The optimized leaching techniques were studied by technical experiment and neural network optimization for improving indium leaching rate. Firstly, effect of single technical parameter on leaching rate was investigate...The optimized leaching techniques were studied by technical experiment and neural network optimization for improving indium leaching rate. Firstly, effect of single technical parameter on leaching rate was investigated experimentally with other parameters fixed as constants. The results show that increasing residual acidity can improve leaching rate of indium. Increasing the oxidant content can obviously increase leaching rate but the further addition of oxidant could not improve the leaching rate. The enhancement of temperature can improve the leaching rate while the further enhancement of temperature decreases it. Extension leaching time can improve the leaching rate. On this basis, a BPNN model was established to study the effects of multi-parameters on leaching rate. The results show that the relative error is extremely small, thus the BPNN model has a high prediction precision. At last, optimized technical parameters which can yield high leaching rate of 99.5%were obtained by experimental and BPNN studies：residual acidity 50-60 g/L, oxidant addition content 10%, leaching temperature 70 ℃ and leaching time 2 h.展开更多
Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process...Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process.In this study,the leaching kinetics of REEs from PG in nitric acid at different temperatures were explored in depth.The experiments show that the maximum leaching recovery for ΣREE was 58.5%,75.9%and 83.4%at 30,60 and 80℃,respectively.Additionally,among La,Ce,Y and Nd,Y had the highest leaching rate.A new shrinking core model(SCM)based on the dissolution reaction of a cylindrical solid particle with interfacial transfer and diffusion across the product layer as the rate-controlling step was deduced and could well fit the leaching process of REEs from PG.The activation energies for the leaching of La,Ce,Y and Nd were determined on the basis of the new cylindrical SCM.In summary,the cylindrical SCM was a more suitable fitting model than the spherical SCM,and the interfacial transfer and diffusion across the product layer were the rate-controlling step for REE leaching from the PG sample.展开更多
A batch of column experiments was carried out to investigate the change of Cr（Ⅵ） concentration leached out from chromium-containing slag with HCI as leaching agent, and to study influences of pH, ratio of solid mas...A batch of column experiments was carried out to investigate the change of Cr（Ⅵ） concentration leached out from chromium-containing slag with HCI as leaching agent, and to study influences of pH, ratio of solid mass to solution volume, flow velocity and temperature on Cr（Ⅵ） leaching. The optimal parameters were obtained for Cr（Ⅵ） leaching and a fitting model was established to describe the procedure of Cr（Ⅵ） leaching. The results show that Cr（Ⅵ） concentration in leachate increases with decreasing pH and increasing flow velocity and temperature. Moreover, Cr（Ⅵ） leaching percentage increases with increasing ratio of solid mass to solution volume. The optimal parameters for Cr（Ⅵ） selective leaching are as follows： pH=3.0, 1：5 of ratio of solid mass to solution volume, 180 mL/min of flow velocity and 40 ℃ of temperature. The procedure of Cr（Ⅵ） leaching fits well with the model： v= 1.87t^-0.54, indicating that the leaching rate of Cr（Ⅵ） declines in an exponential order of-0.54.展开更多
The direct leaching kinetics of an iron-poor zinc sulfide concentrate in the tubular reactor was examined.All tests werecarried out in the pilot plant.To allow the execution of hydrostatic pressure condition,the slurr...The direct leaching kinetics of an iron-poor zinc sulfide concentrate in the tubular reactor was examined.All tests werecarried out in the pilot plant.To allow the execution of hydrostatic pressure condition,the slurry with ferrous sulfate and sulfuric acidsolution was filled into a vertical tube(9m in height)and air was blown from the bottom of the reactor.The effects of initial acidconcentration,temperature,particle size,initial zinc sulfate concentration,pulp density and the concentration of Fe on the leachingkinetics were investigated.Results of the kinetic analysis indicate that direct leaching of zinc sulfide concentrate follows shrinkingcore model(SCM).This process was controlled by a chemical reaction with the apparent activation energy of49.7kJ/mol.Furthermore,a semi-empirical equation is obtained,showing that the order of the iron,sulfuric acid and zinc sulfate concentrationsand particle radius are0.982,0.189,-0.097and-0.992,respectively.Analysis of the unreacted and reacted sulfide particles bySEM-EDS shows that insensitive agitation in the reactor causes detachment of the sulfur layer from the particles surface in lowerthan60%Zn conversion and lixiviant in the face with sphalerite particles.展开更多
