Liquid-liquid Extraction Studies Research Articles

Experimental and Theoretical Insight into the Ionic Liquid-Mediated Complexation of Trivalent Lanthanides with β-Diketone and Its Fluorinated Analogue.

A multitechnique approach with theoretical insights has been employed to understand the complexation of trivalent lanthanides with two β-diketones, viz. 1-phenyl-1,3-butanedione (L1) and 4,4,4-trifluoro-1-phenyl-1,3-butanedione (L2), in an ionic liquid (C6mim·NTf2). UV-vis spectral analysis of complexation using Nd3+ revealed the predominance of ML2+ and ML4- species. The stability constants for the PB complexes were higher (β2 ∼ 10.45 ± 0.05, β4 ∼ 15.51 ± 0.05) than those for the TPB (β2 ∼ 7.56 ± 0.05, β4 ∼ 13.19 ± 0.06). The photoluminescence titration using Eu3+ corroborated the same observations with slightly higher stability constants, probably due to the higher ionic potential of Eu3+. The more asymmetric (AL2ML4 ∼ 5.2) Eu-L2 complex was found to contain one water molecule in the primary coordination sphere of Eu3+ with more covalency of the Eu3+-O bond (Ω2L1 = 8.5 × 10-20, Ω4L1 = 1.3 × 10-20) compared to the less asymmetric Eu-L1 complex (AL1ML4 ∼ 3.5) with two water molecules having less Eu-O covalency (Judd-Offelt parameters: Ω2L1 = 7.3 × 10-20, Ω4L1 = 1.0 × 10-20). Liquid-liquid extraction studies involving Nd3+ and Eu3+ revealed the formation of the ML4- complex following an 'anion exchange' mechanism. The shift of the enol peak from 1176 to 1138 cm-1 on the complexation of the β-diketones with Eu3+ was confirmed from the FTIR spectra. 1H NMR titration of the β-diketones with La(NTf2)3 evidenced the participation of α-H of the β-diketones and protons at C2, C4, and C5 positions of the methylimidazolium ring. For the ML2 complex, 4 donor O atoms are suggested to coordinate to the trivalent lanthanides with bond distances of 2.3297-2.411 Å for La-O, 2.206-2.236 Å for Eu-O, and 2.217-2.268 Å for Nd-O, respectively, while for the ML4 complex, 8 donor O atoms were coordinated with bond lengths of 2.506-2.559 Å for La-O, 2.367-2.447 Å for Eu-O, and 2.408-2.476 Å for Nd-O. The Nd3+ ion was higher by 9.7 kcal·mol-1 than that of the La3+ ion for the 1:4 complex. The complexation energy with L1 was quite higher than that with L2 for both 1:2 and 1:4 complexes. Using cyclic voltammetry, the redox behavior of trivalent lanthanides Eu and Gd with β-diketonate in ionic liquid medium was probed and their redox energetic and kinetic parameters were determined.

Ligand structure and diluent nature in defining improved Am3+ and Cm3+ separation using diglycolamides: a combined solvent extraction and DFT study.

Separation of Am3+ and Cm3+ is one of the most challenging yet unavoidable steps in the back end of the nuclear cycle. Various ligands evaluated for Am/Cm separation have their own merits and demerits, and not a single ligand has been uniquely proposed for this purpose. In the present work, we evaluated N,N,N',N'-tetra-n-octyldiglycolamide (TODGA) vis-à-vis N,N,N',N'-tetra-2-ethylhexyldiglycolamide (T2EHDGA) in combination with a hydrophilic 2,6-bis(1,2,4-triazinyl)pyridine (SO3PhBTP) derivative in the aqueous phase for the separation of Am3+ and Cm3+ from nitric acid medium. The results showed that marginal selectivity for Am3+ over Cm3+ was observed with T2EHDGA in the presence of SO3PhBTP, which was attributed to the difference in the entropy change for their extraction from both the temperature-dependent liquid-liquid extraction and computational studies.

Switchable Metal-Ion Selectivity in Sulfur-Functionalised Pillar[5]arenes and Their Host-Guest Complexes.

