Experiments comparing microwave blank roasting and conventional blank roasting for typical vanadium-bearing stone coal from Hubei Province in central China, in which vanadium is present in muscovite, were conducted to...Experiments comparing microwave blank roasting and conventional blank roasting for typical vanadium-bearing stone coal from Hubei Province in central China, in which vanadium is present in muscovite, were conducted to investigate the effects of roasting temperature, roasting time, H2SO4 concentration, and leaching time on vanadium extraction. The results show that the vanadium leaching efficiency is 84% when the sample is roasted at 800°C for 30 min by microwave irradiation and the H2SO4 concentration, liquid/solid ratio, leaching temperature, and leaching time are set as 20vol%, 1.5:1 m L·g-1, 95°C, and 8 h, respectively. However, the vanadium leaching efficiency achieved for the sample subjected to conventional roasting at 900°C for 60 min is just 71% under the same leaching conditions. Scanning electron microscopy(SEM) analysis shows that the microwave roasted samples contain more cracks and that the particles are more porous compared to the conventionally roasted samples. According to the results of X-ray diffraction(XRD) and Fourier-transform infrared(FTIR) analyses, neither of these roasting methods could completely destroy the mica lattice structure under the experimental conditions; however, both methods deformed the muscovite structure and facilitated the leaching process. Comparing with conventional roasting, microwave roasting causes a greater deformation of the mineral structure at a lower temperature for a shorter roasting time.展开更多
The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation a...The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation and calcium fluoride(Ca F_2) on the vanadium leaching efficiency. It is confirmed that the vanadium leaching process can be improved by microwave irradiation when Ca F_2 is present. The leaching rate of vanadium under microwave irradiation is increased by 8%–15% when 5wt% Ca F_2 is added; by contrast,in the absence of Ca F_2,the leaching rate is almost unaffected compared to that by conventional heating. Morphological analysis reveals that the particles are gradually eroded by acid under microwave irradiation,whereas some of the fine particles in samples subjected to conventional heating are tightly covered by a flocculent silicate product. Moreover,a large amount of Al and V and a small amount of Si are dissolved from samples under microwave heating,as revealed by the elemental analysis of leachates. Fourier transform infrared spectroscopic analysis also indicates a higher mass transfer coefficient in the diffusion layer of the raw material by microwave irradiation. When Ca F_2 is present,the reaction energy barrier is lowered and the leaching process is controlled by the tightly covered product layer,resulting in a prominent effect of microwave irradiation.展开更多
Herein, the influence of the concentration design and comprehensive performance of the sulfate-phosphoric mixed acid system electrolyte is investigated to realize an electrolyte that maintains high energy density and ...Herein, the influence of the concentration design and comprehensive performance of the sulfate-phosphoric mixed acid system electrolyte is investigated to realize an electrolyte that maintains high energy density and stable operation at high temperatures. Static stability tests have shown that VOPO4 precipitation occurs only with vanadium(V) electrolyte. The concentration of vanadium ion of 2.0–2.2 mol·L^(–1), phosphoric acid of 0.10–0.15 mol·L^(–1), and sulfuric acid of 2.5–3.0 mol·L^(–1) are suitable for a vanadium redox flow battery in the temperature range from –20 to 50 ℃. The equations for predicting the viscosity and conductivity of electrolytes are obtained by the response surface method. The optimized electrolyte overcomes precipitation generation. It has 2.8 times higher energy density than the non-phosphate electrolyte, and a coulomb efficiency of 94.0% at 50 ℃. The sulfate-phosphoric mixed acid system electrolyte promotes the electrode reaction process, increases the current density, and reduces the resistance. This work systematically optimizes the concentrations of composition of positive and negative vanadium electrolytes with mixed sulfate-phosphoric acid. It provides a basis for the different valence states and comprehensive properties of sulfate-phosphoric mixed acid system vanadium electrolytes under extreme environments, guiding engineering applications.展开更多
