Rapid determination method for vanadium ion concentration

Abstract

The invention relates to a method for rapidly measuring the concentration of vanadium ions in a vanadium battery electrolyte and application, in particular to a method for rapidly and quantitatively measuring the concentration of vanadium ions in a vanadium battery positive electrode electrolyte or a vanadium battery negative electrode electrolyte and application of the method, and solves the problems that in the prior art, the operation process is tedious, and professional detection equipment is needed. The method comprises the following steps: taking a certain amount of to-be-detected vanadium battery positive or negative electrolyte, and dripping a potassium permanganate solution with known concentration into the to-be-detected solution until the solution is bright blue or blue or light pink or light red; and calculating the concentration of vanadium ions in the electrolyte according to the volume of potassium permanganate consumed at the moment. The method has the advantages of accurate determination result, simple and convenient operation process and no need of any professional detection equipment, can be used for rapid determination of the vanadium ion concentration in the vanadium battery electrolyte, and is suitable for rapid field detection requirements of each system of an all-vanadium battery.

Description

Technical Field

[0001] This invention relates to the field of rapid determination of vanadium ion concentration in vanadium battery electrolytes, and particularly to a rapid quantitative determination method for vanadium ions in a vanadium electrolyte containing pentavalent vanadium or a mixture of tetravalent and pentavalent vanadium at the positive electrode, or a vanadium electrolyte containing divalent vanadium or a mixture of divalent and trivalent vanadium at the negative electrode. Background Technology

[0002] Vanadium redox flow batteries are a novel type of electrochemical energy storage system. Compared to traditional batteries, they offer advantages such as rapid, high-capacity charging and discharging, low self-discharge rate, and simple structure, demonstrating significant advantages in stationary energy storage devices for renewable energy. The positive and negative electrode electrolytes of vanadium batteries are sulfuric acid solutions containing V(V) / V(Ⅳ) and V(Ⅲ) / V(Ⅱ) vanadium compounds, respectively. These solutions are not only conductive media but also electroactive materials for energy storage, forming the core of vanadium battery energy storage and conversion. The interconversion of electrical and chemical energy is achieved through the transformation of vanadium ion valence states. Therefore, the concentration and valence state balance of vanadium ions in the positive and negative electrode electrolytes determine the energy storage capacity of the vanadium redox flow battery. Regular monitoring of the vanadium ion concentration in the electrolyte of the vanadium redox flow battery system is necessary to ensure that the electrolyte remains in optimal condition. Currently, the main methods for detecting vanadium ion concentration include redox titration, ultraviolet-visible spectroscopy, and inductively coupled plasma (ICP) methods. However, these methods all require specialized testing equipment, limiting the detection of electrolytes in vanadium redox flow battery systems. Therefore, developing a rapid method for detecting vanadium ion concentration is particularly important.

[0003] Although the method mentioned in patent CN202111505125.6 does not use professional testing equipment, it only involves the detection method of vanadium electrolyte with trivalent vanadium, or vanadium electrolyte with tetravalent vanadium, or vanadium electrolyte with a mixture of trivalent and tetravalent vanadium. It does not propose a solution for detecting the concentration of vanadium ions in the positive and negative electrolytes of vanadium batteries. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a rapid method for determining the vanadium ion concentration in vanadium battery electrolytes, thereby resolving issues such as cumbersome operation procedures and the need for specialized testing equipment in existing technologies.

[0005] The technical solution of this invention is as follows:

[0006] A rapid method for detecting vanadium ion concentration, wherein the test solution is a vanadium electrolyte containing pentavalent vanadium or a mixture of tetravalent and pentavalent vanadium as the positive electrode, or a vanadium electrolyte containing divalent vanadium or a mixture of divalent and trivalent vanadium as the negative electrode;

[0007] A. When the solution to be tested is a vanadium electrolyte containing pentavalent vanadium or a mixture of tetravalent and pentavalent vanadium, the solution is yellow (RGB range is 255, 255, (200-0) or 255, (255-230), 0) or dark blue (RGB range is 0, 0, (255-100)).

[0008] 1) Take a vanadium electrolyte containing pentavalent vanadium or a mixture of tetravalent and pentavalent vanadium at the positive electrode, and divide it into two test solutions, a and b. Then, add a potassium permanganate solution of known concentration to solution a dropwise until the solution turns light pink or light red (RGB range is 255, (250-240), 250). Calculate the concentration of vanadium ions, c1, based on the volume of potassium permanganate consumed at this point. c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L).

[0009] 2) Add reducing agent solution to solution b until the color of solution b turns bright blue or blue (RGB range: 0, (100-0), 255 or (60-0), 0, 255), then stop adding. Next, add potassium permanganate solution of known concentration to solution b until the solution turns pale pink or pale red (RGB range: 255, (250-240), 250). Calculate the vanadium ion concentration c2 based on the volume of potassium permanganate consumed at this point, c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L). Therefore, the concentration of tetravalent vanadium ions in the test solution is c1, and the concentration of pentavalent vanadium ions is c2 - c1.

