In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnO_2nanoparticles(α-MnO_2@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO_2@C was prepared v...In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnO_2nanoparticles(α-MnO_2@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO_2@C was prepared via a gel formation, using maleic acid(C_4H_4O_4) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnO_2 nanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO_2@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO_2@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnO_2 electrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.展开更多
<div style="text-align:justify;"> In this study a novel manganese dioxide modified nanofiber was facile prepared using the electrospinning technique. The as-prepared manganese dioxide/poly(vinyl alcoho...<div style="text-align:justify;"> In this study a novel manganese dioxide modified nanofiber was facile prepared using the electrospinning technique. The as-prepared manganese dioxide/poly(vinyl alcohol)/poly (acrylic acid) (briefly as MnO<sub>2</sub>-PVA/PAA) was firstly characterized by SEM, FT-IR, XRD, stress-strain test and secondly tested as an adsorbent to remove uranium from aqueous solution. Effect of pH, ionic strength, initial uranium concentration, mixing time, temperature on the adsorption, reusability and adsorption mechanism were illustrated. The theoretical adsorption amount of MnO<sub>2</sub>-PVA/PAA calculated as 398.85 mg/g was competitive compared with the reported values. The study proved MnO<sub>2</sub>-PVA/PAA is promising in the uranium removal from aqueous medium. </div>展开更多
Aqueous zinc-ion battery has attracted much attention due to its low price, high safety, and high theoretical specific capacity. However, most of their performances are limited by the unsatisfied architecture of catho...Aqueous zinc-ion battery has attracted much attention due to its low price, high safety, and high theoretical specific capacity. However, most of their performances are limited by the unsatisfied architecture of cathodes. Herein, we fabricated amorphous manganese dioxide by an in situ deposition method. The amorphous manganese dioxide can directly serve as the cathode of an aqueous zinc-ion battery without a binder. The resultant cathode exhibits a high specific capacity of 133.9 mAh/g at 200 mA/g and a capacity retention of 82% over 50 cycles at 1 A/g.展开更多
Precipitation was carried out to obtain manganese carbonate by adding a precipitating agent, sodium carbonate (NaCO<sub>3</sub>). This was followed by calcination of the manganese carbonate (MnCO<sub>...Precipitation was carried out to obtain manganese carbonate by adding a precipitating agent, sodium carbonate (NaCO<sub>3</sub>). This was followed by calcination of the manganese carbonate (MnCO<sub>3</sub>) to obtain manganese dioxide (MnO<sub>2</sub>). For precipitation tests, a pH ranging from 8 to 10, a time of one to two hours, and a temperature of 25°C and 50°C are the parameters that are considered. The calcination of MnCO<sub>3</sub> is carried out under the following conditions: time (1, 2, 3, and 4 hours) and temperature (370°C, 420°C, and 470°C). It should be noted that the temperature range selected for the calcination tests is based on thermodynamic data obtained using the HSC CHEMISTRY software. The results obtained show an effective recovery of manganese at 25°C, in one hour, with a pH of 8.5 with a precipitation yield and manganese content in the precipitate around 98.43% and 24.21%, respectively. During calcination tests, results show an increase in mass loss, for a constant calcination time, as temperature increases. On the other hand, increasing the calcination time at a given temperature causes an increase in mass loss. However, a significant decrease in mass loss is noted at 3 hours of calcination. The highest mass loss is obtained at a temperature of 470°C after 4 hours of calcination.展开更多
We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanow...We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.展开更多
Graphene/manganese dioxide composites and grapheme/manganese dioxide/sulfur(G/MnO2/S) composite cathode were prepared by hydrothermal method and by vapor permeation, respectively. Their structure, morphology and speci...Graphene/manganese dioxide composites and grapheme/manganese dioxide/sulfur(G/MnO2/S) composite cathode were prepared by hydrothermal method and by vapor permeation, respectively. Their structure, morphology and specific surface area were characterized by X-ray diffraction, electron microanalysis and nitrogen adsorption analysis. The composites show morphology of nanosheets, high specific surface area and even distribution of sulfur. The sulfur accounts for 75% in the G/MnO2/S composite by thermogravimetric analysis. The electrochemical performance of G/S and G/MnO2/S cathode were investigated. The G/MnO2/S composite cathodes show excellent rate performance and cycle stability. At a 0.2C current density, initial discharge specific capacity is 1 061 m A·h·g^-1 and maintains 698 m A·h·g^-1 after 100 cycles;At a 1C current density, maximum discharge capacity reaches 816 m A·h·g^-1 and average capacity decreasing rate is only 0.073%/cycle after running over 400 cycles. Electrochemical mechanism of the composites cathodes was analyzed. The sulfur adsorption of Mn O2 inhibited the loss of active material sulfur, so, the electrochemical performance of the complex was improved.展开更多
