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 tothose previously published. The functional group present in the highest quantity in the complexes was cathecol, and it complexed with all the divalent ions, although to a greater extent 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.

Highlights

  • The study of the complexation of potential toxic metals at natural systems by substances as fulvic acids, which are in fresh-waters, for example, is important because these reactions can determine the metal speciation and bioavailability of the metal species

  • In this work, the interactions of the functional groups of fulvic acids with copper, cadmium and zinc bivalent ions was investigated by potentiometry

  • According to the results obtained by potentiometry, the reactivity series for the divalent ions and the Suwannee River fulvic acid (SRFA) is: Cu(II) >> Cd(II) > Zn(II)

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Summary

Introduction

The study of the complexation of potential toxic metals at natural systems by substances as fulvic acids, which are in fresh-waters, for example, is important because these reactions can determine the metal speciation and bioavailability of the metal species. Copper and zinc are prevalent in nature due to their high industrial use, and they can affect growth of plants, according their metal concentration. Their bioavailability is influenced by physical factors such as temperature, phase association, adsorption and sequestration. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. To elucidate the titration curves of the fulvic acids and zinc (II), cadmium (II) and copper (II) ion complexation it was used the BEST7 software and the software SPE and SPEPLOT

Experimental setup
Results and discussion
Conclusions

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