Study on non-saponification extraction process for rare earth separation

The purpose of this study was to overcome the disadvantages of ammonia-nitrogen wastewater pollution and high cost of sodium saponification in rare earth separation process. The study focused on the non-saponification extraction technology with magnesia. The influences of the content and particle size of magnesia, reaction time, reaction temperature, and O/A on cerium extraction rate were also discussed. The results showed that the hydrogen ions of extractant were exchanged by rare earth ions when organic extractant and rare earth solution were mixed with magnesia powder, and then the exchanged hydrogen dissolved magnesia to make the acidity of the system stable. The magnesium ions were not participated in the extraction reaction. Non-saponification extraction process of rare earth had been realized. The cerium extraction rate could reach up to 99% in single stage within the optimal reaction conditions.     

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.     

STUDY ON THE SEPARATION AND EXTRACTION MECHANISM OF RARE EARTH ELEMENTS BY MEANS OF REVERSED-PHASE PAPER CHROMATOGRAPHY

Reversed-phase paper chromatography technique is used for study on the extraction mechanism and sep-aration of rare earth elements.As the stationary phase,chromatographic paper strips are impregnated with asolution of monomyristyl phosphoric acid (MPA) in chloroform.Mineral acids are used as developers.The effect of concentration of acids and/or salts upon R_f has been investigated.According to the re-sults of R_f values for a given rare earth element in various acids,the order of extraction ability isHCl>HNO_3>H_2SO_4.A tetrad effect is clearly observed.for the R_f value of rare earth elements.Theeffects of other parameters on the R_f value,such as the quantities of extractant retained by the paper and thetemperature are also examined.Based on the determination of the molar ratio of MPA to rare earth elementsand the number of H~ ions released in extraction reaction,a reasonable mechanism is proposed.The mutualseparation of heavy rare earth elements will be better than that of the light rare earth group because of thelarger separation coefficient of the former.A mixture of Ho-Er-Tm-Lu is successfully separated by thepresent method.     

Extraction and back-extraction behaviors of 14 rare earth elements from sulfuric acid medium by TODGA

The unique physical and chemical properties of rare earth elements lay the foundation for their extensive application. N,N,N',N' Tetra-octyl-3-oxopentanediamide(TODGA) is excellent in its ability of extracting rare earth elements and it is favored for green initiative. In this paper, the extraction and back-extraction of14 rare earth elements by TODGA were studied. Experiments show that in conditions of 6 mol/L sulfuric acid, the extraction temperature of 25 ℃,the phase ratio of 1:1 and 0.04 mol/LTODGA(aviation kerosene as the diluent), the extraction rates of 14 rare earth elements including lanthanum, cerium, praseodymium,neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium were 99.00%-99.73%. Mixed with hydrochloric acid and nitric acid(HCl 3.5 mol/L, HNO_30.5 mol/L), the recoveries of the 14 rare earth elements are 91.52%-99.91% when the extraction temperature is 25 ℃ and the ratio is 1:1. The following application is based on the optimum conditions above with practical samples(from the roasting production line of China North Rare Earth High-tech Company Limited) for extraction and back-extraction experiments. Experiments show that TODGA has excellent enrichment effect on 14 rare earth elements, the extraction rates are 91.36%-99.80%, the back-extraction rates are 87.29%-99.64% and the total recoveries are 81.19%-99.44%.     

Characteristic of synergistic extraction of oxalic acid with system from rare earth metallurgical wastewater

Large amount of high concentration acidic wastewater would be produced in the conversion process of chloride rare earth into oxide rare earth.It was a mixed solution of oxalic acid and hydrochloric acid,so the recycling use was very difficult.The method of liquid-liquid extraction was proposed in this paper to achieve wastewater treatment and reclamation.The mechanism of extraction of oxalic acid from the wastewater with the systems of 50% TOB+45% kerosene and 5% 2-ethyl hexanol was investigated.The composition and structure of the extracted species and the establishment of the mathematical model of the oxalic acid extraction were determined by the use of saturation method,equimolar series method.The results showed that extraction of oxalic acid by TOB was a neutral association extraction,oxalic acid existed mainly in a molecular form in the organic phase,and the extraction combination ratio was 2:1.The duality extraction system composed of extractant TOB and TOC had synergistic extraction effect on oxalic acid and chlorhydric acid,and the extraction dislribution ratio was improved greatly.The optimum volume fiaction of TOB was 0.6-0.8.     

