A method of adjusting the valence state of vanadium ions in a solution

Abstract

The application discloses a method for adjusting the valence state of vanadium ions in a solution, which comprises the following steps: (1) adding a hydroxylamine compound into a vanadium-containing solution and reacting; (2) adding an acid into the solution obtained in the step (1) and reacting to obtain a tetravalent vanadium ion solution. The method of the application uses a hydroxylamine compound as an adjusting agent, adjusts the pH value of the solution by adding an acid, and unifies the solution containing vanadium ions with any valence state into a tetravalent vanadium solution. The method can be applied to a solution containing vanadium ions with any valence state, especially a vanadium-containing solution with unknown valence state composition or a solution possibly containing vanadium ions with different valence states. The method does not need to detect and quantitatively analyze the valence state and valence state composition of vanadium ions in the solution in advance, and unifies the vanadium ions with any valence state in the solution into tetravalent vanadium ions. The existing form of vanadium ions in the final solution is only tetravalent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vanadium element, and in particular, the present application relates to a method for adjusting the valence state of vanadium ions in a solution. BACKGROUND

[0002] Vanadium, as a transition metal element, has multiple valence states, and the common valence states are +2, +3, +4 and +5. Among them, +5 valence vanadium is the most stable, has oxidizing property, low valence vanadium has reducing property, and the reducing property increases with the decrease of the valence state. The diversity of valence states of vanadium reflects the diversity of its compound types, and thus it has a wide range of applications in metallurgy, chemical industry and battery industry.

[0003] Vanadium compounds are usually adjusted in valence state during preparation or recycling. The existing methods for adjusting the valence state of vanadium ions in a solution mainly include electrolysis, adding oxidizing agent or adding reducing agent. CN106532079B discloses a method for recycling vanadium flow battery electrolyte, which takes the spent electrolyte after capacity attenuation as raw material, first electrolyzes it, and then adjusts the valence state of vanadium ions by adding oxidizing agent or reducing agent to realize the recycling of the spent electrolyte. CN107117654B discloses a method for preparing vanadium dioxide from vanadium solution, which takes palladium chloride, palladium and the like as catalyst, reduces the pentavalent vanadium solution to tetravalent vanadium in a reaction kettle under hydrogen atmosphere, and then prepares vanadium dioxide. CN102983346B discloses a method for preparing vanadyl sulfate by using failed vanadium electrolyte, which takes the failed vanadium electrolyte as raw material, first increases all vanadium ions to +5 valence by charging, then precipitates vanadium, and adds organic reducing agent to reduce the pentavalent vanadium, thereby preparing vanadyl sulfate crystals.

[0004] However, the current methods for adjusting the valence state of vanadium ions still have some problems. On the one hand, the above methods are relatively complicated, and need to be electrolyzed or heated, etc., which has high energy consumption. On the other hand, the application range is relatively single, and only a single valence state of vanadium ions is reduced or oxidized to tetravalent vanadium ions, and the valence state of vanadium ions in the solution needs to be detected in advance to determine the subsequent adjustment steps. Different valence states need different adjustment steps, and need to be adjusted respectively. SUMMARY

[0005] The present application is based on the discovery and understanding of the inventors on the following facts and problems: the current methods for adjusting the valence state of vanadium ions still have some problems. On the one hand, they are relatively complicated, and need to be electrolyzed or heated, etc., which has high energy consumption. On the other hand, the application range is relatively single, and only a single valence state of vanadium ions is reduced or oxidized to tetravalent vanadium ions, and the valence state of vanadium ions in the solution needs to be detected in advance to determine the subsequent adjustment steps. Different valence states need different adjustment steps, and need to be adjusted respectively.

[0006] The present application aims to solve at least one of the problems in the related art. To this end, embodiments of the present application provide a method for adjusting the valence of vanadium ions in a solution, which uses a hydroxylamine compound as an adjusting agent and adjusts the pH of the solution by adding an acid, so that a solution containing vanadium ions of any valence is adjusted to a solution of tetravalent vanadium ions. The method can be applied to a solution containing vanadium ions of any valence, especially a solution containing vanadium ions of unknown valence or a solution possibly containing vanadium ions of multiple different valences. The method does not require prior detection and quantitative analysis of the valence and valence composition of vanadium ions in the solution, and adjusts vanadium ions of any valence in the solution to tetravalence. The final solution contains only tetravalent vanadium ions.

