Extraction Of Europium Research Articles

Removal of europium by green tea mediated zero valent iron nanoparticles

Europium is the rarest and one of the least abundant rare-earth elements in the world. There are many chemical methods for this extraction of europium, among them application of green synthesized nanomaterial zero-valent iron (nZVI) is a very propitious, inexpensive, and eco-friendly technique. The nZVI nanoparticle was synthesized using green tea extract and applied for the reductive extraction of europium [Eu (III)] from an aqueous solution. The presence of polyphenolic compounds in the green tea extract was used as a reducing agent for the efficient formation of stabilized GT-nZVI. The green synthesized GT-nZVI nanoparticle was characterized by XRD and FTIR techniques. The performance evaluation of GT-NZVI for Eu removal was carried out under batch experiments with various experimental conditions such as, change in pH, initial Eu concentration, reaction time, and temperature. Almost 83 % of Eu was removed at pH 5 while only 65 % at pH 4 at 100 mg/L of initial Eu concentrations. GT-nZVI also shows better removal efficiency at high temperatures. According to the Langmuir isotherm model, GT-nZVI nanoparticles showed an adsorption capacity of 217.39 mg/g. The green synthesized nanoparticles also have good reusability capacity up to 4 consecutive adsorption cycles.

Recovery of critical metals from carbonatite-type mineral wastes: Geochemical modeling investigation of (bio)hydrometallurgical leaching of REEs

Abstract Rare earth elements (REEs) are typically found in low concentrations within natural rocks that make up mine tailings, such as carbonates in association with silicates within carbonatite igneous rocks, so it is of interest to develop (bio)hydrometallurgical ways to liberate them from the silicate matrix. This work investigated, through geochemical modeling, the extraction of europium and ytterbium carbonates from rocks containing one of four silicates (chrysotile, forsterite, montmorillonite, and phlogopite) via chemical (mineral acid) or biological (organic acid) leaching. The results indicated conditions that led to either congruent or incongruent dissolution of the mineral phases and the formation of transient mineral phases. Chemical leaching models suggest that REE carbonates are recoverable in one-step leaching from forsterite and chrysotile rocks, while they are recoverable in a secondary leaching step from montmorillonite and phlogopite rocks. Gibbsite as a transient phase is shown to complicate REE recovery, potentially requiring reactive extraction. REEs have the potential to be recovered from silicate rocks via chemoorganotrophic bioleaching, but the process configuration would differ depending on the predominant minerals that make up the rock, and the type of REE present in it.

Solvent extraction of europium(III) trifluoromethanesulfonate into nitrobenzene by using [2.2.2]paracyclophane – Experimental and theoretical study

The extraction constant corresponding to the equilibrium Eu3+(aq) + 3A-(aq) + 1(nb) ⇌ 1 Eu3+(nb) + 3A–(nb) occurring in the two-phase water–nitrobenzene system (A-=CF3SO3-; 1 = [2.2.2]paracyclophane; aq = aqueous phase, nb = nitrobenzene phase) was determined as logKex(Eu3+,3A–) = -5.7 ± 0.1. Further, the stability constant of the 1 Eu3+ complex in nitrobenzene saturated with water was calculated as log Knb(1 Eu3+) = 7.4 ± 0.1. Finally, by using quantum chemical calculations, the most probable conformation of the cationic complex species 1 Eu3+ was derived. In the resulting complex, the “central” cation Eu3+, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is bound to all three benzene rings of [2.2.2]paracyclophane via cation-π interaction.

Comparative uptake studies on trivalent f-cations from acidic feeds using two extraction chromatography resins containing a diglycolamide in molecular diluent and ionic liquid

Low molecular weight diglycolamide (DGA) extractants were tested for the extraction of europium(III) and americium(III) from nitric acid solutions in n-dodecane, a molecular diluent and 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide (C4mim⋅NTf2), a room temperature ionic liquid, as the diluents. N,N,N’,N’-tetra-n-butyl diglycolamide (TBDGA) was selected for extraction chromatography (XC) studies involving Eu(III) and Am(III). While the TBDGA resin containing n-dodecane gave reasonably high Kd values, that containing the ionic liquid showed higher Eu(III) uptake values. Compared to Eu(III), Am(III) was extracted by the resins to a lower extent. The loaded Eu(III) was back extracted from the resin using 0.05 M EDTA solutions in a buffered medium containing 1 M guanidine carbonate. Reusability studies indicated that, while the ionic liquid-based resin can be conveniently recycled five times with very marginal decrease in the percentage extraction values, there was a sharp decrease in the percent extraction after three cycles with the n-dodecane-based resin. The uptake data was fitted into different isotherm models and the results conformed to the Langmuir model. Based on the batch uptake studies, columns were prepared and the breakthrough as well as elution profiles were obtained. The elution profiles were found to be sharp without any significant tailing.

