Joint Adsorption of Organic Anions on Passive Iron

The adsorption of anions of 3-hydroxy-2-naphthoic acid (HNA) from a borate buffer of pH 7.4 on the surface of iron oxidized at 0.0 V is studied by the ellipsometry technique coupled with electrochemical measurements and is described by the Frumkin isotherm. The joint adsorption of anions of HNA and mepheneamino acid (MAA) is studied at high concentrations at 0.2 V. As opposed to low concentrations of the mixture components (when joint adsorption on passive iron increases), at a high coverage by one of these, this effect is absent. At a high concentration of one component, adding identical amount of the other makes no impact on the coverage by the former. The joint adsorption of anions of HNA and N-phenylanthranilic acid on passive iron is studied at 0.0 and 0.2 V; the relevant isotherms and adsorption constants are obtained. Variations in the ellipsometric angle Δ during adsorption of MAA and its mixture with HNA are examined.