Articoli di riviste: "Radical hydroxyl. Chlore. Ozone"

1

Ye, Miaomiao, Tuqiao Zhang, Zhiwei Zhu, Yan Zhang e Yiping Zhang. "Photodegradation of 4-chloronitrobenzene in the presence of aqueous titania suspensions in different gas atmospheres". Water Science and Technology 64, n. 7 (1 ottobre 2011): 1466–72. http://dx.doi.org/10.2166/wst.2011.531.

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The photocatalytic degradation of 4-chloronitrobenzene (4-CNB) was carried out using Degussa P25 TiO2 as photocatalyst in three different gas atmospheres: nitrogen, oxygen, and ozone. The total organic carbon (TOC) and inorganic anions including chloride, nitrite, and nitrate anions were measured to monitor the mineralization processes, while the degradation of 4-CNB and the formation of intermediates were followed by liquid chromatography–mass spectrometry (LC/MS). Results showed that the photocatalytic efficiency followed the order of TiO2/UV/N2 < TiO2/UV/O2 < TiO2/UV/O3, which was further proved by evaluating the reaction activities using electron paramagnetic resonance (EPR) spin trapping technique. Chlorine atom, nitro group and hydrogen atom of the benzene ring could be displaced by hydroxyl radical (•OH) leading to the formation of chloride, nitrite (III) anions and a variety of phenols, then the nitrite (III) anions were further oxidized to nitrate (V) anions. 4-Nitrophenol and 5-chloro-2-nitrophenol were identified and quantified in both of the TiO2/UV/N2 and TiO2/UV/O2 processes while no aromatic intermediates were monitored in the process of TiO2/UV/O3.

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Cho, Min, Hyenmi Chung e Jeyong Yoon. "Disinfection of Water Containing Natural Organic Matter by Using Ozone-Initiated Radical Reactions". Applied and Environmental Microbiology 69, n. 4 (aprile 2003): 2284–91. http://dx.doi.org/10.1128/aem.69.4.2284-2291.2003.

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ABSTRACT Ozone is widely used to disinfect drinking water and wastewater due to its strong biocidal oxidizing properties. Recently, it was reported that hydroxyl radicals (·OH), resulting from ozone decomposition, play a significant role in microbial inactivation when Bacillus subtilis endospores were used as the test microorganisms in pH controlled distilled water. However, it is not yet known how natural organic matter (NOM), which is ubiquitous in sources of drinking water, affects this process of disinfection by ozone-initiated radical reactions. Two types of water matrix were considered for this study. One is water containing humic acid, which is commercially available. The other is water from the Han River. This study reported that hydroxyl radicals, initiated by the ozone chain reaction, were significantly effective at B. subtilis endospore inactivation in water containing NOM, as well as in pH-controlled distilled water. The type of NOM and the pH have a considerable effect on the percentage of disinfection by hydroxyl radicals, which ranged from 20 to 50%. In addition, the theoretical C̅T value of hydroxyl radicals for 2-log B. subtilis removal was estimated to be about 2.4 × 104 times smaller than that of ozone, assuming that there is no synergistic activity between ozone and hydroxyl radicals.

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Jung, Jong Tae, Jong Oh Kim, Bum Gun Kwon e Dong Ha Song. "Removal of Refractory Organic Compounds Using Peroxy Radical and Ozone Reaction in Aqueous Solution". Materials Science Forum 569 (gennaio 2008): 33–36. http://dx.doi.org/10.4028/www.scientific.net/msf.569.33.

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This study was conducted to evaluate the treatment performance of the system using peroxy radical/ozone reaction for refractory organic compounds removal in aqueous solution. The effect of initial humic acid concentration was conducted under the conditions of humic acid concentration 10 mg/L, 30 mg/L, 50 mg/L and 100 mg/L. Reaction rate constant (k) in 30 mg/L of humic acid concentration was higher than that of humic acid concentration 10 mg/L, 50 mg/L amd 100 mg/L. However, it decreased over the range of 30 mg/L of humic acid concentration due to the action of internal filter of humic acid itself. Reaction rate constant (k) in the initial 20 minute of reaction time was accelerated by decreasing hydraulic retention time (HRT). This may be ascribed to increase the reaction time between peroxy radical and ozone. pH is a key for both ozone stability and TiO2 surface property in aqueous solution. Reaction rate constant (k) of acid solution on pH variation was smaller compared to that of neutral or basic circumstances because ozone decomposes easily into hydroxyl radicals in neutral or basic solution. At reaction rate constant (k) for humic acid degradation in each unit process, peroxy radical/ozone combined system was higher than that of ozone only due to the effective production of hydroxyl radical. An obvious difference between ozone and peroxy radical/ozone is the consequence of hydroxyl radical produced by the reaction of ozone molecules and peroxy radicals.

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Beltrán, Fernando J., Manuel Checa, Javier Rivas e Juan F. García-Araya. "Modeling the Mineralization Kinetics of Visible Led Graphene Oxide/Titania Photocatalytic Ozonation of an Urban Wastewater Containing Pharmaceutical Compounds". Catalysts 10, n. 11 (30 ottobre 2020): 1256. http://dx.doi.org/10.3390/catal10111256.

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In a water ozonation process, dissolved organics undergo two reactions at least: direct ozone attack and oxidation with hydroxyl radicals generated from the ozone decomposition. In the particular case of urban wastewater contaminated with pharmaceuticals, competition between these two reactions can be studied through application of gas–liquid reaction kinetics. However, there is a lack in literature about kinetic modeling of ozone processes in water specially in photocatalytic ozonation. In this work, lumped reactions of ozone and hydroxyl radicals with total organic carbon have been proposed. Urban wastewater containing a mixture of eight pharmaceutical compounds has been used to establish the kinetic model that simulates the mineralization process. The kinetic model is based on a mechanism of free radical and molecular reactions and the knowledge of mass transfer, chemical reaction rate constants, and radiation transfer data. According to the model, both single ozonation and photocatalytic ozonation present two distinct reaction periods characterized by the absence and presence of dissolved ozone. In the first period (less than 10 min), pharmaceuticals mainly disappear by direct ozone reactions and TOC variation due to these compounds has been modeled according to gas–liquid reaction kinetics through a lumped ozone-pharmaceutical TOC fast second order reaction. The corresponding rate constant of this reaction was found to change with time from 3 × 105 to 200 M−1 s−1 with Hatta values higher than 0.3. In the second period (nearly 5 h), competition between direct and hydroxyl radical reactions takes place and a kinetic model based on a direct and free radical reaction mechanism is proposed. Main influencing parameters to be known were: Direct ozone reaction rate constant, catalyst quantum yield, and hydroxyl radical scavengers. The first two take values of 0.5 M−1 s−1 and 5 × 10−4 mol·photon−1, respectively, while a fraction of TOC between 10% and 90% that changes with time was found to possess hydroxyl radical scavenger nature.