Flexible energy-storage devices play a critical role in the development of portable, flexible and wearable electronics. In addition, biological materials including plants or plant-based materials are known for their s...Flexible energy-storage devices play a critical role in the development of portable, flexible and wearable electronics. In addition, biological materials including plants or plant-based materials are known for their safety, biodegradability, biocompatibility, environmental benignancy, and low cost. With respect to these advances, a flexible alkaline zinc-manganese dioxide (Zn-MnO2) battery is fabricated with a kelp-based electrolyte in this study. To the best of our knowledge, pure kelp is utilized as a semi-solid electrolyte for flexible Zn-MnO2 alkaline batteries for the first time, with which the as-assembled battery exhibited a specific capacity of 60 mA·h and could discharge for 120 h. Furthermore, the as-assembled Zn-MnO2 battery can be bent into a ring-shape and power a light-emitting diode screen, showing promising potential for the practical application in the future flexible, portable and biodegradable electronic devices.展开更多
Chemical Manganese Dioxide (CMD) was prepared by an alkali-oxidation method. There are several virtues to this environmental friendly and clean process, including the nontoxic and harmless reagents and products, easy ...Chemical Manganese Dioxide (CMD) was prepared by an alkali-oxidation method. There are several virtues to this environmental friendly and clean process, including the nontoxic and harmless reagents and products, easy operations, no pollutants, easily obtained raw materials and moderate reaction conditions. The synthesized manganese dioxide was characterized by XRD and SEM. The particles were small, consisting primarily of α-MnO2 and γ-MnO2. Experimental results showed that the optimum conditions were: MnSO4?H2O to NaOH ratio, 1.0:2.4; catalyst concentration (catalyst TF-2), 6% of the MnSO4; initial solution pH, 11; reaction time and temperature, 20 min and 80 °C; air flow, 0.20 m3/h; and, agitation rate, 700 r/min. The conversion of MnSO4 can exceed 80% under these optimum conditions.展开更多
The present study investigates the effect of Electrochemical Manganese Dioxide (EMD) by-product as a replacement of cement, on durability of concrete and the corrosion protection of reinforcement steel. Reinforced cem...The present study investigates the effect of Electrochemical Manganese Dioxide (EMD) by-product as a replacement of cement, on durability of concrete and the corrosion protection of reinforcement steel. Reinforced cement mortars were partially immersed in 3.5% w. w NaCl solution and they were exposed to atmospheric conditions for a period of 24 months. Additions of 5% and 10% EMD byproduct were tested. The following techniques were used: half-cell potential measurements (HCP), linear polarization Resistance (LPR), mass loss of reinforcement steel, determination of carbonation depth of mortars, testing of compressive strength, total and open porosity measurements. Based on the up-to-now results of this study, the specimens with addition 10% appear smaller corrosion currents and mass loss of steel than reference specimens. Also, the compressive strength with 10% additive is appeared to be slightly higher from the reference specimens.展开更多
The oxidation of a,b-unsaturated primary and secondary alcohols to corresponding aldehydes and ketones by manganese dioxide in ionic liquids as a safe recyclable and accelerative reaction medium under mild conditions ...The oxidation of a,b-unsaturated primary and secondary alcohols to corresponding aldehydes and ketones by manganese dioxide in ionic liquids as a safe recyclable and accelerative reaction medium under mild conditions are described. The rate of the oxidation reaction is faster and the yield is higher than that with conventional procedures.展开更多
The preparation of chemical manganese dioxide(CMD) from low-grade rhodochrosite ore(LGRO) in Xiushan,Chongqing,was studied and improved,including leaching with sulfuric acid,purifying,crystallizing and decomposing of ...The preparation of chemical manganese dioxide(CMD) from low-grade rhodochrosite ore(LGRO) in Xiushan,Chongqing,was studied and improved,including leaching with sulfuric acid,purifying,crystallizing and decomposing of MnCO3,and refining of primary MnO2.The product was characterized by X-ray diffraction.The results showed that the extraction ratio,the manganese recovery ratio of purifying,crystallization and refining reached 96.8%,93.9%,97.7%and 85.4%,respectively.The optimum conditions of refining were described as follows:liquid(H2SO4)/solid(primary MnO2) ratio was 3 L/g,the concentrations of NaClO exceeded 20%,and reaction time was 3 hours.Under the above conditions,the contents of MnO2and Mn in the obtained manganese dioxide were respectively 85.1%and 53.9%.The refined MnO2can be used as the super grade manganese dioxide mine powder in chemical industry.The XRD indicated that the structure of the product wasγ-MnO2.展开更多
