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Effects of Na_(2)CO_(3)on reduction mechanism and kinetics of iron during deep reduction of ilmenite concentrate

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Journal of Iron and Steel Research International 2023年第3期30卷 419-428页

作者： Xiao-dong Lv You-ling Hou Yun-tao Xin Wei Lv Xue-wei Lv Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials Chongqing UniversityChongqing 400044China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China School of Metallurgy Northeastern UniversityShenyang 110819LiaoningChina

High-quality upgraded titanium slag obtained through semi-molten reduction with the addition of Na_(2)CO_(3)is important for the fluidizing chlorination process to produce TiO_(2)*** key is the effect of Na_(2)CO_(3)on the reduction behavior of ***,the effects of Na_(2)CO_(3)on reduction mechanism and kinetics of iron during deep reduction of ilmenite concentrate were *** results indicated that the metallization ratio of the reduced sample increased with increasing temperature,time,and dose of Na_(2)CO_(3).The addition of Na_(2)CO_(3)significantly accelerated the reduction of iron in the ilmenite concentrate and promoted the growth of iron ***,the addition of Na_(2)CO_(3)produced sodium iron titanates;thus,the metallization ratio of the sample decreased with an increase in the temperature and time when the temperature was above 1200℃and the time was more than 30 *** the doses of Na_(2)CO_(3)were 0,3,and 6 wt.%,the reduction of iron was controlled by the interfacial chemical reaction,both the interfacial chemical reaction and diffusion,and diffusion,respectively,and the apparent activation energies were 134.91,64.89,and 120.82 kJ/mol,respectively.

关键词： Ilmenite concentrate Sodium carbonate Metallization ratio reduction mechanism Kinetics

Coal-based reduction mechanism of low-grade laterite ore

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Transactions of Nonferrous Metals Society of China 2013年第11期23卷 3428-3433页

作者：李艳军孙永升韩跃新高鹏东北大学资源与土木工程学院沈阳110819

A low-grade nickel laterite ore was reduced at different reduction temperatures. The morphology of metallic particles was investigated by scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）. Experimental results indicate that the metallic nickel and iron gradually assemble and grow into larger spherical particles with increasing temperature and prolonging time. After reduction, the nickel laterite ore obviously changes into two parts of Fe-Ni metallic particles and slag matrix. An obvious relationship is found between the reduction of iron magnesium olivine and its crystal chemical properties. The nickel and iron oxides are reduced to metallic by reductant, and the lattice of olivine is destroyed. The entire reduction process is comprised of oxide reduction and metallic phase growth.

关键词： nickel laterite ore coal-based reduction reduction mechanism Fe-Ni metallic phase

Electrochemical reduction characteristics and mechanism of nitrobenzene compounds in the catalyzed Fe-Cu process

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Journal of Environmental Sciences 2006年第2期18卷 379-387页

作者： XU Wen-ying FAN Jin-hong GAO Ting-yao The National Engineering Research Center for Urban Pollution Control Tongji University Shanghai 200092 China

The reduction of the nitrobenzene compounds （NBCs） by the catalyzed Fe-Cu process and the relationship between the electrochemical reduction characteristics of NBCs at copper electrode and reduction rate were studied in alkaline medium（pH=11）. The catalyzed Fe-Cu process was found more effective on degradation of NBCs compared to Master Builder＇s iron. The reduction rate by the catalyzed Fe-Cu process decreased in the following order： nitrobenzene 〉4-chloro-nitrobenzene ≥m-dinitrobenzene ：〉 4-nitrophenol ≥2,4-dinitrotoluene 〉2-nitrophenol. The reduction rate by Master Builder＇s iron decreased in the following order： m-dinitrobenzene ≥4-chloro-nitrobenzene 〉4-nitrophenol 〉2,4-dinitrotoluene ≈nitrobenzene 〉2-nitrophenol. NBCs were reduced directly on the surface of copper rather than by the hydrogen produced at cathode in the catalyzed Fe-Cu process. The reduction was realized by the hydrogen produced at cathode and Fe（OH）2 in Master Builder＇s iron, It is an essential difference in reaction mechanisms between these two technologies. For this reason, the reduction by the catalyzed Fe-Cu depended greatly on NBC＇s electron withdrawing ability.

