Hydrolysis of TiCl_(4)solution is capable of preparing microscale TiO_(2)particles.This research studied the synthesis of microscale spherical TiO_(2)powders and the hydrolysis kinetics.The effects of the flow field g...Hydrolysis of TiCl_(4)solution is capable of preparing microscale TiO_(2)particles.This research studied the synthesis of microscale spherical TiO_(2)powders and the hydrolysis kinetics.The effects of the flow field generated by different agitators and baffles in the crystallizer,the initial free acid concentration,the initial equivalent TiO_(2)concentration,and the temperature on the hydrolysis progress and powder morphology were systematically studied.The results show that the flow field in a crystallizer can significantly affect the morphology and particle size of the powders,and the axial flow can improve the sphericity of the powders.The increased free HCl and equivalent TiO_(2)concentrations in the pregnant solution inhibit the forward hydrolysis reaction,prolong the time to reach equilibrium,and reduce the yield.An appropriate temperature matching the compositions of the pregnant solution is crucial for the powder morphology and size.Powders with sizes ranging from around 5 um-40μm can be tuned under controlled flow field,solution compositions,and temperature conditions.In addition,the Cheng and Wunderlich modified Avrami equation was used for the crystallization kinetic modeling.The effects of the free HCl concentration,equivalent TiO_(2)concentration,and hydrolysis temperature are reflected in the reaction rate constant and active nuclei reduction index.Increasing the free HCl and equivalent TiO_(2)concentrations will reduce the reaction rate constant and accelerate the deactivation of the active nuclei,thus increasing the final powder size,while increasing the temperature will lead to the opposite results.展开更多
提出了一种阳极直接电化学溶解与阴极间接溶出耦合溶出铜的新方法,阴极间接氧化是基于氧气还原反应和类芬顿反应产生H2O2和·OH.结果表明,在最佳电压0.25 V或电流密度6 m A/cm2下,电化学体系能产生大量活性物种,铜溶出率在直接阳极...提出了一种阳极直接电化学溶解与阴极间接溶出耦合溶出铜的新方法,阴极间接氧化是基于氧气还原反应和类芬顿反应产生H2O2和·OH.结果表明,在最佳电压0.25 V或电流密度6 m A/cm2下,电化学体系能产生大量活性物种,铜溶出率在直接阳极溶出的基础上大幅提升.展开更多
Iron-doped lithium titanium oxides were prepared via a solid-state reaction and transformed into lithium ion sieves by acid treatment.Scanning electron microscopy,X-ray photoelectron spectroscopy,and transmission elec...Iron-doped lithium titanium oxides were prepared via a solid-state reaction and transformed into lithium ion sieves by acid treatment.Scanning electron microscopy,X-ray photoelectron spectroscopy,and transmission electron microscopy showed that Fe^3+was doped into the Ti-O lattice and Ti-Fe-O bonds were formed.Iron-doping improved lithium ion adsorption from brines.The saturated adsorption capacity of the iron-doped ion sieves in brine (Li+1.56g/L,pH =8.8)was 34.8mg/g.Lithium ion adsorption fitted pseudo-second-order kinetic and Langmuir equations,indicating that lithium ion adsorption on irondoped lithium ion sieves was chemical and predominantly monolayer.In addition,the iron-doped ion sieves showed excellent selectivity for lithium ion and good recyclability.These iron-doped ion sieves therefore provide effective lithium adsorbents for practical applications.展开更多
Neodymium naphthenate-loaded organic phase stripping using sodium oxalate solution was studied to explore the feasibility of synchronous rare earth-loaded organic phase stripping,rare earth precipitation,and blank org...Neodymium naphthenate-loaded organic phase stripping using sodium oxalate solution was studied to explore the feasibility of synchronous rare earth-loaded organic phase stripping,rare earth precipitation,and blank organic phase saponification.Experimental results show that loaded organic phase stripping,rare earth precipitation,and blank organic phase saponification can be realized simultaneously.When using 20% excess of sodium oxalate over the stoichiometry with the volume ratio of organic phase to aqueous phase of 1:1 at 25℃ for 40 min,the single stage stripping rate and saponification value are about 40% and 0.29 mol/L,respectively.After 16 stages of countercurrent continuous stripping,the stripping rate of neodymium can reach 99%,the saponification value is 0.42 mol/L,the Nd^(3+) concentration in saponified organic phase is less than 0.0020 mol/L,and the main phase in precipitation isNd_(2)(C2 O_(4))3·10 H_(2) O.Afterwards,this saponified organic phase can be used in the extraction