The authors reported a facile method for the synthesis of manganese dioxide without any template and catalyst at a low-temperature. The prepared sample was characterized with X-ray diffraction(XRD), scanning electron ...The authors reported a facile method for the synthesis of manganese dioxide without any template and catalyst at a low-temperature. The prepared sample was characterized with X-ray diffraction(XRD), scanning electron microscopy(SEM), Brunauer-Emmett-Teller(BET) surface analysis, Fourier transform infrared(FTIR) spectrometry, cyclic voltammetry, alternative current(AC) impedance test and battery discharge test. It is found that the prepared sample belongs to α-MnO2 and has a microsphere morphology and a large BET surface area. The electrochemical characterization indicates that the prepared sample displays a larger electrochemical capacitance than the commercial electrolytic manganese dioxides(EMD) in Na2SO4 solution, and exhibits larger discharge capacity than EMD, especially at a high rate discharge condition when it is used as cathode of alkaline Zn/MnO2 battery.展开更多
Grainy electrolytic manganese dioxide was prepared by electrodeposition in a 0.9 mol/L MnSO4 and 2.5 mol/LH2SO4 solution. The structure, particle size and appearance of the grainy electrolytic manganese dioxide were d...Grainy electrolytic manganese dioxide was prepared by electrodeposition in a 0.9 mol/L MnSO4 and 2.5 mol/LH2SO4 solution. The structure, particle size and appearance of the grainy electrolytic manganese dioxide were determined by powder X-ray diffraction, laser particle size analysis and scanning electron micrographs measurements. Current density has important effects on cell voltage, anodic current efficiency and particle size of the grainy electrolytic manganese dioxide, and the optimum current density is 30 A/dm2. The grainy electrolytic manganese dioxide electrodeposited under the optimum conditions consists of γ-MnO2 with an orthorhombic lattice structure; the grainy electrolytic manganese dioxide has a spherical or sphere-like appearance and a narrow particle size distribution with an average particle diameter of 7.237 μm.展开更多
The hydrometallurgical strategy of extracting Mn from low-grade Mn ores has attracted attention for the production of electrolytic manganese metal(EMM). In this work, the reductive dissolution of low-grade Mn O2 ores ...The hydrometallurgical strategy of extracting Mn from low-grade Mn ores has attracted attention for the production of electrolytic manganese metal(EMM). In this work, the reductive dissolution of low-grade Mn O2 ores using toxic nitrocellulose acidic wastewater(NAW) as a reductant was investigated for the first time. Under the optimized conditions of an Mn O2 ore dosage of 100 g·L-1, an ore particle size of-200 mesh, concentrated H2 SO4-to-NAW volume ratio of 0.12, reaction temperature of 90°C, stirring speed at 160 r·min-1, and a contact time of 120 min, the reductive leaching efficiency of Mn and the total organic carbon(TOC) removal efficiency of NAW reached 97.4% and 98.5%, respectively. The residual TOC of 31.6 mg·L-1 did not adversely affect the preparation of EMM. The current process offers a feasible route for the concurrent realization of the reductive leaching of Mn and the treatment of toxic wastewater via a simple one-step process.展开更多
To study the anticlastogenic effect of redistilled cow's urine distillate (RCUD) in human peripheral lymphocytes (HLC) challenged with manganese dioxide and hexavalent chromium. Methods The anticlastogenic activit...To study the anticlastogenic effect of redistilled cow's urine distillate (RCUD) in human peripheral lymphocytes (HLC) challenged with manganese dioxide and hexavalent chromium. Methods The anticlastogenic activity of redistilled cow's urine distillate was studied in human polymorphonuclear leukocytes (HPNLs) and human peripheral lymphocytes in vitro challenged with manganese dioxide and hexavalent chromium as established genotoxicants and clastogens which could cause induction of DNA strand break, chromosomal aberration and micronucleus. Three different levels of RCUD: 1μL/mL, 50μL/mL and 100μL/mL, were used in the study. Results Manganese dioxide and hexavalent chromium caused statistically significant DNA strand break, chromosomal aberration and micronucleus formation, which could be protected by redistilled cow's urine distillate. Conclusion The redistilled cow's urine distillate posseses strong antigenotoxic and anticlastogenic properties against HPNLs and HLC treated with Cr+6 and MnO2. This property is mainly due to the antioxidants present in RCUD.展开更多
