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Photocatalytic Treatment of Cork Wastewater Pollutants. Degradation of Gallic Acid and Trichloroanisole using Triphenyl(thia)pyrylium salts

Paper ID Volume ID Publish Year Pages File Format Full-Text
45473 46412 2015 6 PDF Available
Title
Photocatalytic Treatment of Cork Wastewater Pollutants. Degradation of Gallic Acid and Trichloroanisole using Triphenyl(thia)pyrylium salts
Abstract

•Triphenyl(thia) pyrylium salts photocatalyze degradation of cork pollutants.•Gallic acid is photooxidized faster than 2,4,6-tricloroanisole.•Formation of photocatalyst-pollutant ground state complexes has been proven.•Involvement of singlet excited state of photocatalysts is ruled out.•Electron transfer to triplet state is the main reaction pathway for gallic acid.

The photocatalytic degradation of two typical pollutants present at the wastewaters of cork industry, namely gallic acid (GA) and 2,4,6-trichloroanisole (TCA) has been investigated using triphenylpyrylium (TPP+) and triphenylthiapyrylium (TPTP+) salts as organic photocatalysts. Fast removal of GA and slow but efficient degradation of the reluctant TCA were observed. The role of the transient species involved in the photodegradation has been investigated by means of photophysical experiments. Participation of singlet excited states was safely disregarded since lifetimes of both photocatalysts remained invariable upon addition of GA or TCA. Formation of photoactive ground state complexes was observed, and the complexation constants were estimated as KTPP-GA = 468.4 M−1, KTPP-TCA = 528.0 M−1 and KTPTP-TCA = 657.1 M−1. Moreover participation of the triplet excited states in the electron transfer oxidation of GA was very efficient, while no reaction occurred from the triplet excited states in the case of TCA. In addition, thermodynamic calculations support the participation of the triplet excited state in the case of GA, while the lack of triplet quenching in the case of TCA is associated with a thermodynamically disfavored process. Overall, photophysical experiments indicate that for GA, oxidative electron transfer occurs mainly from the triplet excited state with marginal contribution of the ground state complexes, while for TCA formation of ground state complexes constitutes the only mechanistic pathway.

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Keywords
Complex formation; Electron transfer; Photocatalytic degradation; Laser flash photolysis; Triplet excited state
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Photocatalytic Treatment of Cork Wastewater Pollutants. Degradation of Gallic Acid and Trichloroanisole using Triphenyl(thia)pyrylium salts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 179, December 2015, Pages 433–438
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