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.     

Extraction of Tantalum(V) Impurities from Niobium(V) Fluoride Solutions with Octanol

Fine purification of niobium(V) to remove tantalum(V) by extraction was studied at various compositions of solutions and ratios of phase volumes. Washing of tantalum(V) and niobium(V) extracts with aqueous solutions of their fluorides was considered.     

Niobium(V) Recovery from Titanium-Containing Sulfate Solutions

The separation of niobium(V) from titanium(IV) by extraction with tributyl phosphate containing an amine, followed by precipitation from sulfate media with organic coagulants, was studied.     

Decrease of HF Concentration in Process Solutions before Extractive Separation of Tantalum(V) from Niobium(V)

To improve separation of tantalum(V) from niobium(V) in their extraction from fluoride solutions, different ways for decreasing the fluoride ion concentration in the aqueous phase were tested. The efficiency of decomposition of rare-metal concentrate in continuous countercurrent process with several equilibrium decomposition stages was studied.     

Mechanism of Extraction of Vanadium(V) from Sulfuric Acid Solutions with Di-2-ethylhexylphosphoric Acid

IR and electronic absorption spectroscopies were applied to a study of the mechanism of extraction of vanadium(V) with di-2-ethylhexylphosphoric acid from sulfuric acid solutions.     

State of Rh(III) in Hydrofluoric Acid Solutions

A simple method is developed for synthesizing [Rh(H₂O)₆]F₃. 3H₂O with a yield of 80–90%. ¹⁹F, ¹⁰³Rh, and ¹⁷О NMR spectroscopic studies show that the following three processes simultaneously run in the Rh(III)–HF/K–H₂O system via parallel routes: the formation of mononuclear aquafluoro complexes [Rh(H₂O)₆]³⁺ + F–→ [Rh(H₂O)₅F]²⁺ + H₂O; the formation of aquahydrofluoro complexes [Rh(H₂O)₆]³⁺ + HF₂^-→ [Rh(H₂O)₅HF₂]²⁺ + H₂O; and hydrolysis of the aqua ion followed by coordination of fluoride ion and condensation of the hydroxo species [Rh(H₂O)₆]³⁺ + 2F^– → [Rh(H₂O)₄(OH)F]⁺ + HF → condensation. [Rh(H₂O)₆]³⁺ and [Rh(H2O)5F]²⁺ are the two species making a major contribution to the material balance at high acidity under equilibrium conditions. Parameters of the ¹⁹F NMR spectra of individual complex species are presented.     

The Peculiarities of Extraction of Vanadium(V) by Aminophenols from Sulfuric Acid Solutions

Journal of Solution Chemistry - The effects on the extraction of Vanadium(V) by N-(2-hydroxy-5-nonylbenzyl)-β,β-dihydroxyethylamine of different factors, including pH of the medium,...     

Precipitation Recovery of Rhenium(VII) from Aqueous Solutions with Coagulating Cationic Polyelectrolyte

Rhenium(VII) recovery from dilute aqueous solutions by coprecipitation with VA-212 cationic polyelectrolyte in the presence of nitrate ions was studied.     

Conversion of Tantalum(V), Niobium(V), and Titanuim(IV) Sulfates and Chlorides to Their Fluorides

A process was developed for converting tantalum(V), niobium(V), and titanium(IV) sulfate and chloride to their fluorides in order to improve separation of these elements.     

Adducts of Niobium (V) and Tantalum (V) Halides. XV. Ligand Exchange of the Adducts with Some Phosphoryl Compounds

The ligand exchange MX₅·L + *L?MX₅·*L + L for the octahedral adducts MX₅·L, in an inert solvent (CH₂Cl₂ or CHCl₃) with neutral ligands, proceeds via a dissociative D mechanism when M = Nb, X = Cl and L = phosphoryl compound. A dissociative interchange I_d mechanism is suggested when M = Nb or Ta, and X = F. A first order rate law and positive values for ΔS* (+4 to +14 cal K^?1 mol^?1) are observed for the exchanges on the pentachloride adducts. However, a second order rate law and large negative values for ΔS* (-15 to -24 cal K^?1 mol^?1) are found for the intermolecular neutral ligand exchange (measured by ¹H-NMR.) and for the intramolecular fluorine exchange (measured by ¹⁹F-NMR.) reactions on the pentafluoride adducts. The fluorine exchange is 2 to 5 times faster than the ligand exchange. The exchanges, on the pentachloride and on the pentafluoride adducts, are slowed down with increasing donor strength of the phosphoryl compound.     

Recovery of Lipids from Aqueous Dispersions with Chitosan Solutions

Binding of lipids from aqueous protein-lipid suspensions with a natural polysaccharide, chitosan, was studied in order to develop a procedure for removal of impurities from water. The physicochemical nature of this process was analyzed. The mechanism involving formation of structurally ordered chitosan precipitates, and adsorption and solubilization of lipids with chitosan macromolecules was discussed. The best conditions for defatting of aqueous protein-lipid dispersions with the aid of chitosan were determined.     

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.     

