Removal of nickel from aqueous solution using activated red mud

Abstract

Red mud, a collosal solid waste from bauxite processing, was treated by simple dissolution in hydrochloric acid and reprecipitation by ammonia to produce activated red mud (ARM). This material was used to remove nickel(II) Aom aqueous solution. Various parameters like pH, contact time, temperature, ARM to metal ion ratio were determined for the best results. More than 60% removal of nickel(II) was achieved for an initial concentration of 10 ppm. Removal of metal ion improves by raising pH of the medium upto 6.5 but thereafter drops due to precipitation of metal hydroxides. Increase in rate of adsorption was observed with rise in temperature. The loading capacity of ARM increased with higher nickel(II):ARM ratio and reached a plateau at 1:250 by weight. More than 90% nickel(II) removal at 10 ppm initial concentration was observed for ARM dose of 20gms/L. The experimental data agreed well with Langmuir and Freundlich adsorption isotherms.