Immobilization of Arsenic on Rice Husk

Abstract

The adsorption potential of rice husk was investigated for arsenic ions from aqueous solution as a function of the appropriate electrolyte, contact time, concentrations of the adsorbent and adsorbate, effect of diverse ions and temperature. A radiotracer technique has been used to determine the distribution of arsenic employing a batch method. Maximum adsorption was observed at 0.01 mol/l acid solution (HNO3, HCl, H2SO4 and HClO4) using 1.0 g of adsorbent for 5.97 × 10−3 mol/l arsenic concentration and an equilibration time of 5 min. Studies showed that adsorption decreased with an increase in the concentration of all the acids studied. The adsorption data conformed to the Freundlich isotherm over the concentration range from 8.69 × 10−5 to 1.73 × 10−3 mol/l arsenic. Characteristic Freundlich constants, i.e. 1/n = 0.83 ± 0.06 and K = 4.43 ± 0.16 mmol/g were computed for the sorption system. The uptake of arsenic increased with increasing temperature. Thermodynamic quantities, i.e. ΔG0. ΔS0 and ΔH0, were also calculated for the system. The sorption process was found to be endothermic.