The vanadium redox flow battery with a safe and capacity-controllable large-scale energy storage system offers a new method for the sustainability.In this case,acetic acid,methane sulfonic acid,sulfonic acid,amino met...The vanadium redox flow battery with a safe and capacity-controllable large-scale energy storage system offers a new method for the sustainability.In this case,acetic acid,methane sulfonic acid,sulfonic acid,amino methane sulfonic acid,and taurine are used to overcome the low electrolyte energy density and stability limitations,as well as to investigate the effects of various organic functional groups on the vanadium redox flow battery.When compared to the pristine electrolyte(0.22 Ah,5.0 Wh·L^(−1),85.0%),the results show that taurine has the advantage of maintaining vanadium ion concentrations,discharge capacity(1.43 Ah),energy density(33.9 Wh·L^(−1)),and energy efficiency(90.5%)even after several cycles.The acetic acid electrolyte is more conducive to the low-temperature stability of the V(II)electrolyte(177 h at−25℃)than pristine(82 h at−2℃).The−SO_(3)H group,specifically the coaction of the−NH_(2)and−SO_(3)H groups,improves electrolyte stability.The−NH_(2)and−COOH additive groups improved conductivity and electrochemical activity.展开更多
Composite electrodes prepared by cation exchange resins and activated carbon(AC)were used to adsorb Ⅴ(Ⅳ)in capacitive deionization(CDI).The electrode made of middle resin size(D860/AC M)had the largest specific surf...Composite electrodes prepared by cation exchange resins and activated carbon(AC)were used to adsorb Ⅴ(Ⅳ)in capacitive deionization(CDI).The electrode made of middle resin size(D860/AC M)had the largest specific surface area and mesoporous content than two other composite electrodes.Electrochemical analysis showed that D860/AC M presents higher specific capacitance and electrical double layer capacitor than the others,and significantly lower internal diffusion impedance.Thus,D860/AC M exhibits the highest adsorption capacity and rate of Ⅴ(Ⅳ)among three electrodes.The intra-particle diffusion model fits well in the initial adsorption stage,while the liquid film diffusion model is more suitable for fitting at the later stage.The pseudo-second-order kinetic model is suited for the entire adsorption process.The adsorption of Ⅴ(Ⅳ)on the composite electrode follows that of the Freundlich isotherm.Thermodynamic analysis indicates that the adsorption of Ⅴ(Ⅳ)is an exothermic process with entropy reduction,and the electric field force plays a dominant role in the CDI process.This work aims to improve our understanding of the ion adsorption behaviors and mechanisms on the composite electrodes in CDI.展开更多
Separation of vanadium from black shale leaching solution at low pH is very meaningful,which can effectively avoid the generation of alkali neutralization slag and the resulting vanadium loss.In this study,coordinatio...Separation of vanadium from black shale leaching solution at low pH is very meaningful,which can effectively avoid the generation of alkali neutralization slag and the resulting vanadium loss.In this study,coordination mechanism of vanadium in acid leaching solution at low pH was investigated with the intervention of chloride ions.Under the conditions of pH 0.8,di-(2-ethylhexyl)phosphoric acid concentration of 20%,phase ratio of 1:2,and extraction time of 8 min,the vanadium extraction could reach 80.00%.The Fourier transform infrared and electrospray ionization results reveal that,despite the fact that the chloride ion in the leachate could significantly promote vanadium extraction,the chloride ion does not enter the organic phase,indicating an intriguing phenomenon.Among Cl^(-)-V,SO_(4)^(2-)-V,and H_(2)O-V,the V-Cl bond is longer and the potential difference between coordinate ions and vanadium is smaller.Therefore,Vo^(2+)gets easily desorbed with chloride ions and enter the organic phase.At the same time,the hydrogen ions of di-(2-ethylhexyl)phosphoric acid also enter the water phase more easily,which reduces the pH required for the extraction reaction.展开更多
基金financially supported by the Research Project from the Chinese Ministry of Education (No. 213025A)