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Tootchi, L., R. Seth, S. Tabe e P. Yang. "Transformation products of pharmaceutically active compounds during drinking water ozonation". Water Supply 13, n. 6 (12 settembre 2013): 1576–82. http://dx.doi.org/10.2166/ws.2013.172.

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Ozonation and ozone-based advanced oxidation processes have been shown to be effective in the oxidation of several pharmaceutically active compounds (PhACs) routinely detected in surface waters. Under typical operating conditions of these processes, most of the parent compound oxidized is expected to lead to the formation of transformation products (TPs). For a target ozone exposure, the resulting hydroxyl radical exposure depends on the water matrix or process chosen (e.g. peroxone) which in turn may influence the degradation pathway and the TPs formed. This study was undertaken to examine the expected impact that varying ozone and hydroxyl radical exposures may have on TP formation from the oxidation of PhACs during typical drinking water ozonation. Two representative PhACs were selected for the study. Carbamazepine was chosen to represent PhACs with a fast reaction rate with ozone (kO3 > 104 M−1 s−1) and bezafibrate was chosen to represent PhACs with a slow to moderate reaction rate with ozone (kO3 < 104 M−1 s−1). The results show that under varying ozone and hydroxyl exposure scenarios examined, the major oxidation pathway for the parent compound was dominated by reaction with ozone for carbamazepine while for bezafibrate it varied.

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Vel Leitner, Nathalie Karpel, e Babak Roshani. "Kinetic of benzotriazole oxidation by ozone and hydroxyl radical". Water Research 44, n. 6 (marzo 2010): 2058–66. http://dx.doi.org/10.1016/j.watres.2009.12.018.

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Spanggord, Ronald J., David Yao e Theodore Mill. "Kinetics of Aminodinitrotoluene Oxidations with Ozone and Hydroxyl Radical". Environmental Science & Technology 34, n. 3 (febbraio 2000): 450–54. http://dx.doi.org/10.1021/es990189i.

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Azrague, K., S. W. Osterhus e J. G. Biomorgi. "Degradation of pCBA by catalytic ozonation in natural water". Water Science and Technology 59, n. 6 (1 marzo 2009): 1209–17. http://dx.doi.org/10.2166/wst.2009.078.

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The catalytic effect of commercially available ceramic Raschig rings versus stainless steel rings (known to be oxidant resistant) at different water qualities, for the decomposition of ozone and the hydroxyl radical formation have been investigated by using an ozone bubble column. Para-chlorobenzoic acid (pCBA) has been used as a model pollutant since it has been reported to be an ideal compound for ozone AOP studies because it displays slow reaction rates with ozone, but rapid oxidation kinetics with the OH radical. While the ozone was quite stable when the stainless steel rings were used as a packing media, the ceramic media enhanced the decomposition of the ozone. Nevertheless, the water quality was found to significantly affect the ozone stability. Indeed, in addition to high pH, both NOM and TIC lowered the ozone concentration in the system. When considering the degradation of pCBA, the ceramic packing rings, as high pH and NOM, increases its rate constant which is correlated to the higher decomposition of ozone and consequently to higher formation of hydroxyl radicals. In contrast, TIC decreased the degradation rate of pCBA even if it decomposes the ozone which is due to its scavenging effect.

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Utsumi, Hideo, Sang-Kuk Han e Kazuhiro Ichikawa. "Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation". Water Science and Technology 38, n. 6 (1 settembre 1998): 147–54. http://dx.doi.org/10.2166/wst.1998.0247.

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Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 X 10-6M of DMPO-OH, indicating that 1.4% of •OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance •OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.

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Mutseyekwa, Michael Emmanuel, Şifa Doğan e Saltuk Pirgalıoğlu. "Ozonation for the removal of bisphenol A". Water Science and Technology 76, n. 10 (2 agosto 2017): 2764–75. http://dx.doi.org/10.2166/wst.2017.446.

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Abstract The mechanism of byproduct formation and oxidation pathway of bisphenol A (BPA) during ozonation process have been compared under acidic, neutral and alkaline conditions at an applied ozone dose of 5.3 mg·L−1 min−1. Alkaline conditions promoted the fastest removal and the pseudo first-order reaction rate constant was calculated as 0.15 min−1. Complete removal under alkaline conditions (after 30 minutes of reaction time) was achieved with 1.59 mg ozone per mg BPA and 52% mineralization was achieved at 6.04 mg ozone application per mg total organic carbon (after 90 minutes of reaction time). Hydroxyl radical dominated degradation pathway (pH 10) resulted with opening of ring-structured products into Heptanoic acid, methyl ester. Sixty per cent BPA removal occurred under acidic conditions where the ozone was dominant and formation of Cyclohexene-1-carboxylic acid, ethyl ester, Benzaldehyde, 4-hydroxy-3,5-dimethyl- and 2-Phenylbenzoquinone were evidenced. Despite the fact that complete removal was achieved under neutral conditions, mineralization was not remarkable and both hydroxyl radical and ozone-based degradation pattern was evidenced after the treatment.

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Han, Y. H., K. Ichikawa e H. Utsumi. "A kinetic study of enhancing effect by phenolic compounds on the hydroxyl radical generation during ozonation". Water Science and Technology 50, n. 8 (1 ottobre 2004): 97–102. http://dx.doi.org/10.2166/wst.2004.0497.

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Ozone decomposition in aqueous solution proceeds through a radical type chain mechanism. These reactions involve the very reactive and catalytic intermediates O2- radical, OH radical, HO2 radical, OH-, H2O2, etc. OH radical is proposed as an important factor in the ozonation of water among them. In the present study, the enhancing effects of several phenolic compounds; phenol, 2-, 3-, 4-monochloro, 2,4-dichloro, 2,4,6-trichlorophenol on OH radical generation were mathematically evaluated using the electron spin resonance (ESR)/spin-trapping technique. OH radical was trapped with a 5,5-dimethyl-1-pyrroline-Noxide (DMPO) as a stable adduct, DMPO-OH. The initial velocities of DMPO-OH generation in ozonated water containing phenolic compounds were quantitatively measured using a combined system of ESR spectroscopy with stopped-flow apparatus, which was controlled by homemade software. The initial velocities of DMPO-OH generation increased as a function of the ozone concentration. The relation among ozone concentration, amount of phenolic compounds and the initial velocity (ν0) of DMPO-OH generation was mathematically analyzed and the following equation was obtained, ν0 (10-6 M/s) = (A′ × [PhOHs (10-9M)] + 0.0005) exp (60 × [ozone (10-9 M)]). The equation fitted very well with the experimental results, and the correlation coefficient was larger than 0.98.

