Method for reducing alkaline vanadium-containing solution during short-process preparation of vanadium electrolyte

Abstract

The invention relates to the technical field of preparation of an electrolyte for a vanadium redox flow battery, in particular to a reduction method of an alkaline vanadium-containing solution during short-process preparation of a vanadium electrolyte. The reduction method comprises the following steps: (1) adding a reducing agent sodium sulfite into an alkaline vanadium-containing solution and dissolving; and (2) acid is added into the solution obtained after dissolving in the step (1), the pH is adjusted, a reduction reaction is conducted, and vanadium is reduced to be tetravalent. The method provided by the invention effectively solves the problem of vanadium loss caused by precipitation generated in the sequential operation process of acidification and reduction of the alkaline vanadium-containing solution in the prior art, and meanwhile, the method provided by the invention is easy for engineering implementation.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing electrolytes for vanadium redox flow batteries, specifically to a method for reducing alkaline vanadium-containing solutions during the short-process preparation of vanadium electrolytes. Background Art

[0002] Vanadium redox flow batteries utilize the multivalent state characteristics of vanadium for electrochemical energy storage, and the preparation of vanadium electrolytes is one of the core links.

[0003] In the traditional preparation of vanadium electrolytes, vanadium-containing minerals or vanadium-containing slag are used as the starting materials. After adding sodium salts for oxidative roasting, leaching, impurity removal, adding ammonium salts for precipitation, and then roasting to obtain vanadium pentoxide, and then dissolving and reducing again to obtain vanadium electrolytes. Obviously, the traditional vanadium electrolyte preparation process has numerous steps, high energy consumption, and large pollution. In recent years, short-process vanadium electrolyte preparation technologies centered around extraction processes have received attention. After acidifying and reducing vanadium-containing solutions, acidic phosphorus extractants are used for extraction and separation to obtain vanadyl sulfate solutions in the form of stripping solutions.

[0004] The short-process vanadium electrolyte preparation technology has made significant technological progress, but there are still deficiencies in the reduction process of alkaline vanadium-containing solutions. When operating in the order of acidification and reduction, precipitates will be generated, resulting in vanadium loss. For example, CN 114243042 A discloses a method for preparing vanadium electrolytes. For the leaching solution after sodium roasting, it is first acidified with acid for precipitation and impurity removal, and then a reducing agent is added to reduce vanadium to tetravalent. The end point pH of acidification in this method is 1 - 4, and precipitates are generated during the acidification process. CN 107557598 B also discloses a method for preparing vanadium electrolytes. The alkaline vanadium-containing solution is acidified, and then a reducing agent is added to the vanadium-containing acidic solution to reduce vanadium to tetravalent. The pH is controlled at 0 - 3.5 during acidification, and some impurities precipitate out during the pH adjustment process. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of precipitation and vanadium loss during the acidification and reduction sequence operation of alkaline vanadium-containing solutions in the current short-process vanadium electrolyte preparation technology, and to provide a method for reducing alkaline vanadium-containing solutions during the short-process preparation of vanadium electrolytes. This method can better overcome the problems existing in the prior art, and no precipitates are generated during the process, effectively avoiding vanadium loss.

[0006] To achieve the above invention purposes, the specific technical solution of the present invention is as follows:

[0007] A method for reducing alkaline vanadium-containing solutions during the short-process preparation of vanadium electrolytes, comprising the following steps:

[0008] (1) Adding the reducing agent sodium sulfite to the alkaline vanadium-containing solution and dissolving it;

[0009] (2) Add an acid to the solution obtained in step (1) to adjust the pH and perform a reduction reaction to reduce vanadium to tetravalent.

[0010] Furthermore, in the reduction method of the alkaline vanadium-containing solution during the short-process preparation of vanadium electrolyte, the concentration of vanadium in the alkaline vanadium-containing solution described in step (1) is 1 - 30 g / L (specifically, it can be 1 g / L, 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, etc.); the reducing agent sodium sulfite is added to the alkaline vanadium-containing solution in its original form as an industrial-grade powdered solid, and the addition amount of sodium sulfite is 1.05 - 1.1 times the theoretical amount (specifically, it can be 1.05 times, 1.06 times, 1.07 times, 1.08 times, 1.09 times, 1.1 times, etc.).

[0011] Furthermore, in the reduction method of the alkaline vanadium-containing solution during the short-process preparation of vanadium electrolyte, when adding the reducing agent sodium sulfite in step (1), the pH value is not adjusted, and sodium sulfite only dissolves, and no precipitate is formed in the solution after adding sodium sulfite.

[0012] Furthermore, in the reduction method of the alkaline vanadium-containing solution during the short-process preparation of vanadium electrolyte, the acid added in step (2) is sulfuric acid, and its mass concentration is 93% or 98%.

[0013] Furthermore, in the reduction method of the alkaline vanadium-containing solution during the short-process preparation of vanadium electrolyte, after adding the acid in step (2), a reduction reaction of vanadium is carried out, and the pH value of the solution at the end point of the reduction reaction is not lower than 2.0, and more preferably the pH value is 2.0 - 3.0 (specifically, it can be 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, etc.).

