Selective Extraction and Spectrophotometric Determination of Vanadium(V) with N-Hydroxy-N-p-chlorophenyl-N′-(2-methyl-5-chloro)phenyl-p-toluamidine Hydrochloride and Various Monobasic Carboxylic Acids

Abstract

N-Hydroxy-N-p-chlorophenyl-N′-(2-methyl-5-chloro)phenyl-p-toluamidine hydrochloride (HCPMCPTH), a newly synthesized bidentate chelating agent, reacts with vanadium(V) in the presence of monobasic carboxylic acids to give blue-violet water-insoluble adducts. The adducts have been extracted into various organic solvents such as chloroform, benzene, and carbon tetrachloride, and employed for the spectrophotometric determination of vanadium(V) and its separation from diverse ions. Investigations of the vanadium-HCPMCPTH-carboxylic acid complexes by spectrophotometric and solvent extraction techniques showed that the complex had the composition VO(OAm)₂OH.HOOCR (where HOAm = hydroxyamidine and HOOCR = carboxylic acid). The molar absorptivity and wavelength of maximum absorption of the mixed complex depend on the nature of the carboxylic acid used.     

Para‐substituted 1‐Phenyl‐3‐methyl‐4‐aroyl‐5‐pyrazolones as Selective Extractants for Vanadium(V) from Acidic Chloride Solutions

Abstract

Para‐substituted 4‐aroyl derivatives of 1‐phenyl‐3‐methyl‐5‐pyrazolones (HX), namely, 1‐phenyl‐3‐methyl‐4‐(4‐fluorobenzoyl)‐5‐pyrazolone (HPMFBP) and 1‐phenyl‐3‐methyl‐4‐(4‐toluoyl)‐5‐pyrazolone (HPMTP) were synthesized and examined with regard to the extraction behavior of multivalent metal ions such as magnesium(II), aluminum(III), titanium(IV), vanadium(V), chromium(III), manganese(II), iron(II), and iron(III) that are present in titania waste chloride liquors. For comparison, studies have also been carried out with 1‐phenyl‐3‐methyl‐4‐benzoyl‐5‐pyrazolone (HPMBP). The results demonstrate that vanadium(V) and iron(III) are extracted into chloroform with 4‐aroyl‐5‐pyrazolones as VO₂X · HX and FeX₃, respectively. On the other hand, magnesium(II), aluminum(III), titanium(IV), chromium(III), manganese(II), and iron(II) were not found to be extracted into the organic phase. The equilibrium constants of vanadium(V) and iron(III) with various 4‐aroyl‐5‐pyrazolones follow the order HPMFBP>HPMBP>HPMTP, which is in accordance with their pKa values. The selectivity between vanadium(V) and iron(III) increases with increasing hydrochloric acid concentration. Further, it is clear from the results that iron(III) is not getting extracted above 1.0 mol dm^?3 hydrochloric acid solution. The electronic and IR spectra of the extracted complexes of vanadium(V) and iron(III) were used to further clarify the nature of the extracted complexes. The potential of these reagents for the selective extraction and separation of vanadium(V) from titania waste chloride liquors has also been discussed.     

Distribution Studies of Metal-8-quinolinol Chelates in a Nonaqueous System

Abstract

This investigation was concerned with the determination of the influence of water on the distribution of several metal-8-quinolinol chelates between nitromethane and 1-decanol. These observations were utilized to describe the general equilibria involved in the extraction processes.

The distribution ratios (nitromethane/1-decanol) of bis(8-quinolinolo)-dioxouranium(VI)-8-quinolinol, bis(8-quinolinolo)dioxouranium(VI), tris-(8-quinolinolo)iron(III), and bis(8-quinolinolo)zinc(II) in dry solvents were determined by visible and atomic absorption spectrophotometry to be 0.95, 0.92, 1.90 and 0.11, respectively. The extraction into the 1-decanol phase increased with the number of unfilled coordination sites of the metal, indicating that the extractions were proceeding by solvation of the metal chelates.

