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kinetics of antimony biogeochemical processes under pre-definite anaerobic and aerobic conditions in a paddy soil

Journal of Environmental Sciences 2022年第3期34卷 269-280页

作者： Bingqing Xia Yang Yang Fangbai Li Tongxu Liu Guangzhou Institute of Geochemistry Chinese Academy of SciencesGuangzhou 510640China National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and ManagementInstitute of Eco-environmental and Soil SciencesGuangdong Academy of SciencesGuangzhou 510650China University of Chinese Academy of Sciences Beijing 200049China

While the transformation of antimony(Sb) in paddy soil has been previously investigated, the biogeochemical processes of highly chemical active Sb in the soil remain poorly understood. In addition, there is a lack of quantitative understanding of Sb transformation in soil. Therefore, in this study, the kinetics of exogenous Sb in paddy soils were investigated under anaerobic and aerobic incubation conditions. The dissolved Sb(V) and the Sb(V) extracted by diffusive gradient technique decreased under anaerobic conditions and then increased under aerobic conditions. The redox reaction of Sb occurred, and Sb bioavailability significantly decreased after 55 days of incubation. The kinetics of Fe and the scanning transmission electron microscopy analysis revealed that the Fe oxides were reduced and became dispersed under anaerobic conditions, whereas they were oxidized and re-aggregated during the aerobic stage. In addition, the redox processes of sulfur and nitrogen were detected under both anaerobic and aerobic conditions. Based on these observations, a simplified kinetic model was established to distinguish the relative contributions of the transformation processes. The bioavailability of Sb was controlled by immobilization as a result of S reduction and by mobilization as a result of Fe reductive dissolution and S oxidation, rather than the p H. These processes coupled with the redox reaction of Sb jointly resulted in the complex behavior of Sb transformation under anaerobic and aerobic conditions. The model-based method and findings of this study provide a comprehensive understanding of the Sb transformation in a complex soil biogeochemical system under changing redox conditions.

关键词： Antimony Biogeochemical process kinetics Paddy soil Anaerobic conditions Aerobic conditions

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kinetics and mechanism of propylene hydro-oxidation to acrolein on Au catalysts

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Nano Research 2024年第1期17卷 354-363页

作者： Wei Du Zhihua Zhang Nan Song Xuezhi Duan Xinggui Zhou State Key Laboratory of Chemical Engineering School of Chemical EngineeringEast China University of Science and TechnologyShanghai 200237China

Propylene epoxidation by H_(2)and O_(2)to propylene oxide(PO)over the Au-Ti bifunctional catalysts,as an ideal reaction for PO production,has attracted great interest.Revealing the mechanism of acrolein formation is of great importance for understanding the mechanism of molecular oxygen activation and the formation of hydroperoxo species on the Au sites.Here,we investigate the reaction mechanism of propylene oxidation to acrolein on the Au/uncalcined TS-1(Au/TS-1-B)catalyst through a combination of multiple characterization,H_(2)/D_(2)exchange,kinetics experiment,and modeling.The Ti sites are found to be non-essential to acrolein formation.Moreover,the acrolein formation on the Au/TS-1-B catalyst is confirmed to be promoted by H_(2)through hydroperoxo species formation,which includes two main steps:propylene dehydrogenation to*C_(3)H_(5)with the aid of*OOH species,and*C_(3)H_(5)oxidation by*OOH to acrolein.The latter step is determined to be the rate-determining step because the corresponding kinetics model gives the best description for experimental results.This work not only provides kinetics insights for the propylene hydro-oxidation to acrolein on the Au-Ti bifunctional catalysts,but also facilitates the rational design of Au catalysts with high activity and selectivity in the direct propylene epoxidation with H_(2)and O_(2).

