Iron-rich electrolytic manganese residue(IREMR)is an industrial waste produced during the processing of electrolytic metal manganese,and it contains certain amounts of Fe and Mn resources and other heavy metals.In thi...Iron-rich electrolytic manganese residue(IREMR)is an industrial waste produced during the processing of electrolytic metal manganese,and it contains certain amounts of Fe and Mn resources and other heavy metals.In this study,the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR.The effects of IREMR and H2SO4 mass ratio,current density,reaction temper-ature,and electrolytic time on the leaching and current efficiencies of Fe were studied.According to the results,high-purity Fe powder can be recovered from the cathode plate,and the slurry electrolyte can be recycled.The leaching efficiency,current efficiency,and purity of Fe reached 92.58%,80.65%,and 98.72wt%,respectively,at a 1:2.5 mass ratio of H2SO4 and IREMR,reaction temperature of 60℃,electric current density of 30 mA/cm^(2),and reaction time of 8 h.In addition,vibrating sample magnetometer(VSM)analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m,which reached the advanced magnetic grade of electrical pure-iron powder(DT4A coercivity standard).The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.展开更多
Electrolytic manganese residue(EMR)can cause serious environmental and biological hazards.In order to solve the problem,zeolite A(EMRZA)and zeolite X(EMRZX)were synthesized by EMR.The pure phase zeolites were synthesi...Electrolytic manganese residue(EMR)can cause serious environmental and biological hazards.In order to solve the problem,zeolite A(EMRZA)and zeolite X(EMRZX)were synthesized by EMR.The pure phase zeolites were synthesized by alkaline melting and hydrothermal two-step process,which had high crystallinity and excellent crystal control.And the optimum conditions for synthesis of zeolite were investigated:NaOH-EMR mass ratio=1.2,L/S=10,hydrothermal temperature=90℃,and hydrothermal time=6 h.Then,EMRZA and EMRZX showed excellent adsorption of Cd^(2+).When T=25℃,time=120min,pH=6,C0=518 mg·L^(-1),and quantity of absorbent=1.5 g·L^(-1),the adsorption capacities of EMRZA and EMRZX reached 314.2 and 289,5 mg·g^(-1),respectively,In addition,after three repeated adsorption-desorption cycles,EMRZA and EMRZX retained 80%and 74%of the initial zeolites removal rates,respectively.Moreover,adsorption results followed quasi-second-order kinetics and monolayer adsorption,which was regulated by a combination of chemisorption and intra-particle diffusion mechanisms.The adsorption mechanism was ions exchange between Cd^(2+)and Na+.In summary,it has been confirmed that EMRZA and EMRZX can be reused as highly efficient adsorbents to treat Cd^(2+)-contaminated wastewater.展开更多
An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed,in which the electrolytic manganese residue(EMR)was initially calcined for cement buffering;the...An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed,in which the electrolytic manganese residue(EMR)was initially calcined for cement buffering;then the generated SO2-containing flue gas was managed using manganese oxide ore and anolyte(MOOA)desulfurization;at last,the desulfurized slurry was introduced to the electrolytic manganese production(EMP).Results showed that 4.0 wt%coke addition reduced the sulfur of calcined EMR to 0.9%,thereby satisfying the cement-buffer requirement.Pilot-scale desulfurization showed that about 7.5 vol%of high SO2 containing flue gas can be cleaned to less than 0.1 vol%through a five-stage countercurrent MOOA desulfurization.The desulfurized slurry had 42.44 g·L-Mn2+and 1.92 g·L-1 S2 O62-,which was suitable for electrowinning after purification,and the purity of manganese product was 99.93%,satisfy the National Standard of China YB/T051-2015.This new integrated technology fulfilled 99.7%of sulfur reutilization from the EMR and 94.1%was effectively used to the EMP.The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge,which promoted the cleaner production of EMP industry.展开更多
