COMPARISON OF THE BEHAVIORS OF COPPER, CADMIUM AND LEAD IN THE PRESENCE OF HUMIC-ACID IN SODIUM-CHLORIDE SOLUTIONS

The electrochemical oxidation-reduction processes of copper, cadmium and lead in the presence of humic acid (HA) in sodium chloride solutions were compared, taking into account the differences in the speciation of these heavy metal ions and the type of the HA used. The complexation properties of HA for the metal ions in the solution were studied. The adsorption properties of the HA and the influence of the adsorbed layer of HA formed at the mercury electrode/solution interface were examined. The electrochemical processes of copper ions are mainly influenced by the complexation properties of HA, whereas cadmium and lead are mainly influenced by the presence of the adsorbed layer of HA on the electrode surface.