关键词： kinetics mechanism gold acrolein hydro-oxidation

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kinetics of solid-state reduction of chromite overburden

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International Journal of Minerals,Metallurgy and Materials 2023年第12期30卷 2347-2355页

作者： Saida Shaik Zhiyuan Chen Preeti Prakash Sahoo Chenna Rao Borra Metallurgical and Materials Engineering Department Indian Institute of Technology KharagpurKharagpurWest Bengal 721302India VITO-Flemish Institute for Technological Research Boeretang 200B-2400 MolBelgium Research and Development Division Tata Steel Ltd.Jamshedpur 831001India

The demand for alternative low-grade iron ores is on the rise due to the rapid depletion of high-grade natural iron ore resources and the increased need for steel usage in daily life.However,the use of low-grade iron ores is a constant clinical task for industry metallurgists.Direct smelting of low-grade ores consumes a substantial amount of energy due to the large volume of slag generated.This condition can be avoided by direct reduction followed by magnetic separation(to separate the high amount of gangue or refractory and metal parts)and smelting.Chromite overburden(COB)is a mine waste generated in chromite ore processing,and it mainly consists of iron,chromium,and nickel(kinetics of the solid-state reduction of self-reduced pellets prepared using low-grade iron ore(COB)were thoroughly investigated via thermal analysis.The results showed that the reduction of pellets followed a firstorder autocatalytic reaction control mechanism in the temperature range of 900-1100℃.The autocatalytic nature of the reduction reaction was due to the presence of nickel in the COB.The apparent activation energy obtained from the kinetics results showed that the solid-state reactions between COB and carbon were the rate-determining step in iron oxide reduction.

关键词： chromite overburden solid-state reduction kinetics autocatalytic reaction

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kinetics measurement of ethylene-carbonate synthesis via a fast transesterification by microreactors

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Chinese Journal of Chemical Engineering 2023年第1期53卷 243-250页

作者： Tengjie Wang Wenkai Li Xuehui Ge Ting Qiu Xiaoda Wang Engineering Research Center of Reactive Distillation Fujian Province Higher Education InstitutesCollege of Chemical EngineeringFuzhou UniversityFuzhou 350108China Qingyuan Innovation LaboratoryQuanzhou 362801China

High-purity ethylene carbonate(EC)is widely used as battery electrolyte,polycarbonate monomer,organic intermediate,and so on.An economical and sustainable route to synthesize high-purity ethylene carbonate(EC)via the transesterification of dimethyl carbonate(DMC)with ethylene glycol(EG)is provided in this work.However,this reaction is so fast that the reaction kinetics,which is essential for the industrial design,is hard to get by the traditional measuring method.In this work,an easy-to-assemble microreactor was used to precisely determine the reaction kinetics for the fast transesterification of DMC with EG using sodium methoxide as catalyst.The effects of flow rate,microreactor diameter,catalyst concentration,reaction temperature,and reactant molar ratio were investigated.An activity-based pseudohomogeneous kinetic model,which considered the non-ideal properties of reaction system,was established to describe the transesterification of DMC with EG.Detailed kinetics data were collected in the first 5 min.Using these data,the parameters of the kinetic model were correlated with the maximum average error of 11.19%.Using this kinetic model,the kinetic data at different catalyst concentrations and reactant molar ratios were predicted with the maximum average error of 13.68%,suggesting its satisfactory prediction performance.

关键词： Microreactor kinetics Ethylene carbonate synthesis Transesterification Sodium methoxide

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kinetics of Catalyzed Thermal Degradation of Polylactide and Its Application as Sacrificial Templates

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Chinese Journal of Chemistry 2022年第23期40卷 2801-2807,I0002页

作者： Li Feng Chenhui Cui Zhen Li Mengyuan Zhang Shenghui Gao Qiang Zhang Youshen Wu Zhishen Ge Yilong Cheng Yanfeng Zhang School of Chemistry Xi'an Jiaotong UniversityXianShaanxi 710049China Shaanxi Yuneng Group Energy and Chemical Industry Research Institute Co. Ltd.YulinShaanxi 719000China

