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Kinetics and Mechanism of Reactions between H2O2 and Tungsten Powder
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this work, the reaction between H2O2 and tungsten powder in the presence of Tris(hydroxymethyl) aminomethane was studied experimentally. The production of hydroxyl radicals can be quantified indirectly by quantifying the scavenging product formaldehyde (CH2O). XRD, XPS and SEM analysis shows that no significant structural or compositional changes occur after reaction. We compared H2O2 consumption and CH2O formation in both heterogeneous W(s)/H2O2/Tris system and homogenous W(aq)/H2O2/Tris system. Increasing the amount of W powder leads to the increase in dissolution rate of W species, insignificant increase of H2O2 consumption rate and the decrease of final CH2O production. By contrast, the consumption rate of H2O2 increases as increasing the concentration of dissolved W species. Based on the experimental results, a mechanism of H2O2 reacting with W powder in the presence of Tris is proposed. The mechanism well explained the relationship between surface reactions and homogeneous Haber-Weiss reactions.

National Category
Physical Chemistry
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-172418OAI: oai:DiVA.org:kth-172418DiVA: diva2:847943
Note

QS 2015

Available from: 2015-08-21 Created: 2015-08-21 Last updated: 2015-08-26Bibliographically approved
In thesis
1. Radiation Induced Processes at Solid-Liquid Interfaces
Open this publication in new window or tab >>Radiation Induced Processes at Solid-Liquid Interfaces
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the thesis, the reactions between water radiolysis products—H2O2, HO• and O2—with metals and metal oxides utilized in nuclear industry are studied. The reactions include not only surface reactions, e.g. redox reactions and catalytic decomposition of H2O2, but also solution reactions (Haber-Weiss reactions). To study the interfacial reactions, it is crucial to monitor the dissolution of the solid material, reactivity of H2O2 and formation of the intermediate hydroxyl radicals.Hydroxyl radicals are captured by probe (Tris or methanol) to generate CH2O which can be quantified by the modified Hantzsch method. The results from γ-irradiation experiments on homogeneous system show that the conversion yield of CH2O from hydroxyl radicals is affected by O2 and pH. A mechanism of CH2O production from Tris is proposed.Besides, the consumption rate of H2O2 in the H2O2/ZrO2/Tris system is found to be influenced by Tris. A mechanism for the catalytic decomposition of H2O2 upon ZrO2 surface is proposed which includes independent surface adsorption sites for H2O2 and Tris. Moreover, it is demonstrated that the deviation of detected CH2O concentration by the modified Hantzsch method from actual concentration increases with increasing [H2O2]0/[CH2O]0.The inhibition of sulfide on the radiation induced dissolution of UO2 is confirmed and is dependent on sulfide concentration. And the inhibition of sulfide is independent to that of H2/Pd.It is found that the reactivity of H2O2 and dynamics of CH2O formation are different for the studied materials in the H2O2/MxOy/Probe system. The kinetic parameters, such as rate constant, activation energy, frequency factors are determined.Both surface and solution reactions are observed in the aqueous W(s)/H2O2/Tris system. It is also demonstrated that Haber-Weiss reactions which produce HO• continuously are dominating. Furthermore, it is found that hydroxyl radicals are formed simultaneously during the dissolution of W in aerobic aqueous system.The knowledge conveyed by the thesis is relevant to nuclear technological applications, as well as the applications related in photocatalysis, biochemistry, corrosion science, catalysis and optics/electronics.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xii, 74 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:39
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-172421 (URN)978-91-7595-656-5 (ISBN)
Public defence
2015-09-18, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150826

Available from: 2015-08-26 Created: 2015-08-21 Last updated: 2015-08-26Bibliographically approved

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