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

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 g/g when the equilibrium concentration of uranium in the solution ranged from 11 ppb (11 g/l) to 1000 ppm (10 × 10⁶ g/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 g of uranium per gram of beads when the concentration of uranium was 39 to 734 g/l in the presence of 0.45 M NaCl. It was in the range of 18 to 302 g of uranium per gram of beads when the concentration was 990 to 47 000 g/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.