Extractive Recovery of Tantalum(V) and Niobium(V) with Octanol from Hydrofluoric Acid Solutions Containing Large Amounts of Titanium(IV)

Extractive recovery with n-octanol of tantalum(V) and niobium(V) from hydrofluoric acid solutions containing large amounts of titanium (up to 2-3 M) was studied. The conditions were found for separation of tantalum(V) and niobium(V) from titanium(IV), allowing recovery of 95.7 and 84.1% of tantalum and niobium fluoride complexes, respectively, in one extraction cycle, with 2.6% recovery of titanium.     

Determination of the stability constant of Np(V) fluoride complex using a fluoride ion selective electrode

Fluoride complexing of Np(V) has been studied using fluoride ion selective electrode (F-ISE). Free fluoride ion concentrations in the presence of Np(V) were measured at 0.1 and 1.0M ionic strength. The data were used to calculate the stability constant of the fluoride complex of Np(V) and the values obtained are reported here.     

Processing of Precipitates of Hydrated Tantalum(V), Niobium(V), and Titanium(IV) Oxides in Loparite Technology

Conditions were studied for the dissolution in HF of hydrated tantalum(V), niobium(V), and titanium(IV) oxides, which are formed by acid decomposition of loparite, and also for the selective extraction of Ta(V) with octanol from the resulting fluotitanic solutions.     

Stability constants of Np(V) complexes with fluoride and sulfate at variable temperatures

Summary A solvent extraction method was used to determine the stability constants of Np(V) complexes with fluoride and sulfate in 1.0M NaClO₄ from 25 to 60 °C. The distribution ratio of Np(V) between the organic and aqueous phases was found to decrease as the concentrations of fluoride and sulfate were increased. Stability constants of the 1 : 1 Np(V)-fluoride complexes and the 1 : 1 Np(V)-sulfate and 1 : 2 Np(V)-sulfate complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the effect of [F^-] and [SO₄^2-] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different temperatures by using the Van't Hoff equation.     

Potentiometric determination of antimony in metal(II) hexafluoroantimonates(V)

The purpose of this study was to develop an accurate and precise analytical procedure for the determination of the content of antimony in coordination compounds of metal(II) hexafluoroantimonates(V) (M(SbF(6))(2) compounds, where M=Mg, Ca, Sr or Ba) synthesized in our laboratory. The major problem was to find an appropriate reagent for reductive decomposition of SbF(6)(-) to Sb(3+) required for the determination of antimony by redox titration. Effective reduction of Sb(5+) regardless of the metal M bound to SbF(6)(-) species was achieved using metallic aluminium powder in acidic medium. Precipitated Sb(0) was quantitatively reoxidized to Sb(3+) and determined potentiometrically with KBrO(3) or KMnO(4). Other metals were determined complexometrically with disodium ethylenediaminetetraacetic acid (EDTA). Highly accurate and reproducible results were obtained in the concentration range 5-25 mg Sb with an RSD smaller than 0.6%. Antimony-fluoro-hydroxo species and fluoride did not interfere with the complexometric determinations of other metals with EDTA. The developed method enabled, for the first time, complete elemental chemical analysis of M(SbF(6))(2) compounds in the bulk form.     

Use of ferric-impregnated volcanic ash for arsenate (V) adsorption from contaminated water with various mineralization degrees

Ferric-impregnated volcanic ash (FVA) which consisted mainly of different forms of iron and aluminum oxide minerals was developed for arsenate (V) removal from an aqueous medium. The adsorption experiments were conducted in both DI water samples and actual water (Lake Kasumigaura, Japan) to investigate the effects of solution mineralization degree on the As(V) removal. Kinetic and equilibrium studies conducted in actual water revealed that the mineralization of water greatly elevated the As(V) adsorption on FVA. The experiment performed in DI water indicated that the existence of multivalence metallic cations significantly enhanced the As(V) adsorption ability, whereas competing anions such as fluoride and phosphate greatly decreased the As(V) adsorption. It is suggested that FVA is a cost-effective adsorbent for As(V) removal in low-level phosphate and fluoride solution. It was important to conduct the batch experiment using the actual water to investigate the arsenic removal on adsorbents.     

