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Assessment of labilities of metal complexes with the dynamic ion exchange technique.

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Quattrini, Federico; Galceran, Josep; Rey-Castro, Carlos; Puy, Jaume; Fortin, Claude (2019). Assessment of labilities of metal complexes with the dynamic ion exchange technique. Environmental Chemistry , vol. 16 , nº 3. p. 151-164. DOI: 10.1071/EN18202.

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Résumé

The dynamic ion exchange technique (DIET) is proposed to provide speciation information, which can be used to establish links with metal bioavailability in natural waters. The experimental setup consists of a few milligrams of a sulfonic acid type ion exchange resin packed in a plastic microcolumn that is coupled to a peristaltic pump for a sample to interact with the resin which is subsequently eluted. The evolution of both the accumulated number of moles in the resin and the concentration of the effluent can provide information on the dissociation of different metal-ligand complexes when compared with the transport properties. This information can be converted into the lability degree of a given complex or the DIET concentration cDIET, which accounts for the labile fraction contributing to the metal accumulation by the resin column at the operation conditions. cDIET can be extended to columns containing chelating resins (such as those with Chelex) or to chromatography. A comprehensive modelling of the involved phenomena (such as diffusion, advection, reaction kinetics and electrostatic partitioning) leads to the quantitative interpretation of the accumulation time series (accumulation curves) or effluent evolution (breakthrough curves). Particularly simple analytical expressions can be used for short exposure times, when a (quasi) steady-state is attained. These models have been checked against the results from complexes of Cu and Ni with ligands, such as ethylenediamine, and ethylenediaminetetraacetic, iminodiacetic, glutamic, salicylic, malonic and malic acids, which yield complexes with contrasting charges. Caution is advised when estimating the free metal fraction from DIET measurements, as cDIET and the free metal concentration can be considered to be equal only in the case of extremely inert complexes.

Type de document: Article
Mots-clés libres: availability; ion exchange columns; trace metal speciation
Centre: Centre Eau Terre Environnement
Date de dépôt: 29 nov. 2019 13:54
Dernière modification: 29 nov. 2019 13:54
URI: http://espace.inrs.ca/id/eprint/8495

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