J. Phys. IV France 107 (2003) 769
Ferricyanide-humate formationL. Leita1, G. Petruzzelli2 and F. Fornasier1
1 Experimental Institute for Plant Nutrition, via Trieste 23, 34170 Gorizia, Italy
2 Istituto perla Chimica del Terreno, CNR-Area della Ricerca, via Moruzzi 1, 56124 Pisa, Italy
We studied the complexation of ferricyanide ion by humic substances (HS) at acidic, neutral and basic pH by means of cyclic voltammetry (CV) and UV-visible spectroscopy. The CV measurements carried out at pH 3.5 and 7 showed that the first addition of HS (0.05 mg mL -1 of organic carbon) to ferricyanide solution caused a shift of both cathodic and anodic peak potentials together with a depression of the corresponding peak currents. After successive addition of HS further depression of peak currents were observed. Experiments perfonned at pH 12.5 showed no changes in peak current and peak potential after addition of HS. These results suggested the formation of ferricyanide-HS complexes at pH 3.5 and 7 and were confirmed by UV-Vis spectra recorded in concomitance to voltammetric measurements.
© EDP Sciences 2003