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Apport des spectroscopies moléculaires à l'étude des mécanismes de fixation d'ions métalliques polluants par les substances humiques.
Complexation de Al(III), Pb(II) et Zn(II) par des systèmes modèles.

Abstract : The humic substances (HS) result from the degradation of organic residues and represent the greatest part of the organic matter of the natural systems. The HS are able to trap many pollutants like heavy metals and play a major role in the metal ions retention. Their chelating properties are due mainly to some recurring functions: carboxylic and phenolic groups.
In a 1st part, the study of the complexation of model molecules involving similar sites to those met in the natural biopolymers makes it possible to know the chelating capacities of the most widespread functions (catechol, hydroxy-carbonyl and carboxylic acid). Spectroscopic techniques combined with quantum chemical calculations provides us the chelating capacities classification of the mono-site compounds toward the metallic ions Al(III), Pb(II) and Zn(II). We show whereas that this type of classification is preserved when the sites are in competition within the same structure.
In a 2nd part, the examination by synchronous fluorescence of the 3 polluting metals complexation by a standard humic acid (HA) made it possible to highlight different behaviors for each one of them, reflecting distinct fixing mechanisms and a specificity of the metal-humic interactions. We have established a classification of the chelating powers of HA towards the 3 cations in agreement with those obtained by the models. Lastly, the competition between HA and two organic molecules of low molecular size have shown that the percentages of pollutants extracted to the humic acid are weak and this one remains a "toxic reservoir" in the natural environments.
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Submitted on : Friday, March 6, 2009 - 11:01:51 AM
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Laëtitia Dangleterre. Apport des spectroscopies moléculaires à l'étude des mécanismes de fixation d'ions métalliques polluants par les substances humiques.
Complexation de Al(III), Pb(II) et Zn(II) par des systèmes modèles.. Autre. Université des Sciences et Technologie de Lille - Lille I, 2007. Français. ⟨tel-00366217⟩

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