The Experts below are selected from a list of 1641 Experts worldwide ranked by ideXlab platform
Yali Feng - One of the best experts on this subject based on the ideXlab platform.
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new understanding of the reduction mechanism of Pyrolusite in the acidithiobacillus ferrooxidans bio leaching system
Electrochimica Acta, 2019Co-Authors: Jinxing Kang, Yali Feng, Xiangyi Deng, Hongjun WangAbstract:Abstract The reductive dissolution of Pyrolusite in simulated Acidithiobacillus ferrooxidans bio-leaching medium was investigated. This study was performed in three stages. First, the advantageous electrochemical test conditions, parallel to the optimal bio-leaching conditions and adopting the Mn reduction rate, were determined by imitated electrolysis. The facilitation of A. ferrooxidans on MnO2 reduction is sensitive to pH and Fe(III) concentration. Second, electrochemical tests revealed that the reductive dissolution of manganese dioxide incorporated two single electron and proton steps-the first exchange of MnO2 to MnO·OH, and then conversion to Mn(OH)2 for diffusion. The results of transient and steady electrochemical measurements indicated that the first electron-transfer significantly affects the rate controlling step of Mn-leaching in control(9K) medium, while using A. ferrooxidans and Fe(III) in the solution tends to enable the leaching rate to be controlled by the latter electron transfer step. Third, the analysis of semiconductor and carrier properties of passive films of Pyrolusite formed in the different solutions, illustrated that the reductive dissolution of manganese dioxide tends to depend on the movement of the holes. The first electron preferentially reacts with the shallow energy level of the O-vacancy to form MnO2·-, which then absorbs H+ to become MnO·OH. The second electron participates in the transformation of MnO·OH to (MnOH)(OH) and then to Mn(OH)2. A. ferrooxidans increases the carrier densities of the passivating film accelerating electron and proton transfer and Fe(III) primarily influences the shallow donor density of oxygen during the first electron-exchange. Additionally, the synergistic effect of A. ferrooxidans and Fe(III) on manganese dioxide ore reductive leaching is confirmed.
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New understanding of the reduction mechanism of Pyrolusite in the Acidithiobacillus ferrooxidans bio-leaching system
'Elsevier BV', 2019Co-Authors: Kang Jin-xing, Yali Feng, Li Hao-ran, Du Zhu-wei, Deng Xiang-yi, Wang Hong-junAbstract:The reductive dissolution of Pyrolusite in simulated Acidithiobacillus ferrooxidans bio-leaching medium was investigated. This study was performed in three stages. First, the advantageous electrochemical test conditions, parallel to the optimal bio-leaching conditions and adopting the Mn reduction rate, were determined by imitated electrolysis. The facilitation of A. ferrooxidans on MnO2 reduction is sensitive to pH and Fe(III) concentration. Second, electrochemical tests revealed that the reductive dissolution of manganese dioxide incorporated two single electron and proton steps-the first exchange of MnO2 to MnO center dot OH, and then conversion to Mn(OH)(2) for diffusion. The results of transient and steady electrochemical measurements indicated that the first electron-transfer significantly affects the rate controlling step of Mn-leaching in control(9K) medium, while using A. ferrooxidans and Fe(III) in the solution tends to enable the leaching rate to be controlled by the latter electron transfer step. Third, the analysis of semiconductor and carrier properties of passive films of Pyrolusite formed in the different solutions, illustrated that the reductive dissolution of manganese dioxide tends to depend on the movement of the holes. The first electron preferentially reacts with the shallow energy level of the O-vacancy to form MnO2-, which then absorbs H+ to become MnO center dot OH. The second electron participates in the transformation of MnO center dot OH to (MnOH)(OH) and then to Mn(OH)(2). A. ferrooxidans increases the carrier densities of the passivating film accelerating electron and proton transfer and Fe(III) primarily influences the shallow donor density of oxygen during the first electron-exchange. Additionally, the synergistic effect of A. ferrooxidans and Fe(III) on manganese dioxide ore reductive leaching is confirmed. (C) 2018 Elsevier Ltd. All rights reserved
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effects of acidithiobacillus ferrooxidans and fe iii on pyrite Pyrolusite bioleaching process
Metallurgical Research & Technology, 2017Co-Authors: Yali Feng, Jinxing Kang, Xu Zhang, Xiangyi Deng, Min Sun, Xipei ChenAbstract:The beneficial effects of Acidithiobacillus ferrooxidans and/or Fe(III) on manganese bioleaching from a low-grade manganese ore were confirmed. The results showed that the rate of manganese bioleaching increases with the amount of A. ferrooxidans and/or Fe(III). With the presence of Fe(III) and A. ferrooxidans the average initial leaching rate increased from 0.06 to 0.15 g/(L h). Cyclic voltammetry analysis showed that the presence of A. ferrooxidans and/or Fe(III) generate obvious redox potential polarization in the solution. Fe(III) reduced the potential difference between anode and cathode of pyrite and promoted the positive cathodic polarization of Pyrolusite at 0.2 V. In the process of pyrite oxidation A. ferrooxidans accelerated the generation and transfer of electron.
