This paper describes modification of LECA (light expanded clay aggregate) with Fenton reagent and determines removal of arsenite and arsenate ions from an aqueous solution. The influence of pH, contact time and Fe2+/H2O2 on modification were investigated and adsorption characteristics were examined before and after modification. Isotherm studies were carried out by studying the effects of various parameters such as pH, contact time, adsorbent concentration and initial concentration of arsenite and arsenate. The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models, and the model parameters were evaluated. One gram of LECA is found enough to remove 96% and 99% of the As (III) and As (V) from an aqueous solution of 150 mu g L-1 at pH2 and 4 respectively with a shaking time of 60 min. Column adsorption results indicated that no arsenic was found in the effluent solution up to about 10 and 18 bed volumes of As (III) and As (V), respectively. (C) 2011 Elsevier B.V. All rights reserved.