[0010] Or B, when the test solution is a negative electrode divalent vanadium, or a vanadium electrolyte of a mixture of divalent and trivalent vanadium, its solution is purple (RGB range of 150, (100-0), 255 or (150-120), 0, 255) or dark green (RGB range of 0, 100, (120-50) or (40-0), 100, 100);

[0011] 1) Take a vanadium electrolyte containing divalent vanadium or a mixture of divalent and trivalent vanadium at the negative electrode, and divide it into two test solutions, a and b. Then, add a potassium permanganate solution of known concentration to solution a dropwise until the solution turns bright blue or blue (RGB range is 0, (100-0), 255 or (60-0), 0, 255). Calculate the concentration of vanadium ions, c1, based on the volume of potassium permanganate consumed at this point. c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L).

[0012] 2) Add a potassium permanganate solution of known concentration to solution b until the solution turns pale pink or pale red (RGB range: 255, (250-240), 250). Calculate the vanadium ion concentration c2 based on the volume of potassium permanganate consumed at this point. c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L). Therefore, the concentration of divalent vanadium ions in the test solution is 2c1-c2, and the concentration of trivalent vanadium ions is 2c2-3c1.

[0013] The reducing agent includes one or more of the following: ferrous ammonium sulfate at a mass concentration of 1%-50% (preferably 2-30%, more preferably 5-20%), citric acid at a mass concentration of 1%-50% (preferably 2-30%, more preferably 5-20%), oxalic acid at a mass concentration of 1%-50% (preferably 2-30%, more preferably 5-20%), and hydrazine hydrate at a mass concentration of 1%-50% (preferably 2-30%, more preferably 5-20%).

[0014] The concentration of potassium permanganate is 0.01-5 mol / L, preferably 0.01-1 mol / L, and more preferably 0.02-0.5 mol / L.

[0015] The concentration of vanadium ions in the test solution is 0-4 mol / L, preferably 0.1-4 mol / L, and more preferably 0.2-3 mol / L.

[0016] The electrolyte is a vanadium redox flow battery electrolyte. This method can be used for rapid detection of vanadium ion concentration in vanadium redox flow battery electrolytes under any environment, especially for rapid on-site detection of vanadium redox flow battery systems.

[0017] Beneficial effects of the invention

[0018] The technical solution provided by this invention enables rapid detection of vanadium ions in the electrolyte of vanadium redox flow batteries, requiring no specialized equipment and offering simple and convenient operation. It can meet the rapid on-site testing needs of vanadium redox flow battery systems. Detailed Implementation

[0019] Example 1

[0020] The positive electrode electrolyte from the vanadium redox flow battery was used as the test sample, which was dark blue.

[0021] First, take 5.000 mL of the sample to be tested and add a 0.100 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns a light pink or light red color. The volume of potassium permanganate consumed at this point is 8.7 mL. According to the formula c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L), c1 is calculated to be 0.87 mol / L.

[0022] Next, take 5.00 mL of the sample to be tested and add 10% ferrous ammonium sulfate solution dropwise until the electrolyte turns bright blue. Then stop adding. Next, add 0.100 mol / L potassium permanganate standard solution dropwise until the electrolyte turns pale pink or pale red. The volume of potassium permanganate consumed at this point is 16.3 mL. According to the formula c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L), c2 is calculated to be 1.63 mol / L. Therefore, the concentration of tetravalent vanadium ions in the sample is c1 = 0.87 mol / L, and the concentration of pentavalent vanadium ions is c2 - c1 = 1.63 mol / L - 0.87 mol / L = 0.76 mol / L.

[0023] The same sample was taken and measured using conventional potentiometric titration (the testing instrument used was an automatic potentiometric titrator). The concentration of tetravalent vanadium ions was 0.8669 mol / L and the concentration of pentavalent vanadium ions was 0.7624 mol / L.

[0024] The data obtained by this invention have errors of 0.36% and 0.31% compared to those obtained by conventional methods.

[0025] Example 2

[0026] The positive electrode electrolyte of a fully charged vanadium redox flow battery was used as the test sample, which was bright yellow.

[0027] First, take 5.000 mL of the sample to be tested and add a 0.100 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns a light pink or light red color. The volume of potassium permanganate consumed at this point is 0.1 mL. According to the formula c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L), c1 is calculated to be 0.01 mol / L.