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enhancement of bio oxidation of refractory arsenopyritic gold ore by adding Pyrolusite in bioleaching system
Transactions of Nonferrous Metals Society of China, 2016Co-Authors: Xu Zhang, Yali Feng, Li HaoranAbstract:Pyrolusite was added in the bioleaching process to enhance the bio-oxidation process. Bioleaching tests at different dosages of Pyrolusite ore, pH and inoculation amounts of Acidithiobacillus ferrooxidans were studied. The results showed that the time of the bio-oxidation process was decreased obviously and the arsenic leaching rate reached 94.4% after the bioleaching. The bio-oxidation of arsenopyrite and the effective extraction of manganese from Pyrolusite were achieved by the bioleaching process. After bioleaching, the leaching rate of gold from the reaction residues reached 95.8% by cyanide leaching. In the bio-oxidation process, Pyrolusite increased the redox potential of the solution to accelerate the bioleaching rate. The experiment showed that there were two reaction modes in the bioleaching process.
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reductive leaching of manganese from low grade Pyrolusite ore in sulfuric acid using pyrolysis pretreated sawdust as a reductant
International Journal of Minerals Metallurgy and Materials, 2016Co-Authors: Yali Feng, Shiyuan ZhangAbstract:Manganese (Mn) leaching and recovery from low-grade Pyrolusite ore were studied using sulfuric acid (H2SO4) as a leachant and pyrolysis-pretreated sawdust as a reductant. The effects of the dosage of pyrolysis-pretreated sawdust to Pyrolusite ore, the concentration of sulfuric acid, the liquid/solid ratio, the leaching temperature, and the leaching time on manganese and iron leaching efficiencies were investigated. Analysis of manganese and iron leaching efficiencies revealed that a high manganese leaching efficiency was achieved with low iron extraction. The optimal leaching efficiency was determined to be 20wt% pyrolysis-pretreated sawdust and 3.0 mol/L H2SO4 using a liquid/ solid ratio of 6.0 mL/g for 90 min at 90°C. Other low-grade Pyrolusite ores were tested, and the results showed that they responded well with manganese leaching efficiencies greater than 98%.
Guo Chen - One of the best experts on this subject based on the ideXlab platform.
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study on thermochemical characteristics properties and pyrolysis kinetics of the mixtures of waste corn stalk and Pyrolusite
Bioresource Technology, 2021Co-Authors: Lei Gao, Yong Yang, Guo Chen, Shenghui Guo, Mamdouh Omran, Jin Chen, Roger RuanAbstract:Abstract As an alternative energy source for fossil energy, use of biomass pyrolysis to reduce Pyrolusite is of great significance for energy conservation, emission reduction and environmental protection. Kinetics and thermodynamics of reducing Pyrolusite using biomass pyrolysis was studied using thermogravimetric analysis analysis. Five non-isothermal methods, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Distributed Activation Energy Model, Starink and Friedman, were employed to calculate the pyrolysis kinetics and thermodynamic parameters. The results showed that Pyrolusite reduction by biomass pyrolysis can be divided into four stages: drying stage (30–175 °C), rapid pyrolysis reduction stage (175–350 °C), slow pyrolysis reduction stage (350–680 °C) and char formation stage (680–900 °C). The apparent activation energy, reaction enthalpy, Gibbs free energy and entropy change of Pyrolusite reduction by biomass pyrolysis was calculated ranges from 170 to 180 kJ/mol, 164 to 174 kJ/mol, 136.97 to 137.25 kJ/mol and 45.67 to 61.91 J/mol·K, respectively. This work provides theoretical basis and practical guidance for the reduction of Pyrolusite by waste corn stalk.
