Mechanism of photodegradation of aqueous organic pollutants. 2. Measurement of the primary rate constants for reaction of hydroxyl radicals with benzene and some halobenzenes using an EPR spin-trapping method following the photolysis of hydrogen peroxide

1992 ◽  
Vol 26 (2) ◽  
pp. 262-265 ◽  
Author(s):  
Jan Kochany ◽  
James R. Bolton
Keyword(s):  
Hydrogen Peroxide ◽  
Organic Pollutants ◽  
Hydroxyl Radicals ◽  
Rate Constants ◽  
Spin Trapping ◽  
Trapping Method ◽  
Epr Spin Trapping

Kinetic model for formation of DMPO-OH in water under ultrasonic irradiation using EPR spin trapping method

2012 ◽  
Vol 38 (9) ◽  
pp. 2191-2204 ◽  
Author(s):  
Masaki Kubo ◽  
Kazuhiro Sekiguchi ◽  
Naomi Shibasaki-Kitakawa ◽  
Toshikuni Yonemoto
Keyword(s):  
Kinetic Model ◽  
Ultrasonic Irradiation ◽  
Spin Trapping ◽  
Trapping Method ◽  
Epr Spin Trapping

The photodegradation of model quinolone carboxylates in aqueous media

2014 ◽  
Vol 7 (1) ◽  
pp. 1-8
Author(s):  
Miroslava Bobeničová ◽  
Andrea Čaklóšová ◽  
Dana Dvoranová
Keyword(s):  
Titanium Dioxide ◽  
Hydroxyl Radicals ◽  
Aqueous Media ◽  
Spin Trapping ◽  
Alkaline Media ◽  
Uva Irradiation ◽  
Epr Spin Trapping ◽  
Photoinduced Processes

Abstract This work was focused on the study of photoinduced processes of quinolone carboxylates in the presence of titanium dioxide in an alkaline media. UVA irradiation without/with titanium dioxide caused the decomposition of molecules, with higher efficiency of degradation in the presence of titanium dioxide. EPR spin trapping experiments proved that investigated quinolone carboxylates behave as the efficient scavengers of hydroxyl radicals produced upon irradiation of aerated alkaline titanium dioxide systems.

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.

Relative rate constants for reactions of hydroxyl radicals from the reaction of Fe(II) or Ti(III) with H2O2

1969 ◽  
Vol 47 (20) ◽  
pp. 3737-3744 ◽  
Author(s):  
W. A. Armstrong
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radicals ◽  
Rate Constants ◽  
Relative Rate ◽  
Chloride Ion ◽  
Strong Electron ◽  
Spin Resonance ◽  
Relative Rate Constants ◽  
Novel Method ◽  
Hydroxyl Radical Scavengers

In an attempt to clarify the reactions of ferrous sulfate and titanous sulfate with hydrogen peroxide, a novel method has been developed to determine the relative rate constants for reactions of the oxidizing species generated in these systems. These species react with hydrogen peroxide to give perhydroxyl radicals which combine with titanium(IV) ions to form the relatively stable TiOO•3+ radical. This radical gives a strong electron spin resonance signal and the competition between hydrogen peroxide and a scavenger for the oxidizing species can be followed by measuring the amplitude of this signal in the presence of various concentrations of scavenger. The relative rate constants calculated in this way for both the Fe(II)–H2O2 and Ti(III)–H2O2 systems at pH 1.0 agree with those reported for the reactions of hydroxyl radicals in γ-irradiated thymine solutions. This supports the view that hydroxyl radicals are formed in these cases.Under conditions of acidity favoring the hydrolysis of Fe(II) to FeOH+ ions, hydroxyl radical scavengers do not compete with hydrogen peroxide for the precursors of the TiOO•3+ radical. It is suggested that the FeOH+ ions react with hydrogen peroxide to give a different oxidizing species, possibly the ferryl ion.Scavengers investigated were thymine, methanol, ethanol, formic acid, acetic acid, chloride ion, and several amino acids.

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