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Adsorption of chromium ion by acid activated carbon-mechanistic and equilibrium studies

S.Arivoli*, P.Martin Deva Prasath, M.Hema

A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing chromium ion. The parameters studied include agitation time, initial chromiumion concentration, carbon dose, pH and temperature. The adsorption followed first order reaction equation and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibriumdata. The adsorption capacity (Qm) obtained fromthe Langmuir isothermplotswere 44.87, 44.24, 42.70 and 43.30 mg/g respectively at an initial pH of 7.0 at 30, 40, 50 and 600C. The temperature variation study showed that the chromium ion adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the chromiumion solutions. Almost 72% removal of chromium ion was observed at 600C. The Langmuir and Freundlich isotherms obtained, positive H0 value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of chromium ion on MCC involves physisorption mechanism.