Assessment of trace metal binding kinetics in the resin phase of diffusive gradients in thin films
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The dynamic technique of diffusive gradients in thin films (DGT), that measures metal speciation in situ, has found wide environmental application. Simple interpretation of the metal accumulation in terms of a solution concentration has assumed that trace metals do not penetrate beyond the surface of the binding layer, but penetration, although theoretically discussed has not yet been directly measured. Multiple binding layers were used to enable analysis of different depths of a DGT binding phase (Chelex-100 or iminodiacetate resins). In simple metal solution (no ligand) at pH 7, metal penetration to the back layer was low and similar for all metals. However, at lower pH up to 42% of an individual metal accumulated in the back resin layer. This was most noticeable for Mn at pH 4 and 5, but Cd and Co were also affected at pH 4. These results were consistent with rate limited binding, particularly for Mn. A kinetic model successfully fitted the data and allowed derivation of a binding rate constant and the mean distance that metals penetrate into a resin gel (λM). Only for Mn, Co and Cd were experimentally derived λM values greater than the diameter of a Chelex-100 resin bead. For most situations, then, the penetration into the binding layer is negligible and binding of trace metal ions can be regarded as instantaneous, validating the simple use and interpretation of DGT. For weakly binding metals at low pH the slower binding allows penetration, which may affect the DGT measurement.
Is part ofAnalytica Chimica Acta, 2012, vol. 717, num. 2, p. 143-150
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Extending the use of Diffusive Gradients in Thin Films (DGT) to solutions where competition, saturation, and kinetic effects are not negligible Jiménez-Piedrahita, Martín; Altier Infantes, Alexandra; Cecilia Averós, Joan; Puy Llorens, Jaume; Galceran i Nogués, Josep; Rey Castro, Carlos; Zhang, Hao; Davison, William (American Chemical Society, 2017-06-20)DGT (Diffusion Gradients in Thin films) was designed to sample trace metals in situ at their natural concentrations. The setup and the experimental deployment conditions were established to allow interpretation of a linear ...
Dynamics of trace metal sorption by an ion-exchange chelating resin described by a mixed intraparticle/film diffusion transport model. The Cd/Chelex case Quattrini, Federico; Galceran i Nogués, Josep; David, Calin; Puy Llorens, Jaume; Alberti, Giancarla; Rey Castro, Carlos (Elsevier, 2017-06-01)The time-evolution of Cd2+ ion sorption by Chelex 100 resin was studied in batch experiments as a function of time, pH, ionic strength, stirring rate, mass of resin and initial metal ion concentration. In the experimental ...
Jiménez-Piedrahita, Martín; Altier Infantes, Alexandra; Cecilia Averós, Joan; Rey Castro, Carlos; Galceran i Nogués, Josep; Puy Llorens, Jaume (Elsevier, 2015-05-02)Binding resin beads used in DGT (Diffusion Gradients in Thin films) tend to settle to one side of the resin during casting. This phenomenon might be relevant for metal accumulation when partially labile complexes dominate ...