[0007] The method for adjusting the valence of vanadium ions in a solution according to an embodiment of the present application comprises the following steps:

[0008] (1) adding a hydroxylamine compound to a vanadium-containing solution and reacting;

[0009] (2) adding an acid to the solution obtained in step (1) and reacting to obtain a solution of tetravalent vanadium ions.

[0010] The method for adjusting the valence of vanadium ions in a solution according to an embodiment of the present application has the following advantages and technical effects: a hydroxylamine compound is used as an adjusting agent, and the pH of the solution is adjusted by adding an acid, so that a solution containing vanadium ions of any valence is adjusted to a solution of tetravalent vanadium ions. The electrode potential of the hydroxylamine compound under acidic conditions can be between ψ(V 3+ ) and ψ(V 5+ ), so that when coexisting with trivalent vanadium ions, the hydroxylamine compound can act as a weak oxidizing agent to oxidize trivalent vanadium ions to tetravalent vanadium ions, and when coexisting with pentavalent vanadium ions, the hydroxylamine compound can act as a reducing agent to reduce pentavalent vanadium ions to tetravalent vanadium ions. Adjusting the pH of the solution by adding an acid helps to make the electrode potential of the hydroxylamine compound between ψ(V 3+ ) and ψ(V 5+ ), which plays an auxiliary role in the valence adjustment process. The method of the present application can be carried out at room temperature, is simple to operate, and can effectively reduce the cost of valence adjustment of vanadium ions. The method of the present application can be applied to a solution containing vanadium ions of unknown valence or a solution possibly containing vanadium ions of multiple different valences, and the method of the present application does not require prior detection and quantitative analysis of the valence and valence composition of vanadium ions in the solution, and adjusts vanadium ions of any valence in the solution to tetravalence. The final solution contains only tetravalent vanadium ions. The method of the present application is simple to operate, efficient and low in cost, and is conducive to promoting the rapid and efficient adjustment of the valence of vanadium ions in the solution and improving the preparation or recycling efficiency of vanadium compounds.

[0011] In some embodiments, in step (1), the vanadium-containing solution is a vanadium-containing solution of unknown valence.

[0012] In some embodiments, in the step (1), the vanadium-containing solution comprises at least one of divalent vanadium ions, trivalent vanadium ions, tetravalent vanadium ions, pentavalent vanadium ions.

[0013] In some embodiments, in the step (1), the vanadium-containing solution comprises at least one of vanadium trichloride, vanadyl sulfate, vanadyl oxalate, sodium metavanadate, ammonium metavanadate, vanadium battery electrolyte, vanadium-containing waste solution; the vanadium-containing waste solution comprises at least one of vanadium battery waste electrolyte, vanadium-containing leaching solution.

[0014] In some embodiments, in the step (1), the hydroxylamine compound comprises at least one of hydroxylamine, hydroxylamine hydrochloride, hydroxylamine sulfate, hydroxylamine phosphate.

[0015] In some embodiments, in the step (1), the hydroxylamine compound is in the form of a hydroxylamine compound solution, and the concentration of the hydroxylamine compound solution is 0.5-2 mol / L.

[0016] In some embodiments, in the step (1), the molar ratio of the hydroxylamine compound to vanadium ions in the vanadium-containing solution is 0.5-3:1.

[0017] In some embodiments, in the step (1), the reaction time is 0.5-2 h.

[0018] In some embodiments, in the step (2), an acid is added to the solution obtained in the step (1) until the pH value is 0.1-1.2.

[0019] In some embodiments, in the step (2), after the acid is added to the solution obtained in the step (1), the electrode potential of the hydroxylamine compound is between ψ(V 3+ ) and ψ(V 5+ ).

[0020] In some embodiments, the hydroxylamine compound is an oxidizing agent or a reducing agent.

[0021] In some embodiments, in the step (2), the acid comprises at least one of hydrochloric acid and sulfuric acid.

[0022] In some embodiments, in the step (2), the concentration of the acid is 2-6 mol / L.