A mathematical model for enargite bioleaching at 70℃ by Sulfolobus BC in shake-flasks has been constructed. The model included （1） the indirect leaching by Fe^3＋ and Fe^3＋ regeneration by suspended Sulfolobus, a...A mathematical model for enargite bioleaching at 70℃ by Sulfolobus BC in shake-flasks has been constructed. The model included （1） the indirect leaching by Fe^3＋ and Fe^3＋ regeneration by suspended Sulfolobus, and （2） the direct leaching by the attached Sulfolobus. The model parameters were optimized using genetic algorithm （GA）. Simulations of the ferric leaching, and bioleaching processes were done using this model. The dynamic changes of the concentrations of Cu^2＋, As^3＋, As^5＋, Fe^3＋ and/or Fe^2＋, as well as ferric-arsenate precipitation were accurately predicted.展开更多
The leaching of rare earth elements （REEs） including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, soli...The leaching of rare earth elements （REEs） including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, solid to liquid ratio and leaching time on the recoveries of Ce, La and Nd were investigated using response surface methodology. The results showed that the acid concentration and solid to liquid ratio have significant effect on the leaching recoveries while the time has a little effect. The maximum REE leaching recoveries of 66.1%, 56.8% and 51.7% for Ce, La and Nd, respectively were achieved at the optimum leaching condition with 18% nitric acid concentration, 0.06 solid to liquid ratio and 38 min leaching time. The kinetics of cerium leaching was investigated using shrinking core model. It was observed that the leaching is composed of two stages. In the first stage a sharp increase in cerium leaching recovery was observed and at the longer time the leaching became slower. It was found that in the first stage the diffusion of reactants from ash layer is the rate controlling mechanism with an apparent activation energy of 6.54 kJ/mol, while in the second stage the mass transfer in the solution is the controlling mechanism.展开更多
In order to strengthen the leaching procedure,the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics,hydrodynami...In order to strengthen the leaching procedure,the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics,hydrodynamic and mass transfer.The results show that the leaching hydrodynamics follows the Darcy law.The leaching kinetics can be described by the shrinking core model;the leaching process is controlled by diffusion of porous solid layer;and the mass transfer can be described with Van Deemter equation.This provides a theoretic basis and a scientific approach with high efficiency and optimized extraction conditions in industrial practice.展开更多
The leaching kinetics of Sb and Fe from antimony-bearing complex sulfides ore was investigated in HCl solution by oxidation?leaching with ozone.The effects of temperature,HCl concentration,stirring speed and particle ...The leaching kinetics of Sb and Fe from antimony-bearing complex sulfides ore was investigated in HCl solution by oxidation?leaching with ozone.The effects of temperature,HCl concentration,stirring speed and particle size on the process were explored.It is found that the recoveries of Sb and Fe reach86.1%and28.8%,respectively,when the reaction conditions are4.0mol/L HCl,900r/min stirring speed at85°C with<0.074mm particle size after50min leaching.XRD analysis indicates that no new solid product forms in the leaching residue and the leaching process can be described by shrinking core model.The leaching of Sb corresponds to diffusion-controlled model at low temperature(15?45°C)and mixed-controlled model at high temperature(45?85°C),and the apparent activation energies are6.91and17.93kJ/mol,respectively.The leaching of Fe corresponds to diffusion-controlled model,and the apparent activation energy is1.99kJ/mol.Three semi-empirical rate equations are obtained to describe the leaching process.展开更多
The kinetic behavior of leaching copper from low grade copper oxide ore was investigated. The effects of leaching temperature, H2SO4 concentration, particle size of crude ore and agitation rate on the leaching efficie...The kinetic behavior of leaching copper from low grade copper oxide ore was investigated. The effects of leaching temperature, H2SO4 concentration, particle size of crude ore and agitation rate on the leaching efficiency of copper were also evaluated. And the kinetic equations of the leaching process were obtained. The results show that the leaching process can be described with a reaction model of shrinking core. The reaction can be divided into three stages. The first stage is the dissolution of free copper oxide and copper oxide wrapped by hematite-limonite ore. At this stage, the leaching efficiency is very fast （leaching efficiency is larger than 60%）. The second stage is the leaching of diffiuent copper oxides, whose apparent activation energy is 43.26 kJ/mol. During this process, the chemical reaction is the control step, and the reaction order of H2SO4 is 0.433 84. The third stage is the leaching of copper oxide wrapped by hematite-limonite and silicate ore with apparent activation energy of 16.08 kJ/mol, which belongs to the mixed control.展开更多
