Extraction of strontium from nitric acid solutions by selected crown ethers

The extraction of Sr from nitric acid solutions by the crown ethers, 12-crown-4, 15-crown-5, 18-crown-6 and DB 18-crown-6 dissolved in chloroform has been investigated. Sr is reasonably well extracted by 18-crown-6 compared to other crown ethers from different nitric acid solutions. The extraction is strongly dependent on the concentration of HNO₃ and nitrate salts. Preliminary studies indicate that¹³⁷Cs is also extracted to a limited extent by 18-crown-6 from nitrate medium. Stripping of Sr was achieved by an aqueous solution of low acidity, the crown ether being regenerated for subsequent extraction.     

Solvent extraction of uranium(VI) into toluene by dicyclohexano-18-crown-6 from mixed aqueous-organic solutions

Extraction behaviour of uranium(VI) from mixed organo-aqueous solutions containing water-miscible protic aliphatic alcohols and several aprotic solvents was investigated by using dicyclohexano-18-crown-6(DC18C6) as an extractant. The organic phase was a binary solution of DC18C6 and toluene while the polar phase was a three component solution of uranyl nitrate, polar additive and aqueous nitric acid. Methanol, ethanol, isobutanol, dioxane, acetone, propylene carbonate and acetonitrile were used as the organic components of the mixed (polar) phase. Propylene carbonate, acetone, acetonitrile and dioxane increased the extractability of U(VI), whereas alcoholic additives showed only an antagonistic effect. The relative increase in extraction was found to be more at lower nitric acid concentrations. Possible reasons for such behaviour are briefly discussed. Recovery of U(VI) from loaded organic phase was easily accomplished using dilute perchloric acid and sulphuric acid. A sample method was standardized for the separation of plutonium(IV) from uranium(VI) based on its reductive stripping.     

Separation of components of the solution modeling PUREX raffinate via extraction by crown ethers to 1,1,7-trihydrododecafluoroheptanol

We study the extraction of strontium, cesium, and some other elements by dicyclohexano-18-crown-6 (DCH18C6) and its di-tert-butyl derivative (DTBDCH18C6) in the system 1,1,7-trihydrododecafluoroheptanol-water from the solution modeling PUREX raffinate. We show that strontium under these conditions is extracted in a single contact with distribution ratios of 100–200 and separates from sodium, whose distribution ratio is less than 0.01. Strontium extraction in a single contact reaches 99.5%. The stoichiometry and stability constants are determined for nitric acid complexes of the crown ethers studied with coextraction of nitric acid (1: 1). The mutual solubilities of the components in the system 1,1,7-trihydrododecafluoroheptanol-water are calculated using chromatography/mass spectrometry: water in alcohol is 0.5 wt %, and alcohol in water is 0.16 wt %.     

Sodium and potassium benzeneazophosphonate complexes with crown ethers: Solid-state microwave synthesis, characterization and biological activity

The eco-friendly synthesis, spectroscopic (IR, MS, ¹H and ¹³C NMR) study and biological (cytostatic, antiviral) activity of sodium and potassium benzeneazophosphonate complexes, obtained by reaction in the solid state under microwave irradiation of the alkali salts of ethyl [α-(4-benzeneazoanilino)-N-benzyl]phosphonic acid and [α-(4-benzeneazoanilino)-N-4-methoxybenzyl]phosphonic acid with crown ethers containing 18-membered (dibenzo-18-crown-6 and bis(4′-di-tert-butylbenzo)-18-crown-6), 24-membered (dibenzo-24-crown-8) and 30-membered (dibenzo-30-crown-10) macrocyclic rings, have been described. The simple work-up solvent free reaction is an efficient green procedure for the formation of mononuclear crown ether complexes in which the sodium/potassium ion is bound to oxygen atoms of the macrocycle and the phosphonic acid oxygen. The free crown ethers, alkali benzeneazophosphonate salts and their complexes were evaluated for their cytostatic activity in vitro against murine leukemia L1210, murine mammary carcinoma FM3A and human T-lymphocyte CEM and MT-4 cell lines, as well as for their antiviral activity against a wide variety of DNA and RNA viruses. The investigated compounds showed no specific antiviral activity, whereas all the free crown ethers and their complexes demonstrated cytostatic activity, which was especially pronounced in the case of bis(4′-di-tert-butylbenzo)-18-crown-6 and its complexes.     