Optimization of Green Technique Develop for Europium (III) Extraction by using Phosphonium Ionic Liquid and Central Composite Design Approach

Rare earth compounds widely used in industrial applications and new processes with green solvents are appropriate for recovering these elements. In this study, the ionic liquid application development was investigated to extract europium ions in single and binary systems. A green procedure for europium (III) extraction from aqueous chloride solution was investigated using phosphonium ionic liquid Cyphos IL 104. Comparative conditions were investigated for analyzing better results with the presence of organic extractant such as Cyanex272, D2EHPA in the batch experiments. The experiment design was carried out based on the central composite design principles to analyze the relationships between the responses and the significant parameters. The obtained data revealed that the quadratic equation has good desirability to predict the extraction percentage. Investigation of the extraction process showed that the ionic liquid Cyphos IL104 has selective power in the extraction of europium and the efficiency is higher than the organophosphorus extractants. Accordingly, optimum conditions for maximum removal of europium ions were obtained equal to 5.5, 1, 16 min, and 0.008 M for feed acidity (pH), phase ratio, time, Cyphos IL 104 concentration. Examination of binary systems of rare earth elements showed that ionic liquid had positive and negative effects on the separation factor. The high efficiency of ionic liquid in the reuse condition indicated that the system is appropriate from an economic perspective.

Effect of diluent on the extraction of europium(iii) and americium(iii) with N,N,N',N'-tetraoctyl diglycolamide (TODGA).

Solvent extraction of Eu3+ and Am3+via N,N,N′,N'-tetraoctyl diglycolamide (TODGA) dissolved in different molecular diluents was studied. The diluent types used in this work were primary and secondary alcohols, secondary ketones and alkanes. Effects of concentration of extracting agent, temperature, diluent type and its carbon chain length on the extractions were determined. Distribution ratios of Eu3+ and Am3+ showed high dependence on the diluent type as well as the carbon chain length within the same type of diluent. The highest distribution ratios for both Eu3+ and Am3+ as well as the separation factors of Eu3+ over Am3+ were observed in the alkane diluents. Unexpectedly high distribution ratios for Eu3+ and Am3+ were observed in polar diluents with 5 carbon atoms in the chain, clearly standing out against the general trends. It was found that Eu3+ and Am3+ extraction via TODGA is enthalpy driven in all the studied diluents and that extraction is more exothermic in alkane diluents. Analysis of the stoichiometry of the extracted complexes shows that the average ligand number of TODGA molecules in the extracted complex is lower for Am3+ compared to Eu3+ except for with alkane diluents.

Study of Sorption of Eu(III) from Various Media on TODGA-Сontaining Sorbent AXIONIT MND40T

The dependences of the static capacity (SC) of the AXIONIT MND40T sorbent based on tetraoctyldiglycolamide (TODGA) for Eu(III) on the concentration of HNO3, HCl, H2SO4, and HClO4 were determined. The SC increases with increasing acid concentration. In the concentration range 2–4 mol dm–3 SC of AXIONIT MND40T for europium in nitric, hydrochloric, and perchloric acid solutions is approximately the same, whereas in sulfuric acid solutions it is much lower. The maximum capacity and adsorption constant (Kad) in different media were calculated from the results of processing of the isotherms of europium sorption by AXIONIT MND40T. The mechanism for the extraction of europium from nitric acid solutions by AXIONIT MND40T is proposed based on the IR spectroscopy data.

