Adsorption and desorption of chromium(VI) on active carbon

Abstract

The adsorption and desorption of chromium(VI) ion from aqueous solution on active carbons were studied. The adsorption rate of Cr(VI) ion was measured at various pH values, and was proved to be proportional to its concentration. The chemical species and their respective adsorption rate constants were determined from the pH dependence of the adsorption rate. A desorption experiment of adsorbed Cr(VI) was performed by HNO₃ or NaOH. Only Cr(III) ion was desorbed by HNO₃, while both Cr(III) and Cr(VI) ions were desorbed by NaOH. This shows that Cr(VI) adsorbed on active carbon was reduced to Cr(III) and then Cr(III) was desorbed. The results of Freundlich plot supported the adsorption/desorption mechanism presumed from the experimental results mentioned above.