The speciation of copper(II) ions in dilute solution in the presence of selected amino acid contaminants

Abstract

The stability constants of a number of copper complexes were determined using pHmetric titrations to investigate the effect of complexes, if any, on solubilization of copper. Potentiometric studies were conducted on copper (1I) ions with some selected organic contaminants. The organic contaminants selected are present in the effluents of coffee processing industry. These comprise of amino acids, which include alanine, serine, glycine, lysine, proline and valine. The pH-metric titrations were carried at 25 ± 0.5 °C and ionic strength, I = 0.1 M KN03. Copper and amino acids complexes were investigated to find their possible role in copper solubilization. The molspin pH metric data obtained was further used by SUPERQUAD program to calculate stability constants for the complexes formed. SPECIES program was used to find the most probable models. From the results, it was established that valine, lysine and glycine formed mostly single ligand complexes at pH 6 - 8.5 with log b > 7.9 implying that they are important in holding copper in solution. However, for the mixed ligand complexes investigated; Copper-Valine-Glycine-Hydroxide, Copper-Valine-Glycine and Copper-Glycine-Lysine systems were formed significantly at pH greater than physiological pH range implying that they may not have significant role in the ionic equilibria associated with their transport