Solvent extraction of europium(III) from technogenic solutions with the use of surfactants

Objectives. The extraction and separation of rare-earth metals is a complicated process that requires a multidisciplinary and detailed investigation. Liquid-liquid extraction with the use of surfactant, along with the thermodynamic analysis of the parameters is considered a promising approach. The extraction and separation of rare-earth metals from low-concentration solutions represents an attractive research opportunity. The extraction of europium(III) from nitric acid solutions in the form of dodecyl sulfates has been experimentally studied. This work focuses on the study of fundamental and alternative sources of rare-earth metals and their extraction and separation.Methods. The extraction was performed on a top drive ES-8300 D equipment for 30 min at about 700 rpm. Infrared spectroscopy (Nicolet 6700 spectrometer) was used to determine the type of salts extracted into the organic phase. Extraction was studied in solutions with single cations and with a combination of the target element and interfering cations. For the latter, the concentrations of extracted elements in the aqueous phase were determined by optical emission spectroscopy with inductively coupled plasma on an ICPE-9000 (Shimadzu) spectrometer. The spectrometer was calibrated using standard samples for ICP CertiPUR (Merck).Results. The dependence of the distribution and separation coefficients of rare-earth metals during extraction on the pH value of the aqueous phase at equilibrium was investigated. Moreover, the form in which the elements are extracted was analyzed based on thermodynamic parameters. The minimum concentration of the target component in the aqueous phase was observed at pH 4.0. In general, the dependence of the distribution coefficient on the pH value of the medium is poorly expressed over the entire range of the pH range of the water phase. Based on the spectra of spent and pure isooctyl alcohol, it was concluded that europium dodecyl sulfates are extracted into the organic phase as Eu(C12H25OSO3) 3 solvates.Conclusions. The extraction of europium(III) from nitric acid solutions in the form of dodecyl sulfates was demonstrated. The advantages of the proposed method are the possibility of selective extraction of the target component from dilute solutions and the use of an easily available surfactant (sodium dodecyl sulfate). The efficiency of extraction of europium dodecyl sulfates was maximal in the pH range from 2.0 to 7.5, which reflects a weak dependence on the acidity of the aqueous phase. In addition, in the highly alkaline pH region, the extraction efficiency is reduced.

Liquid-liquid extraction of europium(III) in an alkyl ammonium based ionic liquid containing diglycolamic acid

A strongly hydrophobic alkylammonium ionic liquid: methyltrioctylammonium bis (trifluoromethanesulfonyl) imide ([N1888][NTf2]) was explored as diluent for the extraction of europium (III) from nitric acid medium using bis(2-ethylhexyl) diglycolamic acid (HDEHDGA) as extractant. The extraction behavior of europium(III) in HDEHDGA/[N1888][NTf2] was investigated as a function of various extraction parameters such as pH, [HDEHDGA]IL, temperature, concentrations of europium(III) ion and nitrate ion in the aqueous phase. The metal-solvate stoichiometry was determined from the slope analysis of extraction and the data suggested the involvement of two extractant molecules for extraction. The extraction trend obtained in HDEHDGA was compared with other acidic extractants namely bis(2-ethylhexyl) phosphoric acid (D2EHPA) and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) present in [N1888][NTf2]. The diluent property of [N1888][NTf2] was also compared with other ionic liquid diluents as well as molecular diluents. The stripping study of europium(III) and the reusability of the ionic liquid phase were also ascertained.

Continuous Extraction of Europium(III) by Ionic Liquid in the Rotating Disk Column with an Asymmetrical Structure Aimed at the Evaluation of Reactive Mass Transfer.

In this study, the features of the solvent extraction technique were investigated to explore the potential of ionic liquid for extracting Eu(III) from aqueous solution. The transport process between the aqueous and organic phase was carried out in the rotating disk column with an asymmetrical structure and a continuous mode of operation. The utilization of Cyphos IL 104 as an ionic liquid in comparison with Cyanex272 extractant was evaluated for the extraction abilities in the recovering of Eu(III) under different conditions, including agitation speed, inlet aqueous, and solvent phase velocities. The degree of extraction and the mass-transfer rate were best when the agitation speed and the superficial velocities of aqueous and solvent phases were adjusted to 690 rpm, 0.831 mm/s, and 1.385 mm/s, respectively. The better efficiency was achieved using the ionic liquid with 0.02 mol/L concentration, 96.52% Eu(III) extraction in comparison to the same condition without the presence of ionic liquids with Cyanex272 (0.5 mol/L, 99.66%). With the analysis of the data, it was noted that the increase in the operating parameters has a positive influence on the holdup, degree of extraction, and mass-transfer rates. The percentage increase equal to 33.57% for overall mass-transfer coefficients was obtained with the increment of mixing in the column. The results showed that the mass transfer is associated with reactive resistance. The previous correlation did not explain the behavior of the system correctly in the reactive mode. Finally, the empirical models using the Sherwood number were developed to correlate the mass-transfer coefficient.