Nucleophilic substitution of pertosylated pillar[5]arene (P-OTs) with commercially available sulfur containing nucleophiles (KSCN, KSAc, and thiophenol), yields a series of sulfur-functionalised pillar[5]arenes. DLS results and SEM images imply that these pillararene macrocycles self-assemble in acetonitrile solution, while X-ray crystallographic evidence suggests solvent-dependent assembly in the solid state. The nature of the sulfur substituents decorating the rim of the pillararene controls binding affinities towards organic guest encapsulations within the cavity and dictates metal-ion binding properties through the formation of favorable S-M2+ coordination bonds outside the cavity, as determined by 1 H NMR and fluorescence spectroscopic experiments. Addition of a dinitrile guest containing a bis-triazole benzene spacer (btn) induced formation of pseudorotaxane host-guest complexes. Fluorescence emission signals from these discrete macrocycles were significantly attenuated in the presence of either Hg2+ or Cu2+ in solution. Analogous titrations utilizing the corresponding pseudorotaxanes alter the binding selectivity and improve fluorescence sensing sensitivity. In addition, preliminary liquid-liquid extraction studies indicate that the macrocycles facilitate the transfer of Cu2+ from the aqueous to the organic phase in comparison to extraction without pillar[5]arene ligands.

High-efficient removal of tungsten from hafnium by TOA/XAD-7 extraction resin from HCl-HF media

ABSTRACT For removal of the natural isobar 182W interference prior to ultra-trace 182Hf determination by accelerator mass spectrometry, an extraction chromatographic method for separation of Hf from W has been developed by using a newly synthesized tri-n-octylamine (TOA)/XAD-7 resin as the stationary phase and HCl-HF media as the mobile phase. Based on the TOA liquid-liquid extraction studies in HF and HCl-HF solutions at wide concentration range, a maximum separation factor of 8.6 × 103 for W/Hf was obtained in 8 M HCl-0.05 M HF solution. Subsequently, the macroporous organic polymer-based TOA/XAD-7 resin was prepared by vacuum impregnation technique and its morphology, chemical structure and composition were characterized by SEM, EDS, FT-IR, TG-DSC, and EA. The results showed the self-assembly TOA/XAD-7 resin uptakes about 50% of extractant and keeps intact binding characteristic for metal ions. Hence, this resin was employed to investigate the column chromatographic behavior of Hf and W with variable parameters of sample loading and column bed dimensions. As a result, a high yield of more than 99% for Hf and high decontamination factor of 3.2 × 105 for W were achieved under the optimal column condition. The strategy developed provides a simple and efficient alternative to sample preparation for 182Hf measurement.

Study of liquid-liquid extraction and mass transfer process with solid particles in the inline teethed high shear mixer

The liquid–liquid extraction process with solid particles is of practical importance in the chemical industry. Consequently, the inline high shear mixer (HSM) was employed for the process intensification, and the effects of particle size and concentration, rotor revolution speeds, and rotor structural parameters were revealed in this work. Results indicate that increasing the rotor revolution speed remarkably promotes mass transfer performance. The extraction efficiency (E) and mass transfer coefficient (KLa) increase at low revolution speeds, yet mainly decrease with the elevated particle concentration. The larger particle size is more unfavorable to mass transfer. E and KLa first decline and then increase with the raised rotor outer diameter, and more rotor teeth correspond to higher E and KLa. Increasing the forward teeth angle promotes liquid–liquid extraction. The relationship between KLa and key parameters is established via machine learning algorithms with high accuracy for HSM design and optimization.