The influence of water was attributed primarily to hydrolysis of the chelates in nitromethane, and the magnitude of this effect was correlated to the respective metal chelate formation constants. The chelates were found to be resistant to hydrolysis in 1-decanol.     

Liquid-Liquid Extraction of Vanadium(V) and Niobium(V) with Tris(2-ethylhexyl)phosphate: Mutual Separation of Vanadium(V), Niobium(V), and Tantalum(V), and Analysis of Steel Samples

Abstract

Tris(2-ethylhexyl)phosphate (TEHP) dissolved in toluene is used for selective extraction of vanadium(V) and niobium(V) from hydrochloric and hydrobromic acid solution. Vanadium is determined spectrophotometrically after backextraction from TEHP, whereas unstripped niobium is determined in the TEHP phase with thiocyanate. The probable extractable species is VOCl₃·2TEHP or NbOCl₃·2TEHP/NbOBr₃·2TEHP. The method permits mutual separation of vanadium(V), niobium(V), and tantalum(V), and provides analysis of vanadium and niobium in alloys with a high degree of accuracy and precision.     

Solvent extraction separation of titanium(IV), vanadium(V) and iron(III) from simulated waste chloride liquors of titanium minerals processing industry by the trialkylphosphine oxide Cyanex 923

The solvent extraction of magnesium(II), aluminium(III), titanium(IV), vanadium(V), chromium(III), manganese(II) and iron(III) from hydrochloric acid solutions has been investigated using the trialkylphosphine oxide Cyanex 923 (TRPO) in kerosene as extractant. The results demonstrate that titanium(IV), vanadium(V) and iron(III) are extracted into kerosene as TiOCl₂·2TRPO, VO₂Cl·TRPO and HFeCl₄·2TRPO, respectively. On the other hand magnesium(II), aluminium(III), chromium(III) and manganese(II) are not extracted with TRPO from hydrochloric acid solutions (1.0–4.0 mol dm^?3) under the experimental conditions. IR spectral studies of the extracted complexes were further used to clarify the nature of the extracted complexes. The effect of the diluent on the extraction of titanium(IV), vanadium(V) and iron(III) has been studied and correlated with the dielectric constant. The loading capacity of the TRPO system has been evaluated and the potential for the separation and recovery of titanium(IV), vanadium(V) and iron(III) from simulated waste chloride liquors of the titanium minerals processing industry has been assessed. Copyright © 2004 Society of Chemical Industry     

Studies on Pollutants. VIII. Trace Analysis of Vanadium with N-p-Methoxyphenyl-2-furohydroxamic Acid

Abstract

A highly sensitive, selective, and rapid method for the spectrophotometric determination of trace amounts of vanadium(V) is described. Vanadium(V) is extracted from 4–8 M hydrochloric acid solutions as its violet complex with N-p-methoxyphenyl-2-furohydroxamic acid (MFHA) in chloroform. The extract shows maximum absorbance at 545 run (E = 7.3 × 10³ L.mole^?1 cm^?1) and obeys Beer's law over the range 0–12 ppm of vanadium; Sandell's sensitivity being 0.007 μg/cm². The method has been applied for the analysis of vanadium in pond water, rock phosphates, and steels.     

Thin-Layer Chromatography of Metal Ions Complexed with Anils. Y. Detection,Separation, and Determination

Abstract

p-Diethylaminoanil of phenylglyoxal, a bidentate ligand, was used for complexation with Hg(II), UO₂(II), Au(III), Pt(IV), Mg(II), Bi(III), Sb(III), and Be(II) ions. The chelates were characterized by their analysis, molar conductance, and infrared spectra. TLC detection, separation, and determination of these complexes on starch-bound silica gel layers were studied. Long persisting dark colors of the complexes rendered the spots self-descernible and no locating agent was required. A maximum of four complexes could be resolved and identified. Errors in determinations and maximum separation limits were also deduced.     