Synergic extraction of europium(III) in hydrophobic ammonium ionic liquid containing neutral and acidic extractants

The extraction behavior of europium(III) in a binary solution containing octylphenyl(N,N-diisobutylcarbamoylmethyl) phosphine oxide (CMPO) and bis-2-(2-ethylhexyl)phosphoric acid (D2EHPA) in ionic liquid medium has been reported in this paper. Methyltrioctylammonium bis(trifluoromethanesulfonyl)imide ([N1888][NTf2]) was used as ionic liquid diluent in the present study. The extraction of europium(III) was investigated as a function of various parameters, such as aqueous phase acidity, extractant concentration, equilibration time and the experimental temperature. The extraction of Eu(III) in CMPO in [N1888][NTf2] and D2EHPA in [N1888][NTf2] was studied to compare the extraction data with those obtained in a binary solution. The stripping behavior of Eu(III) from the loaded ionic liquid phase was also investigated.

INFLUENCE OF BACKGROUND ELECTROLYTE AND SURFACE-ACTIVE SUBSTANCES ON EFFICIENCY OF ELECTRO-FLOTATION EXTRACTION OF HARDLY SOLUBLE EUROPIUM COMPOUNDS

Europium and its compounds are widely used in high-tech processes of nuclear and hydrogen energy, electronics, medicine and other fields. In this work, the regularities of electroflotation extraction of hardly soluble europium compounds from model systems were obtained and analyzed. The aim of the work is to obtain data on the process of electroflotation extraction of hardly soluble europium (III) compounds from model systems with background electrolyte and the addition of surface-active substances, establishing optimal conditions for efficient extraction of hardly soluble europium (III) compounds. The research was conducted at room temperature (20 ± 2 °C) in a non- current electric flotator of periodic action, which is made in the form of a vertical column. The cross-sectional area of the electric flotator is 10 cm2, the volume of the treated solution is 500 ml, the height of the apparatus is 800 mm, and the sampling valve is located at a height of 40 mm from the electrode unit. The electrode unit consists of an insoluble anode made of ORTA (titanium with ruthenium oxide coating) and of a cathode made of stainless steel mesh (cell size 0.5 × 0.4 mm, wire thickness 0.3 mm). The mass concentration of europium (III) was determined by a mass-spectrometer with inductively coupled plasma of Termo Scientific brand. Determination of particle size and particle size distribution, surface charge of particles of the dispersed phase (ξ) were carried out using a Photocor Compact-Z laser particle analyzer. The efficiency of the process of extracting hardly soluble compounds of Eu3+ was evaluated by the degree of extraction α (%). The objects of study are colloid-dispersed systems of poorly soluble compounds of europium (III) in aqueous solutions in the presence of surface-active substances of various nature and background electrolytes. The initial aqueous solution contains: СEu3+ - 0.1 g/l, Cbackground electrolyte - 1 g/l, background salts: NaCl, NaNO3, Na2SO4; Csas - 5 mg/l. It has been shown that for each type of solution the efficiency of the electroflotation process is achieved at certain pH. It is established that the optimal conditions for the extraction of europium (III) compounds are: volume current density, Jv = 0.4 A/l; process duration 10 min. For nitrate background the degree of extraction is maximum at pH 10 - 11 and at the presence of an anionic surfactant additive in the solution (Оxy surfactant A1218). When extracting europium (III) compounds from a system with a sulphate background the best results were obtained at pH values of 8 and 10, as well as the addition of an anionic and, or cationic (Septa surfactant XEV70) surfactant. Chloride background showed the best conditions for the extraction of europium (III) at pH 7 with the addition of a non-ionic surfactant of PEO-1500 brand. The degree of extraction of europium is 98-99%.