[0028] Next, take 5.00 mL of the sample to be tested and add 10% ferrous ammonium sulfate solution dropwise until the electrolyte turns bright blue. Then stop adding. Next, add 0.100 mol / L potassium permanganate standard solution dropwise until the electrolyte turns pale pink or pale red. The volume of potassium permanganate consumed at this point is 16.5 mL. According to the formula c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L), c2 is calculated to be 1.65 mol / L. Therefore, the concentration of tetravalent vanadium ions in the sample is c1 = 0.01 mol / L, and the concentration of pentavalent vanadium ions is c2 - c1 = 1.65 mol / L - 0.01 mol / L = 1.64 mol / L.

[0029] The same sample was taken and measured using conventional potentiometric titration (the testing instrument used was an automatic potentiometric titrator). The concentration of tetravalent vanadium ions was 0.0112 mol / L and the concentration of pentavalent vanadium ions was 1.6348 mol / L.

[0030] The data obtained by this invention have errors of 10.7% and 0.32% compared to those obtained by conventional methods. The low concentration of tetravalent vanadium leads to a larger calculation error.

[0031] Example 3

[0032] The negative electrode electrolyte from the vanadium redox flow battery was used as the sample to be tested; the sample was dark green.

[0033] First, take 5.000 mL of the sample to be tested and add a 0.100 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns bright blue or blue. The volume of potassium permanganate consumed at this point is 22.8 mL. According to the formula c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L), c1 is calculated to be 2.28 mol / L.

[0034] Next, take 5.00 mL of the sample to be tested and add 0.100 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns a light pink or light red color. The volume of potassium permanganate consumed at this point is 38.9 mL. According to the formula c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L), c2 is calculated to be 3.89 mol / L. Therefore, the concentration of divalent vanadium ions in the sample is 2c1 - c2 = 2 * 2.28 mol / L - 3.89 mol / L = 0.67 mol / L, and the concentration of trivalent vanadium ions is 2c2 - 3c1 = 2 * 3.89 mol / L - 3 * 2.28 mol / L = 0.94 mol / L.

[0035] The same sample was taken and measured using conventional potentiometric titration (the testing instrument used was an automatic potentiometric titrator). The concentration of divalent vanadium ions was 0.6741 mol / L and the concentration of trivalent vanadium ions was 0.9374 mol / L.

[0036] The data obtained by this invention have errors of 0.61% and 0.28% compared to those obtained by conventional methods.

[0037] Example 4

[0038] The negative electrode electrolyte from the vanadium redox flow battery was taken as the sample to be tested; the sample was purple.

[0039] First, take 5.000 mL of the sample to be tested and add a 0.100 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns bright blue or blue. The volume of potassium permanganate consumed is 32.6 mL. According to the formula c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L), c1 is calculated to be 3.26 mol / L.

[0040] Next, take 5.00 mL of the sample to be tested and add 0.100 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns a light pink or light red color. The volume of potassium permanganate consumed at this point is 49.0 mL. According to the formula c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L), c2 is calculated to be 4.90 mol / L. Therefore, the concentration of divalent vanadium ions in the sample is 2c1 - c2 = 2 * 3.26 mol / L - 4.90 mol / L = 1.62 mol / L, and the concentration of trivalent vanadium ions is 2c2 - 3c1 = 2 * 4.90 mol / L - 3 * 3.26 mol / L = 0.02 mol / L.

[0041] The same sample was taken and measured using conventional potentiometric titration (the testing instrument used was an automatic potentiometric titrator). The concentration of divalent vanadium ions was 1.6151 mol / L and the concentration of trivalent vanadium ions was 0.0210 mol / L.

[0042] The data obtained by this invention have errors of 0.30% and 4.76% compared with those obtained by conventional methods. Due to the low concentration of trivalent vanadium, the calculation error is larger than expected.

[0043] Example 5

[0044] The positive electrode electrolyte from the vanadium redox flow battery was used as the test sample, which was dark blue.

[0045] First, take 5.000 mL of the sample to be tested and add a 1.000 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns a light pink or light red color. The volume of potassium permanganate consumed at this point is 0.9 mL. According to the formula c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L), c1 is calculated to be 0.90 mol / L.

[0046] Next, take 5.00 mL of the sample to be tested and add 10% ferrous ammonium sulfate solution dropwise until the electrolyte turns bright blue. Then stop adding. Next, add 1.000 mol / L potassium permanganate standard solution dropwise until the electrolyte turns pale pink or pale red. The volume of potassium permanganate consumed at this point is 1.6 mL. According to the formula c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L), c2 is calculated to be 1.60 mol / L. Therefore, the concentration of tetravalent vanadium ions in the sample is c1 = 0.90 mol / L, and the concentration of pentavalent vanadium ions is c2 - c1 = 1.60 mol / L - 0.90 mol / L = 0.70 mol / L.

