Synergic extraction of lanthanoids(III) with thenoyl trifluoroacetone and terpyridine

The synergic extraction of trivalent lanthanoids (Ln: La, Nd, Sm, Eu, Yb and Lu) with 2-thenoyltrifluoroacetone (Htta) and 2,26, 2-terpyridine (tpy) into benzene has been studied. The partition coefficient (P_s) of tpy was obtained experimentally in order to calculate the equilibrium concentration of tpy in the organic phase. From the slope analysis, it was shown that these lanthanoids were extracted as Ln(tta)₃(tpy). The adduct formation constant (_s,1) and the synergic extraction constant were obtained for each lanthanoid. The (_s,1) decreases with increasing atomic number of lanthanoids and the trend of (_s,1) is compared with that for bidentate and unidentate heterocyclic amines.     

Synergistic extraction of americium(III) with 2-thenoyltrifluoroacetone and crown ethers

Extracton, of Am³⁺ in benzene with 2-thenoyltrifluoroacetone (HTTA) and crown ethers (CEs) such as 15-crown-5, 18-crown-6, dicyclohexano-18-crown-6, dibenzo-18-crown-6, dicyclohexano-24-crown-8, and dibenzo-24-crown-8 was investigated. Synergistic effect by CE was observed regardless of the kind of CE examined. The extracted species was found to be Am(TTA)₃(CE), and adduct formation constants between Am(TTA)₃ and CE in the organic phase were determined. The sequence of constant could not be explained only by basicity of CE and the steric effect of CE should be taken into account to elucidate the adduct complex formation.     

Ion-pair extraction of Co(II) by crown ethers from perchlorate medium

The extraction of cobalt(II) by chloroform solutions of the crown ethers (CE) 12C4, I5C5, 18C6, Dbl8C6, Dchl8C6 or Dch24C8 from aqueous perchlorate medium was investigated. Slope analysis of the experimental data suggested that the extraction of Co(II) by these CEs takes place through ion-pair formation, and that the chemical formula of the main extracted species is Co(OH)(+)ClO(-)(4).CE. The magnitudes of the extraction constants are in the sequence 18C6 > Dch18C6 > Dch24C8 > Db18C6 > 15C5 > 12C4, which is discussed in terms of the correspondence between the CE cavity size and the ionic radius of cobalt(II).     

Separation of americium(III) from lanthanides(III) by nanofiltration-complexation in aqueous medium

The separation of Am(III) from a mixture of lanthanides(III) was performed in aqueous medium by nanofiltration combined with a complexation step using a DTPA derivative as selective complexing agent.     

Ion-pair extraction of uranyl ion from aqueous medium using crown ethers

Ion-pair extraction behaviour of uranyl ion from aqueous solutions was studied at pH 3.0 employing crown ethers viz. benzo 15 crown 5 (B15C5), 18 crown 6 (18C6), dibenzo 18 crown 6 (DB18C6), and dibenzo 24 crown 8 (DB24C8) in chloroform as the organic phase and picric acid as the organophilic counter anion. The stoichiometry of the extracted species corresponded to [UO₂(crown ether)_n]²⁺·[pic⁻]₂ where n=1.5 for benzo 15 crown 5 and 1 for 18 crown 6 as well as dibenzo 18 crown 6. Adducts of DB24C8 could not be observed as practically no extraction was possible using this reagent. The separation behaviour of fission products from an irradiated uranium target was also studied. An interesting observation on the separation of trivalent lanthanides from uranyl ion is reported.     

Extraction of Eu(III) and Co(II) by dihexyl N,N-diethyl carbamoyl methyl phosphonate (DHDECMP) and thenoyl trifluoroacetone (HTTA)

The extraction of Eu(III) has been carried out from nitrate solutionusing DHDECMP. Different parameters affecting the distribution of metal ionhave been studied. The distribution of Eu(III) was found to be first orderdependent on pH and second order with respect to [DHDECMP]. DHDECMP showedhigh stability towards -radiation dose up to 26.5 megarad. The extractionof Co(II) by either DHDECMP or HTTA from acetate solution showed that it issecond order dependent on both the extractant concentration and the pH. Basedon the data of the distribution ratio obtained and the calculated thermodynamicparameters; reaction mechanisms are suggested.     

Ion-pair extraction of tetravalent plutonium from hydrochloric acid medium using crown ethers

Ion-pair extraction behaviour of plutonium (IV) from varying concentrations of HCl solution was studied employing crown ethers (benzo-l5-crown-5 (B15C5), 18-crown-6, (18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6, (DC18C6), dibenzo-24-crown-8 (DB24C8) and dicyclohexano-24-crown-8 (DCH24C8)) in nitrobenzene as the extractant. Ammonium metavanidate was used as the holding oxidant in the aqueous phase and the conditions necessary for the quantitative extraction of the tetravalent ion were found. The co-extraction of species of the type [HL⁺].[HPu(Cl) ₆ ^– ] and [HL⁺]2·[Pu(Cl) ₆ ^2– ] as ion-pairs (where L represents the crown ether) is suggested.     

