Method for recovering vanadium, and method for selectively recovering vanadium from solution containing vanadium and other metals

Abstract

To provide a method for recovering vanadium from a solution containing vanadium through a simplified process.SOLUTION: A method for recovering vanadium comprises: an addition step of adding to a solution in which ions containing vanadium (V) (hereinafter referred to as vanadate ions) are dissolved, an electron donor which is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound; an ultraviolet irradiation step of irradiating the solution derived from the addition step with ultraviolet light to induce precipitation of a reduced form of the vanadate ions contained in the solution; and a separation step of separating the reduced form of the vanadate ions precipitated in the ultraviolet irradiation step from the solution.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recovering vanadium and a method for selectively recovering vanadium from a solution containing vanadium and other metals. [Background technology]

[0002] Vanadium is a rare metal that is essential for realizing a hydrogen society, and is used in steel plates, catalysts, redox flow batteries, and hydrogen storage materials. However, 99% of its ore is produced in three countries: China and Russia. For this reason, the establishment of recycling technology is desired, but the recycling rate is low at 17%. This is due to the fact that a great deal of effort is required to separate the components from used products, there are processes with low recovery rates, and the generation of wastewater and exhaust gases that place a high burden on the environment, making treatment expensive. For example, in conventional methods, vanadium components are roasted and then leached into water (they are pentavalent, but their chemical species change depending on the pH to VO4 3- to VO2 + There are various forms, from the NH4VO3 stage to the NH4VO3 stage.) Ammonia water is added to the NH4VO3 and the precipitate is recovered, but the precipitate does not completely settle and a large amount of nitrogen-containing wastewater is generated.

[0003] As another method for recovering vanadium, for example, Patent Document 1 proposes (a) placing wet fly ash under a potential gradient, (b) pressurizing it in the range of 0.1 MPa to 1.0 MPa, or (c) pressurizing it under a potential gradient in the range of 0.1 MPa to 1.0 MPa to obtain a recovery liquid, and concentrating vanadium from this recovery liquid by membrane separation. Also, Patent Document 2 proposes a vanadium recovery apparatus and vanadium recovery system that efficiently recovers vanadium from incineration ash generated by the combustion of petroleum-based fuels. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2017 / 104360 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-190522 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and aims to provide a method for recovering vanadium from a solution containing vanadium by a simple procedure. Furthermore, vanadium is sometimes used in the field of catalysts, for example, by forming an alloy with a metal such as molybdenum, and there is also a technical need for selectively recovering vanadium from such used alloys. Therefore, in another aspect, the present invention aims to provide a method for selectively recovering vanadium from a solution containing vanadium and other metals. [Means for solving the problem]

[0006] As a result of extensive research aimed at solving the above problems, the present inventors have found that when a solution containing vanadium(V)-containing ions (hereinafter referred to as vanadate ions) is dissolved in a solution to which an electron donor, such as an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound are added, and the resulting solution is irradiated with ultraviolet light, the vanadate ions in the solution are photochemically reduced to water-insoluble chemical species such as VO, a vanadium(II) compound, which can then be completely precipitated and recovered. The present invention was completed based on the above findings, and provides the following:

[0007] (1) The present invention provides a method for recovering vanadium, comprising: an addition step of adding an electron donor, which is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound to a solution containing dissolved vanadium (V)-containing ions (hereinafter referred to as vanadate ions); an ultraviolet irradiation step of irradiating the solution that has been subjected to the addition step with ultraviolet light to precipitate reduced forms of the vanadate ions contained in the solution; and a separation step of separating the reduced forms of the vanadate ions precipitated by the ultraviolet irradiation step from the solution.

[0008] (2) The present invention also provides a method for recovering vanadium according to the above (1), wherein the electron donor is an aliphatic secondary alcohol.

[0009] (3) The present invention also provides a method for recovering vanadium according to the above (1) or (2), in which the electron donor is 2-propanol.

[0010] (4) The present invention also provides a method for recovering vanadium according to any one of (1) to (3), wherein the ketone compound is acetone.