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pilot scale study on enhanced carbothermal reduction of low grade Pyrolusite using microwave heating
Powder Technology, 2020Co-Authors: Jin Chen, Jinhui Peng, Guo Chen, Roger Ruan, C SrinivasakannanAbstract:Abstract Microwave heating through materials' dielectric loss endows energy saving and consumption reduction and production clean characteristics. Pilot-scale study was initiated to evaluate the enhanced effect of microwave heating on carbothermal reduction process of Pyrolusite. Results indicated that carbothermal reduction process for low-grade Pyrolusite was divided into three stages identified by temperatures: 400 °C. Meanwhile, ƞMn value of 95.38% can achieve at 650 °C for 60 min with 15% coal addition, with low Fe2+ content, indicating efficient Pyrolusite reduction by microwave heating. Moreover, MnO2 peaks disappeared and MnO peaks were detected and product surface became loose and porous with numerous cracks and holes, meanwhile grain shape became more regular with a smaller particle size after further microwave treatment. The study highlights that the non-conventional technology by microwave heating to reduce low-grade Pyrolusite is very promising and could be considered for full scale applications.
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high temperature dielectric properties and pyrolysis reduction characteristics of different biomass Pyrolusite mixtures in microwave field
Bioresource Technology, 2019Co-Authors: Jinhui Peng, Guo Chen, Mamdouh Omran, Jin Chen, Roger RuanAbstract:Abstract Exploring the dielectric properties of mineral-biomass mixtures is fundamental to the coupled application with biomass pyrolysis and microwave technology to mineral reduction. In this work, the microwave dielectric properties of five Pyrolusite-biomass mixtures were measured by resonant cavity perturbation technique and the pyrolysis reduction characteristics were systematically investigated, including poplar, pine, ageratina adenophora, rapeseed shell and walnut shell. Results indicated that the dielectric properties commonalities of five mixtures with temperature represented by increasing firstly, dropping intensely and finally rising slightly, with excellent responsiveness to microwaves; which the change trend was mainly attributed to the crystal transformation of amorphous MnO2 and Pyrolusite reduction reactions by biomass pyrolysis. Meanwhile, the heating characteristics successfully matched the dielectric properties of the mixtures, and the Pyrolusite reduction process by biomass can be divided into two stages: biomass pyrolysis and Pyrolusite reduction. The work highlights the universal feasibility of the novel coupled method for mineral reduction.
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effect of microwave heating on the microstructures and kinetics of carbothermal reduction of Pyrolusite ore
Advanced Powder Technology, 2018Co-Authors: Jin Chen, Jinhui Peng, Guo Chen, C Srinivasakannan, Rongsheng RuanAbstract:Abstract This article focuses on the development of phase transformation and morphology of low-grade Pyrolusite during carbothermal reduction using microwave heating. The XRD, SEM and EDS results show that selective carbothermal reduction of MnxOy and FexOy in Pyrolusite is easy to realize with microwave heating, which can reduce MnO2 to MnO, and Fe2O3 to Fe3O4, rather than FeO. It was also observed that the phases of Mn2O3, Mn3O4 and MnO appear at 300 °C, 450 °C and 500 °C, respectively. The MnO phase, formed by the accumulation of MnO sphere particle with a diameter of 266.75–420.05 nm, is loose and porous. At a temperature of 750 °C, the Mn2SiO4 layer of about 316 nm in thickness, tightly wrapping SiO2 particle is generated at the interface between MnO and SiO2 embedded with MnO. Above 650 °C, Fe2O3 in Pyrolusite can be transformed into a very dense Fe3O4 phase.
Steven L. Suib - One of the best experts on this subject based on the ideXlab platform.
