Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a syste...Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a systematic DFT calculation focused on the defluorination behavior between the LiAl-and MgAl-LDHs.The results indicated that the LiAl-LDHs exhibited high chemical activity before the defluorination,because of the better electronic structure.After the defluorination,the LiAl-LDHs with adsorbed-F–were also more stable than the MgAl-LDHs.In addition,the existence of coordination covalent bond for the adsorbed-F–attached to the LiAl-LDHs was confirmed.This is an important reason for the high defluorination efficiency by the LiAl-LDHs.In addition,a series of weak interaction,including hydrogen bond and van der Waals interaction were also observed.Finally,a LiAl-LDHs with excellent fluoride removal properties were synthesized well by simple hydrothermal method.The results showed that our synthesized LiAl-LDHs with the capacity of 156.09 mg/g,could be effectively defluorinated in water.Notably,it surpasses most materials and has potential applications.展开更多
The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting tem...The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting temperature and time on defluorination rate of bastnaesite were studied.The suitable conditions of steam roasting process are that the particle size of raw material is less than 74μm,the roasting temperature is 1000℃and the roasting time is 4 h.The defluorination rate of bastnaesite is close to 100%under above these conditions.When the temperature rises to 1000℃,the voids on the surface of the particles increase obviously,and there is a developed network of voids,which indicates that the fluorine oxides in bastnaesite react fully with the saturated water vapor at this stage,and a large amount of fluorine escapes in the form of hydrogen fluoride from the surface and inside of the mineral.X-ray diffraction results show that there are only rare-earth oxides in the form of Ce_(0.33)La_(0.33)Ca_(0.33)O_(1.5)and Ce_(7)O_(12)in the slag.The results of energy spectra and chemical analysis show that the fluorine in the baking sand was basically completely removed.展开更多
Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which signif...Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which significantly improved the defluorination efficiency of lepidolite particles.This improvement could be attributed to an increase in the H2O/HF ratio.The highest defluorination rate for the lepidolite particles was obtained in the fluidized bed reactor under vacuum.The rate in the vacuum reactor was 1.5-2 times that in a fixed bed reactor or conventional fluidized bed reactor.The defluorination efficiency of the lepidolite particles also improved and the consumption of steam was greatly reduced by addition of coal char.This enhancement was mainly attributed to changes in the structures of the reduced lepidolite particles.This defluorination roasting method for high lithium extraction with low water steam consumption is a promising method for lithium ore treatment.展开更多
基金supported by the National Science Fund for Distinguished Young Scholars (No.52022111)the Natural Science Foundation of China (No.51974379)the Scientific and Technological Innovation Program of Hunan Province,Huxiang Youth Talent Project (No.2020RC_(3)012)。
文摘Millions of people in poor areas are still under the threat of fluoride contamination.How to effectively separate fluorine in water is an important step to reduce the ecological risk.In this paper,we performed a systematic DFT calculation focused on the defluorination behavior between the LiAl-and MgAl-LDHs.The results indicated that the LiAl-LDHs exhibited high chemical activity before the defluorination,because of the better electronic structure.After the defluorination,the LiAl-LDHs with adsorbed-F–were also more stable than the MgAl-LDHs.In addition,the existence of coordination covalent bond for the adsorbed-F–attached to the LiAl-LDHs was confirmed.This is an important reason for the high defluorination efficiency by the LiAl-LDHs.In addition,a series of weak interaction,including hydrogen bond and van der Waals interaction were also observed.Finally,a LiAl-LDHs with excellent fluoride removal properties were synthesized well by simple hydrothermal method.The results showed that our synthesized LiAl-LDHs with the capacity of 156.09 mg/g,could be effectively defluorinated in water.Notably,it surpasses most materials and has potential applications.
基金Project supported by the National Key Research and Development Program of China(2020YFC1907500)the Fundamental Research Funds of the Ministry of Education of China(N2125033)。
文摘The bastnaesite was defluorinated by steam roasting process,and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth.The effects of particle size of raw material,roasting temperature and time on defluorination rate of bastnaesite were studied.The suitable conditions of steam roasting process are that the particle size of raw material is less than 74μm,the roasting temperature is 1000℃and the roasting time is 4 h.The defluorination rate of bastnaesite is close to 100%under above these conditions.When the temperature rises to 1000℃,the voids on the surface of the particles increase obviously,and there is a developed network of voids,which indicates that the fluorine oxides in bastnaesite react fully with the saturated water vapor at this stage,and a large amount of fluorine escapes in the form of hydrogen fluoride from the surface and inside of the mineral.X-ray diffraction results show that there are only rare-earth oxides in the form of Ce_(0.33)La_(0.33)Ca_(0.33)O_(1.5)and Ce_(7)O_(12)in the slag.The results of energy spectra and chemical analysis show that the fluorine in the baking sand was basically completely removed.
基金supported by the National Natural Scientific Foundation of China(Grant Nos.21978300,U1462128,and 91334108)the State Key Development Program for Basic Research of China(973 Program,Grant No.2015CB251402).
文摘Defluorination roasting of lepidolite ore in a fluidized bed reactor has been proposed for improving the extraction efficiency of lithium.In this paper,a vacuum was introduced to the fluidized bed reactor,which significantly improved the defluorination efficiency of lepidolite particles.This improvement could be attributed to an increase in the H2O/HF ratio.The highest defluorination rate for the lepidolite particles was obtained in the fluidized bed reactor under vacuum.The rate in the vacuum reactor was 1.5-2 times that in a fixed bed reactor or conventional fluidized bed reactor.The defluorination efficiency of the lepidolite particles also improved and the consumption of steam was greatly reduced by addition of coal char.This enhancement was mainly attributed to changes in the structures of the reduced lepidolite particles.This defluorination roasting method for high lithium extraction with low water steam consumption is a promising method for lithium ore treatment.