文摘Experiments comparing microwave blank roasting and conventional blank roasting for typical vanadium-bearing stone coal from Hubei Province in central China, in which vanadium is present in muscovite, were conducted to investigate the effects of roasting temperature, roasting time, H2SO4 concentration, and leaching time on vanadium extraction. The results show that the vanadium leaching efficiency is 84% when the sample is roasted at 800°C for 30 min by microwave irradiation and the H2SO4 concentration, liquid/solid ratio, leaching temperature, and leaching time are set as 20vol%, 1.5:1 m L·g-1, 95°C, and 8 h, respectively. However, the vanadium leaching efficiency achieved for the sample subjected to conventional roasting at 900°C for 60 min is just 71% under the same leaching conditions. Scanning electron microscopy(SEM) analysis shows that the microwave roasted samples contain more cracks and that the particles are more porous compared to the conventionally roasted samples. According to the results of X-ray diffraction(XRD) and Fourier-transform infrared(FTIR) analyses, neither of these roasting methods could completely destroy the mica lattice structure under the experimental conditions; however, both methods deformed the muscovite structure and facilitated the leaching process. Comparing with conventional roasting, microwave roasting causes a greater deformation of the mineral structure at a lower temperature for a shorter roasting time.
基金financially supported by the National Natural Science Foundation of China(Nos.51474162 and 51404174)the Research Project of the Ministry of Education of China(No.213025A)
文摘The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation and calcium fluoride(Ca F_2) on the vanadium leaching efficiency. It is confirmed that the vanadium leaching process can be improved by microwave irradiation when Ca F_2 is present. The leaching rate of vanadium under microwave irradiation is increased by 8%–15% when 5wt% Ca F_2 is added; by contrast,in the absence of Ca F_2,the leaching rate is almost unaffected compared to that by conventional heating. Morphological analysis reveals that the particles are gradually eroded by acid under microwave irradiation,whereas some of the fine particles in samples subjected to conventional heating are tightly covered by a flocculent silicate product. Moreover,a large amount of Al and V and a small amount of Si are dissolved from samples under microwave heating,as revealed by the elemental analysis of leachates. Fourier transform infrared spectroscopic analysis also indicates a higher mass transfer coefficient in the diffusion layer of the raw material by microwave irradiation. When Ca F_2 is present,the reaction energy barrier is lowered and the leaching process is controlled by the tightly covered product layer,resulting in a prominent effect of microwave irradiation.
基金supported by the National Natural Science Foundation of China(Grant No.51774216)Hubei Technical Innovation Special Project of China(Grant No.2017ACA185)Science and technology innovation Talent program of Hubei Province(Grant No.2022EJD002).
文摘Herein, the influence of the concentration design and comprehensive performance of the sulfate-phosphoric mixed acid system electrolyte is investigated to realize an electrolyte that maintains high energy density and stable operation at high temperatures. Static stability tests have shown that VOPO4 precipitation occurs only with vanadium(V) electrolyte. The concentration of vanadium ion of 2.0–2.2 mol·L^(–1), phosphoric acid of 0.10–0.15 mol·L^(–1), and sulfuric acid of 2.5–3.0 mol·L^(–1) are suitable for a vanadium redox flow battery in the temperature range from –20 to 50 ℃. The equations for predicting the viscosity and conductivity of electrolytes are obtained by the response surface method. The optimized electrolyte overcomes precipitation generation. It has 2.8 times higher energy density than the non-phosphate electrolyte, and a coulomb efficiency of 94.0% at 50 ℃. The sulfate-phosphoric mixed acid system electrolyte promotes the electrode reaction process, increases the current density, and reduces the resistance. This work systematically optimizes the concentrations of composition of positive and negative vanadium electrolytes with mixed sulfate-phosphoric acid. It provides a basis for the different valence states and comprehensive properties of sulfate-phosphoric mixed acid system vanadium electrolytes under extreme environments, guiding engineering applications.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51774216)Hubei Technical Innovation Special Project of China(Grant No.2017ACA185)Outstanding Young and Middle-aged Science and Technology Innovation Team Project of Hubei Province(Grant No.T201802).
