Arsenic(V) adsorption mechanism using kaolinite, montmorillonite and illite from aqueous medium.

The present work investigates the adsorptive behavior of As(V) ions with kaolinite, montmorillonite and illite in aqueous medium as a function of As(V) concentration, pH, contact time and temperature. As(V) adsorption on studied clays were pH dependent and maximum adsorption were achieved in the pH range 2.0-5.0. The adsorption data gave good fits with Langmuir isotherm and yielded Langmuir monolayer capacity of 0.86, 0.64 and 0.52 mg As(V) /g of kaolinite, montmorillonite and illite, respectively. An increase in adsorption temperature resulted in a decrease in the amount of As(V) adsorbed. The results of leaching study showed that, kaolinite was very active clay constituent regarding both As(V) adsorption and mobility. The electrokinetic behavior of both the kaolinite and montmorillonite were modified in the presence of As(V). The shift in isoelectric point indicated that adsorption involves inner sphere surface complexation and strong specific ion adsorption. Kaolinite was successfully tested as an adsorbent for the removal of arsenic from two contaminated groundwater samples containing arsenic in the range 1.36-1.41 mg/L.