[0011] (5) The present invention also provides a method for selectively recovering vanadium from a solution containing vanadium and other metals, which comprises adding an electron donor, which is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound to a solution containing vanadium (V)-containing ions (hereinafter referred to as vanadate ions) and coexisting metals (excluding alkali metals and alkaline earth metals), and then irradiating the solution with ultraviolet light to precipitate reduced forms of the vanadate ions contained in the solution.

[0012] (6) The present invention also relates to the method according to (5), wherein the pH of the solution is 5.0 or higher.

[0013] (7) The present invention also relates to the method according to (5) or (6), wherein the pH of the solution is 13.0 or less.

[0014] (8) The present invention also provides the method according to any one of (5) to (7), wherein the coexisting metal is molybdenum. [Effects of the Invention]

[0015] According to the present invention, there is provided a method for recovering vanadium from a solution containing vanadium by a simple procedure. In addition, according to another aspect of the present invention, there is provided a method for selectively recovering vanadium from a solution containing vanadium and other metals. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a plot showing the change in vanadium concentration in solution with respect to irradiation time in Example 1. [Figure 2] FIG. 2 is a plot showing the change in the amount of vanadium in the precipitate versus irradiation time in Example 1. [Figure 3] FIG. 3 is a plot of vanadium and molybdenum concentrations in solution versus irradiation time for Example 2. [Figure 4] FIG. 4 is a plot showing the amount of vanadium and molybdenum species in the precipitate versus irradiation time in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, one embodiment of the method for recovering vanadium according to the present invention and one embodiment of the method for selectively recovering vanadium from a solution containing vanadium and other metals will be described. Note that the present invention is not limited to the following embodiment, and can be practiced with appropriate modifications within the scope of the present invention.

[0018] <Vanadium recovery method> The method for recovering vanadium of the present invention is characterized by comprising the steps of: adding an electron donor, which is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound to a solution containing vanadium (V)-containing ions (also referred to as vanadate ions, as described above); irradiating the solution that has undergone the addition step with ultraviolet light to precipitate reduced forms of the vanadate ions contained in the solution; and isolating the reduced forms of the vanadate ions precipitated by the ultraviolet irradiation step from the solution. Each step will be described below.

[0019] [Addition process] The adding step is a step of adding an electron donor, which is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound to a solution containing vanadium(V) ions. An aqueous solution is a preferred example of this solution. This solution contains vanadium ions derived from vanadium ores or recycled vanadium-containing products.

[0020] Vanadium (V)-containing ions refer to chemical species in which other elements are bonded to vanadium (oxidation state 5) to form ions. Examples of such species include the vanadium oxoanion VO4 3- , V2O7 4- , V3O9 3- , V4O 12 4- , V5O 14 3- , V 10 O 28 6- , V 12 O 32 4- , V 13 O 34 3- , V 18 O 42 12- ,VO 3- , [VO3] n- Vanadic acids such as VO2 +In the present invention, these chemical species are collectively referred to as vanadate ions. Note that VO2, an oxonium ion of vanadium (V), + is a cation, and it is chemically incorrect to call it a vanadate ion, but in the present invention, such oxonium ions are also referred to as vanadate ions.

[0021] The concentration of vanadate ions in the solution is not particularly limited as long as it can be dissolved in a solvent to form a solution, and an example of such a concentration of vanadate ions is about 0.1 mmol / L to 100 mmol / L.

[0022] The electron donor is added to the vanadate ions excited by UV light in the UV irradiation step described below, donating electrons to reduce them. Aliphatic secondary alcohols or aliphatic secondary thioalcohols are used as such electron donors. Aliphatic secondary alcohols and aliphatic secondary thioalcohols contain hydroxyl or thiol groups with unshared electron pairs, and the excited vanadate ions are thought to be reduced by the electrons contained in these unshared electron pairs. Specifically, when the vanadium (V) contained in the vanadate ions is excited under UV irradiation, the electron donor with the unshared electron pair donates electrons to the vanadium (V), reducing the pentavalent vanadium to tetravalent, and then further electrons are donated to trivalent and then divalent. The divalent vanadium precipitates as solvent-insoluble VO. As a result of this reduction, the aliphatic secondary alcohol or aliphatic secondary thioalcohol itself is thought to be oxidized to a ketone or thioketone. For example, when 2-propanol is used as the aliphatic secondary alcohol, the electron donor, vanadium(V) is reduced to produce acetone.

