title: Heteroaggregation of titanium dioxide nanoparticles with model natural colloids under environmentally relevant conditions.
abstract: The heteroaggregation of engineered nanoparticles (ENPs) with natural colloids (NCs), which are ubiquitous in natural surface waters, is a crucial process affecting the environmental transport and fate of ENPs. Attachment efficiencies for heteroaggregation, α hetero, are required as input parameters in environmental fate models to predict ENP concentrations and contribute to ENP risk assessment. Here, we present a novel method for determining α hetero values by using a combination of laser diffraction measurements and aggregation modeling based on the Smoluchowski equation. Titanium dioxide nanoparticles (TiO2 NPs, 15 nm) were used to demonstrate this new approach together with larger silicon dioxide particles (SiO2, 0.5 μm) representing NCs. Heteroaggregation experiments were performed at different environmentally relevant solution conditions. At pH 5 the TiO2 NPs and the SiO2 particles are of opposite charge, resulting in α hetero values close to 1. At pH 8, where all particles are negatively charged, α hetero was strongly affected by the solution conditions, with α hetero ranging from <0.001 at low ionic strength to 1 at conditions with high NaCl or CaCl2 concentrations. The presence of humic acid stabilized the system against heteroaggregation.
authors.affiliation: Institute for Chemical and Bioengineering, ETH Zurich , 8093 Zurich, Switzerland.
authors.forename: Antonia
authors.initials: A
authors.lastname: Praetorius
authors.forename: Jérôme
authors.initials: J
authors.lastname: Labille
authors.forename: Martin
authors.initials: M
authors.lastname: Scheringer
authors.forename: Antoine
authors.initials: A
authors.lastname: Thill
authors.forename: Konrad
authors.initials: K
authors.lastname: Hungerbühler
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Bottero
mesh_terms: D003102:Colloids / Q000737:chemistry*; D004777:Environment; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008962:Models, Theoretical; D053758:Nanoparticles / Q000737:chemistry*; D045483:Rivers / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012996:Solutions; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D003102:Colloids; D006812:Humic Substances; D012996:Solutions; D014867:Water; C009495:titanium dioxide; D012822:Silicon Dioxide; D014025:Titanium