IONIC COMPETITION EFFECTS IN A CONTINUOUS URANIUM BIOSORPTIVE RECOVERY PROCESS

Immobilized Rhizopus arrhizus biomass was studied in a continuous sorp tion and desorption mode in order to identify factors that affect the long term uranium biosorptive uptake capacity performance of the immob ilized biomass. Laboratory-scale continuous operation pilot plant expe riments were performed using synthetic uranyl nitrate and industrial u ranium mine leachate solutions. Analysis of the liquid solutions indic ated that the immobilized Rhizopus arrhizus biomass successfully recov ered all of the uranium from the dilute (less than 500 mg U dm(-3)) so lutions. All uranium can subsequently be eluted, yielding highly conce ntrated uranium eluates. The immobilized Rhizopus arrhizus biomass mai ntained its uranium biosorptive uptake capacity over 12 successive sor ption-elution cycles when synthetic uranyl nitrate solutions were used . However, when used with mine leachate solutions, an 18% reduction in the uranium biosorptive uptake capacity occurred within the first fou r adsorption-elution cycles. Spectral analysis indicated that, during continuous use and reuse, the immobilized biomass retained its structu ral integrity. EDAX, scanning and transmission electron microscopic te chniques employed on the microbial biomass suggested that the presence of aluminium interferes with the uranium biosorption process. Spectra l analysis also indicated that the presence of silicon enhances the ne gative effect of the presence of aluminium on the uranium biosorptive uptake capacity of the immobilized Rhizopus arrhizus biomass particles .