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Reduction kinetics of SrFeO/CaO∙MnO nanocomposite as effective oxygen carrier for chemical looping partial

《化学科学与工程前沿（英文）》 2022年 第16卷 第12期   页码 1726-1734 doi: 10.1007/s11705-022-2188-5

摘要： Chemical looping reforming of methane is a novel and effective approach to convert methane to syngas, in which oxygen transfer is achieved by a redox material. Although lots of efforts have been made to develop high-performance redox materials, a few studies have focused on the redox kinetics. In this work, the kinetics of SrFeO3−δ–CaO∙MnO nanocomposite reduction by methane was investigated both on a thermo-gravimetric analyzer and in a packed-bed microreactor. During the methane reduction, combustion occurs before the partial oxidation and there exists a transition between them. The weight loss due to combustion increases, but the transition region becomes less inconspicuous as the reduction temperature increased. The weight loss associated with the partial oxidation is much larger than that with combustion. The rate of weight loss related to the partial oxidation is well fitted by the Avrami–Erofeyev equation with n = 3 (A3 model) with an activation energy of 59.8 kJ∙mol‒1. The rate law for the partial oxidation includes a solid conversion term whose expression is given by the A3 model and a methane pressure-dependent term represented by a power law. The partial oxidation is half order with respect to methane pressure. The proposed rate law could well predict the reduction kinetics; thus, it may be used to design and/or analyze a chemical looping reforming reactor.

关键词： chemical looping reforming     SrFeO3−δ/CaO·MnO nanocomposite     reduction kinetics     Avrami–Erofeyev model     pressure-dependent term    

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Performance and kinetics of iron-based oxygen carriers reduced by carbon monoxide for chemical looping

Xiuning HUA,Wei WANG,Feng WANG

《环境科学与工程前沿（英文）》 2015年 第9卷 第6期   页码 1130-1138 doi: 10.1007/s11783-015-0821-y

摘要： Chemical looping combustion is a promising technology for energy conversion due to its low-carbon, high-efficiency, and environmental-friendly feature. A vital issue for CLC process is the development of oxygen carrier, since it must have sufficient reactivity. The mechanism and kinetics of CO reduction on iron-based oxygen carriers namely pure Fe O and Fe O supported by alumina (Fe O /Al O ) were investigated using thermo-gravimetric analysis. Fe O /Al O showed better reactivity over bare Fe O toward CO reduction. This was well supported by the observed higher rate constant for Fe O /Al O over pure Fe O with respective activation energy of 41.1±2.0 and 33.3±0.8 kJ·mol . The proposed models were compared via statistical approach comprising Akaike information criterion with correction coupled with F-test. The phase-boundary reaction and diffusion control models approximated to 95% confidence level along with scanning electron microscopy results; revealed the promising reduction reactions of pure Fe O and Fe O /Al O . The boosting recital of iron-based oxygen carrier support toward efficient chemical looping combustion could be explained accurately through the present study.

关键词： chemical looping combustion     iron-based oxygen carriers     reduction kinetics     carbon monoxide     statistics    

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Kinetics of hexavalent chromium reduction by iron metal

QIAN Huijing, WU Yanjun, LIU Yong, XU Xinhua

《环境科学与工程前沿（英文）》 2008年 第2卷 第1期   页码 51-56 doi: 10.1007/s11783-008-0010-3

摘要： The kinetics of Cr(VI) reduction to Cr(III) by metallic iron (Fe) was studied in batch reactors for a range of reactant concentrations, pH and temperatures. Nearly 86.8% removal efficiency for Cr(VI) was achieved when Fe concentration was 6 g/L (using commercial iron powder (< 200 mesh) in 120 min). The reduction of hexavalent chromium took place on the surface of the iron particles following pseudo-first order kinetics. The rate of Cr(VI) reduction increased with increasing Fe addition and temperature but inversely with initial pH. The pseudo-first-order rate coefficients () were determined as 0.0024, 0.010, 0.0268 and 0.062 8 min when iron powder dosages were 2, 6, 10 and 14 g/L at 25°C and pH 5.5, respectively. According to the Arrehenius equation, the apparent activation energy of 26.5 kJ/mol and pre-exponential factor of 3 330 min were obtained at the temperature range of 288–308 K. Different Fe types were compared in this study. The reactivity was in the order starch-stabilized Fe nanoparticles > Fe nano-particles > Fe powder > Fe filings. Electrochemical analysis of the reaction process showed that Cr(III) and Fe(III) hydroxides should be the dominant final products.

