Flow injection study of the potentiometric lithium selectivity of cyclic dioxadiamides containing oxygen and nitrogen atoms

Summary Four 15-membered ring cyclic compounds with two oxygen and two nitrogen atoms incorporated in the ring were prepared and evaluated as neutral carriers in lithium ion-selective electrodes. These ionophores, along with potassium tetrakis (p-chlorophenyl)borate and o-nitrophenyloctyl ether (NPOE), were included in the PVC matrix that coated the tip of a silver-wire electrode. The potentiometric selectivities of the electrodes towards lithium over sodium, potassium, calcium and magnesium were determined. Selectivity coefficients, K _{Li, Na} ^pot ., as low as 9.5×10^–3 were obtained and smaller coefficients for other metals, K _{Li, M} ^pot ., were found. A calibration curve for lithium in the presence of 140 mmol/l sodium, with a linear portion having a slope of 51 mV/decade, was obtained. The effect of incorporating 1% trioctylphosphine oxide (TOPO) in the electrodes was studied. Comparison with the results obtained with 15-crown-4-ethers is made.

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Fließinjektionsuntersuchung der potentiometrischen Lithium-Selektivität von cyclischen Dioxadiamiden, die Sauerstoff- und Stickstoff-Atome enthalten

     

Lithium Ion Association with Sodium Phytate and the Effects on the Conformational Equilibria. Implications in the Physiological Effects of Lithium

Abstract

³¹P NMR was employed to examine the solution interactions of lithium and potassium ions with sodium phytate. The phytate molecular conformation was found to be pH and concentration dependent. The conformational equilibria of sodium phytate in aqueous solution was not affected by the addition of potassium ions, however, it was influenced by added lithium ions and was dependent on lithium ion concentration. Furthesmore, the phytate molecule showed some selectivity for lithium ion association over potassium and sodium ions. Possible implications in the physiological effects of lithium are discussed.     

Nonaqueous Liquid-Liquid Extraction: Extraction of Zinc from Ethylene Glycol Solution of Chloride by Trioctylphosphine Oxide

Abstract

The distribution of zinc between the toluene phase containing trioctylphosphine oxide (TOPO) and the nonaqueous ethylene glycol phase containing either hydrogen or lithium chloride has been investigated by using zinc-65. In the zinc-hydrogen or lithium-chloride-TOPO system, the complex ZnCl₂-2TOPO may predominantly occur in the toluene phase, and only mononuclear zinc complexes appear to exist in the two phases.     

Solvent extraction of alkaline earth metals,and lithium with 1-phenyl-3-methyl-4-acylpyrazol-5-ones and trioctylphosphine oxide

The synergic extraction of magnesium, calcium, strongium, barium and lithium into cyclohexane or benzene containing 1-phenyl-3-methyl-4-acyl-pyrazol-5-one (HA) and tri-n-octylphosphine oxide (TOPO) was investigated as a function of pH, HA and TOPO concentration. The extracted species when the 4-benzoyl compound was used, were MA₂(TOPO)₂ (M = Mg, Ca, Sr), BaA₂(TOPO)₃ and LiA(TOPO)₂. When the 4-trifluoro-acetyl derivatives was used, the extracted species were the same except for SrA₂(TOPO)₃. Extraction constants for the synergic extractions were calculated.     

Extraction-separation of Eu(III) and Th(IV) ions from nitrate media into a room-temperature ionic liquid

Application of a room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim⁺][PF₆ ^?]), in the extraction of Eu(III) and Th(IV) ions from nitrate media using tri-n-octylphosphine oxide (TOPO) as extractant is investigated. The results are compared with those obtained in dichloromethane. It is shown that the europium ions are extracted via a solvation mechanism by formation of [Eu(TOPO) ₃ ³⁺ ](NO₃ ^?)₃ species in both [C₄mim⁺][PF₆ ^?] and dichloromethane. Nevertheless, application of the studied RTIL makes a significant improvement in the extraction efficiency of europium ions. A different attitude was observed for the extraction of thorium ions. In fact, although the analysis of the extraction data of these ions from sodium nitrate solutions confirms the formation of [Th(TOPO) ₃ ⁴⁺ ](NO₃ ^?)₄ species in dichloromethane, the extraction of these ions into the ionic liquid was not affected by the presence of TOPO. This latter outcome states the process takes place by a cation-exchange mechanism. It is found that the extraction of thorium ions diminishes in the presence of nitric acid. Interestingly, in contrast to the results observed in the extraction of thorium ions from sodium nitrate solutions, TOPO shows a co-operative effect on the extraction of these ions from nitric acid media. This allows considering the mechanism of the extraction of Th⁴⁺ ions from nitric acid media as a mixed ion exchange-solvation mechanisms by formation of [Th(TOPO)⁴⁺](NO₃ ^?)(PF₆ ^?)₃ species.     