The effects of temperature and the concentration of sulfuric acid on the cell voltage, the anode current efficiency of elec- trodeposition and the particle size of grainy electrolytic manganese dioxide (EMD) were inve...The effects of temperature and the concentration of sulfuric acid on the cell voltage, the anode current efficiency of elec- trodeposition and the particle size of grainy electrolytic manganese dioxide (EMD) were investigated. The structure, particle size and appearance of grainy EMD were determined by powder X-ray diffraction, laser particle size analysis and scanning electron mi- crograph measurements. As the concentration of sulfuric acid increases, both the cell voltage and the average anode current efficien- cy decrease. With the increase of electrolysis temperature in the range of 30-60°C, the cell voltage, average anode current efficiency and particle size decrease. The optimum temperature of 30°C and concentration of sulfuric acid of 2.5 mol/L for electrodeposition of the grainy EMD were obtained. XRD patterns show that the grainy EMD electrodeposited under the optimum conditions consists of γ-MnO2 and has an orthorhombic lattice structure. According to the results of SEM, the grainy EMD has a spherical or sphere-like appearance and a narrow particle size distribution with an average size of about 7 μm. The grainy EMD is a promising cathode of rechargeable alkaline batteries for high energy density and a prospective precursor for production of the LiMn2O4 cathode of lithium ion batteries.展开更多
Particulate matter(PM)is the main contributor to air pollution,and filtration has been reported to be promising for PM capturing.Considering the complexity of polluted air(volatile organic compounds(VOCs)and ozone are...Particulate matter(PM)is the main contributor to air pollution,and filtration has been reported to be promising for PM capturing.Considering the complexity of polluted air(volatile organic compounds(VOCs)and ozone are likely concomitant with PM particles)and in view of the versatility of MnO_(2) for the degradation of VOCs and ozone,the feasibility of MnO_(2) materials as PM filteringmediawas investigated in this study,and the effect of crystal structure on PM filtration was clarified.Compared with the layeredδ-MnO_(2),the MnO_(2) with tunnel structure(including 1×2-,2×2-and 3×3-MnO_(2))exhibited greatly enhanced PM removal efficiencies,and particularly,the 3×3-MnO_(2) possessed not only significant activity for adsorbing PM particles but also high utilization efficiency of the active surface.Physicochemical properties of the adsorbents were studied by XRD,ATR,isothermal N_(2) adsorption,SEM and(HR)TEM.The correlation between pore characteristics and particle elimination activity demonstrates that the most developed mesoporous structure of the 3×3-MnO_(2) sample played an important role in strengthening the PM adsorption capability.Further comparison of the surface properties of the fresh and spent samples reveals that with respective to the occasion ofδ-MnO_(2),the structure of 3×3-MnO_(2) was robust enough to resist collapse after PM capturing and the great accommodation of the inorganic and organic PM substances in the voluminous pores induced strong affinity between PM particles and 3×3-MnO_(2).Thereby,a higher particle filtration ability was retained.展开更多
The use of titanium dioxide nanoparticles (nTiO<sub>2</sub>) is gaining interest in agriculture because of their impact on many aspects of plant growth. The present study examines the effects of nTiO<su...The use of titanium dioxide nanoparticles (nTiO<sub>2</sub>) is gaining interest in agriculture because of their impact on many aspects of plant growth. The present study examines the effects of nTiO<sub>2</sub> (5 nm and 10 nm) applied to seeds and the seedlings as a foliar application on various aspects of growth characteristics and biomass accumulation in lettuce (Lactuca sativa, cv. Grand Rapids). Application of 10 nm nTiO<sub>2</sub> to seeds through imbibition resulted in a significant reduction in shoot biomass accumulation while 5 nm nTiO<sub>2</sub> did not affect the biomass accumulation in lettuce. The application of 10 nm nTiO<sub>2</sub> reduced the fresh shoot biomass accumulation by about 18% compared to the control plants. Other growth characteristics such as shoot dry biomass, root fresh and dry biomass, plant height, and leaf area were not affected by the application of both 5 nm and 10 nm nTiO<sub>2</sub>. In addition, foliar application of these nanoparticles to the lettuce seedlings did not have a significant effect on most of the growth parameters examined, and the increasing concentration ranging from 5 nm/L to 400 mg/L did not produce a consistent response in lettuce. Thus, nTiO<sub>2</sub> application to lettuce seeds had a notable negative impact on shoot growth while foliar application did not have a significant effect on many plant growth characteristics. However, foliar applications produced some symptoms of toxicity to the foliage in the form of necrotic or chlorotic patches on the leaves, which were more pronounced with increasing concentrations of both 5 nm and 10 nm nTiO<sub>2</sub>. However, these symptoms were apparent at a concentration as low as 50 mg/L of nTiO<sub>2</sub>. Thus, foliar application of nTiO<sub>2</sub> may not have a significant impact on many of the growth characteristics in lettuce, but it can result in foliar toxicity.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(2014R1A2A1A10050821)
文摘In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnO_2nanoparticles(α-MnO_2@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO_2@C was prepared via a gel formation, using maleic acid(C_4H_4O_4) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnO_2 nanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO_2@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO_2@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnO_2 electrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.