of NdCl_(3) solution,and then the loaded organic phases(neodymium naphthenate) with 0.16 mol/L Nd^(3+) can be retrieved.The morphology,particle size distribution,and composition of theNd_(2)(C2 O_(4))3·10 H_(2) O products are similar to those of the current direct precipitation products.The neodymium oxide prepared by continuous calcination of neodymium oxalate meets the national standard of China(GB/T 5240-2015).These results prove the feasibility of stripping neodymium naphthenate-loaded organic phase by using sodium oxalate solution.Sodium oxalate can serve as a stripping agent,a saponifier,and a precipitator,thereby simplifying rare earth extraction and separation.This study provides theoretical and technical support for the development of a novel method for rare earth extraction and separation.展开更多
A novel process of caustic aluminate solution decomposition by alcohol medium was developed by the Institute of Process Engineering,Chinese Academy of Sciences in order to solve the problem of low decomposi-tion ratio...A novel process of caustic aluminate solution decomposition by alcohol medium was developed by the Institute of Process Engineering,Chinese Academy of Sciences in order to solve the problem of low decomposi-tion ratio in the traditional Bayer seeded hydrolysis process.In this research,effects of additives on the crystallization ratio,secondary particle size and morphol-ogy of aluminum hydroxide in the new process were studied to obtain high-quality products.On the basis of primary selection of additives,an orthogonal design L9(3^(4))was used as a chemometric method to investigate the effects of additives.The studied parameters include the reaction style,quantity of additives,caustic soda concen-tration,as well as the combination manner.The crystal-lization ratios of sodium aluminate solution and crystal size of aluminum hydroxide,determined by ICP-OES,SEM and MLPSA(Malvern Laser Particle Size Analyzer),were used to evaluate the effects of the additives.The results showed that different combination manners could promote agglomeration or dispersion.An additive composed by Tween 80 and PEG 200 could promote agglomeration,while a spot of PEG species had a relatively strong dispersion effect.However,the additives had little effects on the crystallization ratios.According to the Raman spectra result,the added alcohol medium might serve as a kind of solvent.展开更多
基金supported by the Key Research Program of the Chinese Academy of Sciences(grant number ZDRWCN-2021-3)the Youth Innovation Promotion Association CAS(grant number 2018065)+1 种基金the National Natural Science Foundation of China(grant number 51771179)the Beijing Natural Science Foundation(grant number 2192056).
文摘Hydrolysis of TiCl_(4)solution is capable of preparing microscale TiO_(2)particles.This research studied the synthesis of microscale spherical TiO_(2)powders and the hydrolysis kinetics.The effects of the flow field generated by different agitators and baffles in the crystallizer,the initial free acid concentration,the initial equivalent TiO_(2)concentration,and the temperature on the hydrolysis progress and powder morphology were systematically studied.The results show that the flow field in a crystallizer can significantly affect the morphology and particle size of the powders,and the axial flow can improve the sphericity of the powders.The increased free HCl and equivalent TiO_(2)concentrations in the pregnant solution inhibit the forward hydrolysis reaction,prolong the time to reach equilibrium,and reduce the yield.An appropriate temperature matching the compositions of the pregnant solution is crucial for the powder morphology and size.Powders with sizes ranging from around 5 um-40μm can be tuned under controlled flow field,solution compositions,and temperature conditions.In addition,the Cheng and Wunderlich modified Avrami equation was used for the crystallization kinetic modeling.The effects of the free HCl concentration,equivalent TiO_(2)concentration,and hydrolysis temperature are reflected in the reaction rate constant and active nuclei reduction index.Increasing the free HCl and equivalent TiO_(2)concentrations will reduce the reaction rate constant and accelerate the deactivation of the active nuclei,thus increasing the final powder size,while increasing the temperature will lead to the opposite results.
基金National Natural Science Foundation of China (Nos.5176113510851774261).