The extraction of europium and americium by the nitrobenzene solution of dicarbollylcobaltate in the presence of some commercially available dioxadiamides

We investigated the extraction of microamounts of Eu3+ and Am3+ from aqueous nitric acid solutions using nitrobenzene solutions of hydrogen dicarbollylcobaltate (H+B−) in the presence of some commercially available dioxa alkyl diamides. The significant synergistic effect was found for some structures of ligand. We suppose that the complexes $${\text{HL}}^{ + }$$, $$\text{ML}^{{\text{3} + }}$$, $$\text{ML}_{\text{2}}^{{\text{3} + }}$$ and $${\text{ML}}_{ 3}^{ 3+ }$$ (M3+ = Eu3+, Am3+) are present in the equilibrium organic phase. Extraction and stability constants of these complex species in water-saturated nitrobenzene have been determined and discussed. Lithium ionophore I and lithium ionophore IV receptors for Eu3+ and Am3+ can be used as efficient extraction agents for nuclear waste treatment.

D2EHPA is a potential extractant for extraction of europium and samarium from chloride medium

Europium and samarium, the most valuable rare earth metals are broadly used in different areas such as fluorescent, medical materials and samarium-cobalt permanent magnet in the industrial community. Solvent extraction is an extensively applied separation process for collection of high purity rare earth metal ions. Due to the congruent physical and chemical properties of rare earth metal ions, the separation of specific elements from the mixture is ambiguous. In such places solvent extraction process is most efficient because of their ease in terms of the equipment and conditions associated with them. Solvent extraction, using di-2-ethylhexylphosphoric acid (D2EHPA) is the most frequently used industrial extractant for the extraction and separation of rare earth metal ions compared with other extractants. Present report deal with the studies on solvent extraction of europium (III) and samarium (III) from chloride medium using D2EHPA diluted in kerosene. Utmost extraction such as 96.65% Eu(III) and 86% Sm(III) happened at 0.001 mol/L hydrogen ion concentration in the aqueous medium. 100% extraction of Eu (III) and Sm(III) has been noticed with 0.07 mol/L and 0.08 mol/L D2EHPA, respectively. The separation factors of Eu/Co and Sm/Co are 1844.44 and 1556, respectively.

Homogeneous liquid–liquid extraction of europium from aqueous solution with ionic liquids

Comparing with the traditionally immiscible two-phase extraction, the homogeneous liquid–liquid extraction technique shows potential in industrial separation engineering due to nearly infinite contact interface. In this work the ionic liquid (IL) compounds such as N-(carboxymethyl)-N,N-dimethylethanaminium bis-trifluoromethane-sulfonimide ([DHbet][Tf2N]) and N-(carboxyethyl)-trimethylammonium bistrifluoromethane-sulfonimide ([THbet][Tf2N]) were synthesized. The homogeneous extraction behaviors of europium with two ILs were studied as functions of solution pH, ionic strength, contact time, and initial europium concentration. The results indicated that both homogeneous extractions were dependent on pH and independent on ionic strength. The extraction capacities for [DHbet][Tf2N] and [THbet][Tf2N] were 3.29 mmol/L and 3.16 mmol/L, respectively. ILs could be recovered using 1.0 M hydrochloric acid. The mole-ratio method indicated the formation of a mononuclear complex between the europium ion and IL. Total europium extraction efficiencies of more than 91% for [DHbet][Tf2N] and more than 90% for [THbet][Tf2N] were obtained by quadruple-stage countercurrent extraction. The result proves the feasibility of the homogeneous liquid–liquid extraction technique as an alternative option for europium separation from aquatic solution.

High-capacity extraction chromatographic materials based on polysulfone microcapsules for the separation and preconcentration of lanthanides from aqueous solution

Extractant-loaded polysulfone (PS) capsules suitable for the separation and preconcentration of rare earth ions from acidic media have been prepared and characterized. Specifically, PS macro- and microcapsules have been impregnated with bis(2-ethylhexyl)phosphoric acid (HDEHP), and their performance in the extraction of europium (Eu3+) from nitric acid solution evaluated. The HDEHP-loaded microcapsules were found to exhibit sorption efficiency superior to those of analogous macrocapsules. Comparison to a conventional (i.e., commercial) extraction chromatographic (EXC) material (Ln•Resin), comprising HDEHP-loaded beads of poly(methyl methacrylate) (PMMA) of comparable size (50–100 µm), showed that the capacity of the HDEHP-loaded microcapsules for europium is ca. 2.5-fold greater than that of the conventional material. This larger capacity is the apparent result of both the higher extractant loading achievable with the microcapsules and an unexpected change in the complexation stoichiometry of europium by HDEHP upon extractant encapsulation. The microcapsule-based sorbent equaled or exceeded the performance of the commercial EXC material in other respects as well, most notably uptake kinetics and column efficiency, making it a promising alternative to established EXC resins.