[0047] The same sample was taken and measured using conventional potentiometric titration (the testing instrument used was an automatic potentiometric titrator). The concentration of tetravalent vanadium ions was 0.9203 mol / L and the concentration of pentavalent vanadium ions was 0.7136 mol / L.

[0048] The data obtained by this invention have errors of 2.21% and 1.91% compared to those obtained by conventional methods.

[0049] Example 6

[0050] The positive electrode electrolyte from the vanadium redox flow battery was used as the test sample, which was dark blue.

[0051] First, take 5.000 mL of the sample to be tested and add a 5.000 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns a light pink or light red color. The volume of potassium permanganate consumed at this point is 0.2 mL. According to the formula c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L), c1 is calculated to be 1.00 mol / L.

[0052] Next, take 5.00 mL of the sample to be tested and add 10% ferrous ammonium sulfate solution dropwise until the electrolyte turns bright blue. Then stop adding. Next, add 5.000 mol / L potassium permanganate standard solution dropwise until the electrolyte turns light pink or light red. The volume of potassium permanganate consumed at this point is 1.6 mL. According to the formula c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L), c2 is calculated to be 1.60 mol / L. Therefore, the concentration of tetravalent vanadium ions in the sample is c1 = 1.00 mol / L, and the concentration of pentavalent vanadium ions is c2 - c1 = 1.60 mol / L - 1.00 mol / L = 0.60 mol / L.

[0053] The same sample was taken and measured using conventional potentiometric titration (the testing instrument used was an automatic potentiometric titrator). The concentration of tetravalent vanadium ions was 0.9127 mol / L and the concentration of pentavalent vanadium ions was 0.5343 mol / L.

[0054] The data obtained by this invention have errors of 9.57% and 12.30% compared with those obtained by conventional methods.

[0055] As can be seen from Examples 5 and 6, when the potassium permanganate concentration is too high (5 mol / L), the technology provided by the present invention can detect the vanadium ion concentration, but the error with the data obtained by conventional methods will increase, reducing the accuracy of the data.

[0056] Example 7

[0057] The positive electrode electrolyte from the vanadium redox flow battery was used as the test sample, which was dark blue.

[0058] First, take 5.000 mL of the sample to be tested and add a 0.100 mol / L potassium permanganate standard solution dropwise. Stop adding the solution when the electrolyte turns a light pink or light red color. The volume of potassium permanganate consumed at this point is 7.5 mL. According to the formula c1 = 5cV1 / V, where c is the concentration of potassium permanganate (mol / L), V1 is the volume of potassium permanganate consumed (L), and V is the volume of solution a (L), c1 is calculated to be 0.75 mol / L.

[0059] Next, take 5.00 mL of the sample to be tested and add 10% citric acid solution dropwise until the electrolyte turns bright blue. Then stop adding. Next, add 0.100 mol / L potassium permanganate standard solution dropwise until the electrolyte turns pale pink or pale red. The volume of potassium permanganate consumed at this point is 15.8 mL. According to the formula c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L), c2 is calculated to be 1.58 mol / L. Therefore, the concentration of tetravalent vanadium ions in the sample is c1 = 0.75 mol / L, and the concentration of pentavalent vanadium ions is c2 - c1 = 1.58 mol / L - 0.75 mol / L = 0.83 mol / L.

[0060] The same sample was taken and measured using conventional potentiometric titration (the testing instrument used was an automatic potentiometric titrator). The concentration of tetravalent vanadium ions was 0.7534 mol / L and the concentration of pentavalent vanadium ions was 0.8328 mol / L.

[0061] The data obtained by this invention have errors of 0.45% and 0.34% compared with those obtained by conventional methods.

Claims

1. A rapid method for detecting vanadium ion concentration, characterized in that: The solution to be tested is a vanadium electrolyte with pentavalent vanadium or a mixture of tetravalent and pentavalent vanadium as the positive electrode, or a vanadium electrolyte with divalent vanadium or a mixture of divalent and trivalent vanadium as the negative electrode; A. When the solution to be tested is a vanadium electrolyte containing pentavalent vanadium at the positive electrode, or a mixture of tetravalent and pentavalent vanadium, the solution is yellow or dark blue. 1) Take a vanadium electrolyte containing pentavalent vanadium, or a mixture of tetravalent and pentavalent vanadium, and divide it into two test solutions, a and b; then add potassium permanganate solution of known concentration to solution a dropwise until the solution turns light pink or light red. Based on the volume of potassium permanganate consumed at this time, the concentration of vanadium ions c1 is calculated, c1 = 5cV1 / V, where c is the concentration of potassium permanganate in mol / L, V1 is the volume of potassium permanganate consumed in L, and V is the volume of solution a in L. 2) Add reducing agent solution to solution b until the color of solution b turns bright blue or blue, then stop adding. Next, add potassium permanganate solution of known concentration to solution b until the solution turns pale pink or pale red. