Mechanism Of Vanadium Research Articles

Unraveling the mechanism of vanadium self-intercalation in 1T-VSe2: atomic-scale evidence for phase transition and superstructure model for intercalation compound

Self-intercalation is an efficient strategy for tailoring the property of layer structured materials like transition metal dichalcogenides (TMDCs), while the associated kinetics and mechanism remain scarcely explored. In this study, we investigate the atomic-scale dynamics and mechanism of vanadium (V) self-intercalation in multi-layer 1T-VSe2 using in situ high resolution scanning transmission electron microscopy. The results reveal that the self-intercalation of V induces structural transformation of pristine VSe2 into three V-enrich intercalated compounds, i.e. V5Se8, V3Se4 and VSe. The self-intercalated V follows an ordered arrangement of 2×2 , 2×1 , and 1×1 within the interlayer octahedral sites, corresponding to an intercalation concentration of 25%, 50% and 100% in V5Se8, V3Se4 and VSe, respectively. The V intercalants induced lattice distortions to the host 1T-VSe2 such as the dimerization of neighboring lattice V is observed experimentally, which are further supported by density functional theory (DFT) calculations. Finally, a superstructure model generalizing the possible structures of self-intercalated compounds in layered TMDCs is proposed and then validated by the DFT determined formation energy landscape. This study provides comprehensive insights on the kinetics and mechanism of the self-intercalation in layered TMDC materials, contributing to the precise control for the structure and stoichiometry of self-intercalated TMDC compounds.

Adsorption property and mechanism of vanadium(V) by supported bifunctionalized ionic liquid

This study aims to investigate the adsorption behavior of supported bifunctionalized ionic liquids (SBILs) polystyrene [1-butyl-3-methylimidazolium][bis(2,4,4-trimethylpentyl)phosphinate] (PS[C4mim][C272]) for vanadium(V). PS[C4mim][C272] was synthesized through anion exchange using [PS][C4mim][Cl] and bis(2,4,4-trimethylpentyl) phosphine acid (Cyanex272) as precursors. The prepared SBILs were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to illustrate the successful loading of [C272]− onto SBILs. The results demonstrate that PS[C4mim][C272] adsorb V(V) by ionic conjugation. Under the preferred adsorption conditions, the equilibrium adsorption capacity of PS[C4mim][C272] reached 303.36 mg/g. The adsorption behavior of PS[C4mim][C272] for V(V) is more consistent with the Langmuir isotherm model, indicating that V(V) is adsorbed as monolayer. The adsorption process of PS[C4mim][C272] is consistent with the pseudo-second-order kinetic adsorption model, implying that the adsorption process is mainly chemical adsorption. Thermodynamics showed that the adsorption process of PS[C4mim][C272] was endothermic and spontaneous. The desorption of loaded V(V) and regeneration of PS[C4mim][C272] can be accomplished using 3 mol/L NH3·H2O solution one step. After 10 cycles, the adsorption capacity of PS[C4mim][C272] remains 96.58% of the initial value, implying the perfect adsorption stability of PS[C4mim][C272]. Meanwhile, PS[C4mim][C272] could effectively separate vanadium(V) from Fe(III) and Al(III) ions.

Mechanism of Vanadium on Microstructure and Properties of Titanium Alloy by Laser Melting Deposition

Mechanism of Vanadium on Microstructure and Properties of Titanium Alloy by Laser Melting Deposition

Mechanism of vanadium(IV) resistance of the strains isolated from a vanadium titanomagnetite mining region.

