Fe(III)-oxalate complexes induced photooxidation of diethylstilbestrol in water

In this work, the photooxidation of diethylstilbestrol (DES), a synthetic estrogen, was investigated in a concentric reactor under a 125 W high-pressure mercury lamp (lambda > or = 365 nm). The photooxidation efficiencies were dependent on the pH values and Fe(III)/oxalate ratios of the system, with higher efficiency at pH 3.50+/-0.05 and Fe(III)/oxalate ratio 10.0/120.0 micromol l(-1). The photooxidation reactions obeyed the law of pseudo-first-order reaction at the concentration over the range of 2.0-10.0 mg l(-1) of DES. The photooxidation rates decreased with increasing the initial concentrations of DES. For 2.0 mg l(-1) DES, the observed photooxidation rate coefficient (k(obs)) was 0.00622 min(-1). By using GC-MS and LC-MS techniques, the predominant photooxidation products DES-o-catechol ([M](+), m/z 284) and DES-4-semiquinone ([M](-), m/z 267) were respectively identified and the mechanisms for the oxidative degradation were proposed. When DES reacted with OH radicals, C atoms in 3-position were added with OH radicals to produce hydrolyzed DES radical followed by two oxidation pathways: (1) dehydrolyzing to produce DES-4-semiquinone which was oxidized further to DES-4,4'-quinone; (2) undergoing peroxidation by O(2) and getting rid of HO(2) radical to produce DES-o-catechol. After that, the two H atoms on the hydroxy group of the catechol were extracted in two individual steps to form intermediates semiquinone radical and o-quinone. The catechol intermediates underwent further oxidation, benzene ring cleavage and decarboxylation, up to mineralization ultimately.     

Mechanisms of molecular product and persistent radical formation from the pyrolysis of hydroquinone

Hydroquinone is considered to be one of the major, potential molecular precursors for semiquinone-type radicals in the combustion of complex polymeric and oligomeric structures contained in biomass materials. Comprehensive product yield determinations from the high-temperature, gas-phase pyrolysis of hydroquinone in two operational modes (rich and lean hydrogen conditions) are reported at a reaction time of 2.0s over a temperature range of 250-1000 degrees C. Below 500 degrees C, p-benzoquinone is the dominant product, while at temperatures above 650 degrees C other products including phenol, benzene, styrene, indene, naphthalene, biphenylene, phenylethyne, dibenzofuran and dibenzo-p-dioxin are formed. Hydrogen-rich conditions initially inhibit hydroquinone decomposition (below 500 degrees C) but promote product formation at higher temperatures. The decomposition process apparently proceeds via formation of a resonance stabilized p-semiquinone radical. Detailed mechanisms of formation of stable molecular species as well as stable radicals are proposed.     

Highly concentrated phenolic wastewater treatment by the photo-Fenton reaction, mechanism study by FTIR-ATR

Phenol degradation by Photo-Fenton reaction has been studied in highly concentrated wastewaters and most intermediate species have been identified by Fourier Transform IR-Spectroscopy with ATR device. During the photodegradation of highly concentrated phenol solutions, the formation of dissolved and precipitate tannin has been observed. The possibility of a Fe3+-Pyrogallol complex formation, previous to the tannin formation, has been proposed too. The complex formation involving Fe3+ ions could be related to the observed Photo-Fenton activity decrease. Tannin formation inhibits the complete mineralization of phenol because *OH radicals attack will produce further condensation steps and the polymer size increase. This fact limits the applicability of the process for highly concentrated phenolic wastes mineralization. However, the tannin precipitation allows its separation from the solution by conventional filtration, and reduction of the corresponding dissolved organic carbon. These observations have been proved from the identification of primary degradation products, catechol and hydroquinone. Catechol is considered to be the first step for the formation of tannins. Degradation process for phenol, catechol and hydroquinone have been monitored by total organic carbon (TOC) measurements along the reaction time span. From these results, a global mechanism for the Photo-Fenton degradation of phenol is proposed.     

Development of expanded and core kinetic models for the gas phase formation of dioxins from chlorinated phenols

Expanded, 45 reaction, and core, 12 reaction, kinetic models have been developed that account for the major features in the homogeneous formation of polychlorinated dibenzo-p-dioxins (PCDD) from the oxidation of 2,4,6-trichlorophenol (P). The expanded and core schemes provide good agreement between experimental and calculated yields of PCDDs using the CHEMKIN combustion package or the React kinetic program, respectively. Steady-state approximations of the reaction kinetic models including radical-molecule and radical-radical formation pathways of PCDD, as well as oxidative destruction pathways of chlorinated phenoxyl radicals, reveal a competition between reactions of chlorinated phenoxyl radicals with chlorinated phenols, recombination reactions of chlorinated phenoxyl mesomers, and destruction/decomposition of phenoxyl radicals.     

