Computerized Pathway Elucidation for Hydroxyl Radical-Induced Chain Reaction Mechanisms in Aqueous Phase Advanced Oxidation Processes

Li, Ke; Crittenden, John C.

doi:10.1021/es802039y

Cited by 35 publications

(46 citation statements)

References 42 publications

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“…The generator enumerates all the major elementary reaction types that have been found to occur during AOPs, 14 including hydrogen abstraction, oxygen addition, HO 2…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Computer-Based First-Principles Kinetic Modeling of Degradation Pathways and Byproduct Fates in Aqueous-Phase Advanced Oxidation Processes

Guo

Minakata

Niu

et al. 2014

Environ. Sci. Technol.

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In this study, a computer-based first-principles kinetic model is developed to predict the degradation mechanisms and fates of intermediates and byproducts produced during aqueous-phase advanced oxidation processes (AOPs) for various organic compounds. The model contains a rule-based pathway generator to generate the reaction pathways, a reaction rate constant estimator to estimate the reaction rate constant for each reaction generated, a mechanistic reduction module to reduce the generated mechanisms, an ordinary differential equations generator and solver to solve the generated mechanisms and calculate the concentration profiles for all species, and a toxicity estimator to estimate the toxicity of major species and calculate time-dependent profiles of relative toxicity (i.e., concentration of species divided by toxicity value). We predict concentration profiles of acetone and trichloroethylene and their intermediates and byproducts in photolysis with hydrogen peroxide (i.e., UV/H2O2) and validate with experimental observations. The predicted concentration profiles for both parent compounds are consistent with experimental data. The calculated profiles of 96-h green algae chronic toxicity show that the overall toxicity decreases during the degradation process. These generated mechanisms also provide detailed and quantitative insights into the pathways for the formation and consumption of important intermediates and byproducts produced during AOPs. Our approach is sufficiently general to be applied to a wide range of contaminants.

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“…The generator enumerates all the major elementary reaction types that have been found to occur during AOPs, 14 including hydrogen abstraction, oxygen addition, HO 2…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Computer-Based First-Principles Kinetic Modeling of Degradation Pathways and Byproduct Fates in Aqueous-Phase Advanced Oxidation Processes

Guo

Minakata

Niu

et al. 2014

Environ. Sci. Technol.

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“…This estimate recognizes the lens effects deriving from the spherical shape of cloud droplets and particles (e.g. Mayer and Madronich, 2004), but it fully neglects any solvent cage effects. Hence, photolysis processes of organic nitrates in aqueous solution must be Figure 13.…”

Section: Detailed Studies Of Organic Nitrate Sinks and Sourcesmentioning

confidence: 99%

Development of a protocol for the auto-generation of explicit aqueous-phase oxidation schemes of organic compounds

et al. 2019

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Abstract. This paper presents a new CAPRAM–GECKO-A protocol for mechanism auto-generation of aqueous-phase organic processes. For the development, kinetic data in the literature were reviewed and a database with 464 aqueous-phase reactions of the hydroxyl radical with organic compounds and 130 nitrate radical reactions with organic compounds has been compiled and evaluated. Five different methods to predict aqueous-phase rate constants have been evaluated with the help of the kinetics database: gas–aqueous phase correlations, homologous series of various compound classes, radical reactivity comparisons, Evans–Polanyi-type correlations, and structure–activity relationships (SARs). The quality of these prediction methods was tested as well as their suitability for automated mechanism construction. Based on this evaluation, SARs form the basis of the new CAPRAM–GECKO-A protocol. Evans–Polanyi-type correlations have been advanced to consider all available H atoms in a molecule besides the H atoms with only the weakest bond dissociation enthalpies (BDEs). The improved Evans–Polanyi-type correlations are used to predict rate constants for aqueous-phase NO3 and organic compounds reactions. Extensive tests have been performed on essential parameters and on highly uncertain parameters with limited experimental data. These sensitivity studies led to further improvements in the new CAPRAM–GECKO-A protocol but also showed current limitations. Biggest uncertainties were observed in uptake processes and the estimation of Henry's law coefficients as well as radical chemistry, in particular the degradation of alkoxy radicals. Previous estimation methods showed several deficits, which impacted particle growth. For further evaluation, a 1,3,5-trimethylbenzene oxidation experiment has been performed in the aerosol chamber “Leipziger Aerosolkammer” (LEAK) at high relative humidity conditions and compared to a multiphase mechanism using the Master Chemical Mechanism (MCMv3.2) in the gas phase and using a methylglyoxal oxidation scheme of about 600 reactions generated with the new CAPRAM–GECKO-A protocol in the aqueous phase. While it was difficult to evaluate single particle constituents due to concentrations close to the detection limits of the instruments applied, the model studies showed the importance of aqueous-phase chemistry in respect to secondary organic aerosol (SOA) formation and particle growth. The new protocol forms the basis for further CAPRAM mechanism development towards a new version 4.0. Moreover, it can be used as a supplementary tool for aerosol chambers to design and analyse experiments of chemical complexity and help to understand them on a molecular level.

