Reduction Of Vanadium Research Articles

Polyanion Sodium Vanadium Phosphate for Next Generation of Sodium‐Ion Batteries—A Review

AbstractPolyanion‐type sodium (Na) vanadium phosphate in the form of Na3V2(PO4)3 has demonstrated reasonably high capacity, good rate capability, and excellent cyclability. Two of three Na ions per formula can be deintercalated at a potential 3.4 V versus Na+/Na with oxidation of V3+/4+. In the reversible process, two Na ions intercalate back resulting in a discharge capacity of 117.6 mAh g−1. Further intercalation is possible but at a low potential of 1.4 V versus Na+/Na accompanied by vanadium reduction V3+/2+, leading to a capacity of 60 mAh g−1. Due to its marvelous electrochemical performance, it has attracted a lot of attention since its discovery in the 1990s. To develop truly useable polyanion‐type vanadium phosphate, better understanding of its crystal configuration, sodium ions' transportation, and electronic structure is essential. Therefore, this review only focuses on the inside of crystal configuration and electronic structure of polyanion‐type vanadium phosphate, Na3V2(PO4)3, since there are a few good reviews on various processing technologies.

Behavior of vanadium during reduction and smelting of vanadium titanomagnetite metallized pellets

Abstract The effects of CaO content, MgO content and smelting temperature on the vanadium behavior during the smelting of vanadium titanomagnetite metallized pellets were investigated. The thermodynamics of reduction and distribution of vanadium was analyzed and the high-temperature smelting experiments were carried out. The thermodynamic calculations show that the distribution ratio of vanadium between the slag and the hot metal decreases with the increments of CaO and MgO content in the slag as well as the increase of the smelting temperature. The smelting experiments demonstrate that the vanadium content in iron and the recovery rate of vanadium in pig iron increase as the CaO content, MgO content and smelting temperature increase, whereas the vanadium distribution ratio between the slag and iron tends to decrease. Moreover, the recovery rate of vanadium in pig iron has a rising trend with increasing the optical basicity of the slag. The addition of MgO in the slag to increase the slag optical basicity can not only improve the vanadium reduction but also promote the formation of magnesium-containing anosovite, which is beneficial to following titanium extraction.

CRISPRi System as an Efficient, Simple Platform for Rapid Identification of Genes Involved in Pollutant Transformation by Aeromonas hydrophila.

Aeromonas species are indigenous in diverse aquatic environments and play important roles in environmental remediation. However, the pollutant transformation mechanisms of these bacteria remain elusive, and their potential in pollution control is largely unexploited so far. In this work, we report an efficient and simple genome regulation tool to edit Aeromonas hydrophila and identify its biomolecular pathways for pollutant transformation. The genome regulation system, which is based on the type II clustered regularly interspaced short palindromic repeat interference (CRISPRi) system from Streptococcus pyogenes, can serve as a reversible and multiplexible platform for gene knockdown in A. hydrophila. A single-plasmid CRISPRi system harboring both dCas9 and the sgRNA was constructed in A. hydrophila and used to silence diverse genes with varied sizes and expression levels. With this system, up to 467-fold repression of gfp expression was achieved, and the function of the essential gene-ftsZ was identified quickly and accurately. Furthermore, simultaneous transcriptional repression of multiple targeted genes was realized. We discovered that the ars operon played an essential role in arsenic detoxification, and the extracellular electron transfer (EET) pathway was involved in methyl orange reduction, but not in vanadium reduction by A. hydrophila. Our method allows better insights and effective genetic manipulation of the pollutant transformation processes in Aeromonas, which might facilitate more efficient utilization of the Aeromonas species and other microbial species for environmental remediation applications.

Experimental Study on Strengthening Carbothermic Reduction of Vanadium-Titanium-Magnetite by Adding CaF2

The effects and reduction mechanisms of carbothermic reduction of vanadium–titanium–magnetite were studied by adding various mass fractions of CaF2 ranging from 0%, 1%, 3%, 5% to 7%. The results showed that the proper CaF2 addition could strengthen the carbothermic reduction of vanadium–titanium–magnetite while the excessive amounts will weaken the promotive effect, hence the appropriate dosage was determined to be 3 mass%. The CaF2 was favorable for the carbon gasification reaction, where it increased the partial pressure of CO inside briquette and caused the lattice distortion of vanadium–titanium–magnetite. The reaction improved the reduction process and accelerated the reduction rate. The appearance of 3CaO·2SiO2·CaF2 and other complex compounds with low melting point facilitated the aggregation and growth of the slag and the iron, which increased the concentration of iron grains and the aggregation level of the slag.