In order to decrease the evaporating rate of ammonia and increase the solubility of copper in the solution,ethylenediamine was added into the ammonia-ammonium chloride system to leach the copper-containing oxide ores....In order to decrease the evaporating rate of ammonia and increase the solubility of copper in the solution,ethylenediamine was added into the ammonia-ammonium chloride system to leach the copper-containing oxide ores.The thermodynamic model was constructed and the solubility of malachite Cu2(OH)2CO3 in the ammonia-ammonium chloride-ethylenediamine(En)-water system was calculated using the exponential computation method based on both mass balance and charge balance.It is found that the solubility of copper can be increased and the free ammonia concentration can be decreased by submitting partial ammonia with ethylenediamine.The lower free ammonia concentration in the solution is a guarantee to the lower evaporating rate of ammonia.The conditions of malachite Cu2(OH)2CO3 converting to atacamite Cu(OH)1.5Cl0.5 were also studied.A group of experiments were designed to validate the veracity of the results of the thermodynamic calculation.It is found that the thermodynamic model is reliable and it can guide the leaching process.展开更多
A kinetic study on the sulfuric acid leaching of multi-metal oxide, which is the product of multi-metal copper alloy with iron trioxide roasted in oxygen, was carried out. The effects of leaching time, stirring speed,...A kinetic study on the sulfuric acid leaching of multi-metal oxide, which is the product of multi-metal copper alloy with iron trioxide roasted in oxygen, was carried out. The effects of leaching time, stirring speed, sulfuric acid concentration, reaction temperature, and particle size of the multi-metal oxide on the kinetics and mechanism of copper extraction were studied. It was found that the reaction kinetic model about the copper extraction from multi-metal oxide follows the mixed kinetic shrinking core mode： 1/31n（1-X）＋（1-X）-l/3-1=680.5C（H2SO4）0.4297dp0.75115exp（-Ea/RT）t.展开更多
基金Project(2012BAE06B01)supported by the National Key Technologies R&D Program of China
文摘The optimized leaching techniques were studied by technical experiment and neural network optimization for improving indium leaching rate. Firstly, effect of single technical parameter on leaching rate was investigated experimentally with other parameters fixed as constants. The results show that increasing residual acidity can improve leaching rate of indium. Increasing the oxidant content can obviously increase leaching rate but the further addition of oxidant could not improve the leaching rate. The enhancement of temperature can improve the leaching rate while the further enhancement of temperature decreases it. Extension leaching time can improve the leaching rate. On this basis, a BPNN model was established to study the effects of multi-parameters on leaching rate. The results show that the relative error is extremely small, thus the BPNN model has a high prediction precision. At last, optimized technical parameters which can yield high leaching rate of 99.5%were obtained by experimental and BPNN studies：residual acidity 50-60 g/L, oxidant addition content 10%, leaching temperature 70 ℃ and leaching time 2 h.
基金Project(51904104) supported by the National Natural Science Foundation of ChinaProject(2020JJ5174) supported by the Natural Science Foundation of Hunan Province,China+2 种基金Project(2019M662780) supported by China Postdoctoral Science FoundationProject(19C0746) supported by Scientific Research Fund of Hunan Provincial Education Department,ChinaProject(2021-2843) supported by College Student Innovation and Entrepreneurship Training Program of Hunan Province,China。
文摘Phosphogypsum(PG)is a potential resource for rare earth elements(REEs).Several studies have been carried out on REE leaching from PG.However,few in-depth studies have investigated the kinetics of this leaching process.In this study,the leaching kinetics of REEs from PG in nitric acid at different temperatures were explored in depth.The experiments show that the maximum leaching recovery for ΣREE was 58.5%,75.9%and 83.4%at 30,60 and 80℃,respectively.Additionally,among La,Ce,Y and Nd,Y had the highest leaching rate.A new shrinking core model(SCM)based on the dissolution reaction of a cylindrical solid particle with interfacial transfer and diffusion across the product layer as the rate-controlling step was deduced and could well fit the leaching process of REEs from PG.The activation energies for the leaching of La,Ce,Y and Nd were determined on the basis of the new cylindrical SCM.In summary,the cylindrical SCM was a more suitable fitting model than the spherical SCM,and the interfacial transfer and diffusion across the product layer were the rate-controlling step for REE leaching from the PG sample.
