Liquid–liquid extraction of yttrium using primene-JMT from acidic sulfate solutions

The liquid–liquid extraction of yttrium(III) from sulfate medium using primene-JMT is investigated with regard to extractant concentration, diluent type, equilibrium pH and time, temperature, and extraction isotherm. Aliphatic kerosene diluents were preferred compared to aromatic diluents because of higher extraction, shorter equilibrium time and good phase separation. Increasing temperature had a negative effect on yttrium(III) extraction. Quantitative yttrium(III) extraction efficiency was achieved at room temperature within 5 min using three stages of extraction with 0.4 M primene-JMT from a synthetic yttrium solution at pH 1.5 (0.2 M H₂SO₄) at a phase ratio of 1:1. A mechanism for extraction is suggested. The proposed separation of yttrium(III) from rare earth concentrate obtained from alkaline leaching of Egyptian monazite is outlined.     

Recovery of yttrium from deep-sea mud

Deep-sea mud rich in rare earth yttrium has received lots of attention from the international community as a new resource for Y. A novel process, which mainly includes acid leaching, solvent extraction, and oxalic acid precipitation-roasting, is proposed for recovery of Y from deep-sea mud. A series of experiments were conducted to inspect the impacts of various factors during the process and the optimum conditions were determined. The results show that the Y of deep-sea mud totally exists in apatite minerals which can be decomposed by hydrochloric acid and sulfuric acid solution. The highest leaching efficiency of Y is 94.53% using hydrochloric acid and 84.38% using sulfuric acid under the conditions of H~+concentration 2.0 mol/L, leaching time 60 min, liquid-solid ratio 4:1 and room temperature 25 ℃(only in case of sulfuric acid, when using hydrochloric acid, the leaching temperature should be 60 ℃). Because of the much lower leaching temperature, sulfuric acid leaching is preferred. The counter current extraction and stripping tests were simulated by a cascade centrifugal extraction tank device. Using 10 vol% P204,15 vol% TBP and 75 vol% sulfonated kerosene as extractant, 98.79% Y~(3+) and 42.60% Fe~(3+) are extracted from sulfuric acid leaching liquor(adjusted to pH = 2.0) after seven-stage counter current extraction with O/A ratio of 1:1 at room temperature, while other metals ions such as Al~(3+), Ca~(2+), Mg~(2+)and Mn~(2+) are almost not extracted. The Y~(3+) in loaded organic can be selectively stripped using 50 g/L sulfuric acid solution and the stripping efficiency reaches 99.86% after seven-stage counter current stripping with O/A ratio of 10:1 at room temperature, while only 2.26% co-extracted Fe~(3+) is stripped. The Y~(3+) of loaded strip liquor can be precipitated by oxalic acid to further separate Y~(3+) and Fe~(3+). The precipitation efficiency of Y~(3+) in loaded strip liquor can be 98.56% while Fe~(3+) is not precipitated under the conditions of oxalic acid solution concentration 200 g/L, quality ratio of oxalic acid to Y of 2, and precipitation time 0.5 h. And the precipitate was roasted at 850 ℃ for 3 h to obtain the oxide of Y in which the purity of Y_2 O_3/REO is 79.02% and the contents of major non-rare earth impurities are less than 0.21%.Over the whole process included acid leaching, solvent extraction, and oxalic acid precipitation-roasting,the yttrium yield is 82.04%.     

Extraction of yttrium in the system Y(NO3)3-HNO3-H2O-Di(2-ethylhexyl) phosphoric acid

The extraction of yttrium from the system YCl₃-Di(2-ethylhexyl) phosphoric acid (D2EHPA) has been reported previously.^1,2 The extraction equilibrium in the system Y(NO₃)₃-HNO₃-H₂O-D2EHPA in Amsco as the solvent was studied as a function of the D2EHPA concentration, acidity and aqueous yttrium concentration, and the results were compared to the choride system. The ratio of the distribution ratios for nitrate and chloride system was found to vary from 0.5 to 7.0. Formerly Post-Doctoral Associate, Chemical Engineering Division, Ames Laboratory, U. S. Atomic Energy Commission, Iowa State University, Ames, Iowa. Formerly Deputy Director, Ames Laboratory, and Professor of Chemical Engineering, Iowa State University.     