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Ramasamy, Sathiyamurthi, Tomoki Nakayama, Yu Morino, Takashi Imamura, Yoshizumi Kajii, Shinichi Enami e Kei Sato. "Nitrate radical, ozone and hydroxyl radical initiated aging of limonene secondary organic aerosol". Atmospheric Environment: X 9 (gennaio 2021): 100102. http://dx.doi.org/10.1016/j.aeaoa.2021.100102.

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13

Liu, Xiaoyu, Harvey E. Jeffries e Kenneth G. Sexton. "Hydroxyl radical and ozone initiated photochemical reactions of 1,3-butadiene". Atmospheric Environment 33, n. 18 (agosto 1999): 3005–22. http://dx.doi.org/10.1016/s1352-2310(99)00078-3.

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Forester, C. D., e J. R. Wells. "Hydroxyl radical yields from reactions of terpene mixtures with ozone". Indoor Air 21, n. 5 (9 maggio 2011): 400–409. http://dx.doi.org/10.1111/j.1600-0668.2011.00718.x.

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Elovitz, Michael S., e Urs von Gunten. "Hydroxyl Radical/Ozone Ratios During Ozonation Processes. I. The RctConcept". Ozone: Science & Engineering 21, n. 3 (gennaio 1999): 239–60. http://dx.doi.org/10.1080/01919519908547239.

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Engdahl, Anders, e Bengt Nelander. "A 1:1 complex between a hydroxyl radical and ozone". Journal of Chemical Physics 122, n. 12 (22 marzo 2005): 126101. http://dx.doi.org/10.1063/1.1872852.

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Ma, Tsz-Kan, Diyuan Li e Jonathan D. Wilden. "Mechanistic studies of reactive oxygen species mediated electrochemical radical reactions of alkyl iodides". Chemical Communications 57, n. 67 (2021): 8356–59. http://dx.doi.org/10.1039/d1cc03019a.

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Pisarenko, Aleksey N., Erica J. Marti, Daniel Gerrity, Julie R. Peller e Eric R. V. Dickenson. "Effects of molecular ozone and hydroxyl radical on formation of N-nitrosamines and perfluoroalkyl acids during ozonation of treated wastewaters". Environmental Science: Water Research & Technology 1, n. 5 (2015): 668–78. http://dx.doi.org/10.1039/c5ew00046g.

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Ragnar, M., T. Eriksson e T. Reitberger. "Radical Formation in Ozone Reactions with Lignin and Carbohydrate Model Compounds". Holzforschung 53, n. 3 (10 maggio 1999): 292–98. http://dx.doi.org/10.1515/hf.1999.049.

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Summary Using different independent methods, the kinetics of ozone consumption and the initial radical yield in reactions of ozone with lignin and carbohydrate model compounds were investigated. It was demonstrated that ozone reacts with phenolates several orders of magnitude more rapidly than with corresponding undissociated phenols. The pH dependence of the radical yield does not completely follow the pK a-value of the phenols. In fact, the radical yield starts to increase at pH 3 for all the phenolic model compounds investigated. Several indications suggest that superoxide rather than the hydroxyl radical is initially formed when ozone reacts with lignin model compounds. In contrast to lignin model compounds no radicals were detected in ozone reactions with carbohydrate model compounds or olefins. On the basis of this study, it may be concluded that ozone bleaching should preferably be performed at pH 3 and at a higher consistency. No significant effect of metal ions was observed.

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Fijołek, Lilla, Joanna Świetlik e Marcin Frankowski. "The Role of Sulphate and Phosphate Ions in the Recovery of Benzoic Acid Self-Enhanced Ozonation in Water Containing Bromides". Molecules 26, n. 9 (5 maggio 2021): 2701. http://dx.doi.org/10.3390/molecules26092701.

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The ozonation of aromatic compounds in low-pH water is ineffective. In an acidic environment, the decomposition of ozone into hydroxyl radicals is limited and insufficient for the degradation of organic pollutants. Radical processes are also strongly inhibited by halogen ions present in the reaction medium, especially at low pH. It was shown that even under such unfavorable conditions, some compounds can initiate radical chain reactions leading to the formation of hydroxyl radicals, thus accelerating the ozonation process, which is referred to as so-called “self-enhanced ozonation”. This paper presents the effect of bromides on “self-enhanced ozonation” of benzoic acid (BA) at pH 2.5. It is the first report to fully and quantitatively describe this process. The presence of only 15 µM bromides in water inhibits ozone decomposition and completely blocks BA degradation. However, the effectiveness of this process can be regained by ozonation in the presence of phosphates or sulphate. The addition of these inorganic salts to the bromide-containing solution helps to recover ozone decomposition and BA degradation efficiency. As part of this research, the fractions of hydroxyl, sulphate and phosphate radicals reacting with benzoic acid and bromides were calculated.

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Kumarathasan, Prem, Renaud Vincent, Patrick Goegan, Marc Potvin e Josée Guénette. "Hydroxyl radical adduct of 5-aminosalicylic acid: A potential marker of ozone-induced oxidative stress". Biochemistry and Cell Biology 79, n. 1 (1 gennaio 2001): 33–42. http://dx.doi.org/10.1139/o00-091.