4-Phosphoryl Pyrazolones for Highly Selective Lithium Separation from Alkali Metal Ions

Effective receptors for the separation of Li⁺ from a mixture with other alkali metal ions under mild conditions remains an important challenge that could benefit from new approaches. In this study, it is demonstrated that the 4-phosphoryl pyrazolones, H L ²-H L ⁴, in the presence of the typical industrial organophosphorus co-ligands tributylphosphine oxide (TBPO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO), are able to selectively recognise and extract lithium ions from aqueous solution. Structural investigations in solution as well as in the solid state reveal the existence of a series of multinuclear Li⁺ complexes that include dimers (TBPO, TBP) as well as rarely observed trimers (TOPO) and represent the first clear evidence for the synergistic role of the co-ligands in the extraction process. Our findings are supported by detailed NMR, MS and extraction studies. Liquid-liquid extraction in the presence of TOPO revealed an unprecedented high Li⁺ extraction efficiency (78 %) for H L ⁴ compared to the use of the industrially employed acylpyrazolone H L ¹ (15 %) and benzoyl-1,1,1-trifluoroacetone (52 %) extractants. In addition, a high selectivity for Li⁺ over Na⁺, K⁺ and Cs⁺ under mild conditions (pH ∼8.2) confirms that H L ²-H L ⁴ represent a new class of ligands that are very effective extractants for use in lithium separation.     

Selective Lithium Adsorption of Silicon Oxide Coated Lithium Aluminum Layered Double Hydroxide Nanocrystals and Their Regeneration

Silicon oxide-coated lithium aluminum layered double hydroxide (Li_xAl₂-LDH@SiO₂) nanocrystals (NCs) are investigated to selectively separate lithium cations in aqueous lithium resources. We directly synthesized Li_xAl₂-LDH NC arrays by oxidation of aluminum foil substrate under a urea and lithium solution. Various lithium salts, including Cl⁻, CO₃²⁻, NO₃⁻, and SO₄²⁻, were applied in aqueous solution to confirm the anion effect on the captured and released lithium quantity of the Li_xAl₂-LDH NCs. In a 5% solution of sulfate ions mix with lithium chloride, the Li_xAl₂-LDH NCs separated a larger quantity of lithium than in other anion conditions. To enhance regeneration stability and lithium selectivity, thin layers of SiO₂ were coated onto the Li_xAl₂-LDH nanostructure arrays for inhibition of nanostructure destruction after desorption of lithium cations in hot water. The Li_xAl₂-LDH@SiO₂ nanostructures showed enhanced properties for lithium adsorption, including increase of stable regeneration cycles from three to five cycles, and they showed high lithium selectivity in the Mg²⁺, Na⁺, and K⁺ cation mixed aqueous resource. Our nanostructured LDH lithium adsorbents would provide a facile and efficient application for cost-efficient and large-scale lithium production.     

Symmetric ethereal hosts for lithium: factors for high affinity and selectivity upon ion recognition

Abstract

Since the host-guest chemistry field has been formulated, organic hosts for various ions have been studied extensively. It is now widely accepted that structural and electrostatic complementarity is very important in host-guest chemistry. However, the detailed understanding which enables the chemists to design useful hosts is still in paucity. Although the calculated gas-phase binding energy is not of direct use for many practical applications, this could provide an objective measure for the intrinsic affinity. Here, we have calculated approximate binding energies for famous organic hosts for lithium. The selectivity between lithium and sodium was also investigated. 6-311++G(d,p) basis set with B3LYP functional was used to calculate binding energy of Li⁺ and Na⁺ with four famous hosts. They are spherand, [2,1,1]cryptand, 12-crown-4 and [1₆]starand. We examined several factors such as coordination number, partial charge of oxygen, distance from metal to its coordinating oxygen and metal-dipolar moiety interactions. Within the boundary of the chosen four symmetric hosts in this work, charge–dipolar moiety orientation was the factor that roughly explains the calculated binding affinity.     

Solvent Extraction of Alkaline Earths with 1-Phenyl -3-Methyl 4 Stearoylpyrazol - 5 - One and Topo

Abstract

The synergic extraction of Ca, Sr, and Ba ions from aqueous solutions into cyclohexane or benzene containing 1- pheny 1 - 3 - methyl - 4 - stearoylpyrazol - 5 - one (HPMSP) and TOPO has been studied. Quantitative extraction (log D>2) was attained at pH>5.4 for Ca, pH>6.5 for Sr, and pH>7.3 for Ba when cyclohexane containing 0.05 M HPMSP and 0.01 M TOPO was used, and the corresoponding values for benzene were 6.5, 7.8, and 8.4. Extracted species were M(PMSP)₂(TOPO)₃ (M=Ca, Sr, Ba) for cyclohexane and Ca(PMSP)₂(TOPO)₃ and Sr (or Ba) (PMSP)₂(TOPO)₂ for benzene.     