Comparison of extraction ability of 18-membered crown ethers with respect to cesium

In the present work, a comparative investigation of the extraction ability of some commercially available 18-membered crown ethers with respect to cesium cation from different media is carried out. It has been shown that, in the series of 18-membered crown ethers, di-tert-butyl-dibenzo-18-crown-6 has comparable extraction ability to that of the well-known analog di-tert-butyl-dicyclohexano-18-crown-6, which much readily available synthetically.     

Preparation and application of HPLC chiral stationary phases based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid

Preparation of liquid chromatographic chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid and their application are reviewed. The various methods of connecting (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to silica gel covalently or dynamically are demonstrated. The CSPs based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid have been very successful for the resolution of various primary amino compounds with the use of an aqueous mobile phase containing organic and acidic modifiers. In addition, the resolution of secondary amino compounds including beta-blockers and N-(3,5-dinitrobenzoyl)-alpha-amino acids has been demonstrated on a CSP based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid with a non-aqueous mobile phase.     

Synergism of crown ethers in the thenoyl trifluoroacetone extraction of americium(III) in benzene medium

The synergism of the crown ethers (CE) dicyclohexano-18-crown-6 (DC18C6), dibenzo-18-crown-6 (DB18C6) and 18-crown-6 (18C6) has been investigated in the thenoyl trifluoroacetone (HTTA) extraction of americium(III) in benzene medium from an aqueous phase of ionic strength 0.5 and pH 3.50 at room temperature (23°C). The extracted synergistic species have the general formula Am(TTA)₃ · CE except for DC18C6 in which case the species Am(TTA)₃·2CE was also observed at high CE concentrations. The order of synergism was found to be DC18C6>DB18C6>18C6, which is the order of the basicity of CE as indicated by their ability to extract hydrogen ions from nitric acid solutions.     

Cesium Complex of an Unsymmetrical Calix[4]crown-dibenzocrown-6

An unsymmetrical calix[4]-bis-crown ether having both conventional crown-6 and dibenzocrown-6 rings in a fixed 1,3-alternate conformation was synthesized with good yield by the reaction of a monocyclic calix[4]crown-6 with dibenzodimesylate in the presence of cesium carbonate. The cesium ion selectivity among alkali metal ions increased compared to symmetrical calix[4]-bis-crown-6. The solid state structureof the ligand-cesium complex illustrates a 1:2 complex ratio. On the contrary, insolution, e.g., extraction equilibrium and ¹H NMR experiment gave a 1:1 complex ratio. From the result of the chemical shift change upon metal ion complex, the cesium ion seems to prefer the dibenzocrown loop to the conventional crown-6 ring.     

Extraction of some lanthanides by nitrobenzene solutions of dicarbolide in the presence of 18-crown-6

The extraction of¹⁴⁴Ce and^152,154Eu microamounts by nitrobenzene solutions of bis-1,2-dicarbollylcobaltate in the presence of 18-crown-6 from aqueous solutions of nitric acid has been investigated. The protonisation constants of 18-crown-6 in water and in nitrobenzene were determined and the corresponding equilibrium constants for cerium and europium extraction were evaluated.     

Extraction distribution of microamounts of cesium in the two-phase water-HCl-nitrobenzene-benzo-18-crown-6-hydrogen dicarbollylcobaltate system

Summary Extraction of microamounts of cesium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^-) in the presence of benzo-18-crown-6 (B18C6,L) has been investigated. The equilibrium data have been explained assuming that the HL⁺, CsL⁺ and CsL complexes are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

The synthesis and coordination properties of new macrocyclic polyethers

A new type of macrocyclic polyethers has been synthesized. It consists of an azacrown ether as mother ring, e.g. 1,7-dioxa-4,10-diaza-cyclododecane (1a) or 1,7,10,16-tetraoxa-4,13-diazacycloocatadecane (1b), and two side chains attached on the two nitrogen atoms of 1a or 1b. A number of these new crown ethers are obtained by alkylation of the two secondary amino groups of 1a or 1b with corresponding halides, BrCH₂(CH₂OCH₂)_nCH₂OR, in the presence of potassium carbonate. The crown-alkali metal complex thus obtained is hydrolyzed by acid. In order to obtain pure crown ether the reaction mixture is treated with tetramethylammonium hydroxide and followed by solvent extraction. The ability of complexing alkali cations of macrocyclic polyethers in terms of the equilibrium constant have been studied by the method of solubilities of salts in chloroform. It is shown that the size of the mother ring, the number of oxygen atoms either in the ring or in the side-chains, and the ionic radius of the alkali metal are the factors governing the stability of the metal complexes. Most of these new crown ethers possess high ability for alkali metal complexation some of them, such as N,N′- di-β-methoxyethyl-1,7-dioxa-4,10-diaza-cyclododecanc (13a), possesses higher selectivity for Na+ and K+ ions than 18-crown-6- and 4,4′(5′)-dimethylbenz-30-crown-10.     