文摘The vanadium redox flow battery with a safe and capacity-controllable large-scale energy storage system offers a new method for the sustainability.In this case,acetic acid,methane sulfonic acid,sulfonic acid,amino methane sulfonic acid,and taurine are used to overcome the low electrolyte energy density and stability limitations,as well as to investigate the effects of various organic functional groups on the vanadium redox flow battery.When compared to the pristine electrolyte(0.22 Ah,5.0 Wh·L^(−1),85.0%),the results show that taurine has the advantage of maintaining vanadium ion concentrations,discharge capacity(1.43 Ah),energy density(33.9 Wh·L^(−1)),and energy efficiency(90.5%)even after several cycles.The acetic acid electrolyte is more conducive to the low-temperature stability of the V(II)electrolyte(177 h at−25℃)than pristine(82 h at−2℃).The−SO_(3)H group,specifically the coaction of the−NH_(2)and−SO_(3)H groups,improves electrolyte stability.The−NH_(2)and−COOH additive groups improved conductivity and electrochemical activity.
基金financially supported by the National Natural Science Foundation of China(No.51874222).
文摘Composite electrodes prepared by cation exchange resins and activated carbon(AC)were used to adsorb Ⅴ(Ⅳ)in capacitive deionization(CDI).The electrode made of middle resin size(D860/AC M)had the largest specific surface area and mesoporous content than two other composite electrodes.Electrochemical analysis showed that D860/AC M presents higher specific capacitance and electrical double layer capacitor than the others,and significantly lower internal diffusion impedance.Thus,D860/AC M exhibits the highest adsorption capacity and rate of Ⅴ(Ⅳ)among three electrodes.The intra-particle diffusion model fits well in the initial adsorption stage,while the liquid film diffusion model is more suitable for fitting at the later stage.The pseudo-second-order kinetic model is suited for the entire adsorption process.The adsorption of Ⅴ(Ⅳ)on the composite electrode follows that of the Freundlich isotherm.Thermodynamic analysis indicates that the adsorption of Ⅴ(Ⅳ)is an exothermic process with entropy reduction,and the electric field force plays a dominant role in the CDI process.This work aims to improve our understanding of the ion adsorption behaviors and mechanisms on the composite electrodes in CDI.
基金supported by the National Key R&D Program of China(Grant No.2020YFC1909700)the Project of National Natural Science Foundation of China(Grant Nos.51974207 and 51774215).
文摘Separation of vanadium from black shale leaching solution at low pH is very meaningful,which can effectively avoid the generation of alkali neutralization slag and the resulting vanadium loss.In this study,coordination mechanism of vanadium in acid leaching solution at low pH was investigated with the intervention of chloride ions.Under the conditions of pH 0.8,di-(2-ethylhexyl)phosphoric acid concentration of 20%,phase ratio of 1:2,and extraction time of 8 min,the vanadium extraction could reach 80.00%.The Fourier transform infrared and electrospray ionization results reveal that,despite the fact that the chloride ion in the leachate could significantly promote vanadium extraction,the chloride ion does not enter the organic phase,indicating an intriguing phenomenon.Among Cl^(-)-V,SO_(4)^(2-)-V,and H_(2)O-V,the V-Cl bond is longer and the potential difference between coordinate ions and vanadium is smaller.Therefore,Vo^(2+)gets easily desorbed with chloride ions and enter the organic phase.At the same time,the hydrogen ions of di-(2-ethylhexyl)phosphoric acid also enter the water phase more easily,which reduces the pH required for the extraction reaction.
