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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 (HNO 3 , HCl, H 2 SO 4 and HClO 4 ) 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. ΔG 0 . ΔS 0 and ΔH 0 , were also calculated for the system. The sorption process was found to be endothermic.