Synergistic extraction of Am(III), Th(IV) and U(VI) by PMBP and crown ethers

The extraction of UO ₂ ²⁺ , Am³⁺, and Th⁴⁺ by 1-phenyl-3-methyl-4-benzylpyrazolone with crown ethers was studies using 0.1M (NaClO₄) aqueous phase and toluene. The crown ethers were 12C4, 15C5, 18C6, DB18C6 and DCH18C6. The synergic equilibrium constant did not show correlation between the cationic radii and the ether cavity size nor did the values follow a simple order of ether basicity. The ether basicity, steric effects, and the number of ether oxygens bound to the cation are the combined factors which seemingly determine the pattern of M(PMBP)_n—CE interaction.     

Hydrolysis of americium(III)

A generalized scheme of americium(III) hydrolysis is proposed for a wide range of pH (1–10) and concentrations (10^–1–10^–10M). The data on Am(III) hydrolysis are presented in the form of three-dimensional isothermal diagram. This approach to the study of hydrolysis can be used for investigation of hydrolytic behaviour of most polyvalent ions.     

Rapid extraction of iron(III) with 2-thenoyl trifluoroacetone : Direct colorimetric determination in the organic phase

2-Thenoytrifluoroacetone is investigated for the rapid extraction and spectrophotometric determination of iron(III) at the milligram level. The red extract absorbs strongly below 400 mμ. The color is stable for many hours, Beer's law is obeyed at 460 mμ for 1–10 μg of iron/ml. Interferences are studied. The method is reproducible to ±1%.     

Bis(crown ethers) derived from biphenyl: extraction and electrochemical properties

Ligands derived from 4,4′-dinitrobiphenyl containing azacrown cavities in the 2,2′ position have been used in extraction and transport experiments. Control experiments with a system containing only one complexing cavity have demonstrated that the capability of forming a sandwich-type complex in the aforementioned ligand not only increases extraction but also the transport across a liquid membrane. Extraction studies have also shown that the complex present in the membrane has a 1:1 stoichiometry with regard to both ligands. Electrochemical studies have also been carried out. The ligand containing two complexing cavities is capable of giving rise to a 2:1 complex under electrochemical conditions.     

Studies on the extraction of americium(III) from aqueous nitrate media by sulfoxides

Solvent extraction behaviour of Am(III) from dilute nitric acid media with sulfoxides (R₂SO) in Solvesso-100 has been investigated over a wide range of conditions. Very poor extractability of Am necessitated the use of salting-out agents, viz., nitrates of Al, Mg, Ca, Li and NH ₄ ⁺ . Effects of certain variables such as acidity, extractant concentration, saltingout agent, temperature etc., on metal extraction by sulfoxides have been examined systematically. For a fixed sulfoxide concentration, extraction attains a maximum value up to around 0.2–0.4M HNO₃ and decreasing above 1M HNO₃. In contrast, increasing the concentration of sulfoxide (0.8M DISO, 1.3M DBuSO) gives almost quantitative Am extraction up to 1M HNO₃. For satisfactory extraction, di-n-octyl as well as di-n-hexyl sulfoxide are the most suitable extracting agents. Extractability of Am increases with increasing amounts of all the salting-out agents studied and their effect follows the sequence: Al³⁺>Mg²⁺>Ca²⁺>Li⁺>NH ₄ ⁺ ; this is also the relative dehydrating effect of the cations. The species extracted would appear to be Am(NO₃)₃.3R₂SO. Americium is easily stripped with 1–3M HNO₃ solutions from the loaded organic phase. Extraction decreases with increasing temperature, indicating the extraction to be exothermic. Extraction from partially non-aqueous solutions was also investigated.     

Radiation effects on the extraction of americium(III) with di(2-ethylhexyl) phosphoric acid

Radiation effects on the extraction of Am(III) with di (2-ethylhexyl) phosphoric acid (DEHPA) was studied by exposing DEHPA to gamma rays under various conditions. Gamma irradiation of undiluted DEHPA causes an enhancement of extraction of Am(III) due to the formation of mono (2-ethylhexyl) phosphoric acid (MEHPA) similarly to that of Nd(III). The presence of diluent during irradiation brought about a slight difference from the results in the absence of a diluent. The marked change occurred in Df when the organic solvent was exposed to γ-ray while being mixed with nitric acid solution. An initial slight increase of Df for Am(III) and Nd(III) was followed by a subsequent decrease beyond an absorbed dose of approximately 200 Wh·1⁻¹. This phenomenon was explained by the enhanced decomposition of DEHPA and the subsequent strong hydrolytic and radiolytic decomposition of MEHPA to H₃PO₄ in the aqueous phase, and the complex forming nature of H₃PO₄ with Am(III) and Nd(III).     