Biological sulfur in the blood cells of Ascidia ceratodes: XAS spectroscopy and a cellular-enzymatic hypothesis for vanadium reduction in the ascidians

Two samples of living blood cells and of cleared blood plasma from the Phlebobranch tunicate Ascidia ceratodes from Bodega Bay, California, and one of fresh Henze solution from A. ceratodes of Monterey Bay, California, have been examined using sulfur K-edge x-ray absorption spectroscopy (XAS). Biological sulfur included sulfate esters, sulfate and bisulfate ions, benzothiazole, thianthrene, epi-sulfide, thiol and disulfide. Glutathione dominated reduced sulfur, from which an average intracellular Voltage of −0.21 V was calculated. Sulfate-bisulfate ratios yielded blood cell pH values of 2.0 and 2.8. Total blood cell [sulfur] was 373±9 mM or 296±73 mM from BaSO4 gravimetry. Two plasma samples (pH 6.9 or 7.0; [S] = 33±6 mM or 26±4 mM) were dominated by sulfate and disulfide. Fresh Henze solution evidenced a sulfur inventory similar to blood cells, with calculated pH = 2.7. A V(III)-sulfonate fraction varied systematically with intracellular pH across six independent blood cell samples, implying a vanadium mobilization pathway. Bodega Bay and Monterey Bay A. ceratodes appear to maintain alternative suites of low-valent sulfur. The significance of the vanabins to vanadium metabolism is critically examined in terms of known protein – V(IV) biochemistry. Finally, a detailed hypothesis for the reduction of [VO4]3− to V(III) in ascidians is introduced. A vanadium oxido-reductase is proposed to span the signet ring membrane and to release V(III) into the inner acidic vacuole. The V(V) to V(III) reduction is predicted require an inner-sphere mechanism, a thiol reductant, 7-coordinate V(III), a biologically accessible Voltage, and proton-facilitated release of V(III).

Kinetic regularities of alloying iron-carbon alloys with vanadium

The results of the vanadium reduction laboratory investigation are presented. Experiments were conducted with CaO-SiO2-Al2O3-V2O3slags in a wide range of compositions in an air atmosphere. A saturated iron- carbon melt was used as a reducing agent. The reduction kinetics was studied by sampling. V2O3reduction from slags having a viscosity of more than 0.5 Pa⋅s and containing less than 7.5–8.0% V2O3proceeds in a diffusion mode. The reaction is of the first order in vanadium. The process rate is inversely proportional to the square root of slag viscosity. A good agreement between the obtained data and the results of electrochemical studies on the cathodic reduction of vanadium was found. One made possible to deduce the rate equation of vanadium reduction by an iron-carbon melt depending on the volume concentration, temperature and slag viscosity. The calculated data for different slags acceptably check with those found by experiment.

A novel Z-scheme Ag6Si2O7/AgI nanocomposite photocatalyst: Study on the degradation of various refractory compounds and reduction of vanadium (V)

The Z-scheme photocatalyst system, with independent reduction and oxidation reaction processes and efficient separation of carriers, has been widely concerned in the field of wastewater treatment. Herein, a Z-scheme Ag6Si2O7/AgI heterojunction nanocomposite was successfully constructed through co-precipitation method and subsequently investigated as a novel photocatalyst for the first time. The macroscopic physical structure, microscopic chemical element composition and optical properties of samples as-prepared samples were adequately detected by various characterization techniques. The photocatalytic properties of Ag6Si2O7/AgI heterostructure with different composite ratios were investigated by degrading methyl orange (MO) under visible light irradiation (λ > 420 nm), and the degradation efficiency of optimal sample (1/3 Ag6Si2O7/AgI) can achieve 99.7% within 8 min, which was about 15.3 and 124.6 folds higher than that of individual Ag6Si2O7 (6.5%) and AgI (0.8%), respectively. Meanwhile, Ag6Si2O7/AgI showed an excellent capability of phenol degradation and V reduction, which might be ascribed to the strong visible light absorption, rapid separation efficiency of photo-induced charge carriers and direct Z-scheme charge transfer mechanism verified by the results of UV–vis diffuse reflection spectra, transient photocurrent response spectra and XPS measurements, respectively. Moreover, Ag6Si2O7/AgI nanocomposite presented a good stability and reusability after four runs. Finally, a possible Z-scheme mechanism is proposed to illustrate the enhanced photocatalytic performance of the Ag6Si2O7/AgI nanocomposite.