关键词： wastewater contaminated by NBCs electrochemical reduction characteristics catalyzed Fe-Cu process reduction mechanism

Photocatalytic reduction of Cr(Ⅵ) over cinder-based nanoneedle in presence of tartaric acid: Synergistic performance and mechanism

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Journal of Environmental Sciences 2021年第9期33卷 194-204页

作者： Wenwu Yang Zhenfei Yang Luhua Shao Sijian Li Yutang Liu Xinnian Xia College of Chemistry and Chemical Engineering Hunan UniversityChangsha 410082China Advanced Catalytic Engineering Research Center of the Ministry of Education Hunan UniversityChangsha 410082China College of Environmental Science and Engineering Hunan UniversityLushan South RoadYuelu DistrictChangsha 410082China

Cr(Ⅵ) is a common heavy metal ion, which will seriously harm human body and ***, the removal of Cr(Ⅵ) has become an attractive *** this work, cinder was used as a raw material to synthesize a nanoneedle material: γ-(AlOOH@FeOOH)(γ-Al@Fe).The physicochemical properties of γ-Al@Fe were thoroughly characterized, and its effectiveness as a catalyst for photocatalytic reduction of Cr(Ⅵ) was *** results showed that Cr(Ⅵ) could be efficiently reduced by γ-Al@Fe in the presence of tartaric acid(TA) under visible *** variable factors on the reaction were investigated in detail, and the results showed that under optimal conditions(γ-Al@Fe 0.4 g/L, TA 0.6 g/L, pH 2), Cr(Ⅵ)was completely reduced within 7 ***, scavenger experiments and EPR proved that O_(2)^(·-) and CO_(2)^(·-) played a significant role in the photocatalytic reduction of Cr(Ⅵ).TA acts as a sacrificial agent to trap the holes and generate strong reducing free radicals: CO_(2)^(·-).Dissolving O_(2) could react with electrons to generate O_(2)^(·-).This work discussed the performance and mechanism of photocatalytic reduction of Cr(Ⅵ) in detail, which provided a new idea for the resource utilization of solid waste and the treatment of heavy metal sewage.

关键词： Cinder Tartaric acid Visible light photocatalysis Cr(Ⅵ)removal reduction mechanism

Efficient reduction and adsorption of Cr(Ⅵ)using FeCl_(3)-modified biochar:Synergistic roles of persistent free radicals and Fe(Ⅱ)

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Journal of Environmental Sciences 2024年第3期137卷 626-638页

作者： Shujie Hu Chengshuai Liu Hongling Bu Manjia Chen Ying-heng Fei 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 State Key Laboratory of Environmental Geochemistry Institute of GeochemistryChinese Academy of ScienceGuiyang 550081China School of Environment Science and Engineering Guangzhou UniversityGuangzhou 510006China College of Resources and Environment Chongqing SchoolUniversity of Chinese Academy of SciencesChongqing 400714China School of Environmental Science and Engineering Guangdong University of TechnologyGuangzhou 510006China

Transition metal iron and persistent free radicals(PFRs)both affect the redox properties of biochar,but the electron transfer relationship between them and the coupling reduction mechanism of Cr(Ⅵ)requires further *** untangle the interplay between iron and PFRs in biochar and the infuences on redox properties,FeCl_(3)-modified rice husk biochar(FBCs)was prepared and its reduction mechanism for Cr(Ⅵ)without light was *** FBCs had higher surface positive charges,oxygen-containing functional groups,and PFRs compared with pristine rice husk biochar(BC).Phenoxyl PFRs with high electrondonating capability formed in *** pronounced electron paramagnetic resonance signals showed that the PFRs preferred to form at lower Fe(Ⅲ)*** a high concentration of Fe(Ⅲ)would be reduced to Fe(Ⅱ)and consumed the formed *** kinetics and X-ray photoelectron spectroscopy analysis indicated that the FBCs effectively enhanced the Cr(Ⅵ)removal efficiency by 1.54-8.20 fold and the Cr(Ⅵ)reduction efficiency by 1.88-9.29 fold compared to those of *** quenching and competitive reductant addition experiments revealed that the higher Cr(Ⅵ)reduction performance of FBCs was mainly attributed to the formed PFRs,which could contribute to~74.0%of Cr(Ⅵ)reduction by direct or indirect electron *** PFRs on FBCs surfaces could promote the Fe(Ⅲ)/Fe(Ⅱ)cycle through single electron transfer and synergistically accelerate~52.3%of Cr(Ⅵ)*** study provides an improved understanding of the reduction mechanism of iron-modified biochar PFRs on Cr(Ⅵ)in environments.