[0023] In some embodiments, in the step (2), the reaction time is 1-2 h. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 are the UV-Vis absorption spectra before and after adjusting the valence state of vanadium ions in the solution in Example 1.

[0025] Figure 2 is the UV-visible absorption spectrum before and after adjusting the valence state of vanadium ions in the solution in Example 2.

[0026] Figure 3 is the UV-visible absorption spectrum before and after adjusting the valence state of vanadium ions in the solution in Example 3.

[0027] Figure 4 is the UV-visible absorption spectrum before and after adjusting the valence state of vanadium ions in the solution in Example 4. DETAILED DESCRIPTION

[0028] Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein the examples of embodiments are shown in the accompanying drawings. The embodiments described below with reference to the attached drawing figures are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0029] The method for adjusting the valence state of vanadium ions in a solution according to an embodiment of the present application comprises the following steps:

[0030] (1) adding a hydroxylamine compound into a vanadium-containing solution and reacting;

[0031] (2) adding an acid into the solution obtained in step (1) and reacting to obtain a tetravalent vanadium ion solution.

[0032] The method for adjusting the valence state of vanadium ions in a solution according to an embodiment of the present application uses a hydroxylamine compound as an adjusting agent, and adjusts the pH value of the solution by adding an acid, so as to uniformly adjust the solution containing vanadium ions in any valence state into a tetravalent vanadium solution. The hydroxylamine compound has an electrode potential between ψ(V 3+ ) and ψ(V 5+ ) under acidic conditions, and thus can oxidize trivalent vanadium ions into tetravalent vanadium ions as a weak oxidizing agent when coexisting with trivalent vanadium ions, and can reduce pentavalent vanadium ions into tetravalent vanadium ions as a reducing agent when coexisting with pentavalent vanadium ions. Adjusting the pH value of the solution by adding an acid helps the electrode potential of the hydroxylamine compound to be between ψ(V 3+ ) and ψ(V 5+The method can be carried out at room temperature, is simple to operate, and can effectively reduce the cost of vanadium ion valence state adjustment. The method can be applied to vanadium-containing solutions with unknown vanadium ion valence states or solutions possibly containing vanadium ions with multiple different valence states. The method does not need to detect and quantitatively analyze the valence state and valence state composition of vanadium ions in the solution in advance, and can uniformly adjust vanadium ions with any valence state to tetravalent vanadium ions. The final solution contains only tetravalent vanadium ions. The method is simple to operate, efficient, and low in cost, and is conducive to promoting the rapid and efficient adjustment of the valence state of vanadium ions in the solution and improving the preparation or recycling efficiency of vanadium compounds.

[0033] In some embodiments, the vanadium-containing solution in step (1) is a vanadium-containing solution with unknown vanadium ion valence states, and optionally, the vanadium-containing solution is a vanadium-containing solution with unknown vanadium ion valence state composition. In the embodiments of the present application, the method can be applied to solutions containing vanadium ions with different valence states, especially vanadium-containing solutions with unknown valence state composition, and the method does not need to detect the valence state and valence state composition of vanadium ions in the solution in advance. Any valence state of vanadium ions in the solution can be uniformly adjusted to tetravalent vanadium ions, and the final solution contains only tetravalent vanadium ions.

[0034] In some embodiments, the vanadium-containing solution in step (1) contains at least one of divalent vanadium ions, trivalent vanadium ions, tetravalent vanadium ions, and pentavalent vanadium ions, and optionally, the vanadium-containing solution contains divalent vanadium ions and trivalent vanadium ions or the vanadium-containing solution contains trivalent vanadium ions and tetravalent vanadium ions or the vanadium-containing solution contains tetravalent vanadium ions and pentavalent vanadium ions. In the embodiments of the present application, the method can be applied to solutions containing vanadium ions with different valence states, for example, one or two, and any valence state of vanadium ions in the solution can be uniformly adjusted to tetravalent vanadium ions, without the need to obtain tetravalent vanadium ions by separate reduction or oxidation for a single valence state of vanadium ions, or the need to detect the valence state of vanadium ions in the solution in advance to determine the adjustment steps to be taken.

