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1.
The extraction of low concentration rare earth elements at high phase ratio was investigated. The traditional extraction set-up, such as mixer-settler, have drawbacks of easy emulsification, difficult separation and low efficiency if operated at the above condition. Membrane dispersion micro-extractor, owing to its well-dispersed, high surface-to-volume ratio and fast mass transfer rate, was employed in our work. Nd(III), Eu(III), Er(III) were chosen to represent light, medium, heavy rare earth elements (REEs). The extraction process of REEs with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (P507) was investigated by membrane dispersion micro-extractors. Firstly, the extraction equilibrium of these three elements was explored in the stirred conical flasks, and it is indicated that the extraction efficiencies can be 0.95, 0.97 and 0.98, respectively within 40 min at phase ratio of 100:1. Then the effects of operational conditions such as the residence time, organic and aqueous flow rates on extraction efficiency were also explored in micro-extractors. The results indicate that the efficiency decreases and then increases if increasing aqueous phase flow rate, residence time and droplets' diameter are the key factors of this process. Increasing the phase ratio reduces the extraction efficiency significantly. When the REEs solution has an initial pH of 4.00, the flow rates of continuous and dispersed phase are 40 and 1.6 mL/min, respectively, and 90 mg/L Nd (III), Eu(III) and Er(III) is extracted by 1 mol/L P507 at the out-let length of 8 m. The extraction efficiencies are 0.978, 0.983 and 0.991, respectively. Finally the stripping process was also studied with the micro-extractor. The stripping efficiencies of Nd(III), Eu(III) and Er(III) can reach 0.99, 0.96 and 0.91, respectively when the out-let length is 8 m and the concentration of hydrochloric acid is 1 mol/L. The developed approach offers a novel and simple strategy on the fast extraction and enrichment of low concentration rare earth elements from waste water.  相似文献   

2.
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.  相似文献   

3.
The feasibility of a rare earth separation process by electrolytic reduction of Eu(III) with a titanium cathode was examined by cathodic polarization characteristics of Eu(III) on a titanium electrode and batch-type electrolytic reduction of Eu(III) using a bipolar electrolytic cell in acidic aqueous solutions of EuCl3. The reduction of Eu(III) started at a cathode potential of about −0.6 Vvs standard hydrogen electrode (SHE). The plateau current for the reduction of Eu(III) was observed at around −1.2 Vvs SHE, but a further decrease in cathodic potential resulted in a decrease in the reduction current, which was caused by the hydrolysis of Eu(III). The plateau current is a diffusion-limiting current in the reduction of Eu(III). In the batch-type electrolytic reduction of Eu(III) using a bipolar electrolytic cell, complete reduction of aqueous 0.1 kmol m−3 EuCl3 solution with a current efficiency of over 0.6 could be achieved by keeping the catholyte pH at 2, to avoid hydrolysis of Eu(III). The final percent Eu(III) reduction of the solution from an industrial europium purification process, which contained other rare earths, was lower than that of a synthetic EuCl3 single electrolyte solution probably because of a more significant hydrolysis of rare earth ions. However, the final percent reduction increased with decreasing reduction current, the concentration of rare earths, and the viscosity of solution.  相似文献   

4.
The pH dependent sorption of rare earth ions (La(Ⅲ), Ce(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Y(Ⅲ), Sm(Ⅲ), Eu(Ⅲ), Gd(Ⅲ), Tb(Ⅲ), Dy(Ⅲ), Ho(Ⅲ), Er(Ⅲ), Lu(Ⅲ), and Yb(Ⅲ)) from HAC-NaAC buffer solution at 298 K by D152 resin containing -COOH function groups were presented. The sorption behaviors of D152 resin for Sm(Ⅲ) were discussed as an example. The effects of operational conditions such as pH, temperature, and contact time were studied. The statically saturated sorption capacity was 510 mg/g resin at pH 6.70 in HAc-NaAc medium at 298 K. The sorption behaviors obeyed the Freundlich isotherm. The capacity value for column study was obtained by graphical integration as 495 mg/g resin. Thomas model was applied to experimental data to predict the breakthrough curve and to determine the characteristic parameters of the column useful for process design.  相似文献   