Empirical model for the extraction system YCl3ErCl3HClH2ODI-(2-ethylhexyl)phosphoric acid—n-heptane

Equilibrium data were obtained for the extraction of the binary rare earth mixture yttrium chloride-erbium chloride from 2 kmol/m³ HClH₂O solutions by 1 kmol/m³ di(2-ethylhexyl)phosphoric acid in n-heptane. Total rare earth concentration in the aqueous phase was 0.5 kmol/m³. It was found that yttrium concentrations in the organic phase exhibit negative deviations whereas erbium concentrations exhibit positive deviations from ideality. Empirical correlations for predicting these deviations were developed. The separation factor was calculated.     

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。     

Liquid extraction of rhenium(VII) and molybdenum(VI) with trialkylphosphine oxide from acidic solutions

The liquid extraction of rhenium(VII) and molybdenum(VI) ions from sulfuric, hydrochloric, and nitric acid media is studied in the temperature range from 20 to 40°C using trialkylphosphine oxide in kerosene as an extracting agent. The maximum separation of these metals is attained when they are extracted from solutions of 1.0–2.0 M H₂SO₄ (the duration of intense phase mixing was 3–5 min). The enthalpy of the studied process is estimated to be ΔH = ?32.32 kJ/mol for molybdenum and ?51.52 kJ/mol for rhenium. The chemical aspects of the extraction process studied are discussed.     

Studies of sorption and separation processes of rare earth element complexes on the anion-exchanger Wofatit SBW in the CH3OH–HNO3 system

For the 90% v/v CH₃OH–10% v/v 7 M HNO₃ system the affinity series of nitrate complexes of rare earth elements(III) for the strongly basic anion-exchanger Wofatit SBW×4% DVB was determined. The effect of ammonium nitrate and polar organic solvent addition on the effectiveness of separation of the ion-exchanging pair Y(III)–Nd(III) on Wofatit SBW×4% DVB as well as that of macrocomponent (yttrium) concentration on the yield of the purification process on Wofatit SBW×6% DVB were investigated. The weight and bed distribution coefficients for individual rare earth elements(III) were determined. It was shown that the neodymium content in the purified yttrium(III) can be decreased from 1% to 10⁻³% under controlled conditions.     

Treatment of Chloride Waste Pickle Liquor by Solvent Extraction for the Recovery of Iron

A systematic study of the extraction of Fe(III) from chloride waste pickle liquor has been investigated using Cyanex 923 diluted with kerosene to recover iron values from the pickle liquor. Various parameters were studied to optimize the conditions for maximum recovery of iron. Extraction increases with increasing concentration of both hydrochloric acid and extractant. The species extracted into the organic phase appears to be HFeCl₂ with 1 M of the solvent. Effect of various salts as additives on Fe extraction was also studied and it was found that addition of NaCl enhanced the extraction about 2.5 times as compared to that without its addition.

Saturated loading capacity was found to be 60.9 g/L Fe in four contacts at O/A of 1. The stripping of Fe(III) with different concentration of hydrochloric acid and nitric acid from the loaded Cyanex 923 was found to increase up to 1 M of both the acids and then decrease with further increase in acid concentration up to 10 M. However, 100% stripping efficiency of Fe(III) was achieved with 0.8 M oxalic acid in two countercurrent stages at an aqueous:organic phase ratio of 3:1. Extraction parameters for maximum extraction of Fe(III) were optimized.     