[0035] In some embodiments, the vanadium-containing solution in step (1) includes at least one of vanadium trichloride, vanadyl sulfate, vanadyl oxalate, sodium metavanadate, ammonium metavanadate, vanadium battery electrolyte, and vanadium-containing waste liquid, and the vanadium-containing waste liquid includes at least one of vanadium battery waste electrolyte and vanadium-containing leaching solution.

[0036] In some embodiments, the hydroxylamine compound in step (1) includes at least one of hydroxylamine, hydroxylamine hydrochloride, hydroxylamine sulfate, and hydroxylamine phosphate.

[0037] In some embodiments, in the step (1), the hydroxylamine compound is in a hydroxylamine compound solution, and the concentration of the hydroxylamine compound solution is 0.5-2 mol / L, specifically, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, or 2 mol / L; and the solvent is water, optionally, deionized water.

[0038] In some embodiments, in the step (1), the molar ratio of the hydroxylamine compound to vanadium ions is 0.5-3:1, specifically, for example, 0.5:1, 0.75:1, 1:1, 1.5:1, 2:1, 2.5:1, or 3:1. In the embodiments of the present application, by optimizing the molar ratio of the hydroxylamine compound to vanadium ions in the vanadium-containing solution, the electrode potential of the hydroxylamine compound is adjusted. At the same time, it is beneficial to the full reaction at a lower cost. When the amount of hydroxylamine compound is too high, it will cause a certain waste; when the amount of hydroxylamine compound is too low, it may cause incomplete reaction.

[0039] In some embodiments, in the step (1), the reaction time is 0.5-2 h, specifically, for example, 0.5 h, 1 h, 1.5 h, or 2 h. In the embodiments of the present application, by optimizing the reaction time, the vanadium ions in the solution are fully adjusted.

[0040] In some embodiments, in the step (1), the reaction is carried out at room temperature.

[0041] In some embodiments, in the step (2), an acid is added to the solution obtained in the step (1) until the pH value is 0.1-1.2, specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, or 1.2, optionally, 0.1-0.6. In the embodiments of the present application, by optimizing the pH value after adding the acid, the auxiliary role of the acid in the valence adjustment reaction is fully played. When the pH is too high or too low, it is not conducive to adjusting the electrode potential of the hydroxylamine compound between ψ(V 3+ ) and ψ(V 5+ ), and further not conducive to adjusting the tetravalent vanadium ions, and at the same time, excessive acid is not conducive to the preparation of subsequent compounds.

[0042] In some embodiments, in the step (2), after the acid is added to the solution obtained in the step (1), the electrode potential of the hydroxylamine compound is between ψ(V 3+ ) and ψ(V 5+ ). In the embodiments of the present application, it is beneficial to uniformly adjust the vanadium ions of any valence in any vanadium ion solution to tetravalent, and the existing form of vanadium ions in the final solution is only tetravalent.

[0043] In some embodiments, the hydroxylamine compound is an oxidizing agent or a reducing agent. In the embodiments of the present application, the hydroxylamine compound acts as an oxidizing agent when the vanadium ion in the solution of unknown valence state is in the form of trivalent vanadium ion, and acts as a reducing agent when the vanadium ion in the solution of unknown valence state is in the form of pentavalent vanadium ion.

[0044] In some embodiments, the acid in step (2) comprises at least one of hydrochloric acid and sulfuric acid.

[0045] In some embodiments, the concentration of the acid in step (2) is 2-6 mol / L, specifically, for example, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or 6 mol / L.

[0046] In some embodiments, the reaction time in step (2) is 1-2 h, specifically, for example, 1 h, 1.5 h, or 2 h.

[0047] In some embodiments, the reaction in step (2) is carried out at room temperature.

[0048] The present application is described below with reference to specific embodiments, which are merely illustrative and not in any way limiting the present application.

[0049] Embodiment 1

[0050] A method for adjusting the valence state of vanadium ions in a solution, comprising the following steps:

[0051] (1) 6.1 g of sodium metavanadate was dissolved in 50 mL of deionized water at room temperature to prepare a sodium metavanadate solution as a vanadium-containing solution. 6.15 g of hydroxylamine sulfate was dissolved in 30 mL of deionized water at room temperature.

