Column leaching process of rare earth and aluminum from weathered crust elution-deposited rare earth ore with ammonium salts

In order to better understand the leaching process of rare earth （RE） and aluminum （Al） from the weathered crust elutiondepositedRE ore, the mass transfer of RE and Al in column leaching was investigated using the chromatographic plate theory. Theresults show that a higher initial ammonium concentration in a certain range can enhance the mass transfer process. pH of leachingagent in the range of 2 to 8 almost has no effect on the mass transfer efficiency of RE, but plays a positive role in the mass transferefficiency of Al under strong acidic condition （pH〈4）. There is an optimum flow rate that makes the highest mass transfer efficiency.The optimum leaching condition of RE is the leaching agent pH of 4？8, ammonium concentration of 0.4 mol/L and flow rate of0.5 mL/min. The mass transfer efficiencies of RE and Al both follow the order： （NH4）2SO4〈NH4Cl〈NH4NO3, implying thecomplexing ability of anion.

Situation and Developing Trend of Rare-Earth Countercurrent Extraction Processes Control

On the basis of the description of the rare-earth countercurrent extraction process, the on-line detecting method and equipments of rare-earth elements and the application in the process of the rare-earth countercurrent extraction are summarized. The procedure simulation of the computer, the automation control method and its current application are also mentioned in the process of rare-earth countercurrent extraction. The method of soft sensor is proposed. Optimal control method based on object-oriented rare-earth countercurrent extraction process and integrated automation system composed of process management system and process control system are presented, which are the developing direction of the automation of rare-earth countercurrent extraction process.

RECOVERING RE FROM LEACHING LIQUOR OF RARE EARTH ORE BY EXTRACTION

ＲＥＣＯＶＥＲＩＮＧＲＥＦＲＯＭＬＥＡＣＨＩＮＧＬＩＱＵＯＲＯＦＲＡＲＥＥＡＲＴＨＯＲＥＢＹＥＸＴＲＡＣＴＩＯＮＣｈｉＲｕ＇ａｎ；ＸｕＪｉｎｇｍｉｎｇ；ＨｅＰｅｉｊｉｏｎｇ；ＺｈｕＹｏｎｇｊｕｎ（ＩｎｓｔｉｔｕｔｅｏｆＮｕｃｌｅａｒＥｎｅｒｇｙＴｅｃ...

A mathematical model for column leaching of ion adsorption-type rare earth ores

Column leaching experiments with ion adsorption-type rare earth ores for different lixiviant concentrations and different column heights were carried out.A mathematical model of column leaching was constructed based on the experimental data.Two parameters(a and b)in the model were determined according to the following methodology:the ore column was divided into several units;each unit was treated with multiple leaching steps.The leaching process was simulated as a series of batch leaching experiments.Parameter a of the model was determined based on the selectivity coefficient of the balanced batch leaching experiment.Further,the influences of ammonium sulfate concentration,rare earth grade,column height,permeability coefficient,and hydrodynamic dispersion coefficient on the extraction were analyzed.Relationships between parameter b,the ammonium sulfate concentration,and the physical and mechanical properties of the ore column,were examined using dimensional analysis.It was determined that the optimal ammonium sulfate concentration for different column heights(2.5,5.0,7.5,and 10.0 cm)using the mathematical model were 5.9,6.2,7.3,and 7.7 g/L,respectively.The mathematical model can be used to estimate the breakthrough curve,leaching rate,and leaching period of rare earth ores,to achieve optimal extraction.

Effect of Cycling Loaded Rare Earths on Stripping Process in P507 Extraction System

P507 （HEH [EHP]） is an important extractant for the separation of rare earth and is widely used in industry. Since the complexes of heavy rare earth ions with saponified P507 are so stable that the rare earth ions are difficult to be exchanged and stripped by H^＋ ions. Thus, the cycled extractant loads certain amount of heavy rare earth ion after stripped by acid. This amount of rare earth ions loaded in blank organic phase is named as the ＂cycling loaded rare earth ions （CLREs）＂. In the separation process of Tm^3＋, Yb^3 ＋, and Lu^3 ＋ , the amount of CLREs carl be more than 10% of the normal capacity of saponifiedorganic phase. In fact, CLREs affect the separation efficiency and decrease the purity of the products. Based on the extracting-stripping equilibrium and mass balance, the influence of different process parameters on the amount of CLREs was studied by computer simulation. The results indicate that higher acid consumption and more stripping stages are required to eliminate CLREs. For an industrial practice, however, the acid consumption and the number of stripping stage can be designed by choosing an economic process and controlling CLREs at a reasonable level.