The extraction of iron(III) from aqueous acid solutions by di(2-ethylhexyl)phosphoric acid

The extraction of iron(III) from aqueous solutions containing sulphuric, hydrochloric and nitric acids by di(2-ethylhexyl)phosphoric acid (DEHPA) in kerosene has been investigated under different conditions. As a result, it is found that although extraction is dominated by an ion-exchange reaction, the rate of iron(III) extraction from sulphuric acid solutions to reach equilibrium is relatively slow in comparison with that from hydrochloric or nitric acid solutions. In the extraction from aqueous solutions containing hydrochloric or nitric acid, however, the DEHPA combines with iron(III) according to the solvating reaction at higher aqueous acidity. From studies on the rate of the extraction from sulphuric acid solutions, examined under non-equilibrium, it is confirmed that dependencies of extraction rate on hydrogen ion and DEHPA concentrations are in the first and inverse first orders, respectively. The hydrolyzed species is considered to interpret the extraction mechanism in this system.     

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.     

Extraction and separation of yttrium from other rare earths in chloride medium by phosphorylcarboxylic acids

Two phosphorylcarboxylic acids, 3-((bis(2-ethylhexyloxy))phosphoryl)propanoic acid (PPA) and 3-((bis(2-ethylhexyloxy))phosphoryl)-3-phenylpropanoic acid (PPPA), were synthesized for separating yttrium from other rare earths in the chloride feed of ion-adsorption type rare earth concentrate. The effect of the factors such as pH_1/2, temperature, saponification degree and phase modifiers was investigated. The separation efficiencies of PPA and PPPA are obviously better than the typical extractants such as sec-octylphenoxy acetic acid (CA-12) and naphthenic acid (NA). The extraction process of rare earths by PPA and PPPA is a cation exchanging reaction, which is similar to those of CA-12 and NA. The loaded rare earths in both PPA and PPPA systems can be effectively back-extracted by 0.5 mol/L HCl or higher concentration. A cascade extraction process for separating yttrium from other rare earths was developed using PPPA as the extractant. The yttrium product with the purity of 97.20 wt% was obtained by 35 stages of extraction and 12 stages of scrubbing.     

Enhanced separation of praseodymium and neodymium by kinetic“push and pull”system of[A336][NO_3]-DTPA in a column extractor

A new approach was suggested in present work for improving the separation between Pr(Ⅲ) and Nd(Ⅲ)by a so-called kinetic "push and pull" system consisting of [A336][NO_3] and DTPA in a column extractor.It is revealed that,when organic extractant [A336][NO_3] is continuously pumped into the column extractor in the form of dispersed oil droplets and at the same time DTPA was injected into the aqueous feed solution whet the extraction was just started,the separatiot factor of Pr(Ⅲ) to Nd(Ⅲ),βPr/Nd,increased obviously with the time,and could even achieve 21.7.Such an amazing increase in β_(Pr)/Nd value might be due to the extraction rate of Pr(Ⅲ) by [A336][NO_3] oil droplets being faster than that of Nd(Ⅲ),while the complexing rate of Nd(Ⅲ) with DTPA in the aqueous solutions being faster than that of Pr(III).The opposite order of the two rates for Pr(Ⅲ) and Nd(Ⅲ) result in their kinetic "push and pull" separation.In contrast,the β_(Pr)/Nd value in traditional thermodynamic separation reported in previous literatures is only around 5 or even less,even though using the same extractant [A336][NO3] and DTPA but by previously adding DTPA into the aqueous feed solutions for pre-complexing of Pr(Ⅲ) and Nd(Ⅲ).Various effects from the pH and addition amount of DTPA aqueous solutions,LiNO_3 concentrations in initial aqueous feed solutions,the initial concentration ratios of Pr(Ⅲ) to Nd(Ⅲ) ions,the initial pH of aqueous feed solutions,and the concentrations of [A336][NO_3] in organic phases,on the kinetic separatiot of Pr(Ⅲ) and Nd(Ⅲ) are discussed.The present work highlights a promising approach for separation of rare earths or other targets with extreme similarity in physicochemical properties.     