[0052] The hydroxylamine sulfate solution was added to the sodium metavanadate solution, and the molar ratio of hydroxylamine sulfate to vanadium ion was 0.75:1. The reaction was stirred at room temperature for 1.5 h.

[0053] (2) Then, 6 mol / L dilute sulfuric acid solution was added dropwise to the mixed solution of hydroxylamine and sodium metavanadate while stirring until the pH value was 0.3. The reaction was continued for 1 h, and after the reaction was completed, a blue pentavalent vanadium solution was obtained.

[0054] Figure 1is the UV-Vis absorption spectrum of the sodium metavanadate solution before and after adjusting the valence state of vanadium ions in Example 1, which is used to characterize the valence state of vanadium ions in the solution. It can be seen that the solution after the reaction has a strong absorption peak at a wavelength of 764 nm and a shoulder peak near 630 nm, which is consistent with the UV-Vis absorption spectrum of pure tetravalent vanadium ions. Therefore, it can be judged that the vanadium ions in the sodium metavanadate solution have been completely converted into tetravalent vanadium ions.

[0055] Example 2

[0056] A method for adjusting the valence state of vanadium ions in a solution, comprising the following steps:

[0057] (1) Take 50 mL of the tervalent vanadium electrolyte obtained after electrolysis (1.6 mol / L) in a beaker. Take 10 mL of hydroxylamine (50% solution in H2O) in a beaker and dilute to 100 mL with deionized water.

[0058] Add the dilute hydroxylamine solution to the tervalent vanadium electrolyte, and the molar ratio of hydroxylamine to vanadium ions is about 2:1. Stir at room temperature for 1 h;

[0059] (2) Then add 2 mol / L dilute sulfuric acid solution to the mixed solution of hydroxylamine and tervalent vanadium electrolyte while stirring until the pH value is 0.1. Continue to stir for 1.5 h. After the reaction is completed, a blue tetravalent vanadium solution is obtained.

[0060] Figure 2 is the UV-Vis absorption spectrum of the tervalent vanadium electrolyte before and after adjusting the valence state of vanadium ions in Example 2, which is used to characterize the valence state of vanadium ions in the solution. It can be seen that the tervalent vanadium electrolyte has two absorption peaks at wavelengths of 400 nm and 611 nm, which is consistent with the UV-Vis absorption spectrum of pure tervalent vanadium ions. After the reaction is completed, the characteristic peak of tervalent vanadium ions disappears and a characteristic peak of tetravalent vanadium ions appears, indicating that the tervalent vanadium ions in the tervalent vanadium electrolyte have been converted into tetravalent vanadium ions.

[0061] Example 3

[0062] A method for adjusting the valence state of vanadium ions in a solution, comprising the following steps:

[0063] (1) Take 50 mL of the tervalent vanadium electrolyte obtained after electrolysis (1.6 mol / L) in a beaker. Take 10 mL of hydroxylamine (50% solution in H2O) in a beaker and dilute to 100 mL with deionized water.

[0064] Pour the hydroxylamine solution into the vanadium-containing waste liquid, and the molar ratio of hydroxylamine to vanadium ions is 1:1. Stir at room temperature for 0.5 h;

[0065] (2) After that, 4 mol / L dilute hydrochloric acid solution was added dropwise into the mixed solution of hydroxylamine sulfate and vanadium-containing waste solution under stirring until the pH value was 0.6, then the reaction was continued to stir for 2 h. After the reaction was completed, a blue tetravalent vanadium solution was obtained.

[0066] Figure 3 The UV-Vis absorption spectra of the vanadium-containing waste solution before and after adjusting the valence state of vanadium ions in Example 3 were used to characterize the valence state of vanadium ions in the solution. It can be seen that there are characteristic peaks of both trivalent vanadium ions and tetravalent vanadium ions in the vanadium-containing waste solution, indicating that there are trivalent and tetravalent vanadium ions in the vanadium-containing waste solution. After the reaction was completed, the characteristic peak of trivalent vanadium ions disappeared, and only the characteristic peak of tetravalent vanadium ions remained, so the vanadium ions in the vanadium-containing waste solution were completely converted into tetravalent vanadium ions.