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“…Group contribution factors are able to treat all kinds of hydrocarbons, oxygenated organic compounds, and organics substituted with sulphur, nitrogen, or phosphor species. In a second paper by the same group [104] an automated mechanism generator was introduced to predict the pathways of degradation reactions and determine byproducts for [4] ; * NIST [6] ; * Herrmann, 2003 [7] ChemPhysChem [104] uses object-oriented programming. In this approach each molecule is treated as an object and reacts according to elementary reaction rules.…”

Section: Oh Radicalmentioning

confidence: 99%

Tropospheric Aqueous‐Phase Free‐Radical Chemistry: Radical Sources, Spectra, Reaction Kinetics and Prediction Tools

et al. 2010

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The most important radicals which need to be considered for the description of chemical conversion processes in tropospheric aqueous systems are the hydroxyl radical (OH), the nitrate radical (NO(3)) and sulphur-containing radicals such as the sulphate radical (SO(4)(-)). For each of the three radicals their generation and their properties are discussed first in the corresponding sections. The main focus herein is to summarize newly published aqueous-phase kinetic data on OH, NO(3) and SO(4)(-) radical reactions relevant for the description of multiphase tropospheric chemistry. The data compilation builds up on earlier datasets published in the literature. Since the last review in 2003 (H. Herrmann, Chem. Rev. 2003, 103, 4691-4716) more than hundred new rate constants are available from literature. In case of larger discrepancies between novel and already published rate constants the available kinetic data for these reactions are discussed and recommendations are provided when possible. As many OH kinetic data are obtained by means of the thiocyanate (SCN(-)) system in competition kinetic measurements of OH radical reactions this system is reviewed in a subchapter of this review. Available rate constants for the reaction sequence following the reaction of OH+SCN(-) are summarized. Newly published data since 2003 have been considered and averaged rate constants are calculated. Applying competition kinetics measurements usually the formation of the radical anion (SCN)(2)(-) is monitored directly by absorption measurements. Within this subchapter available absorption spectra of the (SCN)(2)(-) radical anion from the last five decades are presented. Based on these spectra an averaged (SCN)(2)(-) spectrum was calculated. In the last years different estimation methods for aqueous phase kinetic data of radical reactions have been developed and published. Such methods are often essential to estimate kinetic data which are not accessible from the literature. Approaches for rate constant prediction include empirical correlations as well as structure activity relationships (SAR) either with or without the usage of quantum chemical descriptors. Recently published estimation methods for OH, NO(3) and SO(4)(-) radical reactions in aqueous solution are finally summarized, compared and discussed.

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Computerized Pathway Elucidation for Hydroxyl Radical-Induced Chain Reaction Mechanisms in Aqueous Phase Advanced Oxidation Processes

Cited by 35 publications

References 42 publications

Computer-Based First-Principles Kinetic Modeling of Degradation Pathways and Byproduct Fates in Aqueous-Phase Advanced Oxidation Processes

Computer-Based First-Principles Kinetic Modeling of Degradation Pathways and Byproduct Fates in Aqueous-Phase Advanced Oxidation Processes

Development of a protocol for the auto-generation of explicit aqueous-phase oxidation schemes of organic compounds

Tropospheric Aqueous‐Phase Free‐Radical Chemistry: Radical Sources, Spectra, Reaction Kinetics and Prediction Tools

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