Birnessite mediated debromination of decabromodiphenyl ether

Decabromodiphenyl ether (BDE-209) is a major component of a commercial flame retardant formulation; however, there is limited information on the fate of BDE-209 in the environment, including metal oxide mediated degradation. Laboratory experiments were conducted to investigate the birnessite (delta-MnO(2))-promoted debromination of BDE-209 in tetrahydrofuran (THF)-water systems as well as catechol solutions. Up to 100% (0.1044 micromol initial charge) of BDE-209 disappeared upon reaction with birnessite in THF/H(2)O (4:6-9:1). The formation of aqueous Br(-) from BDE-209 reduction was determined and up to 16 mole% of initial bromine was released over the course of the reaction indicating approximately 1.7 Br-C bonds were reduced per BDE-209 molecule. The distribution of debrominated congeners, however, indicated a much greater extent of debromination for some products than what was inferred from an average bromine mass balance. The produced congeners varied from tetra- to nona-bromodiphenyl ether, including BDE-47 and -99, during the 24 h reaction. Experiments with deuterated water indicated that water was not the major hydrogen donor in the reduction but rather THF provided the reducing power. This conclusion was supported by the presence of succinic acid, which was produced from oxidation of THF. The reactions with aqueous catechol, rather than THF-water mixtures, were performed to assess the possible role that compounds found in natural environments, such a tannin-like phenols, might have on the chemistry. These experiments indicated that birnessite mediated debromination of BDE-209 might occur in natural settings.     

Atmospheric Chemistry of Toxic Contaminants. 2. Saturated Aliphatics: Acetaldehyde,Dioxane, Ethylene Glycol Ethers,Propylene Oxide

Detailed mechanisms are outlined for the chemical reactions that contribute to In-situ formation and atmospheric removal of the saturated aliphatic contaminants acetaldehyde, dioxane, ethylene glycol ethers (methyl, ethyl, n-butyl) and propylene oxide. In-situ formation Is of major Importance for acetaldehyde. In-situ removal Involves reaction with OH (all compounds) and, for acetaldehyde, photolysis and reaction with NO3. Acetaldehyde, dioxane, and the ethers are rapidly removed (half-lives of less than one day), leading to PAN (acetaldehyde) and to 2-oxodioxane and formaldehyde (dioxane). Reaction products of the glycol ethers include a large number of hydroxyesters, hydroxyacids, and hydroxycarbonyls. Propylene oxide reacts only slowly with OH, with an atmospheric half-life of 3-10 days, to yield formaldehyde, acetaldehyde, and PAN. Uncertainties in the reaction mechanisms for dioxane, the glycol ethers, and propylene oxide are discussed and include C-C vs C-0 bond scission in alkoxy radicals as well as alkoxy radical unimolecular decomposition vs reaction with oxygen.     

Comparative study of H(2)O(2) and O3 effects on radiation treatment of TCE and PCE

The effects of H(2)O(2) and O(3) on the decomposition of trichloroethylene (TCE) and perchloroethylene (PCE) by gamma-rays (gamma-rays) were investigated in this work. The combined gamma-rays/O(3) process showed a synergistic effect and enhanced the removal of TCE and PCE compared with gamma-rays alone, but, the gamma-rays/H(2)O(2) process did not increase the removal. This interesting result was successfully identified by an electron paramagnetic resonance spectroscopy/spin-trapping method that can quantify hydroxyl radicals, which is directly related to the efficiency of TCE and PCE decomposition. For gamma-rays/H(2)O(2) system, there was no difference of hydroxyl radical production between gamma-rays alone and gamma-rays/H(2)O(2). This indicates gamma-rays cannot activate H(2)O(2) to produce hydroxyl radicals and this causes no increase of TCE and PCE removals. To the contrary, the production of hydroxyl radicals was obviously increased in the case of gamma-rays/O(3) process. This suggests additional hydroxyl radicals are produced from the reaction of O(3) with the irradiation products of water such as hydrated electrons, hydrogen atoms, etc. and this accelerates the removal of TCE and PCE.     