Comparative studies on Y(III) and Dy(III) extraction from hydrochloric and nitric acids by Cyanex 572 as a novel extractant

Extraction of Y(III) and Dy(III) from hydrochloric and nitric acids by Cy-572 in kerosene was studied. The factors affecting the extraction were separately investigated. The stoichiometry of the extracted species was deduced on the basis of slope analysis method. Evaluation of extraction equilibrium and stripping investigation was studied as well as saponification effect of Cy-572. The composition of the extracted metal species in the organic phase was found to be $\overline{{[\text{MA}}_3·{\left(\text{HA}\right)}_3]}$ for Y(III) or Dy(III) in both media. 1.0 mol/L HCl is the best stripping agent for each metal ion from the studied acidic media in one step. Saponified Cy-572 does not exhibit any selectivity towards the extraction of Y(III) or Dy(III) from both HCl and HNO₃ solutions. Based on the obtained results, the data were compared and the separation feasibility between lanthanides and Y(III) in the two media was discussed.     

Extraction and separation of heavy rare earths from chloride medium by α-aminophosphonic acid HEHAPP

The extraction and separation of heavy rare earths(REs) using newly synthesized a-aminophosphonic acid extractant 2-ethylhexyl-3-(2-ethylhexylamino)pentan-3-yl phosphonic acid(HEHAPP, HA) in nheptane were investigated from chloride medium. The extraction stoichiometries of lanthanum, gadolinium, yttrium and lutetium are determined to be REA3 by the slope analysis method. The favorable separation factors of adjacent heavy REs(Ⅲ),i.e. β_(Y/Ho), β_(Er/Y),β_(Tm/Er),β_(Yb/Tm) and β_(Lu/Yb), are determined to be1.87,1.36, 3.21,3.22 and 1.93, respectively, when extracted from a binary system at proper condition. The loading capacities of HA for Ho, Er, Yb and Lu increase in the order Ho Er Yb Lu with the values being 0.201, 0.205, 0.216 and 0.229 mol/L, respectively. So HA would be a potential extractant for the separation of heavy REs(Ⅲ). Among inorganic acids such as H_2 SO_4, HNO_3 and HCl, HCl is tested to be the most effective stripping agent.     

Adsorption of Ce（ Ⅳ ） Anionic Nitrato Complexes onto Anion Exchangers and Its Application for Ce （Ⅳ） Separation from Rare Earths （ Ⅲ ）

Ceriumis one of the cheapest[1]and most abun-dant rare earths (RE) .However ,high purityis usual-ly required for its utilization in industry , where it isusedfor sulfur control insteels ,pyrophoric alloys ,ce-ramic ,catalyst support ,polishing powders ,etc .In its minerals ,as well as in the spent nuclearfuel ,ceriumis accompanied by other RE.They basi-cally exist in solution as stable RE(Ⅲ) species ,which makes their mutual separation rather difficult .In contrast to other RE, Ce(Ⅲ) can…     

Synergistic extraction of rare earth by mixtures of 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester and di-（2-ethylhexyl） phosphoric acid from sulfuric acid medium

The extraction of Nd^3＋ and Sm^3＋, including the extraction and stripping capability as well as the separation effect of Nd^3＋ or Sm^3＋, from a sulfuric acid medium, by mixtures of di-（2-ethylhexyl） phosphoric acid （HDEHP, H2A2（0）） and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester （HEH/EHP, H2L2（0）） were studied. The distribution ratios and synergistic coefficients of Nd^3＋ and Sm^3＋ in different acidities were also determined. A synergistic extractive effect was found when HDEHP and HEH/EHP were used as mixed extractants for Sm^3＋ or Nd^3＋. The chemical compositions of the extracted complex were determined as Nd.（HA2）2-HL2 and Sm.（HA2）2-HL2. The extraction equilibrium constants, enthalpy change, and entropy change of the extraction reaction were also determined.     

Solvent extraction of Ce(III) and Pr(III) with P507 using SiC foam as a static mixer

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 K_La 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.     

Extraction of chromium(III) from sodium chloride solutions by means of carboxylic acids

Studies of Cr(III) extraction with carboxylic acids showed that the extraction process takes place at a pH of the aqueous phase ranging from 4 to 5. It was shown that sodium chloride is active with respect to chromium(III) as a salting-out agent. For extraction of Cr(III) with hexanoic acid it was shown that in the organic phase trinuclear complexes of the [Cr(OH)R₂·HR]₃ formula are formed.     

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.     

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%.