Ionic Competition Effects in a Continuous Uranium Biosorptive Recovery Process

Abstract

: Immobilized Rhizopus arrhizus biomass was studied in a continuous sorption and desorption mode in order to identify factors that a †ect the long term uranium biosorptive uptake capacity performance of the immobilized biomass. Laboratory-scale continuous operation pilot plant experiments were performed using synthetic uranyl nitrate and industrial uranium mine leachate solutions. Analysis of the liquid solutions indicated that the immobilized Rhizopus arrhizus biomass successfully recovered all of the uranium from the dilute (less than 500 mg U dm~3) solutions. All uranium can subsequently be eluted, yielding highly concentrated uranium eluates. The immobilized Rhizopus arrhizus biomass maintained its uranium biosorptive uptake capacity over 12 successive sorptionÈelution 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 Ðrst four adsorptionÈ elution cycles. Spectral analysis indicated that, during continuous use and reuse, the immobilized biomass retained its structural integrity. EDAX, scanning and transmission electron microscopic techniques employed on the microbial biomass suggested that the presence of aluminium interferes with the uranium biosorption process. Spectral analysis also indicated that the presence of silicon enhances the negative e †ect of the presence of aluminium on the uranium biosorptive uptake capacity of the immobilized Rhizopus arrhizus biomass particles.