Kinetic models for uranium recovery from sulfuric acid leach streams by strong-base anion resins

Abstract

Ion exchange resins are used commercially to concentrate and purify uranium from sulfuric acid leach streams. Three important resin parameters are capacity, loading, and elution kinetics. When a plant engineer evaluates resin kinetic performance, he generally relies on batch loading and elution expert ments with changing bulk concentration. These experiments are easy to set up and maintain and are useful for relative comparison of resins. However, the loading driving force is not constant. Mathematical models for this condition are not readily available. Thus, the resin's diffusion coefficients remain undetermined. A shell progressive batch loading model with changing bulk concentration and a shell progressive elution model with zero bulk concentration were analytically derived. Loading data which could not be fit by constant concentration literature models were readily fit by the shell progressive changing bulk concentration model. The loading diffusion coefficients agree with those calculated from data by Streat and Takel. The elution diffusion coefficients were much smaller than the loading diffusion coefficients. The small elution diffusion coefficients can be accounted for by dynamic equilibrium within the ion exchange resin, i.e., a low concentration of free urany1 sulfate ion in the resin.