Development of the Polish wasteless technology of apatite phosphogypsum utilization with recovery of rare earths

The most promising source of rare earth elements in Poland is apatite phosphogypsum, a waste product obtained in the process of phosphoric acid production from Kola apatite. Depending on the technology used, as the hydration ratio of calcium sulphate is changed from hemihydrate to dihydrate, the content of rare earths varies from 0.6% to 0.3% Ln₂O₃ respectively. Technological flow charts for recovering the rare earths as a byproduct have been developed. The basic process used in the technology consists of three steps: apatite phosphogypsum leaching with dilute sulphuric acid solution; separation of rare earth concentrates from leaching sulphuric acid by preconcentration via evaporization, liquid-liquid extraction or precipitation method; anhydrite production from purified phosphogypsum by recrystallization in concentrated sulphuric acid solution.     

Recovery of rare earth elements from phosphorites in the USSR

Data on the main rare earth compositions in the USSR are presented, showing that the most promising sources are phosphorites and apatites. The rate earth oxide content in the above ore concentrates reaches 1%. Technological schemes for recovering the total and individual rare earth oxides as byproducts have been developed. Extraction methods are used for recovering rare earths from nitrate solutions, with individual oxides more than 99.9% pure being obtained. Apatites are decomposed by nitric acid, yielding apart from fertilizers, strontium carbonate, sodium fluorosilicate, chalk and oxides of rare earth elements.     

稀土金属提纯方法与研究进展

对各种提纯稀土金属方法的机理进行了阐述,包括真空熔炼、电解精炼、真空蒸馏/升华、熔盐萃取、区域熔炼、固态电迁移、电化学脱氧、外吸气剂法、等离子体熔炼(通氢气或通氩气)等。对研究现状和提纯效果进行了总结。杂质去除需采用多种手段结合,同时提升装备水平,以达到提高提纯效果、降低成本、缩短生产周期的目的。     

Processing of rare earth concentrates

The paper describes process details for extraction of rare earths from an intermediate grade concentrate of Madhya Pradesh region in India and a South African slag. The xenodme concentrate obtained from the former place was an intermediate grade （47%） rare earth phosphate containing both monazite and xenotime. The South African slag was a low-grade waste product typically containing only 4% of rare earths. The rare earth resource concentrates have been treated individually by different methods such as alkali fusion and alkali leaching to convert them into their mixed oxides. Both types of materials have been processed and greater than 98% solubilization of metal values has been achieved in the intermediate grade xenotime and 80% from the South African slag. The residue of xenotime hydroxide has been washed thoroughly to collect the sodium phosphate, as by-product and the slurry pH have been adjusted to separate rare earths from thorium effectively. Other impurities such as uranium and iron have been removed by precipitation of rare earths by oxalic acid. It has been possible to recover 〉95% yttrium along with other rare earth oxides.     

Partitioning properties of rare earth ores in China

1 IntroductionChinese rare earth resources are dominant in theworld with a total amount up to 80% of the wholeworld resources. Rare earth resources in China notonly have high grade and various types, but also dis-tribute reasonably. There are many rare ea…     

稀土对化学热处理催渗作用的机理探讨

通过对稀土在渗剂中和钢中作用的不同研究结果,探讨了稀土对化学热处理催渗作用的机理,并认为稀土影响渗层的原因之一在于形成了稀土周围含碳、氮的原子气团。     

Commercial production of rare earth metals by fused salt electrolysis

The commercial production of rare earth metals by fused salt electrolytic methods is described. These methods are used to make mischmetal, cerium, lanthanum, and didymium (Nd + Pr). The feed materials consist essentially of anhydrous chlorides of the metal to be produced, augmented by additions of nonrare earth salts to yield an electrolyte with satisfactory properties for reduction. The rare earths are derived either from monazite or from bastnasite ores. The anhydrous chlorides are manufactured from the hydrated chlorides by methods which minimize oxidation or hydrolysis. Alternatively, anhydrous chlorides may be used which result from the direct chlorination of rare earth ores by the Gold-schmidt process. These are particularly suitable for electrolysis due to their very low oxychloride content. Fluorides and oxides of the rare earths are produced by wet chemical methods to provide the relatively small quantities of these compounds now used for commercial fused salt electrolysis. Reduction cells in use today are constructed mainly from a) ceramics, b) graphite, or c) iron. The advantages and disadvantages of these types of cells are described together with the typical products which result from their use. Primary attention is given to production of mischmetal (mixed rare earth metal), which is the rare earth metal produced on the largest scale today. Brief reference is made also to production of cerium, lanthanum, and didymium (Nd + Pr) metal. Finally, a resume of the current uses of these metals is presented with reference to recent trends in the industrial applications of the rare earth metals.     

