Purification Of Vanadium Research Articles

Efficient Recovery of Vanadium and Titanium from Domestic Titanomagnetite Concentrate Using Molten Salt Roasting and Water Leaching.

The traditional roasting technique using sodium salts in vanadium production has been disadvantageous due to the large consumption of energy and the emission of harmful gases. A modified process using molten salt roasting and water leaching to extract vanadium and titanium from domestic titanomagnetite concentrate was investigated. The roasting process was performed under optimal conditions: the weight ratio between the sample and NaOH of 1:1, the temperature of 400 °C, and the experiment time 90 min, and the conversion of vanadium could be maximized to 90%. The optimization of water leaching (at 60 °C for 90 min with a pulp density of 0.05 g/mL) could extract 98% of the vanadium from the roasted products into the solution, leaving titanium and iron remaining in the residue. Further purification of vanadium and titanium using the precipitation/hydrolysis process followed by calcination obtained the final products V2O5 and TiO2 with high purities of 90% and 96%, respectively. A potential approach with modification of the roasting stage using NaOH was proposed, which was not only efficient to selectively extract the value metals from the titanomagnetite but also eco-friendly based on the reduction in energy consumption and emission of harmful gases.

Removing trace chromium from high concentration vanadium solution by photoreduction deposition with Ti–Zr solid solution

The preparation of ultrahigh-purity vanadium (>99.99 wt%) requires the removal of trace amounts of chromium, but economical vanadium purification is difficult to achieve using crude vanadium mother liquors (>98 wt%) because of the similar properties of V(V) and Cr(IV) ions. In this study, a Ti–Zr solid solution was used for the deep purification of high-concentration ammonium polyvanadate by removing trace chromium using photocatalytic reduction process. The results show that V(V) and Cr(VI) are competitively adsorbed and photoreduced, but V(V) adsorption is preferred and occurs more rapidly than that of Cr(VI). However, after the photoreduction product of V(V), V(IV) is desorbed, whereas after that of Cr(VI), Cr(III) is deposited on the photocatalyst, achieving the separation of vanadium and chromium. The 2 h removal efficiency of chromium exceeds 80%, and the chromium content in the obtained vanadium is less than 0.04 wt%. After precipitation, the chromium content in the obtained ammonium metavanadate is less than 0.001 wt%, and the purity of the final V2O5 product exceeds 99.99%, which meets the requirement for ultrahigh-purity vanadium products. The used photocatalyst can be regenerated and reused with stable performance. This work provides a reference method for ultrahigh-purity vanadium production and an example of the industrial application of the photoreduction process.

Migration and coordination of vanadium separating from black shale involved by fluoride

With the rapid development of extraction technology of vanadium from black shale, more and more attention has been paid to its mechanism of vanadium separating. Among them, the release and oxidation process of vanadium separating from lattice and the ionic state of vanadium in the solution under the fluorine-containing system need to be revealed urgently to guide and improve the separation and purification of vanadium from black shale. In this study, the migration and coordination of vanadium leaching is preliminarily explored through experiments and simulation studies. Leaching kinetics analysis show that the release of vanadium from black shale is mainly controlled by chemical reaction under the direct acid leaching process. DFT simulations further confirm that the remove of structural oxygen atoms is the control step of vanadium release. Meanwhile, the destruction of VO octahedron depends on the synergy of H+ and F− in turn, which pull vanadium away from mica interfaces in the form of six-coordinated [VF6]. The oxidation process of vanadium is mainly caused by the breaking of VO bonds and the formation of VF bonds. After transferring into a fluorine-containing solution, the ionic state of vanadium transforms constantly with the change of the concentration of H+ and F−, wherein the main reversible coordination process of V(IV) is: VF62−⇄ VF5−⇄ VF4⇄ VF3+⇄ VF3(OH) ⇄ VOF2⇄ VOF+⇄ VO2+, and the main reversible coordination process of V(V) is: VF6−⇄ VF5⇄ VF4+⇄ VF4(OH) ⇄ VOF3⇄ VOF2+⇄ VOF2(OH) ⇄ VO2F ⇄ VO2+. Above, the basic theory of vanadium separation from shale at atomic level has been studied systematically.

