Removal of chromium and lead from aqueous solution using industrial wastes: batch and column studies

The rotary kiln waste (dolochar) generated in sponge iron plants has been converted into a low-cost adsorbent by heat activation for the removal of chromium and lead from aqueous solution. The effects of particle size, contact time, sorbent dosage, adsorbate concentration, pH and temperature on the sorption of both the metal ions were studied in batch experiments. Kinetic studies were also conducted to have an idea on the sorption mechanism of the process. The uptake of lead was found to be more than that of chromium. Adsorption on dolochar followed Freundlich isotherm. The kinetics of the Cr(VI) and Pb(II) adsorption on the kiln waste was found to follow a pseudo-second-order rate equation. It was observed that the sorption process was spontaneous and the adsorbent is suitable for sorption of both ions. In addition, fixed bed studies were performed to simulate real-life conditions. The experiments were also performed to regenerate the column by 0.2 N HNO3 for lead-dolochar system and 0.5 M NaOH for chromium-dolochar system for reuse.