XRF Standardless Comparison of Mining Head and Tail Grades to Screen and Display Ore Processing Recoveries

Separation of target elements or minerals from their host rock or ore is essential to successful mining operation. The inevitable loss of a portion of the desired material that accompanies each step in the extraction process must be documented to develop the operational protocol. Superposition of the characteristic X-ray fluorescence spectra of head (crushed rock ore particles, pre-processing) and tail (post-processing particles) samples provides a direct visual comparison of relative peak sizes, and thereby the relative concentrations, of elements of interest. If the head and tail peaks are identical, none of the element was recovered in the extraction process. At the other extreme if the tail peak “flat lines”, i.e., there is no peak, there was 100% recovery of that element. Standardless visual comparison is valid if the same mass of identical starting material is incorporated into the head and tail sample analysis pucks, and XRF analytical conditions are identical. The considerable time and expense of acquiring and calibrating the standards associated with XRF analysis of 75 or more elements are avoided, a significant advantage during initial broad screening of an experimental extraction procedure. Full quantitation by XRF or an alternate technique can proceed at a later project stage, if desired. The approach retains and presents all features of the original data, thus eliminating questions about data quality, standards and their calibration, and data manipulation in processing from raw counts to concentrations in printout tables. This form of display is ideal for both the mining professional and such less technical groups as corporate staff, investors, regulators, and the public. Examples presented herein are for heap leaching;the protocol can be applied as well to any of the other traditional ore processing and beneficiation procedures, e.g., gravity concentration, magnetic and electrical separation, froth flotation, and ore sorting.

Occurrence and vertical distribution of aluminum and rare earths in weathered crust elution-deposited rare earth ore:Effect of soil solution pH and clay minerals

Weathered crust elution-deposited rare earth ore is crucial source of medium and heavy rare earths,with in-situ leaching being the most common mining method.The high contents of impurity of aluminum in the leach solution are a significant challenge for the subsequent enrichment process of rare earths.A comprehensive understanding of the occurrences and vertical distribution of aluminum and rare earths within typical vertical profiles can provide valuable insights into entire design of the in-situ leaching.This paper improves a five-step sequential extraction method to analyze the occurrence and vertical distribution of rare earths and aluminum in vertical profiles from Chongzuo and Longyan.Experimental results demonstrate that soil solution pH is the main factor affecting the vertical distribution of ionexchangeable rare earths.Both samples have distinct areas of enrichment for ion-exchangeable rare earths or aluminum.Ion-exchangeable rare earths are primary concentrated in the middle and lower parts of the ore layer(4-13 m in Chongzuo,14-22 m in Longyan),while the ion-exchangeable aluminum is mainly enriched in the upper part of the ore layer(1-5 m in Chongzuo,and 2-14 m in Longyan).The vertical distribution of inorganic hydroxy aluminum is likely influenced by the micromorphology and particle size of the clay minerals.The inorganic hydroxy aluminum concentration in Chongzuo samples decreases continuously from 415.65 to 120.95 mg/kg with increasing sampling depth,whereas the concentration in Longyan samples(110.55-171.27 mg/kg)is almost independence with sampling depth.These results provide direct guidance for the entire design of the injection well depth and the leaching parameters,thereby inhibiting the leaching of impurity of aluminum and lower the consumption of leaching agent.

Process optimization of rare earth and aluminum leaching from weathered crust elution-deposited rare earth ore with compound ammonium salts

In order to intensify the leaching process of rare earth（RE） and reduce the impurities in the leachate, ammonium chloride（NH4Cl） and ammonium nitrate（NH4NO3） were mixed as a compound leaching agent to treat the weathered crust elution-deposited RE ore. Effects of molar ratio of NH~＋_4Cl and NH_4NO_3, ammonium（NH_4） concentration, leaching agent pH and flow rate on the leaching process of RE were studied and evaluated by the chromatographic plate theory. Leaching process of the main impurity aluminium（Al） was also discussed in detail. Results showed that a higher initial ammonium concentration in a certain range could enhance the mass transfer process of RE and Al by providing a driving force to overcome the resistance of diffusion. pH almost had no effects on the mass transfer efficiency of RE and Al in the range of 4 to 8. The relationship between the flow rate and height equivalent to a theoretical plate（HETP） could fit well with the Van Deemter equation, and the flow rate at the lowest HETP was determined. The optimum conditions of column leaching for RE and Al were 1：1（molar ratio） of NH_4Cl and NH_4NO_3, 0.2 mol/L of ammonium concentration, pH 4–8 of leaching agent and 0.5 mL /min of flow rate. Under this condition, the mass transfer efficiency of RE was improved, but no change was observed for Al compared with the most widely used ammonium sulfate. Moreover, the significant difference value（around 20 mL） of retention volume at the peak concentration between RE and Al provided a possibility for their separation. It suggested the potential application of the novel compound leaching agent（NH_4Cl/NH_4NO_3）. It was found that the relative concentration of RE in the leachate could be easily obtained by monitoring the pH of leachate.

