Electro‐kinetic Separation of Rare Earth Elements Using a Redox‐Active Ligand

Purification of rare earth elements is challenging due to their chemical similarities. All of the deployed separation methods rely on thermodynamic properties, such as distribution equilibria in solvent extraction. Rare‐earth‐metal separations based on kinetic differences have not been examined. Herein, we demonstrate a new approach for rare‐earth‐element separations by exploiting differences in the oxidation rates within a series of rare earth compounds containing the redox‐active ligand [{2‐(t BuN(O))C₆H₄CH₂}₃N]³⁻. Using this method, a single‐step separation factor up to 261 was obtained for the separation of a 50:50 yttrium–lutetium mixture.     

Liquid-liquid extraction of uranium(VI) with 2-ethylhexyltolylsulfoxide (EHTSO)

The liquid-liquid extraction behavior of 2-ethylhexyltolylsulfoxide (EHTSO) towards uranium(VI) contained in nitric acid aqueous solution has been investigated. It was found that the extraction increases with increasing nitric acid concentration up to 5.0 mol/l and then decreases. Extraction also increases with increasing extractant concentration. The extracted species appears to be UO₂(NO₃)₂ ^.2EHTSO. The influences of temperature, NH₄NO₃ and Na₂C₂O₄ concentrations on the extraction equilibrium were also investigated and the thermodynamic functions of the extraction reaction were obtained.     

Extraction of uranium(VI) from nitric acid solution with hexyloctylsulfoxide (HxOSO)

The thermodynamic extraction of uranium(VI) with hexyloctylsulfoxide (HxOSO) has been studied. It was found that the distribution ratio increases with increasing nitric acid concentration up to 2.3 mol/l and then decreases. The distribution ratio also increases with increasing extractant concentration. The extracted species appears to be UO₂(NO₃)₂ ^.2HxOSO. The influences of temperature, sodium nitrate and oxalate concentrations on the extraction were also investigated, and the thermodynamic functions of the extraction reaction were obtained.     

阳离子交换树脂分离富集-ICP-AES法测定地质样品中15种稀土元素

样品用四酸(盐酸+硝酸+高氯酸+氢氟酸)溶解,经阳离子交换树脂分离富集后用电感耦合等离子体原子发射光谱法(ICP-AES)同时测定其中的15种的稀土元素。选用HCl(1.2mol/L)作平衡液和淋洗液,HCl(4.0mol/L)作洗脱液进行实验,测量时选择最佳的分析谱线从而避开杂质峰的干扰。各稀土元素的方法检出限均低于1.5μg/g,相对标准偏差小于11%。经标准物质验证结果可靠,适合地质样品中稀土元素的同时测量。     

Studies on Polarographic Adsorptive Wave of the System of the Rare Earth (III)-Copper(Ii)-M-Trifluomethyl Chlorophosphonazo

Abstract

A new heteronuclear complex, rare earth (III)-copper (II)-m-trifluomethyl chlorophosphonazo (CPA-mCF₃) system for determining trace rare earth ions is presented. In a medium of 0.02mol/L NH₄Cl,1. 0×10^?3mol/L Cu(II),1.0×10^?5 mol/L CPA-mCF₃, a very sensitive polarographic adsorptive wave is observed by using a single sweep oscillopolarograph at about –0.83V (vs. Ag/AgCl). The linear relationship between the peak current and the concentration of rare earth exists from 6. 0×10^?9 to 1. 0×10^?6 mol/L. The detection limit of rare earth is down to 2. 0×10^?9 mol/L for Tm³⁺. This method has been applied to determine trace RE in several samples of Chinese tea. The results are satisfactory. The composition of the complex is detected as RE (II): Cu (II): CPA-mCF₃ = 1: 1: 2.     

The Extraction of Uranium(VI) with n-Octyldecylsulfoxides (ODSO)-Toluene

The liquid-liquid extraction of uranium(VI) from aqueous nitric acid with n-octyldecylsulfoxide (ODSO) in toluene has been studied over a wide range of conditions. The extracted species appears to be UO₂(NO₃)₂·2ODSO. The extraction increased with increasing nitric acid concentration up to 2.0 mol/l and then decreased. Extraction also increased with increasing extractant concentration. The influence of temperature, salting-out agent concentration and complex anion concentration on the extraction equilibrium were also investigated, and the enthalpy of the extraction reaction was calculated.     