Sodium Ion-Selective Chalcogenide Glass Electrodes

Abstract

Analytical characteristics and sensing mechanism of sodium ion-selective electrodes based on NaCl-Ga₂S₃-GeS₂ glasses have been investigated. Chalcogenide glass electrodes containing 10 mol.% NaCl in the membrane showed near-Nernstian response in the concentration range from 10-³ to 1 M sodium nitrate solution. These sensors were superior to the conventional pNa oxide glass electrodes in selectivity in the presence of hydrogen ions and in Na⁺ ion sensitivity in fluoride media. Prolonged solution treatment for several days reduces, however, the detection limit of the sensors and the slope of the electrode response. Ionic processes at the membrane surface have been investigated using XPS technique and ²²Na tracer measurements. It was shown that sodium ion-exchange governed Na⁺ ion response of chalcogenide     

1,4,7,10-Tetraoxacyclododecane(12-Crown-4) as Neutral Carrier for Lithium Ion in Lithium Ion Selective Electrode

Abstract

1,4,7,10-Tetraoxacyclododecane (12-crown-4) (I) and its lithium complex (II) are used as neutral carriers for lithium ion in polyvinylchloride membrane ion selective electrodes. The lithium response varies with concentration, being near Mernstian at low (10^?5-10^?4 M) concentrations and sub-Nernstian (24-28 aV) at higher concentrations (10^?3 M). The selectivity coefficients K_Li ^Pot _M for II are: Na⁺ (0.12), K⁺ (0.66), Cs⁺ (0.15), Mg²⁺ (1.6 × 10^?4), Ca²⁺ (3.1 × 10^?4), Ba²⁺ (9.5 × 10^?7), NH⁺ ₄ (9.0 × 10^?2), H⁺ (2.2).     

Study of the membrane-extraction properties of O-hexyl-(N,N-di-2-ethylhexyl)methylphosphonic acid

ABSTRACT

It was found that the O-hexyl-(N, N-di-2-ethylhexyl)methylphosphonic acid is a good membrane carrier for lithium ion. Thus, the O-hexyl-(N, N-di-2-ethylhexyl) methylphosphonic acid exhibits a sufficiently high ability to transfer lithium and sodium ions through the liquid membrane, and also exhibits high selectivity for lithium ions.     

Use of a flow-injection system in the evaluation of the characteristic behavior of neutral carriers in lithium ion-selective electrodes

A flow-injection system based on microconduits is used to investigate electrode characteristics such as selectivity, detection limit, and response and equilibrium times of the new ionophore, N,N,N′,N′-tetraisobutyl-5,5-dimethyl-3,7-dioxanonane diamide, in lithium ion-selective electrodes. These characteristics were compared with those of the ionophore N,N′-diheptyl-N,N′,5,5-tetramethyl-3,7-dioxanone diamide. The new ionophore has superior detection limits and shorter response and equilibrium time, but the other exhibits better selectivity for lithium with respect to sodium. Values of K^Pot_LiNa for the new ionophore vary from 0.0450 to 0.566, depending on the methods of measurement and solution conditions. This phenomenon is discussed. Stop-flow experiments effectively demonstrated the response and equilibrium time differences between these two ionophore membranes.     

Nonaqueous Liquid-Liquid Extraction. Extraction of Zinc from Methanol-Water Solution of Chloride by Trioctylphosph1Ne Oxide in Decaline

Abstract

The distribution of zinc was studied between the decaline phase having tri-n-octylphosphine oxide (TOPO) and the methanol-water phase (4:1 in molar ratio) having chloride ion, and the stability constants of zinc with chloride in the methanolic solution were calculated from the extraction experiments (K₁ = 2.4 × 10³, K₂ = 1.9 × 10²at 298°K).     

Analytical Methods for Determining the Concentration Ratio in Mixtures of Trioctylphosphine Oxide and Di(2-Ethylhexyl)Phosphoric Acid

Abstract

Analytical methods are described for determining the concentration ratio of trioctylphosphine oxide (TOPO) and di(2-ethylhexyl)phosphoric acid (D₂ EHPA) in hydrocarbon solvents or in mixtures where the D₂ EHPA is the solvent. The Electron Spectroscopy for Chemical Analysis (ESCA) method was used to analyze the mixtures for the relative amounts of phosphine oxide-phosphorus to phosphoric acid-phosphorus as well as the variance with the mixture composition of the Ols/P2p signal intensity. The nmr signal strength of the protons of the oxymethylene group of the D₂ EHPA and the signal strength of the other protons of D₂ EHPA and TOPO were measured in solutions of varying concentrations of D₂ EHPA and TOPO. Mass spectral comparisons of the molecular ion strengths of TOPO and D₂ EHPA were also correlated with mixture composition.     