Degradation of anti-inflammatory drug ketoprofen by electro-oxidation: comparison of electro-Fenton and anodic oxidation processes

The electrochemical degradation of the nonsteroidal anti-inflammatory drug ketoprofen in tap water has been studied using electro-Fenton (EF) and anodic oxidation (AO) processes with platinium (Pt) and boron-doped diamond (BDD) anodes and carbon felt cathode. Fast degradation of the parent drug molecule and its degradation intermediates leading to complete mineralization was achieved by BDD/carbon felt, Pt/carbon felt, and AO with BDD anode. The obtained results showed that oxidative degradation rate of ketoprofen and mineralization of its aqueous solution increased by increasing applied current. Degradation kinetics fitted well to a pseudo-first-order reaction. Absolute rate constant of the oxidation of ketoprofen by electrochemically generated hydroxyl radicals was determined to be (2.8?±?0.1)?×?10⁹ M^?1 s^?1 by using competition kinetic method. Several reaction intermediates such as 3-hydroxybenzoic acid, pyrogallol, catechol, benzophenone, benzoic acid, and hydroquinone were identified by high-performance liquid chromatography (HPLC) analyses. The formation, identification, and evolution of short-chain aliphatic carboxylic acids like formic, acetic, oxalic, glycolic, and glyoxylic acids were monitored with ion exclusion chromatography. Based on the identified aromatic/cyclic intermediates and carboxylic acids as end products before mineralization, a plausible mineralization pathway was proposed. The evolution of the toxicity during treatments was also monitored using Microtox method, showing a faster detoxification with higher applied current values.     

Electron paramagnetic resonance (EPR) investigations of lichens – 1: effects of air pollution

Electron paramagnetic resonance (EPR) investigations were carried out on more than 800 samples of lichens from Lower Silesia, southwest Poland. A statistically confirmed correlation between annual average concentration of sulphur dioxide in the atmosphere and concentration of semiquinone radicals in Hypogymnia physodes thalli was found. Similar results were obtained for Umbilicaria species from the Karkonosze Mountains. Distribution of semiquinone radicals in lichen thalli was also investigated. The action of nitrogen dioxide on Umbilicaria species resulted in the synthesis of iminoxy radicals in the thalli. The intensification of the semiquinone free radical production in lichen thalli from atmospherically polluted environments and the degradation of lichen acids to β-diketone compounds would appear to be parallel processes. The properties of the iminoxyls derived from β-diketones in the lichen matrix (anisotropic spectra at room temperature) and in organic solutions after extraction procedure were also examined by EPR.     

Reaction pathways of dimethyl phthalate degradation in TiO2-UV-O2 and TiO2-UV-Fe(VI) systems

The photocatalytic degradation of dimethyl phthalate (DMP) in aqueous TiO₂ suspension under UV illumination has been investigated using oxygen (O₂) and ferrate (Fe(VI)) as electron acceptors. The experiments demonstrated that Fe(VI) was a more effective electron acceptor than O₂ for scavenging the conduction band electrons from the surface of the catalyst. Some major intermediate products from DMP degradation were identified by HPLC and GC/MS analyses. The analytical results identified dimethyl 3-hydroxyphthalate and dimethyl 2-hydroxyphthalate as the two main intermediate products from the DMP degradation in the TiO₂–UV–O₂ system, while in contrast phthalic acid was found to be the main intermediate product in the TiO₂–UV–Fe(VI) system. These findings indicate that DMP degradation in the TiO₂–UV–O₂ and TiO₂–UV–Fe(VI) systems followed different reaction pathways. An electron spin resonance analysis confirmed that hydroxyl radicals existed in the TiO₂–UV–O₂ reaction system and an unknown radical species (most likely an iron–oxo species) is suspected to exist in the TiO₂–UV–Fe(VI) reaction system. Two pathway schemes of DMP degradation in the TiO₂–UV–O₂ and TiO₂–UV–Fe(VI) reaction systems are proposed. It is believed that the radicals formed in the TiO₂–UV–O₂ reaction system preferably attack the aromatic ring of the DMP, while in contrast the radicals formed in the TiO₂–UV–Fe(VI) reaction systems attack the alkyl chain of DMP.     

Effect of chlorides and sulfates on the performance of a Fe3+/H2O2 Fenton-like system in the degradation of methyl tert-butyl ether and its byproducts.

