Cupric Ion Complexation by Fulvic Acid Extracted from Sewage Sludge-Soil Mixtures
1979
Sposito, Garrison | Holtzclaw, Kenneth M. | LeVesque-Madore, C. S.
The complexes formed between Cu²⁺ and fulvic acid extracted from sewage sludge were investigated by potentiometric titration of K/H fulvate with Cu(ClO₄)₃ at pH 5 and 25°C, in an ionic medium of 0.1M KClO₄. Formation functions, giving the number of moles of Cu²⁺ bound per mole of K/H fulvate, were calculated from the titration data and plotted against the molar concentration of Cu²⁺, with the concentration of K/H fulvate being a fixed parameter for each plot. These functions were analyzed by the Scatchard plot method and were interpreted as evidence of: (i) a relatively strong 1:1 complex (log ᶜK = 3.9) that is formed between Cu²⁺ and the most acidic functional groups in fulvic acid and (ii) a weaker set of complexes (log ᵉK = 2) that is formed between Cu²⁺ and the more weakly acidic functional groups acting as both unidentate and bidentate ligands.
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