Tetrabutylammonium tetra (tert-butyl alcohol) coordinated fluoride-an efficient reagent for the synthesis of fluorine derivatives of phosphorus(V) compounds

Direct conversion of phosphorus(V) chlorides to the corresponding phosphorus(V) fluorides was achieved using a solid reagent, tetrabutylammonium tetra (tert-butyl alcohol) coordinated fluoride. The phosphorus(V) fluorides were directly synthesized and efficiently isolated in very good yields.     

Study of the extraction of vanadium(V)-N-p-octyloxybenzoyl-N-phenylhydroxylamine complexes from sulphuric acid solutions containing chloride, fluoride or thiocyanate

The extraction of vanadium(V)-N-p-octyloxybenzoyl-N-phenylhydroxylamine (OBPHA) complexes from sulphuric acid containing chloride, fluoride or thiocyanate is described. The purple, red and reddish blue complexes extracted, containing chloride, fluoride or thiocyanate, have molar absorptivities of 6.1 x 10(3), 5.08 x 10(3) and 7.9 x 10(3) 1.mole(-1) .cm(-1) with maximum absorption at 540, 490 and 570 nm, respectively. A spectrophotometric determination of vanadium(V) has been based on these results. The composition of the extracted complexes is estimated as V(V): OBPHA:X(-) = 1:2:1 (X(-) = Cl(-), F and SCN(-)).     

Extraction of phosphorus(V), molybdenum(VI), and tungsten(VI) from fluoride solutions

The influence of titanim(IV) and silicon(IV) on the extraction of phosphorus(V), molybdenum (VI), and tungsten(VI) fluoride complexes by tributyl phosphate was studied.

     

Thermal decomposition of chromium(III) nitrate(V) nanohydrate

Thermal decomposition of Cr(NO₃)₃·9H₂O in helium and in synthetic air was studied by means of TG, DTA, EGA and XRD analysis. The dehydration occurs together with decomposition of nitrate(V) groups. Eight distinct stages of reaction were found. Intermediate products of decomposition are hydroxy- and oxynitrates containing chromium in hexa- and trivalent states. The process carried out in helium leads to at about 260°C and in air is formed at about 200°C. The final product of decomposition (>450°C) is Cr₂O₃, both in helium and in air. This revised version was published online in July 2006 with corrections to the Cover Date.     

Squeezing Fluoride out of Water with a Neutral Bidentate Antimony(V) Lewis Acid

Because of hydration, fluoride ions in water typically elude complexation by neutral Lewis acids. Here, we show how this limitation can be overcome with a bidentate Lewis acid containing two antimony(V) centers. This derivative ( 2 ) is obtained by the simple reaction of 4,5‐bis(diphenylstibino)‐9,9‐dimethylxanthene ( 1 ) with two equivalents of 3,4,5,6‐tetrachlorobenzoquinone (o‐chloranil). It features two square‐pyramidal stiborane units oriented in a face‐to‐face fashion. Titration experiments show that this new bidentate Lewis acid binds fluoride in aqueous solutions containing 95 % water with a binding constant (K) of 700±30 M ^?1. The structure of the fluoride adduct confirms fluoride anion chelation between the two antimony centers.     

Electron transfer in neptunyl(VI)-neptunyl(V) complexes in solution

The rates and mechanisms of the electron self-exchange between Np(V) and Np(VI) in solution have been studied with quantum chemical methods and compared with previous results for the U(V)-U(VI) pair. Both outer-sphere and inner-sphere mechanisms have been investigated, the former for the aqua ions, the latter for binuclear complexes containing hydroxide, fluoride, and carbonate as bridging ligand. Solvent effects were calculated using the Marcus equation for the outer-sphere reactions and using a nonequilibrium PCM method for the inner-sphere reactions. The nonequilibrium PCM appeared to overestimate the solvent effect for the outer-sphere reactions. The calculated rate constant for the self-exchange reaction NpO2(+)(aq) + NpO2(2+)(aq) right harpoon over left harpoon NpO2(2+)(aq) + NpO2(+)(aq), at 25 degrees C is k = 67 M(-1) s(-1), in fair agreement with the observed rates 0.0063-15 M(-1) s(-1). The differences between the Np(V)-Np(VI) and the U(V)-U(VI) pairs are minor.     

