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Radiation Induced Processes at Solid-Liquid Interfaces
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. (Nuclear Chemistry)
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: urn:nbn:se:kth:diva-172421ISBN: 978-91-7595-656-5 (print)OAI: oai:DiVA.org:kth-172421DiVA: diva2:847948
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
List of papers
1. Inhibition of radiation induced dissolution of UO2 by sulfide-A comparison with the hydrogen effect
Open this publication in new window or tab >>Inhibition of radiation induced dissolution of UO2 by sulfide-A comparison with the hydrogen effect
2013 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 434, no 1-3, 38-42 p.Article in journal (Refereed) Published
Abstract [en]

In this work we have studied the influence of H2S on radiation induced dissolution of spent nuclear fuel using simple model systems. The reaction between H2O2 and H2S/HS- has been studied experimentally as well as the effect of H2S/HS - on γ-radiation induced dissolution of a UO2 pellet. The experiments clearly show that the reaction of H2O 2 and H2S/HS- is fairly rapid and that H 2O2 and H2S/HS- stoichiometry is favorable for inhibition. Radiolysis experiments show that H2S/ HS- can effectively protect UO2 from oxidative dissolution. The effect depends on sulfide concentration in combination with dose rate. Autoclave experiments were also conducted to study the role of H 2S/HS- in the reduction of U(VI) in the presence and absence of H2 and Pd particles in anoxic aqueous solution. The aqueous solutions were pressurized with H2 or N2 and two different concentrations of H2S/HS- were used in the presence and absence of Pd. No catalytic effect of Pd on the U(VI) reduction by H2S/HS- could be found in N2 atmosphere. U(VI) reduction was found to be proportional to H2S/HS- concentration in H2 and N2 atmosphere. It is clearly shown the Pd catalyzed H2 effect is more powerful than the effect of H2S/HS-. H2S/HS- poisoning of the Pd catalyst is not observed under the present conditions.

Keyword
Anoxic aqueous solutions, Autoclave experiments, Catalytic effects, Dose rate, Hydrogen effect, Model system, Oxidative dissolution, Pd catalyst, Pd particle, Radiation-induced, Spent nuclear fuels, Sulfide concentration, Experiments, Hydrogen, Radiation chemistry, Radioactive wastes, Solutions, Stoichiometry, Dissolution
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-118121 (URN)10.1016/j.jnucmat.2012.10.050 (DOI)000315752000006 ()2-s2.0-84871742513 (Scopus ID)
Note

QC 20130212

Available from: 2013-02-12 Created: 2013-02-12 Last updated: 2017-04-21Bibliographically approved
2. Catalytic decomposition of hydrogen peroxide on transition metal and lanthanide oxides
Open this publication in new window or tab >>Catalytic decomposition of hydrogen peroxide on transition metal and lanthanide oxides
2013 (English)In: Journal of Molecular Catalysis A: Chemical, ISSN 1381-1169, E-ISSN 1873-314X, Vol. 379, 178-184 p.Article in journal (Refereed) Published
Abstract [en]

We have investigated the reactions of H2O2 with Fe2O3, CuO, HfO2, CeO2 and Gd 2O3 in aqueous solution. The reactions rate constants at room temperature were determined. From the temperature dependence of the rate constants we extracted the Arrhenius parameters and the standard enthalpies of activation for the reactions. In addition, we studied the dynamics of formation of the intermediate species formed during decomposition of H2O 2, the HO radical. The kinetic data for H2O2 reactivity and the yields of hydroxyl radical formation differ considerably between many of the materials studied. We compared the energetic and mechanistic data obtained in this work with literature data for a set of nine oxides in total. The Arrhenius pre-exponential factors normalized to surface area for the decomposition of H2O2 vary by nine orders of magnitude for some of the oxides investigated. This indicates that the surfaces of the oxides have very different catalytic capacity towards the decomposition of H 2O2. The standard enthalpies of activation for H 2O2 decomposition vary between 30 and 73 kJ mol -1, revealing also differences in the catalytic efficiency for the different materials. The mechanistic study consists of quantifying the HO radical scavenged by tris(hydroxymethyl)aminomethane (Tris) during the course of the decomposition of H2O2 for the whole set of oxides. The yields and dynamics of scavenging of HO• differ considerably between the oxides analyzed. Surprisingly, the time-independent plots of the amount of HO scavenged as a function of the conversion of H2O 2 reveals that during the decomposition of H2O2 there are turnover points where the amount of HO scavenged by Tris suffers a sudden increase. The location of these points and the curvatures of the plots at the near-neighbours is considerably different for the different materials.