The effect of chloride and sulfate ions on the oxidation of methyl tert-butyl ether (MTBE) and its degradation products in a Fenton-like system was studied. Although both chloride and sulfate ions inhibited the decomposition of H202, chlorides were found to be the more effective inhibitor of MTBE degradation. In the presence of sulfates, MTBE decomposition can be attributed to oxidation not only by hydroxyl radicals, but also likely by SO4*- species. In the presence of chloride ions, it is possible that the dichloride radical is formed, which is less reactive than OH*. In the system under investigation, t-butyl alcohol was found to be the major byproduct, followed by t-butyl formate and acetone. The degradation rates of all intermediates and their inhibition in the presence of inorganic ions are similar to those obtained for MTBE, although their distributions are related to the concentrations of inorganic salts added.     

添加生物油对垃圾焚烧烟气选择性非催化还原脱硝的强化作用及其机理

为揭示添加生物油对垃圾焚烧选择性非催化还原(SNCR)脱硝特性的影响规律及作用机理,利用高温管式炉开展了实验,以研究生物油添加比例(β)、氨氮比(NSR)及氧浓度对SNCR脱硝特性与CO排放的影响;结合SNCR基元反应与生物油热分解产物的成分,分析了添加生物油对烟气选择性非催化还原脱销的强化作用机理。结果表明,添加生物油能拓宽SNCR的温度窗口,在700~900 ℃时可明显提升脱硝效率,当β=10%时,脱硝效率平均提升约21%。在SNCR过程中,CO排放随生物油添加比例的增加而增加,但温度在800 ℃、氧浓度在4%以上时,基本无CO排放。生物油在高温下的分解产物主要为H₂、CO及CH₄等。添加生物油主要通过热分解生成小分子气体,同时产生大量H·、O·、HO₂·及·OH等自由基来强化低温下SNCR脱硝反应。本研究结果表明,在垃圾焚烧电站中,可通过在900 ℃下适当添加生物油来提升SNCR效率。     

Decomposition of gas-phase trichloroethene by the UV/TiO2 process in the presence of ozone.

The decomposition of gas-phase trichloroethene (TCE) in air streams by direct photolysis, the UV/TiO2 and UV/O3 processes was studied. The experiments were carried out under various UV light intensities and wavelengths, ozone dosages, and initial concentrations of TCE to investigate and compare the removal efficiency of the pollutant. For UV/TiO2 process, the individual contribution to the decomposition of TCE by direct photolysis and hydroxyl radicals destruction was differentiated to discuss the quantum efficiency with 254 and 365 nm UV lamps. The removal of gaseous TCE was found to reduce by UV/TiO2 process in the presence of ozone possibly because of the ozone molecules could scavenge hydroxyl radicals produced from the excitation of TiO2 by UV radiation to inhibit the decomposition of TCE. A photoreactor design equation for the decomposition of gaseous TCE by the UV/TiO2 process in air streams was developed by combining the continuity equation of the pollutant and the surface catalysis reaction rate expression. By the proposed design scheme, the temporal distribution of TCE at various operation conditions by the UV/TiO2 process can be well modeled.     

Decomposition and mineralization of cefaclor by ionizing radiation: kinetics and effects of the radical scavengers

There has been recent growing interest in the presence of antibiotics in different environmental sectors. One considerable concern is the potential development of antibiotic-resistant bacteria in the environment, even at low concentrations. Cefaclor, one of the beta-lactam antibiotics, is widely used as an antibiotic. Kinetic studies were conducted to evaluate the decomposition and mineralization of cefaclor using gamma radiation. Cefaclor, 30 mg/l, was completely degraded with 1,000 Gy of gamma radiation. At a concentration of 30 mg/l, the removal efficiency, represented by the G-value, decreased with increasing accumulated radiation dose. Batch kinetic experiments with initial aqueous concentrations of 8.9, 13.3, 20.0 and 30.0mg/l showed the decomposition of cefaclor using gamma radiation followed a pseudo first-order reaction, and the dose constant increased with lower initial concentrations. At a given radiation dose, the G-values increased with higher initial cefaclor concentrations. The experimental results using methanol and thiourea as radical scavengers indicated that ()OH radicals were more closely associated with the radiolytic decomposition of cefaclor than other radicals, such as e(aq)(-) or ()H. The radical scavenger effects were tested under O(2) and N(2)O saturations for the enhancement of the TOC percentage removal efficiencies in the radiolytic decomposition of cefaclor. Under O(2) saturation, 90% TOC removal was observed with 100,000 Gy. Oxygen is well known to play a considerable role in the degradation of organic substances with effective chain reaction pathways. According to the effective radical reactions, the enhanced TOC percentage removal efficiencies might be based on the fast conversion reactions of e(aq)(-) and ()H with O(2) into oxidizing radicals, such as O(2)(-) and HO(2)(), respectively. 100% TOC removal was obtained with N(2)O gas at 20,000 Gy, as reducing radicals, such as e(aq)(-) and ()H, are scavenged by N(2)O and converted into ()OH radicals, which have strong oxidative properties. The results of this study showed that gamma irradiation was very effective for the removal of cefaclor in aqueous solution. The use of O(2) or N(2)O, with radiation, shows promise as effective radical scavengers for enhancing the TOC or COD removal efficiencies in pharmaceutical wastewaters containing antibiotics. However, the biological toxicity and interactions between various chemicals during the radiolytic treatment, as well as treatments under conditions more representative of real wastewater will require further studies.     

