Leaching of uranium

Caro s acid has been used ia AustraUa as an oxidant ia the acid-leaching of uranium ores. It acts by oxidising the iron present ia the solution from Fe " to Fe ". This Fe " then oxidizes the uranium. Alternative oxidants that have been used iaclude pyrolusite and chlorate ion. These are both undesirable because their effluents, containing Mn " or CF, contaminate watercourses. 

Leaching of uranium ores with sulfuric acid Gas/liqiiid... 

The bacterial leaching of uranium minerals is complex. This is because of the fact that uranium minerals are not sulfides and are not, therefore, directly attacked by the bacteria. However, the uranium sources usually have a substantial pyrite content which can be bac-terially oxidized to give an acidic ferric sulfate solution which is an effective leaching medium for uranium minerals. The reactions involved in the system can be shown in a simplified form as ... 

It has been seen that one set of leaching systems is that in which the reaction of H+ and OH- species are involved. In case an adequate leaching is not obtained by deploying these situations, the introduction of another anionic species may be required for the formation of new and more appropriate soluble metal species. The leaching of uranium minerals represents one of the fine examples which makes use of this stated provision. 

Carbonated soft drinks (CSDs), estimated maximum oxygen tolerance, 3 38 It Carbonated soft drink bottles, 20 45-46 world market for, 20 53-54 Carbonate leaching, of uranium ores,... 

Canadian demand for sulfur has amounted historically to about 10 percent of U.S. demand. We expect this relationship to continue. As in the U.S., over half of Canadian sulfur use goes into the production of fertilizers. Other major uses for sulfur are for the leaching of uranium ores, and for use in the pulp and paper industry. 

The most significant water-related releases of radium may be from the leaching of uranium mine tailings and from the release of ore-processing effluents generated by leaching, decantation, and... 

Goddard, J. B. and Brosnahan, D. R. "Rate of Consumption of Dissolved Oxygen During Ammonium Carbonate In Situ Leaching of Uranium" Mining Engineering 1982 34 (11), 1589-1596. 

A.R. Burkin and A.J. Monhemius, Acid Leaching of Uranium Ores Using Hydrogen Peroxide and Caro s Acid , Joint CIM Annual Conference and 8th Hydrometallurgy Meeting, Montreal, 1978. 

The modelling that has been applied to date to the situ leaching of uranium has primarily consisted of modelling the hydrologic behavior of the lixiviant as a function of time. A more sophisticated model has combined a chemical model v/ith the hydrologic model to describe the dissolution of uranium and the pore volumes of lixiviant required to leach the orebody (2). 

Shock, D.A. The Vail Conference on in-situ leaching of uranium. In Situ 1, 103-113 (1977). 

Landa ER, Councell TB. 1992. Leaching of uranium from glass and ceramic foodware and decorative items. Health Phys 343-348. 

Eyal Y. and Olander D. R. (1990) Leaching of uranium and thorium from monazite I. Initial leaching. Geochim. 

The uranyl ion forms unusually strong soluble complexes with the carbonate anion > 20), and this has formed the basis for the use of alkaline carbonate solutions in the leaching of uranium, particularly where the ore is leached directly from the ore body (leaching in situ). The rate of dissolution increases with increasing concentration of carbonate but reaches a limiting value at concentrations above about 1 M. It has been shown that this is due to the rate-determining formation of a layer of hydrated UO3 on the surface, which subsequently dissolves by forming complexes with the carbonate ions. 

Leaching of uranium ores can proceed with acid or alkali. 

Laboratory experiments and practical field experience have demonstrated the use of PL in underground leaching of uranium ores. The method has been shown to be effective for all phases of a mining operation, i.e., preparation of a section for exploitation, exploitation itself and subsequent remediation. The main components that need to be determined during preparation for exploitation of a mineral deposit are O2, Fe, Cl and... 

Fig. 2-54. Logging polarograms of natural water at the site of underground leaching of uranium ore 1-3- cathodic polarograms 4- anodic polarogram (reproduced with permission from Putikov, 1993).

Bhurat, M.C., Dwivedy, K.K., Jayaram, K.M.V. and Dar, K.K., 1973. Some results of microbial leaching of uranium ore samples from Narwapahar, Bhatin and Keruadungri, Singhbhum District, Bihar. Nat. Metal. Lab. Tech. J., 15 47—51. 

Bacterial leaching of uranium ores is the subject of a subsequent section of this chapter. Here it suffices to say that the bacterial activity in such situations is that of enhancing the rate of oxidation of sulfides, through which ferric sulfate and sulfuric acid are liberated to speed up the process of solution of uraninite. 

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