Liquid-Liquid Extraction Processes for the Separation and Purification of Rare Earths

A review of the literature on liquid-liquid extraction processes for the separation and purification of rare earths is presented. This review also discusses computer simulation programs used for the design and optimization of processes for the separation of rare earths. The lacunae in the computer simulation programs are highlighted and suggestions for future work are given.     

Separation of Rare Earths by Solvent Extraction

Abstract

Solvent extraction technology for the separation of rare earths is a recent one. This is mainly due to the low separation factors between the adjacent rare earths for any type of extractants that have been investigated so far. In spite of this inherent weakness arising due to the gradual small changes in basicity in the series of rare earths few extractants have been used on commercial scale for the separation of high purity rare earths. In this paper the mechanisms involved in the extraction of rare earths using different types of extractants like tributylphosphate, di (2-ethylhexyl) phosphoric acid, 2-ethylhexyl 2-ethylhexyl phosphonic acid and quaternary ammonium salts have been discussed. The development of suitable mathematical models of the extraction behaviour of rare earths, particularly for the liquid cation exchangers, and their suitability for the development of the processes for the separation of rare earths is highlighted. Various process parameters that have been optimised using the computer programs developed by incorporating the mathematical models have been used in the purification of rare earths. The flow sheets designed for the separation of various rare earths are also given.     

从伴生稀土磷矿中回收稀土的研究进展

介绍了国内外伴生稀土磷矿概况,综述了磷化工过程中回收稀土的方法及研究现状,展望了未来湿法磷酸生产过程中微量稀土元素的提取研究方向。     

多组分稀土串级萃取有效分离系数的研究

提出了计算多组分稀土串级萃取有效分离系数的平均分数法,研究了稀土摩尔分数对有效分离系数的影响,比较了等效组分法、数学模型法、产品分数法和平均分数法的计算结果.研究表明,仅有平均分数法计算的有效分离系数均介于最大值和最小值之间,而且其极值均与理论极值相等.平均分数法具有更宽的适应范围和更高的准确度.     

稀土串级萃取过程中"无效区"现象的探究

根据恒定混合萃取比分馏萃取体系的稳态平衡特点,推导出了关联体系萃取量S、洗涤量W的表达式,并确定了体系萃余分数Φ和萃取分数1-Φ与料液组成f_A、f_B及两相出口产品纯度(P_(A_(n+m))、P_(B_1))的关系式.通过理论分析和计算机模拟对稀土串级萃取过程中出现的"无效区"现象进行了研究,揭示了这一现象的出现与体系自身特性和所采用的操作参数之间的内在联系.     

Advances in Rare Earths Separation and Purification

The conventional method of separation of rare earths by multistage liquid-liquid extraction is still the best processing technology for their separation and purification. One of the most promising developments in the last decade that could have an impact on the rare earths separation technology is the synthesis of mucrocyclic ligands that have a high degree of selectivity in their complexation. Trivalent lanthanides have recently been transported across liquid membranes containing macrocycic ligands. The use of facilitated liquid membranes reactors in the concentration of very dilute rare eaith streams can be very effective in terms of recovery as well as environmental considerations. The electroreduction of E³⁺ to E²⁺ and the electroodixation of Ce³⁺ to Ce⁴⁺ are potential replacements for chemical reaction valence change methods. The electrolytic method eliminates the introduction of other chemical reagents that need to be treated downstream to satisfy environmental codes. Improvements in the design and control of mixer-settlers and other liquid-liquid extraction equipment will result in higher stage efficiency.     

Cyanex272与HEHEHP混合体系萃取分离重稀土的研究

选定了ＨＥＨＥＨＰ与Ｃｙａｎｅｘ ２７２组成混合体系,确定了萃取体系的最佳组成,测定了该体系的萃取容量、反萃酸度以主相邻重稀土元素之间的分离系数,考察了体系萃取性能的主要影响因素。     

从催化剂污泥中提取稀土试验研究

研究了用盐酸从催化废水治理产生的污泥中浸出稀土、铝、铁、硅,考察了浸出剂酸度、固液质量体积比、温度、浸出时间等对浸出率的影响。结果表明:在浸出剂盐酸浓度2.0mol/L、固液质量体积比1∶9、浸出时间0.5h条件下,稀土浸出率为96%,实现了稀土与铁、铝的初步分离;然后采用草酸盐沉淀法制得纯度为99%的草酸稀土。     

用叔胺萃取铀分离钍及稀土的研究

对独居石苛性钠浸出，盐酸优溶产生的优溶渣的硫酸浸出液，用叔胺Ｎ２３５萃取铀分离钍及稀土进行了研究。结果表明：铀的萃取率大于９９．５％，反铀液中ＴｈＯ＿２／Ｕ为（１．８～３．８）×１０￣（－３），ＲＥ＿ｘＯ＿ｙ／Ｕ为（１．０～１．６）１０￣（－３），萃铀余液中的Ｕ／ＴｈＯ＿２仅为（３．５～５．６）×１０￣（－５）。     

Studies on Expert System for Extraction of Rare Earths

An expert system has been developed,using LISP,for extraction of rare earths.The expert system was de-signed to mimic the deduction of chemists for rare earth separation.The knowledge base consists mainly of threeparts:(1)the extractant solvents common use and the separations of the individual rare earths;(2)the recom-mendation of process for the separation of mixed rare earths with extraetant P507;(3)the evaluation of econo-my for planning to build a rare earth factory The knowledge base of this system was organized as files includingframe files and rules.In addition,removing of the rules can be carried out in the file compiling window under theLISP environment.Both the forward-chaining and the reverse chaining were used simultaneously as the infer-ence strategies.The machine used was a microcomputer IBM PC-XT.     

