The effects of Ca-based additives on roasting properties of low-grade molybdenum concentrate were studied. The resultsshow that calcium-based additives can react with molybdenum concentrate to form CaSO4 and CaMoO4. T...The effects of Ca-based additives on roasting properties of low-grade molybdenum concentrate were studied. The resultsshow that calcium-based additives can react with molybdenum concentrate to form CaSO4 and CaMoO4. The initial oxidationtemperature of MoS2 is 450℃, while the formation of CaMoO4 and CaSO4 occurs above 500℃. The whole calcification reactionsare nearly completed between 600 and 650℃. However, raising the temperature further helps for the formation of CaMoO4 but isdisadvantageous to sulfur fixing rate and molybdenum retention rate. Calcification efficiency of Ca-based additives follows theorder： Ca（OH）2〉CaO〉CaCO3. With increasing the dosage of Ca（OH）2, the molybdenum retention rate and sulfur-fixing rate rise, butexcessive dosages would consume more acid during leaching process. The appropriate mass ratio of Ca（OH）2 to molybdenumconcentrate is 1：1. When roasted at 650 ℃ for 90 min, the molybdenum retention rate and the sulfur-fixing rate of low-grademolybdenum concentrate reach 100% and 92.92%, respectively, and the dissolution rate of molybdenum achieves 99.12% withcalcines being leached by sulphuric acid.展开更多
In order to investigate the oxidation roasting of molybdenite concentrate in pure oxygen atmosphere, experiments at 673, 723, 773, 873 and 973 K were carried out. The phase transitions and morphology evolutions of the...In order to investigate the oxidation roasting of molybdenite concentrate in pure oxygen atmosphere, experiments at 673, 723, 773, 873 and 973 K were carried out. The phase transitions and morphology evolutions of the samples obtained at different temperatures after reacting for different time were analyzed by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The results showed that molybdenite concentrate was oxidized directly to Mo O3 in pure oxygen atmosphere. There were remarkable changes of the morphologies of products with the increase of the roasting temperature. It was also found that sintering phenomenon occurred during the roasting process in pure oxygen when the temperature was above 873 K. The composition of sintered sample was mainly comprised of Mo O3 and some unreacted Mo S2.展开更多
To extract molybdenum and nickel from the roasted Ni-Mo ore, a process of hydrochloric acid leaching, sulphation roasting and water leaching was investigated. The results showed that this process could get a high leac...To extract molybdenum and nickel from the roasted Ni-Mo ore, a process of hydrochloric acid leaching, sulphation roasting and water leaching was investigated. The results showed that this process could get a high leaching rate of Mo and Ni. Under the optimum conditions of hydrochloric acid leaching （roasted Ni-Mo ore leached with 0.219 mL/g hydrochloric acid addition at 65 ℃ for 30 min with a L/S ratio of 3 mL/g）, sulphation roasting （51.9% sulfiaric acid addition, roasting temperature 240 ℃ for 1 h）, followed by leaching with the first stage hydrochloric acid leaching solution at 95 ℃ for 2 h, the leaching rates of Mo and Ni reached 95.8% and 91.3%, respectively.展开更多
This work focuses on the organic depressant,disodium bis(carboxymethyl)trithiocarbonate(DBT),as a selectivedepressant in copper?molybdenum sulfide flotation separation.Micro-flotation,Zeta potential,FTIR and XPS measu...This work focuses on the organic depressant,disodium bis(carboxymethyl)trithiocarbonate(DBT),as a selectivedepressant in copper?molybdenum sulfide flotation separation.Micro-flotation,Zeta potential,FTIR and XPS measurements werecarried out to investigate the selective depression mechanism of DBT on chalcopyrite.Zeta potential and FTIR measurementsrevealed that DBT had higher affinity for chalcopyrite than molybdenite and the XPS results of chalcopyrite before and aftertreatment with DBT further proved that DBT adsorbed on chalcopyrite surface.The investigation indicates that the mechanism ofDBT adsorbing on chalcopyrite is mainly physical adsorption.Locked circuit experiments were carried out and the results showedthat DBT could be considered as a cleaner option in commercial Cu?Mo flotation separation circuits.展开更多
