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Effects of inorganic oxidants on kinetics and mechanisms of WO3-mediated photocatalytic degradation

Paper ID Volume ID Publish Year Pages File Format Full-Text
45674 46418 2015 9 PDF Available
Title
Effects of inorganic oxidants on kinetics and mechanisms of WO3-mediated photocatalytic degradation
Abstract

•Impact of various inorganic oxidants on WO3 photocatalytic activity is evaluated.•Combination with periodate drastically accelerates photocatalyzed oxidation by WO3.•The effects of reaction parameters on kinetic enhancements are examined.•Oxyanions promote charge separation and enable the formation of secondary oxidants.•Surface platinization improves the electron accepting capacity of selected oxyanions.

This study evaluates the capacity of various inorganic oxidants (IO4−, HSO5−, S2O82−, H2O2, and BrO3−) to act as alternative electron acceptors for WO3-mediated photocatalytic oxidation. Combination with IO4− drastically increased the rate of photocatalytic degradation of 4-chlorophenol by WO3, while the other oxyanions only negligibly improved the photocatalytic activity. The extent of the photocatalytic performance enhancement in the presence of inorganic oxidants correlated well with the efficiencies for: (1) hydroxylation of benzoic acid as an OH probe, (2) dechlorination of dichloroaceate as a hole scavenger, and (3) water oxidation with O2 evolution. The results suggest that the promoted charge separation primarily causes kinetic enhancement in photocatalytic degradation using the WO3/IO4− system. In marked contrast to the substrate-dependent activity of the photochemically activated IO4− (generating selective IO3), the efficiency of the WO3/IO4− system for photocatalytic degradation did not sensitively depend on the type of target organic compound, which implies the existence of a minor contribution of the photocatalytic reduction pathway associated with the production of IO3 as a secondary oxidant. On the other hand, the insignificant inhibitory effect of methanol as an OH quencher may reveal the possible involvement of SO4− in the improved photocatalytic activity of the WO3/HSO5− system. The alternative use of platinized WO3, where the interfacial electron transfer occurs in a concerted step, achieved a highly accelerated photocatalytic oxidation in the presence of HSO5− and polyoxometalates as electron scavengers. In particular, the surface loading of nanoscale platinum appeared to retard the reaction route for SO4− generation associated with a one-electron transfer.

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Keywords
CB, conduction band; DCA, dichloroacetic acid; EDS, energy dispersive X-ray spectrometer; IEP, isoelectric point; POM, polyoxometalate; TCD, thermal conductivity detector; VB, valence bandPhotocatalytic oxidation; Inorganic oxidant; Alternative electron a
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Effects of inorganic oxidants on kinetics and mechanisms of WO3-mediated photocatalytic degradation
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 162, January 2015, Pages 515–523
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