文摘<div style="text-align:justify;"> In this study a novel manganese dioxide modified nanofiber was facile prepared using the electrospinning technique. The as-prepared manganese dioxide/poly(vinyl alcohol)/poly (acrylic acid) (briefly as MnO<sub>2</sub>-PVA/PAA) was firstly characterized by SEM, FT-IR, XRD, stress-strain test and secondly tested as an adsorbent to remove uranium from aqueous solution. Effect of pH, ionic strength, initial uranium concentration, mixing time, temperature on the adsorption, reusability and adsorption mechanism were illustrated. The theoretical adsorption amount of MnO<sub>2</sub>-PVA/PAA calculated as 398.85 mg/g was competitive compared with the reported values. The study proved MnO<sub>2</sub>-PVA/PAA is promising in the uranium removal from aqueous medium. </div>
文摘Aqueous zinc-ion battery has attracted much attention due to its low price, high safety, and high theoretical specific capacity. However, most of their performances are limited by the unsatisfied architecture of cathodes. Herein, we fabricated amorphous manganese dioxide by an in situ deposition method. The amorphous manganese dioxide can directly serve as the cathode of an aqueous zinc-ion battery without a binder. The resultant cathode exhibits a high specific capacity of 133.9 mAh/g at 200 mA/g and a capacity retention of 82% over 50 cycles at 1 A/g.
文摘Precipitation was carried out to obtain manganese carbonate by adding a precipitating agent, sodium carbonate (NaCO<sub>3</sub>). This was followed by calcination of the manganese carbonate (MnCO<sub>3</sub>) to obtain manganese dioxide (MnO<sub>2</sub>). For precipitation tests, a pH ranging from 8 to 10, a time of one to two hours, and a temperature of 25°C and 50°C are the parameters that are considered. The calcination of MnCO<sub>3</sub> is carried out under the following conditions: time (1, 2, 3, and 4 hours) and temperature (370°C, 420°C, and 470°C). It should be noted that the temperature range selected for the calcination tests is based on thermodynamic data obtained using the HSC CHEMISTRY software. The results obtained show an effective recovery of manganese at 25°C, in one hour, with a pH of 8.5 with a precipitation yield and manganese content in the precipitate around 98.43% and 24.21%, respectively. During calcination tests, results show an increase in mass loss, for a constant calcination time, as temperature increases. On the other hand, increasing the calcination time at a given temperature causes an increase in mass loss. However, a significant decrease in mass loss is noted at 3 hours of calcination. The highest mass loss is obtained at a temperature of 470°C after 4 hours of calcination.
基金financial supports provided by National Natural Science Foundation of China(Grant no.51104194 and 51104121)International S&T Cooperation Projects of Chongqing(CSTC 2013 gjhz90001)+1 种基金National Key laboratory of Fundamental Science of Micro/Nano-device and System Technology(2013MS06,Chongqing University)State Education Ministry and Fundamental Research Funds for the Central Universities(Project no.CDJZR14135501 and CDJZR13130036,Chongqing University,PR China)
文摘We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.
基金Supported by the Graduate Freedom Exploration Project Fund of the Central South University(No.502211850).