The kinetics of oxidation roasting of molybdenum concentrate was studied by differential thermal−gravimetric experiments and non-isothermal analysis methods.The results show that high temperature is beneficial for oxi...The kinetics of oxidation roasting of molybdenum concentrate was studied by differential thermal−gravimetric experiments and non-isothermal analysis methods.The results show that high temperature is beneficial for oxidation of molybdenum concentrate.The initial oxidation temperature of the molybdenum concentrate is 450℃,and the rapid oxidation occurs above 500℃.The oxidation process conforms to the unreacted shrinking nucleus model.The early stage of the oxidation is controlled by chemical reaction with the apparent activation energy of 123.180 kJ/mol,while the later stage is controlled by internal diffusion with the apparent activation energy of 80.175 kJ/mol.Moreover,the oxidation rate is closely related to particle size of the concentrate.The smaller the particle size is,the larger the oxidation rate is.展开更多
Roasting experiments were carried out with pure reagents as raw materials.The self-sintering behaviors of molybdenite(MoS_(2))during oxidation were investigated by thermodynamic calculation,XRD,SEM-EDS and high-temper...Roasting experiments were carried out with pure reagents as raw materials.The self-sintering behaviors of molybdenite(MoS_(2))during oxidation were investigated by thermodynamic calculation,XRD,SEM-EDS and high-temperature in situ analysis.The results indicate that the desulfurization efficiency of MoS_(2) pellet decreases with the increase of roasting temperature from 600 to 700℃,owing to the expansion of sintered area.At the very beginning of roasting,sintered layer can be rapidly formed and cover the pellet surface on the windward side,and meanwhile,MoO_(2)and Mo_(4)O_(11) intensively appear and constitute the sintered layer together with MoO_(3).Moreover,it is proven that MoO_(3)-rich products containing low-valence molybdenum oxides have low melting points,thus easy to be melted during the occurrence of exothermic reaction between MoS_(2) and O_(2),which leads to the sintering of materials.展开更多
The oxidation roasting process of molybdenum concentrate has significant advantages in industrial applications.However,utilization of low-grade mineral has many problems because it is more complex than the standard co...The oxidation roasting process of molybdenum concentrate has significant advantages in industrial applications.However,utilization of low-grade mineral has many problems because it is more complex than the standard concentrate.In this study,the oxidation behaviors of powdery rhenium-bearing low-grade molybdenum concentrate were investigated through thermodynamic calculation,roasting experiments,thermogravimetric analysis,and phase analysis.The results obtained show that oxidation of MoS2 begins at 450℃,and MoO3 reacts with metal-oxide forming molybdate at 600℃.Finally,MoO3 can be dissolved in ammonia with a maximum content of approximately 80%.The volatile speed of Re was considerably slower than the oxidation speed of MoS2 because the nonvolatile products ReO2 and ReO3 were generated in reactions among MoS2,SO2,and Re2O7.The final volatilization rate of Re was almost 70%.This study determined the problems related to the roasting of low-grade molybdenum concentrate,which lays the scientific foundations for subsequent enhancement of molybdenum and rhenium extraction.展开更多
The dissolution of molybdenite concentrate in NaC1 electrolyte was investigated. The results show that the dissolution rate increases with the increase in liquid-to-solid ratio, stirring speed, NaCl concentration and ...The dissolution of molybdenite concentrate in NaC1 electrolyte was investigated. The results show that the dissolution rate increases with the increase in liquid-to-solid ratio, stirring speed, NaCl concentration and temperature. When the liquid-to-solid ratio is 30：1, stirring speed is 400 r/min, concentration of NaCI is 4 mol/L at pH=9 and room temperature, the leaching efficiency of molybdenite concentrate will reach 99.5% in 240 min. Molybdenite concentrate cannot be electro-oxidized directly on the anode. The kinetic studies show that the dissolution of molybdenite concentrate is represented by shrinking core model with diffusion through a porous product layer of element sulfur, and the apparent activation energy for the dissolution reaction is 8.56 kJ/mol.展开更多
