Synergistic solvent extraction of zirconium(IV)

The extraction of Zr(IV) by 2-thenoyltrifluoroacetone (TTA) in carbon tetrachloride from aqueous hydrochloric acid solutions is a slow process. The addition of a neutral extractant, di-n-pentyl sulfoxide (DPSO) enhances considerably the rate as well as the percentage of extraction. The species extracted appears to be ZrCl₂(TTA)₂·2 DPSO. An increase in temperature results in a further increase in the rate and percentage of extraction. Studies have also been carried out on the extraction of the metal by mixtures of various neutral extractants. Thermodynamic parameters associated with the formation of the synergistic adducts have been evaluated.     

Synergistic extraction of cobalt(II) by tri-octylamine and neutral donors

This work reports a study on the synergistic extraction of cobalt(II), spiked with⁶⁰Co from hydrochloric acid solutions by mixtures of trioctylamine (TOA) and neutral organophosphorous donors into carbon tetrachloride. Synergistic coefficients and adduct formation constants have been evaluated from distribution measurements and correlated with the basic character of donors.     

Extraction of zirconium(IV) from hydrochloric acid solutions by tri-octylamine and neutral donors

Solvent extraction of Zr(IV) from aqueous HCl solutions by mixtures of TOA and different organophosphorous bases in carbontetrachloride solvent have been found to be always higher than that by any single extractant. Synergism has been observed in the range of 2.4–9.6M HCl. Although the species extracted with neutral donor alone seems to be ZrCl₄·TOPO etc, with a mixture of extractants, however, the extracted species appears to be Q₂ZrCl₆·TOPO where Q is R₃NH. The extraction has also been found to increase with increase in the concentration of amines and neutral donors. Enhancement of extraction has been explained by the formation of a complex adduct in organic phase. Synergistic coefficients and apparent formation constants of the complex adducts have also been calculated.     

Synergistic extraction of cobalt (II) by beta hydroxy naphthaldoxime and neutral donors

Liquid - liquid extraction of Cobalt (II) from aqueous hydrochloric acid medium by the use of oxime derivative of beta-hydroxy naphthaldehyde in o-xylene medium is being reported. The ligand was synthesized and characterized in our laboratory. The typical pH range of extraction of Co (II) by the ligand - donor combination was seen to be between 8 - 9. The effect of different donors like dimethyl sulphoxide (DMSO), trioctyl phosphine oxide (TOPO) and bis(2-ethylhexyl) phosphonate and the effect of various diluents on the extraction of Co(II) by the present method were studied in detail. The binary adduct formation constant (log kex) in the organic phase was found to be 3.182. The overall equilibrium constant (log K) for the ternary species [Co(A)(DMSO)(Cl)], [Co(A)(TOPO)(Cl)] and [Co(A)(phosphonate)(Cl)] were estimated to be 6.42, 6.22 and 6.25 respectively. The trend in equilibrium constants were in accordance with their basic character, i.e., (DMSO > or = TOPO approximately/= phosphonate). The results were extrapolated in the determination of Cobalt in pharmaceutical drugs and cobalt bearing ore samples.     

Synergistic effects in the solvent extraction of zinc with salicylaldoxime

The extraction of zinc with salicylaldoxime was studied. The adduct-forming tendency of zinc salicylaldoximate with pyridine, alpha-picoline, beta-picoline, quinohne and isoquinoline was also investigated. This tendency decreases in the order beta-picoline > pyridine > alpha-picoline > isoquinoline > quinoline.     

Spectrophotometric studies on the formation of adducts involved in synergistic extraction of uranium(IV) by mixtures of HTTA and neutral donors

Formation of adducts between U(TTA)₄ and several neutral donors was studied by spectrophotometry and it was shown that each of the neutral donors forms only 1∶1 adduct with U(TTA)₄. The adduct formation constants with some neutral donors were determined for benzene and chloroform media. As these adducts are involved in the synergistic extraction of U(IV) from aqueous media by mixtures of HTTA and neutral donors dissolved in organic solvents, the extraction equilibrium constants were estimated, The adduct formation was found to result in an increase of the co-ordination number of U(IV) from 8 in U(TTA)₄ to 9 in the adducts it forms with the neutral donors. Similar absorption spectral studies with U(DBM)₄ revealed that it forms much weaker adducts than the corresponding ones with U(TTA)₄.     

Synergistic effect of heterocyclic bidentate amines on the extraction of thorium(IV) with 2-thenoyltrifluoroacetone

The synergistic effect on the extraction of thorium(IV) was found by the combination of 2-thenoyltrifluoroacetone (Htta) and 1,10-phenanthroline (phen) or 4,7-diphenyl-1,10-phenanthroline (dpp) as a neutral bidentate ligand. Especially in the presence of dpp (1·10^–3M) in benzene, the distribution ratio of thorium(IV) increased by a factor of about 300. Such synergistic enhancement of the extraction was ascribed to the formation of the adduct complex of Th(tta)₄(phen) and Th(tta)₄(dpp) in the organic phase. The extraction constant and the adduct formation constant were determined and discussed.     

Synergic extraction of uranium(VI) by combination of tri-iso-octylamine and neutral donors

Synergistic effect of neutral donors like tri-butyl phosphate (TBP), triphenyl phosphine oxide (TPPO), trioctyl phosphine oxide (TOPO), and dimethyl sulphoxide (DMSO) on the extraction of uranium(VI) by tri-isooctyl amine into CCl₄ is reported. Synergistic coefficients and adduct formation constants are calculated from distribution data and correlated with relative donor abilities of added bases.     

