Gel formation in extraction of terbium by bis(2-ethylhexyl) hydrogen phosphate

Yurtov, E. V.; Мурашова, Н. М.; Datsenko, A. M.

doi:10.1134/s0036023606040280

Cited by 11 publications

(6 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2). Indeed, in the Pr(III) extraction, a gel forms in the interfacial layer, whereas in the Er(III) extraction, interface species have quasi crystalline properties and are more dense [11][12][13].…”

Section: Resultsmentioning

confidence: 99%

State of the dynamic interfacial layer of an extraction system and the attenuation coefficient of surface waves

2013

View full text Add to dashboard Cite

The possibility of using the method of surface waves for solving physicochemical problems was previously demonstrated by Noskov et al. [1], who, having stud ied the adsorption of surfactants at the aqueous solu tion-air interface, determined the kinetic characteris tics and sizes of micelles. We failed to find similar stud ies as applied to systems of two immiscible liquids, although Barik et al. [2] and Boev and Yasnitskaya [3] showed that the attenuation coefficient depends on the frequency, the surface tension, and the properties of the liquids, namely, viscosity and density. Such dependence suggests that this parameter can be used for identifying structural changes in the dynamic interfacial layer, which emerges in the case of the redistribution of chemically reactive components between phases of a heterogeneous liquid system [4].The purpose of this work was to prove the applica bility of the attenuation coefficient of surface waves generated at the liquid-liquid interface for detecting changes in the state of the dynamic interfacial layer.The novelty of this work consists in the fact that it for the first time presents data on the possibility of using the attenuation coefficient for determining changes in the state of the interface and the surface layers of a heterogeneous liquid system. EXPERIMENTALThe objects of investigation were the heteroge neous systems water-aqueous solution of erbium or praseodymium chloride (pH 5.3)-0.05 M di (2 eth ylhexyl)phosphoric acid (D2EHPA) solution in hep tane. All the reagents were chemically pure. D2EHPA was purified according to a published procedure [5].The experiment was performed on a setup that included a soundproof chamber in which a glass cell (Petri dish) with a system to be studied, a sensor, and a vibrator were placed.The sensor was a highly sensitive piezoceramic head with a 7 cm long rigidly attached glass thread 0.05 cm in diameter, the 0.5 cm long end portion of which was bent at a right angle. The sensor was con nected with a coaxial cable to a selective microvoltme ter, the output signal of which entered a storage oscil loscope and a frequency meter.The vibrator was a high frequency electrodynamic head with a 4.3 cm long stainless steel rod 0.05 cm in diameter, which was rigidly attached to the center of the diffuser. To the end of the rod, a vibrating element was fastened. The vibrating element was made of tet rafluoroethylene in the shape of a regular trigonal prism with a height of 0.5 cm and a base of 1.1 × 0.3 cm, one of the lateral edges of which faced the interface. The vibrator was connected to a low frequency signal generator. The measurements were made within the frequency range 2-14 kHz. Within this range, no eigenfrequencies of the sensor and the vibrator were detected.The experiment was performed as follows. Initially, the water-solvent heterogeneous system was studied. In a cylindrical glass cell 9.7 cm in diameter with a wall height of 1.5 cm, 20 mL distilled water was placed. The horizontal part of the glass thread at the beginning of the ...

show abstract

Section: Resultsmentioning

confidence: 99%

State of the dynamic interfacial layer of an extraction system and the attenuation coefficient of surface waves

2013

View full text Add to dashboard Cite

show abstract

“…However, dispersed structures such as gels, liquid crystals, amorphous and crystalline precipitates establish in the bulk of both aqueous and organic phases or at the interface at high loading of the organic phase, which affect the distribution, separation factors, the rates of extraction and phase separation [27,28]. To prevent the above disadvantageous effects, the mechanism for the formation of the dispersed structures should be studied.…”

Section: Introductionmentioning

confidence: 99%

Characterization of reversed micelles formed in solvent extraction of thorium(IV) by bis(2-ethylhexyl) phosphoric acid. Transforming from rodlike to wormlike morphology

et al. 2016

View full text Add to dashboard Cite

The reversed micelles formed in solvent extraction of thorium(IV) by bis(2-ethylhexyl) phosphoric acid (HDEHP) in -heptane were studied. IR spectra, dynamic/static light scattering and zero shear viscosity measurements indicated that thorium complexes formed rodlike reversed micelles, and both the size of aggregates and the viscosity of the organic phase increased with the increasing loadage of thorium(IV). The entanglement of reversed micelles resulted in their transformation to wormlike reversed micelles, inducing the very high viscosity of the organic phase. The structural composition of thorium complexes was proposed to be Th(DEHP) 3 (NO 3 ) according to the results of log-log plot and job method analysis.Furthermore, molecular modeling was employed to clarify the structures of reversed micelles as well as the state of water inside. It was found that the complexes linked together via hydrogen bonding and van der Waals forces and that the existence of NO − 3 and H 2 O improved the stability of reversed micelles.