Oxidizing roasting of molybdenite with lime can significantly reduce SO2pollution compared with the traditional roastingwithout lime.However,the calcine is subsequently leached by sulfuric acid,resulting in serious eq...Oxidizing roasting of molybdenite with lime can significantly reduce SO2pollution compared with the traditional roastingwithout lime.However,the calcine is subsequently leached by sulfuric acid,resulting in serious equipment corrosion and abundantnon-recyclable CaSO4slag.In this work,a novel process,in which the molybdenite was roasted with CaCO3followed by(NH4)2CO3solution leaching,was proposed to improve the art of lime roasting-sulfuric acid leaching.Oxidizing roasting of molybdenite withCaCO3was investigated through thermodynamic calculation,thermogravimetric analysis and roasting experiments.The results showthat the products of the oxidizing reaction of MoS2in the presence of CaCO3and O2are CaSO4,CaMoO4and CO2at573-1000K.The MoS2conversion rate achieves approximately99%and the sulfur-retained rate attains approximately95%with aCaCO3-to-MoS2molar ratio of3.6at500°C for1h by adding5%mineralizer A(mass fraction).The leaching results show that theleaching rate of Mo reaches98.2%at85°C for7h with a(NH4)2CO3concentration of600g/L and a liquid-solid ratio of10mL/g.The results presented are potential to develop a novel cleaner technique for ammonium molybdate production.展开更多
The separation of rhenium from molybdenum in aqueous solution has always been a problem in hydrometallurgy. The separation of rhenium from the electro-oxidation leachate of molybdenite and its mechanism were investiga...The separation of rhenium from molybdenum in aqueous solution has always been a problem in hydrometallurgy. The separation of rhenium from the electro-oxidation leachate of molybdenite and its mechanism were investigated. The results show that pH of the leachate significantly affects adsorption rate compared with other experimental parameters. When temperature is 30℃, pH=8, and adsorbing time is 1 h, adsorption rates of rhenium and molybdenum are 93.46% and 3.57%, respectively, and separation factor of D301 resin for rhenium and molybdenum is 169.56. In addition, the separation factor is higher when the initial molybdenum concentration in model solution is increased. The saturated adsorption capacity of D301 resin for molybdenum and rhenium calculated based on simulated results are 4.263 3 mmol/g and 4.235 5 mmol/g, respectively. D301 resin is an effective separation material of rhenium from electric-oxidation leachate of molybdenite. The adsorption kinetics results also show that the adsorption of rhenium is easier than that of molybdenum, and the adsorption process of D301 for rhenium and molybdenum may be controlled by liquid film diffusion.展开更多
Sodium hypochlorite was used to treat the standard molybdenum concentrates; the oxidization conditions for sodium hypochlorite were investigated, and the electro-oxidation process was performed. The results indicate t...Sodium hypochlorite was used to treat the standard molybdenum concentrates; the oxidization conditions for sodium hypochlorite were investigated, and the electro-oxidation process was performed. The results indicate that in the suitable conditions, such as temperature around 25℃, NaCl concentration 4.0mol/L, mass ratio of ore slurry liquid to solid （mL/mS） 20, electric charge per gram Mo 0.522C, pH value of original slurry 8, anodic current density 700A·m-2 （cell potential 2.72.9V）, the Mo leaching rate and the current efficiency reach 98% and 36%, respectively. In order to overcome some shortages of the electro-oxidation process, such as low current efficiency, low Mo concentration in the leaching solution, ultrasonic was adopted to intensify the leaching process. The results show that the Mo leaching rate exceeds 98%, current efficiency increases from 36% to 50% and the Mo concentration in the leaching solution reaches about 60g/L at low mL/mS of 8 and low electric charge of 0.373C.展开更多
