Extraction recovery of vanadium(V) from sulfuric acid solutions

The IR and electronic absorption spectra of di-2-ethylhexyl hydrogen phosphate (HDEHP) extracts of vanadium(V) and sulfuric acid and of vanadium(V) solutions in sulfuric acid were studied. The composition of the extractable complex was determined, and the equation of vanadium(V) extraction with HDEHP was suggested. The equilibrium constant of vanadium(V) extraction from concentrated sulfuric acid solutions was found.     

Effect of extractant on arsenic(V) recovery from sulfuric acid solutions

Extraction of arsenic(V) from sulfuric acid solutions with various extractants in multistage counter-current extraction-stripping systems was compared. The extraction ability of the extractants studied showed the following order: ENIM 100>TBP=CYANEX 923>2-methylhexanol. The extraction depends significantly on the number of extraction stages and the phase ratios in extraction. The effects of the number of stripping stages and the phase ratio in stripping are less important.     

Vanadium(V) extraction from sulfuric acid solutions

We studied vanadium(V) extraction by di-2-ethylhexylphosphoric acid (DEHPA) from 1.0–12.0 M sulfuric acid. Optimal extraction parameters were determined. IR, ⁵¹V NMR, and electronic spectroscopy was used to determine the stoichiometry of the extracted complex and the reaction equation for vanadium(V) extraction by DEHPA. The equilibrium constant of vanadium(V) extraction by DEHPA was determined.     

Vanadium(V) complexes in sulfuric acid solutions

The ionic state of vanadium(V) is studied spectrophotometrically over a wide range of sulfuric acid concentrations from 1.0 to 16.8 mol/l. Existence regions for monomeric and dimeric vanadium(V) complexes are determined. The equilibrium constant of vanadium(V) dimerization in 12 M H₂SO₄ is determined.     

Ion-exchange recovery of nickel(II) and cobalt(II) from sulfuric acid solutions

Sorption recovery of nickel(II) and cobalt(II) in their joint presence in sulfuric acid solutions was studied on new samples of domestic ion exchangers of CYBBER brand. It was shown that the ion exchangers under study have a high sorption capacity for ions of both nonferrous metals, depending on the structure of a sorbent and on the acidity of a contacting solution. It was found that, after Co(II) and Ni(II) ions are extracted from weak or strong sulfuric acid solutions, they can be effectively eluted from the ion exchangers under study with a 2 M hydrochloric acid solution to an extent of 85–95% (nickel) and 87–95% (cobalt).     

Extraction of vanadium(V) from acid solutions with octyl alcohol isomers

Vanadium(V) extraction with octyl alcohol isomers from acid solutions was studied. Two areas are determined, wherein the vanadium(V) extraction in relation to acidity of the aqueous phase is maximal. The opposite effects of temperature on the extraction are found. The mechanism of the vanadium(V) extraction with high molecular weight alcohols from weakly acid solutions was suggested.     

Effect of the structure of octanols on their extraction capacity for rhenium(VII) in sulfuric acid solutions

Extraction of Re(VII) from sulfuric acid solutions with isomers of octanol was studied.     

Kinetic and mechanistic aspects for the tartaric acid oxidation by vanadium(V) in sulfuric acid medium

Tartaric acid oxidation by vanadium(V) in sulfuric acid medium was investigated spectrophotometrically at 760 nm and 30°C by appearance of the vanadium(IV), as vanadyl. The reaction rate was determined under pseudo-first-order conditions with an excess of hydroxyacid over the oxidant concentration. The oxidation showed a first-order dependence with respect to vanadium(V) concentration and fractional orders with respect to tartaric acid and sulfuric acid concentrations, with no control and with constant ionic strength. The reaction rate is enhanced by an increase of ionic strength, and slightly reduced by a decrease of the dielectric constant of the medium. The activation parameters were calculated based on the rate constants determined in the 293 to 313 K interval. The proposed oxidation mechanisms and the derived rate laws are consistent with the experimental rate laws. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 55–61, 1998.     

Extraction recovery of vanadium(IV) from acid sulfate solutions with di-(2-ethylhexyl)phosphoric acid

Extraction of vanadium(IV) with di-(2-ethylhexyl)phosphoric acid from acid sulfate solutions in the presence of sodium sulfate was studied. The composition of the complex being extracted was found, and the equation of the extraction reaction was determined. The equilibrium constant of the reaction by which vanadium(IV) is extracted with di-(2-ethylhexyl)phosphoric acid was found by taking into account the complexation of vanadium(IV) in acid sulfate solutions.     

Citric acid oxidation by vanadium(V) in sulfuric acid medium: Kinetic and mechanistic study

The citric acid oxidation by vanadium(V) in sulfuric acid medium at 303 K is reported. The reaction rate was determined spectrophotometrically by monitoring the formation of vanadium(IV) at 760 nm. The oxidation showed a first‐order dependence with respect to vanadium(V) concentration and fractional order with respect to citric acid concentrations, with no control and with constant ionic strength. The reaction is also first order with respect to sulfuric acid concentration with no control and of fractional order at constant ionic strength. The reaction rate is enhanced by an increase of ionic strength and increased by a decrease of the dielectric constant. The activation parameters were calculated based on the rate constants determined in the 293 to 313 K interval. The proposed oxidation mechanisms and the derived rate laws are consistent with the experimental rate laws. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 566–572, 2000     

Hydrolytic precipitation of calcium polyvanadates from vanadium(IV) and vanadium(V) solutions

