Study on separation of rare earth elements in complex system

The effect of the feed acidity,acetic acid concentration and rare earth concentration on the distribution ratio,separation coefficient and extraction capacity of light rare earth elements were studied in the P204(DEHPA)-HCl system and P507(HEH/EHP)-HCl system both containing acetic acid,respectively. The results showed that the distribution ratio and separation coefficient decreased with increasing of acidity,and increased with increasing of acetic acid concentration and rare earths concentration,and the extraction capacity increased with increasing of acetic acid concentration. When pH value of feed was 2.0,[RE]/[acetic acid] was 1:1 and rare earth concentration 0.35 mol/L,in P204(DEHPA) -HCl system with acetic acid,the maximum separation coefficient(β) reached to βCe /La=4.09,βPr/Ce=1.96 and βNd/Pr=1.53,and the separation ability of this extraction system was better than P507(DEHPA)-HCl system.     

Study on separation technology of Pr and Nd in D2EHPA-HCl-LA coordination extraction system

The separation coefficient of Nd/Pr was lower in D₂EHPA-HCl system. Pointing to this problem, the effect of the acidity of feed and the concentration of lactic acid on the distribution ratio, separation coefficient and extraction capacity was investigated in unsaponified D₂EHPA-HCl-LA system, and the regression equations were calculated in this paper. The results showed that the distribution ratio and separation coefficient both increased with decreasing of feed acidity and increasing of the lactic acid concentration, and the extraction capacity increased with increasing of lactic acid concentration in D₂EHPA-HCl-LA system. When the pH value of the feed was 3.5 and lactic acid concentration was 0.6 mol/L, the max separation coefficient was 1.57, and the extraction capacity was 27.87 g/L.     

用乳状液膜从氯化钠型浸出液中浓缩稀土

对乳状液膜从氯化钠型浸出液中浓缩稀土的工艺影响因素进行了考察。这些因素包括油肉比（Ｒｏｉ）、膜相中煤油和液体石蜡的比例、表面活性剂用量、内相酸度、料液中稀土浓度、水乳比（ＲＷｅ），Ｐ５０７和Ｐ２０４的比较以及搅拌时间。通过实验，获得了乳状液膜浓缩稀土的适宜配方是Ｎ２０５－Ｐ５０７－煤油－液体石蜡－ＨＣｌ以及较佳的操作条件，乳状液膜浓缩土稀土的浓度可达１００ｇ／Ｌ。稀土提取率可达９４％。     

电还原-P507萃取分离法从废钕铁硼中回收稀土工业试验

在电解槽中连续电还原废钕铁硼分解液,电还原完全后分解液进萃取槽进行萃取分离除铁,连续工业生产,稀土回收率:98.13%.回收的稀土料液可用于P507-HCl体系稀土分离.     

环烷酸萃取体系中单一稀土和铝的分配比及分离系数的研究

对不同萃取剂皂化值、料液酸度和铝浓度条件下,单一稀土和铝在环烷酸体系中的分配比和分离系数进行研究,结构表明料液的酸度较高时,皂化值为0.35 M环烷酸体系可以获得铝和稀土相对更高的分离系数及更好的分离效果。铝离子浓度较低时,料液酸度较高的条件下仍可实现稀土和铝的较好分离,而铝离子浓度较高时(150 mmol/L),料液酸度较高不利于稀土和铝的分离。     

Extraction mechanism and separation behaviors of low-concentration Nd3+ and Al3+ in P507–H2SO4 system

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 Nd³⁺ and Al³⁺ in the Nd₂(SO₄)₃–Al₂(SO₄)₃ mixed solution using P507 were studied in this work. The extraction of Nd³⁺ and Al³⁺ follows the cation exchange mechanism. With the increase of the equilibrium pH, β_Nd/Al in the extraction of the Nd₂(SO₄)₃–Al₂(SO₄)₃ mixed solution using P507 is always higher than that in the extraction of single Nd₂(SO₄)₃ and Al₂(SO₄)₃ solutions. It can be attributed to the fact that the extraction of Nd³⁺ using P507 is much faster than that of Al³⁺, and Al³⁺ is more prone to be hydrolyzed at lower pH. β_Nd/Al in the extraction of the Nd₂(SO₄)₃–Al₂(SO₄)₃ mixed solution decreases gradually with the increase of mixing time within the equilibrium pH range of 1.5–1.9. The extraction of Nd³⁺ using P507 is much faster than that of Al³⁺, but the stability of Al³⁺-loaded organic phase is better than that of Nd³⁺-loaded organic phase, thus Nd³⁺ in the Nd³⁺-loaded organic phase is gradually replaced by Al³⁺ in the aqueous phase with the increase of mixing time.     

