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Photocatalytic bleaching of aqueous malachite green solutions by UV-A and blue-light-illuminated TiO2 spherical nanoparticles modified with tungstophosphoric acid

Paper ID Volume ID Publish Year Pages File Format Full-Text
46581 46442 2011 7 PDF Available
Title
Photocatalytic bleaching of aqueous malachite green solutions by UV-A and blue-light-illuminated TiO2 spherical nanoparticles modified with tungstophosphoric acid
Abstract

Visible-light-responsive spherical TiO2 particles were prepared by the sol–gel method by adding urea as pore-forming agent and tungstophosphoric acid (TPA) in different ratios (20% and 30% w/w) and by annealing at 500 °C for 2 h. Visible light absorption is probably due to WOx formation (i.e. WO3) resulting from the partial degradation of TPA and evidenced by XPS spectra. Besides, 31P NMR and XPS results showed evidence about the existence of mostly unaltered TPA within TiO2 nanoparticles and on their surface, together with lacunar or dimeric species. TPA addition not only affected the optical properties of materials but also produced a strong decrease of their point of zero charge (pHpzc). Results obtained under UV-A irradiation revealed that aqueous malachite green (MG) solutions were efficiently bleached through the oxidative process of N-demethylation being the TiO2 powder containing 30% (w/w) of TPA (TiO2–TPA–30%) (100% of bleaching in 60 min) the most active even than Degussa P-25 (80% of MG bleaching in 60 min). On the other hand, when blue-light irradiation was used, TiO2–TPA–30% powder also revealed the highest photocatalytic bleaching of MG solutions which, as in the case of UV-A light irradiation experiments, was oxidized through N-demethylation processes. Finally, experiments carried out using blue-light irradiation under N2 atmosphere showed that aqueous MG solutions were not bleached by TiO2 powders containing TPA.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Vis-light-responsive TiO2 modified with tungstophosphoric acid (TPA) was obtained. ► TPA and their lacunar and dimeric phases were detected on TPA–TiO2 materials. ► Presence of WOx species on TPA–TiO2 could be responsible of Vis-light absorption. ► Irradiated TPA–TiO2 bleached efficiently malachite green (MG) solutions. ► MG underwent N-demethylation induced by UV and blue-light irradiated TPA–TiO2.

Keywords
Heterogeneous TiO2 photocatalysis; Tungstophosphoric acid; Malachite green; Visible light responsive TiO2
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Photocatalytic bleaching of aqueous malachite green solutions by UV-A and blue-light-illuminated TiO2 spherical nanoparticles modified with tungstophosphoric acid
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 110, 2 November 2011, Pages 126–132
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