[0067] Example 4

[0068] The method was completely the same as that of Example 2, except that in step (1), vanadium trichloride solution was used as the vanadium-containing solution, and 12.58 g of vanadium trichloride was taken in 50 mL of deionized water.

[0069] Figure 4 The UV-Vis absorption spectra of vanadium trichloride before and after adjusting the valence state of vanadium ions in Example 4 were used to characterize the valence state of vanadium ions in the solution. It can be seen that there is a strong absorption peak near 430 nm wavelength in vanadium trichloride, which is different from the UV-Vis absorption spectrum of pure trivalent vanadium ions. This is because dilute sulfuric acid needs to be added to the vanadium trichloride solution to help characterize the intrinsic valence state of vanadium ions in vanadium trichloride. After adding dilute sulfuric acid, the solution has two absorption peaks at 400 nm and 616 nm wavelengths, which is consistent with the UV-Vis absorption spectrum of pure trivalent vanadium ions. The absorption peak of trivalent vanadium ions disappears in the solution after the reaction is completed, and a characteristic peak of tetravalent vanadium ions appears, indicating that the vanadium ions in the vanadium trichloride solution have been converted into tetravalent vanadium ions.

[0070] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the skilled person in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0071] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary, and are not to be construed as limiting the present application, and any changes, modifications, replacements, and variations of the above embodiments made by those skilled in the art are within the scope of the present application.

Claims

1. A method of adjusting the valence state of vanadium ions in a solution, characterized by, The method comprises the following steps: (1) adding a hydroxylamine compound into a vanadium-containing solution and reacting; The vanadium-containing solution is a vanadium-containing solution with unknown valence state of vanadium ions; (2) adding acid to the solution obtained in step (1) and reacting to obtain a solution of tetravalent vanadium ions; adding acid to the solution obtained in step (1) until the pH value is 0.1-1.2; in the step (2), the reaction is carried out at room temperature; after adding acid to the solution obtained in step (1), the electrode potential of the hydroxylamine compound is between ψ(V 3+ ) and ψ(V 5 + ).

2. The method of adjusting the valence state of vanadium ions in solution according to claim 1, characterized in that, In the step (1), the vanadium-containing solution contains at least one of divalent vanadium ions, trivalent vanadium ions, tetravalent vanadium ions and pentavalent vanadium ions.

3. The method of adjusting the valence state of vanadium ions in solution of claim 1, wherein, In the step (1), the vanadium-containing solution includes at least one of vanadium trichloride, vanadyl sulfate, oxalate vanadyl, sodium metavanadate, ammonium metavanadate and vanadium battery electrolyte.

4. The method of adjusting the valence state of vanadium ions in solution of claim 1, wherein, In the step (1), the vanadium-containing solution includes vanadium-containing waste liquid.

5. The method of adjusting the valence state of vanadium ions in solution according to claim 4, characterized in that, The vanadium-containing waste liquid includes at least one of vanadium battery waste electrolyte and vanadium-containing leaching solution.

6. The method of adjusting the valence state of vanadium ions in solution of claim 1, wherein, In the step (1), the hydroxylamine compound includes at least one of hydroxylamine, hydroxylamine hydrochloride, hydroxylamine sulfate and hydroxylamine phosphate. And / or, the hydroxylamine compound is in the form of a hydroxylamine compound solution, and the concentration of the hydroxylamine compound solution is 0.5-2 mol / L.

7. The method of adjusting the valence state of vanadium ions in solution of claim 1, wherein, In the step (1), the molar ratio of the hydroxylamine compound to vanadium ions in the vanadium-containing solution is 0.5-3:

1.

8. The method of adjusting the valence state of vanadium ions in solution of claim 1, wherein, In the step (1), the reaction time is 0.5-2 h.

9. The method of adjusting the valence state of vanadium ions in solution of claim 1, wherein, In the step (2), the hydroxylamine compound is an oxidizing agent or a reducing agent.

10. The method of adjusting the valence state of vanadium ions in solution of claim 1, wherein, In the step (2), the acid includes at least one of hydrochloric acid and sulfuric acid. And / or, the concentration of the acid is 2-6 mol / L.

11. The method of adjusting the valence state of vanadium ions in solution of claim 1, wherein, In the step (2), the reaction time is 1-2 h.

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