文摘Iron-doped lithium titanium oxides were prepared via a solid-state reaction and transformed into lithium ion sieves by acid treatment.Scanning electron microscopy,X-ray photoelectron spectroscopy,and transmission electron microscopy showed that Fe^3+was doped into the Ti-O lattice and Ti-Fe-O bonds were formed.Iron-doping improved lithium ion adsorption from brines.The saturated adsorption capacity of the iron-doped ion sieves in brine (Li+1.56g/L,pH =8.8)was 34.8mg/g.Lithium ion adsorption fitted pseudo-second-order kinetic and Langmuir equations,indicating that lithium ion adsorption on irondoped lithium ion sieves was chemical and predominantly monolayer.In addition,the iron-doped ion sieves showed excellent selectivity for lithium ion and good recyclability.These iron-doped ion sieves therefore provide effective lithium adsorbents for practical applications.
基金Project supported by the Cultivation Project of the State Key Laboratory of Green Development and High-value Utilization of Ionic Rare Earth Resources in Jiangxi Province(20194AFD44003)。
文摘Neodymium naphthenate-loaded organic phase stripping using sodium oxalate solution was studied to explore the feasibility of synchronous rare earth-loaded organic phase stripping,rare earth precipitation,and blank organic phase saponification.Experimental results show that loaded organic phase stripping,rare earth precipitation,and blank organic phase saponification can be realized simultaneously.When using 20% excess of sodium oxalate over the stoichiometry with the volume ratio of organic phase to aqueous phase of 1:1 at 25℃ for 40 min,the single stage stripping rate and saponification value are about 40% and 0.29 mol/L,respectively.After 16 stages of countercurrent continuous stripping,the stripping rate of neodymium can reach 99%,the saponification value is 0.42 mol/L,the Nd^(3+) concentration in saponified organic phase is less than 0.0020 mol/L,and the main phase in precipitation isNd_(2)(C2 O_(4))3·10 H_(2) O.Afterwards,this saponified organic phase can be used in the extraction of NdCl_(3) solution,and then the loaded organic phases(neodymium naphthenate) with 0.16 mol/L Nd^(3+) can be retrieved.The morphology,particle size distribution,and composition of theNd_(2)(C2 O_(4))3·10 H_(2) O products are similar to those of the current direct precipitation products.The neodymium oxide prepared by continuous calcination of neodymium oxalate meets the national standard of China(GB/T 5240-2015).These results prove the feasibility of stripping neodymium naphthenate-loaded organic phase by using sodium oxalate solution.Sodium oxalate can serve as a stripping agent,a saponifier,and a precipitator,thereby simplifying rare earth extraction and separation.This study provides theoretical and technical support for the development of a novel method for rare earth extraction and separation.
基金financial support of the National Natural Science Foundation of China(Grant No.50874099)the National High Technology Research and Development Program of China(Grant No.2006AA06Z129)+1 种基金Chinese Academy of Sciences Knowledge Innovation Program(Grant No.KGCX2-YW-321-2)the Major State Basic Research Development Program of China(Grant No.2007CB613500)are gratefully acknowledged.
文摘A novel process of caustic aluminate solution decomposition by alcohol medium was developed by the Institute of Process Engineering,Chinese Academy of Sciences in order to solve the problem of low decomposi-tion ratio in the traditional Bayer seeded hydrolysis process.In this research,effects of additives on the crystallization ratio,secondary particle size and morphol-ogy of aluminum hydroxide in the new process were studied to obtain high-quality products.On the basis of primary selection of additives,an orthogonal design L9(3^(4))was used as a chemometric method to investigate the effects of additives.The studied parameters include the reaction style,quantity of additives,caustic soda concen-tration,as well as the combination manner.The crystal-lization ratios of sodium aluminate solution and crystal size of aluminum hydroxide,determined by ICP-OES,SEM and MLPSA(Malvern Laser Particle Size Analyzer),were used to evaluate the effects of the additives.The results showed that different combination manners could promote agglomeration or dispersion.An additive composed by Tween 80 and PEG 200 could promote agglomeration,while a spot of PEG species had a relatively strong dispersion effect.However,the additives had little effects on the crystallization ratios.According to the Raman spectra result,the added alcohol medium might serve as a kind of solvent.
