Study on the reaction of 3-methyl-2-butenal and 3-methylbutanal with Cl atoms: kinetics and reaction mechanism

The reaction of Cl atoms with two C₅ aldehydes (3-methyl-2-butenal and 3-methylbutanal) were investigated by proton-transfer-reaction mass spectrum (PTR-MS) using smog chamber at 298 ± 1 K and 760 Torr. A relative rate method was used to determine the rate constants of the title reactions with m-xylene and trans-2-butene as reference compounds: (3.04 ± 0.18)  ×  10⁻¹⁰ and (2.07 ± 0.14)  ×  10⁻¹⁰ cm³/(molecule⋅sec) for 3-methyl-2-butenal and 3-methylbutanal, respectively. Additionally, the gas-phase products were also identified by PTR-MS, and the possible reaction mechanisms were proposed basing on the identified products. The detected gas-phase products are similar for two C₅ aldehydes reactions, mainly including small molecules of aldehydes, ketones and chlorinated aldehyde compounds. The atmospheric lifetimes (τ) calculated for 3-methyl-2-butenal (τ = 7.0 hr, marine boundary layer (MBL)) and 3-methylbutanal (τ = 10.3 hr, MBL) according to the obtained rate constants. The results indicate that Cl atoms at MBL are competitive with OH radicals for the degradation contribution of C₅ aldehyde compounds.     

Review of technologies and their applications for the speciated detection of RO2 radicals

Peroxy radicals (RO₂), which are formed during the oxidation of volatile organic compounds, play an important role in atmospheric oxidation reactions. Therefore, the measurement of RO₂, especially distinct species of RO₂ radicals, is important and greatly helps the exploration of atmospheric chemistry mechanisms. Although the speciated detection of RO₂ radicals remains challenging, various methods have been developed to study them in detail. These methods can be divided into spectroscopy and mass spectrometry technologies. The spectroscopy methods contain laser-induced fluorescence (LIF), UV-absorption spectroscopy, cavity ring-down spectroscopy (CRDS) and matrix isolation and electron spin resonance (MIESR). The mass spectrometry methods contain chemical ionization atmospheric pressure interface time-of-flight mass spectrometry (CI-APi-TOF), chemical ionization mass spectrometry (CIMS), CI-Orbitrap-MS and the third-generation proton transfer reaction–time-of-flight mass spectrometer (PTR3). This article reviews technologies for the speciated detection of RO₂ radicals and the applications of these methods. In addition, a comparison of these techniques and the reaction mechanisms of some key species are discussed. Finally, possible gaps are proposed that could be filled by future research into speciated RO₂ radicals.     

CaCO3类吸收剂净化焚烧烟气中HCI气体的研究

通常烟气中的酸性气体采用Ca（OH）2净化，然而当烟气温度在300℃以上时，Ca（OH）2喷入到烟气中将快速生成CaCO3。研究了两种CaCO3的反应特性，比较了200-900℃内CaCO3类吸收剂和Ca（OH）2与烟气中HCl气体的反应率，发现在600℃左右和800℃及以上，CaCO3类吸收剂的反应率与Ca（OH）2相当或更高；CaCO3类吸收剂、特别是改性CaCO3可替代Ca（OH）2作为干式净化HCl气体的吸收剂，合适的反应温度在600℃左右。     

Catalytic wet air oxidation of phenol with functionalized carbon materials as catalysts：Reaction mechanism and pathway

The development of highly active carbon material catalysts in catalytic wet air oxidation（CWAO）has attracted a great deal of attention. In this study different carbon material catalysts（multi-walled carbon nanotubes,carbon fibers and graphite） were developed to enhance the CWAO of phenol in aqueous solution. The functionalized carbon materials exhibited excellent catalytic activity in the CWAO of phenol. After 60 min reaction,the removal of phenol was nearly100% over the functionalized multi-walled carbon,while it was only 14% over the purified multi-walled carbon under the same reaction conditions. Carboxylic acid groups introduced on the surface of the functionalized carbon materials play an important role in the catalytic activity in CWAO. They can promote the production of free radicals,which act as strong oxidants in CWAO. Based on the analysis of the intermediates produced in the CWAO reactions,a new reaction pathway for the CWAO of phenol was proposed in this study. There are some differences between the proposed reaction pathway and that reported in the literature. First,maleic acid is transformed directly into malonic acid. Second,acetic acid is oxidized into an unknown intermediate,which is then oxidized into CO2 and H2O. Finally,formic acid and oxalic acid can mutually interconvert when conditions are favorable.     