Highly Tunable 4-Phosphoryl Pyrazolone Receptors for Selective Rare-Earth Separation

Highly selective rare-earth separation has become increasingly important due to the indispensable role of these elements in various cutting-edge technologies including clean energy. However, the similar physicochemical properties of rare-earth elements (REEs) render their separation very challenging, and the development of new selective receptors for these elements is potentially of very considerable economic and environmental importance. Herein, we report the development of a series of 4-phosphoryl pyrazolone receptors for the selective separation of trivalent lanthanum, europium, and ytterbium as the representatives of light, middle, and heavy REEs, respectively. X-ray crystallography studies were employed to obtain solid-state structures across 11 of the resulting complexes, allowing comparative structure-function relationships to be probed, including the effect of lanthanide contraction that occurs along the series from lanthanum to europium to ytterbium and which potentially provides a basis for REE ion separation. In addition, the influence of ligand structure and lipophilicity on lanthanide binding and selectivity was systematically investigated via n-octanol/water distribution and liquid-liquid extraction (LLE) studies. Corresponding stoichiometry relationships between solid and solution states were well established using slope analyses. The results provide new insights into some fundamental lanthanide coordination chemistry from a separation perspective and establish 4-phosphoryl pyrazolone derivatives as potential practical extraction reagents for the selective separation of REEs in the future.

Efficient UO22+ extraction by DAPhens with asymmetric terminal groups: The molecular design, spectral titration, liquid-liquid extraction and mechanism study

• DAPhens with asymmetric terminal groups show high selectivity to UO 2 2+ . • Methyl groups in amide moieties facilitate DAPhens’ extraction performance. • Less distortion of DAPhens in complex benefits its superior affinity to UO 2 2+ . Four asymmetric alkyl-substituted DAPhens (N,N’-Dimethyl-N,N’-Dialkyl-2,9-Diamide-1,10-Phenanthrolines) were synthesized and investigated as selective ligands for UO 2 2+ . The results confirm that the ligands have higher affinity for uranyl comparing to the symmetric analogues with the same 1,10-phenanthroline core moiety. The slope analysis indicated the formation of 1:1 (metal/ligand) extracting complex, which was identified in the organic phase as [UO 2 (DAPhen-4)(NO 3 )] + complex ion by electrospray ionization mass spectrometry (ESI-MS). The superior affinity of the ligands for UO 2 2+ over Th 4+ and Eu 3+ in solvent extraction was consistent with the stability constants of their complexes in acetonitrile obtained by UV–Vis spectroscopic titrations. The observed better affinity of the asymmetric alkyl-substituted DAPhens could originate from the less steric hindrance of methyl in the terminal groups, which was confirmed by the relatively mild distortion of the ligand structure in the uranyl complex according to the crystal and molecular structure of the solid-state complex [UO 2 (DAPhen-1)(NO 3 )](NO 3 )·(CH 3 OH) as characterized by single crystal X-ray diffraction.

Liquid-Liquid Extraction of Copper (II) in a Synthetic Sample using a New Macrocyclic Compound

The paper describes the synthesis and characterization of a novel macrocyclic ligand. Liquid-liquid extraction studies were conducted to assess the extraction performance of the new macrobicyclic ligand towards copper ions. Selective extraction of heavy metals is highly demanded due to their toxicity and market significance. The results of the experimental studies to determine the best extraction conditions demonstrates pH=9 in the presence of 8.0 ppm of copper (II) in 10 mL with shaking time equal to 30 minutes at 25o C with using 0.05% reagent and chloroform as an organic solvent. The article studies the influence of various parameters on the extraction percentage such as; effect of pH, shaking time, type of solvent, temperature, ionic strength, the effect of concentration of metal ion and reagent. IR and HNMR have been used for the characterization of the new macrocyclic compound. Thermodynamic parameters have been calculated based on the experimental results at different temperatures with ΔH (39.91 kJ/ mol), ∆S (0.155 KJ/ mol. K), and ΔG (-6.28 KJ/ mol), which, indicates that the reaction is endothermic, randomness and spontaneous. This process has been used for extracting copper ions using atomic absorption spectrometer (AAS).