5.
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.  相似文献   

6.
By introducing the amine group into phosphorus extractant, a novel aminophosphine compound bis(2-ethylhexyl) ((2-ethylhexylamino)methyl) phosphine oxide (DEHAPO, abbreviated as A) was synthesized for the extraction of cerium (IV) (Ce(IV)) from sulfate medium (H2SO4). The influence factors including extractant concentration, H2SO4 concentration and temperature on the Ce(IV) extraction were investigated and discussed. It is found that the extraction ability of Ce(IV), thorium (IV) (Th(IV)) and rare earths (REs(III)) (La, Gd, Yb) decreases in sulphate medium in the following order: Ce(IV) > Th(IV) > REs(III). The extraction process is an exothermic reaction and the thermodynamic parameters were calculated. The extracted complex of Ce(HSO4)2SO4·A in loaded organic solution was identified by the slope methods and further proved by FT-IR spectral analysis. Stripping studies indicate that Ce(IV) can be effectively stripped from the organic phase. The results of separation factors (β) and saturation loading capacity demonstrate that DEHAPO could be used to selectively extract Ce(IV) from sulphate medium with high separation efficiency and good extraction ability.  相似文献   

7.
Solid-liquid extraction of gadolinium was investigated from phosphoric acid medium using commercial amino phosphonic acid resin, Tulsion CH-93. The experimental conditions studied included equilibration time, acid concentration, mass of the resin, metal concentra-tion, loading and elution. The percent extraction of Gd(Ⅲ) was studied as a function of phosphoric acid (0.05-3 mol/L) using Tulsion CH-93 resin. The corresponding lgD vs. equilibrium pH plot gave straight line with a slope of 1.8. The percent extraction decreased with acid con-centration increasing, conforming ion exchange mechanism. Under observed experimental conditions the loading capacity of Tulsion CH-93 for gadolinium was 10.6 mg/g. Among several eluants screened, the quantitative elution of Gd(Ⅲ) from loaded Tulsion CH-93 was obtained with ammonium oxalate (0.15 mol/L). The extraction behavior of commonly associated metals with gadolinium was studied as a function of phosphoric acid concentration. Tulsion CH-93 resin showed selective extraction towards heavy rare earths (Lu and Yb) which could be sepa-rated from other rare earths at 3 mol/L H3PO4, similar to wet phosphoric acid (3-5 mol/L). On the other hand Gd(Ⅲ) and other rare earths were studied with chelating resin Tulsion CH-90. Light rare earths were highly extracted and these could be separated from heavy rare earths and Gd.)  相似文献   

8.
In view of the problem of ammonia-nitrogen wastewater pollution in rare earths extraction and separation, the novel saponification agent of organic phase, which is magnesium bicarbonate solution, was prepared with the natural rich and cheap dolomite as raw material through carbonation process. The behavior and purification of main impurities ions in the carbonation process as well as the application effect of the novel saponification agent in the extraction and separation was researched. The results showed that the concentration of Fe, Al, Si impurities ions was less than 5 ppm in the saponification agent through the development of effective removal technology, respectively. When the novel saponification agent was used in the extraction and separation, magnesium utilization rate was more than 95%, and rare earths extraction rate above 99.5% has achieved. Therefore, the technology could replace ammonia-water to saponify the organic phase in rare earth extraction and separation process.  相似文献   

9.
The extraction of Eu(Ⅲ) with β-diketone, HA, and monodentate or bidentate Lewis bases, B, into chloroform and the luminescence properties of the extracted species were studied. Pivaloyltrifluoroacetone, Hpta, and 2-thenoyltfifluoroacetone, Htta, were used as the β-diketones. The Lewis bases, B, were tetraethyl methylene diphosphonate, POPO, which was bidentate, and diethyl benzylphosphonate, PhPO which was monodentate. Based on the extraction data, the stability constants, log β, of the first complexes between tfis(β-diketonato)Eu(Ⅲ) and the phosphonate, EuA3B, were determined to be 6.0 for the POPO complex and 3.40 for the PhPO complex. The Eu(Ⅲ) luminescence intensity in the EuA3POPO was larger than EuA3 where A was either pta or tta at similar concentrations of Eu(Ⅲ), while that in Eu(pta)3PhPO was stronger than EuA3; however, in Eu(tta)3PhPO, it was weaker than Eu(tta)3. The POPO functions as a sensitizer, and the PhPO functions as a quencher for the tta chelate and as a sensitizer for the pta chelate. From the lifetime and quantum yield, φ, of the Eu(Ⅲ) luminescence in the complexes as well as the observation of the extractability of Eu(Ⅲ) with the Hpta and the phosphonates and of the luminescence spectra of the complexes, it was confirmed that the extraction of Eu(Ⅲ) was remarkably enhanced with a β-diketonate and a strong Lewis base, and also the ternary complex that was formed as the extracted species, showed luminescence enhancement. This phenomenon may be due the formation of a strong bond between the Eu(Ⅲ) and the strong Lewis base leading to more hydrophobicity in the extracted species and also to more effective energy transfer from the Lewis base to the Eu(Ⅲ). It was not significant whether the donor atoms were N or O.  相似文献   

