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A comparative study of the activity of TiO2 Wackherr and Degussa P25 in the photocatalytic degradation of picloram

Paper ID Volume ID Publish Year Pages File Format Full-Text
46807 46449 2011 8 PDF Available
Title
A comparative study of the activity of TiO2 Wackherr and Degussa P25 in the photocatalytic degradation of picloram
Abstract

A comparative study was carried out of the efficiency of titanium dioxide specimens Wackherr and Degussa P25 toward the photocatalytic degradation of picloram, a widely used herbicide. The study encompassed transformation kinetics and efficiency, identification of intermediates and reaction pathways. In the investigated range of initial concentrations (0.25–1.0 mM), the photocatalytic degradation of picloram in the first stage of the reaction followed approximately a pseudo-first order kinetics. The TiO2 Wackherr induced significantly faster picloram degradation than TiO2 Degussa P25 when high photocatalyst loadings and high substrate concentrations were used. By examining the effect of ethanol as a hydroxyl radical scavenger, it was shown that the photocatalytic degradation of picloram takes place mainly via the hydroxyl radicals, while the valence-band holes play a less important role. Total organic carbon analysis showed that complete mineralization of picloram occurred after about 16 h of irradiation. Several degradation intermediates were identified by using LC–MS, GC–MS, and 1H NMR, which allowed the proposal of a tentative pathway for the photocatalytic transformation of picloram. Finally, the photocatalytic degradation rates of three selected herbicides (picloram, triclopyr and mecoprop) were compared, and the results show that the efficiency of photocatalytic degradation is greatly influenced by the molecular structure.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Kinetics and efficiency of photocatalytic degradation of the pesticide picloram. ► Two TiO2 specimens employed and most important operational parameters studied. ► Faster degradation obtained with the TiO2 specimen of the lower surface area. ► Results suggest the importance of other factors (optical properties and back reactions). ► Photocatalytic transformation pathways of picloram including mineralization.

Keywords
Picloram; Herbicide; Photocatalysis; Titanium dioxide; Photocatalytic degradation pathways
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A comparative study of the activity of TiO2 Wackherr and Degussa P25 in the photocatalytic degradation of picloram
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 105, Issues 1–2, 9 June 2011, Pages 191–198
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