Vanadyl sulfate and a method for preparing the same

Abstract

The application discloses vanadyl sulfate and a preparation method thereof. The preparation method comprises the following steps: adding a hydroxylamine compound into a vanadium-containing solution to react; adding acid into the obtained solution to react, so as to obtain a tetravalent vanadium ion solution; adding an alkali solution into the tetravalent vanadium ion solution to react, filtering, and obtaining a precipitate; dissolving the precipitate by using sulfuric acid to obtain a solution; evaporating and crystallizing the solution to obtain vanadyl sulfate. The method of the application uses a hydroxylamine compound as an adjusting agent, adjusts the pH value by adding acid, and adjusts the vanadium ions in the solution into tetravalent vanadium ions, which is suitable for a solution containing vanadium ions with any valence, especially a vanadium-containing solution with unknown valence composition of vanadium ions or a solution possibly containing vanadium ions with different valences, and the valence and valence composition of vanadium ions in the solution do not need to be detected and quantitatively analyzed in advance. The method of precipitating by adding alkali and then dissolving can effectively separate impurities. The method of segmental evaporation and crystallization can obtain flaky vanadyl sulfate crystals.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vanadyl sulfate, in particular, the present application relates to a kind of vanadyl sulfate and its preparation method. BACKGROUND

[0002] Vanadyl sulfate, also known as vanadic sulfate, is an inorganic compound with the chemical formula VOSO4. It is mainly used as a raw material for electrolyte in vanadium flow battery, a mordant, a catalytic reducing agent, and a colorant for ceramics and glass. In recent years, with the continuous development of related industries such as vanadium flow battery, the demand for vanadyl sulfate has been increasing year by year.

[0003] Currently, the preparation method of vanadyl sulfate includes dissolving vanadium pentoxide with sulfuric acid, adding a reducing agent to reduce it to a tetravalent vanadium solution, and finally obtaining vanadyl sulfate through crystallization. The raw material is basically vanadium pentoxide, which is relatively single. CN105776332B discloses a preparation method of vanadyl sulfate crystal. Vanadium pentoxide and sulfuric acid are added to a reaction kettle and mixed uniformly. A reducing gas such as sulfur dioxide or hydrogen sulfide is introduced, and vanadyl sulfate crystal is obtained after reduction and heating. The reducing gas such as sulfur dioxide or hydrogen sulfide used in this method has high cost and can easily cause air pollution. Other reducing agents such as oxalic acid can have problems such as difficulty in removing residual reducing agents. In addition, vanadyl sulfate can also be prepared by electrolyzing vanadium pentoxide and sulfuric acid, but the energy consumption is high and not suitable for large-scale production. SUMMARY

[0004] The present application is based on the inventors' discovery and understanding of the following facts and problems. Currently, the preparation method of vanadyl sulfate basically uses vanadium pentoxide as the raw material, which is relatively single and has high cost. The reducing agent is easy to remain, causing pollution, etc.

[0005] The present application aims to at least partially solve one of the technical problems in the related art. To this end, the embodiments of the present application propose a vanadyl sulfate and a preparation method thereof. A hydroxylamine compound is used as a regulator, the pH value is adjusted by adding acid, the vanadium ions of any valence in the solution are uniformly adjusted to tetravalent vanadium ions, then vanadium is precipitated by adding alkali, and the precipitate is dissolved in sulfuric acid to obtain vanadyl sulfate crystal by evaporation and crystallization. The method of the present application is suitable for solutions containing vanadium ions of any valence, especially solutions containing vanadium ions of unknown valence or solutions possibly containing vanadium ions of different valences, and does not need to detect and quantitatively analyze the valence and valence composition of vanadium ions in the solution in advance. The impurities can be effectively separated by precipitation and dissolution. The flaky vanadyl sulfate crystal can be obtained by stepwise evaporation and crystallization.