关键词： Different     process     surface     Electrochemical analysis     concentration    

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Redox reactions of iron and manganese oxides in complex systems

Jianzhi Huang, Huichun Zhang

《环境科学与工程前沿（英文）》 2020年 第14卷 第5期 doi: 10.1007/s11783-020-1255-8

摘要： • Mechanisms of redox reactions of Fe- and Mn-oxides were discussed. • Oxidative reactions of Mn- and Fe-oxides in complex systems were reviewed. • Reductive reaction of Fe(II)/iron oxides in complex systems was examined. • Future research on examining the redox reactivity in complex systems was suggested. Conspectus Redox reactions of Fe- and Mn-oxides play important roles in the fate and transformation of many contaminants in natural environments. Due to experimental and analytical challenges associated with complex environments, there has been a limited understanding of the reaction kinetics and mechanisms in actual environmental systems, and most of the studies so far have only focused on simple model systems. To bridge the gap between simple model systems and complex environmental systems, it is necessary to increase the complexity of model systems and examine both the involved interaction mechanisms and how the interactions affected contaminant transformation. In this Account, we primarily focused on (1) the oxidative reactivity of Mn- and Fe-oxides and (2) the reductive reactivity of Fe(II)/iron oxides in complex model systems toward contaminant degradation. The effects of common metal ions such as Mn2+ , Ca2+, Ni2+, Cr3+ and Cu2+, ligands such as small anionic ligands and natural organic matter (NOM), and second metal oxides such as Al, Si and Ti oxides on the redox reactivity of the systems are briefly summarized.

关键词： Iron oxides     manganese oxides     reduction     oxidation     complex systems     reaction kinetics and mechanisms    

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Theoretical insights into influence of additives on sulfamethoxazole crystal growth kinetics and mechanisms

《化学科学与工程前沿（英文）》 2023年 第17卷 第10期   页码 1503-1515 doi: 10.1007/s11705-022-2294-4

摘要： In this work, the influence of the initial chemical potential gradient, stirring speed, and polymer type on sulfamethoxazole (SMX) crystal growth kinetics was systematically investigated through density functional theory (DFT) calculations, experimental measurements and the two-step chemical potential gradient model. To investigate the influence of different conditions on the thermodynamic driving force of SMX crystal growth, SMX solubilities in different polymer solutions were studied. Four model polymers effectively improved SMX solubility. It was further found that polyvinylpyrrolidone (PVP) and hydroxypropyl methyl cellulose (HPMC) played a crucial role in inhibiting SMX crystal growth. However, polyethylene glycol (PEG) promoted SMX crystal growth. The effect of the polymer on the crystal growth mechanisms of SMX was further analyzed by the two-step chemical potential gradient model. In the system containing PEG 6000, crystal growth is dominated by the surface reaction. However, in the system containing PEG 20000, crystal growth is dominated by both the surface reaction and diffusion. In addition, DFT calculations results showed that HPMC and PVP could form strong and stable binding energies with SMX, indicating that PVP and HPMC had the potential ability to inhibit SMX crystal growth.

关键词： insoluble drugs     polymer     inhibition crystallization     crystal growth kinetics     DFT calculations    

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Combustion characteristics and kinetics of bio-oil

Ruixia ZHANG, Zhaoping ZHONG, Yaji HUANG

《化学科学与工程前沿（英文）》 2009年 第3卷 第2期   页码 119-124 doi: 10.1007/s11705-009-0068-x

摘要： The combustion characteristics of bio-oils derived from rice husk and corn were studied by thermogravimetry analysis. According to the thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA) curves of bio-oils in air and nitrogen atmosphere, we analyzed the combustion characteristics of different kinds of bio-oils in different atmospheres and worked out the combustion kinetics parameters of the bio-oil, providing reliable base data for the burning of bio-oil. The thermogravimetry indicated that the combustion process of bio-oil was divided into three stages. At the same time, the combustion process can be described by different order reaction models, and with the method of Coats-Redfern, the activation energy and frequency factor of different kinds of bio-oils were obtained.

