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Spatially resolved dissolution and speciation changes of ZnO nanorods during short-term in situ incubation in a simulated wastewater environment

DOI: 10.1021/acsnano.9b02866 DOI Help

Authors: Miguel A. Gomez-gonzalez (Imperial College London) , Mohamed A. Koronfel (Imperial College London) , Angela Erin Goode (Imperial College London) , Maryam Al-ejji (Imperial College London) , Nikolaos Voulvoulis (Imperial College London) , Julia E. Parker (Diamond Light Source) , Paul D. Quinn (Diamond Light Source) , Thomas Bligh Scott (University of Bristol) , Fang Xie (Imperial College London) , Marian L. Yallop (University of Bristol) , Alexandra E. Porter (Imperial College London) , Mary P. Ryan (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Nano

State: Published (Approved)
Published: September 2019
Diamond Proposal Number(s): 17784

Abstract: Zinc oxide engineered nanomaterials (ZnO ENMs) are used in a variety of applications worldwide due to their optoelectronic and antibacterial properties with potential contaminant risk to the environment following their disposal. One of the main potential pathways for ZnO nanomaterials to reach the environment is via urban wastewater treatment plants. So far there is no technique that can provide spatiotemporal nanoscale information about the rates and mechanisms by which the individual nanoparticles transform. Fundamental knowledge of how the surface chemistry of individual particles change, and the heterogeneity of transformations within the system, will reveal the critical physicochemical properties determining environmental damage and deactivation. We applied a methodology based on spatially resolved in situ X-ray fluorescence microscopy (XFM), allowing observation of real-time dissolution and morphological and chemical evolution of synthetic template-grown ZnO nanorods (∼725 nm length, ∼140 nm diameter). Core–shell ZnO-ZnS nanostructures were formed rapidly within 1 h, and significant amounts of ZnS species were generated, with a corresponding depletion of ZnO after 3 h. Diffuse nanoparticles of ZnS, Zn3(PO4)2, and Zn adsorbed to Fe-oxyhydroxides were also imaged in some nonsterically impeded regions after 3 h. The formation of diffuse nanoparticles was affected by ongoing ZnO dissolution (quantified by inductively coupled plasma mass spectrometry) and the humic acid content in the simulated sludge. Complementary ex situ X-ray absorption spectroscopy and scanning electron microscopy confirmed a significant decrease in the ZnO contribution over time. Application of time-resolved XFM enables predictions about the rates at which ZnO nanomaterials transform during their first stages of the wastewater treatment process.

Journal Keywords: ZnO nanomaterials; X-ray fluorescence microscopy; scanning electron microscopy; in situ ZnO dissolution; spatially resolved ZnO transformations

Subject Areas: Chemistry, Materials, Environment


Instruments: I14-Hard X-ray Nanoprobe