Reactions of hydroxyl radicals with hydrogen peroxide at ambient and elevated temperatures

Christensen, H.; Sehested, Κ.; Corfitzen, Hanne

doi:10.1021/j100206a023

Cited by 454 publications

(162 citation statements)

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“…and [22] are scavenged to form a reducing radical that can then reduce the uranyl ions back to a lower oxidation state by reactions [lo] or [16] followed by [7]. Furthermore, the results when 0.46-' rnol L tert-butanol was added to rnol L-' uranium(IV), rnol L-hydrogen peroxide solution at pH 0.7 are also consistent with the mechanisms [l 11, [22], [23], and [7]. In this case, approximately two molecules of peroxide were consumed for every uranium(1V) lost (Fig.…”

Section: Proposed Mechanismsupporting

confidence: 74%

“…Our results at pH 0.7 can be understood in terms of the free-radical chain sequence originally proposed by Baker and Newton (20) (reactions [ l l ] , [22], [19], [23], [7]) and the additional reactions [24]- [26]. In these reactions, U(V1) can either be the ion pair, U S O~~' , or U4+ but not the hydrolysed form UOH3+.…”

Section: Proposed Mechanismmentioning

confidence: 99%

“…In these reactions, U(V1) can either be the ion pair, U S O~~' , or U4+ but not the hydrolysed form UOH3+. [24] OH + H202 + 0 0 H + H20 k2, = 2.7 X 10' L mol-' s-' (23) [25] OOH + OOH -+ H202 + 0, 2k2, = 8.6 x lo5 L mol-' s-I (24) [26] U(IV) + OOH + U O ,~+ + OH Reactions [24]- [26] would explain the stoichiometry observed in Fig. 5.…”

Section: Proposed Mechanismmentioning

confidence: 99%

“…The termination reactions are given by reactions [23] and [7]. Summing reactions [3 11-[33], the overall equation [34] is arrived at, where both atoms in the molecular oxygen are incorporated into different uranyl ions.…”

Section: Initiationmentioning

confidence: 99%

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Free-radical redox reactions of uranium ions in sulphuric acid solutions

Elliot¹,

Padamshi²,

Pika³

1986

Can. J. Chem.

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A. JOHN ELLIOT, SHAHSULTAN PADAMSHI, and JANA PIKA. Can. J. Chem. 64, 314 (1986).The radiolytic reductio? of uranyl ions in degassed sulphuric acid solutions containing various organic solutes was studied. It was shown that while COOH, C02-, and a-hydroxy-alkyl radicals reduced uranyl ions, the P-hydroxy-alkyl radicals and those derived from gluconic acid could not affect the reduction. The oxidation of uranium(1V) by hydrogen peroxide at pH 0.7 involves hydroxyl radicals in a chain mechanism but at pH 2.0 the oxidation proceeds by a non-radical reaction pathway. From the enhancement of the rate of oxidation of uranium(1V) by oxygen in the presence of 2-propanol, a mechanism involving the perhydroxyl radical, which reconciles earlier published data on kinetics and oxygen tracer studies, is proposed for the oxygenuranium(1V) reactions.A. JOHN ELLIOT, SHAHSULTAN PADAMSHI et JANA PIKA. Can. J. Chem. 64, 314 (1986). On Ctudie la reduction radiolytique des ions uranyles dans des solutions dCgazCes d'acide sulfurique contenant divers solutks organiques. On montre que, contrairement aux radicaux COOH, COz-et a-hydroxy-alkyles qui rCduisent les ions uranyles, les radicaux P-hydroxy-alkyles et ceux provenant de l'acide gluconique ne peuvent effectuer la rkduction. L'oxydation de I'uranium(1V) par le peroxyde d'hydrogtne i un pH de 0,7 fait intervenir des radicaux hydroxyles dans un mCcanisme en chaine; toutefois, i un pH de 2,0, la rCaction d'oxydation s'effectue par une voie non-radicalaire. En se basant sur le fait que la vitesse d'oxydation de l'uranium(1V) par l'oxygtne est plus grande en presence de propanol-2, on propose pour cette rCaction un mCcanisme qui implique le radical perhydroxyle. Ce mkcanisme permet de concilier les donntes publites anttrieurement tant sur la cinCtique que sur les Ctudes par marqueurs d'ox>g' ene.[Traduit par le journal]

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Section: Proposed Mechanismsupporting

confidence: 74%

Section: Proposed Mechanismmentioning

confidence: 99%

Section: Proposed Mechanismmentioning

confidence: 99%

Section: Initiationmentioning

confidence: 99%

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Free-radical redox reactions of uranium ions in sulphuric acid solutions

Elliot¹,

Padamshi²,

Pika³

1986

Can. J. Chem.

