Equilibrium and kinetics studies for As(III) adsorption on activated alumina and activated carbon

Equilibrium adsorption isotherms of As(III) were obtained from the experimentally generated data on activated alumina and activated carbon at temperature 303 K and pH 7.4. The isotherm for As(III) on activated alumina was typically of Brunauer Type-I but in the case of activated carbon equilibrium capacity seems to be increasing with increase in concentration. Langmuir isotherm model best represents the experimental data for As(III) in activated alumina and Freundlich model in activated carbon. Model parameters such as saturation capacity of adsorbent qs, Langmuir constant b, and Freundlich constants K and n were determined. Saturation adsorption capacity of As(III) in activated carbon was much higher than that in activated alumina. Overall effective mass transfer coefficient k was determined using uptake rate method. It is observed that k was independent of concentration of As(III). Values of k for both the adsorbents are of the order of 10(-2) min(-1).