Keyword
Catalysis, Hydroxyl, Oxide, Peroxide, Surface
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-119808 (URN)10.1016/j.molcata.2013.08.017 (DOI)000326772700024 ()2-s2.0-84884191958 (Scopus ID)
Note

QC 20131029

Available from: 2013-03-22 Created: 2013-03-22 Last updated: 2017-12-06Bibliographically approved
3. Evaluation of the O-2 and pH Effects on Probes for Surface Bound Hydroxyl Radicals
Open this publication in new window or tab >>Evaluation of the O-2 and pH Effects on Probes for Surface Bound Hydroxyl Radicals
2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 15, 7971-7979 p.Article in journal (Refereed) Published
Abstract [en]

Interfacial reactions between H2O2 and metal oxides are important in several fields but are yet not fully understood. Recently, tris(hydroxymethyl)aminomethane (Tris) was used as a probe in detecting the intermediate hydroxyl radical (HO center dot) during such process via the formation of formaldehyde (CH2O). In this work, we evaluate two probes (methanol and Tris) for detection of surface bound HO center dot by investigating the O-2 and pH effects on the production of formaldehyde. Moreover, we also examine the pH effect on the production of formaldehyde from Tris in the catalytic decomposition of H2O2 on ZrO2. The influence of O-2 and pH on the yield of formaldehyde under homogeneous conditions was studied via gamma-radiolysis of water. The solution was either deoxygenated or saturated with gas containing 20% 02, and the pH was ranging from 7.0 to 9.0. In the gamma-radiolysis experiment, O-2 shows a strong impact on the yield of formaldehyde: 14-68% for methanol and 16-29% for Tris. However, during the catalytic decomposition of H2O2, O-2 only enables a 30% enhancement of the production of CH2O when using Tris as the scavenger. While for methanol, the O-2 effect is almost negligible, and the production of CH2O from Tris is much higher than that from methanol. For practical reasons, only Tris was studied when evaluating the pH effect. A significant increase in the production of formaldehyde is observed by increasing pH during gamma-radiolysis of water while an even more pronounced pH-dependent increase is observed in the catalytic decomposition of H2O2 on ZrO2. The former indicates that the scavenging yield is base-catalyzed while the latter indicates that the formation of HO center dot is also base-catalyzed. On the basis of the observed effects of O-2 and pH, we propose a mechanism for the production of formaldehyde from Tris. The mechanism accounts for the observed impacts of O-2 and pH on the yield of formaldehyde.

Keyword
Catalysis, Methanol, Petroleum tar, pH effects, Probes, Radiation chemistry, Radiolysis, Scavenging, Zirconium alloys, Catalytic decomposition, Homogeneous conditions, Hydroxyl radicals, Metal oxides, PH-dependent, Radiolysis of waters, Surface bounds, Trishydroxymethylaminomethane
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-145580 (URN)10.1021/jp412571p (DOI)000334730300025 ()2-s2.0-84898997402 (Scopus ID)
Note

QC 20140611

Available from: 2014-06-11 Created: 2014-05-23 Last updated: 2017-12-05Bibliographically approved
4. Surface reactivity of hydroxyl radicals formed upon catalytic decomposition of H2O2 on ZrO2
Open this publication in new window or tab >>Surface reactivity of hydroxyl radicals formed upon catalytic decomposition of H2O2 on ZrO2
2015 (English)In: Journal of Molecular Catalysis A: Chemical, ISSN 1381-1169, E-ISSN 1873-314X, Vol. 400, 49-55 p.Article in journal (Refereed) Published
Abstract [en]

In this work, the surface reactivity of hydroxyl radicals formed upon catalytic decomposition of H2O2 on ZrO2 in the presence of Tris(hydroxymethyl) aminomethane was studied experimentally. Two sets of competition experiments were performed: the competition between H2O2 and Tris for the surface bound hydroxyl radical (HO) and between O2 and H2O2 for the hydroxymethyl radical (CH2OH) (precursor for formaldehyde). A 5-fold increase in initial concentration of Tris or H2O2 does not lead to a 5-fold increase in CH2O formation (only by a factor of 2-3 in the studied concentration range). The O2-dependent enhancement of the final production of CH2O becomes weaker upon increasing the initial concentration of H2O2 from 0.5 mM to 5 mM. The final production of CH2O becomes independent of the concentration of Tris when [Tris]0 is above 100 mM, i.e., the surface is saturated with Tris at this concentration. Based on the experimental results, a site-specific mechanism of H2O2 decomposition on the surface of ZrO2 was proposed. This model was used for numerical simulations of the dynamics of the reaction system. The kinetics was simulated using the kinetic simulation software Gepasi 3.0 and the results are in good agreement with the experimental observations.

