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Role of pH on photolytic and photocatalytic degradation of antibiotic oxytetracycline in aqueous solution under visible/solar light: Kinetics and mechanism studies

Paper ID Volume ID Publish Year Pages File Format Full-Text
45771 46422 2013 10 PDF Available
Title
Role of pH on photolytic and photocatalytic degradation of antibiotic oxytetracycline in aqueous solution under visible/solar light: Kinetics and mechanism studies
Abstract

In this study, the photochemical degradation of the antibiotic oxytetracycline (OTC) at different pH values was investigated in aqueous solution under visible and solar light irradiation. Particular emphasis was given to the kinetics and mechanism during the photolytic and photocatalytic degradation of OTC. A comparative study of the photolysis of OTC under solar light, with different initial concentrations and in the presence of scavengers of reactive oxygen species (ROS), revealed a self-photosensitization pathway with evidence of singlet oxygen generation at pH 8.5 and 11.0 during OTC photolysis. The three-dimensional fluorescence spectra of OTC at different pH values demonstrate that OTC only exhibits significant emission spectra at pH 8.5 and 11.0. The change of the internal electrostatic force between the electron withdrawing group and the dehydrogenation moiety of OTC as a function of solution pH values was proposed as a critical factor influencing the energy states and observed reaction pathways of OTC under light irradiation. Moreover, the mechanism of photochemical degradation of OTC was investigated with nitrogen and fluorine doped titanium dioxide (NF-TiO2) film at different pH values under visible and solar light in the presence of tert-butyl alcohol (TBA), sodium azide (NaN3), potassium iodine (KI) and catalase as scavengers. Five pathways, including direct photolytic degradation, UV/vis light-induced photocatalytic oxidation and reduction, and visible light-induced self-photosensitized oxidation and reduction, were proposed and verified during the photocatalytic degradation of OTC with NF-TiO2 film.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The photolytic and photocatalytic degradation of oxytetracycline was investigated. ► A self-photosensitization path was found at pH 8.5 and 11.0 during OTC photolysis. ► Only OTC at pH 8.5 and 11.0 had emission spectra by photo excitation. ► The internal electrostatic force of OTC was proposed as the critical mechanism. ► Five pathways were verified during the photocatalytic degradation of OTC.

Keywords
Titanium dioxide; Fluorine doping; Nitrogen doping; Oxytetracycline; Photocatalysis; Photosensitization; Solar light; Visible light
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Role of pH on photolytic and photocatalytic degradation of antibiotic oxytetracycline in aqueous solution under visible/solar light: Kinetics and mechanism studies
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volumes 134–135, 2 May 2013, Pages 83–92
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us