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Tailoring thermal stability of ceria-zirconia mixed oxide by doping of rare earth elements:From theory to experiment

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Journal of Rare Earths 2022年第8期40卷 1272-1280页

作者： Zheng Zhao Xiaowei Huang Yongqi Zhang Juanyu Yang Meisheng Cui Yongke Hou Zongyu Feng National Engineering Research Center for Rare Earth Materials GRINM Group Corporation LimitedBeijing 100088China Griem Hi-tech Co. Ltd.Langfang 065000China Rare Earth Functional Materials(Xiong’an)Innovation Center Co. Ltd.Baoding 071700China

Ceria-zirconia mixed oxides(CZMO)are widely used in many important catalysis fields.However,pure CZMO is known to have poor thermal stability.In this paper,a strategy was proposed to design Ce_(0.475)Zr_(0.475)M_(0.05)O_(2)(M=La,Y,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Er,Lu,and,Yb)oxide surface with high thermal stability by using first-principles molecular dynamics(FPMD)simulation and experiment method.Through the structure stability analysis at different temperatures,the surface energyγas a function of R_(ion)/D_(ave)is identified as a quantitative structure descriptor for analyzing the doping effect of rare earth(RE)elements on the thermal stability of Ce_(0.475)Zr_(0.475)M_(0.05)O_(2).By doping the suitable RE,γcan be adjusted to the optimal range to enhance the thermal stability of Ce_(0.475)Zr_(0.475)M_(0.05)O_(2).With this strategy,it can be predicted that the sequence of thermal stability improvement is Y>La>Gd>Nd>Pr>Pm>Sm>Eu>Tb>Er>Yb>Lu,which was further verified by our experiment results.After thermal treatment at 1100℃for 10 h,the specific surface area(SSA)of aged Y-CZ and La-CZ samples can reach 21.34 and 19.51 m~2/g,which is 63.02%and 49.04%higher than the CZMO sample without doping because the surface doping of Y and La is in favor of inhibiting the surface atoms thermal displacement.In a word,the strategy proposed in this work can be expected to provide a viable way for designing the highly efficient CZMO materials in extensive applications and promoting the usages of the high-abundance rare-earth elements Y and La.

关键词： Cerium zirconium oxides surface Thermal stability Doping Structure descriptor Rare earth metals Theory and experiment

Extraction mechanism and separation behaviors of low-concentration Nd^(3+) and Al^(3+) in P507-H_(2)SO_(4) system

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Journal of Rare Earths 2022年第6期40卷 952-957,I0004页

作者： Hongyuan Zhang Longsheng Zhao Xudong Zheng Depeng Liu Zongyu Feng Yongqi Zhang Xiaowei Huang National Engineering Research Center for Rare Earth Materials GRINM Group Co.Ltd.Beijing 100088China General Research Institute for Nonferrous Metals Beijing 100088China Grirem Advanced Materials Co. Ltd.Beijing 100088China Rare Earth Functional Materials(Xiong’an)Innovation Center Co. Ltd.Baoding 071700China

In order to clarify the solvent extraction and separation behaviors of rare earths and impurity of Al during the extraction and enrichment of low-concentration leach solution of ion-adsorption rare earth ore,the extraction mechanism and separation behaviors of Nd^(3+)and Al^(3+)in the Nd_(2)(SO_(4))_(3)-AI_(2)(SO_(4))_(3) mixed solution using P507 were studied in this work.The extraction of Nd^(3+)and Al^(3+)follows the cation exchange mechanism.With the increase of the equilibrium pH,β_(Nd/Al) in the extraction of the Nd_(2)(SO_(4))_(3)-Al_(2)(SO_(4))_(3) mixed solution using P507 is always higher than that in the extraction of single Nd_(2)(SO_(4))_(3) and Al_(2)(SO_(4))_(3) solutions.It can be attributed to the fact that the extraction of Nd^(3+)using P507 is much faster than that of Al^(3+),and Al^(3+)is more prone to be hydrolyzed at lower pH.β_(Nd/Al) in the extraction of the Nd_(2)(SO_(4))_(3)-Al_(2)(SO_(4))_(3) mixed solution decreases gradually with the increase of mixing time within the equilibrium pH range of 1.5-1.9.The extraction of Nd^(3+)using P507 is much faster than that of Al^(3+),but the stability of Al^(3+)-Ioaded organic phase is better than that of Nd^(3+)-loaded organic phase,thus Nd^(3+)in the Nd^(3+)-loaded organic phase is gradually replaced by Al^(3+)in the aqueous phase with the increase of mixing time.