[0006] The preparation method of vanadyl sulfate according to an embodiment of the present application includes the following steps:

[0007] (1) adding a hydroxylamine compound into a vanadium-containing solution, and reacting;

[0008] (2) adding an acid into the solution obtained in step (1), and reacting to obtain a tetravalent vanadium ion solution;

[0009] (3) adding a base solution into the tetravalent vanadium ion solution, and reacting, and filtering to obtain a precipitate;

[0010] (4) dissolving the precipitate in sulfuric acid to obtain a solution, and evaporating and crystallizing the solution to obtain vanadyl sulfate.

[0011] The preparation method of vanadyl sulfate according to the embodiment of the present application has the following advantages and technical effects: the hydroxylamine compound is used as a regulator, the pH value of the solution is adjusted by adding an acid, the solution containing vanadium ions in any valence state is uniformly adjusted to tetravalent vanadium ions to obtain a tetravalent vanadium solution, wherein the electrode potential of the hydroxylamine compound under acidic conditions can be between ψ(V 3+ ) and ψ(V 5+ ), so that the hydroxylamine compound can act as a weak oxidizing agent to oxidize trivalent vanadium ions to tetravalent vanadium ions when coexisting with the trivalent vanadium ions, and can act as a reducing agent to reduce pentavalent vanadium ions to tetravalent vanadium ions when coexisting with the pentavalent vanadium ions, and the adjustment of the pH value 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+ ), thereby playing an auxiliary role in the adjustment of the valence state. Then, vanadium is precipitated by adding a base in the tetravalent vanadium solution, the precipitate is dissolved in dilute sulfuric acid to obtain a vanadyl sulfate solution, and finally the vanadyl sulfate crystal is prepared by evaporating the solution.

[0012] In the embodiment of the present application, the vanadium raw material can be a solution containing vanadium ions in any valence state, especially a solution containing vanadium ions in unknown valence state or a solution possibly containing vanadium ions in multiple different valence states, and it is not necessary to detect and quantitatively analyze the valence state and valence composition of the vanadium ions in the solution in advance, but the vanadium ions in any valence state in the solution are uniformly adjusted to tetravalent vanadium ions to obtain a tetravalent vanadium solution, thereby greatly widening the selection range of the vanadium raw material.

[0013] In the embodiment of the present application, the method of precipitating by adding a base and then dissolving in dilute sulfuric acid can effectively separate vanadyl sulfate from the excess regulator and other impurities that may exist, thereby avoiding the problem that the excess regulator is difficult to remove. The method is simple in operation, high in efficiency and low in cost, and is conducive to promoting the fast and efficient preparation of vanadyl sulfate crystals.

[0014] In some embodiments, in step (1), the vanadium-containing solution is a vanadium-containing solution with unknown valence state of vanadium ions.

[0015] 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.

[0016] In some embodiments, in the step (1), the vanadium-containing solution comprises at least one of vanadium trichloride, vanadyl sulfate, vanadyl oxalate, vanadium pentoxide, 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.

[0017] In some embodiments, in the step (1), the hydroxylamine compound comprises at least one of hydroxylamine, hydroxylamine hydrochloride, hydroxylamine sulfate, hydroxylamine phosphate;

[0018] And / or, the hydroxylamine compound adopts a hydroxylamine compound solution, and the concentration of the hydroxylamine compound solution is 0.5-3 mol / L;

[0019] And / or, the molar ratio of the hydroxylamine compound to vanadium ions in the vanadium-containing solution is 0.5-3:1.

[0020] In some embodiments, in the step (1), the reaction time is 0.5-2 h.

[0021] 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;

[0022] And / or, the acid comprises at least one of hydrochloric acid and sulfuric acid;

[0023] And / or, the concentration of the acid is 2-6 mol / L;

[0024] And / or, in the step (2), the reaction time is 12-24 h.

[0025] 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+ ).

[0026] In some embodiments, the hydroxylamine compound is an oxidizing agent or a reducing agent.

[0027] In some embodiments, in the step (3), a base solution is added to the tetravalent vanadium ion solution until the pH value is 4-6;

[0028] And / or, the base solution comprises at least one of sodium hydroxide solution and potassium hydroxide solution;

[0029] And / or, in the step (3), the reaction time is 10-30 min.

[0030] In some embodiments, in the step (4), the concentration of the sulfuric acid is 2-6 mol / L.

