Sulfidation of sea urchin-like zinc oxide nanospheres: Kinetics, mechanisms, and impacts on growth of Escherichia coli
Date Issued
2020-11-01
Author(s)
Abstract
Nanoscale zinc oxide (n-ZnO) with different morphology and sizes has been used in personal care products due to their antibacterial properties, resulting in discharge of n-ZnO into the environment with potential toxic effect to ecological systems. Sulfidation is one of pathways of transformation of n-ZnO, but a very limited information on the conversion of n-ZnO under sulfidic environment with special morphology such as sea urchin-like zinc oxide nanospheres (ZnO-NSs) is available to know the potential environmental risks of n-ZnO. Herein, sea urchin-like ZnO-NSs with an average size of 78 nm were synthesized and adopted as the model n-ZnO of special morphology. The ZnO-NPs at average sizes of 71 nm (ZnO-NPs-71), 48 nm (ZnO-NPs-48), and 17 nm (ZnO-NPs-17) nm were used to examine possible differences in the sulfidation between the sea urchin-like ZnO-NSs and ZnO-NPs. A new analytical method selectively dissolving ZnO over ZnS in partially sulfidized n-ZnO was developed and applied to understand the kinetics of n-ZnO sulfidation. The sulfidation rate constant (ks) of sea urchin-like ZnO-NSs was 2.9 × 10−3 h−1, comparable to that of ZnO-NPs-71 (4.1 × 10−3 h−1), but much lower than those of ZnO-NPs-48 (20.1 × 10−3 h−1) and ZnO-NPs-17 (67.8 × 10−3 h−1). This might be attributed to the differences in the specific surface area; ks positively correlated with the specific surface area (R2 = 0.97). Natural organic matter (NOM) decreased dissolution and sulfidation of the sea urchin-like ZnO-NSs. Aggregate ZnS nanocrystals instead of the original sea urchin-like ZnO-NSs were observed. We proposed that sea urchin-like ZnO-NSs were transformed to ZnS through a dissolution-precipitation pathway, consistent with the sulfidation pathway of ZnO-NPs. Sulfidation drastically reduced toxicity of sea urchin-like ZnO-NSs to Escherichia coli due to negligible dissolution of ZnS nanocrystals. These results greatly improved our understanding of the transformation and potential risks of n-ZnO with special morphology.
Subjects
Special morphology
;
Sulfidation rate
;
Specific surface area
;
ZnS nanocrystals
;
Escherichia coli
Publisher
Elsevier
Institution
Type
journal article
Journal/Edited collection
ISSN
1879-1026
Band
741
Article ID
140415
Secondary publication
Yes
Document version
Postprint
Language
English
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Qian et al_Sulfidation of sea urchin-like zinc oxide nanospheres_2020_accepted-version .pdf
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