show abstract

“…Under extremely high trivalent metal loading conditions, insoluble gels will form as an interphase between the organic and aqueous phases resulting in loss of system flow properties. [65][66] The formation of a gel interphase can occur under equilibrium conditions, or temporarily under high mass transfer conditions. [65] A detailed physical description of the process through which interphase species form is in Kizim et al [67] Previous work on the formation of gel interphase indicate that this behavior is dependent on HA concentration, aqueous acidity, and aqueous metal concentration.…”

Section: Introductionmentioning

confidence: 99%

“…[65][66] The formation of a gel interphase can occur under equilibrium conditions, or temporarily under high mass transfer conditions. [65] A detailed physical description of the process through which interphase species form is in Kizim et al [67] Previous work on the formation of gel interphase indicate that this behavior is dependent on HA concentration, aqueous acidity, and aqueous metal concentration. [66] Targeted synthesis to understand other high aggregation species has produced the following compounds: LnA(NO 3 HA) 2 , [68] LnA 2 (ClHA), [68] Ln(A) 3 , [69][70] and Ln(Acetate) b (A) 2-b .…”

Section: Introductionmentioning

confidence: 99%

Equilibrium Speciation of Select Lanthanides in the Presence of Acidic Ligands in Homo- and Heterogeneous Solutions

Robinson

2011

View full text Add to dashboard Cite

This dissertation explores lanthanide speciation in liquid solution systems related to separation schemes involving the acidic ligands: bis(2-ethylhexyl) phosphoric acid (HDEHP), lactate, and 8-hydroxyquinoline. Equilibrium speciation of neodymium (Nd 3+ ), sodium (Na + ), HDEHP, water, and lactate in the TALSPEAK liquid-liquid extraction system was explored under varied Nd 3+ loading of HDEHP in the organic phase and through extraction from aqueous HCl and lactate media. System speciation was probed through vapor pressure osmometry, visible and Fourier Transform Infrared (FTIR) spectroscopy, 22 Na and 13 C labeled lactate radiotracer distribution measurements, Karl Fischer titrations, and equilibrium pH measurements. Distribution of Nd 3+ , Na + , lactate, and equilibrium pH were modeled using the SXLSQI software to obtain logK Nd and logK Na extraction constants under selected conditions. Results showed that high Nd 3+ loading of the HDEHP led to Nd 3+ speciation that departs from the ion exchange mechanism and includes formation of highly aggregated, polynuclear [NdLactate(DEHP) 2 ] x ;(with x > 1). By substituting lanthanum (La 3+ ) for Nd 3+ in this system, NMR scoping experiments using 23 Na, 31 P nuclei and 13 C labeled lactate were performed. Results indicated that this technique is sensitive to changes in system speciation, and that further experiments are warranted. In a homogeneous system representing the TALSPEAK aqueous phase, Lactate protonation behavior at various temperatures was characterized using a combination of iv potentiometric titration and modeling with the Hyperquad computer program. The temperature dependent deprotonation behavior of lactate showed little change with temperature at 2.0 M NaCl ionic strength.Cloud point extraction is a non-traditional separation technique that starts with a homogeneous phase that becomes heterogeneous by the micellization of surfactants through the increase of temperature. To better understand the behavior of europium (Eu 3+ ) and 8hydroxyquinoline under cloud point extraction conditions, potentiometric and spectrophotometric titrations coupled with modeling with Hyperquad and SQUAD computer programs were performed to assess europium (Eu 3+ ) and 8-hydroxyquinoline speciation.Experiments in both water and a 1wt% Triton X-114/water mixed solvent were compared to understand the effect of Triton X-114 on the system speciation. Results indicated that increased solvation of 8-hydroxyquinoline by the mixed solvent lead to more stable complexes involving 8hydroxyquinoline than in water, whereas competition between hydroxide and Triton X-114 for Eu 3+ led to lower stability hydrolysis complexes in the mixed solvent than in water.Lanthanide speciation is challenging due to the trivalent oxidation state that leads to multiple ligand complexes, including some mixed complexes. The complexity of the system demands well-designed and precise experiments that capture the nuances of the chemistry. This work increased the understanding of lanthanide speciation in the explo...

show abstract

Gel formation in extraction of terbium by bis(2-ethylhexyl) hydrogen phosphate

Cited by 11 publications

References 2 publications

State of the dynamic interfacial layer of an extraction system and the attenuation coefficient of surface waves

State of the dynamic interfacial layer of an extraction system and the attenuation coefficient of surface waves

Characterization of reversed micelles formed in solvent extraction of thorium(IV) by bis(2-ethylhexyl) phosphoric acid. Transforming from rodlike to wormlike morphology

Equilibrium Speciation of Select Lanthanides in the Presence of Acidic Ligands in Homo- and Heterogeneous Solutions

Contact Info

Product

Resources

About