Complexation of Cu~(2+),Zn~(2+)and Fe~(3+) Metal Ions with Humic

The humic substances-fulvic acid(FA)and humic acid(HA) and their complexations with metal ions Cu~(2+),Zn~(2+)and Fe~(3+) were investigated by using potentiometric titration. The formation constants of the metal ion complexes with HA and FA were obtained by graphical approaches. It was found that formation constants decrease with the increasing concentration of metal in the solution.The formation constants of FA are larger than those of HA and the formation constants of Cu~(2+) and Fe~(3+) are larger than those of Zn~(2+).