Extraction distribution of microamounts of cesium in the two-phase water-HCl-nitrobenzene-dibenzo-18-crown-6-hydrogen dicarbollylcobaltate system

Summary Extraction distribution of microamounts of cesium in the water-HCl-nitrobenzene-dibenzo-18-crown-6(L)-hydrogen dicarbollylcobaltate has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, CsL⁺and CsL_2,⁺are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Extraction of uranium from hydrochloric acid solutions by alkylated crown ethers

The extraction recovery of uranium from 1–10 mol/L hydrochloric acid solutions into solutions of alkylated crown ethers di-tert-butyldibenzo-18-crown-6 (DTBDB18C6) and di-tert-butyldicyclohexyl-18-crown-6 (DTBDCH18C6) in organic solvents (nitrobenzene, 1,2-dichloroethane, chloroform, 1-octanol) was studied. It was found that with increasing HCl concentration, the value of the distribution coefficients of uranium (D) between the organic and aqueous phases increased to a maximum value at 9 mol/L HCl for DTBDB18C6 and 6–7 mol/L HCl for DTBDCH18C6. The properties of the solvent also greatly affect the values of D, reaching a maximum in the application of nitrobenzene, dichloroethane, or their mixture. Under these conditions, D for a 0.01 mol/L solution of DTBDCH18C6 in nitrobenzene is 830, which is the highest of known values. It was determined by the slope method and the complete saturation method that the extracted complexes of the studied alkylated crown ethers with uranyl ions have the 2 : 1 composition. Thus, new supramolecular extractants of uranium from hydrochloric acid solutions have been studied, having an extremely high extraction capacity, which can be used in the analytical and preparative chemistry of uranium.     

Interfacial insights on the dibenzo-based crown ether assisted cesium extraction in [BMIM][Tf2N]–water binary system

The distribution coefficient of Cs is estimated using dibenzo-21-crown-7 (DB21C7) and di-benzo-18-crown-6 (DB18C6) in 1-butyl-3-methylimidazolium bis (trifluroromethanesulphonyl) imide (BMIMTF2N) ionic liquid by performing solvent extraction experiments. In addition, molecular dynamics studies on the extraction of cesium (Cs⁺) ion transfer from the aqueous phase to the BMIMTF2N phase is reported. The experimental findings gave a cesium distribution coefficient of 0.218 and 0.326, which agrees closely with the values of 0.2 and 0.5 obtained from MD simulation for the ionophores DB18C6 and DB21C7, respectively. Thus MD simulation may be helpful in screening the solvents prior to the experiments.

     

Extraction of cesium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6

Extraction of cesium by the nitrobenzene solution of bis-1,2-dicarbollylcobaltate in the presence of dibenzo-18-crown-6 (DB18C6, L) was investigated. It was found, that besides hydrated cesium ion Cs _org ⁺ the complexes CsL _org ⁺ and CsL _2,org ⁺ were extracted to nitrobenzene phase. No maximums on dependencies of the cesium distribution ratio (D) on the concentration of crown in the systemc _L was found andD increased monotony withc _L. Values of extraction constants and stability constants of extracted species in nitrobenzene have been determined.     

Solvent extraction of radioactive Cs<Superscript>+</Superscript> by hydroborate anionic extractants of the [1-LB<Subscript>10</Subscript>H<Subscript>9</Subscript>]<Superscript>-</Superscript> type (L = amine or phosphine)

Summary New anion derivatives of the closo-decaborate [B₁₀H₁₀]^2- bearing amine or phosphine groups were tested for the extraction of radioactive cesium cations in acidic medium. The technique used is the liquid-liquid extraction based on the complexation of Cs⁺ by these anions to form neutral compounds which are extracted by organic solvents (diluents) of medium polarity. Promising results were obtained with the anion [1-(C₆H₅CH₂)₂(C₆H₅)NB₁₀H₉]^- (3) soluble in many organic solvents. The most efficient diluent for the extraction is nitrobenzene. Using hydrochloric acid or sulfuric acid in the aqueous medium instead of nitric acid does not significantly affect the efficiency of Cs⁺ extraction.     