Vanadium purification: A review

Vanadium purification: A review

Recovery of tungsten from spent selective catalytic reduction catalysts by pressure leaching

The recovery and purification of vanadium (V) and tungsten (W) from honeycomb-type spent selective catalytic reduction (SCR) catalyst was investigated using an autoclave through a pressure leaching process. Spent SCR catalyst mainly consists of TiO2 and other oxides (7.73% WO3, 1.23% V2O5, etc.). The reaction temperature, NaOH concentration, time, additive concentration, and liquid–solid (L/S) ratio were varied during the leaching process. The optimal reaction conditions were identified for recovery of V and W. The addition of NaOH to Na2CO3 improved the amount of V and W recovered because of the enhancing effect of NaOH in Na2CO3. As the concentration of CaCl2 was increased during the precipitation process in order to separate the recovered V and W, the precipitation percentages of V and W increased, respectively. However, the use of Ca(OH)2 as the additive reduced the precipitation percentage of W. Therefore, despite full precipitation of V (98.6%), only 7.73% of W was precipitated when 3 equivalents of Ca(OH)2 was reacted with spent SCR catalyst for 30min. The remaining W in the leaching solution was reacted with NH4OH to form ammonium tungstate, which was converted to ammonium paratungstate through evaporation. Consequently, V and W could be recovered and separated successfully through the process in this study.

Radiochemical processing of activated specimens of vanadium–chromium–titanium alloy

The extraction part of the technological scheme for radiochemical separation of components of irradiated vanadium–chromium–titanium (V–Cr–Ti) alloy and for their purification from metallic activation products was tested on the whole using activated alloy specimens. It was shown that the replacement of the acid re-extraction of vanadium with a peroxide re-extraction and of the acid re-extraction of chromium with an alkaline re-extraction substantially improves the characteristics of the extraction reprocessing of the activated V–Cr–Ti alloy. In particular, the durations of the vanadium and chromium re-extractions were shortened by about an order of magnitude, the outputs of these alloy components increased, vanadium purification from rare-earth metals became twice as great, and chromium decontamination from cobalt increased by two orders of magnitude.

エレクトロスラグ溶解法を用いたバナジウムの低コスト高純度化プロセスの開発と水素吸蔵合金への適用

エレクトロスラグ溶解法を用いたバナジウムの低コスト高純度化プロセスの開発と水素吸蔵合金への適用

Separation of Rare Metals by Solvent Extraction Employing Reductive Stripping Technique

The Separation and purification of vanadium from V/Mo mixture and europium from Sm/Eu/Gd mixture by solvent extraction followed by chemical, electrochemical or photochemical reductive stripping, has been investigated. Vanadium (penta) was first extracted into organic phase along with molybdenum from their solution mixture, and the vanadium reduced either chemically by L-ascorbic acid, electrochemically using platinum electrode or photochemically using low pressure mercury or halogen lamp. The resulting vanadium(tetra) was then separated by selective stripping. In the case of mixed rare earths solution, Eu3+ was reduced to Eu2+ electrochemically using titanium plate electrode or photochemically using low or high pressure mercury lamp. The divalent europium thus obtained was then precipitated selectively to effect separation from samarium and gadolinium.

Separation and purification of vanadium and molybdenum by solvent extraction followed by reductive stripping.

The solvent extraction of vanadium and molybdenum by tri-n-octylmethylammonium chloride (TOMAC) from neutral solutions was studied and it was found that vanadium was extracted preferentially by an anion exchange mechanism. The pentavalent vanadyl anion in the organic solution was found to be reduced to the form of tetra- or trivalent cations by contact with an aqueous solution containing a reduction agent such as L-ascorbic acid. This enables the vanadium to be stripped selectively by chemical reduction, with the molybdenum remaining in the organic phase

Purification of Vanadium by External Gettering

Vanadium metal has been purified with respect to carbon, oxygen and nitrogen by allowing these impurities to diffuse to and react with a surface layer rich in titanium. The nitrogen concentration was reduced from 100 ppm to less than 1 ppm, the carbon concentration was reduced from 240 ppm to less than 2 ppm and the oxygen concentration was reduced from 290 ppm to 6 ppm. The resistance ratio was increased from 52 to more than 685, a value that would indicate a total interstitial impurity concentration of 11 ppm. The diamond pyramid hardness was between 44 and 50 after purification. The internal friction peaks due to these interstitial solutes had almost completely disappeared in the purified metal. The purification can be done at any temperature at which the interstitial solutes are able to diffuse rapidly enough. Both 1000 and 1200 °C were found to be satisfactory with somewhat higher purity obtained at 1000 °C. This method is quite versatile and can be applied to specimens more than one cm thick if sufficient time is allowed for diffusion.