稀土银合金显微组织观察与分析

对稀土银合金材料进行了金相观察和电子探针扫描分析以及显微硬度测定。实验结果表明,添加两种性质差交大的稀土元素可以充分发挥互补作用,改善银合金的组织与性能。含有稀土钇的银合金有较强的加工硬化效果和较好的抗高温氧化作用。稀土钇与轻稀土元素组合添加将有助于改善银合金的综合性能。     

含稀土铂基合金的性能研究进展

铂基合金作为功能材料使用已经较为广泛,研究表明加入稀土元素可以有效改善铂基合金的性能。综述了铂基合金在稀土微合金化和细化作用下,合金材料强度、高温稳定性以及电学性能的变化。介绍了微合金化带来的固溶强化、沉淀强化和弥散强化机制,及稀土细化合金组织作用机理。总结了引入稀土后铂基合金材料性能变化规律,为铂基合金新材料的研究开发及应用提供参考。     

Research and development trends of hydrometallurgy: An overview based on Hydrometallurgy literature from 1975 to 2019

Modern hydrometallurgy has been developing for more than 100 years and the related articles keep piling up. Based on a bibliometric analysis of the articles in Hydrometallurgy, the most authoritative journal in the field of hydrometallurgy, we try to catch the research and development trends from a global perspective. Firstly, keywords burstness shows that rare earth, recycling, lithium, ionic liquid, and thorium are the hotspots in recent years, and the economic and technological reasons behind them were discussed in depth. Secondly, the proportion of biohydrometallurgy grows fast from 5% to 13% and the related articles are almost all about bioleaching. There are some new directions such as direct preparation of materials in hydrometallurgical processes and ion-imprinted techniques. Thirdly, the advanced instrument analysis methods such as XAFS (X-ray absorption fine structure), gene sequencing, and micro-CT promote the deep understanding of hydrometallurgy mechanism. Finally, the cooperation network and contribution of the main institutes were mapped.     

Separation and recovery of rare earths via a dry chemical vapour transport based on halide gaseous complexes

The progress in the field of mutual separation of rare earths from the rare earth ores and their recovery from rare earth containing industrial waste by the dry chemical vapour transport (CVT) process mediated by the corresponding gaseous rare earth complexes with aluminum or alkali chlorides, RAI_nCl_3+3n or KRCl₄, is reviewed and discussed on the basis of their thermodynamic characteristics. The experimental results for the mutual separation and recovery of rare earth elements show the potential of this simple dry CVT process to substitute the conventional energy consuming complicated wet methods used at present for the costly preparation of the rare earths.     

中国灯用稀土荧光粉行业的发展现状

介绍了我国灯用稀土荧光粉行业的现状及存在的主要问题，阐述了提高灯用荧光粉质量的途径，并对稀土荧光粉的发展趋势提出了建议。     

A Primer on Hydrometallurgical Rare Earth Separations

This article delineates the history and details of hydrometallurgical rare earth separations and technologies. It covers the history, development, application, and recently published research into this key aspect of rare earths separation and recovery.     

Preparation of Phosphors MAl_2O_4∶Eu~(2 )(M=Ca,Sr,Ba) by Microwave Heating Technique and Their Phosphorescence

1 ＩｎｔｒｏｄｕｃｔｉｏｎＭＡｌ2 Ｏ4∶Ｅｕ2 (Ｍ =Ｃａ ,Ｓｒ ,Ｂａ )ｈａｖｅｂｅｅｎｋｎｏｗｎａｓｅｘｃｅｌｌｅｎｔｐｈｏｓｐｈｏｒｓｗｉｔｈｅｍｉｓｓｉｏｎｃｏｌｏｒｓｆｒｏｍｂｌｕｅｔｏｇｒｅｅｎｕｎ ｄｅｒｕｌｔｒａｖｉｏｌｅｔａｎｄｃａｔｈｏｄｅ ｒａｙｅｘｃｉｔａ ｔｉｏｎ[1～ 3].Ｓｔｕｄｉｅｓｏｎｐｈｏｓｐｈｏｒｓｗｅｒｅｍｏｓｔｌｙｐｅｒｆｏｒｍｅｄｉｎ 1 960ｓ′ａｎｄｅａｒｌｙ 1 970ｓ′ｍａｉｎｌｙｆｏｒｌａｍｐａｎｄｃａｔｈｏｄｅ ｒａｙｔｕｂｅａｐ ｐｌｉｃａｔｉｏｎ .Ｉｎ 1 990…     

The fascination of the rare earths—then, now and in the future

The rare earths have long been a subject of fascination to chemists and physicists. Herein, I comment on some of the prehistory leading up to the advent of the Judd–Ofelt theory of the intensities of their remarkable spectra, the origins of the Judd–Ofelt theory and its early applications. I then consider subsequent developments and extensions of the theory, its current status and its relevance to current problems of interest in rare earth spectroscopy and the future of rare earth studies.     