Synthesis and structure of complexes of gold(III) with sulfur-containing crown ethers

The 11 complexes of chloroauric acid with three sulfur-containing crown ethers, 4,7,13,16-tetraoxo-l,10-dithiocyclooctadecane (DTTO18C6) and its oxidized derivatives, the - and -forms of 4,7,13,16-tetraoxo-l,10-disulfoxocyclooctadecane (DSF18C6), have been synthesized and investigated by physicochemical methods. It is demonstrated that in all three cases the metal ion does not enter into the cavity of the macrocycle. In the case of DTTO18C6 complex formation takes place via the sulfur donor atoms of the macrocycle, in the case of the - and -forms of DSF18C6 via the oxygen of the sulfoxide group. It is assumed that gold as the complex-forming metal plays a role in the stabilization of the cis-form of the macrocyclic sulfoxide.Translated from Teoreticheskaya i Éksperimental/naya Khimiya, Vol. 26, No. 5, pp. 637–640, September–October. 1990.     

A study of radiation effects on the extraction of americium(III) with acidic organophosphates

Radiation effects on the extraction of americium(III) with several dialkylphosphoric and monoalkylphosphoric acids have been studied comparatively. The extractants were exposed to⁶⁰Co γ-rays in the absence and presence of diluent and HNO₃. The Df of Am(III) was measured and the yield of radiolytic products was determined after γ-irradiation as a function of the absorbed dose. Di(hexoxyethyl)phosphoric acid was the most susceptible to radiation among the extractants studied and its extractability was weakened by radiation regardless of the presence or absence of diluent or HNO₃. Diisodecylphosphoric acid itself showed an enhancement upon irradiation but incurred a depressant effect upon intimate contact with HNO₃·Mono(2-ethylhexyl)phosphoric acid showed a decrease of the Df of Am(III), similarly to DIDPA in the presence of HNO₃ during γ-irradiation. All the above extractants gave H₃PO₄ as the principal radiolytic product upon γ-irradiation upon intimate contact with HNO₃ causing decreasing solely the extraction of Am(III). Di(2-ethylhexyl)phosphoric acid proved to be the most stable extractant to radiation among those studied.     

An unusual extraction behavior of americium (III) and dioxouranium (VI) from picric acid medium using 18-crown-6 as neutral oxodonor

The extraction behavior of Am³⁺ and UO₂ ²⁺ is investigated employing chloroform solution of 18-crown-6 as the organic phase and picrate solution at pH 3.0 as the aqueous phase. In contrast to the commonly observed behavior, the extraction of Am³⁺ is preferred to that of UO₂ ²⁺. This unusual separation behavior is investigated as a function of several variable parameters such as crown ether concentration, picric acid concentration, inert electrolyte concentration, nature of diluent etc. Thermodynamic parameters are also evaluated.     

Ionic liquid modified silica gel for the sorption of americium(III) and europium(III) from dilute nitric acid medium

The imidazolium bis(2-ethylhexyl) phosphate moiety was chemically attached on silica gel by chemical modification. The resulting product ([SG-Im]⁺ [DEHP]^?) was characterized by FT-IR spectroscopy, thermogravimetry and elemental analysis. The sorption behavior of Am(III) and Eu(III) on [SG-Im]⁺ [DEHP]^? was studied from dilute nitric acid medium for the separation of Am(III) and Eu(III) from aqueous waste. The effect of time, concentrations of nitric acid and europium in aqueous phase on the distribution coefficient (K _d) was studied. The study indicated the possibility of using modified silica for the separation of Eu(III) from Am(III) with high separation factors (>50 at 0.1 M HNO₃).     

Study of the extraction of strontium(II) and lead(II) by crown and dithiacrown ethers

A study was carried out on the extraction of strontium(II) and lead(II) picrates by chloroform solutions of crown and dithiacrown ethers. The benzene ring substituents in benzodithia-18-crown-6 only slightly affect the extraction of strontium and lead cations and their separation. The introduction of an adamantyl group onto the benzene ring markedly increases the extraction of lead and the separation selectivity of these cations. The use of dithia derivatives of benzo-18-crown-6 is less efficient for the extraction of both strontium and lead, though the selectivity of their separation is almost the same as in the extraction with benzo-18-crown-6.M. V. Lomonosov Moscow State University, 119899 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1125–1129, August, 1997.     

Chiral recognition in NMR spectroscopy using crown ethers and their ytterbium(III) complexes

Chiral crown ethers 1 and 5 are useful enantiomeric discriminating agents in ¹H NMR spectroscopy for neutral and protonated primary amines, amino acids, and amino alcohols. The presence of the carboxylic acid groups in 1 and 5 provide sites at which ytterbium(III) can bind. Adding ytterbium(III) nitrate to crown–substrate mixtures in methanol-d₄ causes shifts in the spectra of substrates and often enhances the chiral discrimination in the ¹H NMR spectrum. The enhancement in enantiomeric discrimination that occurs in the presence of ytterbium(III) allows lower concentrations of the crown ether to be used in chiral recognition studies. Several amide derivatives of 1 were prepared and evaluated as chiral NMR discriminating agents, although except for 1e, these were less effective than 1.