Insight into the Uranium biosorption from aqueous solution by biomass immobilization

Uranium is one of the most threatening elements due to its radioactivity and high toxicity. In the course of the nuclear fuel cycle, significant amounts of uranium are released into the environment. Biosorption technology offers the advantages of low operating costs and high efficiency in metal removal from aqueous solutions. In this work, the sorptions of uranyl ions from aqueous solutions by Saccharomyces Cerevisiae (SC) on zeolite clinoptilolite were investigated. First, a characterization of the natural zeolite was performed by classical chemical analysis and, then the influence of solution pH, temperature, contact time and, initial concentration on the sorption of uranyl was investigated. The concentration range of uranyl in the solution was between 0.02 and 1 mmol L-1, which was determined by the inductively coupled plasma optical emission spectrometry method (ICP-OES). Further results showed that metal binding occurred extracellularly at the cell wall surface and the rate of sorption of uranyl ions by free yeast cells was rapid from SC. Also, comparison of the results from BET for the primary and modified biomass shows an increase in the surface area of the modified biomass as a result of adsorption on clinoptilolite zeolite. The equilibrium adsorption ratio and distribution of uranium hydrolysis products for all samples was calculated and showed that the points corresponding to initial concentrations of less than 0.1 mmol L-1 have higher and narrower absorption fractions. Moreover, the adsorption rate decreases at concentrations higher than 0.2 mmol L-1 compared to low concentrations.