Electrolytic manganese residue (EMR) is a waste from electrolytic manganese industry that contains high concentration of toxic substances. Since the EMR disposal in landfill sites has a serious environmental impact,...Electrolytic manganese residue (EMR) is a waste from electrolytic manganese industry that contains high concentration of toxic substances. Since the EMR disposal in landfill sites has a serious environmental impact, new ways of EMR utilization are being sought. Considering the melting of EMR to a glass at high temperature was a relatively less energy-intensive process, EMR was first made into a base glass and then the ground base glass was heat-treated in a certain procedure to make a glass-ceramic and the crystallization process was studied. It was determined by X-ray diffraction (XRD) that the primary crystalline phases of the EMR glass-ceramic were diopside and anorthite, which formed the surface crystallization mechanism with a crystallization activation energy of 429 kJ/mol. Scanning electron microscopy (SEM) observation showed that a layer of small spherical particles with an average size of about 0.5 ~tm were covered on the glass matrix surface, and among them there were some big particles. The low melting temperature and crystallization activation energy make it promising to reuse EMR for glass-ceramic production.展开更多
The online flow injection preconcentration and electrothermal atomic absorption spectrometry method were used for the determination of trace nickel in electrolytic manganese samples by sorption on a conical minicolumn...The online flow injection preconcentration and electrothermal atomic absorption spectrometry method were used for the determination of trace nickel in electrolytic manganese samples by sorption on a conical minicolumn packed with activated carbon at pH 9.0. The nickel was eluted from the minicolumn with 10%(v/v) nitric acid. An enrichment factor of 190-fold for a sample volume of 10mL was obtained. The detection limit (DL) of nickel with the use of the preconcentration method was 13ng·g -1in the original solid sample. The precision for 10 replicate determinations at 150ng·g -1 nickel concentration was 5.2% relative standard deviation (RSD). The calibration graph was linear with a correlation coefficient of r=0.9996 up to concentration of 660ng·g -1 nickel.展开更多
The effects of four types of graphite tube and five matrix modifiers on the determination of selenium by graphite furnace atomic absorption spectrometry were compared.The results show that platform thermolysis coat gr...The effects of four types of graphite tube and five matrix modifiers on the determination of selenium by graphite furnace atomic absorption spectrometry were compared.The results show that platform thermolysis coat graphite tube and magnesium nitrate and cobaltco as matrix modifer can get a high sensitivity and a good recovery.The optimized working conditions and interference in the determination were invesigated.This result is consistent with that of XRF.The recovery is from 100.8 % to102.2 %,the relative standard deviation is from 3.47% to 5.56 % (n=9),and the detection limit of selenium is 378 pg (C=44.5μg/g to 97.3μg/g.).The proposed method can be applied to the rapid determination of selenium in electrolytic manganese.展开更多
Electrolytic manganese metal residue(EMMR)harmless treatment has always lacked a low-cost and quick processing technology.In this study,surfactants,namely tetradecyl trimethylammonium chloride(TTC),sodium dodecyl benz...Electrolytic manganese metal residue(EMMR)harmless treatment has always lacked a low-cost and quick processing technology.In this study,surfactants,namely tetradecyl trimethylammonium chloride(TTC),sodium dodecyl benzene sulfonate(SDBS),sodium lignin sulfonate(SLS),and octadecyl trimethylammonium chloride(OTC),were used in the solidification of Mn^(2+)and removal of NH_(4)^(+)-N from EMMR.The Mn^(2+)and NH_(4)^(+)-N concentrations under different reaction conditions,Mn^(2+)solidification and NH_(4)^(+)-N removal mechanisms,and leaching behavior were studied.The results revealed that the surfactants could enhance the Mn^(2+)solidification and NH_(4)^(+)-N removal from EMMR,and the order of enhancement was as follows:TTC>SDBS>OTC>SLS.The NH_(4)^(+)-N and Mn^(2+)concentrations were 12.3 and 0.05 mg·L^(-1)with the use of 60.0 mg·kg^(-1)TTC under optimum conditions(solid–liquid ratio of 1.5:1,EMMR to BRM mass ratio of 100:8,temperature of 20℃,and reaction duration of 12 h),which met the integrated wastewater discharge standard(GB8978-1996).Mn^(2+)was mainly solidified as Mn(OH)_(2),MnOOH and MnSiO_(3),and NH_(4)^(+)-N in EMMR was mostly removed in the form of ammonia.The results of this study could provide a new idea for cost-effective EMMR harmless treatment.展开更多
The effects of temperature and the concentration of sulfuric acid on the cell voltage, the anode current efficiency of electrodeposition 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 electrodeposition 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 micrograph measurements. As the concentration of sulfuric acid increases, both the cell voltage and the average anode current efficiency decrease. With the increase of electrolysis temperature in the range of 30-60℃, the cell voltage, average anode current efficiency and particle size decrease. The optimum temperature of 30℃ 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 7μm. 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
