Towards a better understanding on agglomeration mechanisms and thermodynamic properties of TiO2 nanoparticles interacting with natural organic matter

Abstract

Interaction between engineered nanoparticles and natural organic matter is investigated by measuring the exchanged heat during binding process with isothermal titration calorimetry. TiO2 anatase nanoparticles and alginate are used as engineered nanoparticles and natural organic matter to get an insight into the thermodynamic association properties and mechanisms of adsorption and agglomeration. Changes of enthalpy, entropy and total free energy, reaction stoichiometry and affinity binding constant are determined or calculated at a pH value where the TiO2 nanoparticles surface charge is positive and the alginate exhibits a negative structural charge. Our results indicate that strong TiO2-alginate interactions are essentially entropy driven and enthalpically favorable with exothermic binding reactions. The reaction stoichiometry and entropy gain are also found dependent on the mixing order. Finally correlation is established between the binding enthalpy, the reaction stoichiometry and the zeta potential values determined by electrophoretic mobility measurements. From these results two types of agglomeration mechanisms are proposed depending on the mixing order. Addition of alginate in TiO2 dispersions is found to form agglomerates due to polymer bridging whereas addition of TiO2 in alginate promotes a more individually coating of the nanoparticles.

Formation of complexes between hematite nanoparticles and a non-conventional galactomannan gum. Toward a better understanding on interaction processes

“…3 (a and b) indicated that the zeta potential and particle size of hematite NPs suspended in VG will be different if they are added to a VG suspension than if the VG suspension is added to hematite NPs. Such results are also found in good agreement with the findings of Loosli et al (2015). Using isothermal titration calorimetry they found that the mixing procedure between TiO 2 nanoparticles and alginate polysaccharide chains was playing key roles in the complexation mechanisms.…”

Scalable synthesis of an architectural library of well‐defined poly(acrylic acid) derivatives: Role of structure on dispersant performance

“…In order to correlate the performance of these dispersants, isothermal titration calorimetry (ITC) was used to calculate the binding constant ( K a ), enthalpy changes (Δ H ), and thermodynamic parameters for the interaction between different PAA architectures and the surface of TiO 2 particles . Importantly, comparing different polymer architectures with the same DP n eliminates molecular weight effects and allows the influence of structure on dispersant performance to be probed.…”

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

“…It denotes the role of van der Waals interactions (especially for Type I) and change of conformation of SRHA. Such a behavior is not observed when linear natural polysaccharide (alginate) are considered 64 . This was due to the alginate chemical properties for which van der Waals interactions are not favored.…”