Polylactide(PLA)is an outstanding sacrificial template material for the manufacture of microchannels in a thermosetting matrix.However,the initial thermal degradation temperature of pure PLA is relatively high(about 280℃),which limits its use as a sacrificial template.In this report,we found that TBD,an organic base catalyst,can significantly reduce the thermal degradation temperature of PLA.TBD has higher catalytic activity for the thermal degradation of PLA compared with Tin(II)oxalate(Sn(Oxa)),one catalyst reported in the literature.Moreover,the gaseous products catalyzed by TBD for PLA thermal degradation are mainly lactide,and the formation temperature of the monomer is lower and the yield is higher,which may have potential value for PLA recycling.A combined catalyst,S8T2,was composed of 80%low activity catalyst Sn(Oxa)and 20%high activity catalyst TBD,which can catalyze the rapid degradation of PLA without greatly damaging the mechanical properties of PLA.PLA-S8T2 sacrificial fibers can form high-precision one-dimensional microchannels in the epoxy resin matrix,and 3D-printed PLA-S8T2 sacrificial templates can be used to form three-dimensional microchannels in a thermosetting matrix by vaporization of sacrificial components process(VaSC).These features highlight the great potential of PLA-S8T2 as sacrificial template material for the preparation of the complicated microchannels in the thermosetting matrix.

关键词： Polymers Gaseous product kinetics Sacrificial template Microchannel

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kinetics of Selective Hydrogenation of PAHs from FCC Slurry Extract over Ni-W/γ-Al_(2)O_(3) Catalyst

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China Petroleum Processing & Petrochemical Technology 2023年第4期25卷 31-40页

作者： Cui Wenlong Wu Fubu Chen Yulong Qian Junfeng Luo Hui Liu Yingjie Yang Jihe Jiangsu Province Key Laboratory of Fine Petrochemical Engineering Advanced Catalysis and Green Manufacturing Collaborative Innovation CenterCNPC-CZU Innovation AllianceSchool of Petrochemical EngineeringChangzhou UniversityChangzhou 213164China State Key Laboratory of Heavy Oil Processing China University of PetroleumQingdao 266580China

The selective hydrogenation of polycyclic aromatic hydrocarbons(PAHs)from fluid catalytic cracking(FCC)slurry extract was conducted in a batch reactor over aγ-Al_(2)O_(3)-supported bimetallic Ni-W catalyst.For the Ni-W/γ-Al_(2)O_(3) catalyst,the experiment run was divided into three processes according to the reaction conditions used:(1)the absence of hydrogenation as both temperature and pressure increased;(2)the desulfurization of FCC slurry extract under a fixed pressure as the temperature increased;and(3)the selective hydrogenation of PAHs when both pressure and temperature remained constant.The hydrogen consumption could be accurately calculated from the Redlich–Kwong equation of state.The results for the removal of PAHs with hydrogenation displayed an excellent fit to the first-order kinetics.The apparent activation energy was determined to be 20.80 kJ/mol.

关键词： selective hydrogenation kinetics PAHs FCC slurry extract

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Photodegradation of hydroxyfluorenes in ice and water: A comparison of kinetics, effects of water constituents, and phototransformation by-products

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Journal of Environmental Sciences 2023年第2期124卷 139-145页

作者： Linke Ge Shengkai Cao Crispin Halsall Junfeng Niu Dongxiao Bai Guangkai He Peng Zhang Hongrui Ma School of Environmental Science and Engineering Shaanxi University of Science&TechnologyXi’an 710021China Lancaster Environment Centre Lancaster UniversityLancaster LA14YQUK State Environmental Protection Key Laboratory of Coastal Ecosystem National Marine Environmental Monitoring CenterDalian 116023China

