Author(s):
Aditi C. Patra, V. K. Thakur, P. Lenka, C. G. Sumesh, S. K. Jha

Abstract:
Dynamic leaching tests were carried out on solid wastes generated from the uranium mining and milling industry under different physico-chemical conditions to assess the mobility of uranium from these matrices. The mobile/ soluble fraction of uranium leached out very slowly; being faster in the initial stages and then attaining a near steady state condition in most cases. Uranium leaching was observed to increase with decreasing initial pH, reducing particle size and increasing temperatures. A maximum of 2.4% uranium was leached out under highly acidic conditions in the experimental time period. Leachability index values indicated weak leaching of uranium from the wastes under all conditions. Leaching kinetics was examined with the help of a heterogeneous reaction model. Model results and apparent activation energy values indicated the leaching process to be initially reaction controlled and subsequently diffusion controlled. The apparent rate constants displayed dependence on the particle sizes of the tailings. All results obtained from this study imply that the extent of uranium leaching from these solid mining wastes is extremely low. This indicates low mobility and negligible transfer to other environmental compartments.

Pages: 66-81

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