[0031] And / or, the molar ratio of the sulfuric acid to vanadium is 1-1.1:1.

[0032] In some embodiments, in the step (4), the evaporative crystallization comprises two evaporative crystallization stages, the temperature of the first evaporative crystallization stage is higher than the temperature of the second evaporative crystallization stage.

[0033] Preferably, the temperature of the first evaporative crystallization stage is 110-150℃; the time of the first evaporative crystallization stage is 4-8h.

[0034] The temperature of the second evaporative crystallization stage is 70-90℃; the time of the second evaporative crystallization stage is 16-22h.

[0035] Preferably, the flaky vanadyl sulfate crystals are obtained by the evaporative crystallization through the two evaporative crystallization stages.

[0036] The embodiment of the present application provides a vanadyl sulfate, which is prepared by the preparation method of the embodiment of the present application. In the embodiment of the present application, the vanadium ions of any valence in the solution are uniformly adjusted to tetravalent to obtain a tetravalent vanadium solution. The vanadyl sulfate and possible impurities such as excess adjusting agent can be effectively separated by adding alkali to precipitate and then dissolving in dilute sulfuric acid, thereby avoiding the problem that the excess adjusting agent is difficult to remove. The preparation cost of the vanadyl sulfate is low, and the efficiency is high, which is conducive to promoting the fast and efficient preparation of vanadyl sulfate crystals. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is the ultraviolet-visible absorption spectrum of the solution obtained after the precipitation in Example 1 is completely dissolved in dilute sulfuric acid.

[0038] Figure 2 is the XRD pattern of the vanadyl sulfate crystals prepared in Example 1.

[0039] Figure 3 is the SEM image of the vanadyl sulfate crystals prepared in Example 1.

[0040] Figure 4 is the SEM image of the vanadyl sulfate crystals prepared in Example 1. DETAILED DESCRIPTION

[0041] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0042] The preparation method of vanadyl sulfate according to the embodiment of the present application comprises the following steps:

[0043] (1) adding a hydroxylamine compound into a vanadium-containing solution and reacting;

[0044] (2) adding an acid into the solution obtained in step (1) and reacting to obtain a tetravalent vanadium ion solution;

[0045] (3) adding an alkali solution into the tetravalent vanadium ion solution and reacting, and filtering to obtain a precipitate;

[0046] (4) dissolving the precipitate with sulfuric acid to obtain a solution, and evaporating and crystallizing the solution to obtain vanadyl sulfate.

[0047] The preparation method of vanadyl sulfate according to the embodiment of the present application uses a hydroxylamine compound as a regulator, adjusts the pH value of the solution by adding an acid, and adjusts the vanadium ions of any valence in the solution to tetravalent vanadium ions to obtain 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 to tetravalent vanadium ions as a weak oxidizing agent when coexisting with the trivalent vanadium ions, and can reduce pentavalent vanadium ions to tetravalent vanadium ions as a reducing agent when coexisting with the pentavalent vanadium ions. Adjusting the pH value 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+ ), and plays an auxiliary role in the valence adjustment process. Then, vanadium is precipitated by adding an alkali in the tetravalent vanadium solution, the precipitate is dissolved in dilute sulfuric acid to obtain a vanadyl sulfate solution, and finally the vanadyl sulfate crystal is prepared by evaporating the solution.

[0048] In the embodiment of the present application, the vanadium raw material can be 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 different valences, and it is not necessary to detect and quantitatively analyze the valence and valence composition of vanadium ions in the solution in advance. The vanadium ions of any valence in the solution are adjusted to tetravalent vanadium ions to obtain a tetravalent vanadium solution, which greatly widens the selection range of vanadium raw materials.

[0049] In the embodiment of the present application, the method of precipitating by adding an alkali and then dissolving in dilute sulfuric acid can effectively separate vanadyl sulfate from excess regulators and other impurities that may exist, avoiding the problem that the excess regulators are difficult to remove. The method is simple, efficient and low in cost, and is conducive to promoting the rapid and efficient preparation of vanadyl sulfate crystals.

[0050] In some embodiments, in step (1), the vanadium-containing solution is a vanadium-containing solution with unknown valence of vanadium ions.