Remelting rejected electrolytic manganese metal (EMM) scrap was investigated by electroslag remelting (ESR) process through industrial experiment. The results indicated that the ANF-6 slag (70 wt.% CaF_(2) + 30 wt.% A...Remelting rejected electrolytic manganese metal (EMM) scrap was investigated by electroslag remelting (ESR) process through industrial experiment. The results indicated that the ANF-6 slag (70 wt.% CaF_(2) + 30 wt.% Al_(2)O_(3)) and deoxidizer could promote the desulfurization of ESR manganese in an air atmosphere. Under an air atmosphere, the sulfur in the ingot decreased to 0.0534 wt.% with a desulfurization ratio of ESR manganese of 53.2% by using ANF-6 slag and water-cooled copper electrode electroslag remelting rejected EMM scrap, suggesting its efficient removal. The electroslag ingots exhibited uneven chemical composition in an air atmosphere and cooling condition of the ESR process. The metal manganese could be oxidized by electroslag remelting of rejected EMM scrap in an air atmosphere with MnO content in the final slag of 21.9 wt.%. Besides, the activity of MnO in slag increased with increasing remelting temperature, resulting in a reduction in the slag–manganese sulfur partition ratio and desulfurization ratio. Moreover, with the accumulation of sulfur in slag and the oxidation of metallic manganese liquid, the slag showed a lower cleanliness and more oxidation, leading to an increase in sulfur and oxygen content in the electroslag ingot with the increase in ingot height.展开更多
The recycling rate of rejected electrolytic manganese metal(EMM)scrap can be increased by inhibiting the manganese metal(MM)vaporization during the remelting process with electroslag.However,if the latter is achieved ...The recycling rate of rejected electrolytic manganese metal(EMM)scrap can be increased by inhibiting the manganese metal(MM)vaporization during the remelting process with electroslag.However,if the latter is achieved by reducing the remelting temperature,the desulfurization behavior will deteriorate.Therefore,Na_(2)O-containing electroslag and metallic additive were used to increase the rejected EMM scrap recovery ratio.The respective high-temperature experiment was conducted in a MoSi_(2) electrical resistance furnace filled with fluid argon at 1673 K using five different types of electroslag with the Na_(2)O content ranging from 5.81%to 15.71%.High-purity metallic magnesium and magnesium calcium alloy additives were used as deoxidizers.The addition of Na_(2)O and metallic additives effectively promoted the desulfurization and deoxidization of MM.The removal of sulfur and oxygen by the interaction between Na_(2)O-containing electroslag melt and molten MM with metallic additive was analyzed from the thermodynamic and kinetic standpoints.The effect of Na_(2)O-containing electroslag volatilization on desulfurization and deoxidization was considered.With an increase in Na_(2)O content in the slag,the mass loss rates of Na_(2)O and electroslag rose,as well as the final sulfur partition ratio.If the Na_(2)O content volatilized in the slag melt did not exceed 10.44%,the sulfur removal ratio was increased by high sulfide capacity and CaO activity in all slags due to the addition of Na_(2)O.The rejected EMM scrap deoxidization ratio grew with the increased activity of CaO and reduced activity of Al_(2)O_(3) in the molten slag,caused by the increased Na_(2)O content in the molten slag.The addition of metallic Mg and Mg-Ca alloy indirectly promoted desulfurization and deoxidization by reducing the MnO content in the rejected EMM scrap and growing slag oxidability.The Mg-Ca alloy could also react with dissolved sulfur and oxygen,directly promoting desulfurization and deoxidization processes.The Na_(2)O content in slag should not exceed 10.44%to ensure the high desulfurization and deoxidization abilities,fluidity and low volatilization of slag.展开更多
