Equilibrium and kinetics studies on removal of arsenite by iron oxide coated activated alumina.

Arsenic in drinking water is causing much concern because of its toxicity. It occurs in water naturally as As(III) and As(V). Of these As (III) is more toxic. Adsorption on activated alumina has been one of the most commonly used methods for As (V) removal from drinking water. But it is not very effective for As (III). Activated alumina was modified by coating it with Iron oxide to make it suitable for As (III) adsorption. Iron oxide coated activated alumina was tested for its effectiveness as an adsorbent for As (III). The As (III) adsorption was strongly dependent on pH and a maximum removal of 98% was observed at a pH of 12. The adsorption process followed a first order kinetics. The equilibrium was attained after 8 hours. The kinetic study was carried out with different initial As (III) concentration. It was observed that time taken to attain equilibrium was independent of initial concentration but percentage removal decreased with increasing initial concentration. The adsorption isotherms were fitted well to both Langmuir and Freundlich equation.