基金Project(51304245)supported by the National Natural Science Foundation of ChinaProject(2014T70691)supported by the Postdoctoral Science Foundation of China+1 种基金Project(2015CX005)supported by the Innovation Driven Plan of Central South University,ChinaProject supported by the Hunan Provincial Co-innovation Center for Clean and Efficient Utilization of Strategic Metal Mineral Resources,China
文摘The effects of Ca-based additives on roasting properties of low-grade molybdenum concentrate were studied. The resultsshow that calcium-based additives can react with molybdenum concentrate to form CaSO4 and CaMoO4. The initial oxidationtemperature of MoS2 is 450℃, while the formation of CaMoO4 and CaSO4 occurs above 500℃. The whole calcification reactionsare nearly completed between 600 and 650℃. However, raising the temperature further helps for the formation of CaMoO4 but isdisadvantageous to sulfur fixing rate and molybdenum retention rate. Calcification efficiency of Ca-based additives follows theorder： Ca（OH）2〉CaO〉CaCO3. With increasing the dosage of Ca（OH）2, the molybdenum retention rate and sulfur-fixing rate rise, butexcessive dosages would consume more acid during leaching process. The appropriate mass ratio of Ca（OH）2 to molybdenumconcentrate is 1：1. When roasted at 650 ℃ for 90 min, the molybdenum retention rate and the sulfur-fixing rate of low-grademolybdenum concentrate reach 100% and 92.92%, respectively, and the dissolution rate of molybdenum achieves 99.12% withcalcines being leached by sulphuric acid.
基金Projects(5147414151174022)supported by the National Natural Science Foundation of China
文摘In order to investigate the oxidation roasting of molybdenite concentrate in pure oxygen atmosphere, experiments at 673, 723, 773, 873 and 973 K were carried out. The phase transitions and morphology evolutions of the samples obtained at different temperatures after reacting for different time were analyzed by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The results showed that molybdenite concentrate was oxidized directly to Mo O3 in pure oxygen atmosphere. There were remarkable changes of the morphologies of products with the increase of the roasting temperature. It was also found that sintering phenomenon occurred during the roasting process in pure oxygen when the temperature was above 873 K. The composition of sintered sample was mainly comprised of Mo O3 and some unreacted Mo S2.
基金Project(51104186)supported by the National Natural Science Foundation of ChinaProjects(2016zzts282,2016zzts283)supported by the Fundamental Research Funds for the Central Universities of Central South University,China
文摘To extract molybdenum and nickel from the roasted Ni-Mo ore, a process of hydrochloric acid leaching, sulphation roasting and water leaching was investigated. The results showed that this process could get a high leaching rate of Mo and Ni. Under the optimum conditions of hydrochloric acid leaching （roasted Ni-Mo ore leached with 0.219 mL/g hydrochloric acid addition at 65 ℃ for 30 min with a L/S ratio of 3 mL/g）, sulphation roasting （51.9% sulfiaric acid addition, roasting temperature 240 ℃ for 1 h）, followed by leaching with the first stage hydrochloric acid leaching solution at 95 ℃ for 2 h, the leaching rates of Mo and Ni reached 95.8% and 91.3%, respectively.
基金Project(2016zzts109)supported by the Innovation Driven Plan of Central South University,ChinaProject(B14034)supported by the National 111 Project,China
文摘This work focuses on the organic depressant,disodium bis(carboxymethyl)trithiocarbonate(DBT),as a selectivedepressant in copper?molybdenum sulfide flotation separation.Micro-flotation,Zeta potential,FTIR and XPS measurements werecarried out to investigate the selective depression mechanism of DBT on chalcopyrite.Zeta potential and FTIR measurementsrevealed that DBT had higher affinity for chalcopyrite than molybdenite and the XPS results of chalcopyrite before and aftertreatment with DBT further proved that DBT adsorbed on chalcopyrite surface.The investigation indicates that the mechanism ofDBT adsorbing on chalcopyrite is mainly physical adsorption.Locked circuit experiments were carried out and the results showedthat DBT could be considered as a cleaner option in commercial Cu?Mo flotation separation circuits.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(52074364).
