Separation of Uranium by Immobilized Inactive Microbial Biomass

Abstract

<p>The ability of microorganisms to interact with and accumulate a variety of heavy metal ions from their immediate environment has been well recognized. Biosorption is termed as the sequestering of metal ions by live or dead microorganisms and their derivatives. Native microorganisms however are not rigid enough to be used as technical biosorbents in large scale operations such as a packed bed adsorption reactor. A new immobilization technique has been developed using a spouted bed reactor that produces encapsulated R. arrhizus biomass which can be used as a technical adsorbent in the same way as an ion exchange resin or activated carbon. The immobilized biomass has 10 to 15 wt % of inert medium that is porous polymeric membrane. The overall mechanical strength of the immobilized biomass was evaluated by measuring the pressure drop at various water now rates in a packed bed filled with immobilized biomass particles. The structure of the encapsulation membrane of the immobilized biomass particles was examined under electron microscope and appeared to be very porous. A batch kinetic mass transfer model was developed for the immobilized R. arrhizus and was numerically solved by collocation methods. Batch kinetic experiments for mass transfer rate of uranium were carried out with the immobilized R. arrhizus using a modified liquid Carberry reactor. The effective diffusivities of uranyl ion through the wall membrane and in the biomass core were estimated by fitting the kinetic data to the mass transfer model using a non-linear regression analysis. The new immobilization technique developed in this study can produce biosorbents with desirable technical properties without affecting the biosorptive capacity of inactive R. arrhizus. This technique is very versatile and can be applied to other biomass types. The mechanical strength of the immobilized biomass and mass transfer rate through the wall membrane can be easily controlled by adjusting the membrane properties during the immobilization process.</p>