三烷基氧化膦萃取稀土元素的研究

研究了国产三烷基氧化膦(混合)对稀土元素La～Gd及Y硝酸盐的萃取.试验了30%三烷基氧化膦(TRPO)-煤油-硝酸体系中水相酸度0.5mol/L～7mol/L范围内轻稀土元素的分配比和相邻两稀土元素的分离因子,测定了TRPO稀土萃合物的组成,探讨了γ射线辐照对稀土元素萃取性能的影响.     

Studies on Liquid-Liquid Extraction of Yttrium and Separation from Other Rare Earth Elements Using Bifunctional Ionic Liquids

Solvent extraction of yttrium(III) from chloride and nitrate solutions were carried out using two bifunctional ionic liquids Cyphos IL 104 and [A336/Cy272]. Comparative study with their constituent extractants showed higher extraction abilities of the ionic liquids for Y(III). The extraction behavior of yttrium using the above ionic liquids was studied as function of different parameters. Ion association neutral complexes were formed in the organic phase. 0.5 M HNO3 could strip 82% and 75.6 % yttrium from the loaded organic phases of 0.01M [A336/Cy272] and Cyphos IL 104, respectively. Separation studies involving binary systems were also investigated.     

Application of ~(241)Am EDXRF to Determine Heavy Rare Earths in RE Separation Processes by Solvent Extraction

Ａｐｐｌｉｃａｔｉｏｎｏｆ２４１ＡｍＥＤＸＲＦｔｏＤｅｔｅｒｍｉｎｅＨｅａｖｙＲａｒｅＥａｒｔｈｓｉｎＲＥＳｅｐａｒａｔｉｏｎＰｒｏｃｅｓｅｓｂｙＳｏｌｖｅｎｔＥｘｔｒａｃｔｉｏｎＪｉａＪｉａｎｇｔａｏ（贾江涛），ＭａＸｉａｏｔａｏ（马小桃），Ｙａ...     

稀土分离过程综合自动化系统研究

针对稀土工业生产过程自动化装备水平普遍较低而造成的生产成本高，产品质量一致性差，资源消耗大的问题，提出了实现稀土产品纯度和金属回收率等综合生产指标优化的稀土萃取分离生产过程综合自动化系统，讨论了由生产过程管理系统和过程控制系统两层结构组成的综合自动化系统的体系结构、功能和以萃取分离过程两端出口产品纯度为目标的优化控制策略。将所提出的系统应用于某公司HAB萃取提钇生产过程，实现了稀土萃取过程的优化控制、优化运行和优化管理，取得了显著的应用成效。     

Separation of Scandium and Rare Earths with the Method of PSO-Extraction Chromatography

Separation of scandium and rare earths was investigated by using a new extraction chromatography whichPSO was used as a stationary phase,while HCl-NH_4SCN solution as a mobile phase.The separation conditionswere studied.In this system, the separation factor(β_(Nd)~(Sc))can reach up to 1.3×10~4.The method can be applied tothe purposes of separation,purification and analysis of microquantity of Sc in the mixed rare earth.     

在磁场作用下用乙酰胺(A101)萃取稀土元素

研究了在磁场作用下，于盐酸溶液中，用乙酰胺（A101）对稀土元素的萃取。讨论了磁场的作用及萃取机理，并分析了磁场作用及使萃取上升的原因。研究结果认为：在磁场作用下稀土的萃取率稍有升高，萃取机理不变。萃取率的上升是因体系物理性质发生变化而造成。磁场作用对分配比的影响与稀土元素的磁矩大小规律性关系。     

稀土萃取有机相的无氨连续皂化试验研究

研究了稀土萃取有机相的无氨连续皂化。结果表明,用无氨皂化剂CaCO3皂化30min,有机相皂化值可达0.50~0.54mol/L,且易分相、流动性好,Ca/RE分离最佳级数为8级。以此条件在30L萃取槽中进行综合试验,结果有机相皂化值稳定在0.50~0.54mol/L之间,所得氧化物稀土总量大于99%,CaO和Cl-质量分数稳定小于0.05%;皂化成本远低于氨水和氢氧化钠的皂化成本。该技术已成功应用于国内某稀土分离厂,经济技术指标达到行业要求且稀土产品质量合格。     

磷矿中微量稀土提取技术研究进展

磷矿中伴生的微量稀土作为一种潜在的稀土资源,开展综合回收稀土的研究具有重要意义.简单介绍了磷矿中稀土含量及分布状况,综述了磷化工过程中回收稀土的最新研究进展,分别介绍了回收稀土的方法及现状,对未来磷矿中微量稀土提取技术研究方向进行了探讨.     

能谱解析法稀土萃取过程在线分析的研究

应用能量色散X荧光分析原理,采用高分辨半导体探测器和微机多道能谱仪直接获取萃取过程中由放射源激发的稀土元素K系X荧光能谱,用能谱解析方法在线分析萃取过程15个稀土元素的含量。该分析系统具有较宽的分析范围和较小的分析误差,能够较好地满足萃取过程在线分析的要求。