Synergism in the Solvent Extraction of Europium(III) with Thenoyltrifluoroacetone and CMPO in Methylimidazolium Ionic Liquids

The solvent extraction of Eu(III) from an aqueous chloride phase into hydrophobic ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides ([C1Cnim+][Tf2N−], n = 4, 6, 8 and 10), by β-diketone 2-thenoyltrifluoroacetone (HTTA) alone and in combination with N,N-diisobutyl-2-(octylphenylphosphoryl)acetamide (CMPO) was investigated. The interaction between the two extractants (acidic/neutral) in deuterochloroform has been studied by 1H, 13C, 19F and 31P NMR spectra and NOESY experiments. 1H and 19F Q-NMR analytical techniques were also applied for determination of [C1C4im+] and [Tf2N−] entities transferred into the aqueous phase. Eu(III) was efficiently extracted by HTTA/[C1Cnim+][Tf2N−] and HTTA/CMPO/[C1Cnim+][Tf2N−] systems but a relatively small synergism was established. A cation extraction mechanism was proposed via the log–log slope analysis method. The effect of the IL cation alkyl chain length on the extraction process was studied as well.

Solvent extraction and separation of europium (III) using a phosphonium ionic liquid and an organophosphorus extractant-A comparative study

In this paper, the comparative study between an ionic liquid (Cyphos IL 104) and an acidic extractant (D2EHPA) on europium (III) extraction from chloride medium has been reported. Effect of different extraction parameters such as equilibrium pH, extractant and metal ion concentration, salt, diluent and temperature effect has been investigated. Quantitative extraction of europium is achieved with 0.02 M Cyphos IL 104 and with 0.05 M D2EHPA and the loading capacity of 0.01 M Cyphos IL 104 is found to be 0.004 mol and that of 0.01 M D2EHPA is 0.0027 mol, respectively showing Cyphos IL 104 is a better extractant than D2EHPA. The extraction occurred via ion association mechanism for Cyphos IL 104 and cation exchange mechanism for D2EHPA. Stripping studies have been carried out using H2SO4 and HNO3. The effect of thermodynamic parameters, stability and reusability test of both the extractants studied in detail. The loss of extractants while stripping with nitric acid is negligible for both the extractants. The extraction behavior of europium is studied in presence of some transition elements. Separation studies of europium in presence of yttrium, cerium and lanthanum from a mixed solution indicate that D2EHPA is more suitable than Cyphos IL 104 for Y(III)/Eu(III) separation but the selectivity of Eu(III)/La(III) and Eu(III)/Ce(III) are better with Cyphos IL 104 than D2EHPA.

Segmented Microflows as a Tool for Optimization of Mass Transfer in Liquid−Liquid Extraction: Application at the Extraction of Europium(III) by a Malonamide

Segmented flows in T-junction glass microchannels are investigated as a tool for the study of liquid–liquid extraction kinetics of europium(III) by a malonamide. They allow to reach higher extracti...

Liquid–Liquid Equilibria in Multicomponent Systems Containing o-Xylene, Di-(2-ethylhexyl)phosphoric Acid, Water, Nitric Acid, and Europium (Gadolinium, Dysprosium) Nitrate at 298.15 K

The extraction of europium(III), dysprosium(III), and gadolinium(III) nitrates with di-(2-ethylhexyl) phosphoric acid (D2EHPA) in o-xylene was investigated at 298.15 K. Spectrophotometry and ICP-AES techniques were used for rare earth elements (REE) content determination. The content of nitric acid was measured by acid–base titration. The density of the equilibrium phases was determined. In the case of high content of rare earth element nitrates in the initial aqueous solutions, the third solid phase formation was observed during extraction experiments.