10.
电感耦合等离子体质谱法(ICP-MS)测定稀土元素时,轻稀土元素Ce、Nd、Sm的氧化物等复合离子严重干扰重稀土元素Tb、Dy、Ho、Er的测定,因此对混合稀土中重稀土元素进行测定前一般需要先对其分离富集。实验在样品溶解后,将N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)用硅藻土吸附后装柱,以0.1 mol/L HNO3为样品溶液介质上柱,通过控制洗脱液的种类、酸度以及洗脱液流速,实现了轻稀土元素La、Ce、Pr、Nd与重稀土元素Tb、Dy、Ho、Er、Tm、Yb、Lu的分离和富集,建立了ICP-MS测定混合稀土氧化物中重稀土元素的方法。实验表明:控制洗脱流速为2.0 mL/min,用pH 2.0的HNO3淋洗至淋洗体积约为500 mL,继续收集洗脱液,并用ICP-MS检测其中Nd2O3含量,直至洗脱液中Nd2O3的质量浓度小于200 ng/mL,可将轻稀土元素La、Ce、Pr、Nd及少量Y、Sm、Gd洗脱;再改用350 mL 1 mol/L HCl洗脱重稀土元素,可实现重稀土元素与La、Ce、Pr、Nd及部分Y、Sm、Gd的分离;通过选择159Tb、163Dy、165Ho、167Er、169Tm、172Yb、175Lu为测定同位素可消除质谱干扰。将实验方法应用于混合稀土氧化物中重稀土元素的测定,加标回收率在93%~110%之间,相对标准偏差(RSD,n=8)在1.1%~10%之间。  相似文献   

11.
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 KLa 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.  相似文献   

12.
Acylpyrazolonesareβ diketone typechelat ingextractants,whichareextensivelyusedfortheseparationandanalysisofrareearths.Theirrareearthcomplexesmaybeusedaslasermaterials ,shiftreagentsinNMRspec troscopyandluminescentmaterialandhaveat tractedmuchattention[1 ] .…  相似文献   

13.
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.  相似文献   

14.
Developing the novel ionic liquids as the potential substitutes for conventional organic solvents in extraction of the rare-earth metals is highly desirable but challenges still remain. In this study, the well-designed carboxylic acid functionalized phosphonium based ionic liquids, (4-carboxyl)butyl-trioctyl-phosphonium chloride/nitrate, were synthesized and characterized. The as-prepared samples were tested as the undiluted hydrophobic acidic extractant for rare-earth metal ions, affording the maximal loading of 3 mol/mol towards Nd(III) in aqueous solution and the remarkable stripping performance. The results also reveal their excellent extractability and selectivity for Sc(III) in the mixtures of six rare-earth ions, as well as the outstanding separation properties between rare-earth and first row transition-metal ions (i.e., La/Ni, Sm/Co). Moreover, the extraction mechanism indicates that the extracted rare-earth complex via a proton exchange in the ionic liquid phase is structurally similar to the complexes obtained with neutral extractants. This work presents a prototype for the fabrication of the hydrophobic cation-functionalized ionic liquids for highly efficient rare-earth extraction and provides the future application in recycling of rare-earth metals from the spent magnets.  相似文献   

15.
A comparative study on extraction of Fe(III) from the HCl leach liquor of low grade iron ore tailings has been carried out using Tri-n-butyl phosphate (TBP), Cyanex 921 and Cyanex 923 in distilled kerosene. The percentage extraction of iron increased with increasing HCl and extractant concentrations. The extracted species in each case was found to be HFeCl4·S. The extraction isotherms for the above extractants indicated quantitative extraction of Fe(III) in 3-stages at O:A ratio of 3:2 with TBP, and in 2-stages at O:A ratio of 1:1 with Cyanex 921 and Cyanex 923. The stripping studies of the loaded organic phases were carried out with 0.4 M HCl. The stripping isotherms indicated 2-stages at O:A ratio of 5:2 for TBP, and 3-stages at O:A ratio of 2:3 for Cyanex 921 and Cyanex 923. From the extraction studies, the extraction efficiency of the extractants for Fe(III) was in the order TBP < Cyanex 921 < Cyanex 923. Although Cyanex 923 was found to be the best extractant, the percentage stripping of Fe from the loaded Cyanex 923 was the least. The stripping of Cyanex 923 was 94.9%, but with TBP and Cyanex 921, it was 99.8% and > 99.9%, respectively.  相似文献   