[0023] Examples of aliphatic secondary alcohols include 2-propanol, 2-butanol, and 2-pentanol. Examples of aliphatic secondary thioalcohols include 2-propanethiol, 2-butanethiol, and 2-pentanethiol. Among these, aliphatic secondary alcohols are preferred as the electron donor, and among aliphatic secondary alcohols, 2-propanol is particularly preferred.

[0024] The concentration of the electron donor in the solution is preferably in large excess relative to the concentration of vanadate ions. An example of the concentration of such an electron donor in the solution is about 10 mmol / L to 10 mol / L. The molar concentration ratio of the electron donor to the molar concentration of vanadate ions is, for example, about 5 to 10,000 times.

[0025] Preferred examples of the ketone compound include aliphatic ketone compounds. Among these, acetone or methyl ethyl ketone is preferred as the ketone compound, with acetone being particularly preferred. The concentration of the ketone compound in the solution is preferably in large excess relative to the concentration of vanadate ions. An example of the concentration of such a ketone compound in the solution is about 10 mmol / L to 1 mol / L. The ratio of the molar concentration of the ketone compound to the molar concentration of vanadate ions can be about 5 to 100 times.

[0026] It is also preferable to add a strong electrolyte salt to the solution to maintain a constant ionic strength. Adding such a salt promotes the precipitation of vanadium. A preferred example of such a salt is sodium perchlorate. The amount of such a salt to be added can be about 10 mmol / L to 500 mmol / L.

[0027] In this step, the solution containing vanadate ions to which the electron donor and the ketone compound have been added is subjected to an ultraviolet ray irradiation step.

[0028] [Ultraviolet irradiation process] The ultraviolet irradiation step is a step in which the solution that has been subjected to the above-mentioned addition step is irradiated with ultraviolet light to precipitate the reduced form of vanadate ions contained in the solution. At this time, pentavalent vanadium is reduced and precipitated. Examples of such precipitated chemical species include VO, a compound of vanadium (II).

[0029] As mentioned above, the ultraviolet light used in this process excites the vanadium contained in the vanadate ions, causing a reduction reaction. Therefore, the ultraviolet light used must have a wavelength that can be absorbed by the vanadate ions. Since vanadate ions have a wide range of absorption at wavelengths of 400 nm or less, the ultraviolet light used is not particularly limited as long as it includes wavelengths of 400 nm or less. While light of 380 nm or more is generally considered visible light, in the present invention, light of 400 nm or less is considered ultraviolet. Furthermore, the ultraviolet light used may include ultraviolet light with wavelengths of 400 nm or less, and therefore may include visible light in addition to ultraviolet light with wavelengths of 400 nm or less. Examples of light sources used to generate such ultraviolet light include, but are not limited to, mercury-xenon lamps, high-pressure mercury lamps, and metal halide lamps.

[0030] Some of the above light sources generate heat during light emission, generating heat rays (infrared rays). When such light sources are used, the temperature of the solution to be irradiated may rise excessively. Therefore, an optical filter that blocks heat rays may be provided between the light source and the solution to be irradiated. An example of such an optical filter is a water filter in which water is sealed inside the filter.

[0031] In the ultraviolet irradiation step, the solution is irradiated with ultraviolet light as described above, and it is preferable to irradiate the solution with ultraviolet light while stirring it. Although not particularly limited, the temperature of the solution at this time can be, for example, about 20°C. Furthermore, in order to prevent undesirable side reactions caused by oxygen present in the system, it is preferable to carry out the ultraviolet irradiation step under an argon or nitrogen atmosphere.