Electrolytic manganese residue(EMR) is the waste slag generated from the electrolysis manganese industry.As a promising exploitable adsorbent,EMR has become a hot research topic.However,EMR’s low adsorption capacity ...Electrolytic manganese residue(EMR) is the waste slag generated from the electrolysis manganese industry.As a promising exploitable adsorbent,EMR has become a hot research topic.However,EMR’s low adsorption capacity has limited its applications as an efficient adsorbent.In this study,the EMR was mixed with serpentine and calcined(at 800℃ for 2 h) to prepare a composite adsorbent(S-EMR) with its specific surface area of 11.998 m^(2)·g^(-1)(increased compared to the original EMR) and improved adsorption capacities for Cd^(2+)(98.05 mg·g^(-1)) and Pb^(2+)(565.81 mg·g^(-1)).Kinetic studies have shown that the pseudo-first-order kinetics(PSO)model could best describe the adsorption kinetics of S-EMR for Cd^(2+)/Pb^(2+),implying that the chemisorption process is the rate-limiting step.The effects of different interfering ions on S-EMR’ s adsorption for Cd^(2+)/Pb^(2+)may be due to the difference in their electronegativity.Results of response surface methodology tests showed that pH had the highest influence on adsorption,and the removal efficiency of S-EMR reached 99.92% for Cd(Ⅱ) and 94.00%for Pb(Ⅱ).X-ray photoelectron spectroscopy(XPS) analyses revealed that chemical precipitation was the predominant mechanism for Cd^(2+)/Pb^(2+)removal,and the adsorption mechanisms were associated with ion exchange and electrostatic attraction.The results showed that S-EMR could be used as an effective adsorbent for the removal of Cd(Ⅱ)/Pb(Ⅱ) from water bodies,rendering dual benefits of pollution control and resource recovery.展开更多
A new type of high efficient Ti composite anodes for electrodeposition of MnO 2 was successfully developed and was widely satisfied with production in many factories in China. The process parameters of electrolysis i...A new type of high efficient Ti composite anodes for electrodeposition of MnO 2 was successfully developed and was widely satisfied with production in many factories in China. The process parameters of electrolysis in using the composite anodes were optimized and discussed.展开更多
The effects of the electro-deposition conditions on the crystal structure and the properties of electrolytic manganese dioxide(EMD) were investigated in this paper. The results show that EMD was γ-crystal, with sand-...The effects of the electro-deposition conditions on the crystal structure and the properties of electrolytic manganese dioxide(EMD) were investigated in this paper. The results show that EMD was γ-crystal, with sand-like rough interface. The optimal preparation conditions of EMD were 30 min deposition time, and p H=1.0 in Mn SO4-H2SO4 solution at 50 ?C. Surfactant(P1) was conducive to the uniform and stable surface of γ-Mn O2 film, the impedance and the specific surface area of the electrode modified with γ-Mn O2 increased by 21.4 times and 75.6 times, respectively. The redox reversibility and the resolution ratio of characteristic peaks with the modified electrode were significantly improved in the benzodiazepines electrochemical reaction. The achievement illustrated that the controllable synthesis of γ-Mn O2 film thickness was practical in electrochemical sensors, and the determination reliability of benzodiazepines was improved with γ-Mn O2 modified electrodes used in environment monitoring technology.展开更多
基金supported by the Key Research and Development Program of Guangxi Province,China (No.AB23075174)the National Natural Science Foundation of China (No.52174386)the Science and Technology Plan Project of Sichuan Province,China (No.2022YFS0459).
文摘Iron-rich electrolytic manganese residue(IREMR)is an industrial waste produced during the processing of electrolytic metal manganese,and it contains certain amounts of Fe and Mn resources and other heavy metals.In this study,the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR.The effects of IREMR and H2SO4 mass ratio,current density,reaction temper-ature,and electrolytic time on the leaching and current efficiencies of Fe were studied.According to the results,high-purity Fe powder can be recovered from the cathode plate,and the slurry electrolyte can be recycled.The leaching efficiency,current efficiency,and purity of Fe reached 92.58%,80.65%,and 98.72wt%,respectively,at a 1:2.5 mass ratio of H2SO4 and IREMR,reaction temperature of 60℃,electric current density of 30 mA/cm^(2),and reaction time of 8 h.In addition,vibrating sample magnetometer(VSM)analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m,which reached the advanced magnetic grade of electrical pure-iron powder(DT4A coercivity standard).The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.
基金supported by the National Natural Science Foundation of China(52164036,U1960201,51764007)the Guizhou Province Graduate Research Fund(YJSKYJJ(2021)003).