基金Projects(2006AA06Z374 2007AA021304) supported by the National High-Tech Research and Development Program of China
文摘A batch of column experiments was carried out to investigate the change of Cr（Ⅵ） concentration leached out from chromium-containing slag with HCI as leaching agent, and to study influences of pH, ratio of solid mass to solution volume, flow velocity and temperature on Cr（Ⅵ） leaching. The optimal parameters were obtained for Cr（Ⅵ） leaching and a fitting model was established to describe the procedure of Cr（Ⅵ） leaching. The results show that Cr（Ⅵ） concentration in leachate increases with decreasing pH and increasing flow velocity and temperature. Moreover, Cr（Ⅵ） leaching percentage increases with increasing ratio of solid mass to solution volume. The optimal parameters for Cr（Ⅵ） selective leaching are as follows： pH=3.0, 1：5 of ratio of solid mass to solution volume, 180 mL/min of flow velocity and 40 ℃ of temperature. The procedure of Cr（Ⅵ） leaching fits well with the model： v= 1.87t^-0.54, indicating that the leaching rate of Cr（Ⅵ） declines in an exponential order of-0.54.
基金the Zanjan Zinc Khalessazan Industries Company (ZZKICO) for the financial and technical support of this work
文摘The direct leaching kinetics of an iron-poor zinc sulfide concentrate in the tubular reactor was examined.All tests werecarried out in the pilot plant.To allow the execution of hydrostatic pressure condition,the slurry with ferrous sulfate and sulfuric acidsolution was filled into a vertical tube(9m in height)and air was blown from the bottom of the reactor.The effects of initial acidconcentration,temperature,particle size,initial zinc sulfate concentration,pulp density and the concentration of Fe on the leachingkinetics were investigated.Results of the kinetic analysis indicate that direct leaching of zinc sulfide concentrate follows shrinkingcore model(SCM).This process was controlled by a chemical reaction with the apparent activation energy of49.7kJ/mol.Furthermore,a semi-empirical equation is obtained,showing that the order of the iron,sulfuric acid and zinc sulfate concentrationsand particle radius are0.982,0.189,-0.097and-0.992,respectively.Analysis of the unreacted and reacted sulfide particles bySEM-EDS shows that insensitive agitation in the reactor causes detachment of the sulfur layer from the particles surface in lowerthan60%Zn conversion and lixiviant in the face with sphalerite particles.
基金Supported by the State Key Development Program for Basic Research of China （2004CB619202） and the National Natural Science Foundation of China （50174034, 30170026）.
文摘A mathematical model for enargite bioleaching at 70℃ by Sulfolobus BC in shake-flasks has been constructed. The model included （1） the indirect leaching by Fe^3＋ and Fe^3＋ regeneration by suspended Sulfolobus, and （2） the direct leaching by the attached Sulfolobus. The model parameters were optimized using genetic algorithm （GA）. Simulations of the ferric leaching, and bioleaching processes were done using this model. The dynamic changes of the concentrations of Cu^2＋, As^3＋, As^5＋, Fe^3＋ and/or Fe^2＋, as well as ferric-arsenate precipitation were accurately predicted.
文摘The leaching of rare earth elements （REEs） including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, solid to liquid ratio and leaching time on the recoveries of Ce, La and Nd were investigated using response surface methodology. The results showed that the acid concentration and solid to liquid ratio have significant effect on the leaching recoveries while the time has a little effect. The maximum REE leaching recoveries of 66.1%, 56.8% and 51.7% for Ce, La and Nd, respectively were achieved at the optimum leaching condition with 18% nitric acid concentration, 0.06 solid to liquid ratio and 38 min leaching time. The kinetics of cerium leaching was investigated using shrinking core model. It was observed that the leaching is composed of two stages. In the first stage a sharp increase in cerium leaching recovery was observed and at the longer time the leaching became slower. It was found that in the first stage the diffusion of reactants from ash layer is the rate controlling mechanism with an apparent activation energy of 6.54 kJ/mol, while in the second stage the mass transfer in the solution is the controlling mechanism.