[0032] The required UV irradiation time varies depending on the vanadium concentration in the solution and the intensity of the UV light emitted from the light source. Therefore, it is preferable to determine the UV irradiation time by measuring the change in vanadium concentration in the solution using, for example, inductively coupled plasma (ICP) atomic emission spectrometry. For example, when an aqueous solution (10 mL) containing 10.4 mmol / L NH4VO3, 0.50 mmol / L 2-propanol, 0.1 mmol / L acetone, and 0.1 mmol / L sodium perchlorate monohydrate was irradiated with UV light from a mercury-xenon lamp (200 W output) while stirring in an argon atmosphere, ICP atomic emission spectrometry confirmed that the vanadium in the solution almost disappeared in approximately 5 hours.

[0033] The solution in which vanadium precipitates have been formed by the ultraviolet irradiation step is subjected to a fractionation step.

[0034] [Preparative process] The separation step is a step of separating the reduced form of vanadate ions precipitated by the ultraviolet irradiation step from the solution, thereby recovering vanadium from the solution.

[0035] The precipitated reduced form of vanadate ions is considered to be a divalent vanadium compound, VO, as described above. Since this is a solid, it can be separated by a conventional solid-liquid separation method, such as filtration or centrifugation.

[0036] The vanadium separated from the solution is then subjected to the necessary treatment and recycled. As described above, according to the present invention, it is possible to recover vanadium from a solution by a simple method in which an electron donor and a ketone compound are added to a solution containing vanadate ions, and the solution is then irradiated with ultraviolet light.

[0037] <Method for selectively recovering vanadium from a solution containing vanadium and other metals> Next, an embodiment of the method for selectively recovering vanadium from a solution containing vanadium and other metals according to the present invention will be described. Note that the "other metals" referred to here do not include alkali metals and alkaline earth metals.

[0038] The method of the present invention for selectively recovering vanadium from a solution containing vanadium and other metals is characterized in that an electron donor, which is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound are added to a solution containing vanadium (V)-containing ions and coexisting metals (excluding alkali metals and alkaline earth metals), and then the solution is irradiated with ultraviolet light to precipitate reduced forms of vanadate ions contained in the solution. The vanadium (V)-containing ions have already been described, and these ions will be referred to as vanadate ions here as well.

[0039] This method is the same as the above-described "Vanadium Recovery Method" except that the solution to be treated contains vanadium and other metals, and other points can be the same as those in the above-described "Vanadium Recovery Method." Therefore, explanations that overlap with the above-described "Vanadium Recovery Method" will be omitted, and differences will be mainly described.

[0040] The method of this embodiment was completed based on the following discovery by the present inventors. Specifically, when a solution containing vanadate ions and coexisting metals is irradiated with ultraviolet light in the presence of an electron donor that is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol and a ketone compound, a precipitate forms in the solution, as in the above-described "method for recovering vanadium." However, the precipitate contains almost no coexisting metals and is composed exclusively of reduced vanadate ions. When the vanadium concentration and the coexisting metal concentration in the remaining solution are examined, the vanadium concentration is found to be close to zero, while the coexisting metals remain almost unchanged. The method of this embodiment utilizes this discovery and is used to recover vanadium as a precipitate from a solution containing vanadate ions and coexisting metals.

[0041] Coexisting metals contained in a solution together with vanadate ions generally exist in the form of some kind of ion in the solution. Therefore, strictly speaking, it would be more correct to call them "ions containing coexisting metals" rather than "coexisting metals." However, in this specification, these are collectively referred to as "coexisting metals."

[0042] The coexisting metal is a metal other than alkali metals and alkaline earth metals, and examples of such metals include molybdenum, tantalum, aluminum, nickel, and copper. Among these metals, molybdenum is a particularly preferred example. The concentration of the coexisting metal in the solution is not particularly limited as long as it can be dissolved in the solvent to form a solution. An example of the concentration of such a coexisting metal is about 1 mmol / L to 100 mmol / L, but is not particularly limited.

