Adsorption of chromium(VI) on chitosan-coated Perlite

Chitosan-coated perlite beads were prepared by drop-wise addition of a liquid slurry containing chitosan and perlite to an alkaline bath. The beads were characterized by SEM and EDS x-ray microanalysis. The chitosan content of the beads was 23%, as determined by a pyrolysis method. Adsorption of hexavalent chromium from aqueous solutions on chitosan-coated perlite beads was studied under both equilibrium and dynamic conditions. The effect of pH on adsorption was also investigated. The data were fitted to the Langmuir adsorption isotherm. The adsorption capacity of chitosan-coated perlite was found to be 104 mg/g of adsorbent from a solution containing 5000 ppm of Cr(VI). On the basis of chitosan, the capacity was 452 mg/g of chitosan. The capacity was considerably higher than that of chitosan in its natural and modified forms, which was in the range of 11.3 to 78 mg/g of chitosan. The beads loaded with chromium were regenerated with sodium hydroxide solution of different concentrations. A limited number of adsorption-desorption cycles indicated that the chitosan-coated beads could be regenerated. and. reused to remove Cr(VI) from waste streams.