Recovery Of Uranium As Uranium Peroxide From Acidic Solution Using Hydrogen Peroxide

摘要

In recent years, three factors are beginning to influence the industry. Firstly, product specifications are becoming more stringent, secondly lower quality ore grades are being processed so that the impurity levels in the leach solutions may rise for which the ADU or MDU is not selective; and thirdly environmental impact of effluents such as ammonia is becomling a subject of societal concern. Consequently the use of hydrogen peroxide to precipitate uranium as 'yellow cake' has received considerable attention. In the present paper, the technical details of using hydrogen peroxide as a precipitant for the preparation of yellow cake from the acidic solution of uranium in presence of appreciable concentration of chloride ion (30-40 gpl), sulphate ion (35-45 gpl), phosphate ion (0.2-1.0 gpl) apart from iron have been discussed. The effects of parameters including pH of the solution, quantity of H_2O_2, digestion time and temperature on uranium peroxide precipitation have been carried out. Conditions for precipitation have been optimised for dilute (2-3 gpl U_3O_8) as well strong (100 gpl U_3O_8) solution of uranium. The end pH for effective precipitation was found to depend on the chloride/ sulphate level in the solution. However, in most of the cases the precipitation reaction was found to be complete in the pH rang of 2.8 to 3.5. Two to four hours of digestion time and slight excess over the stoichiometric quantity of H_2O_2 were found to be suitable for the effective precipitation in terms uranium concentration in barren solution, nature of the precipitate and rate of filtration. Precipitation at temperature of 50-55℃, at the optimum pH of 3.5 improved the particle size (20 micron), which was comparable to the size of the yellow cake produced by magnesia. Tests on 5 L batch capacity yielded higher degree of reproducibility in terms of recovery (>99.9%) and purity (>99%) in the final product (yellow cake).