[0014] Furthermore, in the reduction method of the alkaline vanadium-containing solution during the short-process preparation of vanadium electrolyte, after adding the acid in step (2), a reduction reaction of vanadium is carried out, and the pH value of the solution at the end point of the reduction reaction is 2.1.

[0015] Furthermore, in the reduction method of the alkaline vanadium-containing solution during the short-process preparation of vanadium electrolyte, after adding the acid in step (2), a reduction reaction of vanadium is carried out, and the pH value of the solution at the end point of the reduction reaction is 2.52.

[0016] Furthermore, in the reduction method of the alkaline vanadium-containing solution during the short-process preparation of vanadium electrolyte, after the acidification reduction reaction in step (2), vanadium is reduced to tetravalent, and no precipitate is formed during the reduction process.

[0017] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0018] In the method of the present invention, a reducing agent in the form of sodium sulfite is first added to an alkaline vanadium-containing solution for dissolution. During this process, no precipitation is formed, and there is no risk of a large amount of sulfur dioxide gas escaping. In the subsequent acidification process, the pH of the solution at the end point of the reduction reaction is controlled to be not lower than 2. No precipitation is formed during the reduction reaction. At the same time, the material added in the reduction reaction step is sulfuric acid in liquid form. Under normal pressure conditions, the transportation of the fluid and the sealing of the reaction vessel are easy to achieve. This method effectively solves the problem of precipitation formation and vanadium loss during the sequential operation of first acidifying and then reducing the alkaline vanadium-containing solution in the prior art. At the same time, the method proposed by the present invention is easy to implement in engineering. Detailed Embodiments

[0019] Example embodiments will now be described more fully. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more complete and comprehensive, and will fully convey the concept of the example embodiments to those skilled in the art.

[0020] In addition, the described features or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of this application. However, those skilled in the art will realize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, steps, etc. can be adopted. In other cases, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring aspects of this application.

[0021] The embodiments are only illustrative and not necessarily include all the contents and operations / steps, nor are they necessarily executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined. Therefore, the actual execution order may change according to the actual situation.

[0022] It should be noted that: "a plurality of" mentioned in this article refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0023] It should be noted that the order of the methods mentioned in the specification and claims of this application should be understood that the objects used in this way can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented in an order other than those described.

[0024] To make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0025] Example 1

[0026] The main components of the alkaline vanadium-containing solution are: vanadium 29.83 g / L, chromium 2.734 g / L, calcium 17.4 mg / L, iron 10.5 mg / L, and silicon 804.1 mg / L.

[0027] Take 400 mL of the alkaline vanadium-containing solution, calculate the theoretical amount of the reducing agent sodium sulfite according to the reduction of vanadium from pentavalent to tetravalent and chromium from hexavalent to trivalent, take 1.05 times the theoretical amount of sodium sulfite and add it to the alkaline vanadium-containing solution and stir to dissolve; slowly add industrial sulfuric acid with a mass concentration of 93% to the above solution, and the end-point pH of the solution is 2.52.

[0028] No precipitate is formed during the whole operation process.

[0029] Example 2

[0030] The main components of the alkaline vanadium-containing solution are: vanadium 27.88 g / L, chromium 3.39 g / L, calcium 25.3 mg / L, iron 43.5 mg / L, and silicon 845.2 mg / L.

[0031] Take 700 mL of the alkaline vanadium-containing solution, calculate the theoretical amount of the reducing agent sodium sulfite according to the reduction of vanadium from pentavalent to tetravalent and chromium from hexavalent to trivalent, take 1.1 times the theoretical amount of sodium sulfite and add it to the alkaline vanadium-containing solution and stir to dissolve; slowly add industrial sulfuric acid with a mass concentration of 98% to the above solution, and the end-point pH of the solution is 2.1.

[0032] No precipitate is formed during the whole operation process.

[0033] Example 3:

[0034] The main components of the alkaline vanadium-containing solution are: vanadium 25.83 g / L, chromium 3.534 g / L, calcium 22.4 mg / L, iron 30.45 mg / L, and silicon 852.1 mg / L.

[0035] Take 600 mL of the alkaline vanadium-containing solution, calculate the theoretical amount of the reducing agent sodium sulfite according to the reduction of vanadium from pentavalent to tetravalent and chromium from hexavalent to trivalent, take 1.07 times the theoretical amount of sodium sulfite and add it to the alkaline vanadium-containing solution and stir to dissolve; slowly add industrial sulfuric acid with a mass concentration of 93% to the above solution, and the end-point pH of the solution is 2.71.

[0036] No precipitation is formed during the whole operation process.

[0037] Example 4:

[0038] The main components of the alkaline vanadium-containing solution are: vanadium 29.83 g / L, chromium 2.734 g / L, calcium 17.4 mg / L, iron 10.5 mg / L, and silicon 804.1 mg / L.

[0039] Take 400 mL of the alkaline vanadium-containing solution, calculate the theoretical amount of the reducing agent sodium sulfite according to the reduction of vanadium from pentavalent to tetravalent and chromium from hexavalent to trivalent, take 1.07 times the theoretical amount of sodium sulfite and add it to the alkaline vanadium-containing solution and stir to dissolve; slowly add industrial sulfuric acid with a mass concentration of 98% to the above solution, and the pH at the end point of the solution is 2.36.