文摘Graphene/manganese dioxide composites and grapheme/manganese dioxide/sulfur(G/MnO2/S) composite cathode were prepared by hydrothermal method and by vapor permeation, respectively. Their structure, morphology and specific surface area were characterized by X-ray diffraction, electron microanalysis and nitrogen adsorption analysis. The composites show morphology of nanosheets, high specific surface area and even distribution of sulfur. The sulfur accounts for 75% in the G/MnO2/S composite by thermogravimetric analysis. The electrochemical performance of G/S and G/MnO2/S cathode were investigated. The G/MnO2/S composite cathodes show excellent rate performance and cycle stability. At a 0.2C current density, initial discharge specific capacity is 1 061 m A·h·g^-1 and maintains 698 m A·h·g^-1 after 100 cycles;At a 1C current density, maximum discharge capacity reaches 816 m A·h·g^-1 and average capacity decreasing rate is only 0.073%/cycle after running over 400 cycles. Electrochemical mechanism of the composites cathodes was analyzed. The sulfur adsorption of Mn O2 inhibited the loss of active material sulfur, so, the electrochemical performance of the complex was improved.
文摘Flexible energy-storage devices play a critical role in the development of portable, flexible and wearable electronics. In addition, biological materials including plants or plant-based materials are known for their safety, biodegradability, biocompatibility, environmental benignancy, and low cost. With respect to these advances, a flexible alkaline zinc-manganese dioxide (Zn-MnO2) battery is fabricated with a kelp-based electrolyte in this study. To the best of our knowledge, pure kelp is utilized as a semi-solid electrolyte for flexible Zn-MnO2 alkaline batteries for the first time, with which the as-assembled battery exhibited a specific capacity of 60 mA·h and could discharge for 120 h. Furthermore, the as-assembled Zn-MnO2 battery can be bent into a ring-shape and power a light-emitting diode screen, showing promising potential for the practical application in the future flexible, portable and biodegradable electronic devices.
基金National Natural Science Foundation of China (No50704036)the Natural Science Foundation of Hunan Province (No08JJ3027) for their financial support
文摘Chemical Manganese Dioxide (CMD) was prepared by an alkali-oxidation method. There are several virtues to this environmental friendly and clean process, including the nontoxic and harmless reagents and products, easy operations, no pollutants, easily obtained raw materials and moderate reaction conditions. The synthesized manganese dioxide was characterized by XRD and SEM. The particles were small, consisting primarily of α-MnO2 and γ-MnO2. Experimental results showed that the optimum conditions were: MnSO4?H2O to NaOH ratio, 1.0:2.4; catalyst concentration (catalyst TF-2), 6% of the MnSO4; initial solution pH, 11; reaction time and temperature, 20 min and 80 °C; air flow, 0.20 m3/h; and, agitation rate, 700 r/min. The conversion of MnSO4 can exceed 80% under these optimum conditions.
文摘The present study investigates the effect of Electrochemical Manganese Dioxide (EMD) by-product as a replacement of cement, on durability of concrete and the corrosion protection of reinforcement steel. Reinforced cement mortars were partially immersed in 3.5% w. w NaCl solution and they were exposed to atmospheric conditions for a period of 24 months. Additions of 5% and 10% EMD byproduct were tested. The following techniques were used: half-cell potential measurements (HCP), linear polarization Resistance (LPR), mass loss of reinforcement steel, determination of carbonation depth of mortars, testing of compressive strength, total and open porosity measurements. Based on the up-to-now results of this study, the specimens with addition 10% appear smaller corrosion currents and mass loss of steel than reference specimens. Also, the compressive strength with 10% additive is appeared to be slightly higher from the reference specimens.
文摘The oxidation of a,b-unsaturated primary and secondary alcohols to corresponding aldehydes and ketones by manganese dioxide in ionic liquids as a safe recyclable and accelerative reaction medium under mild conditions are described. The rate of the oxidation reaction is faster and the yield is higher than that with conventional procedures.
基金Foundation by the Bureau of Land Resources and Housing Management of Chongqing(Scientific & Technologic Program in 2011)
文摘The preparation of chemical manganese dioxide(CMD) from low-grade rhodochrosite ore(LGRO) in Xiushan,Chongqing,was studied and improved,including leaching with sulfuric acid,purifying,crystallizing and decomposing of MnCO3,and refining of primary MnO2.The product was characterized by X-ray diffraction.The results showed that the extraction ratio,the manganese recovery ratio of purifying,crystallization and refining reached 96.8%,93.9%,97.7%and 85.4%,respectively.The optimum conditions of refining were described as follows:liquid(H2SO4)/solid(primary MnO2) ratio was 3 L/g,the concentrations of NaClO exceeded 20%,and reaction time was 3 hours.Under the above conditions,the contents of MnO2and Mn in the obtained manganese dioxide were respectively 85.1%and 53.9%.The refined MnO2can be used as the super grade manganese dioxide mine powder in chemical industry.The XRD indicated that the structure of the product wasγ-MnO2.