文摘The kinetics of oxidation roasting of molybdenum concentrate was studied by differential thermal−gravimetric experiments and non-isothermal analysis methods.The results show that high temperature is beneficial for oxidation of molybdenum concentrate.The initial oxidation temperature of the molybdenum concentrate is 450℃,and the rapid oxidation occurs above 500℃.The oxidation process conforms to the unreacted shrinking nucleus model.The early stage of the oxidation is controlled by chemical reaction with the apparent activation energy of 123.180 kJ/mol,while the later stage is controlled by internal diffusion with the apparent activation energy of 80.175 kJ/mol.Moreover,the oxidation rate is closely related to particle size of the concentrate.The smaller the particle size is,the larger the oxidation rate is.
基金financially supported by the Basic Science Center Program of the National Natural Science Foundation of China(No.72088101)the General Program of the National Natural Science Foundation of China(No.51874355)the Special Funding of China Postdoctoral Science Foundation(No.2020T130730)。
文摘Roasting experiments were carried out with pure reagents as raw materials.The self-sintering behaviors of molybdenite(MoS_(2))during oxidation were investigated by thermodynamic calculation,XRD,SEM-EDS and high-temperature in situ analysis.The results indicate that the desulfurization efficiency of MoS_(2) pellet decreases with the increase of roasting temperature from 600 to 700℃,owing to the expansion of sintered area.At the very beginning of roasting,sintered layer can be rapidly formed and cover the pellet surface on the windward side,and meanwhile,MoO_(2)and Mo_(4)O_(11) intensively appear and constitute the sintered layer together with MoO_(3).Moreover,it is proven that MoO_(3)-rich products containing low-valence molybdenum oxides have low melting points,thus easy to be melted during the occurrence of exothermic reaction between MoS_(2) and O_(2),which leads to the sintering of materials.
基金Projects(U1760107,U1660206)supported by the National Natural Science Foundation of ChinaProject(2013zzts064)supported by the Innovation Foundation for Postgraduate of Central South University,China
文摘The oxidation roasting process of molybdenum concentrate has significant advantages in industrial applications.However,utilization of low-grade mineral has many problems because it is more complex than the standard concentrate.In this study,the oxidation behaviors of powdery rhenium-bearing low-grade molybdenum concentrate were investigated through thermodynamic calculation,roasting experiments,thermogravimetric analysis,and phase analysis.The results obtained show that oxidation of MoS2 begins at 450℃,and MoO3 reacts with metal-oxide forming molybdate at 600℃.Finally,MoO3 can be dissolved in ammonia with a maximum content of approximately 80%.The volatile speed of Re was considerably slower than the oxidation speed of MoS2 because the nonvolatile products ReO2 and ReO3 were generated in reactions among MoS2,SO2,and Re2O7.The final volatilization rate of Re was almost 70%.This study determined the problems related to the roasting of low-grade molybdenum concentrate,which lays the scientific foundations for subsequent enhancement of molybdenum and rhenium extraction.
基金Project(2007BAB22B01) supported by the 11th Five-Year Plan of National Science and Technology of China Project(50704036) supported by the National Natural Science Foundation of China
文摘The dissolution of molybdenite concentrate in NaC1 electrolyte was investigated. The results show that the dissolution rate increases with the increase in liquid-to-solid ratio, stirring speed, NaCl concentration and temperature. When the liquid-to-solid ratio is 30：1, stirring speed is 400 r/min, concentration of NaCI is 4 mol/L at pH=9 and room temperature, the leaching efficiency of molybdenite concentrate will reach 99.5% in 240 min. Molybdenite concentrate cannot be electro-oxidized directly on the anode. The kinetic studies show that the dissolution of molybdenite concentrate is represented by shrinking core model with diffusion through a porous product layer of element sulfur, and the apparent activation energy for the dissolution reaction is 8.56 kJ/mol.
