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Isothermal titration calorimetry as a powerful tool to quantify and better understand agglomeration mechanisms during interaction processes between TiO2 nanoparticles and humic acids

Published inEnvironmental science. Nano, vol. 2, p. 541-550
Publication date2015
Abstract

The association processes between engineered TiO2 nanoparticles and Suwannee River humic acids are investigated by isothermal titration calorimetry and by measuring the exchanged heat during the binding process, allowing the determination of thermodynamic (change in enthalpy, Gibbs free energy and entropy) and reaction (binding affinity constant, reaction stoichiometry) parameters. Our results indicate that strong TiO2–Suwannee River humic acid interactions are entropically and enthalpically favorable with exothermic binding reactions and that the mixing order is also an important parameter. High humic acid concentrations induce homoagglomeration (“self”-assembly) and are shown to favor an enthalpically driven association process. Light scattering techniques are also considered to investigate the influence of TiO2 surface charge modifications and agglomeration mechanisms. Patch and bridging mechanisms are found to result in the formation of large agglomerates once charge inversion of TiO2–humic acid complexes is achieved. Moreover, van der Waals interactions are also found to play a significant role during interaction processes due to the amphiphilic character of humic acids.

Keywords
  • TiO2 nanoparticles
  • Humic acids
  • Natural organic matter
  • Isothermal titration calorimetry
  • Metal oxide stability
  • Aquatic systems
Funding
Citation (ISO format)
LOOSLI, Frédéric et al. Isothermal titration calorimetry as a powerful tool to quantify and better understand agglomeration mechanisms during interaction processes between TiO<sub>2</sub> nanoparticles and humic acids. In: Environmental science. Nano, 2015, vol. 2, p. 541–550. doi: 10.1039/C5EN00139K
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Article (Published version)
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ISSN of the journal2051-8153
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Technical informations

Creation10/01/2015 11:54:00 AM
First validation10/01/2015 11:54:00 AM
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