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Transformation products and reaction kinetics in simulated solar light photocatalytic degradation of propranolol using Ce-doped TiO2

Paper ID Volume ID Publish Year Pages File Format Full-Text
45979 46428 2013 17 PDF Available
Title
Transformation products and reaction kinetics in simulated solar light photocatalytic degradation of propranolol using Ce-doped TiO2
Abstract

The visible light photocatalytic degradation of propranolol was studied using cerium doped titanium dioxide, a catalyst that showed an increased light absorption in the visible region. The experiments were carried out in ultrapure water and in a biologically treated wastewater from the secondary effluent of a treatment plant spiked with propranolol. The best results were obtained for a cerium loading of 0.5 wt.% and a bulk catalyst concentration of 0.14 g/L, with which propranolol became essentially depleted after 1.5 h of irradiation. The extent of mineralization reached 17.4% after 6 h on stream under the same conditions. Both oxidation on catalyst holes and reaction with hydroxyl radicals contribute to propranolol depletion, but for the reaction conditions tested in this study, the first mechanism predominated and accounted for 60% of the propranolol rate constant. The runs performed in wastewater matrix led to a very low photocatalytic rate compared with pure water, which was attributed to the presence of radical scavengers and competing substances. Over thirty reaction intermediates were detected by means of exact mass measurements performed by liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (LC-ESI-QTOF–MS/MS) based on the characteristic fragmentation of oxidation by-products. Their relative abundance was also assessed in catalytic and non-catalytic runs. The most abundant transformation products could be attributed to the cleavage of the ether bond of propranolol. Other compounds detected derived from the addition of hydroxyl groups to the aromatic nuclei or to the ring-opening attack of hydroxyl radicals on the naphthol moiety. Finally, the toxicity of oxidized mixtures was determined using the green algae Pseudokirchneriella subcapitata and the bioluminescent marine bacterium Vibrio fischeri. Although the toxicity of treated mixtures tended to decrease as propranolol was depleted, mixtures treated in pure water may lead to the accumulation of toxic transformation products.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We studied the visible-light photocatalytic degradation of propranolol. ► We used cerium-doped titanium dioxide as photocatalyst. ► Oxidation through catalyst holes was the prevailing mechanism. ► We detected over thirty transformation products using LC-ESI-QTOF–MS/MS. ► Toxic transformation products accumulated, displaying toxicity to microorganisms.

Keywords
Propranolol; Solar photocatalysis; Transformation products; Liquid chromatography; Mass spectrometry
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Transformation products and reaction kinetics in simulated solar light photocatalytic degradation of propranolol using Ce-doped TiO2
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 129, 17 January 2013, Pages 13–29
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