Abstract: In the present paper the adsorption of anionic dve carmine (CM) on the activatedcarbon under various pH has been studied, and revealed that the zeta potential of the activat-ed carbon has a large effect on the adsorption capacity of CM.The results show that the zetapotential of the carbon surface is positive when the pH of the suspension is lower than pH_zpc.Therefore, with decreasing zeta potential the electrostatic attraction between anionic dye andthe carbon surface greatly reduces the adsorption capacity.On the other hand the colorchange of CM from orange to rose in the pH range 3.5～6.8 results to the solubility increaseof CM with increasing pH,Therefore,the adsorption capacity is gradually reduced and downto vanish.The adsorption kinetics and thermodynamic parameters as a function of pH havebeen evaluated.The mechanism for adsorption of anionic dve CM on the activated carbon hasalso been studied.

Key words: activated carbon, zeta potential, carmine, adsorption isotherm, adsorption mecha-nism