Decomposition of mixed rare earth concentrate by NaOH roasting and kinetics of hydrochloric acid leaching process

A new clean extraction technology for the decomposition of Bayan Obo mixed rare earth concentrate by NaOH roasting is proposed.The process mainly includes NaOH roasting to decompose rare earth concentrate and HCl leaching roasted ore.The effects of roasting temperature,roasting time,NaOH addition amount on the extraction of rare earth and factors such as HCl concentration,liquid-solid ratio,leaching temperature and leaching time on the dissolution kinetics of roasted ore were studied.The experimental results show that when the roasting temperature is 550℃ and the roasting time is 60 min,the mass ratio of NaOH:rare earth concentrate is 0.60:1,the concentration of HCl is 6.0 mol/L,the ratio of liquid to solid(L/S) 6.0:1.0,and the leaching temperature 90℃,leaching time 45 min,stirring speed 200 r/min,and the extraction of rare earth can reach 92.5%.The relevant experimental data show that the process of HCl leaching roasted ore conforms to the shrinking core model,but the control mechanism of the che mical reaction process is different when the leaching temperature is different.When the leaching temperature is between 40 and 70℃,the chemical reaction process is controlled by the diffusion of the product through the residual layer of the inert material.The average surface activation energy of the rare earth element is E_a=9.96 kJ/mol.When the leaching temperature is 75-90℃,the chemical reaction process is controlled by the interface transfer across the product layer(product layer interface mass transfer) and diffusion.The average surface activation energy of rare earth elements is E_a=41.65 kJ/mol.The results of this study have certain significance for the green extraction of mixed rare earth ore.     

Migration behavior,separation and recycling of rare earth during thermal decomposition of Zhijin phosphorus ore

Zhijin phosphorus ore is a moderate and low-grade phosphorus rare-earth ore contained in mines. The separation and extraction of associated rare earth are important research topics. In this study,the migration behavior of rare earth during the thermal decomposition of Zhijin phosphorus ore and the separation and extraction of rare earth in phosphorus slag are discussed systematically. During the thermal decomposition process of phosphorus ore, almost all of the associated rare earth enters into the phosphorus slag phase but does not enter into the ferrophosphorus or gas phases. Amorphous calcium metasilicate and calcium fluosilicate are major components of phosphorus slag, and rare earth mainly exists as a calsil solid solution. Hydrochloric acid was used for acidolysis of the phosphorous slag.Under the following conditions, 96% of the rare earth in the phosphorous slag can be dissolved in the acidolysis solution: acid excess coefficient of 1.5, reaction time of 50 min and reaction temperature of 50℃. The rare earth in the acidolysis solution was separated and recycled using oxalic acid as a precipitator and NaOH as a pH modifier. At pH of 1.7, rare-earth-enriched matter with rare-earth content of 2.1 wt% was obtained, and the recovery of the rare earth was 88%.     

Study on Preparation and Property of Poly－Aminosilicone－Rare Earth Composite

The poly-aminosilicone-rare earth composite was prepared by poly-aminosilicone cross-linked with rare earth and active silanol. The thermal stability of the composites was studied by thermogravimetric analysis (TG). Force condition of the composites in electric field was analyzed and relative polarizability was derived. It is found that the composites containing different rare earth ions have different relative polarizability. The experiment results reveal that organosilicon materials with different electrical performance can be obtained by this way. Meanwhile, the absorption and flourescene spectrum of composites were also investigated. Compared to rare earth chloride, the spectrum properties of the composite are changed obviously. The possible reasons for these phenomena were discussed.     

Non-ammonia enrichment of rare earth by magnesium oxide from rare earth leaching liquor in magnesium salt system

In order to solve the problem of ammonia-nitrogen pollution in the enrichment process of the ionadsorption type rare earth ore,the technology of non-ammonia precipitation with magnesium oxide precipitant was carried out.It is determined that the rare earth precipitation efficiency is 99.6% and the purity of rare earth concentrates is only 85.89 wt%under the optimum precipitation conditions.And the contents of MgO,SO_3 and Al_2O_3 in the rare earth concentrates are 5.12 wt%,6.77 wt%and 1.78 wt%,respectively.Furthermore,the thermo-decomposition process of precipitates was investigated by TGDSC,XRD and FI-IR.The thermal decomposition process consists of two stages:the dehydration of rare earth hydroxide and alkaline rare earth sulfate within 900 ℃ and the thermal decomposition of RE_2O_2SO_4 at 900-1300 ℃.Therefore,a high-temperature calcinations method for removing SO_3 from precipitates is proposed.When the precipitates are calcined at 1300 ℃ for 2 h,the rare earth concentrates with a purity of 92.03 wt%can be acquired.Moreover,the content of SO_3 in the concentrate is only 0.46 wt%.In the MgO precipitation and high-temperature calcinations process,the raw material cost is low and the quality of rare earth concentrates is acceptable.It could have great significance for nonammonia enrichment of rare earth from the rare earth leaching liquor,and finally solve the problem of ammonia nitrogen in the extraction process of the ion-adsorption type rare earth ore within magnesium salt system.     

