Adsorption of Uranium on a Novel Bioadsorbent-Chitosan-Coated Perlite

Abstract

Chitosan was coated on an inert substrate, perlite, and was prepared as spherical beads for adsorption of uranium from aqueous solutions. The uptake capacity of chitosan-coated perlite beads for uranium varied from 98.9 to 149 000 μg/g when the equilibrium concentration of uranium in the solution ranged from 11 ppb (11 μg/l) to 1000 ppm (10 × 10⁶ μg/l) and the solution pH was 5. The adsorption capacity of chitosan-coated perlite beads for uranium decreased by 75% in the presence of 0.45 M NaCl, whereas the adsorption capacity decreased by 55% when TiO₂ was added to the beads during their preparation. The adsorption capacity of TiO₂-containing chitosan beads for uranium was found to be in the range of 2.5 to 40 μg of uranium per gram of beads when the concentration of uranium was 39 to 734 μg/l in the presence of 0.45 M NaCl. It was in the range of 18 to 302 μg of uranium per gram of beads when the concentration was 990 to 47 000 μg/l in the presence of 0.45 M Na₂CO₃. Chitosan-coated beads were found to preferentially adsorb uranium, Cd, and Cr from a mixture containing these ions along with Sr and Cs. Only a negligible amount of Sr and Cs was adsorbed by chitosan-coated beads. The data suggest that the chitosan-coated beads can be used for both extraction of uranium from waste streams and also from a highly acidic medium such as a reprocessing stream that uses nitric acid.