Separation of trivalent rare earths from nitrate medium using solvent extraction with a novel extractant 2-ethylhexyl ((2-ethylhexylamino)methyl) phosphonic acid

By introducing the amine group into the structure of P227, a novel extractant 2-ethylhexyl ((2-ethylhexylamino)methyl) phosphonic acid (EEAMPA, abbreviated as HA) was synthesized for the extraction and separation of trivalent rare earths (REs) from nitrate medium. The influence factors including extractant concentration, equilibrium time, HNO₃ concentration, separation factors, cycle regeneration, stripping acidity, and actual leach liquor of metal ions, were studied systematically. The results show that the extraction ability of EEAMPA for REs decreases with increasing acidity. A possible extraction mechanism is proposed and the extracted species as REHA₃(NO₃) are confirmed by the slope analysis method. The extraction equilibrium can reach faster than P227. It shows good chemical stability and cycling regeneration. Stripping studies show that HCl is an excellent stripping agent and REs can be effectively stripped from the organic phase.     

Study on separation technology of Pr and Nd in D₂EHPA-HCl-LA coordination extraction system

The separation coefficient of Nd/Pr was lower in D2EHPA-HCl system. Pointing to this problem,the effect of the acidity of feed and the concentration of lactic acid on the distribution ratio,separation coefficient and extraction capacity was investigated in unsaponified D2EHPA-HCl-LA system,and the regression equations were calculated in this paper. The results showed that the distribution ratio and separation coefficient both increased with decreasing of feed acidity and increasing of the lactic acid concentration,and the extraction capacity increased with increasing of lactic acid concentration in D2EHPA-HCl-LA system. When the pH value of the feed was 3.5 and lactic acid concentration was 0.6 mol/L,the max separation coefficient was 1.57,and the extraction capacity was 27.87 g/L.     

稀土和铝在皂化氯代环烷酸体系中分配比及分离系数的研究

分别对萃取剂皂化值为0.35mol/L、0.40mol/L,不同料液酸度、铝浓度条件下氯化稀土溶液在皂化氯代环烷酸萃取体系中的稀土和铝分配比及分离系数进行研究,表明当料液中含有中、高浓度铝时,皂化值为0.35mol/L氯化环烷酸体系可以在较高酸度的条件下获得铝和稀土相对更高的分离系数及更好的分离效果.实际生产中可通过提高料液酸度实现铝和稀土的有效分离,同时抑制其它非稀土杂质的萃取,更有利于降低产品中杂质的含量.     

Theoretical elucidation of rare earth extraction and separation by diglycolamides from crystal structures and DFT simulations

Diglycolamides(DGAs) show excellent application prospects for the extraction and separation of rare earth metals from highly radioactive liquid wastes and rare earth ores.The extraction ability of DGAs for rare earth ions in nitrate or chloride media increases with increasing atomic number of the rare earth metal.To understand the origin of this phenomenon,three binuclear crystals [Ln(TEDGA)3][Ln(NO_3)_6] of N,N,N',N'-tetraethyldiglycolamide(TEDGA) with rare earth ions La(Ⅲ),Pr(Ⅲ) and Eu(III) were prepared and characterized crystallographically.The three complexes belong to the triclinic crystal system,P-1 space group.The bond lengths of Ln-O_(amide) are significantly shorter than those of Ln-O_(ether) in the same crystal.The Ln-O_(amide) and Ln-O_(enher) bond lengths gradually decrease with increasing atomic number of the rare earth ion.The dihedral angle formed by TEDGA and metal ions through the tridentate coordination gradually increases with increasing metal ion atomic number,tending toward the formation of sizeable planar coordination structures for the most massive rare earth ions.The structures of the compounds formed by the extractant and metal ion were optimized by means of DFT simulations.We find that the interaction between TEDGA and the rare earth ion is dominated by electrostatic interaction by analyzing binding energy,WBIs,Mulliken charge,natural electron configurations,and molecular orbital interaction.The covalent component of the Ln-O bonds of the complexes increases with increasing metal atomic number.The observed increase in extraction and separation capacity of diglycolamides for rare earth ions with increasing atomic number might be due to the formation of two fivemember rings by one tridentate ligand.The rare earth ions with large atomic numbers tend to form planar structures with large dihedral angles with DGA ligands.     