The photochemical behavior of organic pollutants in ice is poorly studied in comparison to aqueous photochemistry.Here we report a detailed comparison of ice and aqueous photodegradation of two representative OH-PAHs,2-hydroxyfluorene(2-OHFL)and 9-hydroxyfluorene(9-OHFL),which are newly recognized contaminants in the wider environment including colder regions.Interestingly,their photodegradation kinetics were clearly influenced by whether they reside in ice or water.Under the same simulated solar irradiation(λ>290 nm),OHFLs photodegraded faster in ice than in equivalent aqueous solutions and this was attributed to the specific concentration effect caused by freezing.Furthermore,the presence of dissolved constituents in ice also influenced photodegradation with 2-OHFL phototransforming the fastest in‘seawater’ice(k=(11.4±1.0)×10^(−2) min^(−1))followed by‘pure-water’ice((8.7±0.4)×10^(−2) min^(−1))and‘freshwater’ice((8.0±0.7)×10^(−2) min^(−1)).The presence of dissolved constituents(specifically Cl^(−),NO_(3)^(−),Fe(Ⅲ)and humic acid)influences the phototransformation kinetics,either enhancing or suppressing phototransformation,but this is based on the quantity of the constituent present in the matrixes,the specific OHFL isomer and the matrix type(e.g.,ice or aqueous solution).Careful derivation of key photointermediates was undertaken in both ice and water samples using tandem mass spectrometry.Ice phototransformation exhibited fewer by-products and‘simpler’pathways giving rise to a range of hydroxylated fluorenes and hydroxylated fluorenones in ice.These results are of importance when considering the fate of PAHs and OH-PAHs in cold regions and their persistence in sunlit ice.

关键词： Ice photochemistry Hydroxyfluorene Photodegradation kinetics Water constituents Intermediates

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Geochemical modeling to aid experimental design for multiple isotope tracer studies of coupled dissolution and precipitation reaction kinetics

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Acta Geochimica 2024年第1期43卷 1-15页

作者： Mingkun Chen Peng Lu Yongchen Song Chen Zhu Department of Earth and Atmospheric Sciences Indiana UniversityBloomingtonIN 47405USA School of Energy and Power Engineering Dalian University of TechnologyDalian 116024China EXPEC Advanced Research Center Saudi Aramco31311 DhahranSaudi Arabia

It is a challenge to make thorough but efficient experimental designs for the coupled mineral dissolution and precipitation studies in a multi-mineral system, because it is difficult to speculate the best experimental duration, optimal sampling schedule, effects of different experimental conditions, and how to maximize the experimental outputs prior to the actual experiments. Geochemical modeling is an efficient and effective tool to assist the experimental design by virtually running all scenarios of interest for the studied system and predicting the experimental outcomes. Here we demonstrated an example of geochemical modeling assisted experimental design of coupled labradorite dissolution and calcite and clayey mineral precipitation using multiple isotope tracers. In this study, labradorite(plagioclase) was chosen as the reactant because it is both a major component and one of the most reactive minerals in basalt. Following our isotope doping studies of single minerals in the last ten years, initial solutions in the simulations were doped withmultiple isotopes(e.g., Ca and Si). Geochemical modeling results show that the use of isotope tracers gives us orders of magnitude more sensitivity than the conventional method based on concentrations and allows us to decouple dissolution and precipitation reactions at near-equilibrium condition. The simulations suggest that the precise unidirectional dissolution rates can inform us which rate laws plagioclase dissolution has followed. Calcite precipitation occurred at near-equilibrium and the multiple isotope tracer experiments would provide near-equilibrium precipitation rates, which was a challenge for the conventional concentration-based experiments. In addition, whether the precipitation of clayey phases is the rate-limiting step in some multi-mineral systems will be revealed. Overall, the modeling results of multimineral reaction kinetics will improve the understanding of the coupled dissolution–precipitation in the multi-mineral systems and the quality of geochemic

关键词： kinetics Feldspar Isotope doping Near-equilibrium CO_(2)sequestration Basalt

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Improving hydrogen storage thermodynamics and kinetics of Ce-Mg-Ni-based alloy by mechanical milling with TiF_(3)

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Journal of Magnesium and Alloys 2024年第4期12卷 1593-1607页