[0043] When selectively recovering vanadium from a solution containing vanadium and other metals by light irradiation, it is preferable to set the pH of the solution to 5.0 or higher. A pH greater than 5.0 allows for sufficient precipitation of vanadium. In particular, when the coexisting metal is molybdenum, molybdenum tends to precipitate at a low pH of 2.0 or less, and hardly precipitates at a pH of 5.0 or higher. Therefore, setting the pH of the solution to 5.0 or higher increases the efficiency of selective separation of vanadium from the solution. The upper limit of the pH of the solution is preferably about 13.0, and more preferably about 9.0. A pH of 9.0 or lower is preferable because most of the vanadium contained in the solution can be recovered as a precipitate, but vanadium can also be recovered even if the pH of the solution is higher than this.

[0044] A solution is prepared by the same operation as the addition step in the above "Method for recovering vanadium" except that the solution contains a coexisting metal. The prepared solution is subjected to an operation corresponding to the ultraviolet irradiation step in the above "Method for recovering vanadium", and a precipitate, which is a reduced form of vanadate ions, is formed in the solution.

[0045] The precipitate thus produced can be recovered by an operation corresponding to the separation step in the "vanadium recovery method" described above, thereby separating the reduced form of vanadate ions. According to the method of this embodiment, vanadium can be selectively recovered from a solution containing vanadium and other metals, and therefore, for example, vanadium can be recovered from an alloy containing vanadium. [Example]

[0046] The method for recovering vanadium according to the present invention will be explained in more detail below by showing examples, but the present invention is not limited to the following examples in any way.

[0047] [Example 1] The mixture consisted of NH4VO3 (10.9 mmol / L), 2-propanol (0.50 mol / L), acetone (0.10 mol / L), and sodium perchlorate monohydrate (NaClO 4· An aqueous solution containing HO (0.10 mol / L) was placed in a photoreaction cell (liquid volume 10 mL) and irradiated with ultraviolet-visible light (220-460 nm) using a mercury-xenon lamp while stirring in an argon atmosphere. This test was performed multiple times, varying the irradiation time from 1 to 12 hours. After the specified irradiation time, the concentration of vanadium remaining in the solution was analyzed by ICP emission spectroscopy, and the precipitate was recovered by centrifugation. Figure 1 shows a plot of the change in vanadium concentration in the solution versus irradiation time, as obtained by this quantification. Figure 2 also shows a plot of the change in the amount of vanadium in the precipitate versus irradiation time.

[0048] As shown in Figure 1, the vanadium concentration in the water decreases with light irradiation, and after 5 hours it has almost completely disappeared. Furthermore, as shown in Figure 2, the amount of vanadium recovered increases with the passage of light irradiation time. The amount of vanadium in the precipitate produced after 12 hours of irradiation reached 97.4 μmol, indicating that 89% of the vanadium present in the water before the reaction was separated and recovered as precipitate.

[0049] [Example 2] The mixture consisted of NH4VO3 (10.0-11.0 mmol / L), 2-propanol (0.50 mol / L), acetone (0.10 mol / L), K2MoO4 (9.4-10.4 mmol / L), and sodium perchlorate monohydrate (NaClO 4· An aqueous solution containing HO (0.10 mol / L) was placed in a photoreaction cell (10 mL volume). While stirring in an argon atmosphere, the solution was irradiated with ultraviolet-visible light (220–460 nm) using a mercury-xenon lamp. This test was repeated multiple times, varying the irradiation time from 1 to 6 hours. The aqueous solution used in each test contained vanadium at concentrations of 10.0–11.0 mmol / L and molybdenum at concentrations of 9.4–10.4 mmol / L. After the specified irradiation times, the vanadium and molybdenum concentrations in the solution were measured using ICP emission spectroscopy and UV-visible absorption spectroscopy, respectively, and the amounts of vanadium and molybdenum in the resulting precipitate were also measured. Figure 3 shows plots of the vanadium and molybdenum concentrations in the solution versus irradiation time. Figure 4 also shows plots of the amounts of vanadium and molybdenum in the precipitate versus irradiation time.