关键词： bio-oil     combustion characteristics     combustion kinetics    

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Thermal degradation kinetics and lifetime estimation for polycarbonate/polymethylphenylsilsesquioxane

Jiangbo WANG, Zhong XIN

《化学科学与工程前沿（英文）》 2009年 第3卷 第2期   页码 167-171 doi: 10.1007/s11705-009-0006-y

摘要： The thermal degradation behaviors of polycarbonate/polymethylphenylsilsesquioxane (FRPC) composites were investigated by thermogravimetric analysis (TGA) under isothermal conditions in nitrogen atmosphere. The isothermal kinetics equation was used to describe the thermal degradation process. The results showed that activation energy ( ), in the case of isothermal degradation, was a quick increasing function of conversion (α) for polycarbonate (PC) but was a strong and decreasing function of conversion for FRPC. Under the isothermal condition, the addition of polymethylphenylsilsesquioxane (PMPSQ) retardanted the thermal degradation and enhanced the thermal stability of PC during the early and middle stages of thermal degradation. It also indicated a possible existence of a difference in nucleation, nuclei growth, and gas diffusion mechanism in the thermal degradation process between PC and FRPC. Meanwhile, the addition of PMPSQ influenced the lifetime of PC, but the composite still met the demand in manufacturing and application.

关键词： polycarbonate     polymethylphenylsilsesquioxane     thermal degradation kinetics     activation energy     lifetime    

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Modeling the aqueous reaction kinetics of estriol with ferrate

Cong LI, Naiyun GAO

《化学科学与工程前沿（英文）》 2009年 第3卷 第1期   页码 39-45 doi: 10.1007/s11705-009-0098-4

摘要： In this study the aqueous oxidation kinetics of estriol (E3) by potassium ferrate (K FeO ), a chemical for its strong oxidizing power and for producing a coagulant from its reduced state (i.e. Fe(III)), was evaluated in the range of pH 8-12 with different molar ratios of the reactants. As the degree of Fe(VI) protonation varies with the solution pH, it was found that a first order model was not suitable to describe the oxidation reaction. This paper describes a theoretical representation that closely models the reaction kinetics of E3 and ferrate. From this modeling, the reaction rates of HFe and Fe with E3 have been determined. The results show that the reactivity of HFe with dissociated and undissociated E3 is greater than that of Fe , and that E3 is more reactive in its dissociated state.

关键词： ferrate     estriol     endocrine disruptor     kinetics     oxidation    

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Influence of extracellular polymeric substances from activated sludge on the aggregation kinetics of

《环境科学与工程前沿（英文）》 2022年 第16卷 第2期 doi: 10.1007/s11783-021-1450-2

摘要：

• The NPs aggregation in the electrolyte solution is consistent with the DLVO theory.

关键词： Silver nanoparticles     Silver sulfide nanoparticles     Extracellular polymeric substances     Aggregation kinetics     Influence mechanisms    

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Preparation and crystallization kinetics of micron-sized Mg(OH)

Xingfu SONG, Kefeng TONG, Shuying SUN, Ze SUN, Jianguo YU

《化学科学与工程前沿（英文）》 2013年 第7卷 第2期   页码 130-138 doi: 10.1007/s11705-013-1332-7

摘要： Magnesium hydroxide is an important chemical, and is usually obtained from seawater or brine via precipitation process. The particle size distribution of magnesium hydroxide has great effects on the subsequent filtration and drying processes. In this paper, micron-sized magnesium hydroxide with high purity, large particle size and low water content in filter cake was synthesized via simple wet precipitation in a mixed suspension mixed product removal (MSMPR) crystallizer. The effects of reactant concentration, residence time and impurities on the properties of magnesium hydroxide were investigated by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Malvern laser particle size analyzer. The results show that NaOH concentration and residence time have great effects on the water content and particle size of Mg(OH) . The spherical Mg(OH) with uniform diameter of about 30 μm was obtained with purity higher than 99% and water content less than 31%. Furthermore, the crystallization kinetics based on the population balance theory was studied to provide the theoretical data for industrial enlargement, and the simulation coefficients ( ) based on ASL model and C-R model are 0.9962 and 0.9972, respectively, indicating that the crystal growth rate of magnesium hydroxide can be well simulated by the size-dependent growth models.