聚多巴胺/聚乙烯亚胺复合非织造布/Fe2+活化过硫酸盐催化氧化酸性红B的效果分析

以聚丙烯(PP)非织造布为基体,采用多巴胺聚乙烯亚胺共沉积法制备了聚多巴胺/聚乙烯亚胺复合非织造布(PDA/PEI@PP),研究了PDA/PEI@PP在Fe²⁺活化过硫酸盐(PS)降解酸性红B(ARB)的中的性能和反应机理。通过SEM对材料结构进行了表征,考察了不同体系(PS、PDA/PEI@PP/PS、Fe²⁺/PS和PDA/PEI@PP/Fe²⁺/PS)中ARB的降解效果,通过电子自旋共振波谱(ESR)和傅里叶红外光谱(FT-IR)分析了PDA/PEI@PP活化PS及自由基生成的机理,此外,考察了PDA/PEI@PP对Fe³⁺的还原作用。结果表明：PDA/PEI@PP非织造材料具有贯穿的孔道结构,利于PDA/PEI@PP表面官能团对PS的活化;PDA/PEI@PP对Fe²⁺/PS体系的催化氧化具有促进作用,当Fe²⁺初始浓度为0.5 mmol·L⁻¹时,90 min内对ARB的降解率为98%,反应速率常数为0.040 min⁻¹;在不添加Fe²⁺的情况下,PDA/PEI@PP可直接活化PS产生自由基降解ARB,降解率为56%;PDA/PEI@PP表面的邻苯二酚基团与邻醌基反应生成半醌,从而活化PS产生硫酸根自由基($ {\rm{SO}}_4^{ \cdot - } $)和羟基自由基(·OH);同时PDA/PEI@PP表面的邻苯二酚基团也对Fe³⁺具有还原作用,生成Fe²⁺持续活化PS。因此,PDA/PEI@PP对于Fe²⁺活化PS的促进作用主要是通过PDA/PEI@PP对PS协同活化和对Fe³⁺的还原作用来实现的。本研究为进一步提高Fe²⁺活化PS氧化降解染料废水的效率提供了一种较好的解决方案。     

Photocatalytic oxidation of monuron in the suspension of WO3 under the irradiation of UV-visible light

A comprehensive study of the degradation of monuron, one of the phenylurea herbicides, was conducted by UV-Vis/WO₃ process. It was found that hydroxyl radicals played a major role in the decay of monuron while other radicals (e.g. superoxide) and hole might also contribute to the decomposition of monuron. The oxidation path likely plays a major role in the generation of hydroxyl radicals. The effects of initial pH level, initial concentration of monuron, and inorganic oxidants on the performance of UV-Vis/WO₃ process were also investigated and optimized. Comparison between monuron decay pathways by UV-Vis/WO₃ and UV/TiO₂ was conducted. The decay mechanisms, including N-terminus demethylation, dechlorination and direct hydroxylation on benzene ring, were observed to be involved in the oxidation of monuron in these two processes. Sixteen intermediates were identified during the photodegradation of monuron and degradation pathways were proposed accordingly.     

