Critical Review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (⋅OH/⋅O− in Aqueous Solution

1988 ◽  
Vol 17 (2) ◽  
pp. 513-886 ◽  
Author(s):  
George V. Buxton ◽  
Clive L. Greenstock ◽  
W. Phillips Helman ◽  
Alberta B. Ross
Keyword(s):  
Aqueous Solution ◽  
Hydroxyl Radicals ◽  
Rate Constants ◽  
Critical Review ◽  
Hydrogen Atoms ◽  
Hydrated Electrons

scholarly journals Photochemical Degradation of Short-Chain Chlorinated Paraffins in Aqueous Solution by Hydrated Electrons and Hydroxyl Radicals

2022 ◽  
Author(s):  
Brian DiMento ◽  
Cristina Tusei ◽  
Christoph Aeppli
Keyword(s):  
Organic Pollutants ◽  
Hydroxyl Radicals ◽  
Surface Waters ◽  
Rate Constants ◽  
Degradation Rate ◽  
Chlorine Content ◽  
Photochemical Degradation ◽  
Model Compounds ◽  
Chlorinated Paraffins ◽  
Hydrated Electrons

Short-chain chlorinated paraffins (SCCPs) are a complex mixture of polychlorinated alkanes (C10-C13, chlorine content 40-70%), and have been categorized as persistent organic pollutants. However, there are knowledge gaps about their environmental degradation, particularly the effectiveness and mechanism of photochemical degradation in surface waters. Photochemically-produced hydrated electrons (e-(aq)) have been shown to degrade highly chlorinated compounds in environmentally-relevant conditions more effectively than hydroxyl radicals (·OH), which can degrade a wide range of organic pollutants. This study aimed to evaluate the potential for e-(aq) and ·OH to degrade SCCPs. To this end, the degradation of SCCP model compounds was investigated under laboratory conditions that photochemically produced e-(aq) or ·OH. Resulting SCCP degradation rate constants for e-(aq) were on the same order of magnitude as well-known chlorinated pesticides. Experiments in the presence of ·OH yielded similar or higher second-order rate constants. Trends in e-(aq) and ·OH SCCP model compounds degradation rate constants of the investigated SCCPs were consistent with that of other chlorinated compounds, with higher chlorine content producing in higher rate constants for e-(aq) and lower for ·OH. Above a chlorine:carbon ratio of approximately 0.6, the e-(aq) second-order rate constants were higher than rate constants for ·OH reactions. Results of this study furthermore suggest that SCCPs are likely susceptible to photochemical degradation in sunlit surface waters, facilitated by dissolved organic matter that can produce e-(aq) and ·OH when irradiated.

Comparison of muonium and positronium with hydrogen atoms in their reactions towards solutes containing amide and peptide linkages in water and micelle solutions

1989 ◽  
Vol 67 (1) ◽  
pp. 120-126 ◽  
Author(s):  
Mary V. Barnabas ◽  
Krishnan Venkateswaran ◽  
David C. Walker
Keyword(s):  
Carbonyl Group ◽  
Rate Constants ◽  
Reaction Rates ◽  
Hydrogen Atoms ◽  
Methyl Group ◽  
Hydrated Electrons

Rate constants have been sought for the reaction of muonium (Mu) and o-positronium (Ps) with solutions of thirteen solutes containing [Formula: see text] the groups. Values of k range from <105 M−1 s−1 to 3 × 1010 M−1 s−1 and show a variety of trends. For instance, Mu adds across the carbonyl group much faster than does H, but abstracts from an adjacent methyl group more slowly. Mu adds exceptionally efficiently to the thiocarbonyl group. Abstraction reactions are identified by large enhancements in reaction rates when localized in micelles. Ps behaves quite differently to the others in neither abstracting nor adding to these compounds, consistent with it not being a pseudo-isotope of hydrogen. Keywords: muonium, positronium, hydrogen, hydrated electrons, micelles.

Nonylphenols degradation in the UV, UV/H2O2, O3 and UV/O3 processes – comparison of the methods and kinetic study

2015 ◽  
Vol 71 (3) ◽  
pp. 446-453 ◽  
Author(s):  
E. Felis ◽  
K. Miksch
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Hydroxyl Radicals ◽  
Rate Constants ◽  
Uv Light ◽  
Second Order ◽  
Quantum Yields ◽  
Environmental Significance ◽  
Order Rate ◽  
Technical Mixture

This paper describes the results of experiments on the decomposition of selected nonylphenols (NPs) in aqueous solutions using the UV, UV/H2O2, O3 and UV/O3 processes. The goal of the research was to determine the kinetic parameters of the above-mentioned processes, and to estimate their effectiveness. These substances were selected because of their ubiquitous occurrence in the aquatic environment, resistance to biodegradation and environmental significance. As a result of the experiments, the quantum yields of the 4-n-nonylphenol (4NP) and NP (technical mixture) photodegradation in aqueous solution were calculated to be 0.15 and 0.17, respectively. The values of the second-order rate constants of the investigated compounds with hydroxyl radical and NP with ozone were also determined. The estimated second-order rate constants of 4NP and NP with hydroxyl radicals were equal to 7.6 × 108–1.3 × 109 mol−1 L s−1. For NP, the determined rate constant with ozone was equal to 2.01 × 106 mol−1 L s−1. The performed experiments showed that NP was slightly more susceptible to degradation by the UV radiation and hydroxyl radicals than 4NP. The study demonstrated also that the polychromatic UV-light alone and also in combination with selected oxidizers (i.e. hydrogen peroxide, ozone) may be successfully used for the removal of selected NPs from the aqueous medium.

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