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SynopsisChitosan prepared from fresh water crab shells was used for hexavalent chromium removal. Kinetic studies indicated a rapid removal of chromium from aqueous solutions. The first-order rate constant for chromium removal was calculated to be 1.92 h-I. Sorption isothermal data could be interpreted by the Langmuir relationship. Drastic decrease in chromium removal was observed with the increase in pH. Sorption was almost 90% at pH 3 at an initial chromium concentration of 5 mg/L and reduced to 10% at pH 7 and above. Presence of electrolytes and chloride significantly affected the chromium removal, indicating the electrostatic attraction as the main removal mechanism. Regeneration of the sorbent with alkali was not very effective as only 60-65% of sorbed chromium could be recovered.

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