基金Projects(50664004,50474022,50574069) supported by the National Natural Science Foundation of ChinaProjects(Q959612,Q972026) supported by the Natural Science Foundation of Jiangxi Province,China
文摘In order to strengthen the leaching procedure,the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics,hydrodynamic and mass transfer.The results show that the leaching hydrodynamics follows the Darcy law.The leaching kinetics can be described by the shrinking core model;the leaching process is controlled by diffusion of porous solid layer;and the mass transfer can be described with Van Deemter equation.This provides a theoretic basis and a scientific approach with high efficiency and optimized extraction conditions in industrial practice.
基金Project (51474257) supported by the National Natural Science Foundation of ChinaProject (2015zzts037) supported by the Postgraduate Research and Innovation Projects of Hunan Province,ChinaProject (2015JC3005) supported by the Key Technology Research and Development Program of Hunan Province,China
文摘The leaching kinetics of Sb and Fe from antimony-bearing complex sulfides ore was investigated in HCl solution by oxidation?leaching with ozone.The effects of temperature,HCl concentration,stirring speed and particle size on the process were explored.It is found that the recoveries of Sb and Fe reach86.1%and28.8%,respectively,when the reaction conditions are4.0mol/L HCl,900r/min stirring speed at85°C with<0.074mm particle size after50min leaching.XRD analysis indicates that no new solid product forms in the leaching residue and the leaching process can be described by shrinking core model.The leaching of Sb corresponds to diffusion-controlled model at low temperature(15?45°C)and mixed-controlled model at high temperature(45?85°C),and the apparent activation energies are6.91and17.93kJ/mol,respectively.The leaching of Fe corresponds to diffusion-controlled model,and the apparent activation energy is1.99kJ/mol.Three semi-empirical rate equations are obtained to describe the leaching process.
基金Project(2005BA639C) supported by the National Science and Technology Development of China
文摘The kinetic behavior of leaching copper from low grade copper oxide ore was investigated. The effects of leaching temperature, H2SO4 concentration, particle size of crude ore and agitation rate on the leaching efficiency of copper were also evaluated. And the kinetic equations of the leaching process were obtained. The results show that the leaching process can be described with a reaction model of shrinking core. The reaction can be divided into three stages. The first stage is the dissolution of free copper oxide and copper oxide wrapped by hematite-limonite ore. At this stage, the leaching efficiency is very fast （leaching efficiency is larger than 60%）. The second stage is the leaching of diffiuent copper oxides, whose apparent activation energy is 43.26 kJ/mol. During this process, the chemical reaction is the control step, and the reaction order of H2SO4 is 0.433 84. The third stage is the leaching of copper oxide wrapped by hematite-limonite and silicate ore with apparent activation energy of 16.08 kJ/mol, which belongs to the mixed control.
基金Project(2007CB613604)supported by the National Basic Research Program of ChinaProject(50674104)supported by the National Natural Science Foundation of China
文摘In order to decrease the evaporating rate of ammonia and increase the solubility of copper in the solution,ethylenediamine was added into the ammonia-ammonium chloride system to leach the copper-containing oxide ores.The thermodynamic model was constructed and the solubility of malachite Cu2(OH)2CO3 in the ammonia-ammonium chloride-ethylenediamine(En)-water system was calculated using the exponential computation method based on both mass balance and charge balance.It is found that the solubility of copper can be increased and the free ammonia concentration can be decreased by submitting partial ammonia with ethylenediamine.The lower free ammonia concentration in the solution is a guarantee to the lower evaporating rate of ammonia.The conditions of malachite Cu2(OH)2CO3 converting to atacamite Cu(OH)1.5Cl0.5 were also studied.A group of experiments were designed to validate the veracity of the results of the thermodynamic calculation.It is found that the thermodynamic model is reliable and it can guide the leaching process.
基金Project(2011AA061003)supported by Hi-Tech Research and Development Program of China
文摘A kinetic study on the sulfuric acid leaching of multi-metal oxide, which is the product of multi-metal copper alloy with iron trioxide roasted in oxygen, was carried out. The effects of leaching time, stirring speed, sulfuric acid concentration, reaction temperature, and particle size of the multi-metal oxide on the kinetics and mechanism of copper extraction were studied. It was found that the reaction kinetic model about the copper extraction from multi-metal oxide follows the mixed kinetic shrinking core mode： 1/31n（1-X）＋（1-X）-l/3-1=680.5C（H2SO4）0.4297dp0.75115exp（-Ea/RT）t.