16.
P507 solvent extraction is the main method to separate and purify the rare earth products.The emulsification may be caused by the impurities in process of extracting rare earths,and these result in huge economic loss and decrease the quality of rare earth products.In recent researches,the extractant was prone to emulsification,and aluminum content of rare earth products also increased,while aluminum concentration of feed was higher.Pointing to this problem,the structural change of saponification P507 extracting aluminum and lanthanum was investigated by infrared spectroscopy,and the results showed that Al ions exchanged with H of P-O-H to become P-O-Al.Because aluminum held the characteristic of hydrophilic after extracted in the form of hydroxyl polymer ions and this provided conditions for the formation of micro emulsion.The organic phase and aqueous phase were investigated by polarizing microscope after aluminum was extracted.The results showed that the organic phase was clear when the extraction capacity of Al was less than 5 g/L.If the extraction capacity of Al exceeded 5 g/L,it formed W/O of ME(micro emulsion),leading to form emulsion of the organic phase.When Al concentration of feed was less than 1 g/L,the aqueous phase would form O/W of ME.If aluminum was extracted by saponification P507 firstly,then the the organic phase loading aluminum extracted rare earth continually,the organic and aqueous phase formed emulsification easily.  相似文献   

17.
This paper reports on the selective transport of Lu(III) from La(III) and Sm(III) through a polymer inclusion membrane (PIM) composed of 40 wt% di(2-ethylhexyl) phosphinic acid (P227) and 60 wt% poly(vinylidene fluoride) (PVDF). Basically, the changes in surface morphology, thickness and water contact angle of this PVDF-based PIM containing P227 (P227@PVDF PIM) with different polymer concentrations were investigated. By solvent extraction experiments, it is found that Lu(III) can be selectively extracted from La(III) and Sm(III) at pH 1.5 in hydrochloric acid solution. According to this result, P227@PVDF PIM was used to selectively transport Lu(III) from hydrochloric acid feed solution containing similar concentration of La(III) and Sm(III). The recovery factor of Lu(III) is 91% after 36 h, and about 5% of Sm(III) was also transported through the PIM. The concentration of La(III) in the feed solution and the stripping solution does not change. Furthermore, to overcome the ubiquitous decline of transport efficiency caused by the loss of carrier or the damage of membrane structure after long-term use of PIMs, a process for regenerating PIMs was first proposed and implemented. By comparison of the regenerated PIM with the normal PIM, there is almost no difference in the SEM image, ATR-FTIR spectrum and Lu(III) transport efficiency. It is expected that P227@PVDF PIMs have the potential to be applied to the grouped separation of rare earth elements (REEs), and this study also can be as an inspiration for the further study on the PIMs regeneration process.  相似文献   

18.
This paper described the fluoride removal from water using a new adsorbent namely mixed rare earths modified chitosan (CR). Mixed rare earths mainly contained La followed by Ce which was analyzed by in...  相似文献   

19.
P507 solvent extraction is the main method to separate and purify the rare earth products. The emulsification may be caused by the impurities in process of extracting rare earths, and these result in huge economic loss and decrease the quality of rare earth products. In recent researches, the extractant was prone to emulsification, and aluminum content of rare earth products also increased, while aluminum concentration of feed was higher. Pointing to this problem, the structural change of saponification P507 extracting aluminum and lanthanum was investigated by infrared spectroscopy, and the results showed that Al ions exchanged with H of P-O-H to become P-O-Al. Because aluminum held the characteristic of hydrophilic after extracted in the form of hydroxyl polymer ions and this provided conditions for the formation of micro emulsion. The organic phase and aqueous phase were investigated by polarizing microscope after aluminum was extracted. The results showed that the organic phase was clear when the extraction capacity of Al was less than 5 g/L. If the extraction capacity of Al exceeded 5 g/L, it formed W/O of ME (micro emulsion), leading to form emulsion of the organic phase. When Al concentration of feed was less than 1 g/L, the aqueous phase would form O/W of ME. If aluminum was extracted by saponification P507 firstly, then the the organic phase loading aluminum extracted rare earth continually, the organic and aqueous phase formed emulsification easily.  相似文献   

20.
The ternary interaction of 1, 5-bis ( 2-hydroxy-5-chlorphenyl )-3-cyanoformazan (HCPCF) with cetyhrimethylammonium bromide (CTAB) and rare earths (RE: Yb, Dy, Er and Eu) was investigated at pH 9.84 by the microsurface adsorption - spectral correction technique (MSASC). The aggregation of HCPCF on CTAB obeys the Langmuir isothermal adsorption and the interaction of RE with the HCPCF-CTAB aggregate was first found to accord with the monolayer binding. The effects of temperature and ionic strength of solution on the aggregations were made. The binary aggregate and the ternary complex were characterized.  相似文献   

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