Electron Transfer Spectra of Some Adducts of Niobium (V), Tantalum (V), Titanium (IV) and Zirconium (IV) Halides with Lewis Bases

The electron transfer spectra of adducts of the title metal halides with a series of ligands (nitriles, dialkylchalcogenides, phosphoryl and thiophosphoryl ligands and phosphines) have been studied. The effect of halogen substitution on the halogen metal transitions is discussed by comparing the spectra of the adducts with those of the hexahalometalates. The origin of the two ligand-metal transitions observed in most adducts is discussed, and the splitting of the metal d levels in these almost octahedral adducts is estimated. For each metal halide, the series of adducts with dialkyl chalcogenides show a linear relationship of slope one between the ligand ionisation potential and the ligand-metal charge transfer energy. The ligand optical electronegativities have been estimated.     

Extraction Kinetics of Copper Ions from Aqueous Solutions with a Mixture of Oleic Acid and Triethanolamine

Solvent extraction of copper(II) ions from aqueous solutions with a mixture of oleic acid and triethanolamine in kerosene is studied.     

Gallium(III) Extraction from Hydrochloric Acid Solutions with Diacylated Diethylenetriamine Hydrochloride

Extraction of gallium(III) from hydrochloric acid solutions with hydrochloride of diethylenetriamine [N-(2-aminoethyl)ethane-1,2-diamine] N,N'-diacylated with neodecanoic acid was studied using chloroform as diluent. Gallium(III) can be effectively recovered from 6–10 M HCl solutions and selectively separated from indium(III), aluminum(III), and zinc(II). The concentration constant and thermodynamic parameters of the anion-exchange extraction of gallium(III) from 6 M HCl solutions were evaluated.     

Adducts of Niobium(V) and Tantalum(V) Halogenides. IX. Relative stability of the adducts of the chlorides and bromides with some dialkylchalcogenides

The relative stability of adducts formed by Nb(V) and Ta(V) pentachlorides and bromides with some dimethylchalcogenides and nitriles has been determined by ¹H-NMR. in dichloromethane at ? 60°. The stabilities are explained in terms of the HSAB principle and Jørgensen's symbiotic effect. A good correlation exists between the ionisation potential of the valence p orbital of the chalcogen atom in the ligand and the logarithm of the relative stability of the adduct formed with a given acid.     

Studies on Simultaneous Fluorescence-Spectrophotometric Determination of Ultratrace Niobium(V), Tantalum(V), and Zirconium(IV) Using Partial Least-Squares Algorithm

In the presence of cetyltrimethylammonium bromide, a cationic surfactant, highly sensitive molecular fluorescence reactions occur between Nb(V), Ta(V), and Zr(IV) ions and morin (3, 5, 7, 2′, 4′-pentahydroxyflavone) in acidic medium to form stable ternary micellar complexes. Their λ_ex(max)/λ_em(max)values are 421.0/492.2, 416.2/489.6, and 424.2/507.8 nm, respectively, and their λ_em(max)values are 490.5, 488.6, and 507.2 nm, respectively, at the same fixed λ_exof 420.5 nm, indicating their seriously overlapping fluorescence excitation spectra and fluorescence emission spectra. The linear ranges of their regression calibration curves are 0 to 0.20, 0 to 0.50, and 0 to 0.20 mg/liter, respectively, with 0.5 ng/ml for all of sensitivities. The simultaneous molecular fluorescence-spectrophotometric determination of ultratrace or trace Nb(V), Ta(V), and Zr(IV) without separation was made using a partial least-squares (PLS) algorithm and other algorithms. The optimum PLS computation conditions are wavelength point number of 25 and corresponding wavelength range from 450 to 550 nm oriented from λ_em500 nm to two sides at combined intervals of 2.5 and 5.0 nm at a fixed λ_exof 420.5 nm with an optimum calibration sample number of 14 and respective optimum abstracted factor numbers of 6, 4, and 3. With respect to both accuracy and precision of the obtained results, the PLS algorithm is superior to the ordinary least-squares algorithm.     

Arsenic(V) Removal from Aqueous Solutions by Iron(III) Loaded Chelating Resin

A study of arsenic adsorption using iron(III) loaded chelating resin as adsorbent is presented. The experiments were carried out in batch mode by using aqueous solutions containing 1000 ppm As, and using an iron(III) loaded iminodiacetate resin (LEWATIT TP 207) with sorption capacity of 168 mg Fe/g resin. The equilibrium time for adsorption was found to be one hour under the experimental conditions used. The influence of pH was studied in the range of 0.8÷8.5. The highest arsenic adsorption was found at pH 1.7. Under these conditions the adsorption capacity for As was approximately 60 mg As/g resin.     

Experimental Study of Zirconium(IV) Extraction from Fluoride-Containing Acid Solutions

Zirconium(IV) extraction from acid solutions was studied, and the optimal parameters of the process were found. Extractants for zirconium(IV) recovery from nitric and sulfuric acid solutions in the presence of fluoride ions were selected. The distribution coefficients of zirconium(IV) and fluoride ion were determined.