关键词： Biochar Iron-modification Cr(Ⅵ) Electron transfer reduction mechanism

reduction behavior of iron ore powder by high-volatile coal in thermogravimetric-gas chromatographic and kinetic analysis

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Journal of Iron and Steel Research International 2024年第1期31卷 92-107页

作者： Rui-meng Shi Qi-yuan Mi Bin Li Xiao Shi Chong Zou Jing Guo Han-jie Guo School of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an710055ShaanxiChina China International Engineering Consulting Corporation Beijing100048China School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing100083China

The reduction behavior of iron ore powder by high-volatile coal was investigated,and its kinetic mechanism was *** effect of volatiles in coal on the reduction reaction of iron ore was compared by utilizing a Xinjiang lignite with a high volatile content and its pyrolysis carbon produced by high-temperature pyrolysis to remove volatiles,serving as a *** mass loss and gas composition of the samples during the reduction process were detected using thermo-gravimetric analysis and gas chromatography,and the morphological changes of iron ore powder were observed through scanning electron *** kinetic parameters of the iron oxide reduction reaction were calculated by the Flynn-Ozawa-Wall method,and the kinetic mechanism of volatile participation in the iron oxide reduction reaction was determined through the Coats-Redfern *** results indicate that the coupling effect between the high-volatile coal pyrolysis and reduction reactions occurs during the second stage of the entire coupling process,which corresponds to the late stage of coal pyrolysis with a substantial release of H_(2)and *** volatiles in coal actively participated in the reduction reaction,reducing the initiation temperature of the reaction by around 200℃.The reduction of iron oxides by high-volatile coal was jointly promoted by the"hydrogen cycle"and"carbon cycle",resulting in a higher reduction extent and metallization rate at the end of the *** high-volatile coal was used as the reductant,the average activation energy for the entire process was 76.5 kJ/mol,a significant decrease compared to the employment of pyrolysis carbon without volatiles as the reductant(1167 kJ/mol).

关键词： Direct reduction High-volatile coal Volatile Kinetics reduction mechanism

Phosphorus reduction behavior of high-phosphate iron ore during hydrogen-rich sintering

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International Journal of Minerals,Metallurgy and Materials 2022年第10期29卷 1862-1872页

作者： Yanbiao Chen Wenguo Liu Haibin Zuo State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China

High-phosphorus iron ore resource is considered a refractory iron ore because of its high-phosphorus content and complex ore phase structure. Therefore, the development of innovative technology to realize the efficient utilization of high-phosphorus iron ore resources is of theoretical and practical significance. Thus, a method for phosphorus removal by gasification in the hydrogen-rich sintering process was proposed. In this study, the reduction mechanism of phosphorus in hydrogen-rich sintering, as well as the reduction kinetics of apatite based on the non-isothermal kinetic method, was investigated. Results showed that, by increasing the reduction time from 20 to 60 min, the dephosphorization rate increased from 10.93%to 29.51%. With apatite reduction, the metal iron accumulates, and part of the reduced phosphorus gas is absorbed by the metal iron to form stable iron-phosphorus compounds, resulting in a significant reduction of the dephosphorization rate. Apatite reduction is mainly concentrated in the sintering and burning zones, and the reduced phosphorus gas moves downward along with flue gas under suction pressure and is condensed and adsorbed partly by the sintering bed when passing through the drying zone and over the wet zone. As a result, the dephosphorization rate is considerably reduced. Based on the Ozawa formula of the iso-conversion rate, the activation energy of apatite reduction is 80.42 kJ/mol. The mechanism function of apatite reduction is determined by a differential method (i.e., the Freeman-Carroll method) and an integral method (i.e., the Coats-Redfern method). The differential form of the equation is f(α)=2(1-α)^(1/2), and the integral form of the equation is G(α)=1-(1-α)^(1/2).