The effect of VO²⁺ ions on the composition and kinetics of calcium polyvanadate precipitation from solutions with 1.5 ≤ pH ≤ 9 at 80–90°C has been studied. For 1,5 ≤ pH < 3 and V⁴⁺/V⁵⁺ = 0.11–9, the precipitated compounds have the general formula Ca _x V _y ⁴⁺ V _12?y ⁵⁺ O_31?δ · nH₂O (0.8 ≤ x ≤ 1.06, 2 ≤ y ≤ 3, 0.94 ≤ δ ≤ 1.5). The maximum vanadium(IV) proportion (y = 3) in the precipitates is achieved when V⁴⁺/V⁵⁺ = 0.5?1.0 in the solution and pH is 3. Polyvanadate precipitation at pH 1.7 has a long induction period (up to 30 min), which is not observed for V⁴⁺/V⁵⁺ > 0.1. Precipitation in solutions with pH 3 occurs only when VO²⁺ ions are added, with a maximum rate near V⁴⁺/V⁵⁺ = 0.2 and in presence of chloride ions. The processes are controlled by a secondorder reaction on the polyvanadate surface.     

Recovery of rhenium(VII) with triisooctylamine from sulfuric acid solutions

Extraction recovery of rhenium(VII) with triisooctylamine from model sulfuric acid solutions was studied. The effect of the composition of the organic and aqueous phases on the recovery of rhenium(VII) was analyzed, and the composition of rhenium(VII) complexes in the organic phase was determined. The possibility of effective re-extraction of rhenium(VII) from triisooctylamine with ammonia solutions was demonstrated.     

State of rhodium(III) in sulfuric acid solutions

The formation of rhodium(III) sulfate complexes under moderately rigorous temperature conditions was studied by ¹⁰³Rh and ¹⁷O NMR spectroscopy. The complexes [Rh₂(μ-SO₄)₂(H₂O)₈]²⁺, [Rh₂(^*μ-SO₄)(H₂O)₈]⁴⁺, and [Rh₃(μ-SO₄)₃(μ-OH)(H₂O)₁₀]²⁺ were found to be the most stable species in aged solutions.     

Colorimetric studies of vanadium(V) with organic acids

Summary The intense yellow colour developed by adding an excess of organic acids (acetic, succinic, malonic, benzoic, phthalic) to an ammonium metavanadate solution is employed for the colorimetric determination of vanadium. On the other hand, the decrease in the intensity of the colour developed by acetic acid and metavanadate by oxalic and citric acids can be used for an indirect colorimetric determination of these acids.

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Zusammenfassung Die intensive Gelbfärbung, die Ammoniummetavanadat mit organischen Säuren (Essig-, Bernstein-, Malon-, Benzoe-, Phthalsäure) bildet, kann zu einer colorimetrischen Vanadiumbestimmung benutzt werden. Andererseits kann die Schwächung der aus Metavanadat und Essigsäure gebildeten Gelbfärbung durch Oxal- und Citronensäure zu einer indirekten colorimetrischen Bestimmung dieser Säuren herangezogen werden.

     

Extraction of vanadium(V) by N′,N′-dialkylhydrazides of carboxylic acids from acidic solutions

Extraction of vanadium(V) with solutions of 2-ethylhexanoic acid N′,N′-dialkylhydrazides in kerosene from acidic media was studied. The optimal extraction conditions were determined depending on the concentrations of H₂SO₂, HCl, and the extraction agent; the composition of the recovered complexes was proposed. The conditions for back-extraction of vanadium(V) from the organic phase were studied. It was found that benzoic acid N′,N′-diheptylhydrazide did not recover vanadium(V) from acidic media.     

Binuclear vanadium(V) and vanadium(IV,V) complexes of dihydrocaffeic,caffeic and ferulic acids

Summary Binuclear complexes of dihydrocaffeic, caffeic and ferulic acids with vanadium were prepared and studied. The suggested square-pyramidal structures with catecholic-type coordination are supported by various spectroscopic, magnetic and thermogravimetric data.     

Complexation of Rh(III) in diluted sulfuric acid solutions

Complex formation in a system Rh(III)-H₂SO₄-H₂O was studied by the ¹⁰³Rh and ¹⁷O NMR spectroscopy at room temperature. The formation of two interrelated systems of mononuclear and polynuclear complexes was established in the above solutions. The predominant species in the first system is a labile ionic pair {Rh(H₂O) ₆ ³⁺ SO ₄ ^2? }⁺, while in the second system, two inert binuclear complexes [Rh₂(μ-SO₄)₂(H₂O)₈]²⁺ and [Rh₂(μ-SO₄)(μ-OH)(H₂O)₈]³⁺ prevail.     

Stability of tetra(tetramethylene)tetraazaporphine in sulfuric acid solutions

In sulfuric acid solutions tetra(tetramethylene)tetraazaparphine undergoes hydrolytic destruction. The reaction is first order in the porphyrin concentration and second order in the hydronium ion concentration.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 629–633, May, 1987.     

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(-)).     

Joint electrolytic deposition of vanadium(V) and chromium(III) oxides from aqueous sulfate solutions

The conditions of the joint electrolytic deposition of vanadium(V) and chromium(III) oxides from mixed sulfate solutions at different concentration ratios of the main components were studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1795–1798.Original Russian Text Copyright © 2004 by Nagirnyi, Apostolova, Baskevich, Shembel.