Removal of metronidazole by TiO2 and ZnO photocatalysis: a comprehensive comparison of process optimization and transformation products

The photodegradation of antibiotic metronidazole (MNZ) was systematically studied and compared by using aqueous suspensions of TiO 2 and ZnO catalysts under 100-W UV irradiation. The degradation conditions were optimized using the central composite design and response surface methodology. The optima...

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Bibliographic Details
Published in:Environmental science and pollution research international 2018-10, Vol.25 (28), p.28285-28295
Main Authors: Tran, Mai Lien, Fu, Chun-Chieh, Juang, Ruey-Shin
Format: Article
Language:English
Subjects:
Antibiotics
Aquatic Pollution
Atmospheric Protection/Air Quality Control/Air Pollution
Catalysis
Catalysts
Design optimization
Earth and Environmental Science
Ecotoxicology
Environment
Environmental Chemistry
Environmental Health
Environmental science
Free radicals
Genetic transformation
Hydroxyl radicals
Intermediates
Irradiation
Metronidazole
Oxidation
pH effects
Photocatalysis
Photodegradation
Research Article
Response surface methodology
Superoxide
Titanium dioxide
Ultraviolet radiation
Waste Water Technology
Water Management
Water Pollution Control
Zinc oxide
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Summary:The photodegradation of antibiotic metronidazole (MNZ) was systematically studied and compared by using aqueous suspensions of TiO 2 and ZnO catalysts under 100-W UV irradiation. The degradation conditions were optimized using the central composite design and response surface methodology. The optimal photodegradation conditions obtained were at pH 6.0 with 1.5 g L −1 of TiO 2 (86.10% removal for 50 mg L −1 MNZ) and at pH 9.5 with 0.5 g L −1 of ZnO (60.32% removal for 30 mg L −1 MNZ) after 60-min irradiation at 20 °C. The degradation efficiency in the presence of TiO 2 was higher than that of ZnO. The participation of active species such as hydroxyl radicals (OH·), holes (h + ), and superoxide radicals (O 2 − ·) during MNZ photodegradation over TiO 2 and ZnO catalysts was also examined. Experimental results showed that MNZ oxidation was mainly driven by the presence of holes and superoxide radicals. Totally, 10 major intermediates were detected in UV/TiO 2 and UV/ZnO photocatalysis of MNZ using LC-QTof/MS system, in which 5 same intermediates were found. The remaining different intermediates led to the variations of degradation pathways of both processes. Moreover, some bigger transformation products than the parent MNZ were detected.
ISSN:0944-1344
1614-7499
DOI:10.1007/s11356-018-2848-7