关键词： hydrogen-rich sintering dephosphorization reduction mechanism kinetics thermogravimetry

A high-efficiency separation process of Fe and Zn from zinc-bearing dust by direct reduction

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Journal of Iron and Steel Research International 2022年第10期29卷 1559-1572页

作者： Ding-zheng Wang De-qing Zhu Jian Pan Zheng-qi Guo Hong-yu Tian Yu-xiao Xue School of Minerals Processing and Bioengineering Central South UniversityChangsha410083HunanChina

It is urgent to dispose of zinc-bearing dust from steel plants,and direct reduction process is an effective method to remove hazardous metals and recycle iron from the *** reduction behavior of carbon-containing pellets which were made from three kinds of zinc-bearing dust was *** the pellets were reduced at 1200℃ for 50 min,the reduced pellets with cold compressive strength of 1164 N pellet−1 and Zn contentreduction rate was controlled by the chemical *** strengthening mechanism of reduced pellets and iron oxide reduction mechanism was investigated by thermodynamic calculation besides X-ray diffraction,scanning electron microscopy combined with energy dispersive spectrometry,and optical microscopy *** was found that higher temperatures are required for the reduction of spinel phase(zinc ferrite)and olivine phase(hedenbergite).The generation and growth of metallic iron bridges could significantly increase the compressive strength of reduced *** iron oxide reduction in the carbon-containing pellets followed the uniform internal reduction model and possessed a high apparent reaction rate,which can improve energy utilization rate and production efficiency.

关键词： Zinc-bearing dust reduction mechanism Kinetics High efficiency Direct reduction

Theoretical perspectives on the reduction of Pu(Ⅳ)and Np(Ⅵ)by methylhydrazine in HNO_(3)solution:Implications for Np/Pu separation

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Chinese Chemical Letters 2024年第7期35卷 306-312页

作者： Xiaobo Li Qunyan Wu Congzhi Wang Jianhui Lan Meng Zhang Weiqun Shi Fundamental Science on Nuclear Safety and Simulation Technology Laboratory College of Nuclear Science and TechnologyHarbin Engineering UniversityHarbin 150001China Laboratory of Nuclear Energy Chemistry Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China

Effective adjustment and control of the oxidation state of plutonium(Pu)and neptunium(Np)is an indispensable component of Np/Pu separation in spent nuclear fuel *** hydrazine derivatives including methylhydrazine(CH_(3)N_(2)H_(3))effectively achieves the reduction of Np(Ⅵ)to Np(V)without reducing Pu(Ⅳ).Herein,we explored the reduction mechanisms of Pu(Ⅳ)and Np(Ⅵ)by CH_(3)N_(2)H_(3)in HNO_(3)solution using scalar-relativistic density functional *** elucidated the difference in the reduction mechanism between Np(Ⅵ)and Pu(Ⅳ)ions by CH_(3)N_(2)H_(3).The energy barrier for the reduction of[NpⅥO_(2)(H_(2)O)_(5)]^(2+)and[NpⅥO_(2)(NO_(3))(H_(2)O)_(3)]^(+)by CH_(3)N_(2)H_(3)is largely different due to the coordination of nitrate ***,the energy barrier of the reduction of[NpⅥO_(2)(H_(2)O)_(5)]^(2+)is apparently lower than that of[PuⅣ(NO_(3))_(2)(H_(2)O)_(7)]^(2+),which is in line with the experimental *** results of Mayer bond order and localized molecular orbitals clarify the structural evolution of the reaction *** of the spin density demonstrates that the first Np(Ⅵ)and Pu(Ⅳ)reduction belongs to the outer-sphere electron transfer and the second Np(Ⅵ)and Pu(Ⅳ)reduction is the hydrogen *** study explains theoretically why CH_(3)N_(2)H_(3)reduces Np(Ⅵ)but not Pu(Ⅳ),and helps to design promising reductants for the Np/Pu separation in spent nuclear fuel reprocessing.

关键词： Neptunium Plutonium Methylhydrazine reduction mechanism Np/Pu separation