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“…where R •OH is the formation rate of • OH in equation (1) The second-order rate constant values k 2 , k 3 and k 4 were taken from the literature (Buxton et al, 1988;Christensen et al 1982). The fit of the rate data of Figure 3 with equation (7) yielded k 3 = (1.87±0.31)⋅10 10 M −1 s −1 at pH 4 and (8.46±0.24)⋅10 9 M −1 s −1 at pH 10.…”

Section: Reaction With • Ohmentioning

confidence: 99%

Photochemical processes involving the UV absorber benzophenone-4 (2-hydroxy-4-methoxybenzophenone-5-sulphonic acid) in aqueous solution: Reaction pathways and implications for surface waters

et al. 2013

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processes involving the UV absorber benzophenone-4 (2-hydroxy-4-methoxybenzophenone-5-sulphonic acid) in aqueous solution. Reaction pathways and implications for surface waters. Wat. Res. 2013, 47, 5943-5953. DOI: 10.1016/j.waters.2013 You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions:(1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license.(2) The integrity of the work and identification of the author, copyright owner, and publisher must be preserved in any copy. AbstractThe sunlight filter benzophenone-4 (BP-4) is present in surface waters as two prevailing forms, the singly deprotonated (HA − ) and the doubly deprotonated one (A 2− ), with pK a2 = 7.30±0.14 (µ±σ, by dissociation of the phenolic group). In freshwater environments, BP-4 would mainly undergo degradation by reaction with • OH and direct photolysis. The form HA − has a second-order reaction rate constant with • OH ( OH k • ) of (1.87±0.31)⋅10 10 M −1 s −1 and direct photolysis quantum yield Φ equal to (3.2±0.6)⋅10 −5 . The form A 2− has (8.46±0.24)⋅10 9 M −1 s −1 as the reaction rate constant with • OH and (7.0±1.3)⋅10 −5 as the photolysis quantum yield. The direct photolysis of HA − likely proceeds via homolytic breaking of the O-H bond of the phenolic group to give the corresponding phenoxy radical, as suggested by laser flash photolysis experiments. Photochemical modelling shows that because of more efficient direct photolysis (due to both higher sunlight absorption and higher photolysis quantum yield), the A 2− form can be degraded up to 3 times faster than HA − in surface waters. An exception is represented by low-DOC (dissolved organic carbon) conditions, where the • OH reaction dominates degradation and the transformation kinetics of HA − is faster compared to A 2− . The half-life time of BP-4 in mid-latitude summertime would be in the range of days to weeks, depending on the environmental conditions. BP-4 also reacts with Br 2 −• , and a rate constant

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Photochemical degradation of benzotriazole in aqueous solution

Andreozzi

Caprio

Insola

et al. 1998

J. Chem. Technol. Biotechnol.

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Photochemical degradation of benzotriazole is investigated in aqueous solution at 25¡C and pH values varying in the range 3È11. The quantum yields at di †erent pH values are evaluated by analysing the kinetics of the reacting system. Reaction kinetics are markedly a †ected by pH because of its inÑuence upon benzotriazole dissociation. A mathematical method that takes into account the presence of intermediates and of the pH has been developed.1998 Society ( of Chemical Industry

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Reactions of hydroxyl radicals with hydrogen peroxide at ambient and elevated temperatures

Cited by 454 publications

References 3 publications

Free-radical redox reactions of uranium ions in sulphuric acid solutions

Free-radical redox reactions of uranium ions in sulphuric acid solutions

Photochemical processes involving the UV absorber benzophenone-4 (2-hydroxy-4-methoxybenzophenone-5-sulphonic acid) in aqueous solution: Reaction pathways and implications for surface waters

Photochemical degradation of benzotriazole in aqueous solution

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