Stability of engineered nanomaterials in complex aqueous matrices: Settling behaviour of CeO{sub 2} nanoparticles in natural surface waters
- Laboratory of Analytical Chemistry and Applied Ecochemistry, Department of Applied Analytical and Physical Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Ghent (Belgium)
- Particle and Interfacial Technology Group, Department of Applied Analytical and Physical Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Ghent (Belgium)
The stability of engineered nanoparticles (ENPs) in complex aqueous matrices is a key determinant of their fate and potential toxicity towards the aquatic environment and human health. Metal oxide nanoparticles, such as CeO{sub 2} ENPs, are increasingly being incorporated into a wide range of industrial and commercial applications, which will undoubtedly result in their (unintentional) release into the environment. Hereby, the behaviour and fate of CeO{sub 2} ENPs could potentially serve as model for other nanoparticles that possess similar characteristics. The present study examined the stability and settling of CeO{sub 2} ENPs (7.3±1.4 nm) as well as Ce{sup 3+} ions in 10 distinct natural surface waters during 7 d, under stagnant and isothermal experimental conditions. Natural water samples were collected throughout Flanders (Belgium) and were thoroughly characterized. For the majority of the surface waters, a substantial depletion (>95%) of the initially added CeO{sub 2} ENPs was observed just below the liquid surface of the water samples after 7 d. In all cases, the reduction was considerably higher for CeO{sub 2} ENPs than for Ce{sup 3+} ions (<68%). A first-order kinetics model was able to describe the observed time-dependant removal of both CeO{sub 2} ENPs (R{sup 2}≥0.998) and Ce{sup 3+} ions (R{sup 2}≥0.812) from the water column, at least in case notable sedimentation occurred over time. Solution-pH appeared to be a prime parameter governing nanoparticle colloidal stability. Moreover, the suspended solids (TSS) content also seemed to be an important factor affecting the settling rate and residual fraction of CeO{sub 2} ENPs as well as Ce{sup 3+} ions in natural surface waters. Correlation results also suggest potential association and co-precipitation of CeO{sub 2} ENPs with aluminium- and iron-containing natural colloidal material. The CeO{sub 2} ENPs remained stable in dispersion in surface water characterized by a low pH, ionic strength (IS), and TSS content, indicating the eventual stability and settling behaviour of the nanoparticles was likely determined by a combination of physicochemical parameters. Finally, ionic release from the nanoparticle surface was also examined and appeared to be negligible in all of the tested natural waters. - Highlights: • Solution-pH appeared to be a key factor determining CeO{sub 2} ENPs colloidal stability. • A 1st-order kinetics model could describe the time-dependant settling of CeO{sub 2} ENPs. • Suspended solids content affected the settling rate and residual cerium fraction. • CeO{sub 2} ENPs remained stable in dispersion in water with low pH, IS, and TSS content. • Ionic release from the CeO{sub 2} ENPs appeared negligible in all surface waters.
- OSTI ID:
- 22687692
- Journal Information:
- Environmental Research, Vol. 1542; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0013-9351
- Country of Publication:
- United States
- Language:
- English
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