基金Supported by the National Natural Science Foundation of China(No.20873046)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.200805740004)+1 种基金the Natural Science Foundation of Guangdong Province,China(No.10351063101000001)the Fund of Guangdong Province Cooperation of Producing, Studying and Researching,China (No.2011B090400317)
文摘The authors reported a facile method for the synthesis of manganese dioxide without any template and catalyst at a low-temperature. The prepared sample was characterized with X-ray diffraction(XRD), scanning electron microscopy(SEM), Brunauer-Emmett-Teller(BET) surface analysis, Fourier transform infrared(FTIR) spectrometry, cyclic voltammetry, alternative current(AC) impedance test and battery discharge test. It is found that the prepared sample belongs to α-MnO2 and has a microsphere morphology and a large BET surface area. The electrochemical characterization indicates that the prepared sample displays a larger electrochemical capacitance than the commercial electrolytic manganese dioxides(EMD) in Na2SO4 solution, and exhibits larger discharge capacity than EMD, especially at a high rate discharge condition when it is used as cathode of alkaline Zn/MnO2 battery.
文摘Grainy electrolytic manganese dioxide was prepared by electrodeposition in a 0.9 mol/L MnSO4 and 2.5 mol/LH2SO4 solution. The structure, particle size and appearance of the grainy electrolytic manganese dioxide were determined by powder X-ray diffraction, laser particle size analysis and scanning electron micrographs measurements. Current density has important effects on cell voltage, anodic current efficiency and particle size of the grainy electrolytic manganese dioxide, and the optimum current density is 30 A/dm2. The grainy electrolytic manganese dioxide electrodeposited under the optimum conditions consists of γ-MnO2 with an orthorhombic lattice structure; the grainy electrolytic manganese dioxide has a spherical or sphere-like appearance and a narrow particle size distribution with an average particle diameter of 7.237 μm.
基金financially supported by the National Natural Science Foundation of China (No. 21277012)the Nature Scientific Research Foundation of Shaanxi Provincial Education Office of China (No. 17JK0864)the Scientific Research Foundation for Ph D of Yan'an University(No. YDBK2018-10)
文摘The hydrometallurgical strategy of extracting Mn from low-grade Mn ores has attracted attention for the production of electrolytic manganese metal(EMM). In this work, the reductive dissolution of low-grade Mn O2 ores using toxic nitrocellulose acidic wastewater(NAW) as a reductant was investigated for the first time. Under the optimized conditions of an Mn O2 ore dosage of 100 g·L-1, an ore particle size of-200 mesh, concentrated H2 SO4-to-NAW volume ratio of 0.12, reaction temperature of 90°C, stirring speed at 160 r·min-1, and a contact time of 120 min, the reductive leaching efficiency of Mn and the total organic carbon(TOC) removal efficiency of NAW reached 97.4% and 98.5%, respectively. The residual TOC of 31.6 mg·L-1 did not adversely affect the preparation of EMM. The current process offers a feasible route for the concurrent realization of the reductive leaching of Mn and the treatment of toxic wastewater via a simple one-step process.
文摘To study the anticlastogenic effect of redistilled cow's urine distillate (RCUD) in human peripheral lymphocytes (HLC) challenged with manganese dioxide and hexavalent chromium. Methods The anticlastogenic activity of redistilled cow's urine distillate was studied in human polymorphonuclear leukocytes (HPNLs) and human peripheral lymphocytes in vitro challenged with manganese dioxide and hexavalent chromium as established genotoxicants and clastogens which could cause induction of DNA strand break, chromosomal aberration and micronucleus. Three different levels of RCUD: 1μL/mL, 50μL/mL and 100μL/mL, were used in the study. Results Manganese dioxide and hexavalent chromium caused statistically significant DNA strand break, chromosomal aberration and micronucleus formation, which could be protected by redistilled cow's urine distillate. Conclusion The redistilled cow's urine distillate posseses strong antigenotoxic and anticlastogenic properties against HPNLs and HLC treated with Cr+6 and MnO2. This property is mainly due to the antioxidants present in RCUD.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50302016) and the PostdoctoralScience Foundation of Central South University.