[0051] 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, optionally, the vanadium-containing solution comprises divalent vanadium ions and trivalent vanadium ions or the vanadium-containing solution comprises trivalent vanadium ions and tetravalent vanadium ions or the vanadium-containing solution comprises tetravalent vanadium ions and pentavalent vanadium ions. In the embodiments of the present application, the method of the present application can be applied to a solution containing vanadium ions of multiple different valences, for example, one or two, and any valence of vanadium ions in the solution can be adjusted to tetravalent, without the need to obtain tetravalent vanadium ions by separate reduction or oxidation for a single valence of vanadium ions, nor the need to detect the valence of vanadium ions in the solution in advance to determine the adjustment steps to be taken.

[0052] In some embodiments, in the step (1), the vanadium-containing solution comprises at least one of vanadium trichloride, vanadyl sulfate, oxalate vanadyl, vanadium pentoxide, sodium metavanadate, ammonium metavanadate, vanadium battery electrolyte, vanadium-containing waste solution, and the vanadium-containing waste solution comprises at least one of vanadium battery waste electrolyte and vanadium-containing leaching solution. In the embodiments of the present application, the vanadium raw material used can be a solution containing vanadium ions of any valence, in particular, a solution containing vanadium ions of unknown valence composition or a solution possibly containing vanadium ions of multiple different valences, and there is no need to detect and quantitatively analyze the valence and valence composition of vanadium ions in the solution in advance, greatly widening the selection range of vanadium raw materials.

[0053] In some embodiments, in the step (1), the hydroxylamine compound comprises at least one of hydroxylamine, hydroxylamine hydrochloride, hydroxylamine sulfate, and hydroxylamine phosphate;

[0054] And / or, the hydroxylamine compound is in a hydroxylamine compound solution, the concentration of the hydroxylamine compound solution is 0.5-3 mol / L, specifically, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, and the solvent is water, optionally, deionized water;

[0055] And / or, the molar ratio of the hydroxylamine compound to vanadium ions in the vanadium-containing solution is 0.5-3:1, specifically, for example, 0.5:1, 0.75:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1. In the embodiments of the present application, by optimizing the molar ratio of the hydroxylamine compound to vanadium ions, the electrode potential of the hydroxylamine compound is facilitated. At the same time, it is beneficial to the reaction to proceed fully at a lower cost. When the amount of the hydroxylamine compound is too high, it will cause a certain waste; when the amount of the hydroxylamine compound is too low, it may cause incomplete reaction.

[0056] In some embodiments, in the step (1), the reaction time is 0.5-2h, specifically, for example, 0.5h, 1h, 1.5h, 2h. In the embodiments of the present application, by preferably the reaction time, it is beneficial to the full adjustment of vanadium ions in the solution.

[0057] In some embodiments, in the step (1), the reaction is carried out at room temperature.

[0058] 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, 1.2, optionally, 0.1-0.6;

[0059] And / or, the acid comprises at least one of hydrochloric acid, sulfuric acid;

[0060] And / or, the concentration of the acid is 2-6mol / L, specifically, for example, 2mol / L, 3mol / L, 4mol / L, 5mol / L, 6mol / L. In the embodiments of the present application, by preferably the pH value after adding the acid, it is beneficial to the full play of the auxiliary role of the acid in the valence adjustment reaction. When the pH is too high or too low, it is not conducive to adjusting the electrode potential of the hydroxylamine compound to be between ψ(V 3+ ) and ψ(V 5 + ), and further not conducive to adjusting to obtain tetravalent vanadium ions, and meanwhile, excessive acid is not conducive to the subsequent preparation of compounds.

[0061] In some embodiments, in the step (2), the reaction time is 12-24h, specifically, for example, 12h, 15h, 18h, 21h, 24h.

[0062] In some embodiments, in the step (2), the reaction is carried out at room temperature.

[0063] 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 adjusting 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.

[0064] 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 solution with unknown valence of vanadium ions contains vanadium ions with valence of 3, and acts as a reducing agent when the solution with unknown valence of vanadium ions contains vanadium ions with valence of 5.