1218. Purification of vanadium by vacuum melting: W E Anable, J Vac Sci Technol, 7 (6), Nov/Dec 1970, S74– S81

1218. Purification of vanadium by vacuum melting: W E Anable, J Vac Sci Technol, 7 (6), Nov/Dec 1970, S74– S81

1222. Electron-beam float zone and vacuum purification of vanadium: R E Reed, J Vac Sci Technol, 7 (6), Nov/Dec 1970, S105– S112

1222. Electron-beam float zone and vacuum purification of vanadium: R E Reed, J Vac Sci Technol, 7 (6), Nov/Dec 1970, S105– S112

Purification of Vanadium by Vacuum Melting

The Bureau of Mines compared the purification of two commercially available vanadium samples by three vacuum melting techniques: consumable-electrode arc melting in a conventional deep mold, consumable-electrode arc melting at the top of the mold, and conventional electron-beam melting. Top-of-the-mold (TOM) and electron-beam (EBF) melts were both conducted in the same vessel equipped with a bottom-withdrawal mechanism. Pressures during melting were in the range of 0.10–0.50 mTorr; the pressure in the deep mold could not be measured, but probably exceeded 100–300 mTorr during a typical melt. Arc melting was characterized by melting rates of 500–800 g/min, but electron-beam melts were limited to rates of 20–30 g/min. Forty-nine percent of the oxygen content was removed by double melting vanadium sponge at the top of the mold, and 42% of the oxygen content was removed from electrorefined vanadium treated in the same manner; however, the carbon and nitrogen increased. The purity of samples melted at the TOM approached the purity of samples prepared in the EBF. In some instances, a further decrease in the oxygen and metallic impurity content resulted from remelting selected materials in the electron-beam furnace. Little or no purification resulted from melting vanadium in the conventional deep mold. Purification proceeded faster and more completely on melting vanadium with small additions of yttrium, carbon, or aluminum; aluminum was largely removed on double melting, but carbon and yttrium were retained in the products. Metal or carbon additions tended to stabilize the arc and improve metal recovery from 85 to greater than 90% during a consumable-electrode arc melt. Typical metal hardness ranged from Rhn B-20 to B-30. Mass-spectrometric studies conducted in conjunction with the purification work demonstrated that CO, CO2, Al2O, and AlO were the principal oxides, while Al, Fe, Ti, Mn, Ni, V, Cr, Ca, and Cu were the principal metallics evolved when heating and melting vanadium. The volatilization of VO was slow and incomplete; therefore, sacrificial dissociation was of minor importance in the purification of vanadium.

Electron-Beam Float Zone and Vacuum Purification of Vanadium

Electron-beam float zone melting vanadium three passes at 3.9 in./h in 4×10−10 Torr vacuum resulted in resistance ratios of about 700 and a total impurity content of 50 wt ppm. The zoning reduced both carbon and oxygen content. However, while carbon removal was always accompanied by a lowering of the oxygen content, the reverse was not true. The removal of oxygen was probably accomplished by the formation and volatilization of VO. The mechanism for carbon removal was not clearly resolved. Nitrogen was not appreciably affected by electron-beam float zone melting. All metallic impurities, with the exception of Ta and W and possibly Si, were effectively volatilized. No evidence was found for zone refining action on any impurity. Vacuum outgassing further reduced the carbon and oxygen level. However, the oxygen removal was far more effective than the carbon. The nitrogen content increased, particularly on the specimens that lost about 40% in weight due to vanadium evaporation. However, the effect of vacuum outgassing was less on the highest purity as-zoned specimens. The same purification mechanisms apparently operated.