Effect of iron transformation on Acidithiobacillus ferrooxidans bio-leaching of clay vanadium residue

The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated. Acidithiobacillus ferrooxidans affects the dissolution of vanadium through the catalytic effect on Fe3+/Fe2+ couple and material exchange. The passivation of iron settling correlates with ferrous ion content in bio-leaching solution. In medium containing A. ferrooxidans and Fe(III), the increment in Fe(II) concentration leads to the formation of jarosite, generating a decline in vanadium extraction efficiency. Analysis of cyclic voltammetry shows that Fe(II) ion is apt to be oxidized and translated into precipitate by A. ferrooxidans, which strongly adsorbed to the surface of the residue. Fe(III) ion promotes the vanadium extraction due to its oxidizing activity. Admixing A. ferrooxidans to Fe(III) medium elevates the reduction of low valence state vanadium and facilitates the exchange of substance between minerals and solution. This motivates 3.8% and 21.8% increments in recovery ratio and leaching rate of vanadium compared to the Fe(III) exclusive use, respectively. Moreover, Fe(II) ion impacts vanadium extraction slightly in sterile medium but negatively influences vanadium leaching in the presence of bacteria.

Use of Vanadium for Low-alloy Steel Manufacturing at JSC “EVRAZ NTMK”

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Identifying the presence of [V=O]2+ during SCR using in-situ Raman and UV Vis spectroscopy

Abstract Combining UV Vis and Raman spectrosocopy allows for V O, oxo vanadium(IV) surface species to be identified during operando SCR on V2O5/TiO2 catalysts. V4+ is formed by a one electron reduction pathway by NO and NH3 and it exhibits a V O stretch which is red shifted slightly compared to its V5+ counterpart. This is due to an extra proton charge balancing the reduced entity in form of an OH group. This red shift is similar in nature to the effect of hydration, which is a function of water partial pressure in the gas stream and the temperature. It is shown that the red shift cannot solely be due to changes in the water contents, and that it is related to a reduction of vanadium. Furthermore, exposing the oxidized catalyst to 1.5% H2O, which is more than an order of magnitude higher than the residual water level present after the NO and NH3 reduction, induces less red shift as observed after reduction of the catalyst in the apparent dry conditions. It is further observed with UV Vis spectroscopy that NO and NH3 reduction forms a V(IV) band at 15,000 cm−1.

Electrochemical Reduction of Vanadium(V)‐Cupferron Complex, VO(cupf)2OH

AbstractElectrochemical reduction of vanadium(V) complex with cupferron (N‐nitroso‐N‐phenylhydroxylamine), VVO(cupf)2OH, has been studied by polarography in wide potential range to verify the catalytic mechanism of electroreduction of coordinated cupferron ligand. Reduction of the complex was studied in the concentration range from 2 ⋅ 10−5 M to 10−3 M. Depending on the process conditions kinetics of catalytic reduction of coordinated cupferron is either controlled by adsorption step or governed by mixed control of diffusion and chemical reaction. Kinetic parameters of the reduction process are reported.Reduction of VVO(cupf)2OH complex is accompanied by adsorption and autoinhibition phenomena. V(II) ion in the surface bound complex of vanadium with cupferron catalyzes reduction of coordinated cupferronate ligands. In 1 mM solutions, the catalytic reduction of coordinated cupferron ligand shifts to more cathodic potentials due to formation of a monolayer of adsorbed vanadium(III)‐cupferron complexes. Reduction kinetics in the presence of tetraalkylammonium salt is consistent with multilayer cooperative adsorption of anionic vanadium(II)‐cupferron complex and tetraalkylammonium cations.

An automatic reserve flow injection method using vanadium (III) reduction for simultaneous determination of nitrite and nitrate in estuarine and coastal waters

An automatic reserve flow injection method using vanadium (III) as a reducing agent for the simultaneous determination of nitrite and nitrate in estuarine and coastal waters was reported for the first time. Vanadium (III) chloride was used as an environmentally friendly substitute to toxic cadmium for reducing nitrate to nitrite. The experimental parameters were optimized based on a univariate experimental design. The salinity effect of estuarine and coastal waters was carefully investigated. Under the optimized conditions, the detection limit of the proposed method was 0.06 µmol L−1 and 0.13 µmol L−1, and the linearity was up to 20 µmol L−1 and 80 µmol L−1 for nitrite and nitrate detection, respectively. The relative standard deviations were below 1.5% (n = 7). The recovery of spiked estuarine and coastal water samples varied from 100.0 ± 2.5% to 107.5 ± 2.5% for nitrite and 90.7 ± 0.3% to 98.0 ± 1.0% for nitrate. The sample throughput was approximately 15 h−1. The analytical results obtained with the proposed method displayed good agreement with the classic copperized cadmium column reduction method. The automatic reserve flow injection method has been successfully applied to analyze the nitrite and nitrate in estuarine and coastal water samples.