作者： Hongwei Shang Wei Zhang Xin Wei Yaqin Li Zeming Yuan Jun Li Yanghuan Zhang School of Mechanical and Electrical Engineering Chuzhou UniversityChuzhou 239000China Department of Functional Material Research Central Iron and Steel Research InstituteNo.76 Xueyuannan RoadHaidian DistrictBeijing 100081China Key Laboratory of Integrated Exploitation of Bayan-Obo Multi-Metal Resources Inner Mongolia University of Science and TechnologyBaotou 014010China China Rare Earth New Material(Weishan)Co. Ltd.Jining 277600China

Mg-based hydrides are too stable and the kinetics of hydrogen absorption and desorption is not satisfactory.An efficient way to improve these shortcomings is to employ reactive ball milling to synthesize the nanocomposite materials of Mg and additives.In this experiment,TiF_(3)was selected as an additive,and the mechanical milling method was employed to prepare the experimental alloys.The alloys used in this experiment were the as-cast Ce_(5)Mg_(85)Ni_(10),as-milled Ce_(5)Mg_(85)Ni_(10)and Ce_(5)Mg_(85)Ni_(10)+3 wt.%TiF3.The phase transformation,structural evolution,isothermal and non-isothermal hydrogenation and dehydrogenation performances of the alloys were inspected by XRD,SEM,TEM,Sievert apparatus,DSC and TGA.It revealed that nanocrystalline appeared in the as-milled samples.Compared with the as-cast alloy,ball milling made the particle dimension and grain size decrease dramatically and the defect density increase significantly.The addition of TiF_(3)made the surface of ball milling alloy particles markedly coarser and more irregular.Ball milling and adding TiF_(3)distinctly improved the activation and kinetics of the alloys.Moreover,ball milling along with TiF_(3)can decrease the onset dehydrogenation temperature of Mg-based hydrides and slightly ameliorate their thermodynamics.

关键词： Mg-based hydrides TiF_(3) Ball milling Thermodynamics kinetics

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Microscale spherical TiO_(2)powder prepared by hydrolysis of TiCl_(4)solution:Synthesis and kinetics

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Particuology 2024年第1期84卷 60-71页

作者： Peiyi Yan Ying Zhang Shili Zheng School of Rare Earths University of Science and Technology of ChinaHefei230026China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou341119China Key Laboratory of Green Process and Engineering National Engineering Research Center of Green Recycling for Strategic Metal ResourcesInstitute of Process EngineeringChinese Academy of SciencesBeijing100190China State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization Panzhihua617000China

Hydrolysis of TiCl_(4)solution is capable of preparing microscale TiO_(2)particles.This research studied the synthesis of microscale spherical TiO_(2)powders and the hydrolysis kinetics.The effects of the flow field generated by different agitators and baffles in the crystallizer,the initial free acid concentration,the initial equivalent TiO_(2)concentration,and the temperature on the hydrolysis progress and powder morphology were systematically studied.The results show that the flow field in a crystallizer can significantly affect the morphology and particle size of the powders,and the axial flow can improve the sphericity of the powders.The increased free HCl and equivalent TiO_(2)concentrations in the pregnant solution inhibit the forward hydrolysis reaction,prolong the time to reach equilibrium,and reduce the yield.An appropriate temperature matching the compositions of the pregnant solution is crucial for the powder morphology and size.Powders with sizes ranging from around 5 um-40μm can be tuned under controlled flow field,solution compositions,and temperature conditions.In addition,the Cheng and Wunderlich modified Avrami equation was used for the crystallization kinetic modeling.The effects of the free HCl concentration,equivalent TiO_(2)concentration,and hydrolysis temperature are reflected in the reaction rate constant and active nuclei reduction index.Increasing the free HCl and equivalent TiO_(2)concentrations will reduce the reaction rate constant and accelerate the deactivation of the active nuclei,thus increasing the final powder size,while increasing the temperature will lead to the opposite results.

关键词： TiCl_(4) Hydrolysis Microscale TiO_(2) Spherical kinetics

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