The x-ray structure of the h5-cyclopentadienyltris(tropolonato)zirconium(IV) 1:1 dichloromethane solvate

X-ray structure analysis has shown that h⁵-cyclopentadienyltris(tropolonato)zirconium(IV) may be regarded as seven-coordinate with a slightly distorted pentagonal bipyramidal geometry; the h⁵-cyclopentadienyl group occupies an axial position.     

Unprecedented acceleration of zirconium(IV)-assisted peptide hydrolysis at neutral pH

4,13-Diaza-18-crown-6 substantially increases the rate of zirconium(IV) hydrolysis of unactivated peptide amide bonds under near-physiological conditions of temperature and pH. In the presence of this azacrown ether, ZrCl(4) efficiently hydrolyses both neutral and negatively charged peptides (pH 7.0-7.3, 37-60 degrees C).     

The effect of tin(II) chloride on the liquid-liquid extraction of tetrachloroplatinate(II) ions by triphenylphosphine in dichloromethane

The effect of tin(II) chloride on the extraction of tetrachloroplatinate(II) in 1.0–1.5 M HCl into dichloromethane with triphenylphosphine (TPP) is described. Tin(II) chloride dramatically increases the rate and efficiency of platinum extraction. The percentage of platinum extracted depends in a complicated way on the time allowed for extraction, the Pt:Sn(II) ratio, the Pt:TPP ratio, and to a lesser extent to the hydrochloric acid concentration. Tin is initially extracted into the organic phase, probably as [Pt(SnCl₃)Cl(PPh₃)₂], but is subsequently back-extracted into the aqueous phase, as a result of the relatively slow disproportionation reaction: [Pt(SnCl₃)Cl(PPh₃)₂]_org + cl^? ? [Pt(PPh₃)₂Cl₂]_org + SnCl^?₃.     

Synergistic solvent extraction studies of uranium(VI) using a combination of naphthenic acid and various neutral donors into benzene

The equilibrium extraction behavior of uranium(VI) using a benzene solution containing naphthenic acid either alone or combined with one of the adductants viz., diphenyl sulphoxide, dinonyl sulphoxide, tri-n-butyl phosphate, triphenyl phosphine oxide, tri-n-octyl phosphine oxide, triphenyl arsine oxide, 2,9 dimethyl 1,10-phenanthroline, 1,10-phenanthroline, 4,7-diphenyl 1,10-phenanthroline, 2,2′-bipyridyl and 2,2′-biquinoline is described. The enhancement in the extraction by addition of such neutral adducts is explained in terms of adduct formation of the metal chelates in the organic phase. The composition of the extracted species is obtained from slope analysis and pH_0,5 values are also obtained. The effect of various parameters such as equilibrium pH, extractant concentration, various diluents on the extraction of U(VI) with 2% naphthenic acid has been carried out. Stripping or back extraction with various mineral acids was also studied.     

Studies on extraction of zirconium(IV) by tricapryl methyl ammonium chloride from sulphate media and its separation from hafnium(IV)

The distribution of Zr(IV) between aqueous H₂SO₄ solutions and organic phases of tricapryl methyl ammonium chloride has been described. The dependence of extraction on acidity, metal and solvent concentration, diluent type and temperature was thoroughly investigated. The possible extraction mechanism is discussed in the light of results obtained. A method for the separation of Hf(IV) from Zr(IV) is also suggested.     

On the stabilization of niobium(V) solutions by zirconium(IV) and hafnium(IV)

Niobium cannot be separated from zirconium or hafnium when these elements occur together in solution with common anions such as chloride and sulphate. This is ascribed to the co-polymerization of niobium(V) and the hydrolysed ionic species of zirconium(IV) and hafnium(IV) to form colloidal particles. In hydrochloric acid the particles are positively charged, whereas in sulphate solution the Zr-and Hf-sulphate complexes confer a negative charge. The two cases are considered separately.     

Synergistic extraction of hexavalent actinides by HTTA and neutral donors-II

Synergistic extraction studies on Np(VI) and Pu(VI) have been carried out as a part of the programme on the synergistic extraction of hexavalent actinides. Extraction of Np(VI) and Pu(VI) were carried out by mixtures of HTTA and TBP in benzene from aqueous perchlorate and nitrate media. Equilibrium constant values for the various reaction equilibria involved were calculated from the data obtained by using slope-ratio as well as Job’s method. The extraction of Np(VI) by the synergistic mixture from 1M nitric acid indicated that the species NpO₂ (TTA) (NO₃). TBP was not involved in the extraction. The log values of K_A, K_AB and β_AB were −1.5, 2.92 and 4.43, respectively for Np(VI) and −1.63, 2.50 and 4.13 respectively for Pu(VI).     

Carboxylato complexes of zirconium(IV)

The preparation and thermal decomposition of several trifluoroacetatozirconium chlorides is described. A mechanism for the thermal decomposition is proposed and the formation of zirconium tetrafluoride discussed in terms of composition of the parent compound.

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Zusammenfassung Es wurde die thermische Zersetzung und die Darstellung einiger Trifluoroazetatozirkoniumchloride beschrieben. Für die Zersetzungsreaktion wurde ein Mechanismus vorgeschlagen und die Bildung von Zirkoniumtetrachlorid unter den Gesichtspunkten der Zersetzung der Mutterverbindung erläutert.

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One of us (CMS) wishes to thank the SERC, England, for a maintenance award.     

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.     

Schiff base derivatives of titanium(IV) and zirconium(IV)

The reactions of a few bifunctional and tridentate Schiff bases with titanium-(IV) and zirconium(IV) isopropoxides in equimolar and bimolar ratios are described. The resulting compounds have been obtained in almost quantitative yields and are of the general formulae M(SB)_x(OPrⁱ)_4?2X (where M = Ti or Zr; SB- = anion of the Schiff base SBH₂ and x = 1 or 2). Their molecular weights have been determined ebullioscopically and IR spectra recorded.