Thermolyse von Phosphor(V)-Schwefel(VI)-nitridhalogeniden

Thermolysis of Phosphorus(V) Sulfur(VI) Nitride Halides Thermolysis of compounds of the type R₂PCl = N–SO₂X (R = Cl, CH₃, C₆H₅; X = F, Cl) results in the formation of the compounds R₂P(O)Cl and [NS(O)X]_n. Pyrolysis of the title compounds with longer chains yields, among others, the cyclic compounds III and IX. IX is also one of the decomposition products of a sulfamide derivative (XXI). Finally the thermal behaviour of carbon containing phosphorus(V) sulfur(VI) nitride chlorides has been investigated.     

Molecular absorption spectrometry (MAS) by electrothermal evaporation in a graphite furnace-XIII Determination of traces of fluoride by mas of AlF after liquid-liquid extraction of fluoride with triphenylantimony(V) dihydroxide

The determination of traces of fluoride by means of the molecular absorption of AlF volatilized in graphite cuvettes is described. An extraction method for separation and preconcentration of the fluoride has been developed, to avoid matrix effects. The fluoride is extracted with 10(-3)M triphenylantimony(V) dihydroxide in M1BK, and stripped with 0.025M barium hydroxide. The method is sensitive and specific for fluoride. The detection limit is about 0.3 ng of fluoride, and the fluoride content of 6 ml of 10(-7)M solution can be determined. The determination is possible in presence of various ions, but it is estimated that usage of trace matrix separation leads to a considerable improvement in the relative detection limits (by 2-3 orders of magnitude), levels as low as 0.01 ppm being detectable in some matrices.     

Silver(I) undecafluorodiantimonate(V)

The reaction between AgBF4 and excess of SbF5 in anhydrous hydrogen fluoride (aHF) yields the white solid AgSb2F11 after the solvent and the excess of SbF5 have been pumped off. Reaction between equimolar amounts of AgSb2F11 and AgBF4 yields AgSbF6. Meanwhile, oxidation of solvolyzed AgSb2F11 in aHF by elemental fluorine yields a clear blue solution of solvated Ag(II) cations and SbF6- anions. AgSb2F11 is orthorhombic, at 250 K, Pbca, with a=1091.80(7) pm, b=1246.28(8) pm, c=3880.2(3) pm, V=5.2797(6) nm3, and Z=24. The crystal structure of AgSb2F11 is related to the already known crystal structure of H3OSb2F11. Vibrational spectra of AgSb2F11 entirely match the literature-reported vibrational spectra of beta-Ag(SbF6)2, for which a formulation of a mixed-valence AgI/AgIII compound was suggested (AgIAgIII(SbF6)4). On the basis of obtained results it can be concluded that previously reported beta-Ag(SbF6)2 is in fact Ag(I) compound with composition AgSb2F11.     

Theoretical study of electron transfer in uranyl(VI)–uranyl(V) complexes in solution

The rates of the electron self‐exchange between uranyl(VI) and uranyl(V) complexes in solution have been investigated in detail with quantum chemical methods. The calculations have shown that the bond length of U? Oyl is elongated by 0.1 Å when the extra electron is localized on the sites. The diabatic potential surfaces are obtained. The inner reorganization energies are 212.6 and 226.8 kJ mol^?1 for hydroxide and fluoride bridge systems, respectively. The solvent reorganization energies are 28.12 and 31.60 kJ mol^?1 for hydroxide and fluoride bridge systems, respectively. The nuclear frequency factors are 3.17 × 10¹³ and 3.12 × 10¹³ s^?1 for hydroxide and fluoride bridge systems, respectively. The electronic coupling matrix elements are 1.89 and 4.06 kJ mol^?1 for hydroxide and fluoride bridge systems, respectively. The electron‐transfer rates of our calculations are 12.95 and 0.819 M^?1 s^?1 for hydroxide and fluoride bridge systems, respectively. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Optical Properties of Porous Glass Modified with Vanadium(V) Oxide

Porous glasses modified with vanadium(V) oxide were obtained by impregnation with aqueous NH₄VO₃ solutions and by subsequent thermal decomposition of the salt. Changes in the charge-transfer spectra, resulting from an increase in the content of the deposited oxide and from water sorption, and also the possibility of using vanadium-containing glass for visual monitoring of air humidity were considered.     