Atmospheric degradation of alkylfurans with chlorine atoms: Product and mechanistic study

As part of a study on the oxidation mechanism of heterocyclic aromatic compounds, some aspects of the atmospheric chemistry of several alkyl derivatives of furan have been investigated. The aim of this work was to identify the products of the reactions of chlorine atoms with 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran. Experiments were performed in two different smog chambers at 296 ± 2 K and 1000 ± 20 mbar of synthetic air. The experimental investigation was carried out using in situ long-path FTIR absorption spectroscopy and both SPME-GC/FID-ECD and SPME-GC/MS as sampling and detection techniques. The major primary products from the addition reaction channel were 4-oxo-2-pentenoyl chloride and formaldehyde for the reactions of 2-methylfuran and 2,5-dimethylfuran; 4-oxo-2-hexenoyl chloride and acetaldehyde for the reaction of 2-ethylfuran and 5-chloro-2(5H)-furanone for the reactions of both 2-methylfuran and 2-ethylfuran. Other minor products were 4-oxo-2-pentenal, 4-oxo-2-hexenal and 3-hexene-2,5-dione for the 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran reactions, respectively. From the abstraction pathway, HCl, furfural, 2-acetylfuran, 5-methylfurfural, maleic anhydride and 5-hydroxy-2(5H)-furanone were detected. The formation of furfural, 2-acetylfuran and 5-methylfurfural confirmed the H-atom abstraction from the alkyl group of 2-methylfuran, 2-ethylfuran and 2,5-dimethylfuran, respectively. This mechanism was not observed in previous studies with OH and NO₃ radicals. A mechanism is proposed to explain the main reaction products observed. The observed products confirm that addition of Cl atoms to the double bond of the alkylfuran is the dominant reaction pathway.     

Heterogeneous light-induced ozone processing on the organic coatings in the atmosphere

Many of the more recent studies concerning heterogeneous reactions of atmospheric interest, carry, in some cases, much more details but still follow the basic philosophy of the first pioneering studies. Therefore, in this study the accent is put on the additional complexities that arise when the aerosols of interest have more complex compositions. Hence, it is attempted to identify the products following the simultaneous ozone processing and light irradiation on particles coated with 4-phenoxyphenol in the presence of 4-carboxybenzophenone as a photosensitizer. In order to reveal a more complete picture on the fate of these aromatic compounds under controlled experimental conditions, different analytical tools such as gas chromatography coupled to mass spectrometry (GC–MS) and proton transfer reaction-mass spectrometry (PTR-MS) have been applied.Several surface bound products were identified via GC–MS and some of them (phenol, hydroquinone, catechol, 4-hydroxybenzoic acid, benzoic acid, fumaric acid, terephthalic acid, maleic acid, 1,2,4-trihydroxybenzene and 4,4′-oxydiphenol) confirmed with standards. The main volatile secondary products as identified by PTR-MS in this study were formic acid, phenol and p-benzoquinone.A reaction mechanism was proposed and density functional theory calculations were performed in order to elucidate the initial steps of the ozonolysis reaction on 4-phenoxyphenol in the presence of 4-carboxybenzophenone.     

Mineralization of CCl4 by the UVC-photolysis of hydrogen peroxide in the presence of methanol

A method for a photochemically induced mineralization of CCl4 is described in which use is made of reductive radicals. The UVC-photolysis (254 nm) of H2O2 added to aqueous solutions of CCl4 is leading to the homolysis of the oxidant yielding hydroxyl radicals (HO) that subsequently react with added methanol to generate hydroxymethyl radicals (CH2OH). The latter radicals initiate mineralization of CCl4 by reductive C-Cl bond splitting. CHCl3, C2Cl4 and C2Cl6 were found as reaction intermediates, but are quantitatively depleted in a parallel oxidative reaction manifold leading to mineralization. Carbon dioxide radical anion, CO2(-), an intermediate in the mineralization pathway of methanol, is also shown to initiate the mineralization of CCl4 by reductive dechlorination. A reaction mechanism is proposed and validated with computer simulations of all the experimental results.     

汽车尾气中NO_X再燃烧过程的动力学

为了阐明汽车尾气中 NOX再燃烧的动力学进程 ,以甲醛和 NO2 作为探针分子 ,通过 FT-IR跟踪研究了反应体系中所产生的 HCO自由基与 NO2 反应的动力学。结果表明 ,反应的主要产物中包括 CO、CO2 、NO、HONO和 H2 O等分子 ,经长时间的反应 ,当体系中的 NO2 基本耗尽时 ,才有少量的 N2 O生成。这些产物分子分别是在几个不同途径的连串反应中形成的。从体系中 CO和 CO2 的生成量 ,测定了主反应的歧化反应速率比 ,并对相应的动力学机理进行了讨论。