Effect of the Number of Donor Atoms in Calix[4]arene Derivatives for Selective Complexation and Extraction of Mercury(II) Cations, Thermodynamics and Extraction Studies

Water pollution due to gold mining activity is increasingly worrying. One way to selectively mitigate it is through the use of complexing agents such as calixarenes, which selectively functionalized with soft donor atoms such as sulphur, can selectively remove this pollutant, for the selective complexation of mercury from contaminated water, which was compared by conductimetry and liquid-liquid extraction studies with results that show that the derivative with the highest sulphur atoms is its structure which presents greater selectivity compared to the derivative with the lowest number of sulphur atoms, in both cases, they present very stable complexes.

Soluble Unimolecular Polymer Nanoparticles by Crosslinking of Polyethylenimine with Isophthalaldehyde

Polyethylenimine (PEI) is a cationic polymer widely used in non-viral gene delivery systems and other polymer technologies. PEI with a MW of 25 kD was cross-linked in aqueous solution by the aromatic di-aldehyde isophthalaldehyde. This di-aldehyde cross-links PEI by forming stable imines with the primary amine groups in branched PEI. Cross-linking was evaluated at different concentrations of PEI using NMR, dynamic light scattering (DLS or QELS) and solvent extraction. It is demonstrated that isophthalaldehyde was able to cross-link PEI intramolecularly in solution near physiological pH resulting in the formation of unimolecular cross-linked nanoparticles. Proton NMR was used to examine the cross-linking reaction <i>in-situ</i>. The aldehyde resonance of isophthalaldehyde became broadened as cross-linking occurred. Organic-aqueous liquid-liquid extraction studies supported both that the cross-linking was intramolecular and that the cross-linked structures were stable to hydrolysis in water at neutral pH. As cross-linking occurred, the percentage of isophthalaldehyde that could be extracted from the solution was reduced. The molecular radii and aggregation behavior was monitored by QELS. The particle size of the polymer molecules in solution decreased with increased cross-linking, indicating the intra-molecular cross-linking between the PEI branches. These results clearly show that cross-linking of PEI with isophthalaldehyde creates soluble unimolecular polymer nanoparticles. These materials hold promise for a variety of applications in biotechnology.

A microfluidic study of synergic liquid-liquid extraction of rare earth elements.

A microfluidic technique is coupled with X-ray fluorescence in order to investigate the origin of the so-called synergy effect observed in liquid-liquid extraction of rare earth elements (REEs) when special combinations of two extractants - one solvating and one ionic - are used. The setup enables kinetic studies by varying the two phases' contact time. The results obtained are compared with those obtained using a standard batch extraction method at identical contact time. We then determine variations of free energies of transfer for five rare earth elements present in a solution together with a non-target ion (Fe3+) at different pH. Analysis of the effect of temperature and of surface charge density of the coexisting cations allows separating electrostatic effects from complexation effects. We finally show that all non-linear (synergic) effects are quadratic in mole fraction. This demonstrates that in-plane mixing entropy of the bent extractant film, in the first nanometer around rare earth ions, is the determining term in the synergy effect. Surprisingly, even when the third phase is present, free energies of transfer could still be measured in the dilute phase, which is reported for the first time, to our knowledge. We hence show that the extractive power of the dense third phase is stronger than that of conventional reverse aggregates in equilibrium with excess water.

Extraction Properties of 4-Tetra(hydroxyphenyl)BTPhen in Liquid-Liquid Extraction Systems with Cyclohexanone/Octanol or in a Solid-Phase Extraction System

The extraction properties of tetra(4-hydroxyphenyl)BTPhen have been investigated. Liquid-liquid extraction studies in proposed SANEX diluents, cyclohexanone and 1-octanol, indicate that actinide-lanthanide separation is superior in cyclohexanone; whereas actinide-actinide separation is more efficient in 1-octanol. Immobilization of the ligand onto a silica support results in the separation factor becoming dependent upon the concentration of nitrate anions in the aqueous phase. The immobilized ligand was also applied to the extraction of transition metals, resulting in >70% uptake of all transition metals examined, in the presence of alkali and alkaline earth metals.

