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, and significant amounts of it are released into the environment in the course of nuclear fuel cycles. In this regard, biosorption technology offers the advantages of low operating costs and high efficiency in metal removal from aqueous solutions. This work evaluated the sorption of uranyl ions from aqueous solutions by Saccharomyces Cerevisiae (SC) on zeolite clinoptilolite. First, natural zeolite was characterized by classical chemical analysis, and then the influence of solution pH, temperature, contact time, and initial concentration on the sorption of uranyl were 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 (ICP-OES). In addition, the results showed that metal binding occurred extracellularly at the cell wall surface and the sorption rate of uranyl ions by free yeast cells was rapid from SC. Further, comparing the results from BET for the primary and modified biomass showed 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 were calculated, indicating that the points corresponding to initial concentrations of less than 0.1 mmol L-1 have higher and narrower absorption fractions. Furthermore, the adsorption rate decreased at concentrations higher than 0.2 mmol L-1 compared to low concentrations.