A COMPARISON OF THE SORBTIVE CHARACTERISTICS OF LEAF MOLD AND ACTIVATED CARBON COLUMNS FOR THE REMOVAL OF HEXAVALENT CHROMIUM

Previous batch studies have shown that leaf mould is a potentially use ful biosorbent for the treatment of wastewaters contaminated with hexa valent chromium. This paper examines its use for continuous adsorption in columns and compares the results with a parallel study using an ac tivated carbon column. Both columns were operated at a pH of 2.5 and a flow-rate of 74 ml/min. The results show that, although the Cr(VI) ad sorption capacities of the leaf mould were only 25.9 mg/g compared wit h a value of 75.6 mg/g for the activated carbon, the leaf mould caused little or no reduction and produced an effluent with very low concent ration of trivalent chromium. The activated carbon, on the other hand, had a high reducing action. The data were also tested against the Bed -Depth-Service-Time model and it was found that, although the complian ce was nonlinear, the model was appropriate for design purposes.