Article pubs.acs.org/est
Variability of Zinc Oxide Dissolution Rates Monika Michaelis,† Cornelius Fischer,*,‡ Lucio Colombi Ciacchi,†,§ and Andreas Luttge‡,§,∥ †
Hybrid Materials Interfaces Group, Faculty of Production Engineering, Bremen Center for Computational Materials Science (BCCMS), and Center for Environmental Research and Sustainable Technology (UFT), University of Bremen, Am Fallturm 1, 28359 Bremen, Germany ‡ Marum & Fachbereich Geowissenschaften, Universität Bremen, Klagenfurter Straße, 28359 Bremen, Germany § MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany ∥ Earth Science Department, Rice University, 6100 Main Street, Houston, Texas 77005, United States S Supporting Information *
ABSTRACT: Zinc oxide (ZnO) is of widespread use for numerous applications, including many in the cosmetic industry. Thus, ZnO particles are quite likely to enter the environment. ZnO may be harmful because of the release of cytotoxic Zn2+ ions during dissolution reactions. Here, we analyze the dissolution kinetics of the polar zinc-terminated (000−1) and nonpolar (10−10) crystal surfaces in ultrapure water to examine the impact of the crystal defects on dissolution. By using a complementary approach of atomic force microscopy and vertical scanning interferometry, we quantify the difference in reaction rate between the crystal faces, the overall range of rate variability, and the rate components that combine to an overall rate. The mean dissolution rate of the (000−1) crystal surface is more than 4 times that of the (10−10) surface. By using the rate spectrum analysis, we observed an overall dissolution rate variability of more than 1 order of magnitude. The rate components and the range of dissolution rate are important input parameters in reactive transport models for the prediction of potential release of Zn2+ into the environment.
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ROS species.14 The following biological responses depend on the relative abundance and the involved cellular pathways.13 Additionally, the photocatalytic activity of ZnO NPs might cause toxic actions promoting an additional generation of ROS.13 According to Bondarenko et al., ZnO NPs are most toxic to algae (
