The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when...The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 moUL H2SO4 at 90℃ for 2 h. After the sample is roasted at 900℃ for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the Content of V(V) increases with the rise of roasting temperature from 600 to 900℃, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000℃. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.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
基金financially supported by the National Key Technologies R&D Program of China(Nos.2011BAB05B01 and 2011BAB05B04)the Exclusive Research Fund of Environmental Protection for the Commonweal of China(No.201009013)
文摘The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 moUL H2SO4 at 90℃ for 2 h. After the sample is roasted at 900℃ for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the Content of V(V) increases with the rise of roasting temperature from 600 to 900℃, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000℃. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.
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.