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The use of 5-aminosalicylic acid in assessment of reactive oxygen species formation was investigated by in vitro Fenton and ozonation reactions, and by in vivo ozone-exposure experiments. Enzymatic hydroxylation was evaluated by a microsomal assay. Fischer 344 male rats (250 g) injected with 5-aminosalicylic acid (100 mg·kg-1 i.p.; 30 min) were exposed to ozone (0, 1, 2 ppm; nose only, 2 h); bronchoalveolar lavage, lung homogenates, and plasma were recovered. Oxidation products of 5-aminosalicylic acid were as follows: salicylic acid, by deamination; 2,3-dihydroxybenzoic acid and 2,5-dihydroxybenzoic acid, from radical or enzymatic hydroxylation; 5-amino-2-hydroxy-N,N'-bis(3-carboxy-4-hydroxyphenyl)-1,4-benzoquinonediimine, a condensation product of oxidized 5-aminosalicylic acid; and 5-amino-2,3,4,6-tetrahydroxybenzoic acid, attributed to hydroxyl radical attack without deamination, identified by HPLC electrochemical (HPLC-EC) detector system analysis and by GC-MS analysis of trimethylsilyl derivatives. 5-Aminotetrahydroxybenzoic acid was not formed enzymatically. 5-Aminotetrahydroxybenzoic acid, but not 5-aminosalicylic acid, was significantly elevated in bronchoalveolar lavage (+86%) and lung homogenates (+56%) in response to 2 ppm ozone (p < 0.05); no significant changes were detected in plasma. The data indicate that hydroxylation of 5-aminosalicylic acid is a potential specific probe for in vivo oxidative stress.Key words: 5-aminosalicylic acid, biomarker, free radical scavenging, hydroxyl radical, ozone.

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Han, Y. H., I. Koshiishi e H. Utsumi. "Determination of an effect of 3-chlorophenol on hydroxyl radical generation during ozonation through kinetic study in the power law type". Water Supply 4, n. 5-6 (1 dicembre 2004): 305–11. http://dx.doi.org/10.2166/ws.2004.0121.

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Ozone decomposition in aqueous solution proceeds through a radical type chain mechanism. These reactions involve the very reactive and catalytic intermediates hydroxyl (OH) radical, O2− radical, HO2 radical, OH−, H2O2, etc. OH radical is proposed as an important factor in the ozonation of water. In the previous study, generation of OH radical in the ozonation of water containing 3-chlorophenol was mathematically evaluated. In this study, we estimated the kinetic equation for the effect of 3-chlorophenol on OH radical generation during ozonation using the power law equation, in order to analyze it more correctly. The OH radical was trapped with a 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a stable adduct, DMPO-OH. The relationship between the ozone concentration, 3-chlorophenol content, and the initial velocity (ν0) of DMPO-OH generation was analyzed mathematically, and the following equation was obtained: ν0 (10−6 M/s)=(1.58×10−5)×[3-chlorophenol (10−6 M)]×[ozone (10−6 M)]2.40+(3.09×10−5)×[ozone (10−6 M)]1.72. The equation fitted very well with the experimental results, and square of the correlation coefficient was larger than 0.9.

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Shao, Yu, Zhicheng Pang, Lili Wang e Xiaowei Liu. "Efficient Degradation of Acesulfame by Ozone/Peroxymonosulfate Advanced Oxidation Process". Molecules 24, n. 16 (8 agosto 2019): 2874. http://dx.doi.org/10.3390/molecules24162874.

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Artificial sweeteners (ASWs), a class of emerging contaminants with good water solubility, have attracted much attention recently because of their wide use and negative impact on the aquatic environment and drinking water. Efficient technologies for removing ASWs are in urgent need. This study investigated degradation of typical ASW acesulfame by ozone-activated peroxymonosulfate process (O3/PMS) in prepared and real waters. O3/PMS can degrade >90% acesulfame in prepared water within 15 min at a low dosage of O3 (60 ± 5 µg∙min−1) and PMS (0.4 mM). Ozone, hydroxyl radical (HO•), and sulfate radical (SO4•−) were identified as contributors for ACE degradation and their contribution proportion was 27.1%, 25.4%, and 47.5% respectively. O3/PMS showed the best degradation performance at neutral pH and were sensitive to constituents such as chloride and natural organic matters. The qualitative analysis of degradation products confirmed the involvement of hydroxyl radical and sulfate radical and figured out that the active sites of ACE were the C=C bond, ether bond, and C-N bond. The electrical energy per order ACE degradation were calculated to be 4.6 kWh/m3. Our findings indicate that O3 is an efficient PMS activator and O3/PMS is promising due to its characteristic of tunable O3−HO• SO4•− ternary oxidant involving.

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Ikhlaq, Amir, Rahat Javaid, Asia Akram, Umair Yaqub Qazi, Javeria Erfan, Metwally Madkour, Mohamed Elnaiem M. Abdelbagi, Sami M. Ibn Shamsah e Fei Qi. "Application of Attapulgite Clay-Based Fe-Zeolite 5A in UV-Assisted Catalytic Ozonation for the Removal of Ciprofloxacin". Journal of Chemistry 2022 (19 maggio 2022): 1–10. http://dx.doi.org/10.1155/2022/2846453.

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For the first time, Fe-zeolite 5A (Fe-Z5A) efficacy in the UV-assisted ozonation process to remove ciprofloxacin (CF) in wastewater is investigated. FTIR, SEM, EDX, BET, and the mass transfer process for point of zero charge are used to characterize the catalyst. Furthermore, the synergic process (UV/O3/Fe-Z5A) is compared with O3, O3/UV, and Fe-Z5A/O3 processes. The influence of catalyst dose, hydroxyl radical scavenger, and off-gas ozone released is discussed. The removal efficiency of CF in wastewater (for the synergic process) is compared with a single ozonation process. The results indicate that the synergic process was more efficient than others, with about 73% CF being removed (in 60 minutes) in the synergic process. The results also show that synergic processes produce less off-gas ozone than other processes, suggesting more ozone consumption in the synergic process, and confirmed by the radical scavenger effect and hydrogen peroxide decomposition studies. The Fe-Z5A was found to operate through a hydroxyl mechanism in which Fe worked as an active site that promotes the formation of hydroxyl radicals. Finally, the synergic process was more efficient than the ozonation process in the wastewater matrix. Hence, Fe-Z5A/O3/UV pathway is highly efficient for the degradation of pharmaceuticals in wastewater.

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Shi, Fa Min, Lei Wang, Si Mo Shi, Han Fei Zhang, Chang Qing Dong e Wu Qin. "Catalytic Hydroxyl Radical Generation by CuO Confined in Multi-Walled Carbon Nanotubes". Advanced Materials Research 557-559 (luglio 2012): 448–55. http://dx.doi.org/10.4028/www.scientific.net/amr.557-559.448.