Evaluation of municipal solid waste composting kinetics

Most modern municipal solid waste (MSW) composting operations have emphasized the enhancement of decomposition of the organic fraction of the waste to comply with strict environmental regulations. This can be achieved once the composting process kinetics are well understood. This study examined process kinetics through experimentation with bench-scale reactors under controlled composting conditions to show the interdependence between biological, chemical and physical factors during composting of MSW. The effects of temperature, moisture content, waste particle size and carbon to nitrogen (C/N) ratio on process kinetics were evaluated. The results obtained revealed that these factors should be carefully controlled in order to achieve optimum process performance. It has been found that the organic matter degradation during composting follows a first-order kinetic model.     

河水BOD1～20与反应速率常数K的初探

实验证明，由于无锡水域中硝化菌的存在，使ＢＯＤ硝化阶段大为提前。因此当水体含氮有机物丰富时，硝化因素应予以重视。     

Use of silicon and ferrosilicon industry by-products (silica fume) in cement paste and mortar

With increased environmental awareness, recycling/utilization of industrial byproducts is gaining ground. One such by-product is silica fume (SF), which is byproduct of the smelting process in the silicon and ferrosilicon industry. By-products of the production of silicon metal and the ferrosilicon alloys having silicon contents of 75% or more contain 85-95% non crystalline silica. Silica fume is very useful in the design and development of high quality cement paste/mortar and concrete.This paper presents comprehensive details of the physical, chemical, properties, and its reaction mechanism. It also covers the hydration characteristics, consistency, setting times, workability and compressive strength of cement paste and mortar.     

Recent trends in the decomposition of chlorinated aromatic hydrocarbons by ultrasound irradiation and Fenton's reagent

Over the past few years, a large number of studies have been conducted on the use of ultrasound for decomposition of harmful organic pollutants, particularly chlorinated aromatic hydrocarbons (CAH) in wastewater. The published reports cover a variety of applications, including both ultrasonic treatment alone and in combination with other methods, e.g., advanced chemical oxidation processes. This article presents a review of recent work on ultrasonic-based methods of CAH decomposition, with emphasis on the applications of ultrasound alone and in combination with Fenton's reagent, as attractive advanced oxidation systems. In the first part of this review, the basic principles of sonochemical treatment are presented, followed by a review of the applications of ultrasound alone for CAH degradation. In the second part, the mechanisms of CAH degradation with Fenton's reagent and its application for CAH degradation are summarized. In the final part, studies on the applications of ultrasound together with Fenton's reagent are reviewed. The reported results suggest that a combination of ultrasound and Fenton's reagent is more attractive for practical application than the use of either method separately. Further studies, however, are required in this area because the reaction mechanism and the relationship between the reaction rates and process parameters for such a combined process are not yet well established.     

Numerical methods for improving sensitivity analysis and parameter estimation of virus transport simulated using sorptive-reactive processes

Using one- and two-dimensional homogeneous simulations, this paper addresses challenges associated with sensitivity analysis and parameter estimation for virus transport simulated using sorptive-reactive processes. Head, flow, and conservative- and virus-transport observations are considered. The paper examines the use of (1) observed-value weighting, (2) breakthrough-curve temporal moment observations, and (3) the significance of changes in the transport time-step size. The results suggest that (1) sensitivities using observed-value weighting are more susceptible to numerical solution variability, (2) temporal moments of the breakthrough curve are a more robust measure of sensitivity than individual conservative-transport observations, and (3) the transport-simulation time step size is more important than the inactivation rate in solution and about as important as at least two other parameters, reflecting the ease with which results can be influenced by numerical issues. The approach presented allows more accurate evaluation of the information provided by observations for estimation of parameters and generally improves the potential for reasonable parameter-estimation results.     

2．4－二硝基甲苯在水中的光化学反应

本文研究了２．４－二硝基甲苯在纯水、江水、含腐殖质纯水及合过氧化氢纯水中的光化学反应．结果表明：在影响２．４－二硝基甲苯光化学反应的因素中，过氧化氢影响最大，腐殖质次之，ｐＨ值影响最小．研究了２．４－二硝基甲苯在江水、含腐殖质纯水及合过氧化氢的纯水中光化学反应的机理．应用高压液相色谱鉴定了中间产物２．４－二硝基苯甲酸的存在．表明２．４－二硝基甲苯的光化学反应为侧链甲基光化学反应．