Adsorption of phthalic acid on mercury electrodes

Abstract

The adsorption of o-phthalic acid (H2Pht) on mercury electrodes was studied in the pH range 0.5–11.5 using surface tension, double layer capacity, and zero charge potential measurements. The calculated adsorption isotherms indicate a reorientation of H2Pht molecules from flat to vertical orientation with increase of H2Pht concentration in the solution. These results combined with the change of the zero charge potentials suggest that in the vertical position —COOH groups are directed to the surface of the metal. The change in the adsorption of phthalic acid at different pH's was explained by the different adsorbability of free acid H2Pht and its ions HPht− and Pht2−.