Influence of surface conductivity on the apparent zeta potential of TiO2 nanoparticles: Application to the modeling of their aggregation kinetics

• Published in: Journal of colloid and interface science Vol. 406; pp. 75 - 85
• Main Authors: Sameut Bouhaik, Izzeddine, Leroy, Philippe, Ollivier, Patrick, Azaroual, Mohamed, Mercury, Lionel
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15.09.2013; Elsevier
• Subjects: Adjustable; Agglomeration; aquatic environment; aqueous solutions; Chemical Phenomena; Chemistry; Colloidal state and disperse state; Continental interfaces, environment; Crystallites; Derjaguin approximation; dispersions; Double layer; electrical conductivity; electrophoresis; energy; Environmental Sciences; Exact sciences and technology; Extended Stern model; General and physical chemistry; Global Changes; human health; Humans; ionic strength; Kinetics; Linear superposition approximation; Mathematical models; Nanoparticle; Nanoparticles; Nanoparticles - chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; potassium chloride; risk; Sciences of the Universe; Stability ratio; Static Electricity; Surface conductivity; Surface element integration; TiO2; Titanium - toxicity; Titanium dioxide; titration; Zeta potential; Extended Stern model; Nanoparticle; Zeta potential; Surface conductivity; Linear superposition approximation; Stability ratio; Surface element integration; TiO2; Derjaguin approximation; Binary compound; Stability; Transition element compounds; Modeling; Aggregation; Linear approximation; Electrokinetic potential; Models; Kinetics; TiO; Titanium oxide
• DOI: 10.1016/j.jcis.2013.05.034
• ISSN: 0021-9797; 1095-7103

[Display omitted] •The high surface conductivity of TiO2 NPs decreases their electrophoretic mobility.•The zeta potential can be estimated directly from an extended Stern model.•The true zeta potential can be twice that not corrected of surface conductivity.•The effective interaction radius corresponds to that of primary particles.•The aggregation kinetics of TiO2 NPs can be predicted successfully by the DLVO theory. Titanium dioxide nanoparticles (TiO2 NPs) are extensively used in consumer products. The release of these NPs into aquatic environments raises the question of their possible risks to the environment and human health. The magnitude of the threat may depend on whether TiO2 NPs are aggregated or dispersed. Currently, limited information is available on this subject. A new approach based on DLVO theory is proposed to describe aggregation kinetics of TiO2 NPs in aqueous dispersions. It has the advantage of using zeta potentials directly calculated by an electrostatic surface complexation model whose parameters are calibrated by ab initio calculations, crystallographic studies, potentiometric titration and electrophoretic mobility experiments. Indeed, the conversion of electrophoretic mobility measurements into zeta potentials is very complex for metal oxide nanoparticles. This is due to their very high surface electrical conductivity associated with the electromigration of counter and co-ions in their electrical double layer. Our model has only three adjustable parameters (the minimum separation distance between NPs, the Hamaker constant, and the effective interaction radius of the particle), and predicts very well the stability ratios of TiO2 NPs measured at different pH values and over a broad range of ionic strengths (KCl aqueous solution). We found an effective interaction radius that is significantly smaller than the radius of the aggregate and corresponds to the radius of surface crystallites or small clusters of surface crystallites formed during synthesis of primary particles. Our results confirm that DLVO theory is relevant to predict aggregation kinetics of TiO2 NPs if the double layer interaction energy is estimated accurately.