Mass transfer in heap leaching of weathered crust elution deposited rare earth ore with Al_(2)(SO_(4))_(3) solution

In order to increase efficiency and avoid NH^(4+)-N pollution in the leaching process of weathered crust elution-deposited rare earth ores,the mass transfer in heap leaching with Al_(2)(SO_(4))_(3) solution was simulated with column elution and experimentally optimized.The results indicate that the leaching yield is also up to 99%for leaching with aluminum sulfate instead of ammonium sulfate.The optimal flow rate is 60 mL/h,the height equivalent to a theoretical plate(HETP)is 1.29 mm correspondingly.The peak value position of RE^(3+)is 60 mL/h,Fe^(3+)is 100 mL/h,however,Al^(3+)is 150 mL/h,and the heap leaching process has kinetic separation effect.

Effects of organic acids on the leaching process of ion-adsorption type rare earth ore

To examine the activation of organic acids on the leaching process of ion-adsorption type rare earth ore（IRE-ore）, the leaching behavior of rare earth（RE） and zeta potential of IRE-ore were investigated in the absence and presence of carboxylic acids. The results show that all the tested organic acids（acetic acid,malonic acid, citric acid, tartaric acid, succinic acid, and malic acid） can promote RE extraction. At relatively high concentrations of organic acids, the activation efficiency of organic acids on RE extraction is generally consistent with their complexation ability; whereas at their low concentrations, the change of zeta potential on the IRE-ore surface with organic acid concentration and p H has a close association with RE extraction, which indicates that organic acids can impact the surface electrical property of IREore via their adsorption/desorption, and thereby increase/decrease the affinity of RE ions to IRE-ore.Therefore the influence of organic acids on the IRE-ore surface electrical property also plays an important role in RE extraction in addition to their complexation with RE ions.

Readsorption of rare earth elements during leaching process of ion-adsorption-type rare earth ore

A leaching experiment on simulated rare earth ore pillars with uneven grade distribution was conducted because of the readsorption of rare earth elements in the in situ leaching process of ion-adsorption-type rare earth ore.Results show that the readsorption of rare earth elements in the barren layer is the main reason for the decrease in rare earth concentration in the leachate,decrease in rare earth recovery and extension of the leaching process.This limitation could be affected by the concentration of rare earth of the influent flow passing through the barren ore layer,and pH value of leaching agents shows minimal effect during leaching.The magnesium sulfate leaching process requires higher liquid-tosolid ratio than the ammonium sulfate leaching process.The former also has lower peak value of rare earth concentration and more significant tailing in the leaching curve.The readsorption of rare earth elements in the barren layer is more severe in magnesium sulfate leaching than in ammonium sulfate leaching.Thus,areas without ore belts should be avoided when magnesium sulfate is used for leaching.

Europium recovery process by means of polymeric nanoparticles functionalized with acrylic acid,curcumin and fumaramide

Polymeric nanoparticles of poly(methyl methacrylate)were obtained by emulsion polymerization techniques in a proce ss of two stages.The particles were functionalized with acrylic acid,curcumin,and fumaramide and three series of polymeric particles were obtained.The incorporation of functional groups was confirmed by Fourier transform-infrared spectrosocopy(FT-IR)and ultraviolet-visible(UV-Vis)methods.The spherical morphology of particles with an average diameter of 100 nm was observed by scartning electron microscopy(SEM).The polymeric materials were used for recovery of[Eu]from synthetic solutions.The nanoparticles show excellent chelation capacity to trap rare-earth ions,because they recover more than 85%of[Eu]at pH of 2.The images of SEM after extraction process show arrays between particles with larger average particle sizes to 1.5 um.In addition,the particles have a good stripping capacity,exceeding 50%of it,maintaining their homogeneity in morphology and good stability in dispersion for the recovery and stripping processes.A pseudo-second model order is obtained for the extraction and stripping processes while the best results of stripping process are obtained at pH of 6.

Research and Application Progress in Countercurrent Solvent Extraction

In this article, the recent progress made by Peking University is briefly introduced. Based on Theory of Countercurrent Extraction established by Prof. Guangxian Xu, the static equilibrium and dynamic process for two- and three-outlet countercurrent extractions, and designed the optimized parameters for the real cascades to separate different rare earth minerals, which can be scaled-up to the industrial process without any further experimental verification were systematically investigated. In order to stabilize the quality of products and improve the capability of automation for extraction process, we have also established an (()^(241)Am) stimulated X-ray fluorescent energy dispersive method to detect the elemental composition in both organic and aqueous phases, which can be used as an on-line analysis method in practice. Furthermore, the expert system and the control software with open- and close-loop models have been set up. Combined with the detected data from on-line analysis, the flow-rates of extracting, feeding, scrubbing and stripping solutions can be (controlled) in an optimum status for the industrial cascades. In addition, we have developed a new multi-input and multi-output countercurrent extraction process for separating multi-component rare earth mixture with lower chemical cost and pollution.