Study of Liquid-Liquid Extraction: Review

Study of Liquid-Liquid Extraction: Review

New organic extractant based on pyridazinone scaffold compounds: Liquid-liquid extraction study and DFT calculations

In this work, the synthesis of new organic compounds is reported based on pyridazin-3-(2H)-one compounds. The extraction efficiency of metal ions (e.g. Lead Pb(II), Cadmium Cd(II), Copper Cu(II) and Zinc Zn(II)) from aqueous solutions to organic solutions of those compounds was studied. Accordingly, the studied ligands show a remarkable affinity for the transition metals, especially Zn(II) with (Ligand L5), Cu(II) and Cd(II) with (Ligand L3) in the presence of withdrawing and donor electron group. Theoretical calculations DFT were made in order to get better insight into the geometry of the studied ligands.

Unfolding the complexation and extraction of Am3+ and Eu3+ using N-heterocyclic aromatic diphosphonic acids: a combined experimental and DFT study.

Phosphonate based ligands are well known for the extraction of 'f' block elements. Three N,O-donor N-heterocyclic aromatic diphosphonate ligands were evaluated in the present work for the extraction/separation studies of Am3+ and Eu3+. Complexation studies in aqueous medium using luminescence titration indicated the formation of anionic complexes in the case of Eu3+. Two phase liquid-liquid extraction studies were, therefore, carried out by employing Aliquat-336 as the liquid anion exchanger. The results indicated the formation of a species with a metal-ligand stoichiometry of 1 : 3 in the case of pyridine-2,6-diphosphonic acid (PyPOH). In the case of 2,2'-bipyridine-6,6'-diphosphonic acid (BipyPOH), however, a 1 : 2 complex was extracted and 1,10-phenanthroline-2,9-diphosphonic acid (PhenPOH) extracts the Am3+ and Eu3+ ions by forming both 1 : 2 and 1 : 3 complexes. Formation of these kinds of anionic complexes was further confirmed using electrospray ionization mass spectrometry (ESI-MS). DFT calculations predicted the structure of the anionic complexes. The non-selectivity of these kinds of ligands between Am3+ and Eu3+ was attributed to the presence of unfavorable covalent interactions in the metal-ligand bonds.

Cyphos IL 102 assisted liquid-liquid extraction studies and recovery of vanadium from spent catalyst

In this study, Cyphos IL 102 (trihexyl(tetradecyl)phosphonium bromide) diluted in toluene has been explored as an organic phase for the extraction, separation and recovery of V(V) from sulphate medium. The influence of different fundamental extraction variables namely acids and extractant concentration, equilibration time and temperature on the V(V) extraction has been evaluated. Different stripping agents have been studied for back extraction of vanadium. Saturation and recycling capacity of the extractant has also been performed. Partition behavior of other associated metal ions namely Mn(II), Fe(II/III), Al(III), Cr(III), Ti(IV), Mo(VI) and W(VI) were carried out. The extraction data offer conditions for the binary separation of V(V) from associated metal ions with high separation factors. Optimized parameters have been employed for the extraction and recovery of V(V) from spent V2O5 catalyst leach liquor. To find out the number of stages required to achieve quantitative extraction/stripping of vanadium, McCabe-Thiele plots were drawn, which were further verified by counter current simulation studies. In addition, vanadium oxide was synthesised using thermal decomposition and characterized by XRD, FESEM and EDX techniques.

A comparative study of liquid-liquid extraction in different rotating bed contactors

This study examines the influence of the internal structure of the rotor of rotating bed contactors on mass transfer characteristics in liquid-liquid extraction. Experiments were carried out in rotating spiral bed, rotating zigzag bed, and rotating packed bed. The system studied was removal of hexavalent chromium from an aqueous solution using Aliquat336 (dissolved in kerosene) as the extractant. The stage efficiency in all the rotating contactors increased with rotational speed and flow rates but decreased with feed concentration. The rotating spiral bed extractor (RSB) provides significant improvement over other rotating packed bed (RPB). The stage efficiency attained in RSB was ∼99% within a bed of radial depth ∼0.06 m at aqueous and organic flow rates of 13.34 × 10−6 m3s−1and 3.34 × 10−6 m3s-1respectively. The overall volumetric mass transfer coefficient is over twenty five times higher than that in conventional extractors like mixer settler and fixed bed.