Solvent extraction separation of vanadium(V) from multivalent metal chloride solutions using 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester

The solvent extraction behaviour of vanadium(V) from hydrochloric acid solutions has been investigated using 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester (EHEHPA ≡ HX) in kerosene as an extractant. For comparison, extraction studies have also been carried out with vanadium(IV). The results demonstrate that the extraction of vanadium(V) follows the cation exchange mechanism: where (HX)₂ refers to the dimeric form of EHEHPA. On the other hand, two dimeric molecules of EHEHPA were found to be involved in the extracted complex of vanadium(IV): The equilibrium constants of the above extracted complexes have been calculated and found to be K_ex,V(V) = 3.14 and K_ex,V(IV) = 0.32. The effect of the nature of the diluent on the extraction of vanadium(V) with EHEHPA has been studied and correlated with the dielectric constants. IR spectral studies of the extracted complex were used to further clarify the nature of the extracted complex. The separation and recovery possibilities of vanadium(V) from other associated metal ions, viz magnesium(II), aluminium(III), titanium(IV), chromium(III), manganese(II) and iron(III), which are present in the waste chloride liquors from the processing of titanium minerals, are also discussed. © 2002 Society of Chemical Industry     

Utilization of Steric Hindrance at the Metal Site in Separation of Copper(ll) Chelates

Abstract

The chromatographic behavior of copper(II) chelates differing in the arrangement of their alkyl chains is influenced by the steric hindrance at the copper(II) site. This hindrance prevents the solvent molecules from coordinating on the remaining coordination positions, and thus R_F values of chelates decrease with increasing compression at the copper(II) site.     

The Use of Tri-n-octylamine for the Separation of Vanadium(V) from Acidic Sulfate Uranium Leach Liquors

Abstract

Extraction of vanadium(V) from acidic sulfate solutions by a mixture of tri-n-octylamine and tributylphosphate (used as modifier) dissolved in kerosene has been studied. The distribution coefficient of vanadium(V) increases with an increase in pH and vanadium(V) concentration. The presence of iron(III) in aqueous solution does not have any appreciable effect, while large amounts of sulfate ion depress the distribution coefficient. Uranium(VI) has a distribution different from vanadium(V). Based upon these results, a scheme for the separation of vanadium(V) from uranium leach liquors has been made and checked experimentally.     

Fenton reactions in lipid phases

Metal catalysis of membrane lipid oxidation has been thought to occur only at cell surfaces. However, conflicting observations of the pro-oxidant activity of ferric (Fe³⁺) vs ferrous (Fe²⁺) forms of various chelates have raised questions regarding this dogma. This paper suggests that the solubilities of iron complexes in lipid phases and the corresponding abilities to initiate lipid oxidation there, either directly or via Fenton-like production of reactive hydroxyl radicals, are critical determinants of initial catalytic effectiveness. Partitioning of Fe³⁺ and Fe²⁺ complexes and chelates into bulk phases of purified lipids was quantified by atomic absorption spectroscopy. mM solutions of iron salts partitioned into oleic acid at levels of about micromolar. Ethylenediamine tetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) chelates were somewhat less soluble, while adenosine diphosphate (ADP) chelates, and ferrioxamine were soluble as chelates at greater than 10⁻⁵ M. Solubilities of all iron compounds in methyl linoleate were 10- to 100-fold lower. To determine whether Fenton-like reactions occur in lipid phases, H₂O₂ and either Fe²⁺ or Fe³⁺ and a reducing agent were partitioned into the lipid along with the spintrap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), and free radical adducts were recorded by electron paramagnetic resonance (EPR). Hydroxyl radicals (OH^.) adducts were observed in oleic acid, but in lipid esters secondary peroxyl radicals predominated, and the presence of OH^. adducts was uncertain. Presented at the symposium “Free Radicals, Antioxidants, Skin Cancer and Related Diseases” at the 78th AOCS Annual Meeting in New Orleans, LA, May 1987     

