To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures rangi...To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.展开更多
Arsenic(As)removal from smelting acidic wastewater is an urgent task.The most common method is oxidation of trivalent As(III)to pentavalent As(V)subsequently precipitated by ferric(Fe(III))salts.Foundations of redox b...Arsenic(As)removal from smelting acidic wastewater is an urgent task.The most common method is oxidation of trivalent As(III)to pentavalent As(V)subsequently precipitated by ferric(Fe(III))salts.Foundations of redox behavior and chemical species are of great importance for understanding As removal.In this work,cyclic voltammetry(CV)and UV?Vis spectroscopy were used for laboratory observation;meanwhile HSC and MINTEQ software were employed for theoretical analyses.It is found that As(III)oxidation,a multiple electron transfer reaction,is diffusion-controlled.The oxidation over-potential is very high(about0.9V)in sulfuric acid solutions(pH1.0).In addition,Fe(III)?As(V)complexes are evidenced by UV?Vis spectra and chemical species analyses in series of Fe(III)?As(V)?H2SO4?H2O solutions.Therefore,the Fe(III)and As(V)species distribution against pH values are determined and a newφ?pH diagram with inclusion of Fe?As complexes is consequently compiled based on thermodynamic data predicted by other researchers.展开更多
The constructed potential-pH diagrams of Li-Ni(Co,Mn)-H2O system indicate that the LiNiO2,LiCoO2 and LiMnO2 are thermodynamically stable in aqueous solution within the temperature range of 25-200°C and the activi...The constructed potential-pH diagrams of Li-Ni(Co,Mn)-H2O system indicate that the LiNiO2,LiCoO2 and LiMnO2 are thermodynamically stable in aqueous solution within the temperature range of 25-200°C and the activity range of 0.01-1.00.A predominant co-region of LiNiO2,LiCoO2 and LiMnO2 oxides(Li-Ni-Co-Mncomposite oxide)is found in the Li-Ni-Co-Mn-H2O potential-pH diagrams,in which the co-precipitation region expands towards lower pH with rising temperature,indicating the enhanced possibility of synthesizing Li-Ni-Co-Mn composite oxide in aqueous solution.The experimental results prove that it is feasible to prepare the LiNi0.5Co0.2Mn0.3O2 cathode materials(NCM523)by an aqueous routine.The as-prepared lithiated precursor and NCM523 both inherit the spherical morphology of the hydroxide precursor and the obtained NCM523 has a hexagonalα-NaFeO2 structure with good crystallinity.It is reasonable to conclude that the aqueous routine for preparing NCM cathode materials is a promising method with the guidance of the reliable potential-pH diagrams to some extent.展开更多
基金Project(2007CB613504)supported by the National Key Basic Research Program of ChinaProjects(51004033,50974035,51074047)supported by the National Natural Science Foundation of ChinaProject(2008BAB34B01)supported by National Science and Technology Support Plan of China during the 11th Five-Year Plan
文摘To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.
基金Projects (51304251,51374237) supported by the National Natural Science Foundation of ChinaProject (201509050) supported by Special Program on Environmental Protection for Public Welfare,China
文摘Arsenic(As)removal from smelting acidic wastewater is an urgent task.The most common method is oxidation of trivalent As(III)to pentavalent As(V)subsequently precipitated by ferric(Fe(III))salts.Foundations of redox behavior and chemical species are of great importance for understanding As removal.In this work,cyclic voltammetry(CV)and UV?Vis spectroscopy were used for laboratory observation;meanwhile HSC and MINTEQ software were employed for theoretical analyses.It is found that As(III)oxidation,a multiple electron transfer reaction,is diffusion-controlled.The oxidation over-potential is very high(about0.9V)in sulfuric acid solutions(pH1.0).In addition,Fe(III)?As(V)complexes are evidenced by UV?Vis spectra and chemical species analyses in series of Fe(III)?As(V)?H2SO4?H2O solutions.Therefore,the Fe(III)and As(V)species distribution against pH values are determined and a newφ?pH diagram with inclusion of Fe?As complexes is consequently compiled based on thermodynamic data predicted by other researchers.
基金Project(FA2019015) supported by the Government of Chongzuo,Guangxi Zhuang Autonomous Region,ChinaProject(AD18281073) supported by Science and Technology Department of Guangxi Zhuang Autonomous Region,China
文摘The constructed potential-pH diagrams of Li-Ni(Co,Mn)-H2O system indicate that the LiNiO2,LiCoO2 and LiMnO2 are thermodynamically stable in aqueous solution within the temperature range of 25-200°C and the activity range of 0.01-1.00.A predominant co-region of LiNiO2,LiCoO2 and LiMnO2 oxides(Li-Ni-Co-Mncomposite oxide)is found in the Li-Ni-Co-Mn-H2O potential-pH diagrams,in which the co-precipitation region expands towards lower pH with rising temperature,indicating the enhanced possibility of synthesizing Li-Ni-Co-Mn composite oxide in aqueous solution.The experimental results prove that it is feasible to prepare the LiNi0.5Co0.2Mn0.3O2 cathode materials(NCM523)by an aqueous routine.The as-prepared lithiated precursor and NCM523 both inherit the spherical morphology of the hydroxide precursor and the obtained NCM523 has a hexagonalα-NaFeO2 structure with good crystallinity.It is reasonable to conclude that the aqueous routine for preparing NCM cathode materials is a promising method with the guidance of the reliable potential-pH diagrams to some extent.