[0050] As shown in Figures 3 and 4, precipitation occurred after 3 hours or more of irradiation, and the precipitate formed after 6 hours of irradiation contained 98.1% of the vanadium present in the solution before irradiation in the test from which this sample was obtained. On the other hand, this precipitate contained only 0.3% of the molybdenum contained in the solution before irradiation. This demonstrates that the present invention enables the recovery of vanadium with high yield and high selectivity.

[0051] [Example 3] In Example 3, the pH dependence of the recovery amount of each metal in a mixed solution of vanadium and molybdenum was investigated. First, a mixture of NH4VO3 (9.42 to 10.80 mmol / L), 2-propanol (0.50 mol / L), acetone (0.10 mol / L), K2MoO4 (9.80 to 10.80 mmol / L), and sodium perchlorate monohydrate (NaClO 4· An aqueous solution containing HO (0.10 mol / L) was prepared, and hydrochloric acid or sodium hydroxide was added to this solution to adjust the pH to between 1.8 and 12.7. Each of the prepared solutions was irradiated for 6 hours with ultraviolet-visible light (220-460 nm) from a mercury-xenon lamp while stirring in an argon atmosphere in a photoreaction cell (10 mL volume). After this irradiation, the concentrations of vanadium and molybdenum in the solution were measured using ICP emission spectroscopy and ultraviolet-visible absorption spectroscopy, respectively, and the amounts of vanadium and molybdenum in the precipitates formed. Table 1 shows the pH of each solution before the reaction, the vanadium and molybdenum concentrations before and after the reaction, and the amounts of vanadium and molybdenum in the precipitates formed.

[0052] [Table 1]

[0053] As shown in Table 1, for each sample in which the pH of the pre-reaction solution was between 5.0 and 9.0, the vanadium concentration in the post-reaction solution was significantly reduced, indicating that the vanadium in the solution was almost completely recovered, while the molybdenum concentration in the post-reaction solution remained almost unchanged from that before the reaction. Furthermore, even when the pH of the pre-reaction solution was 9.0 or higher, the vanadium recovery rate was slightly lower than when the pH was between 5.0 and 9.0, but the molybdenum concentration in the post-reaction solution remained almost unchanged from that before the reaction. These results demonstrate that the present invention allows selective recovery of vanadium from a solution even when it contains coexisting metals.

Claims

1. Ions containing vanadium (V) (hereinafter referred to as vanadate ions) an addition step of adding an electron donor which is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound to a solution in which the above-mentioned amine compound is dissolved; an ultraviolet irradiation step of irradiating the solution that has been subjected to the adding step with ultraviolet light to precipitate reduced forms of vanadate ions contained in the solution; and a separation step of separating the reduced form of vanadate ions precipitated by the ultraviolet irradiation step from the solution.

2. 2. The method for recovering vanadium according to claim 1, wherein said electron donor is an aliphatic secondary alcohol.

3. 2. The method for recovering vanadium according to claim 1, wherein the electron donor is 2-propanol.

4. 2. The method for recovering vanadium according to claim 1, wherein the ketone compound is acetone.

5. A method for selectively recovering vanadium from a solution containing vanadium and other metals, comprising adding an electron donor which is an aliphatic secondary alcohol or an aliphatic secondary thioalcohol, and a ketone compound to a solution containing vanadium (V)-containing ions (hereinafter referred to as vanadate ions) and coexisting metals (excluding alkali metals and alkaline earth metals), and then irradiating the solution with ultraviolet light to precipitate reduced forms of the vanadate ions contained in the solution.

6. 6. The method of claim 5, wherein the pH of the solution is 5.0 or higher.

7. 7. The method of claim 6, wherein the pH of the solution is 13.0 or less.

8. The method according to any one of claims 5 to 7, wherein the coexisting metal is molybdenum.

Images