The synthesis and the molecular structure of hexakis(carbonyl)hexafluoroantimonato(V)tungsten(II) undecafluorodiantimonate(V), [W(CO)6(FSbF5)][Sb2F11

The reaction of tungsten hexacarbonyl, W(CO)6, with antimony(V) fluoride, SbF5, in the conjugate Br?nsted-Lewis superacid HF-SbF5 at 40 degrees C produces quantitatively the salt [W(CO)6(FSbF5)][Sb2F11] as the main product. The observed 2e- oxidation without any loss of CO is unprecedented. The cation [W(CO)6(FSbF5)]+ is seven coordinated with a distorted C2v capped trigonal prismatic structure. [W(CO)6(FSbF5)][Sb2F11] crystallizes in the monoclinic space group P21 (No. 4). a = 8.2051(12) A, b = 16.511(3) A, c = 8.1432(2) A, beta = 111.5967(6) degrees, V = 1025.8(2) A3, Z = 2. Number of reflections measured = 9112, unique 4410. Residuals on F, I > 3 sigma (I): R (Rw) = 0.023 (0.023). In the [W(CO)6(FSbF5)]+ cation the FSbF5 group is very tightly coordinated to tungsten with the bridging fluorine nearly equidistant from W and Sb. The details of the molecular structure are compared to those to polymeric [[Mo(CO)4]2(cis-mu-F2SbF4)3]x[Sb2F11]x reported by us very recently.     

Vielseitige Koordinationschemie von Vanadium(V): Substitutionsreaktionen,Umlagerungen und Kondensationsreaktionen von Oxovanadium(V)‐Komplexen des tripodalen Sauerstoffliganden LOMe− = [η5‐(C5H5)Co{P(OMe)2(O)}3]−

Multifaceted Coordination Chemistry of Vanadium(V): Substitution, Rearrangement Reactions, and Condensation Reactions of Oxovanadium(V) Complexes of the Tripodal Oxygen Ligand L_OMe^? = [η⁵‐(C₅H₅)Co{P(OMe)₂(O)}₃]^? The octahedral oxovanadium(V) complex [V(O)F₂L_OMe] of the tripodal oxygen ligand L_OMe^? = [η⁵‐(C₅H₅)Co{P(OMe)₂(O)}₃]^? reacts with alcohols and phenol with substitution of one fluoride ligand to form alkoxo complexes [V(O)F(OR)L_OMe], R = Me, Et, i‐Prop, Ph. In the presence of water, however, both fluoride ions are substituted and a complex with the composition VO₂L_OMe can be isolated. The crystal structure shows that the oxo‐bridged trimer [{V(O)(L_OMe)O}₃] was synthesized. In the presence of BF₃ the fluoride ligand in the alkoxo‐complex [V(O)F(OEt)L_OMe] can be exchanged for pyridine to yield [V(O)(OEt)pyL_OMe]BF₄. Analogous attempts to exchange the fluoride ligand for tetrahydrofuran and acetonitrile induces a rearrangement reaction that leads to the vanadium complex [V(O)(L_OMe)₂]BF₄. The crystal structure of this compound has been determined. Its ¹H and ³¹P‐NMR spectra show that it is a highly fluxional vanadium complex at ambient temperature in solution. The two tripodal ligands L_OMe^? coordinate the vanadium centre as bidentate or tridentate ligands. The exchange bidentate/tridentate becomes slow on the NMR time scale below about 200 K.     

Preparation of no-carrier-added48V(IV) and48V(V) for biological tracer use

The preparation of no-carrier-added⁴⁸V(IV) and⁴⁸V(V) from a natural titanium target irradiated by a proton beam has been developed. The⁴⁸V recovered from the target by solvent extraction was purified as⁴⁸V(V) with a cation exchange column and then converted to⁴⁸V(IV) by reduction with ethanol. One hour irradiations at 10 A of 18 MeV protons gave approximately 2mCi (a radiochemical yield of 41%) of radiochemically pure and almost salt-free⁴⁸V(IV) and⁴⁸V(V) with high specific activities. They were shown to be suitable for biological tracer use.