[0065] In some embodiments, in step (3), the alkaline solution is added to the solution of vanadium ions with valence of 4 until the pH value is 4-6, specifically, for example, 4, 4.5, 5, 5.5, 6.

[0066] And / or, the alkaline solution comprises at least one of sodium hydroxide solution and potassium hydroxide solution.

[0067] And / or, in step (3), the reaction time is 10-30 min, specifically, for example, 10 min, 20 min, 30 min.

[0068] In some embodiments, in step (4), the concentration of sulfuric acid is 2-6 mol / L, specifically, for example, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L.

[0069] And / or, the molar ratio of sulfuric acid to vanadium is 1-1.1:1, specifically, for example, 1:1, 1.05:1, 1.1:1.

[0070] In some embodiments, in step (4), the evaporation crystallization comprises two evaporation crystallization stages, and the temperature of the first evaporation crystallization stage is higher than that of the second evaporation crystallization stage.

[0071] Preferably, the temperature of the first evaporation crystallization stage is 110-150℃, specifically, for example, 110℃, 120℃, 130℃, 140℃, 150℃, and the time of the first evaporation crystallization stage is 4-8 h, specifically, for example, 4 h, 5 h, 6 h, 7 h, 8 h.

[0072] The temperature of the second evaporation crystallization stage is 70-90℃, specifically, for example, 70℃, 80℃, 90℃, and the time of the second evaporation crystallization stage is 16-22 h, specifically, for example, 16 h, 18 h, 20 h, 22 h.

[0073] Preferably, the vanadyl sulfate crystals obtained by the evaporation crystallization of the two evaporation crystallization stages are in the form of flakes.

[0074] Preferably, the evaporation crystallization is carried out in an oven.

[0075] The embodiment of the present application provides a vanadyl sulfate, which is prepared by adopting the preparation method of the embodiment of the present application. In the embodiment of the present application, vanadium ions of any valence in a solution are uniformly adjusted to be tetravalent to obtain a tetravalent vanadium solution. The vanadyl sulfate and impurities such as excess adjusting agents that may exist can be effectively separated by adding alkali to precipitate and then dissolving in dilute sulfuric acid, thereby avoiding the problem that the excess adjusting agents are difficult to remove. The vanadyl sulfate has low preparation cost and high efficiency, and is beneficial to promoting the fast and efficient preparation of vanadyl sulfate crystals.

[0076] In some embodiments, the vanadyl sulfate is a flaky vanadyl sulfate crystal.

[0077] In some embodiments, the vanadyl sulfate is composed of flaky particles, and the diameter of the flaky particles is 1-7 μm, preferably 3-4 μm.

[0078] The present application is described below with reference to specific embodiments, and it should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0079] Embodiment 1

[0080] A preparation method of vanadyl sulfate, comprising the following steps:

[0081] (1) 6.1 g of sodium metavanadate is taken in 50 mL of deionized water, and the mixture is stirred and dissolved at room temperature to prepare a sodium metavanadate solution as a vanadium-containing solution. 6.15 g of hydroxylamine sulfate is dissolved in 30 mL of deionized water, and then the solution is added to the sodium metavanadate solution, and the molar ratio of the hydroxylamine sulfate to vanadium ions is 0.75:1. The mixture is stirred and reacted at room temperature for 1.5 h;

[0082] (2) Then, 6 mol / L dilute sulfuric acid solution is added dropwise to the mixed solution of hydroxylamine sulfate and sodium metavanadate while stirring until the pH value is 0.3. Then, the mixture is continuously stirred and reacted for 24 h. After the reaction is completed, a blue tetravalent vanadium solution is obtained;

[0083] (3) Then, sodium hydroxide solution is added to the blue tetravalent vanadium solution while stirring until the pH value is 4.5. After 20 min of reaction, the mixture is subjected to suction filtration to obtain a gray precipitate;

[0084] (4) 6 mol / L dilute sulfuric acid solution is added to the gray precipitate to completely dissolve the precipitate, and the molar ratio of sulfuric acid to vanadium is 1.05:1. The obtained solution is placed in an oven for evaporation and crystallization. Specifically, the solution is kept at 120 ℃ for 6 h, and then kept at 80 ℃ for 18 h to prepare vanadyl sulfate crystals.