Extraction kinetics and kinetic separation of La(Ⅲ),Gd(Ⅲ),Ho(Ⅲ) and Lu(Ⅲ) from chloride medium by HEHEHP

Acco rding to the tetrad-effect,14 elements of lanthanides can be divided into four groups.In our previous study,a new approach was proposed for the kinetic separation of four rare earth ions La(Ⅲ),Gd(Ⅲ),Ho(Ⅲ) and Lu(Ⅲ) coming from four groups.In that study,four rare-earth ions were kinetically separated from their coexisting mixed aqueous solutions,by performing liquid-column elution using the aqueous solution containing four lanthanide rare-earth ions as the stationary phase and the dispersed organic oil droplets containing HEHEHP(2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester) extractant as the mobile phase.The study of extraction kinetics is very important for understanding the kinetic separation of rare earth ions,which was carried out in this paper.The extraction kinetics of La(Ⅲ),Gd(Ⅲ),Ho(Ⅲ) and Lu(Ⅲ) by HEHEHP diluted in heptane were investigated using single drop method.The different parameters affecting the extraction rate such as column length,specific interfacial area,rare earth ion concentration,extractant concentration,hydrogen ion concentration and temperature were separately studied and the rate equations are deduced.It is first order with respect to rare earth ion and HEHEHP concentrations,and negative first order with respect to hydrogen ion concentrations.The rate constants at 293.15 K are 10~(-6.23),10~(-5.73),10~(-5.58) and 10~(-5.43),respectively.The experimental results demonstrate that the extraction rate of La(Ⅲ), Gd(Ⅲ),Ho(Ⅲ) or Lu(Ⅲ) is diffusion-controlled,and the extraction reaction takes place at the interface rather than in the bulk phase.The extraction model was proposed.Besides,the kinetic separation of rare earth ions by HEHEHP oil drops was discussed.     

稀土串级萃取静态递推模型的研究

针对双出口稀土串级萃取分离工艺,建立了两组分静态递推模型。区别于代数模型,首先将萃取过程归结为初始萃取段、置换萃取段、进料级、置换洗涤段、初始洗涤段5种类型,然后建立了各个对象、及对象间的交互关系。利用对象之间的调用和迭代,模型求解速度快于其他模型。分析了萃取液和洗涤液流量波动对稀土产品出口纯度影响的规律,确定了检测点的最佳位置。     

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.     

从离子型稀土矿浸取液中提取稀土的技术现状与展望

综述了沉淀法、沉淀浮选法、溶剂萃取法、离子交换法、液膜分离法等方法从离子型稀土矿浸取液中提取稀土的技术研究进展.在提取稀土的各种方法中,碳酸沉淀法因成功实现了稀土母液无毒化,改善了矿山生态环境等特点,在今后很长的一段时期内仍将是从离子型稀土矿浸取液中提取稀土的主要方法.但溶剂萃取法由于可直接生产出可溶性稀土盐或稀土料液,还能对稀土进行萃取分组以制备稀土分组产品,从而改变了稀土矿山一直以来只能生产混合氧化稀土的不利局面,提高了矿山的经济效益等特点,且符合绿色化学提取稀土资源的要求,将会有很好的发展前景.     

降低离子型稀土原地浸矿残留稀土的对策探讨

离子吸附型稀土矿是国家战略资源,加强稀土废弃矿资源综合利用、充分回收残留稀土资源是今后稀土研究领域重要研究方向之一。文章在总结离子吸附型稀土矿提取工艺发展演变的基础上,重点分析了离子吸附型稀土废弃矿中残留稀土原因及其赋存状态。研究结果表明,离子吸附型稀土废弃矿中残留稀土的主要因素有浸矿过程的浸矿盲区、毛细现象、风化不完全和反吸附现象等。针对稀土残留的原因,结合实验研究,就减少稀土残留及进一步浸出回收离子吸附型稀土提出了对策,分析结果可为离子吸附型稀土矿的绿色高效提取及减少稀土资源残留提供参考依据。      

