Adsorption of chromium (III) ion from aqueous solution using rice hull ash

Rice hull was calcined to rice hull ash (RHA) at 500 °C under 20 mL air/s for 50 min. The RHA thus prepared has been found to be able to remove chromium (III) ion from aqueous solution, though not very efficient. The experiments indicated that the rate of removal of Cr3+ and the removal of Cr3+ at equilibrium was increased upon decreasing the RHA dosage. The removal could also be enhanced upon increasing the initial chromium concentration, or adsorption temperature. However, pH in the range of 2.5–5.4 or stroke speed higher than 120 stroke/min could not change the removal. The dependence of the RHA dosage and the initial chromium concentration on the removal have been found to be strong, while that of adsorption temperature is mild. An empirical equation correlating the relationship between the removal of Cr3+ and the adsorption time was determined.