure (TCLP) test. A thermodynamic model of dissolution was established to reveal the mechanism of high dissolution stability of the immobilization product. [ABSTRACT FROM AUTHOR]

Citric acid and oxalic acid, the main metabolites of fungi, have different leaching effects on uranium ore. Herein, uranium leaching from a volcano-litho-type uranium ore using citric acid and oxalic acid was studied by performing soaking experiments in incubator shakers using pure water and H2SO4 as controls. The citric acid is advantageous over oxalic acid in terms of the uranium leaching rate (97% and 67%) and speed for 20 days of leaching. These findings will help optimize the isolation and cultivation conditions of organic acid-producing fungi used for uranium leaching. [ABSTRACT FROM AUTHOR]

The high level of fluorine and low sulfur in the ore could significantly undermine the bioleaching effectiveness. Here, a strategy to improve the bioleaching efficiency by introducing fluoride-resistant mesophilic eosinophils coupled with pyrite supplement was investigated in a bioleaching system with such ore. The results of column and heap bioleaching showed that 89.25% and 90.40% of uranium were recovered with the consortium and pyrite addition, which increased the uranium leaching rates by 13.22% and 8.96% as compared with the sulfuric acid leaching. Hence, it provides a method to improve uranium bioleaching efficiency of the high-fluorine and low-sulfur uranium ore by the consortium adding pyrite. [ABSTRACT FROM AUTHOR]

Systematic study of the surface chemical properties of uranium minerals is necessary to improve the uranium ore extracting process. The presented work aims to argue geochemistry and acid hydrometallurgy accessibility of uraninite from the Mianhuakeng (MHK) granite-hosted uranium deposit, South China, which provides insight on this ore extracting domain. Mineralogy, geochemical composition, U–Th–Pb chemical age, and uranium deportment of the uraninite were systematically analyzed by using scanning electron microscope with energy dispersion spectrum (SEM-EDS), an electron probe microanalyzer (EPMA), and x-ray photoelectron spectroscopy (XPS). The results showed that uraninite was intergrowth with coffinite, probably due to uraninite being partly metasomatized into coffinite along the fissures. The major element content of uraninite such as for UO2, SiO2, and CaO were 79.46 ± 2.03 wt%, 6.19 ± 1.36 wt%, and 5.09 ± 0.80 wt%, respectively. Single-point U–Th–Pb chemical ages for uraninite grains were calculated with the EPMA data, and the results showed ages ranging from a few million to dozens of million years, indicating Pb loss after uraninite formed. Uranium deportment in uraninite generally existed in the forms of UO2, U3O8, and UO3, and mostly showed high valence states suggested by XPS. Uranium on the surface of the uraninite grain was partially oxidized by sulfuric acid leaching, which led to tetravalent uranium converting to hexavalent uranium, suggesting uraninite in the MHK uranium deposit is accessible to be leached by sulfuric acid. [ABSTRACT FROM AUTHOR]