Preconcentration and speciation of vanadium by three phases liquid–liquid microextraction prior to electrothermal atomic absorption spectrometry

We developed a new method three phase liquid–liquid microextraction (TPLLME) for simultaneous speciation of vanadium. This efforts were launched to know the species and aqueous transport chemistry of the binary V-(1-(2-Pyridylazo)-2-naphthol) complex across the interface of the three phases. Various analytical parameters were optimized. The limit of detection (LOD) was 0.034 μg L⁻¹ and 0.028 μg L⁻¹ for V(V) and V(IV) with preconcentration factor of 100. Relative standard deviation (RSD) was found 4.32% for V(V) and 4.22% for V(IV). The proposed method was applied to species of vanadium successfully in sea water and tap water samples. The method was also applied to certified reference material and food samples for total vanadium determination.     

Bifunctional redox flow battery: 2. V(III)/V(II)-l-cystine(O2) system

A new bifunctional redox flow battery (BRFB) system, V(III)/V(II)—l-cystine(O₂), was systematically investigated by using different separators. It is shown that during charge, water transfer is significantly restricted with increasing the concentration of HBr when the Nafion 115 cation exchange membrane is employed. The same result can be obtained when the gas diffusion layer (GDL) hot-pressed separator is used. The organic electro-synthesis is directly correlated with the crossover of vanadium. When employing the anion exchange membrane, the electro-synthesis efficiency is over 96% due to a minimal crossover of vanadium. When the GDL hot-pressed separator is applied, the crossover of vanadium and water transfer are noticeably prevented and the electro-synthesis efficiency of over 99% is obtained. Those impurities such as vanadium ions and bromine can be eliminated through the purification of organic electro-synthesized products. The purified product is identified to be l-cysteic acid by IR spectrum. The BRFB shows a favorable discharge performance at a current density of 20 mA cm⁻². Best discharge performance is achieved by using the GDL hot-pressed separator. The coulombic efficiency of 87% and energy efficiency of about 58% can be obtained. The cause of major energy losses is mainly associated with the cross-contamination of anodic and cathodic active electrolytes.     

Vanadium staining in fired clay bricks

Abstract

This paper reports on a series of efflorescence tests and instrumental techniques that have been used to determine the nature and mechanism of vanadium staining, and the effects of additions of magnesite, calcite, and fluorspar to the brick mix to eliminate the problem. Scanning electron microscopy, electron probe microanalysis, inductively coupled mass spectrometry (with laser ablation attachment), and X-ray photon spectrometry have been used to more fully understand the elemental composition, oxidation states, and formation of vanadium stains in fired clay bricks. It was found that the stains consist of V, K, Na, Mo, S, and O. Vanadium +4 compounds form initially within the brick and are slowly oxidised to vanadium +5 compounds as the water transports the potassium and sodium salts to the brick surface. X-ray diffraction led to a reasonably successful search match for a KVO(SO₄)₂ phase for the stains. Evolved gas analysis showed loss of vanadium compounds between 700 and 900° C which are most likely VF₃ and VCl₄. Inductively coupled plasma spectrometry laser ablation studies on thin sections of brick showed areas of glassy phases corresponding to the agglomeration of Mg/V/Al/Si and Mg/Al/Si. The increased alkalinity of magnesia and the comparable sizes of V⁴⁺ and Mgions are driving forces for locking vanadium into what is otherwise an acidic glassy phase. The addition of 1 wt-% magnesite to the brick mix led to fired products on a commercial scale that are free from vanadium staining.     