Microbial treatment for vanadium contamination of soils is a favorable and environment-friendly method. However, information of the resistant mechanism of the strains in soils to vanadium, especially to tetravalent vanadium [vanadium(IV)], is still limited. Herein, potential of the vanadium(IV) biosorption and biotransformation of the strains (4K1, 4K2, 4K3 and 4K4) which were capable of tolerating vanadium(IV) was determined. For biosorption, the bioadsorption and the bioabsorption of vanadium(IV) occur on the bacterial cell wall and within the cell, respectively, were taken into consideration. Comparison of the vanadium(IV) adsorbed on the bacterial cell walls and remained in the cells after sorption indicated the major bacterial vanadium(IV) sorption role of the bioadsorption which was at least one order of magnitude higher than the bioabsorption amount. Isotherm study using various isotherm models revealed a monolayer and a multilayer vanadium(IV) biosorption by 4K2 and the others (4K1, 4K3 and 4K4), respectively. Higher biosorption was observed in acidic conditions than in alkaline conditions, and the maximum biosorption was 2.41, 9.35, 7.76 and 8.44mgg-1 observed at pH 6 for 4K1, at pH 3 for 4K2, and at pH 4 for 4K3 and 4K4, respectively. At the present experimental range of the initial vanadium(IV) concentration, optimal biosorption capacity of the bacteria was observed at the vanadium(IV) level of 100-250mgL-1. Different biotransformation level of vanadium(IV) in soils by the stains was observed during a 28-d pot incubation of the soils mixed with the strains, which can be attributed to the discrepancy of both soil properties and bacterial species. Present study can help to fill up the gaps of the insufficient knowledge of the vanadium(IV) resistant mechanism of the strains in soils.

Separation characteristics of vanadium from leach liquor of red mud by ion exchange with different resins

Resin D201, D314 and 717 were compared for their efficiency to extract vanadium from hydrochloric acid leaching solution of red mud. The adsorption parameters were investigated in details by using the three resins. The separation characteristics and mechanism of vanadium were analyzed with infrared spectroscopy and adsorption kinetics. More than 99% of vanadium was selectively adsorbed by using resin D201 at pH value of 2.0, flow speed of 6m3/h·m3 resin, resin D314 at pH value of 3.0, flow speed of 4.8m3/h·m3 resin, and resin 717 at pH value of 5.0, flow speed of 7.92m3/h·m3 resin, respectively. The maximum loading of vanadium by using resin D201 was more than resin 717 and D314. The vibration peak of functional group on the resins increased after adsorption of vanadium from the leaching solution. The adsorption process of vanadium was according with the pseudo-second adsorption kinetic model.

Successive C1-C2 bond cleavage: the mechanism of vanadium(v)-catalyzed aerobic oxidation of d-glucose to formic acid in aqueous solution.

Vanadium(v)-catalyzed aerobic oxidation in aqueous solution shows high selectivity in the field of C-C bond cleavage of carbohydrates for chemicals with less carbon atoms. However, the pathway of C-C bond cleavage from carbohydrates and the conversion mechanism are unclear. In this work, we studied the pathway and the mechanism of d-glucose oxidation to formic acid (FA) in NaVO3-H2SO4 aqueous solution using isotope-labeled glucoses as substrates. d-Glucose is first transformed to FA and d-arabinose via C1-C2 bond cleavage. d-Arabinose undergoes similar C1-C2 bond cleavage to form FA and the corresponding d-erythrose, which can be further degraded by C1-C2 bond cleavage. Dimerization and aldol condensation between carbohydrates can also proceed to make the reaction a much more complicated mixture. However, the fundamental reaction, C1-C2 bond cleavage, can drive all the intermediates to form the common product FA. Based on the detected intermediates, isotope-labelling experiments, the kinetic isotope effect study and kinetic analysis, this mechanism is proposed. d-Glucose first reacts with a vanadium(v) species to form a five-membered-ring complex. Then, electron transfer occurs and the C1-C2 bond weakens, followed by C1-C2 bond cleavage (with no C-H bond cleavage), to generate the H3COO˙-vanadium(iv) complex and d-arabinose. FA is generated from H3COO˙ that is oxidized by another vanadium(v) species. The reduced vanadium species is oxidized by O2 to regenerate to its oxidation state. This finding will provide a deeper insight into the process of C-C bond cleavage of carbohydrates for chemical synthesis and provide guidance for screening and synthesizing new highly-efficient catalyst systems for FA production.