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A DFT study of the catalytic properties of CuO/CNT and CuO@CNT complexes for the heterogeneous catalytic ozonation has been performed. We illustrated the atomistic details of CuO/CNT and CuO@CNT with a quantitative and qualitative discussion within such an electronic structure characteristics. Ozone was catalytically decomposed into an atomic oxygen species and oxygen molecule on both the surface inner and outer CuO@CNT complex, while ozone can only decompose over CuO on the outer surface of CuO/CNT, with partial electrons transfer from CuO/CNT and CuO@CNT complexes to the adsorbate. Then the atomic oxygen reacted with the water molecule to form two hydroxyl groups on the surface, promoting the reaction chain for the generation of•OH which, in turn, lead to an increase in the catalytic ozonation efficiency. Results show synergetic confinement effect of metal oxide nanoparticles inside CNT could also lead to an acceleration of ozone decomposition and the generation of •OH on the inner and outer surface of carbon-nanotube containing catalytic particles.

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Ragnar, M., T. Eriksson e T. Reitberger. "Detection of Radicals Generated by Strong Oxidants in Acidic Media". Holzforschung 53, n. 3 (10 maggio 1999): 285–91. http://dx.doi.org/10.1515/hf.1999.048.

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Summary A new method to study superoxide and hydroxyl radicals in aqueous solution in the pH range 1 to 6 is described and critically evaluated. The method primarily detects superoxide, which reacts with tetranitromethane (TNM) by reductive cleavage. The strongly coloured nitroform anion (ε350nm = 15000M−1 cm−1) formed, is easily measured in a spectrophotometer or in a stopped-flow equipment. Hydroxyl radicals are measured indirectly. In a first step the hydroxyl radical reacts with iso-propyl alcohol to give acetone and superoxide. The superoxide formed is then in a second step detected with TNM. The TNM-method was primarily designed to monitor the radical formation under ozone bleaching conditions, but it is also applicable in acidic hydrogen peroxide.

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Hunter, Gary, Bob Hulsey, Jim Coughenour, Thomas Walz e Shane Snyder. "Out in the Ozone the Return of Ozone and the Hydroxyl Radical to Wastewater Disinfection". Proceedings of the Water Environment Federation 2006, n. 12 (1 gennaio 2006): 1192–201. http://dx.doi.org/10.2175/193864706783749620.

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Zhu, Shumin, Bingzhi Dong, Naiyun Gao e Jin Jiang. "Removal of IBMP using ozonation: role of ozone and hydroxyl radical". Desalination and Water Treatment 57, n. 59 (20 giugno 2016): 28776–83. http://dx.doi.org/10.1080/19443994.2016.1193063.

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29

Nöthe, Tobias, Hans Fahlenkamp e Clemens von Sonntag. "Ozonation of Wastewater: Rate of Ozone Consumption and Hydroxyl Radical Yield". Environmental Science & Technology 43, n. 15 (agosto 2009): 5990–95. http://dx.doi.org/10.1021/es900825f.

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30

Burns, Nick, Gary Hunter, Amanda Jackman, Bob Hulsey, Jim Coughenour e Thomas Walz. "The Return of Ozone and the Hydroxyl Radical to Wastewater Disinfection". Ozone: Science & Engineering 29, n. 4 (31 luglio 2007): 303–6. http://dx.doi.org/10.1080/01919510701463206.

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31

Ali, Zarafshan, Amir Ikhlaq, Umair Yaqub Qazi, Asia Akram, Iftikhar Ul-Hasan, Amira Alazmi, Fei Qi e Rahat Javaid. "Removal of Disperse Yellow-42 Dye by Catalytic Ozonation Using Iron and Manganese-Loaded Zeolites". Water 15, n. 17 (29 agosto 2023): 3097. http://dx.doi.org/10.3390/w15173097.

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Abstract (sommario):

In this research, the efficiency of the catalytic activity of iron and manganese-loaded (bimetallic) sodium zeolite was investigated for the ozonation-based removal of disperse yellow 42 dye. The impregnation method was used to deposit Fe and Mn on the surface of sodium zeolite. The morphological analysis of sodium zeolite before and after Fe and Mn deposition was conducted by SEM, EDX, and FTIR. It was found that several variables, including the ozone dose, contact time, pH, catalyst dose, and hydroxyl radical scavenger action, greatly influenced the efficiency of dye removal. The chemical oxygen demand (COD) removal by catalytic ozonation using Fe and Mn-loaded sodium zeolite from real dye textile wastewater was also investigated. After 30 min of treatment with catalytic ozonation at pH 6, the maximum 73% removal of disperse yellow 42 dye was achieved with a catalyst dose of 0.5 g and an ozone dose supply of 1.8 mg/min. In catalytic ozonation with the hydroxyl radical scavenger effect (HRSE), the decline in removal efficiency from 73% to 61% demonstrated that removal efficiency was highly dependent on hydroxyl radical production. The COD removal efficiency in the real textile wastewater was 59% with the ozonation process, which increased to 79% after catalytic ozonation.

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32

Jiménez-Estrada, Manuel, Ricardo Reyes-Chilpa, Arturo Navarro-Ocaña e Daniel Arrieta-Báez. "Reactivity of Several Reactive Oxygen Species (ROS) with the Sesquiterpene Cacalol". Natural Product Communications 3, n. 4 (aprile 2008): 1934578X0800300. http://dx.doi.org/10.1177/1934578x0800300403.

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Abstract (sommario):

To analyze the antioxidant effects of cacalol we determined its reactivity with different reactive oxygen species (ROS). Cacalol gave rise to cacalone by a specific site reaction with a hydroxyl radical. Singlet oxygen reacted only with the double bond of the furan ring, causing its rupture. On the other hand, ozone reacted with all double bonds in cacalol affording 2-methyl-hexanedioic acid as an end product. No reaction was observed with either superoxide or hydrogen peroxide. The potential antioxidant effect of cacalol as a scavenger of hydroxyl radical and singlet oxygen could be related to its function in the plant roots.

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33

Glaze, William H., Fernando Beltran, Tuula Tuhkanen e Joon-Wun Kang. "Chemical Models of Advanced Oxidation Processes". Water Quality Research Journal 27, n. 1 (1 febbraio 1992): 23–42. http://dx.doi.org/10.2166/wqrj.1992.002.

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Abstract Advanced oxidation processes (AOPs) have been defined as near-ambient temperature processes that involve the generation of highly reactive radical intermediates, especially the hydroxyl radical. These processes show promise for the destruction of hazardous organic substances in municipal and industrial wastes, in drinking water and in ultrapure water. Three types of AOPs are considered in this paper: catalyzed decomposition of ozone; ozone with hydrogen peroxide (Peroxone); and photolysis of hydrogen peroxide with ultraviolet radiation. Kinetic models for these processes are being developed based on known chemical and photochemical principles. The models take into account measured effects of radical scavengers such as bicarbonate; dose ratios of the oxidants or UV intensity; pH; and the presence of generic radical scavengers. The models are used to discuss two cases: oxidation of parts-per-million levels of nitrobenzene with ozone, Peroxone and peroxide/UV and oxidation of naphthalene and pentachlorophenol with peroxide/UV.

