KINETICS OF THE DISSOLUTION OF URANIUM DIOXIDE IN CARBONATE-BICARBONATE SOLUTIONS
The kinetics of the dissolution of uranium dioxide in sodium carbonate- sodium bicarbonate solutions were determined. The study was undertaken in order to obtain fundamental information about the commercial carbonate process for leaching uranium from its ores. A rate equation incorporating the effects of surface area oxygen partial pressure, temperature, and reagent concentrations was empirically developed. A mechanism consisting essentially of two consecutive reactions at steady state is proposed. These reactions are the oxidation of U/ sup 4+/ to U/sup 6+/ and the subsequent formation of the uranyl dicarbonate complexion. Depending on the conditions, either or both of these reactions can determine the over-all rate. The conversion of uranyl dicarbonate to the uranyl tricarbonate complexion is postulated to be very rapid. In the suggested mechanism, the rate-determining phase of the oxidation is the dissociation of adsorbed molecular oxygen. and both the carbonate and bicarbonate ions play equivalent roles in the formation of the uranyl dicarbonate. As indicated by their high activation energies of about 13 and 14 kcal per mole uranium, both reactions are chemical rather than diffusional processes. A mathematical examination of the proposed mechanism produced a rate equation consistent with the experimental information. The credibility of the mechanism was thereby strengthened. (auth)
- Research Organization:
- National Lead Co., Inc. Raw Materials Development Lab., Winchester, Mass.
- DOE Contract Number:
- AT(49-6)-924
- NSA Number:
- NSA-12-007763
- OSTI ID:
- 4352525
- Report Number(s):
- WIN-89
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-58
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ADSORPTION
CARBONATES
CHEMICAL REACTIONS
COMPLEXES
CONCENTRATION
DECOMPOSITION
ENERGY
EQUATIONS
EXCITATION
IONS
LEACHING
MATHEMATICS
OXIDATION
OXYGEN
PRESSURE
QUANTITATIVE ANALYSIS
QUANTITY RATIO
REACTION KINETICS
SODIUM CARBONATES
SOLUTIONS
SURFACE AREA
SURFACES
TEMPERATURE
TESTING
URANIUM COMPOUNDS
URANIUM DIOXIDE
URANIUM ORES
URANYL COMPOUNDS
VELOCITY