Extraction of cesium by the nitrobenzene solution of sodium bis-1,2-dicarbollylcobaltate in the presence of 18-crown-6

Extraction of cesium by the nitrobenzene solution of sodium bis-1,2-dicarbollylcobaltate (Na⁺B⁻) in the presence of 18-crown-6 (18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes NaL⁺, CsL⁺ and CsL₂ ⁺ are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Crown Ethers as Synergist in the 2-Thenoyltrifluoroacetone Extraction of Lanthanoids in 1,2-Dichloroethane

Summary. The solvent extraction of 14 trivalent lanthanoid ions (Ln ³⁺) from a nitrate medium into 1,2-dichloroethane containing 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (HTTA) was investigated at 25.0°C. The extraction of Ln(TTA)₃ species was confirmed and the extraction constants were determined. The extraction of Ln with the synergistic mixture of HTTA and a crown ether (CE: 12-crown-4, 18-crown-6, cyclohexano-18-crown-6 or benzo-18-crown-6) was also investigated at 25.0°C. The 1:1 adducts of the complex and crown ether, Ln(TTA)₃·(CE) are formed for all the lanthanoid ions and the CEs used in this study. The formation constants, β_add, of the adduct Ln(TTA)₃·(CE) from Ln(TTA)₃ in the organic phase were determined by nonlinear least-squares method. The stabilities and structures of the formed adducts were discussed with respect to the cavity size, steric effect, and basicity of the CE.     

Ion chromatography on chelating stationary phases: separation of alkali metals

Analytical 250x4.6 mm I.D. columns packed with iminodiacetic acid (IDA) derivatised silica were used to separate alkali metal ions and the ammonium ion in combination with non-suppressed conductivity detection. The addition of 2.5-10 mmol/l of the macrocyclic crown ether 18-crown-6 to the nitric acid eluent resulted in a change in the elution order and a significant improvement in the resolution between potassium and ammonium because of selective complexation of potassium. However, the admixture of 15-crown-5 did not improve the resolution of lithium and sodium, although 15-crown-5 is a selective complexing agent for sodium. Retention and resolution of lithium, sodium, ammonium, cesium, rubidium and potassium ions increased at lower temperatures down to 1 degree C. The simultaneous separation of alkali and transition metals under isocratic conditions was achieved with an eluent comprising 10 mmol/l 18-crown-6, 1.5 mmol/l dipicolinic acid, and 1.9 mmol/l nitric acid. The chromatographic system enabled the quantitation of alkali metal ions with detection limits in the low ppb range and excellent linearity. Finally, the applicability of the method was approved by quantitation of sodium, ammonium and potassium in different water samples.     

Synthesis,characterization, and complexing properties of a polymethacrylate bearing pendant macroheterocyclic structures

The synthesis of a polymerizable methacrylate bearing the dibenzo-18-crown-6 moiety ( 5 ) was effected in three steps by condensation of 3,4-dihydroxybenzaldehyde with 1,2-bis[2′-(2″-chloroethoxy)ethoxy]benzene ( 2 ), reduction of the resulting 4-formyldibenzo-18-crown-6 ( 3 ) to 4 and subsequent reaction of 4 with methacryloyl chloride. The methacrylate ( 5 ) was polymerized in solution using 2,2′-azobis(isobutyronitrile) (AIBN) as the initiator and gave a solid polymer ( 6 ) having a midrange T_g of 67°C. The polymethacrylate bearing pendant crown-ether structure ( 6 ) was found to effectively complex potassium ions and was clearly more effective in its complexing ability than dibenzo-18-crown-6 ( 7 ) or a polyurethane bearing the dibenzo-18-crown-6 moiety ( 8 ) in the polymer backbone. The subject polymer ( 6 ) was also found to complex and consequently solubilize several metal 7,7,8,8-tetracyanoquinodimethane (TCNQ) salts to give semiconducting compositions. Evidence is given that in the presence of the neutral acceptor molecule, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), the polymethacrylate ( 6 ) acting as a donor, gives rise to a charge-transfer (C/T) complex.