• Resources Recycling
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• v.29 no.5
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• pp.28-37
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• 2020

In this study, the effect of precipitation temperature, ammonium chloride amount and addition method, vanadium and sodium hydroxide content of the solution on the precipitation of ammonium metavanadate were examined by using the sodium vanadate(NaVO₃) solution in alkali region as a starting material. As the pH of solution decreased, the addition amount of ammonium chloride and the vanadium content of the solution increased, the precipitation rate of ammonium metavanadate increased. In this research condition, the basic conditions for obtaining more than 90% of precipitation yield were 10,000mg/L of vanadium content, 2equivalents of ammonium chloride addition, room temperature, and 2 hours of precipitation time. The size of precipitated particles decreased with increasing precipitation rate. Especially when liquid ammonium chloride was injected into the solution, the precipitation rate was the slowest and the particle size of the precipitate was the largest. After the primary precipitation by adding ammonium chloride as a solid, the secondary precipitation was carried out by adding new reactants. At this time, the precipitation with added ammonium chloride solid was not affected by the precipitates present in the solution. However, when liquid ammonium chloride was added, new precipitate was deposited on the surface of the precipitate present in the solution, increasing its size. Due to the difference in ammonium metavanadate solubility to temperature, the precipitation temperature at the vanadium content of 10,000mg/L in the solution affected the precipitation rate of ammonium metavanadate and the precipitation temperature did not affect the precipitation rate at a high concentration of more than 30,000mg/L vanadium content in the solution.

• Resources Recycling
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• v.32 no.3
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• pp.26-37
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• 2023

Good control of the solution pH and temperature is required to recover vanadium from the water leaching solution of vanadium ore after sodium roasting. However, such adjustments could lead to aluminum-vanadium and sodium-vanadium co-precipitation, which greatly affects the efficiency of vanadium recovery. In this study, a process that can increase the efficiency of vanadium recovery as ammonium metavanadate [NH₄VO₃] and ammonium polyvanadate [(NH₄)₂V₆O₁₆·H₂O] was investigated by examining the characteristics of vanadium-containing aqueous solutions during precipitation. The aluminum content of vanadium-containing water leaching solutions has a great effect on the loss of vanadium when the pH of the aqueous solution is adjusted to 9. Therefore, a process to minimize aluminum leaching is also required. In this study, ~99% or more of vanadium present in vanadium-containing aqueous solutions was precipitated and recovered as NH₄VO₃ by adding 3 equivalents of ammonium chloride relative to the vanadium content at pH 9 and room temperature. (NH₄)₂V₆O₁₆·H₂O was precipitated from the aluminum-vanadium coprecipitates generated during the pH-adjustment of the aqueous solutions to 9 by dissolving the coprecipitate in the solutions at pH 2.5 and controlling their sodium content to 2,000 mg/L or less. Approximately, 98% or more of the available (NH₄)₂V₆O₁₆·H₂O could be precipitated and recovered from a solution with a vanadium content of 2,200 mg/L and a sodium content of 1,875 mg/L at pH 2.5 by adding approximately 3 equivalents of ammonium chloride relative to the vanadium content at 95℃ or higher. The overall process could precipitate and recover, approximately 91% or more of the total vanadium in the water leaching solution as NH₄VO₃ and (NH₄)₂V₆O₁₆·H₂O.

• Resources Recycling
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• v.28 no.5
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• pp.42-50
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• 2019

In this study, the precipitation reaction of vanadium and ammonium chloride in aqueous solution was investigated in order to recover vanadium. Ammonium metavanadate having a crystal structure of [$NH_4VO_3$] was precipitated from aqueous solution containing vanadium at pH 9.2 ~ 9.4, and ammonium polyvanadate having a crystal structure of [$(NH_4)_2V_6O_{16}$] was precipitated when the pH of the aqueous solution containing vanadium was adjusted with sulfuric acid. Ammonium polyvanadate [$(NH_4)_2V_6O_{16}$] precipitated at a temperature of $80{\sim}90^{\circ}C$ and pH 2, and at a temperature of $40^{\circ}C$ and pH 6 ~ 8 of aqueous solution. In the acidic region of aqueous solution pH 2, the vanadium content of the aqueous solution should be at least 3,000 mg/L and the precipitation temperature should be maintained at $80^{\circ}C$ or higher in order to obtain a precipitation ratio of 99% or more. When the ammonium vanadate was precipitated in the alkaline region, the vanadium content was more than 10,000 mg/L and the precipitation temperature was maintained at $40^{\circ}C$ to increase the precipitation ratio. Aluminum was not precipitated regardless of the vanadium content and pH of the aqueous solution. However, the iron component reacts with ammonium chloride to precipitate into ammonium jarosite. Therefore, Fe component must be preferentially removed in order to increase the recovery of vanadium.