Preparation of Highly Pure Vanadyl Sulfate from Sulfate Solutions Containing Impurities of Iron and Aluminum by Solvent Extraction Using EHEHPA

The preparation of highly pure vanadyl sulfate from sulfate solutions containing impurities of iron and aluminumwas investigated by solvent extraction with 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (EHEHPA) and tri-n-butyl phosphate (TBP) as the phase modifier. The extraction and stripping conditions of vanadium (IV) and its separation from iron and aluminum were optimized. Under the optimal extraction conditions, the extraction of vanadium (IV) and iron were 68% and 53%, respectively, while only 2% aluminum was extracted in a single contact, suggesting good separation of vanadium (IV) from aluminum. Sulfuric acid solution was used for the stripping. Nearly 100% vanadium (IV) and 95% aluminum were stripped, while only 10% iron was stripped under the optimal stripping conditions in a single contact, suggesting good separation of vanadium (IV) from iron. After five stages of extraction and stripping, highly pure vanadyl sulfate containing 76.5 g/L V (IV) with the impurities of 12 mg/L Fe and 10 mg/L Al was obtained, which is suitable for the electrolyte of a vanadium redox flow battery. Organic solution was well regenerated after stripping by oxalic acid solution to remove the remaining iron. The mechanism of vanadium (IV) extraction using EHEHPA was also discussed based on the Fourier transform infrared spectroscopy (FT-IR) analysis.

A novel synergistic extraction method for recovering vanadium (V) from high-acidity chloride leaching liquor

Abstract A selective synergistic extraction process for recovering vanadium (V) from the high-acidity chloride leaching liquor was proposed. Vanadium (V) extraction from the simulated high-acidity leaching liquor with numerous impurities using a mixed extractant consisting of tricaprylmethylammonium chloride (Aliquat 336) and tri-n-butyl phosphate (TBP) was studied while obvious synergism was found. According to synergistic enhancement coefficient and physical property of organic phase, the suitable extractant composition was the volume ratio of Aliquat 336 to TBP 1:4. The vanadium (V) extraction increased sharply as HCl concentration increased from 1.01 mol/L to 4.13 mol/L. Under the optimum extraction conditions (extractant concentration of 50 vol%, 1 min, 25–30 °C, and phase ratio (O/A) of 1:1), the vanadium extraction with three stages was above 90.0%. Almost no other impurity ions, such as Ca, Al, Mg, Cr, Ti, Mn, and Si, were co-extracted. Under the optimum stripping conditions, the vanadium stripping was above 92.0% in a single stage using water as the effective stripping reagent. High-quality V2O5 product was obtained after precipitation and calcination. The mechanism of vanadium (V) extraction by Aliquat 336–TBP mixed extractant was discussed based on the analysis of FT-IR and UV–vis spectra.

Thermodynamics and mechanism of vanadium(IV) extraction from sulphate medium with D2EHPA, EHEHPA and CYANEX 272 in kerosene

Extraction of vanadium(IV) from sulphate acid solution was studied using organophosphorous-based extractants D2EHPA, EHEHPA and CYANEX 272 in kerosene. The different parameters affecting the extraction of vanadium(IV) under equilibrium conditions were separately investigated to elucidate the stoichiometry of the extracted species. The distribution ratio of vanadium increased with increasing equilibrium pH of the aqueous phase, concentration of the extractants and temperature. D2EHPA was found to be a stronger extractant, having greater pH functionality than EHEHPA and CYANEX 272. Extraction of vanadium(IV) by these organophosphorous-based extractants involved cation exchange mechanism, and the extracted species appear to be VOR2(HR)2 in the low equilibrium pH and VOR2 in the higher equilibrium pH, where HR refers to the three acidic extractants.

