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dc.contributor.authorDavid, Calin
dc.contributor.authorMongin, Sandrine
dc.contributor.authorRey Castro, Carlos
dc.contributor.authorGalceran i Nogués, Josep
dc.contributor.authorCompanys Ferran, Encarnació
dc.contributor.authorGarcés, Josep Lluís
dc.contributor.authorSalvador, José
dc.contributor.authorPuy Llorens, Jaume
dc.contributor.authorCecilia Averós, Joan
dc.contributor.authorLodeiro, Pablo
dc.contributor.authorMas, Francesc
dc.description.abstractInformation on the Pb and Cd binding to a purified Aldrich humic acid (HA) is obtained from the influence of different fixed total metal concentrations on the acid-base titrations of this ligand. NICA (Non-Ideal Competitive Adsorption) isotherm has been used for a global quantitative description of the binding, which has then been interpreted by plotting the Conditional Affinity Spectra of the H+ binding at fixed total metal concentrations (CAScTM). This new physicochemical tool, here introduced, allows the interpretation of binding results in terms of distributions of proton binding energies. A large increase in the acidity of the phenolic sites as the total metal concentration increases, especially in presence of Pb, is revealed from the shift of the CAScTM towards lower affinities. The variance of the CAScTM distribution, which can be used as a direct measure of the heterogeneity, also shows a significant dependence on the total metal concentration. A discussion of the factors that influence the heterogeneity of the HA under the conditions of each experiment is provided, so that the smoothed pattern exhibited by the titration curves can be justified.
dc.description.sponsorshipThis work was financially supported by the Spanish Ministry of Education and Science (Projects CTQ2006-14385, CTM2006-13583, CTQ2009-07831 and CTQ2009-14612), from the “Comissionat d’Universitats i Recerca de la Generalitat de Catalunya” 2009SGR00465 and XRQTC. S. Mongin acknowledges a FPI fellowship from Ministerio de Educacion y Ciencia of Spain. P. Lodeiro gratefully acknowledges financial support from Xunta de Galicia through Ángeles Alvariño projects AA 10.02.56B.444.0 and 10.02.561B.480.0, both co-funded by European Social Funds
dc.relation.isformatofVersió postprint del document publicat a:
dc.relation.ispartofGeochimica et Cosmochimica Acta, 2010, vol. 74, num. 18, p. 5216-5227
dc.rightscc-by-nc-nd (c) Elsevier, 2010
dc.subjectMacromolecular complexation
dc.subjectAffinity spectrum
dc.subjectTrace metal speciation
dc.titleCompetition effects in cation binding to humic acid: conditional affinity spectra for fixed total metal concentration conditions

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cc-by-nc-nd (c) Elsevier, 2010
Except where otherwise noted, this item's license is described as cc-by-nc-nd (c) Elsevier, 2010