P507-N235混合萃取剂分离石煤酸浸液中钒与铁

研究了P507-N235混合萃取剂分离石煤酸浸液中钒与铁的工艺,考察了N235/P507浓度、萃原液pH、萃取时间、相比(A/O)对钒、铁萃取率及钒铁分离效果的影响。结果表明,采用0.4 mol/L P507,0.8mol/L N235为萃取剂,磺化煤油为稀释剂,pH=1.7,萃取时间5min,A/O=5/1,经4级萃取,钒萃取率可达98.36%,而铁萃取率仅为5.78%。相对现有的P204、P507单一体系,P507-N235体系具有更好的萃取能力及钒铁分离性能。     

P204-P350萃取体系萃取稀土铈的研究

用P204和P350组成的二元协同萃取体系萃取氯化铈稀土料液,研究萃取体系的震荡时间、相比及稀土离子浓度对萃取率的影响,结果表明,当P204与P350体系的振荡时间9 min、相比1:1、稀土离子浓度为0.1 mol/L时,协同萃取体系具有最佳萃取效果,此时萃取率为71％;红外表征中萃取相出现的特征峰,可定性说明萃取反...     

P507和P204在稀土分离中的应用

文章详细报道了P507和P204两种萃取剂在轻稀土镧铈-镨钕分离工业生产中的实际应用,并且对其共性、特性及生产能力等进行了比较和分析,为稀土分离领域提供了一些技术参数和投资依据。     

Solubilization behaviors of interfacial lutetium-extractant complex in a solvent extraction system

Knowledge of the solubilization behaviors of rare-earth-extractant complex is mandatory for full comprehension of interfacial phenomenon and intermediate state of rare earth (RE) ion transport from water to oil during solvent extraction. The lutetium with 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (P507) extraction system was explored as a case study for the solubilization behaviors in this paper. With a quantitative analysis of a white crud obtained in the practical process, the results demonstrate that the insoluble REL₃ (L = the anion of P507) complex enriches at the oil/water interface and forms the network polymers. Besides, with the increase of RE loading ratios in the oil phase, the interfacial tension increases while the free ligand in the bulk phase decreases, which results in the flocculation of REL₃ complex and the formation of polymers at the interface. Furthermore, the properties of the oil phase and the interface reveal that the free ligand can solubilize the REL₃ complex along with the transfer of water from microemulsion to aqueous phase. In addition, the change of aqueous acidity can regulate the solubilization behaviors of the interfacial complex to improve RE extraction efficiency. These fundamental studies will hopefully provide new insights into the solubilization of metal-extractant complex and a technical guidance to the transfer of RE from water to oil.     

萃取法Ca/La在线分离工艺

本文提出并研究了轻稀土Ｐ５０７－ＨＣｌ体系Ｌａ／Ｃｅ分离过程中的在线萃镧除钙工艺，对工艺的实施方法、流程控制及分离效果进行了阐述。结果表明：该工艺可节约设备投资，用在线萃取法进行Ｃａ／Ｌａ分离。本工艺同样适用于Ｐ２０４－ＨＣｌ等体系的类似工艺流程     

A comparative investigation into floatability of bastnaesite with three di/trialkyl phosphate surfactants

