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Site Thionville : IUT de Thionville-Yutz - Espace Cormontaigne, F-57970 THIONVILLE-YUTZ - France)
Abstract : Hypothesis Proper evaluation of the intrinsic stability of metals with humic nanoparticles calls for a robust representation of the particulate electrostatic features. Addressing here the case of trivalent metal association with humics for which a significant electrostatic contribution is expected, we report a robust interpretative approach as an alternative to the conventional but approximative Donnan model applied in the speciation codes. Experiments The intrinsic chemical binding affinity of Indium to humic nanoparticles is tackled from equilibrium electroanalytical measurements (Absence of Gradient and Nernstian Equilibrium Stripping) in NaClO4 electrolyte (10-100mM, pH4) at different metal-to-humics concentration ratios. The electrostatic contribution was evaluated using a Poisson-Boltzmann based-approach where the key electrostatic descriptors of humics are involved. Findings The electrochemical results interpreted in the light of so identified non-specific indium binding contribution evidences a dramatic impact of electrostatics on indium complexation by humics, with e.g. in 10mM electrolyte an intraparticulate Boltzmann metal accumulation factor that is ca. 5 times larger than that reported for cadmium and highly-charged fulvics complexants. A successful comparison between theory and experiments is consistently achieved over the tested electrolyte concentrations with the only adjustment of the radius of the metal accumulation spherical volume. The analysis reveals the necessity to consider full equilibration of charged humics with its intraparticulate counterion atmosphere.
Elise Rotureau, José-Paulo Pinheiro, Jerome F. L. Duval. On the Evaluation of the Intrinsic Stability of Indium-Nanoparticulate Organic Matter Complexes. Colloids and Surfaces A: Physicochemical and Engineering Aspects, Elsevier, 2022, pp.128859. ⟨10.1016/j.colsurfa.2022.128859⟩. ⟨hal-03626703⟩