Preparation and Photocatalytic Mechanism of Vanadium Doped NaTaO3 Nanoparticles

Pure and vanadium doped NaTaO3 nanoparticles were synthesized by hydrothermal conditions. From XRD studies, both pure as well as vanadium doped NaTaO3 are found to show pure orthorhombic phase of tatanlate. STEM studies show the formation of cube shape particles in all the samples with a particle size about 70 nm. UV-vis diffuse reflectance spectra clearly indicates the red-shift in the series of vanadium doped NaTaO3 catalysts, resulting in a decrease in the band gap of NaTaO3 caused by substitution of V5+ ions at Ta5+ site with an increase of vanadium doping concentration in NaTaO3. The results reveal that Vanadium doped NaTaO3 show good photocatalytic performance under visible light and RhodamineB (RB) degradation is improved with Vanadium doping. The photocatalytic mechanism was discussed by density functional theory. V5+ ions substitution of Ta5+ ions results in an intermediate band (IB) below the bottom of the conduction band (CB), which is mainly attributed to the state of V 3d. Meanwhile the broadening of valence band is formed due to the hybridization between the V 3d and O 2p states. Both these factors increase the transient behavior of the photogenerated charge carriers and inhibit the recombination of e–h+ pairs, showing enhanced activities over the entire visible region.

PpGalNacT2 participating in vanadium-induced HL-60 cell differentiation

The current study demonstrates vanadium plays the role of antitumor, and its antitumor effect is dosage-dependent. N-acetyl-galactosamine-transferase 2 (polypeptide: N-acetyl-α-galactosaminyl-transferases 2, ppGalNAc-T2) is a member of ppGalNAcTs (polypeptide: N-acetyl-α-galactosaminyl-transferases) family, which proves to play a vital role in the tumor emergence and development process. In this study, we focused on ppGalNAc-T2 and vanadium and aimed to determine whether ppGalNAc-T2 is correlated with vanadium's antitumor effect. We discovered that ppGalNAc-T2 changed with the variation of HL-60 cell growth induced by vanadium at mRNA level. Peanut agglutinin (PNA) is an exogenous lectin. PpGalNacT2 can be indirectly recognized by PNA. By means of flow cytometry and immunofluorescent staining, we found the deviation of PNA binding increased significantly at high concentration vanadium. Then we docked one of the possible compound substances of vanadium onto the body, VO(3) (molecular formula O(13)V(4), partial vanadate tetramer) and ppGalNAcT2, and simulated them via molecular dynamics, which showed that VO(3) may inhibit the activity of the enzyme by stemming conformational changes of a key loop of ppGalNAcT2. To sum up, our results suggested that ppGalNacT2 participated in vanadium induced HL-60 cell differentiation, which might be able to provide a new mechanism of vanadium's antitumor effect.

Kinetics and mechanism of vanadium(IV) oxidation by tetrabutylammonium tribromide

The reaction between tetrabutylammonium tribromide(TBATB) and vanadium(IV) has been studied in 50% (v/v) acetic acid under second order conditions. The overall order of reaction is found to be two, unity in each reactant. The reaction involves two single-electron transfer steps generating bromine free radical in the first rate determining step. The test for the formation of free radicals in presence of added acrylonitrile was negative while added toluene increases the rate of the reaction considerably due to its conversion into benzyl bromide. The reaction is retarded by hydrogen ions as a result of protonation prior equilibria of the active reductant, vanadyl acetate. The oxidation of the vanadylsalen complex by TBATB proceeds more rapidly than that of vanadyl acetate but follows the similar kinetic behaviour. Considerable decrease in the entropy of activation of the reaction indicates formation of an ordered transition state between the two reactants and since the kinetic behaviour remains unaltered, even after the change in the ligand attached to the reductant, indicates an interaction between the reactants through the oxygen atom on the vanadyl ion.