Kinetic study of continuous liquid-liquid extraction of wine with real-time detection

Kinetic optimization of continuous liquid-liquid extraction (CLLE) can shorten sample preparation times and reduce losses of labile or volatile analytes. Here, we coupled a downscaled CLLE apparatus with atmospheric pressure chemical ionization interface of triple quadrupole mass spectrometer. Real-time sampling was guided by an Arduino-based programmable logic controller. The recorded datasets were processed to compute the extraction rate constants for the target analytes. The extraction time in subsequent on-line experiments was set to 180 min as a compromise between the reduction of the analysis time and maximizing its yield. Interestingly, off-line analysis of the extract produced different results than on-line analysis pointing to the immanent degradation of the collected extract aliquots. Next, we implemented this hyphenated system in the analysis of red wine samples, which were stored during different periods of time after opening the bottle. The results reveal differences in the depletion of the volatile wine components during storage.

First Report on the Separation of Trivalent Lanthanides from Trivalent Actinides Using an Aqueous Soluble Multiple N-Donor Ligand, 2,6-bis(1 H-tetrazol-5-yl)pyridine: Extraction, Spectroscopic, Structural, and Computational Studies.

A terdentate multiple N donor ligand, 2,6-bis(1 H-tetrazol-5-yl)pyridine (H2BTzP), was synthesized, and its complexation with trivalent americium, neodymium, and europium was studied using single-crystal X-ray diffraction, attenuated total reflectance-fourrier transform infrared spectroscopy, time-resolved fluorescence spectroscopy, UV-vis absorption spectrophotometry. Higher complexation strength of BTzP toward trivalent actinide over lanthanides as observed from UV-vis spectrophotometric study resulted in an effective separation of Am3+ and Eu3+ in liquid-liquid extraction studies employing N,N, N',N'-tetra- n-octyl diglycolamide in the presence of BTzP as the aqueous complexant. The selectivity of BTzP toward Am3+ over Eu3+ was further investigated by DFT computations, which indicated higher metal-ligand overlap in the Am3+ complex as indicated from the metal-nitrogen bond order and frontier molecular orbital analysis of the BTzP complexes of Am3+ and Eu3+.

Lanthanide extraction selectivity of a tripodal carbamoylmethylphosphine oxide ligand system.

Four tripodal carbamoylmethylphosphine oxide (CMPO)-based ligands are reported here and assessed with regard to lanthanide (Ln) coordination chemistry and selective extraction of lanthanide ions from aqueous solution. Inspired by previous liquid-liquid extraction studies that suggested a preference for terbium(iii), the current work further probes the extraction behavior of a tris-(2-aminoethyl)amine (TREN) capped, ethoxy substituted CMPO ligand with respect to the entire series of lanthanides. Upon confirmation of Tb3+ extraction selectivity versus the whole series, experiments were conducted to assess the effect of increasing the alkyl chain length within the ligand TREN cap, as well as changing the CMPO substituents by replacing the ethoxy groups with more hydrophobic phenyl groups to promote solubility in the organic extraction solvent. Extraction efficiencies remained low for most lanthanides upon increasing the cap size, with %E values consistently around 5%, and a complete loss of Tb3+ preference was noted with a decrease in %E from 18% to 3.5%. For the agent employing the original, smaller TREN cap but with phenyl substituents on the CMPO units, an increase in extraction toward the middle of the row was again observed, albeit modest, with relatively high %E values for both Gd3+ and Tb3+versus the other lanthanides (13 and 11%, respectively). A more dramatic extraction selectivity for the phenyl substituted ligand was achieved upon modification of the ligand to metal ratio, with a 100 : 1 ratio resulting in a near linear decrease in %E from 41% for La3+ to 3.7% for Lu3+. Finally, modification of the TREN capping scaffold by adding an oxygen atom to the central nitrogen led to consistently low %E values, revealing the effect of TREN cap oxidation on Ln extraction for this tripodal CMPO ligand system.