文摘Electrolytic manganese residue(EMR)can cause serious environmental and biological hazards.In order to solve the problem,zeolite A(EMRZA)and zeolite X(EMRZX)were synthesized by EMR.The pure phase zeolites were synthesized by alkaline melting and hydrothermal two-step process,which had high crystallinity and excellent crystal control.And the optimum conditions for synthesis of zeolite were investigated:NaOH-EMR mass ratio=1.2,L/S=10,hydrothermal temperature=90℃,and hydrothermal time=6 h.Then,EMRZA and EMRZX showed excellent adsorption of Cd^(2+).When T=25℃,time=120min,pH=6,C0=518 mg·L^(-1),and quantity of absorbent=1.5 g·L^(-1),the adsorption capacities of EMRZA and EMRZX reached 314.2 and 289,5 mg·g^(-1),respectively,In addition,after three repeated adsorption-desorption cycles,EMRZA and EMRZX retained 80%and 74%of the initial zeolites removal rates,respectively.Moreover,adsorption results followed quasi-second-order kinetics and monolayer adsorption,which was regulated by a combination of chemisorption and intra-particle diffusion mechanisms.The adsorption mechanism was ions exchange between Cd^(2+)and Na+.In summary,it has been confirmed that EMRZA and EMRZX can be reused as highly efficient adsorbents to treat Cd^(2+)-contaminated wastewater.
基金supported by the National Key R&D Program of China(No.2018YFC0213405)。
文摘An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed,in which the electrolytic manganese residue(EMR)was initially calcined for cement buffering;then the generated SO2-containing flue gas was managed using manganese oxide ore and anolyte(MOOA)desulfurization;at last,the desulfurized slurry was introduced to the electrolytic manganese production(EMP).Results showed that 4.0 wt%coke addition reduced the sulfur of calcined EMR to 0.9%,thereby satisfying the cement-buffer requirement.Pilot-scale desulfurization showed that about 7.5 vol%of high SO2 containing flue gas can be cleaned to less than 0.1 vol%through a five-stage countercurrent MOOA desulfurization.The desulfurized slurry had 42.44 g·L-Mn2+and 1.92 g·L-1 S2 O62-,which was suitable for electrowinning after purification,and the purity of manganese product was 99.93%,satisfy the National Standard of China YB/T051-2015.This new integrated technology fulfilled 99.7%of sulfur reutilization from the EMR and 94.1%was effectively used to the EMP.The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge,which promoted the cleaner production of EMP industry.
基金the National High Technology Research and Development Program (‘863’ Program) of China (No. 2008AA031206)Key Scientific and Technological Projects of Chongqing (No. CSTC2007AB4019)
文摘Electrolytic manganese residue (EMR) is a waste from electrolytic manganese industry that contains high concentration of toxic substances. Since the EMR disposal in landfill sites has a serious environmental impact, new ways of EMR utilization are being sought. Considering the melting of EMR to a glass at high temperature was a relatively less energy-intensive process, EMR was first made into a base glass and then the ground base glass was heat-treated in a certain procedure to make a glass-ceramic and the crystallization process was studied. It was determined by X-ray diffraction (XRD) that the primary crystalline phases of the EMR glass-ceramic were diopside and anorthite, which formed the surface crystallization mechanism with a crystallization activation energy of 429 kJ/mol. Scanning electron microscopy (SEM) observation showed that a layer of small spherical particles with an average size of about 0.5 ~tm were covered on the glass matrix surface, and among them there were some big particles. The low melting temperature and crystallization activation energy make it promising to reuse EMR for glass-ceramic production.
文摘The online flow injection preconcentration and electrothermal atomic absorption spectrometry method were used for the determination of trace nickel in electrolytic manganese samples by sorption on a conical minicolumn packed with activated carbon at pH 9.0. The nickel was eluted from the minicolumn with 10%(v/v) nitric acid. An enrichment factor of 190-fold for a sample volume of 10mL was obtained. The detection limit (DL) of nickel with the use of the preconcentration method was 13ng·g -1in the original solid sample. The precision for 10 replicate determinations at 150ng·g -1 nickel concentration was 5.2% relative standard deviation (RSD). The calibration graph was linear with a correlation coefficient of r=0.9996 up to concentration of 660ng·g -1 nickel.
文摘The effects of four types of graphite tube and five matrix modifiers on the determination of selenium by graphite furnace atomic absorption spectrometry were compared.The results show that platform thermolysis coat graphite tube and magnesium nitrate and cobaltco as matrix modifer can get a high sensitivity and a good recovery.The optimized working conditions and interference in the determination were invesigated.This result is consistent with that of XRF.The recovery is from 100.8 % to102.2 %,the relative standard deviation is from 3.47% to 5.56 % (n=9),and the detection limit of selenium is 378 pg (C=44.5μg/g to 97.3μg/g.).The proposed method can be applied to the rapid determination of selenium in electrolytic manganese.