赤泥中稀土提取与分离技术研究进展

稀土元素被誉为“工业维生素”,具有优异的磁、光、电性能。随着新能源汽车等新兴行业对稀土需求量的不断增加,稀土资源日益紧缺,从二次资源中回收稀土已成大势所趋。作为一种重要的二次资源,赤泥的产量高、堆存量大、稀土含量较高。本文介绍了赤泥中稀土元素的赋存状态,概述了从赤泥中提取分离稀土元素的湿法浸出工艺和火法-湿法联合工艺;介绍了溶剂萃取法和离子交换法两种分离工艺的研究现状,对比分析了不同处理工艺的优缺点,并通过比较不同工艺的优劣,指出降低回收成本、提高环境效益是未来赤泥资源化利用研究的重要方向。

溶剂萃取技术在磷矿加工工艺中的应用

溶剂萃取技术作为工业物质分离提纯中最常用的方法之一,被广泛应用于磷矿加工的多个环节。简述了溶剂萃取技术在磷矿制备磷酸的工艺过程的应用,重点介绍了磷矿加工过程中湿法磷酸和萃余酸的萃取、净化以及磷矿伴生氟、碘及稀土资源的萃取回收工艺,并将萃取法和其它净化方法进行了对比,最后对溶剂萃取技术在磷矿加工过程中的应用做出了总结并给出了未来的研究建议。

Development course of separating rare earths with acid phosphorus extractants: A critical review

This paper reviews the development course of separating rare earths with acid phosphorus extractants,including extraction chemistry(thermodynamics and kinetics), separation process and industrial application, the loss/degradation of extractants, etc.

Rare earth extraction from wet process phosphoric acid by emulsion liquid membrane

The recovery of rare earths （RE） during the wet processing of phosphoric acid is very important, the method of emul- sion liquid membrane （ELM） with di（2-ethylhexly） phosphate （D2EHPA） as carrier has the high selectivity while cannot provide a satisfactory extraction rate. Here novel method of emulsion liquid membrane （ELM） using Aniline as carrier to extract RE from the feed solution was proposed. The method could increase the extraction rate of RE in the real sample to 93%. The effects of dif- ferent parameters such as type and concentration of carrier and surfactant, hydrochloric acid concentration, organic to internal phase volume ratio, membrane to external phase volume ratio on extraction of RE3＋ were investigated. Quantitative extraction （〉93%） of RE3＋ was observed with 6 vol.% Aniline and 4 vol.% T 154 liquid membrane at external to internal phase volume ratio of 10 for the feed solution. The proposed method of ELM using Aniline as carrier can be expected to provide a practical, efficient, and economical method for extracting RE from phosphate leach solution with high acidity in the industry of wet process phosphoric acid.

风化壳淋积型稀土矿的基础研究

文章评述了40年来风化壳淋积型稀土矿的基础研究,包括矿床的成因及特征、稀土矿物的组成及性质,稀土与黏土矿物的关系、稀土在黏土矿物中的吸附及迁移理论,论述了风化壳淋积型稀土矿的稀土元素配分的特征及四大效应,并探讨了稀土浸出机理和风化壳淋积型稀土矿稀土浸取的三代工艺,提出了风化壳淋积型稀土矿基础研究和浸出工艺的发展方向及亟待解决的问题.

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。

P507体系反萃取条件对平衡负载稀土量的研究

P507-盐酸体系是目前应用最为广泛的稀土萃取分离体系。在用P507-盐酸体系分离含中重稀土的原料时,由于重稀土元素(Tm,Yb,Lu)难于完全反萃,使得长期使用后的空白萃取剂中仍负载一定量的重稀土(称为平衡负载)。在重稀土元素分离时,平衡负载甚至高达有机相正常负载的10%以上,严重影响了相关分离工艺的运行和实际分离效果。根据多组分萃取分离体系的萃取-反萃平衡和物料平衡关系,将平衡负载引入反萃取参数计算的物料平衡模型,对反萃过程进行了计算机仿真模拟,研究了反萃酸的相对流量、反萃级数等工艺条件对平衡负载量的影响。模拟结果表明,平衡负载随反萃级数和反萃酸流量的增大而减小;消除重稀土平衡负载、保证反萃完全需要较高的反萃酸耗和较长的反萃级数。在工业生产中,可根据实际分离需要选择相对经济的工艺条件,将平衡负载控制在合理的范围内。