Extraction of uranium(VI) with bis(octylsulfinyl)methane

The liquid-liquid extraction of uranium(VI) from aqueous nitric acid with bis(octylsulfinyl)methane (BOSM) has been studied over a wide range of conditions. The extracted species appear to be UO₂(NO₃)₂·2BOSM. It was found that the extraction increased with increasing nitric acid concentration up to 8.5 mol/l and then descreased. Extraction also increased with increasing extractant concentration. The influence of temperature and salting-out agent concentration on the extraction equilibrium has also been investigated, and the enthalpy of the extraction reaction was estimated.     

Extraction of rare earth elements by high molecular weight amines from nitric acid solutions

Extraction of trivalent rare earth elements by a high molecular weight primary amine /decylamine/ from 0.5–3M nitric acid solutions, containing potassium phosphotungstate /K₁₀P₂W₁₇O₆₁/, has been investigated. The effect of nitric acid and potassium phosphotungstate concentration of the organic solvent, and lanthanides ionic radii upon distribution coefficients has been studied. It has been established that decylamine solutions in chloroform can be used for the group isolation of rare earth elements and for their separation.     

Flow injection on-line preconcentration with an ion-exchange resin coupled with microwave plasma torch-atomic emission spectrometry for the determination of trace rare earth elements

A sensitive and rapid on-line method has been developed for the determination of trace amounts rare earth elements (REEs), lanthanum, cerium, neodymium and yttrium, by microwave plasma torch-atomic emission spectrometry (MPT-AES) combined with micro-column separation/preconcentration. A strong basic cinnamene anion exchange resin is used for matrix elimination and enrichment of the analytes. The adsorbed metal ions are subsequently eluted from the column and transferred into the detector with nitric acid solution for simultaneous multi-element determination. Various factors influencing the separation/preconcentration, sample flow rate, loading time, acidity and eluent flow rate, concentration, have been studied in detail. Under the optimized conditions, the detection limits for lanthanum, cerium, neodymium and yttrium based on three times of standard deviations of blank by 7 replicates are 0.89, 2.02, 1.56 and 0.78 μg·L^− 1, and the relative standard deviations are determined as 1.54, 4.29, 4.95 and 3.90%, respectively. The proposed method has been applied to the analysis of the four REEs in high purity Sm₂O₃, Eu₂O₃, Gd₂O₃, Tb₂O₃, Dy₂O₃, Yb₂O₃, and Lu₂O₃ samples with a recovery range of 95.1-104.8%.     

Liquid-liquid extraction of uranium(VI) from nitric acid solutions with bis(octylsulfinyl)ethane (BOSE)

The liquid-liquid extraction behavior of uranium(VI) from aqueous nitric acid with bis(octylsulfinyl)ethane (BOSE) in 1,1,2,2-tetrachloroethane has been studied over a wide range of conditions. The extracted species appears to be UO₂(NO₃)₂·2BOSE. It was found that the extraction increases with increasing nitric acid concentration up to 7 mol/l and then decreased. Extraction also increases with increasing extractant concentration. The influence of temperature and salting-out agent concentration on the extraction equilibrium and stripping of uranium(VI) was also investigated and the enthalpy of the extraction reaction was obtained.     

Self-assembling structures in the extraction of some rare earth elements in systems with D2EHPA

Effect of different factors on the formation of self-assembling structures in a dynamic interfacial layer in LnA₃-H₂O-D2EHPA-solvent extraction systems was studied. Increase in temperature was shown to inhibit the formation of the self-assembling structures. An exposure of dynamic interfacial layer to mechanical vibrations using a microvibrator was found to prevent structurization and provide higher aggregative stability of disperse system. The structure deteriorates when exposed to vibration and decomposes to aggregates at rather high power. On the extraction of rare earth elements (REE) of yttrium subgroup, the system partially recovers its properties after termination of exposure to vibration, i.e., it is coagulation and thixotropic and becomes condensation in time.     

N,N,N′,N′-tetrabutylmalonamide as a new extractant for extraction of nitric acid and uranium(VI) in toluene

N,N,N,N-tetrabutylmalonamide (TBMA) was synthesized and used for extraction of uranyl(II) ion from nitric acid media in toluene. The effects of nitric acid concentration, extractant concentration, temperature and salting-out agent (LiNO₃) on distribution coefficients of uranyl(II) ion have been studied. The extraction of nitric acid is also studied. The main adduct of TBMA and HNO₃ is HNO₃. TBMA in 1.0 mol/l nitric acid solution. The 1:2:3 complex of uranyl(II) ion, nitrate ion and TBMA as extracted species is further confirmed by IR spectra of the extraction of uranyl(II) ion with TBMA, and found that the NO ₃ ^– in the extraction species UO₂(NO₃)₂·3TBMA did not participate in coordination of uranyl(II) ion. The values of thermodynamic parameters have also been calculated.     