基金Project(51274243)supported by the National Natural Science Foundation of ChinaProject(2015CX001)supported by the Innovation-driven Plan in Central South University,China
文摘Oxidizing roasting of molybdenite with lime can significantly reduce SO2pollution compared with the traditional roastingwithout lime.However,the calcine is subsequently leached by sulfuric acid,resulting in serious equipment corrosion and abundantnon-recyclable CaSO4slag.In this work,a novel process,in which the molybdenite was roasted with CaCO3followed by(NH4)2CO3solution leaching,was proposed to improve the art of lime roasting-sulfuric acid leaching.Oxidizing roasting of molybdenite withCaCO3was investigated through thermodynamic calculation,thermogravimetric analysis and roasting experiments.The results showthat the products of the oxidizing reaction of MoS2in the presence of CaCO3and O2are CaSO4,CaMoO4and CO2at573-1000K.The MoS2conversion rate achieves approximately99%and the sulfur-retained rate attains approximately95%with aCaCO3-to-MoS2molar ratio of3.6at500°C for1h by adding5%mineralizer A(mass fraction).The leaching results show that theleaching rate of Mo reaches98.2%at85°C for7h with a(NH4)2CO3concentration of600g/L and a liquid-solid ratio of10mL/g.The results presented are potential to develop a novel cleaner technique for ammonium molybdate production.
基金Foundation item： Project（21106188） supported by the National Natural Science Foundation of China Project（12JJ4013） supported by Htman Provincial Natural Science Foundation of China+2 种基金 Projects（2011M501299, 2012T50709） supported by China Postdoctoral Science Foundation Project（2011QNZT050） supported by the Special Fund from the Central Collegiate Basic Scientific Research Bursary of Central South University, China Project（CSUZC2012038） supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University, China
文摘The separation of rhenium from molybdenum in aqueous solution has always been a problem in hydrometallurgy. The separation of rhenium from the electro-oxidation leachate of molybdenite and its mechanism were investigated. The results show that pH of the leachate significantly affects adsorption rate compared with other experimental parameters. When temperature is 30℃, pH=8, and adsorbing time is 1 h, adsorption rates of rhenium and molybdenum are 93.46% and 3.57%, respectively, and separation factor of D301 resin for rhenium and molybdenum is 169.56. In addition, the separation factor is higher when the initial molybdenum concentration in model solution is increased. The saturated adsorption capacity of D301 resin for molybdenum and rhenium calculated based on simulated results are 4.263 3 mmol/g and 4.235 5 mmol/g, respectively. D301 resin is an effective separation material of rhenium from electric-oxidation leachate of molybdenite. The adsorption kinetics results also show that the adsorption of rhenium is easier than that of molybdenum, and the adsorption process of D301 for rhenium and molybdenum may be controlled by liquid film diffusion.
文摘Sodium hypochlorite was used to treat the standard molybdenum concentrates; the oxidization conditions for sodium hypochlorite were investigated, and the electro-oxidation process was performed. The results indicate that in the suitable conditions, such as temperature around 25℃, NaCl concentration 4.0mol/L, mass ratio of ore slurry liquid to solid （mL/mS） 20, electric charge per gram Mo 0.522C, pH value of original slurry 8, anodic current density 700A·m-2 （cell potential 2.72.9V）, the Mo leaching rate and the current efficiency reach 98% and 36%, respectively. In order to overcome some shortages of the electro-oxidation process, such as low current efficiency, low Mo concentration in the leaching solution, ultrasonic was adopted to intensify the leaching process. The results show that the Mo leaching rate exceeds 98%, current efficiency increases from 36% to 50% and the Mo concentration in the leaching solution reaches about 60g/L at low mL/mS of 8 and low electric charge of 0.373C.