基金supported by National Natural Science Foundation of China(52174386,21806132)the National Key Research and Development Program of China(2018YFC1903500)+1 种基金the Science and Technology Plan Project of Sichuan Province(2021YFH0058)the Key Research and Development Program of Guangxi Province(AB18126088)。
文摘Electrolytic manganese metal residue(EMMR)harmless treatment has always lacked a low-cost and quick processing technology.In this study,surfactants,namely tetradecyl trimethylammonium chloride(TTC),sodium dodecyl benzene sulfonate(SDBS),sodium lignin sulfonate(SLS),and octadecyl trimethylammonium chloride(OTC),were used in the solidification of Mn^(2+)and removal of NH_(4)^(+)-N from EMMR.The Mn^(2+)and NH_(4)^(+)-N concentrations under different reaction conditions,Mn^(2+)solidification and NH_(4)^(+)-N removal mechanisms,and leaching behavior were studied.The results revealed that the surfactants could enhance the Mn^(2+)solidification and NH_(4)^(+)-N removal from EMMR,and the order of enhancement was as follows:TTC>SDBS>OTC>SLS.The NH_(4)^(+)-N and Mn^(2+)concentrations were 12.3 and 0.05 mg·L^(-1)with the use of 60.0 mg·kg^(-1)TTC under optimum conditions(solid–liquid ratio of 1.5:1,EMMR to BRM mass ratio of 100:8,temperature of 20℃,and reaction duration of 12 h),which met the integrated wastewater discharge standard(GB8978-1996).Mn^(2+)was mainly solidified as Mn(OH)_(2),MnOOH and MnSiO_(3),and NH_(4)^(+)-N in EMMR was mostly removed in the form of ammonia.The results of this study could provide a new idea for cost-effective EMMR harmless treatment.
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 electrodeposition 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 micrograph measurements. As the concentration of sulfuric acid increases, both the cell voltage and the average anode current efficiency decrease. With the increase of electrolysis temperature in the range of 30-60℃, the cell voltage, average anode current efficiency and particle size decrease. The optimum temperature of 30℃ 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 7μm. 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support from the National Natural Science Foundation of China(Grant No.51804227).
文摘Remelting rejected electrolytic manganese metal (EMM) scrap was investigated by electroslag remelting (ESR) process through industrial experiment. The results indicated that the ANF-6 slag (70 wt.% CaF_(2) + 30 wt.% Al_(2)O_(3)) and deoxidizer could promote the desulfurization of ESR manganese in an air atmosphere. Under an air atmosphere, the sulfur in the ingot decreased to 0.0534 wt.% with a desulfurization ratio of ESR manganese of 53.2% by using ANF-6 slag and water-cooled copper electrode electroslag remelting rejected EMM scrap, suggesting its efficient removal. The electroslag ingots exhibited uneven chemical composition in an air atmosphere and cooling condition of the ESR process. The metal manganese could be oxidized by electroslag remelting of rejected EMM scrap in an air atmosphere with MnO content in the final slag of 21.9 wt.%. Besides, the activity of MnO in slag increased with increasing remelting temperature, resulting in a reduction in the slag–manganese sulfur partition ratio and desulfurization ratio. Moreover, with the accumulation of sulfur in slag and the oxidation of metallic manganese liquid, the slag showed a lower cleanliness and more oxidation, leading to an increase in sulfur and oxygen content in the electroslag ingot with the increase in ingot height.
基金The authors appreciate the financial support from the National Natural Science Foundation of China(Grant No.51804227).