A New Extraction System Based on Isopropyl Salicylate and Trioctylphosphine Oxide for Separating Alkali Metals

It was established that isopropyl salicylate can be used similarly to 1,3-diketones as a key component for a new efficient extraction system for selective separation of alkali metal cations. According to DFT modeling of complexes of isopropyl salicylate and 1,3-diketone with alkali metal cations (Li⁺, Na⁺, K⁺), six-membered metallacycles are formed whose stability decreases along the series Li > Na > K, which results in the observed enhanced affinity to lithium. The extraction ability of isopropyl salicylate is manifested in the presence of trioctylphosphine oxide (TOPO). The newly obtained complexes of isopropyl salicylate with alkali metal cations as well as their extracts in a mixture with TOPO are characterized by means of FT-IR, Raman, and NMR spectroscopy. The probable structure of the extracted lithium complex is presumed and the role of TOPO in the extraction process is investigated in detail. Extraction experiments showed extremely high separation coefficients for Li/Na and Li/K pairs in the extraction from a model multi-component solution.     

The sodium responsive tungsten bronze electrode: An electrode for sodium ion analysis of DNA solutions

The preparation and construction of tungsten bronze electrodes, responsive to sodium ions, are reported. The electrodes were made from tungsten bronze powder (Na_0.4WO₃), compressed into pellets with a resin binder and sealed in epoxy resin.The electrodes were found to respond almost instantenously to changes in sodium ion concentration and to be relatively stable with time. The pH dependence decreases as the sodium ion concentration increases, indicating suitability for solutions of sea water concentration.Unfortunately the electrodes show a response to potassium ions of apparently equal magnitude to the sodium response between 0.001 mol kg⁻¹ and 0.1 mol kg⁻¹. Preliminary tests indicate that they also respond to lithium, calcium, aluminium, cupric and tetramethylammonium ions at concentrations of 0.1 mol kg⁻¹. At high sodium ion concentrations ( 1 mol kg⁻¹) the effect of cross sensitivity is negligible for these ions. No attempts are made in this short paper to evaluate selectivity coefficients. Some data demonstrating the low but linear response to sodium ion are given. Tests carried out in DNA—saline-bearing solutions suggest that the possible suitability for marine or biological applications.     

Evidences for Chelating Complexes of Lithium with Phenylphosphinic and Phenylphosphonic Acids: A Spectroscopic and DFT Study

Abstract

Lithium complexes were prepared with phenylphosphinic and phenylphosphonic acids. The complexes were studied in the solid state using Fourier transform infrared spectroscopy spectroscopy and in solution (methanol) using ¹H, ¹³C, and ³¹P Nuclear magnetic resonance spectroscopy (NMR) spectroscopy; the most preferred structures of the complexes were determined by density functional theory (DFT) computational method. Although methanol has a strong solvation effect on lithium ions and ligands, which causes dissociation of the complexes, significant changes of the NMR spectra of the complexes (relative to those of the free ligands) were observed. The new spectroscopic results indicate the presence of the phenylphosphinic acid tautomer (I: C₆H₅PH(?O)OH) rather than that of phenyl-phosphorous acid (II: C₆H₅P(OH)₂) in deuterated methanol showing PH/PD exchange. On the other hand, tautomer I predominates in the complex with lithium without showing PH/PD exchange. The DFT calculations predict that tautomer I is the preferred structure in the case of free ligand and lithium complex. The absence of a PH/PD exchange in the complex is due to the formation of a chelating complex, rather than of a simple salt between lithium ion and the two oxygen atoms of I, which prevent tautomerization of I into II. DFT calculations support the formation of lithium chelating complexes. The lithium ion was found to affect the spectroscopic properties of phenylphosphinic acid more dramatically than those of phenylphosphonic acid.     

Synergistic extraction of copper(II) from sulfate medium with capric acid and tri-n-octylphosphine oxide in chloroform

The synergistic solvent extraction of copper(II) from 0.33?mol?dm^?3 Na₂SO₄ aqueous solutions with capric acid (HL) in the absence and presence of tri-n-octylphosphine oxide (TOPO) in chloroform at 25°C has been studied. The extracted species when capric acid was used alone is CuL₂(HL)₂. In the presence of TOPO, the extracted complex is CuL₂(HL)₂(TOPO). The TOPO–HL interaction strongly influences the synergistic extraction efficiency. The extraction constants were calculated.