Competition effects in cation binding to humic acid: conditional affinity spectra for fixed total metal concentration conditions
| Autor: | Calin David, Francesc Mas, J. L. Garces, Carlos Rey-Castro, José Salvador, Sandrine Mongin, Jaume Puy, Pablo Lodeiro, Josep Galceran, Encarnació Companys, Joan Cecília |
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| Přispěvatelé: | Universitat de Barcelona |
| Rok vydání: | 2010 |
| Předmět: |
Cation binding
Titration curve Proton binding Àcid húmic Inorganic chemistry Affinity spectrum chemistry.chemical_element Acid–base titration Metal Equilibri àcid-base Geochemistry and Petrology NICA Humic acid chemistry.chemical_classification Cadmium Chromatography Macromolècules Ligand (biochemistry) Polyelectrolytes Macromolecular complexation Trace metal speciation Acid-base equilibrium chemistry Macromolecules visual_art visual_art.visual_art_medium Polielectròlits |
| Zdroj: | Repositorio Abierto de la UdL Universitad de Lleida Dipòsit Digital de la UB Universidad de Barcelona Recercat. Dipósit de la Recerca de Catalunya instname |
| Popis: | Information 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. This 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 |
| Databáze: | OpenAIRE |
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