基于QPSO-ELM的稀土萃取过程组分含量预测研究

分析了稀土串级萃取分离的工艺流程,探讨了QPSO优化ELM参数的方法对稀土萃取槽中离子组分含量的预测精度与速度问题,并运用该方法对某厂镨/钕萃取中镨工艺参数的生产数据进行了现场预测分析。结果表明,该软测量方法预测速度快、精度较高,符合稀土萃取生产检测要求。     

有机次膦酸在硝酸体系下提取稀土研究

本文采用溶剂萃取法,用有机次磷酸萃取剂从富含稀土元素镧(La）、钕(Nd）、钇(Y)、铈(Ce）的硝酸溶液中提取稀土。选择盐酸为反萃剂。考察了酸度、萃取剂浓度、相比和萃取时间对萃取率和反萃率的影响,结果表明,二异丁基膦酸萃取稀土的最佳条件为：室温,酸度0.2mol/l,萃取剂浓度40%,A/O比1:5,萃取时间15min,镧（La）、钕（Nd）,铈（Ce）和钇（Y）分别为41.68%、81.30%、81.29%和100%。当利用盐酸作为反萃实验的反萃剂时其最佳条件为：室温,初始水相稀土溶液为0.3 mol/L,反萃剂盐酸为6 mol/L,负载有机相与反萃剂盐酸溶液的体积比为1:6,将反萃的震荡时间改变为5min,应用上述条件的镧(La）、钕(Nd）、铈(Ce）、钇(Y)的反萃率分别为92.45%、94.88%、95.76%、93.34%。有机次膦酸对稀土元素（La）、钕（Nd）、铈（Ce）和钇（Y）的萃取效率不同。钇的提取率高于镧、钕和铈。它是一种有机次膦酸,对轻稀土元素亲和力低,对重稀土元素亲和力强。     

Application of the Phase Transfer Catalysis in Rare Earth Solvent Extraction

ＡｐｐｌｉｃａｔｉｏｎｏｆｔｈｅＰｈａｓｅＴｒａｎｓｆｅｒＣａｔａｌｙｓｉｓｉｎＲａｒｅＥａｒｔｈＳｏｌｖｅｎｔＥｘｔｒａｃｔｉｏｎＹａｎＣｈｕｎｈｕａ（严纯华）；ＺｈａｎｇＹａｗｅｎ（张亚文）；ＬｉａｏＣｈｕｎｓｈｅｎｇ（廖春生）；ＪｉａＪｉａｎｇ...     

Extraction kinetics and kinetic separation of La(III), Gd(III), Ho(III) and Lu(III) from chloride medium by HEHEHP

According to the tetrad-effect, 14 elements of lanthanides can be divided into four groups. In our previous study, a new approach was proposed for the kinetic separation of four rare earth ions La(III), Gd(III), Ho(III) and Lu(III) coming from four groups. In that study, four rare-earth ions were kinetically separated from their coexisting mixed aqueous solutions, by performing liquid-column elution using the aqueous solution containing four lanthanide rare-earth ions as the stationary phase and the dispersed organic oil droplets containing HEHEHP (2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester) extractant as the mobile phase. The study of extraction kinetics is very important for understanding the kinetic separation of rare earth ions, which was carried out in this paper. The extraction kinetics of La(III), Gd(III), Ho(III) and Lu(III) by HEHEHP diluted in heptane were investigated using single drop method. The different parameters affecting the extraction rate such as column length, specific interfacial area, rare earth ion concentration, extractant concentration, hydrogen ion concentration and temperature were separately studied and the rate equations are deduced. It is first order with respect to rare earth ion and HEHEHP concentrations, and negative first order with respect to hydrogen ion concentrations. The rate constants at 293.15 K are 10^−6.23, 10^−5.73, 10^−5.58 and 10^−5.43, respectively. The experimental results demonstrate that the extraction rate of La(III), Gd(III), Ho(III) or Lu(III) is diffusion-controlled, and the extraction reaction takes place at the interface rather than in the bulk phase. The extraction model was proposed. Besides, the kinetic separation of rare earth ions by HEHEHP oil drops was discussed.     

我国稀土萃取分离技术的现状及发展趋势

以我国几种典型稀土矿为代表，研究了它们不同的组成特点。分析、讨论了我国现行稀土萃取分离工艺存在的问题。介绍了在酸碱消耗、存槽有机(稀土)方面都具有优势的南方离子矿和氯化稀土分离最优化稀土流程。     

包头稀土精矿处理现状及建议

包头稀土矿世界最大,在我国乃至世界稀土工业占据举足轻重的地位。综述了包头稀土精矿工业提取工艺及存在的问题,介绍了处于实验室研究阶段的其他提取工艺,对包头稀土精矿的处理提出了几点建议。