Immobilization of arsenic on rice husk

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 x 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 x 10(-5) to 1.73 x 10(-3) mol/l arsenic. Characteristic Freundlich constants, i.e. l/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. Delta G(0), Delta S-0 and Delta H-0, were also calculated for the system. The sorption process was found to be endothermic.