A plumbomicrolite concentrate(PMC)was leached with the mixture of HF and H2SO4,HF and HNO3 acids,respectively.Optimal conditions ensuring high recovery of tantalum and niobium(up to 99%)into solution,and radionuclides...A plumbomicrolite concentrate(PMC)was leached with the mixture of HF and H2SO4,HF and HNO3 acids,respectively.Optimal conditions ensuring high recovery of tantalum and niobium(up to 99%)into solution,and radionuclides into insoluble residue were determined.Fluoride-sulfuric acid and fluoride-nitric acid schemes were proposed for PMC leaching by an extractive separation of tantalum form niobium,lead and impurities,and production of high-purity tantalum compounds.Octanol-1 was used as an extractant.Optimal conditions for production of high-purity tantalum strip solutions were defined for all stages(extraction-scrubbing-stripping).Produced tantalum compounds,such as tantalum pentoxide and potassium heptafluotanthalate,comply with the norms for high-purity substances in terms of impurities content.Final choice of the PMC processing scheme is determined by its profitability.展开更多
The leaching kinetics of molybdenum from Ni-Mo ore in sulfuric acid solution with sodium peroxodisulfate was studied.The effects including leaching temperature, reaction time, particle size, stirring speed, and concen...The leaching kinetics of molybdenum from Ni-Mo ore in sulfuric acid solution with sodium peroxodisulfate was studied.The effects including leaching temperature, reaction time, particle size, stirring speed, and concentrations of sulfuric acid and sodium peroxodisulfate were investigated. The leaching process of molybdenum from Ni-Mo ore is controlled by the chemical reaction through the solid layer across the unreacted shrinking core. The apparent activation energy of the leaching of molybdenum is calculated to be 41.0 k J/mol and the leaching kinetics equation of molybdenum from Ni-Mo ore is expressed as1-(1-a)1/3=3405.7exp[-41030.0/(RT)]t.展开更多
This work aims to investigate the efficiency of Fariman sepiolite from Iran as an adsorbent to remove Cd from aqueous solutions. The effects of different experimental factors such as the initial Cd concentration, cont...This work aims to investigate the efficiency of Fariman sepiolite from Iran as an adsorbent to remove Cd from aqueous solutions. The effects of different experimental factors such as the initial Cd concentration, contact time and the sorbent dose were investigated through a series of batch adsorption experiments. The results show that the adsorption capacity of sepiolite for Cd increases with the contact time, the initial concentration of Cd solutions and the sorbent dose. Sorption of Cd by Fariman sepiolite is rapid within the first hour of the experiment and then slowly increases until a pseudo equilibrium is approached at 8 h. The results also show that the time-dependent Cd sorption data are better described with pseudo second-order （7〉0.999） than that of pseudo first-order （r2〉0.971） kinetic model. Equilibrium isotherm studies show that the experimental data are better correlated by the Freundlich adsorption isotherm （7〉0.995） than the Langmuir （P〉0.825）. It is suggested that both adsorption and cation exchange reactions are responsible for the sorption of Cd by the sepiolite, and the mineral has a very good potential to remove Cd from aqueous solutions.展开更多
基金Project supported by the Federal Research Centre of Kola Science Centre of the Russian Academy of Sciences,Russian。
文摘A plumbomicrolite concentrate(PMC)was leached with the mixture of HF and H2SO4,HF and HNO3 acids,respectively.Optimal conditions ensuring high recovery of tantalum and niobium(up to 99%)into solution,and radionuclides into insoluble residue were determined.Fluoride-sulfuric acid and fluoride-nitric acid schemes were proposed for PMC leaching by an extractive separation of tantalum form niobium,lead and impurities,and production of high-purity tantalum compounds.Octanol-1 was used as an extractant.Optimal conditions for production of high-purity tantalum strip solutions were defined for all stages(extraction-scrubbing-stripping).Produced tantalum compounds,such as tantalum pentoxide and potassium heptafluotanthalate,comply with the norms for high-purity substances in terms of impurities content.Final choice of the PMC processing scheme is determined by its profitability.
基金Project(51364009) supported by the National Natural Science Foundation of ChinaProject(JSU071302) supported by the Construct Program of the Key Discipline in Hunan Province,ChinaProject(2015JJ2115) supported by the Natural Science Foundation of Hunan Province,China
文摘The leaching kinetics of molybdenum from Ni-Mo ore in sulfuric acid solution with sodium peroxodisulfate was studied.The effects including leaching temperature, reaction time, particle size, stirring speed, and concentrations of sulfuric acid and sodium peroxodisulfate were investigated. The leaching process of molybdenum from Ni-Mo ore is controlled by the chemical reaction through the solid layer across the unreacted shrinking core. The apparent activation energy of the leaching of molybdenum is calculated to be 41.0 k J/mol and the leaching kinetics equation of molybdenum from Ni-Mo ore is expressed as1-(1-a)1/3=3405.7exp[-41030.0/(RT)]t.
基金Shahid Chamran University of Ahvaz and Isfahan University of Technology for the financial supports they provided for this study
文摘This work aims to investigate the efficiency of Fariman sepiolite from Iran as an adsorbent to remove Cd from aqueous solutions. The effects of different experimental factors such as the initial Cd concentration, contact time and the sorbent dose were investigated through a series of batch adsorption experiments. The results show that the adsorption capacity of sepiolite for Cd increases with the contact time, the initial concentration of Cd solutions and the sorbent dose. Sorption of Cd by Fariman sepiolite is rapid within the first hour of the experiment and then slowly increases until a pseudo equilibrium is approached at 8 h. The results also show that the time-dependent Cd sorption data are better described with pseudo second-order （7〉0.999） than that of pseudo first-order （r2〉0.971） kinetic model. Equilibrium isotherm studies show that the experimental data are better correlated by the Freundlich adsorption isotherm （7〉0.995） than the Langmuir （P〉0.825）. It is suggested that both adsorption and cation exchange reactions are responsible for the sorption of Cd by the sepiolite, and the mineral has a very good potential to remove Cd from aqueous solutions.