A Novel Fullerene Hydroxamic Acid for the Liquid–Liquid Extraction, Separation, Preconcentration, and Spectrophotometric and ICP‐AES Determination of Vanadium

A new reagent N‐phenyl‐(1,2 methanofullerene C60)61‐formohydroxamic acid (PMFFA) is reported for extraction and trace determination of vanadium(V) in nutritional and biological substrates. The extraction mechanism of vanadium from 6 M HCl media is investigated. The influence of PMFFA, diverse ions, and temperature on the distribution constant of vanadium examined. The over all stability constant (log β2 K e ) and extraction constant (K ex) are 20.89 ± 0.02 and 8.0 ± 0.02 × 10−15, respectively in chloroform. The thermodynamics parameters are calculated and kinetics of vanadium transport is discussed. The system obeys Beer's law in the range of 3.2–64.0 ng mL−1 of vanadium(V). The molar absorptivity is 7.96 × 105 L mol−1 cm−1, at 510 nm. The PMFFA–vanadium(V) complex chloroform extract in chloroform was directly inserted into plasma for ICP‐AES measurement, which increases the sensitivity by 50 folds and obey Beer's law in the range of 50–1200 pg mL−1 of vanadium(V). The method is applied for determination vanadium in real standard samples, sea water, and environmental samples.

Vanadium(IV)-mediated free radical generation and related 2′-deoxyguanosine hydroxylation and DNA damage

Free radical generation, 2′-deoxyguanosine (dG) hydroxylation and DNA damage by vanadium(IV) reactions were investigated. Vanadium(IV) caused molecular oxygen dependent dG hydroxylation to form 8-hydroxyl-2′-deoxyguanosine (8-OHdG). During a 15 min incubation of 1.0 mM dG and 1.0 mM VOSO 4 in phosphate buffer solution (pH 7.4) at room temperature under ambient air, dG was converted to 8-OHdG with a yield of about 0.31%. Catalase and formate inhibited the 8-OHdG formation while Superoxide dismutase enhanced it. Metal ion chelators, DTPA and deferoxamine, blocked the 8-OHdG formation. Incubation of vanadium(IV) with dG in argon did not generate any significant amount of 8-OHdG, indicating the role of molecular oxygen in the mechanism of vanadium(IV)-induced dG hydroxylation. Vanadium(IV) also caused molecular oxygen-dependent DNA strand breaks in a pattern similar to that observed for dG hydroxylation. ESR spin trapping measurements demonstrated that the reaction of vanadium(IV) with H 2O 2 generated OH radicals, which were inhibited by DTPA and deferoxamine. Incubation of vanadium(IV) with dG or with DNA in the presence of H 2O 2 resulted in an enhanced 8-OHdG formation and substantial DNA double strand breaks. Sodium formate inhibited 8-OHdG formation while DTPA had no significant effect. Deferoxamine enhanced the 8-OHdG generation by 2.5-fold. ESR and UV measurements provided evidence for the complex formation between vanadium(IV) and deferoxamine. UV-visible measurements indicate that dG, vanadium(IV) and deferoxamine are able to form a complex, thereby, facilitating site-specific 8-OHdG formation. Reaction of vanadium(IV) with t-butyl hydroperoxide generated hydroperoxide-derived free radicals, which caused 8-OHdG formation from dG and DNA strand breaks. DTPA and deferoxamine attenuated vanadium(IV)/r-butyl-OOH-induced DNA strand breaks.

One-electron reduction of vanadate by ascorbate and related free radical generation at physiological pH

The one-electron reduction of vanadate (vanadium(V)) by ascorbate and related free radical generation at physiological pH was investigated by ESR and ESR spin trapping. The spin trap used was 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Incubation of vanadium(V) with ascorbate generated significant amounts of vanadium(IV) in phosphate buffer (pH 7.4) but not in sodium cacodylate buffer (pH 7.4) nor in water. The vanadium(IV) yield increased with increasing ascorbate concentration, reaching a maximum at a vanadium(V) : ascorbate ratio of 2:1. Addition of formate to the incubation mixture containing vanadium(V), ascorbate, and phosphate generated carboxylate radical (·COO −), indicating the formation of reactive species in the vanadium(V) reduction mechanism. In the presence of H 2O 2, a mixture of vanadium(V), ascorbate, and phosphate buffer generated hydroxyl radical (· OH) via a Fenton-like reaction (vanadium(IV) + H 2O 2 → vanadium(V)+ ·OH+OH −). The ·OH yield was favored at relatively low ascorbate concentrations. Omission of phosphate sharply reduced the · OH yield. The vanadium(IV) generated by ascorbate reduction of vanadium(V) in the presence of phosphate was also capable of generating lipid hydroperoxide-derived free radicals from cumene hydroperoxide, a model lipid hydroperoxide. Because of the ubiquitous presence of ascorbate in cellular system at relatively high concentrations, one-electron reduction of vanadium(V) by ascorbate together with phosphate may represent an important vanadium(V) reduction pathway in vivo. The resulting reactive species generated by vanadium(IV) from H 2O 2 and lipid hydroperoxide via a Fenton-like reaction may play a significant role in the mechanism of vanadium(V)-induced cellular injury.