[0085] Figure 1The UV-Vis absorption spectrum of the solution obtained after adding dilute sulfuric acid to the precipitate in Example 1 to completely dissolve it was used to characterize the valence state of the vanadium ions in the solution. It can be seen that it has a strong absorption peak at a wavelength of 765 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 converted into tetravalent vanadium ions.

[0086] Figure 2 The XRD pattern of the vanadyl sulfate crystal prepared in Example 1 can be seen to be basically consistent with the standard diffraction peak of VOSO4·3H2O, confirming that the sample prepared is vanadyl sulfate trihydrate, and has good crystallinity.

[0087] Figure 3 and 4 The SEM image of the vanadyl sulfate crystal prepared in Example 1 can be seen to be composed of irregular flaky particles, most of which are in an upright state, with flaky particle diameters of about 3-4 μm.

[0088] Example 2

[0089] A method for preparing vanadyl sulfate, comprising the following steps:

[0090] (1) Using a used and discarded trivalent vanadium electrolyte as a vanadium-containing solution, 50 mL of the trivalent vanadium electrolyte (1.6 mol / L) was taken in a beaker, 10 mL of hydroxylamine (50% solution in H2O) was diluted to 100 mL with deionized water, and then added to the trivalent vanadium electrolyte, the molar ratio of the hydroxylamine to the vanadium ions was about 2:1, and the reaction was stirred at room temperature for 1 h;

[0091] (2) Then 2 mol / L dilute sulfuric acid solution was added dropwise to the mixed solution of hydroxylamine and trivalent vanadium electrolyte while stirring until the pH value was 0.1, and then the stirring reaction was continued for 18 h. After the reaction was completed, a blue tetravalent vanadium solution was obtained;

[0092] (3) Then potassium hydroxide solution was added to the blue tetravalent solution while stirring until the pH value was 5. After 30 min of reaction, the gray precipitate was obtained by suction filtration;

[0093] (4) 3 mol / L dilute sulfuric acid solution was added to the gray precipitate to completely dissolve it, and the molar ratio of sulfuric acid to vanadium was 1:1. The obtained solution was placed in an oven for evaporation and crystallization, wherein it was kept at 110°C for 8 h, and then kept at 70°C for 22 h to prepare vanadyl sulfate crystals.

[0094] Example 3

[0095] A method for preparing vanadyl sulfate, comprising the following steps:

[0096] (1) Vanadium-containing waste solution with unknown valence of vanadium ions as vanadium-containing solution, 50 mL of the vanadium-containing waste solution (0.8 mol / L) was taken in a beaker, 6.56 g of hydroxylamine sulfate was dissolved in 30 mL of deionized water, and then added to the vanadium-containing waste solution, the molar ratio of the hydroxylamine sulfate to vanadium ions was 1:1, and the reaction was stirred at room temperature for 0.5 h;

[0097] (2) Then 4 mol / L dilute hydrochloric acid solution was added dropwise to the mixed solution of hydroxylamine sulfate and vanadium-containing waste solution while stirring until the pH value was 0.6, and then the reaction was continuously stirred for 12 h, after the reaction was completed, a blue tetravalent vanadium solution was obtained;

[0098] (3) Then sodium hydroxide solution was added to the blue tetravalent solution while stirring until the pH value was 5.5, and after 10 min of reaction, the gray precipitate was obtained by suction filtration;

[0099] (4) 4 mol / L dilute sulfuric acid solution was added to the gray precipitate to completely dissolve it, wherein the molar ratio of sulfuric acid to vanadium was 1.1:1. The obtained solution was placed in an oven for evaporation and crystallization, wherein it was kept at 130°C for 4 h, and then kept at 90°C for 16 h, to obtain vanadyl sulfate crystals.

[0100] Example 4

[0101] The method of Example 2 was completely the same, 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.

[0102] Blue vanadyl sulfate crystals were prepared by Example 4.