Amidoximation of cross-linked polyacrylonitrile fiber and its highly selective gallium recovery from Bayer liquor

Fibrous adsorbent functionalized with amidoxime group has been recognized as the most potentially adsorbing material for recovering gallium from Bayer liquors, but the practical process has not been so attractive owing to the performance decreasing in strongly alkaline conditions. The purpose of this research aims to enhance the Ga/V selectivity and efficiency of extraction and retain the mechanical stability of the adsorbent by cross-linking the polyacrylonitrile fiber before amidoximation. In this study, cross-linking amidoxime-functionalized PAN fiber (C-PAO) was prepared by cross-linking polyacrylonitrile fiber through triethylene tetramine. Subsequently, the cross-linked PAN fiber was reacted with hydroxylamine at 70 °C and the C-PAO fiber was obtained. C-PAN and C-PAO were characterized with Fourier transmission infrared spectrometer, scanning electron microscope and single-fiber electronic tensile strength tester, respectively. The performance of C-PAO for gallium adsorption was measured by batch and multilevel adsorption experiments. Experimental data showed that the maximum static adsorption capacity of Ga in simulating Bayer liquor was 26.9 mg/g, and the equilibrium adsorption time was 60 min which indicated that the shorter exposure time equated to the less degradation of the amidoxime groups and the reduction of mechanical performance. The extraction efficiency of gallium was more than 85% using hydrochloric acid (1 mol/L) as stripping agent. The maximum static adsorption capacity in Bayer liquor was 17.6 mg/g, and the saturated adsorption time was 140 min, which are both better than that of commodity gallium-recycled resin. In addition, after four-stage adsorption by C-PAO, gallium was entirely adsorbed while a reduction of vanadium is no more than 20%, which showed a good selective adsorption of gallium. In conclusion, the C-PAO fiber is a highly effective adsorbent for enrichment and separation of gallium in the presence of competitive ions such as V5+ and Al3+ in strongly alkaline Bayer liquid.

Reduction of vanadium(V) in a microbial fuel cell: V(IV) Migration and Electron Transfer Mechanism

Reduction of vanadium(V) in a microbial fuel cell: V(IV) Migration and Electron Transfer Mechanism

The isothermal reduction kinetics of chromium-bearing vanadium–titanium magnetite sinter

ABSTRACTThe reduction of chromium-bearing vanadium–titanium magnetite sinter (CVTMS) by CO was investigated at 1123–1223 K. The reduction degree increased with increasing temperature. The isothermal reduction kinetics of CVTMS was analysed, according to Sharp analysis and ln–ln analysis, the kinetic mechanism of reduction process for all samples in different basicity can be represented as f(α) = 1.61(1−α)[−ln(1−α)]1–1/1.61. The reaction activation energy of all samples (R = 1.9, 2.1, 2.3, obtained according to the components of the materials burdening used in sintering process) at different reaction degrees were calculated by the model-free method. And the pre-exponential factors of reaction also were calculated by the mathematical method. The rate controlling step for the reduction process under the present reduction condition was chemical reaction.

Nitrous acid-driven reduction of vanadium as a neptunium analogue

Nitrous acid-driven reduction of vanadium as a neptunium analogue

Thermodynamic study of direct reduction of high-chromium vanadium–titanium magnetite (HCVTM) based on phase equilibrium calculation model

