title: Chemical interactions between Nano-ZnO and Nano-TiO2 in a natural aqueous medium.
abstract: The use of diverse engineered nanomaterials (ENMs) potentially leads to the release of multiple ENMs into the environment. However, previous efforts to understand the behavior and the risks associated with ENMs have focused on only one material at a time. In this study, the chemical interactions between two of the most highly used ENMs, nano-TiO2, and nano-ZnO, were examined in a natural water matrix. The fate of nano-ZnO in Lake Michigan water was investigated in the presence of nano-TiO2. Our experiments demonstrate that the combined effects of ZnO dissolution and Zn adsorption onto nano-TiO2 control the concentration of dissolved zinc. X-ray absorption spectroscopy was used to determine the speciation of Zn in the particulate fraction. The spectra show that Zn partitions between nano-ZnO and Zn2+ adsorbed on nano-TiO2. A simple kinetic model is presented to explain the experimental data. It integrates the processes of nano-ZnO dissolution with Zn adsorption onto nano-TiO2 and successfully predicts dissolved Zn concentration in solution. Overall, our results suggest that the fate and toxicity potential of soluble ENMs, such as nano-ZnO, are likely to be influenced by the presence of other stable ENMs, such as nano-TiO2.
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Tiezheng
authors.initials: T
authors.lastname: Tong
authors.forename: Kaiqi
authors.initials: K
authors.lastname: Fang
authors.forename: Sara A
authors.initials: SA
authors.lastname: Thomas
authors.forename: John J
authors.initials: JJ
authors.lastname: Kelly
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Gray
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Gaillard
mesh_terms: D000327:Adsorption; D004777:Environment; D060106:Lakes / Q000737:chemistry; D008824:Michigan; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D012996:Solutions; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy; D015032:Zinc / Q000302:isolation & purification; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D012996:Solutions; D014867:Water; C009495:titanium dioxide; D014025:Titanium; D015032:Zinc; D015034:Zinc Oxide