Highly Efficient Hydrophosphonylation of Aldehydes and Unactivated Ketones Catalyzed by Methylene‐Linked Pyrrolyl Rare Earth Metal Amido Complexes

A series of rare earth metal amido complexes bearing methylene‐linked pyrrolyl‐amido ligands were prepared through silylamine elimination reactions and displayed high catalytic activities in hydrophosphonylations of aldehydes and unactivated ketones under solvent‐free conditions for liquid substrates. Treatment of [(Me₃Si)₂N]₃Ln(μ‐Cl)Li(THF)₃ with 2‐(2,6‐Me₂C₆H₃NHCH₂)C₄H₃NH ( 1 , 1 equiv) in toluene afforded the corresponding trivalent rare earth metal amides of formula {(μ‐η⁵:η¹):η¹‐2‐[(2,6‐Me₂C₆H₃)NCH₂](C₄H₃N)LnN(SiMe₃)₂}₂ [Ln=Y ( 2 ), Nd ( 3 ), Sm ( 4 ), Dy ( 5 ), Yb ( 6 )] in moderate to good yields. All compounds were fully characterized by spectroscopic methods and elemental analyses. The yttrium complex was also characterized by ¹H NMR spectroscopic analyses. The structures of complexes 2 , 3 , 4 , and 6 were determined by single‐crystal X‐ray analyses. Study of the catalytic activities of the complexes showed that these rare earth metal amido complexes were excellent catalysts for hydrophosphonylations of aldehydes and unactivated ketones. The catalyzed reactions between diethyl phosphite and aldehydes in the presence of the rare earth metal amido complexes (0.1 mol %) afforded the products in high yields (up to 99 %) at room temperature in short times of 5 to 10 min. Furthermore, the catalytic addition of diethyl phosphite to unactivated ketones also afforded the products in high yields of up to 99 % with employment of low loadings (0.1 to 0.5 mol %) of the rare earth metal amido complexes at room temperature in short times of 20 min. The system works well for a wide range of unactivated aliphatic, aromatic or heteroaromatic ketones, especially for substituted benzophenones, giving the corresponding α‐hydroxy diaryl phosphonates in moderate to high yields.     

Yttrium oxide nanopowders from carbonate precursors

Reactions of solutions of yttrium oxide in nitric acid with a 1.67 M NH₄HCO₃ solution were studied by direct and back titration. When the concentration of the reacting solution was within 0.031–0.052 mol/L (as Y₂O₃), yttrium carbonate Y₂(CO₃)₃ · nH₂O (n ≈ 2.5) of fibrous or spherulitic morphology precipitated. When the concentration was decreased to 0.022 mol/L, a new phase of platy morphology appeared. Heating these precipitates to 650–680°C yielded yttrium oxide having coherent scattering domain sizes of 40–80 nm. Y₂O₃ particles retain the precursor morphology.     

Solvent extraction separation of hafnium with 4-methyl-3-pentene-2-one

A new method for the extractive separation of hafnium from zirconium is presented. Zirconium is extracted with pure mesityl oxide from 4M nitric acid/4M sodium nitrate medium, followed by extraction of hafnium with mesityl oxide from 0.4M hydrochloric acid/2M ammonium thiocyanate medium. It is possible to accomplish clean separations of Hf from Zr in ratios from 1:20 to 1:200. The separation of hafnium from commonly associated elements such as scandium, yttrium, uranium, thorium, alkali and alkaline earth metals in 500:1 weight ratio to hafnium is also possible.     

8-羟基喹啉对稀土钐和钇的萃取行为

研究了8-羟基喹啉（HQ）-庚烷体系从硝酸介质中萃取钐、钇的行为。 考察了HQ浓度、平衡水相pH值及NO-3离子浓度对稀土分配比的影响。 研究结果表明,稀土萃取分配比随水相pH值、8-羟基喹啉浓度的增加而增大,随水相中NO-3浓度的增高而降低。 根据斜率法及电荷平衡原理确定萃合物的组成为M(NO3)·Q(HQ)(OH), HNO3 体系中HQ萃取Sm3+、Y3+属络合机理。     