关键词： magnesium hydroxide     precipitation     micron-sized     crystallization kinetics    

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Intrinsic kinetics and external diffusion of catalytic steam gasification of fine coal char particles

Xuantao Wu, Jie Wang

《化学科学与工程前沿（英文）》 2019年 第13卷 第2期   页码 415-426 doi: 10.1007/s11705-018-1725-8

摘要： Catalytic steam gasification of fine coal char particles was carried out using a self-made laboratory reactor to determine the intrinsic kinetics and external diffusion under varying pressures (0.1–0.5 MPa) and superficial gas flow velocities (GFVs) of 13.8–68.8 cm?s . In order to estimate the gas release rate at a low GFV, the transported effect of effluent gas on the temporal gasification rate pattern was simulated by the Fluent computation and verified experimentally. The external mass transfer coefficients ( ) and the effectiveness factors were determined at lower GFVs, based on the intrinsic gasification rate obtained at a high GFV of 55.0 cm?s . The was found to be almost invariable in a wider carbon conversion of 0.2–0.7. The variations of at a median carbon conversion with GFV, temperature and pressure were found to follow a modified Chilton-Colburn correlation: (0.04< <0.19), where is total pressure and is atmospheric pressure. An intrinsic kinetics/external diffusion integrating model could well describe the gasification rate as a function of GFV, temperature and pressure over a whole gasification process.

关键词： coal char     catalytic steam gasification     pressure     kinetics     diffusion    

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Determination of growth kinetics of microorganisms linked with 1,4-dioxane degradation in a consortium

《环境科学与工程前沿（英文）》 2022年 第16卷 第5期 doi: 10.1007/s11783-022-1567-y

摘要：

● Evaluated three methods for determining the consortia’s growth kinetics.

关键词： Biodegradation     1     4-Dioxane     Kinetics     Microbial consortium     16S rRNA    

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Removal of Rhodamine B from aqueous solutions and wastewater by walnut shells: kinetics, equilibrium

Jasmin Shah, M. Rasul Jan, Attaul Haq, Younas Khan

《化学科学与工程前沿（英文）》 2013年 第7卷 第4期   页码 428-436 doi: 10.1007/s11705-013-1358-x

摘要： An adsorption study of Rhodamine B (RB) dye from aqueous solutions was carried out using walnut shells pretreated by different methods. In addition to the effects of the pretreatment, the effects of various parameters like pH, adsorbent dose, contact time, initial dye concentration and temperature on the adsorption of RB was studied. The adsorption process was highly pH dependent and a maximum adsorption was achieved at pH 3.0. The best fit for the rates of dye adsorption was a pseudo-second-order kinetic model with good correlation coefficients ( >0.99). Langmuir isotherms were used to determine that the maximum loading capacity of the different walnut shells and the RB capacities ranged from 1.451–2.292 mg·g . The dye adsorption was also evaluated thermodynamically. Positive standard enthalpy (? °) values were obtained indicating that the RB adsorption process is endothermic as well as ? ° and ? ° values showed that adsorption process is spontaneous with an increased randomness at the solid-liquid interface. Desorption studies were carried out to explore the feasibility of regenerating the used walnut shells and it was found that 97.71%–99.17% of the retained RB was recovered with 0.1 mol?L NaOH solution. The walnut shells were also successfully used to remove RB from industrial effluents.