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synthesis of single crystal manganese oxide octahedral molecular sieve oms nanostructures with tunable tunnels and shapes
Journal of Physical Chemistry B, 2006Co-Authors: Jikang Yuan, Sinue Gomezmower, Shantakumar Sithambaram, Steven L. SuibAbstract:A new and facile route is reported to manipulate the self-assembly synthesis of hierarchically ordered Rb-OMS-2 and Pyrolusite with an interesting flowerlike morphology by a direct and mild reaction between rubidium chromateand manganese sulfate without any organic templates. The crystal forms, morphologies, and tunnel sizes of the obtained OMS materials can be controlled. A mechanism for the growth of manganese dioxides with flowerlike architectures was proposed. The obtained products exhibit potential for use in catalysis and other applications.
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self assembly of microporous manganese oxide octahedral molecular sieve hexagonal flakes into mesoporous hollow nanospheres
Journal of the American Chemical Society, 2003Co-Authors: Jikang Yuan, Kate Laubernds, Qiuhua Zhang, Steven L. SuibAbstract:Manganese oxide hollow nanospheres were prepared using a straightforward, template-free synthesis. The resulting material was mesoporous, crystalline, and of uniform diameter. The nanospheres were characterized by XRD, HR-SEM, and HR-TEM, and pore size distributions were calculated from nitrogen desorption. Unlike previous synthesis methods that use an inorganic template, this procedure requires no separation after synthesis to remove the template. The nanospheres are composed of hexagonal γ-manganese oxide flakes and are approximately 400 nm in diameter. γ-MnO2 is composed of a ramsdellite matrix (1 × 2 tunnels) with randomly distributed microdomains of Pyrolusite (1 × 1 tunnels). These materials could have applications as cathodic battery materials, oxidation catalysts, catalyst supports, and adsorbents for pollutants.
Jin Chen - One of the best experts on this subject based on the ideXlab platform.
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study on thermochemical characteristics properties and pyrolysis kinetics of the mixtures of waste corn stalk and Pyrolusite
Bioresource Technology, 2021Co-Authors: Lei Gao, Yong Yang, Guo Chen, Shenghui Guo, Mamdouh Omran, Jin Chen, Roger RuanAbstract:Abstract As an alternative energy source for fossil energy, use of biomass pyrolysis to reduce Pyrolusite is of great significance for energy conservation, emission reduction and environmental protection. Kinetics and thermodynamics of reducing Pyrolusite using biomass pyrolysis was studied using thermogravimetric analysis analysis. Five non-isothermal methods, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Distributed Activation Energy Model, Starink and Friedman, were employed to calculate the pyrolysis kinetics and thermodynamic parameters. The results showed that Pyrolusite reduction by biomass pyrolysis can be divided into four stages: drying stage (30–175 °C), rapid pyrolysis reduction stage (175–350 °C), slow pyrolysis reduction stage (350–680 °C) and char formation stage (680–900 °C). The apparent activation energy, reaction enthalpy, Gibbs free energy and entropy change of Pyrolusite reduction by biomass pyrolysis was calculated ranges from 170 to 180 kJ/mol, 164 to 174 kJ/mol, 136.97 to 137.25 kJ/mol and 45.67 to 61.91 J/mol·K, respectively. This work provides theoretical basis and practical guidance for the reduction of Pyrolusite by waste corn stalk.
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pilot scale study on enhanced carbothermal reduction of low grade Pyrolusite using microwave heating
Powder Technology, 2020Co-Authors: Jin Chen, Jinhui Peng, Guo Chen, Roger Ruan, C SrinivasakannanAbstract:Abstract Microwave heating through materials' dielectric loss endows energy saving and consumption reduction and production clean characteristics. Pilot-scale study was initiated to evaluate the enhanced effect of microwave heating on carbothermal reduction process of Pyrolusite. Results indicated that carbothermal reduction process for low-grade Pyrolusite was divided into three stages identified by temperatures: 400 °C. Meanwhile, ƞMn value of 95.38% can achieve at 650 °C for 60 min with 15% coal addition, with low Fe2+ content, indicating efficient Pyrolusite reduction by microwave heating. Moreover, MnO2 peaks disappeared and MnO peaks were detected and product surface became loose and porous with numerous cracks and holes, meanwhile grain shape became more regular with a smaller particle size after further microwave treatment. The study highlights that the non-conventional technology by microwave heating to reduce low-grade Pyrolusite is very promising and could be considered for full scale applications.