文摘The effects of temperature and the concentration of sulfuric acid on the cell voltage, the anode current efficiency of elec- trodeposition and the particle size of grainy electrolytic manganese dioxide (EMD) were investigated. The structure, particle size and appearance of grainy EMD were determined by powder X-ray diffraction, laser particle size analysis and scanning electron mi- crograph measurements. As the concentration of sulfuric acid increases, both the cell voltage and the average anode current efficien- cy decrease. With the increase of electrolysis temperature in the range of 30-60°C, the cell voltage, average anode current efficiency and particle size decrease. The optimum temperature of 30°C and concentration of sulfuric acid of 2.5 mol/L for electrodeposition of the grainy EMD were obtained. XRD patterns show that the grainy EMD electrodeposited under the optimum conditions consists of γ-MnO2 and has an orthorhombic lattice structure. According to the results of SEM, the grainy EMD has a spherical or sphere-like appearance and a narrow particle size distribution with an average size of about 7 μm. The grainy EMD is a promising cathode of rechargeable alkaline batteries for high energy density and a prospective precursor for production of the LiMn2O4 cathode of lithium ion batteries.
基金supported by the National Natural Science Foundation of China(No.21806016)the Fundamental Research Funds for the Central Universities(No.DUT22JC15).
文摘Particulate matter(PM)is the main contributor to air pollution,and filtration has been reported to be promising for PM capturing.Considering the complexity of polluted air(volatile organic compounds(VOCs)and ozone are likely concomitant with PM particles)and in view of the versatility of MnO_(2) for the degradation of VOCs and ozone,the feasibility of MnO_(2) materials as PM filteringmediawas investigated in this study,and the effect of crystal structure on PM filtration was clarified.Compared with the layeredδ-MnO_(2),the MnO_(2) with tunnel structure(including 1×2-,2×2-and 3×3-MnO_(2))exhibited greatly enhanced PM removal efficiencies,and particularly,the 3×3-MnO_(2) possessed not only significant activity for adsorbing PM particles but also high utilization efficiency of the active surface.Physicochemical properties of the adsorbents were studied by XRD,ATR,isothermal N_(2) adsorption,SEM and(HR)TEM.The correlation between pore characteristics and particle elimination activity demonstrates that the most developed mesoporous structure of the 3×3-MnO_(2) sample played an important role in strengthening the PM adsorption capability.Further comparison of the surface properties of the fresh and spent samples reveals that with respective to the occasion ofδ-MnO_(2),the structure of 3×3-MnO_(2) was robust enough to resist collapse after PM capturing and the great accommodation of the inorganic and organic PM substances in the voluminous pores induced strong affinity between PM particles and 3×3-MnO_(2).Thereby,a higher particle filtration ability was retained.
文摘The use of titanium dioxide nanoparticles (nTiO<sub>2</sub>) is gaining interest in agriculture because of their impact on many aspects of plant growth. The present study examines the effects of nTiO<sub>2</sub> (5 nm and 10 nm) applied to seeds and the seedlings as a foliar application on various aspects of growth characteristics and biomass accumulation in lettuce (Lactuca sativa, cv. Grand Rapids). Application of 10 nm nTiO<sub>2</sub> to seeds through imbibition resulted in a significant reduction in shoot biomass accumulation while 5 nm nTiO<sub>2</sub> did not affect the biomass accumulation in lettuce. The application of 10 nm nTiO<sub>2</sub> reduced the fresh shoot biomass accumulation by about 18% compared to the control plants. Other growth characteristics such as shoot dry biomass, root fresh and dry biomass, plant height, and leaf area were not affected by the application of both 5 nm and 10 nm nTiO<sub>2</sub>. In addition, foliar application of these nanoparticles to the lettuce seedlings did not have a significant effect on most of the growth parameters examined, and the increasing concentration ranging from 5 nm/L to 400 mg/L did not produce a consistent response in lettuce. Thus, nTiO<sub>2</sub> application to lettuce seeds had a notable negative impact on shoot growth while foliar application did not have a significant effect on many plant growth characteristics. However, foliar applications produced some symptoms of toxicity to the foliage in the form of necrotic or chlorotic patches on the leaves, which were more pronounced with increasing concentrations of both 5 nm and 10 nm nTiO<sub>2</sub>. However, these symptoms were apparent at a concentration as low as 50 mg/L of nTiO<sub>2</sub>. Thus, foliar application of nTiO<sub>2</sub> may not have a significant impact on many of the growth characteristics in lettuce, but it can result in foliar toxicity.
