Complexations of Divalent Metallic Ions with Fulvic Acids

Abstract

In this work, the interactions of the functional groups of fulvic acids with copper, cadmium and zinc bivalent ions was investigated by potentiometry. The BEST7 software was employed to investigate the interactions of the functional groups. The software SPE and SPEPLOT were used to generate and to plot the species diagrams. It was used the Suwannee River fulvic acid (SRFA) of the IHSS (International Humic Substances Society) to illustrate the process. The values of the proton dissociation and complexation constants with the divalent ions for each functional group were calculated and their values were very close to those previously published. The functional group present in the highest quantity in the complexes was catechol, and it is complexed with all the divalent ions, although with Cu(II). According to the results obtained by potentiometry, the reactivity series for the divalent ions and the SRFA is: Cu(II) >> Cd(II) > Zn(II). Thus, the method employed could be useful to estimate the role of fulvic acids in the transport of metals in the aquatic environments.