关键词： Rhodamine B     walnut shell adsorption     kinetics     isotherms     regeneration    

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Ozone kinetics of dimethyl sulfide in the presence of water vapor

Haitao WANG

《环境科学与工程前沿（英文）》 2013年 第7卷 第6期   页码 833-835 doi: 10.1007/s11783-013-0570-8

摘要： The outdoor smog chamber was used to thorough investigate the rate constants of gas-phase reaction between dimethyl sulfide (DMS) and ozone (O ) under conditions of relative humidity 55.0%–67.8% at (296±2)K for the first time. The rate constants were measured, at a total pressure of 1 atm, to be (10.4±0.2) × 10 cm ·molecule ·s at relative humidity of 67.5%±0.3% at 298K, (10.1±0.1) × 10 cm ·molecule ·s at relative humidity of 66.5%±0.5% at 296K, (7.75±0.39) × 10 cm ·molecule ·s at relative humidity of 64.8%±0.1% at 294K and (3.42±0.21) × 10 cm ·molecule ·s at relative humidity of 55.8%±0.8% at 295K. Base on these results, it is possible to see the reaction of O /DMS in the presence of water vapor as an important sink for DMS in the earth atmosphere.

关键词： rate constants     ozone (O3)     dimethyl sulfide (DMS)     water vapor    

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Numerical investigation of the influence of kinetics and shape factor on barium sulfate precipitation

Zheng WANG, Zai-Sha MAO, Chao YANG, Qinghua ZHANG, Jingcai CHENG

《化学科学与工程前沿（英文）》 2009年 第3卷 第3期   页码 272-281 doi: 10.1007/s11705-009-0023-x

摘要： The effect of kinetics and shape factor on barium sulfate precipitation in a continuous stirred tank has been investigated numerically through solving the standard momentum and mass transport equations in combination with the moment equations for crystal population balance. The numerical method was validated with the literature data. The simulated results include the distribution of the local supersaturation ratio in the reactor, the mean crystal size, and the coefficient of variation. The simulation results show that the value of shape factor used in the model affected greatly the mean crystal size and the moments of the crystal size distribution. The influence of the kinetic expressions on the simulation is also analyzed. It is important to investigate the relationship of the shape factor with the precipitator type and other operation conditions to obtain reliable simulation results and suitable kinetic equations of crystal nucleation and growth rates.

关键词： stirred tank     numerical simulation     precipitation     shape factor     crystal kinetics    

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标题 作者 时间 类型 操作

Reduction kinetics of SrFeO/CaO∙MnO nanocomposite as effective oxygen carrier for chemical looping partial

期刊论文

Performance and kinetics of iron-based oxygen carriers reduced by carbon monoxide for chemical looping

Xiuning HUA,Wei WANG,Feng WANG

期刊论文

Kinetics of hexavalent chromium reduction by iron metal

QIAN Huijing, WU Yanjun, LIU Yong, XU Xinhua

期刊论文

Redox reactions of iron and manganese oxides in complex systems

Jianzhi Huang, Huichun Zhang

期刊论文

Theoretical insights into influence of additives on sulfamethoxazole crystal growth kinetics and mechanisms

期刊论文

Combustion characteristics and kinetics of bio-oil

Ruixia ZHANG, Zhaoping ZHONG, Yaji HUANG

期刊论文

Thermal degradation kinetics and lifetime estimation for polycarbonate/polymethylphenylsilsesquioxane

Jiangbo WANG, Zhong XIN

期刊论文

Modeling the aqueous reaction kinetics of estriol with ferrate

Cong LI, Naiyun GAO

期刊论文

Influence of extracellular polymeric substances from activated sludge on the aggregation kinetics of

期刊论文

Preparation and crystallization kinetics of micron-sized Mg(OH)

Xingfu SONG, Kefeng TONG, Shuying SUN, Ze SUN, Jianguo YU

期刊论文

Intrinsic kinetics and external diffusion of catalytic steam gasification of fine coal char particles

Xuantao Wu, Jie Wang

期刊论文

Determination of growth kinetics of microorganisms linked with 1,4-dioxane degradation in a consortium

期刊论文

Removal of Rhodamine B from aqueous solutions and wastewater by walnut shells: kinetics, equilibrium

Jasmin Shah, M. Rasul Jan, Attaul Haq, Younas Khan

期刊论文

Ozone kinetics of dimethyl sulfide in the presence of water vapor

Haitao WANG

期刊论文

Numerical investigation of the influence of kinetics and shape factor on barium sulfate precipitation

Zheng WANG, Zai-Sha MAO, Chao YANG, Qinghua ZHANG, Jingcai CHENG

期刊论文