fulltext.study @t Gmail

Mechanisms of catalytic ozonation on alumina and zeolites in water: Formation of hydroxyl radicals

Paper ID Volume ID Publish Year Pages File Format Full-Text
46127 46430 2012 13 PDF Available
Title
Mechanisms of catalytic ozonation on alumina and zeolites in water: Formation of hydroxyl radicals
Abstract

The mechanisms of catalytic ozonation of coumarin on ZSM-5 zeolites and γ-alumina in water have been studied. Coumarin is known to react with hydroxyl radicals to produce 7-hydroxycoumarin and is used to differentiate between radical and non-radical mechanisms. The effect of the radical scavenger (t-butanol) and phosphates has also been used to study the possible involvement of radicals and the role of surface hydroxyl groups of catalysts. Four ZSM-5 zeolites with varying silica to alumina ratios and with both hydrogen and sodium counter ions were used in the study (Z1000H:SiO2/Al2O3 = 1000, Z900Na:SiO2/Al2O3 = 900, Z25H:SiO2/Al2O3 = 25 and Z25Na:SiO2/Al2O3 = 25). The results show that both alumina and the zeolites catalyse the removal of coumarin from aqueous solution by ozonation, but that alumina is generally more active than zeolites and it catalyses a radical pathway involving hydroxyl radicals, showing its highest activity at pH close to the point of zero charge where surface hydroxyl groups are most susceptible to conversion of ozone to hydroxyl radicals. The zeolites operate through a simple adsorption process, leading to a direct reaction between adsorbed coumarin and adsorbed ozone. Activity depends to an extent on the silica to alumina ratio of the zeolite but is insensitive to the nature of the zeolite counter ion.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights▸ Coumarin was used as probe molecule to investigate OH formation during catalytic ozonation in water. ▸ The ZSM-5 zeolites act mainly as adsorbents of ozone and coumarin and do not generate hydroxyl radicals. ▸ Al2O3/O3 leads to hydroxyl radicals formation due to interaction of ozone with surface hydroxyl groups of alumina.

Keywords
Catalytic ozonation; Water treatment; Coumarin; 7-hydroxycoumarin; ZSM-5 zeolites; Alumina; Mechanism; AOPs; Advanced oxidation processes
First Page Preview
Mechanisms of catalytic ozonation on alumina and zeolites in water: Formation of hydroxyl radicals
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
Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volumes 123–124, 23 July 2012, Pages 94–106
Authors
, , ,
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