关键词： Ion-adsorption rare earth ore Low-concentration rare earth Aluminum Extraction mechanism Separation factor

Grain boundary segregation and its influences on ionic conduction properties of scandia doped zirconia electrolytes

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Journal of Rare Earths 2019年第6期37卷 645-651页

作者： Qiannan Xue Xiaowei Huang Jianxing Zhang He Zhang Zongyu Feng National Engineering Research Center for Rare Earth Materials General Research Institute for Nonferrous Metals Grirem Advanced Materials Co. Ltd.

Solid oxide fuel cell is a promising energy conversion system which converts chemical energy into electrical energy directly. Electrolyte is the key component and determines the working temperature. In this paper,ceria and scandia co-doped zirconia electrolytes sintered from 1300 to 1550 ℃ were chosen as research objects. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy were performed to characterize the ceramic samples. The effects of grain size and grain boundary element segregation on the electrical conductivity were focused. Electrochemical impedance spectroscopy was used to calculate the bulk, grain boundary and specific grain boundary conductivity. Results show that the bulk and grain boundary ionic conductivity increases with the increasing grain size.However, the specific grain boundary conductivity decreases with the increasing grain size. This is explained by the fact that Sc^(3+) is segregated at the grain boundary, which leads to higher oxygen vacancy concentration when sintered at lower temperature.

关键词： Electrolytes Co-doped zirconia Grain size Dopant segregation Ionic conductivity Rare earths

Reaction between tetravalent cerium ion and chloride ion and effect of thiourea using cyclic voltammetry

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Journal of Rare Earths 2022年第10期40卷 1635-1640页

作者： Deliang Meng Xiaowei Huang Zongyu Feng Meng Wang Juanyu Yang Chao Xia Yanyan Zhao Yuqing Wei School of Metallurgy Northeastern UniversityShenyang 110819China National Engineering Research Center for Rare Earth Materials GRINM Group Co.Ltd.Beijing 100088China GRIREM Advanced Materials Co. Ltd.Beijing 100088China General Research Institute for Nonferrous Metals Beijing 100088China

To monitor the reaction between Ce^(4+) ion and Cl-ion at the electron level,an electrochemical experiment was designed in this work.Herein,the intermediate and final products that may be produced during the redox reaction are directly tracked by using cyclic voltammetry,and the influences of Ce^(4+) ion concentration,temperatu re and F-ion on the reduction peak potential of Ce^(4+) ion were investigated.The results show that Ce^(4+) ion reacts with Cl-ion through an irreversible reaction without any intermediate products,and the rate-determining step of the reaction is diffusion during the electrode reaction.The effects of temperature(20-40℃) and Ce^(4+) ion concentration(0.04-0.12 mol/L) on the reduction peak pote ntial of Ce^(4+) ion can be ignored,but the higher the molar ratio of F-to Ce^(4+)(0-3 mol/mol),the mo re easily the reduction of Ce^(4+) ion to Ce^(3+) ion occurs.Additionally,the Ce^(4+) ions are preferentially reduced by thiourea when thiourea is added in the HCl solution,and thiourea inhibits the oxidation of Cl-ions to Cl_(2) by forming a complex with Cl-ions.This work provides a theoretical basis for the role of thiourea in inhibiting Cl_(2) production and offers a new way to find new reductants.

关键词： Electrochemical test Cyclic voltammetry Redox reaction Rare earths

Behavior of sulfate in preparation of single light rare earth carbonate by Mg(HCO_(3))_(2) precipitation method

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Journal of Rare Earths 2021年第7期39卷 850-857,I0004页

作者： Meng Wang Xiaowei Huang Zongyu Feng Chao Xia Deliang Meng Zonghe Yu National Engineering Research Center for Rare Earth Materials GRINM Group Co.Ltd.Beijing 100088China GRIREM Advanced Materials Co. Ltd.Beijing 100088China General Research Institute for Nonferrous Metals Beijing 100088China Rare Earth Functional Materials(Xiong'an)Innovation Center Co. Ltd.Baoding 071700China