Preorganized, cone-conformational calix[4]arene possessing four propylenephosphonic acids with high extraction ability and separation efficiency for trivalent rare earth elements

p-t-Octylcalix[4]arene with tetraphosphonic acid at lower rim in cone conformation has been designed and synthesized as a new extraction reagent to investigate the extraction behavior of the nine trivalent rare earth elements: La, Pr, Nd, Sm, Eu, Gd, Ho, Y, and Er. The extraction of rare earth metals with the present extractant occurs by a simple ion-exchange mechanism. The stoichiometry of the extractant to rare earth metal ion was determined to be 2:1 based on the extraction equation, half pH values, pH_1/2, and the difference in the values of the extraction equilibrium constants of nine trivalent rare earth elements and separation factors between adjacent rare earth elements. This allowed for comparison of the estimated extraction efficiency and selectivity. The present extractant exhibited extremely high extractability and sufficiently high separation efficiency of rare earth metals, compared with calix[4]arene tetraphosphonic acid at upper rim, calix[4]arene tetraacetic acid at lower rim as previously reported and the commercial extraction reagent. This results was attributed to size and multidentate effects based on the preorganized cyclic structure of calix[4]arene and to the original selectivity of functional group for heavier rare earth elements.     

Dinuclear Rare‐Earth Metal Alkyl Complexes Supported by Indolyl Ligands in μ‐η2:η1:η1 Hapticities and their High Catalytic Activity for Isoprene 1,4‐cis‐Polymerization

Two series of new dinuclear rare‐earth metal alkyl complexes supported by indolyl ligands in novel μ‐η²:η¹:η¹ hapticities are synthesized and characterized. Treatment of [RE(CH₂SiMe₃)₃(thf)₂] with 1 equivalent of 3‐(tBuN?CH)C₈H₅NH ( L₁ ) in THF gives the dinuclear rare‐earth metal alkyl complexes trans‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH(CH₂SiMe₃)}Ind)RE(thf)(CH₂SiMe₃)]₂ (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L₁ is deprotonated by the metal alkyl species and the imino C?N group is transferred to the amido group by alkyl CH₂SiMe₃ insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ‐η²:η¹:η¹ bonding modes, forming the dinuclear rare‐earth metal alkyl complexes. When L₁ is reduced to 3‐(tBuNHCH₂)C₈H₅NH ( L₂ ), the reaction of [Yb(CH₂SiMe₃)₃(thf)₂] with 1 equivalent of L₂ in THF, interestingly, generated the trans‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH₂}Ind)Yb(thf)(CH₂SiMe₃)]₂ (major) and cis‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH₂}Ind)Yb(thf)(CH₂SiMe₃)]₂ (minor) complexes. The catalytic activities of these dinuclear rare‐earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio‐ and stereoselectivities for isoprene 1,4‐cis‐polymerization.     

Synergistic extraction of uranium(VI) with tri-n-butyl phosphate and i-butyldodecylsulfoxide

Summary The synergistic extraction of uranium(VI) from aqueous nitric acid solution with a mixture of tri-n-butyl phosphate (TBP) and i-butyldodecylsulfoxide (BDSO) in toluene was investigated. The effects of the concentrations of extractant, nitric acid, sodium nitrate and sodium oxalate on the distribution ratios of uranium(VI) have been studied. The values of enthalpy change for the extraction reactions with BDSO, TBP and a mixture of TBP and BDSO in toluene were -23.2±0.8 kJ/mol, -29.2±1.4 kJ/mol and -30.6±0.6 kJ/mol, respectively. It has been found that the maximum synergistic extraction effect occurs when the molar ratio of TBP to BDSO is close to 1. The composition of the complex of the synergistic extraction is UO₂(NO₃)₂ ^. BDSO ^. TBP.     

Extraction behavior of yttriuí with diisodecylphosphoric acid from nitric acid solution

Extraction of yttrium and some of the lanthanoids by diisodecylphosphoric acid (DIDPA) has been studied as a function of nitric acid concentration in the aqueous phase and concentration of the DIDPA in n-dodecane. The distribution ratio of yttrium was found to increase with the second power of concentration of the extractant and decrease with the third power of concentration of nitric acid. As the concentration of yttrium in the organic phase increased, an amorphous solid was found to precipitate and the composition of the solid was determined to be Y(DIDP)₃. To dissolve Y(DIDP)₃ into n-dodecane, a 14-fold molar excess of DIDPA was required over Y(DIDP)₃. The distribution ratio of yttrium was found to be too high to back-extract this element by nitric acid of medium concentration.