稀土耐热镁合金发展现状及展望

介绍了稀土耐热镁合金在俄罗斯、欧美、日本和中国的发展历史及现状。初步讨论了稀土元素对镁合金耐热性能的影响机理。对稀土耐热镁合金的研制开发、应用前景进行了简单分析。     

稀土镁球墨铸铁的起源及其早期发展--纪念稀土镁球墨铸铁投产40周年

上世纪60年代初，为了充分开发和应用我国丰富的稀土资源，包钢、锡柴、上海内研所和一机部系统的一些生产和科研单位曾各自或协同进行稀土球墨铸铁试验研究。结果发现稀土的球化作用较弱，稀土球铁的球化率不如镁球铁，但夹渣、缩松明显少于镁球铁。这种结果引起了用稀土和镁进行球化处理的设想，导致了稀土镁球铁的诞生，解决了当时国内球铁生产由于原材料和技术两方面原因引起的质量问题，对我国球墨铸铁的发展起了重要作用。研究表明，与镁球铁曲轴相比，稀土镁球铁曲轴的夹渣、缩松缺陷大幅度减少，疲劳性能和耐磨性能也明显提高，因而很快在全国范围内推广。在这之后，锡柴又试验成功稀土镁硅铁合金球化剂冲入球化处理法，取代比较不安全而且温降较大的压力包处理法，并将稀土镁球铁用于柴油机连杆、大断面曲轴以及重量达20t的16V300型气缸体，此外，1965年还研制成功等温淬火稀土镁球铁凸轮轴并投入大批量生产。稀土能中和微量元素及铁液中某些气体的反球化作用，而稀土使球墨畸变的作用也需要微量元素中和。稀土镁球铁发生石墨漂浮的临界碳当量是4．55％，与镁球铁基本相同。稀土在球铁中的应用要注意用量恰当，才能达到“扬长避短”，充分发挥其有利作用和免除其不利影响。     

Leaching process of rare earths from weathered crust elution-deposited rare earth ore

In order to strengthen the leaching procedure, the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics, hydrodynamic and mass transfer. The results show that the leaching hydrodynamics follows the Darcy law. The leaching kinetics can be described by the shrinking core model; the leaching process is controlled by diffusion of porous solid layer; and the mass transfer can be described with Van Deemter equation. This provides a theoretic basis and a scientific approach with high efficiency and optimized extraction conditions in industrial practice.     

Oxidation resistance of aluminum-coated Fe-20Cr alloys containing rare earths or yttrium

Aluminum-coated Fe-20Cr-(rare earth or yttrium) alloy foils were developed with oxidation resistance equivalent or superior to Fe-20Cr-5Al-(rare earth or yttrium) alloy foils. The coated foils were made by dipping Fe-20Cr sheet into a salt-covered aluminum bath and then rolling the sheet to foil. Oxidation resistance of the coated foil was enhanced by adding rare earths or yttrium to the Fe-20Cr substrate alloys to insure oxide adherence. Test results indicate that only sufficient addition to tie up sulfur as a stable sulfide is needed in the Fe-20Cr alloy. Aluminum-coated foils show lower oxide growth rates than similar Fe-Cr-Al alloys, most likely the result of fewer impurities (particularly Fe) is the coated foils' growing oxide scale.     

Rare Earth Compounds in Cemented Carbides with Trace Rare Earth Additions

The morphology,structure and distribution of the rare earth compounds in the YG8R.YT5R and YT14Rcemented carbides with additions of trace light rare earths were studied with an analytical electron microscope.The particles of the rare earth compounds in these alloys are all spherical and distribute at interfaces betweenthe Co-cement phase and WC hard phase or(TiW)C solid solution,and in the(TiW)C solid solution.In theYG8R and YTI4R alloys,the rare earth compound is RE_2O_3 with a bcc structure,while in the YT5R alloy.the rare earth compound is RE_2O_2S with a hcp structure.