Doctoral Dissertations

Date of Award

12-1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemical Engineering

Major Professor

Robert M. Counce

Abstract

Multiple experiments have been performed to evaluate aspects of uranium extraction by dibutyl carbitol (DEC) in the system UO2(NO3)2-HNO3-H2O-Ca(NO3)2-DBC. Equilibrium distribution of the uranium solute between the aqueous and organic phases has been evaluated. Transfer rate tests have been performed to determine the effect of physical parameters on the rate of transfer. Evaluation of physical parameter correlations with transfer rate has been used to determine the controlling resistance to transfer: reaction kinetics, diffusion, or a combination of the two. Transfer tests have also been performed in which reactant concentrations have been varied. The results of these tests have been used to establish a reaction rate expression applicable to transfer test conditions. The results of the study indicate that calcium nitrate is effective in increasing the efficiency of uranium extraction by dibutyl carbitol. Results of transfer rate experiments indicate that the rate of transfer is controlled by reaction kinetics, and that the controlling reaction occurs at the interface. Additional transfer rate test results indicate that the rate of transfer is a linear function of the uranium concentration in the aqueous phase, and is not affected by the nitrate concentration under the conditions applied. Based on the results of transfer tests, a psuedo first-order reaction rate expression is proposed as a transient model for extraction in the subject system. Comparison of predicted transfer rates and observed values shows good agreement. A reaction mechanism for the system which is based on one proposed by Danesi (1980) for basic extractants, and which yields a first order rate expression is proposed.

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