The mechanism of vanadium (IV) extraction in a chemical kinetic controlled regime

The rate of vanadium (IV) extraction from sulphuric acid medium by di(2-ethylhexy) phosphoric acid in n-hexane diluent was investigated. The liquid mixture was stirred at a speed at which the influence of diffusion on kinetics was believed to be a minimum. The overall rate of mass transfer was found to be first order in aqueous vanadium concentration, inverse first order in aqueous hydrogen ion concentration and a half order with respect to the concentration of the extractant in the organic phase. The rate constant at 28°C is 2.8×10 −3 mol 1 2 s −1 and the activation energy is 64 kJ mol −1. A mechanism is proposed for the extraction kinetics.

Metal catalysis in oxidation by peroxides part 8 [1] further insight on the mechanism of vanadium(V) catalyzed oxidation of sulphides and alkenes by hydrogen peroxide

The oxidation of p-chlorophenyl methyl sulphide, geraniol and cyclohexene with hydrogen peroxide in the presence of catalytic amounts of bis acetylacetonato oxovanadium(IV) [VaO(acac)2] in dioxane and dioxaneethanol has been studied, p-Chlorophenyl methyl sulphoxide and 2,3-epoxygeraniol are produced in quantitative yield; oxidation of cyclohexene is, on the other hand, much less selective, affording 2-cyclohexen-1-ol, 2-cyclohexen-1-one and cyclohexene oxide as major products. Kinetic studies indicate that the rate of sulphide oxidation, at relatively low hydrogen peroxide concentration, is first-order in sulphide, oxidant and catalyst whereas, at higher [H2O2]o, zero-order dependence on hydrogen peroxide is observed.

Metal catalysis in oxidation by peroxides. Part 5. On the mechanism of vanadium(V) catalysed oxidation by hydrogen peroxide

AbstractThe oxidation of p‐chlorophenyl methyl sulphide and of a series of phenyl substituted aryl methyl sulphides with hydrogen peroxide in the presence of catalytic amounts of bisacetylacetonato‐oxovanadium(IV) [VaO(acac)2] in ethanol, at 25°C, has been studied. The reaction affords the parent sulphoxide in quantitative yield. Oxidation rates are little affected by substitution in the phenyl ring of the sulphide. Comparison with vanadium catalysed oxidation of sulphides by tert‐butyl hydroperoxide shows that the Va(V)‐H2O2 system is much more effective than Va(V)‐ButO2H system. The initial rates of the reaction, which is first‐order in sulphide and in vanadium catalyst, show a rather complicated dependence on the initial concentration of the peroxide. Initial rates are found to increase with increasing [H2O2]0 at low peroxide initial concentration, then decrease at higher [H2O2]0; both the positive and the negative dependence show a fractionary kinetic order. Also on the ground of a kinetic investigation of the Va(V) catalysed autodecomposition of H2O2, which proceeds at measurable rate only at much higher Va(V) concentrations than those employed in the oxidation experiments, the involvement of two peroxyvanadium(V) species in the oxidation mechanism, corresponding to the equilibrium addition of one and two molecules of H2O2 to Va(V), respectively, is suggested. Whereas the mono‐adduct is believed to be a strong oxidant, the di‐adduct appears to behave, in our system, as a much weaker oxidizing agent. This is likely related to the fact that, in the conditions adopted, the di‐adduct may be largely ionized to its monoanionic form.