[0103] 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, different embodiments or examples described in the present specification and the features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0104] Although the above embodiments have been shown and described, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and the changes, modifications, replacements and variations of the above embodiments made by those skilled in the art are within the protection scope of the present application.

Claims

1. A process for the preparation of vanadyl sulfate, characterized in that, The method comprises the following steps: (1) adding a hydroxylamine compound into a vanadium-containing solution and reacting, wherein the hydroxylamine compound comprises at least one of hydroxylamine, hydroxylamine hydrochloride, hydroxylamine sulfate and hydroxylamine phosphate, and the vanadium-containing solution is a vanadium-containing solution with unknown valence of vanadium ions; (2) Add acid to the solution obtained in step (1) until the pH value is 0.1-1.2, react, and obtain a tetravalent vanadium ion solution; 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+ The reaction takes place between ) and ); the reaction is carried out at room temperature; (3) adding an alkali solution into the tetravalent vanadium ion solution, reacting, filtering and obtaining a precipitate; (4) dissolving the precipitate with sulfuric acid to obtain a solution, evaporating and crystallizing the solution to obtain vanadyl sulfate.

2. The process for preparing vanadyl sulfate according to claim 1, characterized in that, In the step (1), the vanadium-containing solution comprises at least one of divalent vanadium ions, trivalent vanadium ions, tetravalent vanadium ions and pentavalent vanadium ions; and / or, the vanadium-containing solution comprises at least one of vanadium trichloride, vanadyl sulfate, oxalate vanadyl, vanadium pentoxide, sodium metavanadate, ammonium metavanadate, vanadium battery electrolyte and vanadium-containing waste liquid, wherein the vanadium-containing waste liquid comprises at least one of vanadium battery waste electrolyte and vanadium-containing leaching solution.

3. The process for preparing vanadyl sulfate according to claim 1, characterized by, In the step (1), the hydroxylamine compound is a hydroxylamine compound solution, and the concentration of the hydroxylamine compound solution is 0.5-3 mol / L; and / or, the molar ratio of the hydroxylamine compound to vanadium ions in the vanadium-containing solution is 0.5-3:1; and / or, in the step (1), the reaction time is 0.5-2 h.

4. The process for preparing vanadyl sulfate according to claim 1, characterized by, In the step (2), the acid comprises at least one of hydrochloric acid and sulfuric acid; and / or, the concentration of the acid is 2-6 mol / L; and / or, in the step (2), the reaction time is 12-24 h.

5. The process for preparing vanadyl sulfate according to claim 1, characterized by, In the step (2), the hydroxylamine compound is an oxidizing agent or a reducing agent.

6. The process for preparing vanadyl sulfate according to claim 1, characterized by, In the step (3), the alkali solution is added into the tetravalent vanadium ion solution until the pH value is 4-6; and / or, the alkali solution comprises at least one of sodium hydroxide solution and potassium hydroxide solution; and / or, in the step (3), the reaction time is 10-30 min.

7. The process for preparing vanadyl sulfate according to claim 1, characterized by, In the step (4), the concentration of the sulfuric acid is 2-6 mol / L; and / or, the molar ratio of the sulfuric acid to vanadium is 1-1.1:

1.

8. The process for preparing vanadyl sulfate according to claim 1, characterized by, In the step (4), the evaporation and crystallization comprises two evaporation and crystallization stages, and the temperature of the first evaporation and crystallization stage is higher than that of the second evaporation and crystallization stage.

9. The process for preparing vanadyl sulfate according to claim 8, characterized in that, The temperature of the first evaporation and crystallization stage is 110-150℃, and the time of the first evaporation and crystallization stage is 4-8 h; The temperature of the second evaporation and crystallization stage is 70-90℃, and the time of the second evaporation and crystallization stage is 16-22 h; and / or, the flaky vanadyl sulfate crystal is obtained through the evaporation and crystallization of the two evaporation and crystallization stages.

10. A vanadyl sulfate characterized in that, The vanadyl sulfate is prepared by the preparation method in any one of claims 1-9, and the evaporation and crystallization comprises two evaporation and crystallization stages, and the temperature of the first evaporation and crystallization stage is higher than that of the second evaporation and crystallization stage.

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