Keyword
Catalysis, Hydrogen peroxide, Hydroxyl radical, Oxide, Surface, Computer software, Methanol, Oxides, Surfaces, Catalytic decomposition, Concentration ranges, Hydroxyl radicals, Initial concentration, Kinetic simulation, Reaction system, Surface reactivity, Trishydroxymethylaminomethane, Zirconium alloys
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-167732 (URN)10.1016/j.molcata.2015.02.002 (DOI)000353248000007 ()2-s2.0-84922771691 (Scopus ID)
Note

QC 20150601

Available from: 2015-06-01 Created: 2015-05-22 Last updated: 2017-12-04Bibliographically approved
5. Kinetics and Mechanism of Reactions between H2O2 and Tungsten Powder
Open this publication in new window or tab >>Kinetics and Mechanism of Reactions between H2O2 and Tungsten Powder
Show others...
(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:nbn:se:kth:diva-172418 (URN)
Note

QS 2015

Available from: 2015-08-21 Created: 2015-08-21 Last updated: 2015-08-26Bibliographically approved
6. Influence of H2O2 on the Quantitative Determination of Formaldehyde using Acetoacetanilide as Detection Reagent in the Hantzsch Method
Open this publication in new window or tab >>Influence of H2O2 on the Quantitative Determination of Formaldehyde using Acetoacetanilide as Detection Reagent in the Hantzsch Method
(English)Manuscript (preprint) (Other academic)
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:kth:diva-172419 (URN)
Note

NQC 2015

Available from: 2015-08-21 Created: 2015-08-21 Last updated: 2015-08-26Bibliographically approved
7. Hydroxyl Radical Production in Aerobic Aqueous Solution containing Metallic Tungsten
Open this publication in new window or tab >>Hydroxyl Radical Production in Aerobic Aqueous Solution containing Metallic Tungsten
(English)Manuscript (preprint) (Other academic)
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-172420 (URN)
Note

NQC 2015

Available from: 2015-08-21 Created: 2015-08-21 Last updated: 2015-08-26Bibliographically approved
8. Kinetics and mechanisms of reactions between H2O2 and copper and copper oxides
Open this publication in new window or tab >>Kinetics and mechanisms of reactions between H2O2 and copper and copper oxides
Show others...
2015 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, no 36, 16045-16051 p.Article in journal (Refereed) Published
Abstract [en]

One of the main challenges for the nuclear power industry today is the disposal of spent nuclear fuel. One of the most developed methods for its long term storage is the Swedish KBS-3 concept where the spent fuel is sealed inside copper canisters and placed 500 meters down in the bedrock. Gamma radiation will penetrate the canisters and be absorbed by groundwater thereby creating oxidative radiolysis products such as hydrogen peroxide (H2O2) and hydroxyl radicals (HO[radical dot]). Both H2O2 and HO[radical dot] are able to initiate corrosion of the copper canisters. In this work the kinetics and mechanism of reactions between the stable radiolysis product, H2O2, and copper and copper oxides were studied. Also the dissolution of copper into solution after reaction with H2O2 was monitored by ICP-OES. The experiments show that both H2O2 and HO[radical dot] are present in the systems with copper and copper oxides. Nevertheless, these species do not appear to influence the dissolution of copper to the same extent as observed in recent studies in irradiated systems. This strongly suggests that aqueous radiolysis can only account for a very minor part of the observed radiation induced corrosion of copper.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-172417 (URN)10.1039/C5DT02024G (DOI)000360471000033 ()2-s2.0-84940774487 (Scopus ID)
Note

QC 20150929. Updated from e-pub ahead of print to published.

Available from: 2015-08-21 Created: 2015-08-21 Last updated: 2017-12-04Bibliographically approved

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