John Wiley & Sons, Ltd.

Uncoated and coated ZnO nanoparticles life cycle in synthetic seawater

The increasing production of nanoparticles has raised strong concerns regarding their environmental release. In nanoparticles life cycle scenarios, marine systems constitute one of the main final compartments, and nanoparticles fate in these environments needs to be assessed. Here, dissolution kinetics of commercial uncoated and organic‐coated ZnO nanoparticles in synthetic seawater has been investigated using Donnan Membrane Technique, and 1000 daltons pore size ultrafiltration. Uncoated nanoparticles reach a maximum in dissolution within the first hour, around 24% of total ZnO at pH 8.2, and 4% at pH 7.7, followed by secondary carbonated phases precipitation (hydrozincite) until the system reaches a steady state after 30 days of interaction. Assuming a pseudo first order kinetics for hydrozincite precipitation allowed to calculate kinetics constants values k'p of −208.10−4 ± 15. 10−4 mol L−1 h−1 at pH 7.7, and ‐57.10−4 ± 11.10−4 mol L−1 h−1 at pH 8.2. Presence of organic coating drastically modifies the nanoparticles life cycle, with a maximum in dissolution reached after 7 days of interaction, followed by a stationary phase lasting from 1 to 3 weeks, and a subsequent Zn carbonates precipitation until a steady state is reached after 1.5 months. Monitoring changes in nanoparticles physico‐chemical parameters once exposed to synthetic seawater constitutes an important step to predict their fate in environmental systems, with major implications for ecotoxicological studies where metallic speciation is required for toxicity evaluation. Environ Toxicol Chem © 2013 SETAC

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