Tailoring Activated Carbon Properties for Pb(II) and Cr(VI) Removal from Water in Continuous Mode

Dynamic adsorption of Cr(VI) and Pb(II) in single and binary mixture solutions at different pH values (2 and 6) was studied on activated carbons obtained by chemical activation of olive stones with different agents. The activated carbons exhibited large surface areas with diverse pore size distributions and surface chemistry. The adsorption tests, performed in continuous mode, revealed the existence of different adsorption sites for Pb(II) and Cr(VI). Besides, they emphasized the significant role of the pH, both of the medium and of the carbon surface, in the adsorption of Cr(VI). That is, an acidic medium favors the retention of Cr(VI) on activated carbon having a surface pH around 2 whereas an activated carbon with a more neutral surface shows high efficiency for binary mixtures at high contaminant concentrations for solulions at pH 6.