• Resources Recycling
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• v.30 no.6
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• pp.3-11
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• 2021

In this study, the effect of the solubility of ammonium metavanadate and the decomposition ratio of ammonium ions on a precipitation reaction-the precipitation of ammonium metavanadate by adding ammonium chloride to a sodium vanadate solution-was investigated. As the precipitation temperature and pH increased, the decomposition ratio of ammonium ions increased, and the decomposition ratio was greater than 81% at 45 ℃ and pH 9.3. This was approximately four times higher than that at pH 8. The result of the precipitation reaction, in view of these two factors that significantly influence the precipitation reaction, was that the precipitation yield increased as the temperature increased. However, the effect of temperature was not significant above 35 ℃. A kinetic study of the precipitation reaction revealed that the activation energy of the reaction was 42.3 kJ/mol. Therefore, considering the solubility of ammonium metavanadate, the lower the temperature, the better the vanadium recovery yield. Additionally, considering the decomposition of ammonium ions, the lower the pH of the aqueous solution, the more advantageous. However, at pH 8 or less, sodium polyvanadate is precipitated and the purity of vanadium oxide may reduce.

• Resources Recycling
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• v.31 no.2
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• pp.40-48
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• 2022

In this study, the effects of solution components were investigated in the recovery of vanadium as ammonium metavanadate from vanadium-ore-salt roasting-water leaching solution. The vanadium-containing solution is strongly alkaline (pH 13), so the pH must be lowered to 9 or less to increase the ammonium metavanadate precipitation efficiency. However, in the process of adjusting the solution pH using sulfuric acid, aluminum ions are co-precipitated, which must be removed first. In this study, aluminum was precipitated in the form of an aluminum-silicate compound using sodium silicate, and the conditions for minimizing vanadium loss in this process were investigated. After aluminum removal, the silicate was precipitated and removed by adjusting the solution pH to 9 or less using sulfuric acid. In this process, the concentration and addition rate of sulfuric acid have a significant influence on the loss of vanadium, and vanadium loss was minimized as much as possible by slowly adding dilute sulfuric acid. Ammonium metavanadate was precipitated using three equivalents of ammonium chloride at room temperature from the aluminum-free, aqueous solution of vanadium following the pH adjustment process. The recovery yield of vanadium in the form of ammonium metavanadate exceeded 81%. After washing the product, vanadium pentoxide with 98.6% purity was obtained following heat treatment at 550 ℃ for 2 hours.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.445-451
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• 2019

The fluorescence intensity and fluorescence lifetime of $Ba_2GdV_3O_{11}$, a vanadate compound based on $Ba^{2+}$ ion, were investigated by adding $Eu^{3+}$ as a rare earth ion which is an alkaline earth metal, which is distributed around active ions and has a large influence on fluorescent properties when used as a host in a phosphor. $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor was synthesized by solid state method and the crystallinity of the phosphor was confirmed by X - ray diffraction analysis. The fluorescence properties of the $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor were measured using optical and laser. The energy transfer and diffusion of the $Ba_2GdV_3O_{11}:Eu^{3+}$ phosphor are highly dependent on the concentration of $Eu^{3+}$. When the concentration of $Eu^{3+}$ is low, it shows strong fluorescence to the CT band. However, as the concentration of $Eu^{3+}$ increases, the fluorescence due to 4f - 4f transition is strong. The concentration of $Eu^{3+}$ ion increased and the energy between ions was diffused, and the lifetime of fluorescence decreased. Energy transfer occurs between two $Eu^{3+}$ ions at low $Eu^{3+}$ concentration and energy diffusion occurs at high $Eu^{3+}$ concentration.

• Clean Technology
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• v.27 no.2
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• pp.146-151
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• 2021

Pure and Sm ion doped BiVO₄ catalysts were synthesized using a conventional hydrothermal method and characterized by XRD, DRS, SEM, and PL. We also examined the activity of these materials on the photocatalytic decomposition of rhodamine B under visible light irradiation. The doping of Sm ion into BiVO₄ catalyst changed the ms-BiVO₄ crystal structure into the tz-BiVO₄ crystal structure in the low synthesis temperature. Light absorption analysis using DRS showed that all the catalysts displayed strong absorption in the visible range of the electromagnetic spectrum regardless of Sm ion doping. In addition, an amorphous morphology was shown in the pure BiVO₄ catalyst, but the morphology of the BiVO₄ catalyst doped with Sm ion was changed into an ellipse shape and also the particle size decreased. In the photocatalytic decomposition of rhodamine B, Sm ion doped BiVO₄ catalyst showed higher photocatalytic activity than the pure BiVO₄ catalyst. In addition, the Sm3-BVO catalyst doped with 3% Sm ion showed the highest photocatalytic activity, as well as the highest formation rate of OH radicals (•OH) and the highest PL peak. This result suggests that the formation rate of OH radicals produced in the interface between the photocatalyst and water is well correlated with the photocatalytic activity.

• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.148-154
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• 2019

Vanadium oxide based materials have been studied as novel negative electrode materials in lithium-ion batteries (LIBs) because of their high specific capacity. In this study, potassium metavanadate ($KVO_3$) was synthesized and its electrochemical properties are evaluated as a negative electrode materials. The aqueous solution of $NH_4VO_3$ is mixed with a stoichiometric amount of KOH. The solution is boiled to remove $NH_3$ gas and dried to obtain a precipitate. The obtained $KVO_3$ powders are heat-treated at 300 and $500^{\circ}C$ for 8 h in air. As the heat treatment temperature increases, the initial reversible capacity decreases, but the cycle performance and Coulombic efficiency are improved slightly. On the contrary, the electrochemical performances of the $KVO_3$ electrodes are greatly improved when a polyacrylic acid (PAA) as binder was used instead of polyvinylidene fluoride (PVDF) and a fluoroethylene carbonate (FEC) was used as electrolyte additive. The initial reversible capacity of the $KVO_3$ is 1169 mAh/g and the Coulombic efficiency is improved to 76.3% with moderate cycle performance. The $KVO_3$ has the potential as a novel high-capacity negative electrode materials.

• Resources Recycling
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• v.31 no.2
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• pp.56-62
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• 2022

This study investigated the water leaching behavior of vanadium in Na₂CO₃-roasted vanadium-bearing titaniferous magnetite (VTM) concentrate. The magnetic concentrate and Na₂CO₃, mixed in a mass ratio of 4:1, were roasted at 1050 ℃, kept for 3 h, and ground to a size of D₅₀ = 48.79 ㎛ using a rod mill. The effects of leaching temperature and pulp density on water leaching were then investigated. The results show that the vanadium leaching efficiency decreased to 90.4%, 88.2%, and 83.8% as the temperature increased to 25, 55, and 85 ℃, respectively, whereas it remained almost constant 90.4%, 87.0%, and 87.0% as the pulp density increased to 10, 50, and 100 w/v%, respectively. Based on the preliminary leaching results, multi-stage leaching was conducted with the experimental conditions of 25 ℃, 100 w/v%, 300 rpm, and 1 h. The vanadium concentration in the final leaching solution was determined as 16.20 g/L after four stages of leaching. Thus, a high-concentration sodium vanadate solution was prepared by multi-stage leaching.

• Resources Recycling
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• v.30 no.4
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• pp.54-63
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• 2021

Vanadium and tungsten can be obtained by separating/recovering the leaching solution from a spent SCR DeNO_X catalyst using the soda roasting-water leaching process. Therefore, in this study, the adsorption/desorption mechanism of vanadium and tungsten in an ion-exchange column was investigated using Lewatit MonoPlus MP 600, a strong basic anion exchange resin. The operating conditions for the separation of vanadium and tungsten in the ion-exchange column was intended to present. By conducting a continuous adsorption experiment in a pH 8.5 solution, the adsorption capacity of vanadium and tungsten was found to be 44.75 and 64.92 mg/(g of resin), respectively, which showed that the adsorption capacity of tungsten was larger than that of vanadium because of the difference in ion charge. Vanadium has a higher affinity for MP 600 than tungsten. Consequently, as the vanadium-containing solution is eluted through the ion exchange resin onto which tungsten is adsorbed, the adsorbed tungsten is exchanged with vanadium and desorbed. A continuous experiment was performed with a solution of vanadium and tungsten prepared at the same concentration as the spent SCR DeNO_X catalyst leachate. The adsorption capacity of vanadium was found to be 48.72 mg/(g of resin) and 80% of the supplied vanadium was adsorbed; in contrast, almost no tungsten was adsorbed. Therefore, vanadium and tungsten were separated effectively. The ion exchange resin was treated with 2 M HCl at 15 mL/h, and 97.7% of the vanadium(99% purity) could be desorbed. After desorption, NH₄Cl was added to precipitate ammonium polyvanadate at 90℃ and recover 93% of the vanadium.