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Communication Dans Un Congrès Année : 2022

Unravelling the electrostatic and chemical components of the stability of indium-nanoparticulate humics complexes

Résumé

The fundamental role played by electrostatics on the binding of trivalent metal ions (Indium) to humic nanoparticles (HNPs, 5 nm radius) was here investigated so as to evaluate the intrinsic (chemical) stability of In-HNPs complexes [1]. To that end, a set of apparent stability constants was experimentally obtained at various metal-to-ligand ratios and ionic strengths using the electroanalytical technique AGNES (Absence of Gradient and Nernstian equilibrium stripping) well-adapted to measure free indium concentrations at the nanomolar level [2,3]. Following the strategy developed by Town et al. [4], the Boltzmann factors which quantify the electrostatically-driven partitioning of free indium ions and its cationic hydrolysis products between HNP body and bulk solution, were computed by solving the nonlinear Poisson Boltzmann (PB) equation for soft nanoparticles [5]. The PB-based modelling captures the magnitude and structure of particle electric field operating in the extra- and/or intra-particulate regions with or without considering the neutralization of the structural HNP charges due to accumulation of counterions from electrolyte solution. By taking into account HNP charge neutralization effects on the particle electric field distribution, we found a consistent agreement between theory and experiments over the whole range of tested electrolyte concentrations. Our results reveal a significant metal ions accumulation in the intraparticulate body of HNP particles. The intrinsic stability constants of In-HNP complexes were then recovered from their apparent counterparts and reported for several metal-to-site coverages. Finally, we demonstrated that the Donnan electrostatic representation implemented within popular NICA-Donnan speciation code, were unable to recover the here-reported experimental results, mainly due to its incapability to properly capture the bell-shaped potential profiles operational within and outside HNP nanoparticles.
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Dates et versions

hal-04283887 , version 1 (14-11-2023)

Identifiants

  • HAL Id : hal-04283887 , version 1

Citer

Elise Rotureau, José P. Pinheiro, Jérôme F.L. Duval. Unravelling the electrostatic and chemical components of the stability of indium-nanoparticulate humics complexes. Interfaces against pollution, University of Antwerp, Sep 2022, Antwerpen, Belgium. ⟨hal-04283887⟩
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