Physicochemical studies on square-planar Cu(II), Ni(II) and Co(II) chelate polymers

Chelate polymers of Cu(II), Ni(II) and Co(II) with bis-oxime of 5,5′-methylene bis(salicylaldehyde) have been prepared. The square-planar structure of the complexes was determined on the basis of infrared and electronic spectral measurements in conjunction with magnetic susceptibility measurements. The thermal stability of the chelates, obtained from the TG thermograms has the following order: Co(II) and Ni(II) chelates are found to increase their coordination number by interaction with pyridine at right angles to the plane of the parent molecule. The resulting complex is found to have octahedral structure. The ligand-field and nephelauxetic parameters have been determined from the spectra, using ligand-field theory of spin-allowed transitions which are found consistent with six-coordinate structure for these adducts.     

Oxidation of butane over vanadium–phosphorus oxides of P/V≥2

Two mixed oxides of vanadium and phosphorus, with phosphorus to vanadium atomic ratio (P/V) about 2 and 2.4, were studied as catalysts for selective oxidation of butane to maleic anhydride. The sample with P/V about 2 was poorly crystalline, contained a small amount of V(V), and oxidized butane to maleic anhydride with about 50% selectivity. The sample with P/V about 2.4 contained well crystalline VO(PO₃)₂ phase, but it deactivated with time-on-stream with the formation of V(PO₃)₃. The results suggested that the two samples differed greatly in their rates of oxidation of the vanadium ions.     

Synthesis,characterization, and antimicrobial studies of newly developed metal‐chelated epoxy resins

A series of novel metal‐chelated epoxy resins have been synthesized by the condensation of epichlorohydrin (1‐chloro‐2, 3 epoxy propane) with bisphenolic metal chelates in alkaline medium. The bisphenolic chelates were initially prepared by the reaction of 3‐formyl‐4, 4′‐dihydroxy diphenyl methane and diamine (ethylenediamine/o‐phenylenediamine) in 1:2 molar ratio and then with Cu(II), Ni(II), and Co(II) acetate. The metal‐chelated epoxy resins were characterized by various instrumental techniques, such as elemental analysis, DSC and TGA, electronic, FTIR, ¹H‐NMR, and ¹³C‐NMR spectra. The physicochemical properties, viz., epoxide equivalent weight (eq/100 g), hydroxyl value (eq/100 g), refractive index, specific gravity, and specific viscosity were measured by standard procedures. The antimicrobial activities of these chelated resins were screened against Escherichia coli, Staphylococcus aureus, Bacillius subtilis (bacteria), and Candida albicans, Mucor species (yeast) by using agar well diffusion method. All the polymeric chelates show promising antimicrobial activities. Among these polymeric chelates (ERPD)‐Cu(II) shows better antimicrobial activities, which can be attributed to higher stability constant of Cu(II) chelate than others. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1347–1355, 2006     

Determination of Water Associated with Some Iron Acetylacetonates and Nickel Glyoximes Extracted into CHCI3

Abstract

Utilizing the Karl Fischer titration technique for the quantitative determination of water, the number of water molecules associated with a molecule of chelate when extracted from water into chloroform was determined for five chelates in the acetylacetone and dimethylglyoxime types. In this investigation no increase in the number of associated water molecules was observed as the bulkiness of the ligand was increased by the substitution of electron-withdrawing groups for methyl groups on the ligand, nor was any increase noted when the metal ion in the chelate was less sterically hindered to the approach of water molecules than in the phenanthroline chelates. The fact that the chelate contains hydrogen-bonded sites does not appear to affect the number of water molecules associated with the chelates investigated here.     

Addition Reactions to Methylenecyclopropanes II: Electrophilic Additions of Diphenylmethylenecyclopropane

A number of addition reactions to diphenylmethylenecyclopropane (II) have been studied. Bromination and CF₃COOH addition in CH₃Cl₂ proceeded with ring-opening and gave the homoallylic adducts III and VI. On the other hand bromination in glyme and water gave both unrearranged and rearranged products, III and V. Reactions with NBS in the same solvent system gave the unrearranged bromohydrin V. Oxymercuration and hydroboration proceeded without ring-cleavage, the mercury and boron attacking mainly β- to the phenyl groups. Two cyclopropylmercury compounds VII and IX were isolated and characterized.