文摘The recycling rate of rejected electrolytic manganese metal(EMM)scrap can be increased by inhibiting the manganese metal(MM)vaporization during the remelting process with electroslag.However,if the latter is achieved by reducing the remelting temperature,the desulfurization behavior will deteriorate.Therefore,Na_(2)O-containing electroslag and metallic additive were used to increase the rejected EMM scrap recovery ratio.The respective high-temperature experiment was conducted in a MoSi_(2) electrical resistance furnace filled with fluid argon at 1673 K using five different types of electroslag with the Na_(2)O content ranging from 5.81%to 15.71%.High-purity metallic magnesium and magnesium calcium alloy additives were used as deoxidizers.The addition of Na_(2)O and metallic additives effectively promoted the desulfurization and deoxidization of MM.The removal of sulfur and oxygen by the interaction between Na_(2)O-containing electroslag melt and molten MM with metallic additive was analyzed from the thermodynamic and kinetic standpoints.The effect of Na_(2)O-containing electroslag volatilization on desulfurization and deoxidization was considered.With an increase in Na_(2)O content in the slag,the mass loss rates of Na_(2)O and electroslag rose,as well as the final sulfur partition ratio.If the Na_(2)O content volatilized in the slag melt did not exceed 10.44%,the sulfur removal ratio was increased by high sulfide capacity and CaO activity in all slags due to the addition of Na_(2)O.The rejected EMM scrap deoxidization ratio grew with the increased activity of CaO and reduced activity of Al_(2)O_(3) in the molten slag,caused by the increased Na_(2)O content in the molten slag.The addition of metallic Mg and Mg-Ca alloy indirectly promoted desulfurization and deoxidization by reducing the MnO content in the rejected EMM scrap and growing slag oxidability.The Mg-Ca alloy could also react with dissolved sulfur and oxygen,directly promoting desulfurization and deoxidization processes.The Na_(2)O content in slag should not exceed 10.44%to ensure the high desulfurization and deoxidization abilities,fluidity and low volatilization of slag.
基金financially supported by the Open-Up and Innovation Funds of Hubei Three Gorges Laboratory (No.SK211004)。
文摘Electrolytic manganese residue(EMR) is the waste slag generated from the electrolysis manganese industry.As a promising exploitable adsorbent,EMR has become a hot research topic.However,EMR’s low adsorption capacity has limited its applications as an efficient adsorbent.In this study,the EMR was mixed with serpentine and calcined(at 800℃ for 2 h) to prepare a composite adsorbent(S-EMR) with its specific surface area of 11.998 m^(2)·g^(-1)(increased compared to the original EMR) and improved adsorption capacities for Cd^(2+)(98.05 mg·g^(-1)) and Pb^(2+)(565.81 mg·g^(-1)).Kinetic studies have shown that the pseudo-first-order kinetics(PSO)model could best describe the adsorption kinetics of S-EMR for Cd^(2+)/Pb^(2+),implying that the chemisorption process is the rate-limiting step.The effects of different interfering ions on S-EMR’ s adsorption for Cd^(2+)/Pb^(2+)may be due to the difference in their electronegativity.Results of response surface methodology tests showed that pH had the highest influence on adsorption,and the removal efficiency of S-EMR reached 99.92% for Cd(Ⅱ) and 94.00%for Pb(Ⅱ).X-ray photoelectron spectroscopy(XPS) analyses revealed that chemical precipitation was the predominant mechanism for Cd^(2+)/Pb^(2+)removal,and the adsorption mechanisms were associated with ion exchange and electrostatic attraction.The results showed that S-EMR could be used as an effective adsorbent for the removal of Cd(Ⅱ)/Pb(Ⅱ) from water bodies,rendering dual benefits of pollution control and resource recovery.
文摘A new type of high efficient Ti composite anodes for electrodeposition of MnO 2 was successfully developed and was widely satisfied with production in many factories in China. The process parameters of electrolysis in using the composite anodes were optimized and discussed.
基金Funded by the Fundamental and Advanced Research Projects of Chongqing Science and Technology Commission(No.2013jj B20001)
文摘The effects of the electro-deposition conditions on the crystal structure and the properties of electrolytic manganese dioxide(EMD) were investigated in this paper. The results show that EMD was γ-crystal, with sand-like rough interface. The optimal preparation conditions of EMD were 30 min deposition time, and p H=1.0 in Mn SO4-H2SO4 solution at 50 ?C. Surfactant(P1) was conducive to the uniform and stable surface of γ-Mn O2 film, the impedance and the specific surface area of the electrode modified with γ-Mn O2 increased by 21.4 times and 75.6 times, respectively. The redox reversibility and the resolution ratio of characteristic peaks with the modified electrode were significantly improved in the benzodiazepines electrochemical reaction. The achievement illustrated that the controllable synthesis of γ-Mn O2 film thickness was practical in electrochemical sensors, and the determination reliability of benzodiazepines was improved with γ-Mn O2 modified electrodes used in environment monitoring technology.