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high temperature dielectric properties and pyrolysis reduction characteristics of different biomass Pyrolusite mixtures in microwave field
Bioresource Technology, 2019Co-Authors: Jinhui Peng, Guo Chen, Mamdouh Omran, Jin Chen, Roger RuanAbstract:Abstract Exploring the dielectric properties of mineral-biomass mixtures is fundamental to the coupled application with biomass pyrolysis and microwave technology to mineral reduction. In this work, the microwave dielectric properties of five Pyrolusite-biomass mixtures were measured by resonant cavity perturbation technique and the pyrolysis reduction characteristics were systematically investigated, including poplar, pine, ageratina adenophora, rapeseed shell and walnut shell. Results indicated that the dielectric properties commonalities of five mixtures with temperature represented by increasing firstly, dropping intensely and finally rising slightly, with excellent responsiveness to microwaves; which the change trend was mainly attributed to the crystal transformation of amorphous MnO2 and Pyrolusite reduction reactions by biomass pyrolysis. Meanwhile, the heating characteristics successfully matched the dielectric properties of the mixtures, and the Pyrolusite reduction process by biomass can be divided into two stages: biomass pyrolysis and Pyrolusite reduction. The work highlights the universal feasibility of the novel coupled method for mineral reduction.
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effect of microwave heating on the microstructures and kinetics of carbothermal reduction of Pyrolusite ore
Advanced Powder Technology, 2018Co-Authors: Jin Chen, Jinhui Peng, Guo Chen, C Srinivasakannan, Rongsheng RuanAbstract:Abstract This article focuses on the development of phase transformation and morphology of low-grade Pyrolusite during carbothermal reduction using microwave heating. The XRD, SEM and EDS results show that selective carbothermal reduction of MnxOy and FexOy in Pyrolusite is easy to realize with microwave heating, which can reduce MnO2 to MnO, and Fe2O3 to Fe3O4, rather than FeO. It was also observed that the phases of Mn2O3, Mn3O4 and MnO appear at 300 °C, 450 °C and 500 °C, respectively. The MnO phase, formed by the accumulation of MnO sphere particle with a diameter of 266.75–420.05 nm, is loose and porous. At a temperature of 750 °C, the Mn2SiO4 layer of about 316 nm in thickness, tightly wrapping SiO2 particle is generated at the interface between MnO and SiO2 embedded with MnO. Above 650 °C, Fe2O3 in Pyrolusite can be transformed into a very dense Fe3O4 phase.
Hongjun Wang - One of the best experts on this subject based on the ideXlab platform.
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new understanding of the reduction mechanism of Pyrolusite in the acidithiobacillus ferrooxidans bio leaching system
Electrochimica Acta, 2019Co-Authors: Jinxing Kang, Yali Feng, Xiangyi Deng, Hongjun WangAbstract:Abstract The reductive dissolution of Pyrolusite in simulated Acidithiobacillus ferrooxidans bio-leaching medium was investigated. This study was performed in three stages. First, the advantageous electrochemical test conditions, parallel to the optimal bio-leaching conditions and adopting the Mn reduction rate, were determined by imitated electrolysis. The facilitation of A. ferrooxidans on MnO2 reduction is sensitive to pH and Fe(III) concentration. Second, electrochemical tests revealed that the reductive dissolution of manganese dioxide incorporated two single electron and proton steps-the first exchange of MnO2 to MnO·OH, and then conversion to Mn(OH)2 for diffusion. The results of transient and steady electrochemical measurements indicated that the first electron-transfer significantly affects the rate controlling step of Mn-leaching in control(9K) medium, while using A. ferrooxidans and Fe(III) in the solution tends to enable the leaching rate to be controlled by the latter electron transfer step. Third, the analysis of semiconductor and carrier properties of passive films of Pyrolusite formed in the different solutions, illustrated that the reductive dissolution of manganese dioxide tends to depend on the movement of the holes. The first electron preferentially reacts with the shallow energy level of the O-vacancy to form MnO2·-, which then absorbs H+ to become MnO·OH. The second electron participates in the transformation of MnO·OH to (MnOH)(OH) and then to Mn(OH)2. A. ferrooxidans increases the carrier densities of the passivating film accelerating electron and proton transfer and Fe(III) primarily influences the shallow donor density of oxygen during the first electron-exchange. Additionally, the synergistic effect of A. ferrooxidans and Fe(III) on manganese dioxide ore reductive leaching is confirmed.
