Adsorption of hexavalent chromium from aqueous solution by using activatedred mud

Adsorption by activated red mud (ARM) is investigated as a possible alterna tive to the conventional methods of Cr(VI) removal from aqueous synthetic s olutions and industrial effluents. Adsorption characteristics suggest the h eterogenous nature of the adsorbent surface sites with respect to the energ y of adsorption Various factors such as pH, contact time, Cr(VI) concentrat ion, amount of adsorbent, and temperature are taken into account, and promi sing results are obtained. The applicability of the Langmuir as well as Fre undlich adsorption isotherms for the present system is tested. The loading factor (i.e., milligrams of Cr(VI) adsorbed per gram of ARM) increased with initial Cr(VI) concentration, whereas a negative trend was observed with i ncreasing temperature. The influence of the addition of anions on the adsor ption of Cr(VI) depends on the relative affinity of the anions for the surf ace and the relative concentrations of the anions. (C) 1999 Academic Press.