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34

Zhao, Wen Yu, Xiao Feng Zheng, Li Wei Xu, Guang Wen Yang e Qi Mu. "Overview and Prospect of Strengthen Ozone Oxidation Technology in Water Treatment". Advanced Materials Research 726-731 (agosto 2013): 1710–14. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.1710.

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Abstract (sommario):

Based on the enhanced formation of hydroxyl free radical (OH), Strengthen ozone oxidation can intensify the oxidizing ability and lower reaction selectivity as a kind of the Advanced Oxidation Technologies (AOTs). This paper introduces the research progress of strengthen ozone oxidation technology such as H2O2 strengthen, catalytic strengthen, UV strengthen, ultrasound strengthen, hydrodynamic cavitations strengthen et al, and points out the research focus and application prospects of this technology.

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35

Derwent, Richard G. "Representing Organic Compound Oxidation in Chemical Mechanisms for Policy-Relevant Air Quality Models under Background Troposphere Conditions". Atmosphere 11, n. 2 (7 febbraio 2020): 171. http://dx.doi.org/10.3390/atmos11020171.

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This intercomparison has taken thirteen chemical mechanisms and compared how they treat VOC oxidation and degradation and its relationship to the photochemical formation of ozone and hydroxyl radicals. Here, we have looked in some detail at the incremental responses of hydroxyl radicals to incremental additions of a range of organic compounds under conditions appropriate to the background atmosphere. Most of the time, with most organic compounds and most chemical mechanisms, incremental additions of an organic compound led to depletion of hydroxyl radical concentrations. The chemical mechanisms studied demonstrated increasingly negative incremental hydroxyl radical reactivities with increasing carbon numbers for the alkanes ethane, propane and n-butane. Hydroxyl radical incremental reactivities for the simple alkenes, ethylene and propylene, were reasonably consistent across the chemical mechanisms studied. However, this consistent representation did not extend to trans but-2-ene, where reactivity estimates spanned a range of a factor of five. Incremental reactivities were reasonably well-defined for isoprene which was encouraging in view of its importance to background tropospheric chemistry. The most serious discrepancies emerging from this study were found with the aromatics toluene and o-xylene, and with the Master Chemical Mechanism and these are discussed in some detail.

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36

Karamah, Eva Fathul, Ika Putri Adripratiwi e Linggar Anindita. "Combination of Ozonation and Adsorption Using Granular Activated Carbon (GAC) for Tofu Industry Wastewater Treatment". Indonesian Journal of Chemistry 18, n. 4 (12 novembre 2018): 600. http://dx.doi.org/10.22146/ijc.26724.

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Abstract (sommario):

Tofu industry wastewater is one of the environmental pollutants that need more effective treatment. Ozonation and adsorption method is known to have the capability to oxidize organic compound in wastewater. Adsorption is done by using granular activated carbon (GAC) as an adsorbent to increase tofu wastewater degradation process by adsorbing organic materials and increasing production of hydroxyl radical as the main oxidizing agent. This research is carried out to evaluate the performance of ozonation, adsorption, and combination of both in processing tofu wastewater. To evaluate the significance of ozone dosage and amount of GAC used, these variations are varied which are 60, 111, and 155 mg/h of ozone dosage and 50, 75, and 100 g of the amount of GAC used. Parameters of the process are organic substances of tofu wastewater such as COD, TSS, and pH. The measurements are being done using a spectrophotometer, colorimeter, and pH meter. The outcome of this research is to provide an alternative method in the liquid waste treatment of the tofu industry and the processed wastewater to meet the environmental quality standards. The more ozone and the more quantity of GAC used, the higher the quantity of hydroxyl radicals formed. Addition of GAC in the ozonation process results in more than 100% increase in hydroxyl radical production. Combination of ozonation and adsorption is able to remove 377.12 mg/L of COD and 26 mg/L of TSS.

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37

Dhanakodi, P., e M. Jayendran. "Hydroxyl Radical Rinse Water Technology using Ozone Ultasonic and Ultraviolet Oxidation Process". Indian Journal of Public Health Research & Development 8, n. 3s (2017): 166. http://dx.doi.org/10.5958/0976-5506.2017.00271.6.

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38

Park, Ji-Ho. "CRDS Study of Tropospheric Ozone Production Kinetics : Isoprene Oxidation by Hydroxyl Radical". Korean Journal of Environmental Health Sciences 35, n. 6 (31 dicembre 2009): 532–37. http://dx.doi.org/10.5668/jehs.2009.35.6.532.

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39

Preis, S., I. C. Panorel, I. Kornev, H. Hatakka e J. Kallas. "Pulsed corona discharge: the role of ozone and hydroxyl radical in aqueous pollutants oxidation". Water Science and Technology 68, n. 7 (1 ottobre 2013): 1536–42. http://dx.doi.org/10.2166/wst.2013.399.

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Abstract (sommario):

Ozone and hydroxyl radical are the most active oxidizing species in water treated with gas-phase pulsed corona discharge (PCD). The ratio of the species dependent on the gas phase composition and treated water contact surface was the objective for the experimental research undertaken for aqueous phenol (fast reaction) and oxalic acid (slow reaction) solutions. The experiments were carried out in the reactor, where aqueous solutions showered between electrodes were treated with 100-ns pulses of 20 kV voltage and 400 A current amplitude. The role of ozone increased with increasing oxygen concentration and the oxidation reaction rate. The PCD treatment showed energy efficiency surpassing that of conventional ozonation.

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40

Chen, L., F. Qi, B. Xu, Z. Xu, J. Shen e K. Li. "The efficiency and mechanism of γ-alumina catalytic ozonation of 2-methylisoborneol in drinking water". Water Supply 6, n. 3 (1 luglio 2006): 43–51. http://dx.doi.org/10.2166/ws.2006.726.

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Abstract (sommario):

The efficiency and mechanism in degradation of 2-methylisoborneol (MIB) as a taste and odour compound in drinking water were studied under the condition where γ-alumina catalysed ozonation. As a result, γ-alumina can show distinct activity in enhancing the efficiency of ozonation of MIB. Tert-butyl alcohol had a remarkable effect on the removal efficiency of catalytic ozonation of MIB. The surface charge status, surface hydroxyl group status of γ-alumina, and pH values of the solution can be linked together. When the pH value of the solution was near the pHzpc of γ-Al2O3, there was observable activity in the catalysed ozonation process. Rct, which denoted the relative concentration of hydroxyl radical (·OH), was much higher in the catalysed ozonation process than in the ozonation process. This result further illuminated that γ-Al2O3 can promote ozone decomposition to produce ·OH. Finally, the effect of rP/I on catalysed ozone decomposition and ozone decomposition was investigated.

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41

Umosekhaimhe, G. O., e S. E. Umukoro. "Thermochemical Evaluation of Hydroxyl and Peroxyl Radical Precursors in the Formation of Tropospheric Ozone Reactions". International Journal of Engineering Research in Africa 3 (novembre 2010): 74–83. http://dx.doi.org/10.4028/www.scientific.net/jera.3.74.

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Abstract (sommario):

The thermochemical properties of varieties of species needed to assess the most prominent pathways of tropospheric ozone transformation have been established. In the troposphere, ozone which is a secondary pollution produced by photochemical induced transformation, acts as an oxidizing agent to numerous atmospheric reactions leading to the formation of particulate matter. Based on the climate related problems resulting from the precursor of particulate matter, it is adequate to establish the feasible routes of ozone formation. In this study, the electronic structure methods which approximate the Schrödinger equation to compute Gibbs free energies and enthalpies of formation of the various chemical species participating in the reactions were used. These thermodynamic properties were determined using four computational model chemistry methods integrated in the Gaussian 03 (G03) chemistry package. Five known reaction pathways for the formation of NO2 (the O3 precursor specie), as well as the dominant ozone formation route from NO2 were examined and their energies determined. Of all the computational methods, the complete basis set (CBS-4M) method produced energies for all species of the five reaction routes. Out of the five routes, only the reactions involving radical species were favoured to completion over a temperature range of -100 and +100oC. The most relevant reaction route for the formation of NO2 and subsequently O3 is that involving the peroxyl acetyl nitrate (PAN) and hydroxyl radicals. Chemical equilibrium analyses of the reaction routes also indicated that reduction in temperature encourages NO2 formation while increase in temperature favours O3 production.

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42

Van der Zee, J., E. Van Beek, T. M. A. R. Dubbelman e J. Van Steveninck. "Toxic effects of ozone on murine L929 fibroblasts. Damage to DNA". Biochemical Journal 247, n. 1 (1 ottobre 1987): 69–72. http://dx.doi.org/10.1042/bj2470069.

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Abstract (sommario):

Damage to DNA caused by exposure of L929 fibroblasts to ozone was reflected by the generation of strand breaks, DNA inter-strand cross-links and DNA-protein cross-links. Addition of propan-2-ol, a hydroxyl radical scavenger, did not affect the formation of strand breaks. In model experiments it appeared that both purines and pyrimidines were involved in DNA inter-strand and DNA-protein cross-links.

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43

Tan, Zhaofeng, Keding Lu, Meiqing Jiang, Rong Su, Hongli Wang, Shengrong Lou, Qingyan Fu et al. "Daytime atmospheric oxidation capacity in four Chinese megacities during the photochemically polluted season: a case study based on box model simulation". Atmospheric Chemistry and Physics 19, n. 6 (20 marzo 2019): 3493–513. http://dx.doi.org/10.5194/acp-19-3493-2019.

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Abstract. Atmospheric oxidation capacity is the basis for converting freshly emitted substances into secondary products and is dominated by reactions involving hydroxyl radicals (OH) during daytime. In this study, we present in situ measurements of ROx radical (hydroxy OH, hydroperoxy HO2, and organic peroxy RO2) precursors and products; the measurements are carried out in four Chinese megacities (Beijing, Shanghai, Guangzhou, and Chongqing) during photochemically polluted seasons. The atmospheric oxidation capacity is evaluated using an observation-based model and radical chemistry precursor measurements as input. The radical budget analysis illustrates the importance of HONO and HCHO photolysis, which account for ∼50 % of the total primary radical sources. The radical propagation is efficient due to abundant NO in urban environments. Hence, the production rate of secondary pollutants, that is, ozone (and fine-particle precursors (H2SO4, HNO3, and extremely low volatility organic compounds, ELVOCs) is rapid, resulting in secondary air pollution. The ozone budget demonstrates its high production in urban areas; also, its rapid transport to downwind areas results in rapid increase in local ozone concentrations. The O3–NOx–VOC (volatile organic compound) sensitivity tests show that ozone production is VOC-limited and that alkenes and aromatics should be mitigated first for ozone pollution control in the four studied megacities. In contrast, NOx emission control (that is, a decrease in NOx) leads to more severe ozone pollution. With respect to fine-particle pollution, the role of the HNO3–NO3 partitioning system is investigated using a thermal dynamic model (ISORROPIA 2). Under high relative humidity (RH) and ammonia-rich conditions, nitric acid converts into nitrates. This study highlights the efficient radical chemistry that maintains the atmospheric oxidation capacity in Chinese megacities and results in secondary pollution characterized by ozone and fine particles.

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44

Kamimura, M., S. Furukawa e J. Hirotsuji. "Development of a simulator for ozone/UV reactor based on CFD analysis". Water Science and Technology 46, n. 11-12 (1 dicembre 2002): 13–19. http://dx.doi.org/10.2166/wst.2002.0710.

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Abstract (sommario):

A new CFD (Computational Fluid Dynamics) simulator for an O3/UV reactor where ozone dissolved water flows under the irradiation of UV, has been developed by combining a fluid dynamics model with a complex radical reaction model. The radical reaction model used in this simulator was found to be reasonable, because the results obtained from the simulation of a completely stirred tank reactor (CSTR) system were in good agreement with the experimental results, e.g., the concentrations of total organic carbon (TOC), hydrogen peroxide and dissolved ozone obtained from a lab-scale CSTR. Furthermore, by using this CFD simulator, the distributions of substances such as hydroxyl radical (OHá) and hydrogen peroxide in the O3/UV reactor have been investigated. These distributions showed that this CFD simulator was considered to be reasonable. In addition, the simulation results suggested that conventional reactors were not optimized.

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45

Yapsaklı, Kozet, e Zehra S. Can. "Interaction of Ozone with Formic Acid: A System which Supresses the Scavenging Effect of HCO3-/CO32-". Water Quality Research Journal 39, n. 2 (1 maggio 2004): 140–48. http://dx.doi.org/10.2166/wqrj.2004.021.

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Abstract (sommario):

Abstract Formic acid, mainly found in its ionized form at pH values greater than 3.75, is among the major by-products of drinking water ozonation. This study focusses on ozone decomposition reactions when formate ion is present. A mechanistic model was developed for ozone decomposition in the presence of formate ion and alkalinity. n-chlorobutane (BuCl) was used as a hydroxyl radical probe. The proposed mechanism is a combination of all the reactions provided in the literature for ozone decomposition, ozone-formate ion interactions, and formate ion and certain inorganic radical interactions in aqueous solutions. The validity of the proposed mechanism was tested by comparing the experimental data collected at different initial ozone and formate ion concentrations, pH and alkalinity to the model predictions. The model was capable of predicting the ozone decomposition and BuCl oxidation data extremely well when 1.53 M-1s-1 (knew) was used as the reaction rate constant for the reaction between ozone and formate ion, as opposed to the value provided in the literature (100 M-1s-1). Furthermore, according to the proposed model formate ion suppresses the scavenging effect of HCO3- and CO32- ions because the reaction of formate ion with CO3*- radical regenerates the OH* radical that is scavenged by the HCO3- and CO32- ions. This was tested by observing ozone decomposition at different levels of alkalinity in the presence of formate ion. The experimental data did not present any significant effect of alkalinity on the decomposition rate. In addition, the model provided highly reliable predictions of the experimental data collected in the presence of alkalinity when knew was used.

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46

Masten, Susan J., e Jürg Hoigné. "Comparison of Ozone and Hydroxyl Radical-Induced Oxidation of Chlorinated Hydrocarbons in Water". Ozone: Science & Engineering 14, n. 3 (giugno 1992): 197–214. http://dx.doi.org/10.1080/01919519208552475.

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47

Cheng, Wen, Li Jiang, Xuejun Quan, Chen Cheng, Xiaoxue Huang, Zhiliang Cheng e Lu Yang. "Ozonation process intensification of p-nitrophenol by in situ separation of hydroxyl radical scavengers and microbubbles". Water Science and Technology 80, n. 1 (1 luglio 2019): 25–36. http://dx.doi.org/10.2166/wst.2019.227.

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Abstract (sommario):

Abstract The ozonation efficiency for removal of recalcitrant organic pollutants in alkaline wastewater is always low because of the presence of some hydroxyl radical scavengers. To solve this problem, the O3/Ca(OH)2 system was put forward, and p-nitrophenol (PNP) was chosen to explore the mechanism of this system. The effects of key operational parameters were studied respectively; the Ca(OH)2 dosage 3 g/L, ozone inlet flow rate 3.5 L/min, ozone concentration 65 mg/L, reactor pressure 0.25 MPa, and temperature 25 °C were obtained as the optimal operating conditions. After 60 min treatment, the organic matter mineralized completely, which was higher than the sum of the ozonation-alone process (55.63%) and the Ca(OH)2 process (3.53%). It suggests that the calcium hydroxide in the O3/Ca(OH)2 process possessed a paramount role in the removal of PNP. The liquid samples and the precipitated substances were analyzed by gas chromatography mass spectrometry, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy; it was demonstrated that Ca(OH)2 could accelerate the generation of hydroxyl radical and simultaneously in situ separate partial intermediate products and CO32− ions through some precipitation reactions.

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48

Sangadkit, W., e J. Kongtrub. "Effective microbial disinfection in food industry with hydroxyl radical fumigation". Food Research 4, S4 (20 dicembre 2020): 65–72. http://dx.doi.org/10.26656/fr.2017.4(s4).010.

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Hydrogen peroxide (H2O2) fumigation has recently been explored and tested to be a good fumigant replacement of formaldehyde. This technique has been proven safer, less irritating and requires shorter exposure times. Surface disinfection has long been implemented with toxic formaldehyde or 35% hydrogen peroxide (H2 O2 ). The results showed that they could be replaced with a safer and stronger oxidizing agent, activated H2O2 in a vaporized form. Aerosolization by aerosol generators has been used to produce aerosols containing hydroxyl radicals of hydrogen peroxide. The dispersal of this highly oxidizing mist of micron-size droplets destroyed Escherichia coli and Aspergillus niger colonies that have been artificially spiked on surfaces. The experiments demonstrated efficient disinfection by integrating 1 to 5% H2 O2 fumigation with ozone (O3 ) and ultraviolet light (UV-C). Studies with E. coli and A. niger showed some disinfection with either O3 or UV-C. Combining H2 O2 fumigation with both O3 and UV-C exposure considerably accelerated the microbial inactivation. This approach allowed fast disinfection with 1 to 5% H2 O2 while offering cheaper and safer disinfection for healthcare settings.

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49

Cazorla, M., W. H. Brune, X. Ren e B. Lefer. "Direct measurement of ozone production rates in Houston in 2009 and comparison with two estimation methods". Atmospheric Chemistry and Physics Discussions 11, n. 10 (10 ottobre 2011): 27521–46. http://dx.doi.org/10.5194/acpd-11-27521-2011.

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Abstract (sommario):

Abstract. Ozone production rates, P(O3), were measured directly using the Penn State Measurement of Ozone Production Sensor (MOPS) during the Study of Houston Atmospheric Radical Precursors (SHARP 2009). Measured P(O3) peaked in the late morning, with values between 15 ppbv h−1 and 100 ppbv h−1, although values of 40–80 ppbv h−1 were typical for higher ozone days. These measurements were compared against ozone production rates calculated using measurements of hydroperoxyl (HO2), hydroxyl (OH), and nitric oxide (NO) radicals, called "calculated P(O3)". The same comparison was done using modeled radicals obtained from a box model with the RACM2 mechanism, called "modeled P(O3)". Measured and calculated P(O3) had similar peak values but the calculated P(O3) tended to peak earlier in the morning when NO values were higher. Measured and modeled P(O3) had a similar dependence on NO, but the modeled P(O3) was only half the measured P(O3). This difference indicates possible missing radical sources in the box model with the RACM2 mechanism and thus has implications for the ability of air quality models to accurately predict ozone production rates.

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50

Felis, E., e K. Miksch. "Nonylphenols degradation in the UV, UV/H2O2, O3 and UV/O3 processes – comparison of the methods and kinetic study". Water Science and Technology 71, n. 3 (6 gennaio 2015): 446–53. http://dx.doi.org/10.2166/wst.2015.011.

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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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