[0040] No precipitation is formed during the whole operation process.

[0041] Example 5:

[0042] The main components of the alkaline vanadium-containing solution are: vanadium 29.83 g / L, chromium 2.734 g / L, calcium 17.4 mg / L, iron 10.5 mg / L, and silicon 804.1 mg / L.

[0043] Take 600 mL of the alkaline vanadium-containing solution, calculate the theoretical amount of the reducing agent sodium sulfite according to the reduction of vanadium from pentavalent to tetravalent and chromium from hexavalent to trivalent, take 1.10 times the theoretical amount of sodium sulfite and add it to the alkaline vanadium-containing solution and stir to dissolve; slowly add industrial sulfuric acid with a mass concentration of 98% to the above solution, and the pH at the end point of the solution is 2.17.

[0044] No precipitation is formed during the whole operation process.

[0045] Example 6:

[0046] The main components of the alkaline vanadium-containing solution are: vanadium 27.88 g / L, chromium 3.39 g / L, calcium 25.3 mg / L, iron 43.5 mg / L, and silicon 845.2 mg / L.

[0047] Take 800 mL of the alkaline vanadium-containing solution, calculate the theoretical amount of the reducing agent sodium sulfite according to the reduction of vanadium from pentavalent to tetravalent and chromium from hexavalent to trivalent, take 1.1 times the theoretical amount of sodium sulfite and add it to the alkaline vanadium-containing solution and stir to dissolve; slowly add industrial sulfuric acid with a mass concentration of 93% to the above solution, and the pH at the end point of the solution is 2.43.

[0048] No precipitation is formed during the whole operation process.

[0049] The above-described embodiments merely represent the specific implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several variations and improvements can still be made, and these all fall within the protection scope of the present application.

[0050] This Background of the Invention section is provided to generally present the context of the present invention. Work of the presently named inventors, to the extent it is described in this Background of the Invention section, and aspects of the work described that were not part of the prior art as of the time of filing this application, are neither expressly nor impliedly admitted to be prior art to the present invention.

Claims

1. Method for reducing alkaline vanadium-containing solution during short-process preparation of vanadium electrolyte, characterized in that It includes the following steps: (1) Add reducing agent sodium sulfite into the alkaline vanadium-containing solution and dissolve it; (2) Add acid into the solution obtained in step (1), adjust the pH to conduct a reduction reaction, and reduce vanadium to tetravalent.

2. The reduction method of the alkaline vanadium-containing solution in the short-process preparation of vanadium electrolyte according to claim 1, characterized in that: In the alkaline vanadium-containing solution described in step (1), the concentration of vanadium is 1-30 g / L; the reducing agent sodium sulfite is added into the alkaline vanadium-containing solution in the original form of industrial powdered solid, and the addition amount of sodium sulfite is 1.05-1.1 times of the theoretical amount.

3. The reduction method of the alkaline vanadium-containing solution in the short-process preparation of vanadium electrolyte according to claim 1, characterized in that: When adding the reducing agent sodium sulfite in step (1), the pH value is not adjusted, and sodium sulfite only dissolves, and no precipitate is formed in the solution after adding sodium sulfite.

4. The reduction method of the alkaline vanadium-containing solution in the short-process preparation of vanadium electrolyte according to claim 1, characterized in that: The acid added in step (2) is sulfuric acid, and its mass concentration is 93% or 98%.

5. The reduction method of the alkaline vanadium-containing solution in the short-process preparation of vanadium electrolyte according to claim 1, characterized in that: After adding acid in step (2), a reduction reaction of vanadium is conducted, and the pH value of the solution at the end point of the reduction reaction is not lower than 2.

0.

6. The reduction method of an alkaline vanadium-containing solution in the short-process preparation of a vanadium electrolyte according to claim 1, characterized in that: After the acidification reduction reaction in step (2), vanadium is reduced to tetravalent, and no precipitate is formed during the reduction process.

7. The reduction method of the alkaline vanadium-containing solution in the short-process preparation of vanadium electrolyte according to claim 2, characterized in that: The addition amount of sodium sulfite is 1.1 times of the theoretical amount.

8. The reduction method of the alkaline vanadium-containing solution in the short-process preparation of vanadium electrolyte according to claim 5, characterized in that: After adding acid in step (2), a reduction reaction of vanadium is conducted, and the pH value of the solution at the end point of the reduction reaction is 2.0-3.

0.

9. The reduction method of the alkaline vanadium-containing solution in the short-process preparation of vanadium electrolyte according to claim 8, characterized in that: After adding acid in step (2), a reduction reaction of vanadium is conducted, and the pH value of the solution at the end point of the reduction reaction is 2.

1.

10. The reduction method of the alkaline vanadium-containing solution in the short-process preparation of vanadium electrolyte according to claim 8, characterized in that: After adding acid in step (2), a reduction reaction of vanadium is conducted, and the pH value of the solution at the end point of the reduction reaction is 2.52.