Flotation separation and recovery of rare earth minerals (REM) have returned to an important position due to the growing strategy demand for rare earth elements (REE). In this paper, a comparative investigation into the floatability of bastnaesite ((Ce,La)FCO₃) was conducted by using three di/trialkyl phosphate collectors, di(2-ethylhexyl) phosphate (DEHPA), dibutyl phosphate (DBP) and tributyl phosphate (TBP). The density functional theory (DFT) computation recommends that the chemical activity of the three phosphate collectors is in order of DEHPA ≥ DBP >> TBP, and their hydrophobization as-suggested by the lgP (oil-water partition coefficient) value is in the order of DEHPA > TBP > DBP. The micro-flotation indicates that the preferable pH values for flotation of bastnaesite with the three phosphate collectors are 7.0–8.0, and DEHPA achieves much higher flotation recovery of bastnaesite, followed by DBP, and then TBP, which coincides with their reactivity and hydrophobicity, the two prerequisites for froth flotation. The contact angle, zeta potential, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) deduce that DEHPA likely reacts with the Ce(Ⅲ) atoms of bastnaesite interface through its O atom(s) of the P(=O)–O^– group to generate the Ce–O–P bonds, and its two 2-ethylhexyl groups orient outside for attaching bubbles, resulting in flotation enrichment of bastnaesite. Furthermore, this investigation offers a novel strategy for developing collectors in selective beneficiation of REM.     

Solvent extraction of Ce(III) and Pr(III) with P507 using SiC foam as a static mixer

Extraction reactor is a major research area of interest within the field of rare earths extraction and separation. SiC foam offers excellent material characteristics as well as three-dimensional (3-D) reticulated structure; however, very little research has been carried out on its application in extraction reactor so far. In this work, a static mixer reactor based on SiC foam was designed and demonstrated to extract and separate Ce(III) and Pr(III) from nitric acid media by using 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (P507) as extractant. The structure–performance relationship between SiC foam and extraction performance was studied by experiment combined with computational fluid dynamics (CFD) simulation. The experiment data are in good agreement with the simulation results. Contrast experiment by using a Kenics mixer was carried out, and SiC foam shows better extraction and mass transfer performance. Using the optimal structural SiC foam (pore size D = 2.3 mm, open porosity ε = 85%, foam length L = 80 mm), high extraction efficiency η (Pr(III): 94.6%, Ce(III): 88.5%) and separation factor β (2.27) between Ce(III) and Pr(III) is achieved at a high total throughput of 200 mL/min. Besides, overall volumetric mass transfer coefficient K_La of Pr(III) and Ce(III) are 0.519 and 0.378 s^?1 at the residence time τ of 3.6 s, respectively, which reach the high level of microchannel reactors and are better than conventional extractors and other static mixers. SiC foam is found to be applicable as a static mixer for efficient and high-throughput extraction and separation of rare earths.     

环烷酸体系萃取分离稀土和铝的实验研究

在不改变料液酸度的条件下,研究了不同皂化值、相比和萃取级数对稀土和铝在环烷酸体系中的分配比和分离系数的影响.实验结果表明,环烷酸萃取体系分离稀土和铝的较优工艺参数为：皂化值0.25 mol/L、相比O/A=1.5,在此条件下,分配比DAl=4.035,DRE=0.111,分离系数βAl/RE=36.35,此外,随着萃取级数的增加,除铝率也会增加,当萃取级数大于2时,除铝率可达95%以上.     

富集稀土磷酸溶液中稀土的萃取研究

研究了P204从富集稀土磷酸溶液中稀土元素钇、镧、钕的萃取行为,并考察了初始水相中P_2O_5浓度、萃取相比、萃取剂浓度、萃取时间对稀土萃取效果的影响。结果表明,低磷酸浓度、较大相比、较高萃取剂浓度和较长萃取时间有利于萃取稀土,并得到了萃取优化条件:初始水相中P_2O_5浓度10%、萃取相比V_0/V_1=3/1、萃取时间15min、P204浓度30%,在室温下萃取钇、镧、钕3种稀土,单级萃取率均可达到90%以上。     

Analysis of Response Surface in the Study of RE(NO_3)_3-HNO_3-P507-Kerosene Extraction System

RE(NO_3)_3-HNO_3-P507-kerosene extraction system(RE=La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Y)was studied by the response surface technique.14 models for extracting single rare earth ele-ment in a broad range of acidity and initial rare earth concentration were obtained by using the stepwiseregression method.Three-dimensional display of the response surface of the model of extracting Er~(3 )wasshowed as an example,which reveals clearly the dependence of distribution ratio upon both initial acidity and ini-tial rare earth concentration.