Adsorption of Selected Amino Acids at the Mercury/Aqueous Solution Interface from the Chlorate (VII) and Its Dependence on the Supporting Electrolyte Concentration

Abstract

In this study, we compared the adsorption of methionine, cysteine and cystine at the mercury/chlorate (VII) interface. Changes in the surface tension with the potential of the zero charge γ z and relative surface excess Γ' of methionine, cysteine and cystine as a function of their concentration indicate that the adsorption of the studied amino acids increases in the order of methionine > cystine > cysteine. For all the systems examined, linear dependences ln[×(1–Θ)/Θ = f(Θ)] (Frumkin isotherm) and ln (Γ/c) = f(Γ') (virial isotherm) were obtained. Changes in the adsorption parameters as a function of the supporting electrolyte concentration indicate the competitive adsorption of amino acids and ClO 4 − ions and electrostatic interactions between the water dipoles and adsorbates in the double layer.