| Abstract
| - An electrostatic model has been used in the analysis ofthe fulvic acid-copper ion complexation with the aimof estimating the contribution of the electrostatic effect tometal binding and calculating the intrinsic complexationparameters in solutions with a dissolved organic carbon(DOC) analogous to that in natural media such as aqueousenvironments and soil solution. For this purpose solutionsof a soil extracted fulvic acid (FA) at concentrations 30,40, 50, and 60 mg L-1 and ionic strengths 0.001, 0.005, 0.01,0.05, and 0.1 were titrated at pH 6.5 with copper ion byusing differential pulse anodic stripping voltammetry. Bymeans of a 1:1 nonelectrostatic model conditionalcomplexation parameters (apparent stability constant andcomplexation capacity) were calculated, and theirdependence on the FA concentration and ionic strengthwas demonstrated. Consideration of a second binding siteand assumption of bidentate binding sites do notsignificantly affect the results. The application of a 1:1electrostatic model with the geometric parameters derivedfrom a previous study of the proton binding reaction ofthe fulvic acid allowed us for the obtention of the intrinsicstability constants which do not exhibit any dependenceon the FA concentration nor on the ionic strength. Comparisonof the apparent and intrinsic stability constants shows asignificant contribution of the electrostatic effect on the coppercomplexation.
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