High-chromium vanadium–titanium magnetite (HCVTM) is a good valuable resource with high iron content in the form of complex iron ore which contains various valuable metal elements such as iron, vanadium, titanium, chromium. Direct reduction of HCVTM is studied based on thermodynamic analysis. Combined TG experimental verification and equilibrium calculation model was used to analyze the reaction sequence and equilibrium amount in this paper. The contents in HCVTM reduction system are simplified as 18 kinds of chemical compositions. Reductions of Fe3O4 and FeO·TiO2 are the main reduction reactions and are mainly reduced by C. The reduction reaction sequence of FeO·TiO2 is FeO·TiO2, TiO2, TiC, and Ti; the reduction reaction sequence of Fe3O4 is Fe3O4, FeO, and Fe. The minimum reduction temperature of HCVTM is 860 °C. The reduction of Cr is difficult to implement, and the minimum reduction temperature of V is above 700 °C. The gas phase in this system is mainly CO when the temperature is above 1000 °C. CO partial pressure curve of gasification reaction is in the shape of ‘S’ with increase of temperature. When the temperature is 1350 °C, C/O is 1.0 and reduction time is 30 min, HCVTM can be reduced thoroughly and the reduction degree can reach to 0.98. When C/O is lower than 1.0, FeTi2O5 is the reduction intermediate products from FeO·TiO2. When C/O is 1.0, diffraction peaks of Fe3O4 and FeO·TiO2 disappear, and they are reduced to Fe and TiO2.

Avaliação teórica do uso do oxihidróxido de vanádio trivalente na detecção eletroquímica de nandrolona

Pela primeira vez foi descrito um caso interessante de uso do oxihidróxido de vanádio trivalente (VO(OH)) como modificador de elétrodo na detecção eletroquímica de nandrolona. Foi mostrado que o oxihidróxido de vanádio pode ser um modificador eficiente para a detecção de nandrolona, mas, ao contrário da maioria dos casos de uso de oxihidróxido de cobalto, composto parecido, o processo é catódico e dá-se em meio moderadamente ácido a neutro. O comportamento oscilatório, no sistema, é possível apenas por causa das influências do processo da eletrorredução de vanádio tetravalente em trivalente na dupla camada elétrica.

Structural Evolution during Lithium- and Magnesium-Ion Intercalation in Vanadium Oxide Nanotube Electrodes for Battery Applications

Multiwalled vanadium oxide nanotubes are an intriguing class of materials due to their complex and functional structure. They have especially gained attention as an electrode material for rechargeable ion batteries exhibiting Li-ion storage capacities up to 250 mAh/g. The pristine nanotube materials and their electrochemical properties have previously been investigated extensively; however little knowledge exists on the structural transformations induced by ion storage in vanadium oxide nanotube electrodes. In this work, the changes in the atomic-scale and nanoscale structure during lithium- and magnesium-ion storage in two types of vanadium oxide nanotubes are investigated by operando powder X-ray diffraction and total X-ray scattering. Linear expansion and contraction of the VOx layers with vanadium reduction and oxidation are observed, while the interlayer spacing is found to be drastically dependent on the nature of the templating molecules or ions residing in the interlayer space of the pristine tube...

Ternary pentagonal-bipyramidal oxovanadium(V) complexes containing five- and six-membered chelate rings: Syntheses, structures and properties

Reactions of bis(acetylacetonato)oxovanadium(IV) [VO(acac)2] with isolated or in-situ generated α-diketone bis(para-R-benzoylhydrazones) (H2Ln (n = 1–6), where 2H represent the two dissociable amide protons) in methanol or chloroform–methanol (1:3) mixture afford six novel oxovanadium(V) complexes of formula [VO(acac)(Ln)] (1–6) in 51–64% yields. All the complexes have been characterized by elemental analysis, mass spectrometric, solution electrical conductivity, various spectroscopic (IR, UV–Vis, and 1H NMR) and cyclic voltammetric measurements. The complexes are brown in color. They are diamagnetic and non-electrolytes. Molecular structures of all six complexes have been determined by single crystal X-ray crystallography. The metal center in each complex is in a distorted pentagonal-bipyramidal N2O5 coordination sphere. The fused 5,5,5-membered chelate rings forming ON2O-donor (Ln)2− and one of the acetylacetonate-O form a N2O3 pentagonal plane around the vanadium atom, while the second acetylacetonate-O and the oxo atom occupy the two axial positions. In the crystal lattice, the complexes form one-dimensional chain-, ladder- and ribbon-like supramolecular structures via various types of intermolecular non-covalent interactions such as trifurcated OH∙∙∙(O,O,O), bifurcated CH∙∙∙O∙∙∙HC and CH∙∙∙(O,O), simple CH∙∙∙O, π−π, CH∙∙∙π and O∙∙∙O interactions. The spectroscopic features of 1–6 are consistent with their molecular structures. All the complexes are redox active and display a quasi-reversible to irreversible vanadium(V) to vanadium(IV) reduction in the potential range −0.80 to −0.92 V (vs. Ag/AgCl).