Complexation of Copper (II), Cadmium (II) and Lead (II) with Humic and Fulvic Acids of Yamuna River Sediments

Abstract

The complexation of humic and fulvic acids extracted from Yamuna river sediments, collected in summer and winter months with Cu⁺², Cd⁺² and Pb⁺² were investigated at different pH of the medium employing ion selective electrode potentiometry. The different complexation parameters were computed from Double Surface Langmuir, Scatchard and Hill plots. The degree of complexation was found to increase with increase in pH and decrease with rise in total metal concentration. Maximum binding abilities of humic acids were higher than those of fulvic acids. As regards the metal ions, the conditional stability constants were found to increase with increase in pH and follow the order: Cu-L > Pb-L > Cd-L. Metal-humates were found to be more stable than metal-fulvates. The ligands extracted from the sediments collected in summer showed stronger metal binding ability than those extracted from winter samples. The cooperative binding ability of the ligands did not indicate any trend of variation and thus was found to be an unreliable parameter to assess the complexation behaviour of the poly-functional humic and fulvic acids towards metals.