The precipitation of the water-leaching solution of Baotou mixed rare earth(RE) concentrate roasted with sulfuric acid using ammonium bicarbonate for producing RE carbonate produces a mass of ammonia-nitrogen wastewater because of the relatively low solubility of rare earth sulfate.To solve the serious problem of ammonia-nitrogen pollution,new precipitators need to be developed urgently so as to meet the requirements of environmental protection and impurities content of the product(SO_(4)^(2-)<1.8 wt% in RE carbonates products).In this paper,we studied the effects of feeding modes on the behavior of SO_(4)^(2-) during the preparation of light RE carbonate(RE=La,Ce,Pr,Nd) from their sulfate solutions using Mg(HCO_(3))_(2) as a precipitant.The results indicate that the contents of SO_(4)^(2-) in the La and Ce precipitates using positive feeding mode exceed 16 wt% because of the formation of La_(2)(CO_(3))2.15(-SO_(4))0.85·4 H_(2)O and Ce_(2)(CO_(3))_(2).15(SO_(4))0.85·3H_(2)O,while those of the Pr and Nd precipitates are 4 wt%-5 wt% since they exist in the form of n-carbonate.The precipitates prepared using synchronous feeding mode are all RE carbonate with only 4 wt%-5 wt% of SO_(4)^(2-) enclosed in the precipitation.The content of SO_(4)^(2-) in the RE carbonate obtained using reverse feeding mode is the lowest.Among them,the content of SO_(4)^(2-) in La precipitate is only 1.40 wt%.Both synchronous and reverse feeding modes can effectively reduce the content of SO_(4)^(2-)in RE carbonate,which provides theoretical guidance for the preparation of qualified light RE carbonate products by Mg(HCO3)2 precipitation method.

关键词： Rare earth sulfate Magnesium bicarbonate Rare earth carbonate Sulfate ion Complex salt

SO_(4)^(2-)-modified La,Y-doped ceria-zirconia with high oxygen storage capacity and its application in Pd-only three-way catalysts

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Journal of Rare Earths 2022年第5期40卷 737-744,I0003页

作者： Hao Wang Yongke Hou Yongqi Zhang Meisheng Cui Fang Chen Xiaowei Huang Juanyu Yang Zongyu Feng National Engineering Research Center for Rare Earth Materials GRINM Group Corporation LimitedBeijing 100088China Grirem Hi-tech Co. Ltd.Langfang 065000China Grirem Advanced Materials Co. Ltd.Beijing 100088China Rare Earth Functional Materials(Xiong’an)Innovation Center Co. Ltd.Baoding 071700China

As the oxygen redox ability shows great effects on the catalytic performances of ceria-zirconia based materials,many strategies have been utilized to improve the oxygen storage capacity.Here in this study,we report a simple and facile approach to prepare a SO_(4)^(2-)-modified La,Y-doped ceria-zirconia material(SO/CZLY-f)with high oxygen storage capacity.Due to the additional redox process between SO_(4)^(2-)and S^(2-),oxygen storage capacity of SO/CZLY-f(745.3μmol O_(2)/g)is about 1.6 times higher than that of La,Ydoped ceria-zirconia material without SO_(4)^(2-)modification.Moreover,the catalytic activities and stability of the corresponding Pd-only three-way catalyst were measured.Compared to that of Pd@CZLY-f,the operation window of CO,full conversion temperature of HC and NO over Pd@SO/CZLY-f are obviously widened and lowered,respectively.After aging treatment at 1100℃for 4 h,the superiority of aged Pdloading composite is still maintained.

关键词： SO_(4)^(2-)-modified La Y-doped ceria-zirconia Oxygen storage materials Three-way catalytic performances Rare earths

Effects ofiron and temperature on solubility of light rare earth sulfates in multicomponent system of Fe2(SO4)3-H3PO4-H2SO4 synthetic solution

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Journal of Rare Earths 2020年第11期38卷 1243-1250,I0004页

作者： Shiliang Chen Longsheng Zhao Meng Wang Zongyu Feng Chao Xia Yang Xu Xiaowei Huang National Engineering Research Center for Rare Earth Materials GRINM Group Co.Ltd.Beijing 100088China Grirem Advanced Materials Co. Ltd.Beijing 100088China General Research Institute for Nonferrous Metals Beijing 100088China School of Metallurgy Northeastern UniversityShenyang 110819China

Numerous light rare earth elements(LREE)minerals containing Fe and P were processed by sulfuric acid roasting method,and the leaching solution mainly comprises LREE sulfate,Fe2(SO4)3,H3PO4,and H2SO4,however,the solubility data of LREE sulfates in this system is few.This work studies the solubility of LREE sulfates in independent LREE sulfate system RE2(SO4)3-Fe2(SO4)3-H3 PO4-H2SO4(RE=La,Ce,Pr or Nd)and mixed LREE sulfates system(La,Ce,Pr,Nd)2(SO4)3-Fe2(SO4)3-H3 PO4-H2SO4 at different temperature(25-65℃)and concentrations of Fe2(SO4)3(Fe2 O3,0-50.13 g/L),H2SO4(0.5 mol/L),and H3 PO4(P2 O5,20.34 g/L)based on the industrial operating condition at low liquid and solid ratio 2:1.The solubility of each LREE sulfate in the independent system(La2 O3,12.25-20.88 g/L;CeO2,41.93-62.35 g/L;Pr6 O11,37.34-56.69 g/L;Nd2 O3,26.60-37.63 g/L)is much higher than that of the mixed system(La2 O3,6.95-11.03 g/L;CeO2,10.63-21.51 g/L;Pr6 O11,11.56-20.36 g/L;Nd2 O3,12.36-19.79 g/L)under the same other conditions.The results also indicate that,in the two systems,both Fe and the temperature have negative effects on the solubility of LREE sulfates.That may occur due to the complication reactions between the complexes of RESO4+and Fe(SO4)2-.However,the influence degree of temperature and iron concentration on the LREE sulfates solubility varies in the two systems and among different LREE species.This research is of theoretical significance for optimizing the conditions of the sulfuric acid process for recovering the LREE from the mixed LREE bearing minerals as well as the single LREE containing secondary rare earth scraps.

关键词： Rare earth sulfate Solubility Ferric sulfate Sulfuric acid Phosphoric acid

Preparation of crystalline mixed rare earth carbonates by Mg(HCO3)2 precipitation method

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Journal of Rare Earths 2020年第3期38卷 292-298页

作者： Zonghe Yu Meng Wang Liangshi Wang Longsheng Zhao Zongyu Feng Xu Sun Xiaowei Huang National Engineering Research Center for Rare Earth Materials General Research Institute for Nonferrous MetalsBeijing 100088China Grirem Advanced Materials Co. Ltd.Beijing 100088China

In acid treatment technology of Baotou mixed rare earth ore,large quantities of ammonia-nitrogen wastewater are produced in the step of ammonium bicarbonate precipitation to transform rare earth sulfate.In this paper,we adopted a green precipitant magnesium bicarbonate(Mg(HCO3)2) to substitute ammonium bicarbonate to eliminate ammonia-nitrogen pollution.The effects of n(HCO3^-):n(RE^3+),aging temperature and aging time on the crystallization using Mg(HCO3)2 precipitation method were investigated.The results indicate that the rare earths could be completely recovered when n(HCO3^-):n(RE^3+) is higher than 3.15:1.The crystal water content of rare earth carbonates is affected by the aging temperature.The precipitate has a bad filterability when the aging temperature is over 40℃.This can be attributed to the less crystallized water molecules of the hydrated rare earth carbonate precipitation.The mixed rare earth carbonates are prone to be crystalline,and have a good filterability at aging temperatures below 40℃.Meanwhile,the evolution mechanism of crystalline mixed rare earth carbonates is reasonably deduced,the amorphous rare earth carbonates are first dissolute and then recrystallized.Under the optimized aging conditions,the purity of the crystalline precipitate meets the requirements of the fine product standard(GB/T 16479-2008).The filtrated could be used to produce Mg(HCO3)2,thus to realize the recycling of magnesium sulfate.

关键词： Baotou mixed rare earth ore Magnesium bicarbonate Rare earth carbonates Ammonia-free Crystallization mechanism Filtrate recycling

Effect of phase transition during roasting of Mountain Pass rare earth concentrate on leaching efficiency of rare earths

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Journal of Rare Earths 2024年第2期42卷 409-414,I0006页

作者： Yanyan Zhao Xu Sun Deliang Meng Xiangsheng Liu Qiang Zhong Zongyu Feng National Engineering Research Center for Rare Earth Grirem Advanced Materials Co.Ltd.Beijing0088China Rare Earth Functional Materials(Xiong'an)Innovation Center Co. Ltd.Xiongan071700China General Research Institute for Nonferrous Metals Beijing100088China

To find a greener and more economical approach for treating the Mountain Pass rare earth concentrate(MPREC),a novel "Combination Method",including the processes of oxidizing roasting,HCI leaching and sulfuric acid roasting,is proposed in this research.In this paper,the effect of phase transition behavior in hydrochloric acid leaching during oxidative roasting at 450-600℃ was studied.During roasting,the bastnasite in MPREC is decomposed into CeLa_(2)O_(3)F_(3) and(Ce_(0.33),La_(0.33),Ca_(0.33))O_(1.5).As the CeLa_(2)O_(3)F_(3) phase has the fluorine-fixation effect,the generated CeLa_(2)O_(3)F_(3) phase can not be dissolved by HCI after roasting at 500 and 550℃,but it can be decomposed by HCI after roasting at over 600℃,resulting in the improvement of the leaching rate of total F element.The maximum leaching efficiency of rare earth elements(REEs) can reach 70.32 wt% at the roasting temperature of 550℃.After roasting at over 600℃,some F^-ions in the solution combined with RE^(3+) to form REF_(3) precipitate and enter the leaching residue,and the others are in the form of [CeF_(3)]^+ in the leaching solution during leaching,therefore,the leaching efficiency of non-ce rium REEs decreases while that of cerium element increases.This work provides basic research for optimizing the actual production process of MPREC.

关键词： Mountain pass rare earth mine Roasting Phase change Rare earths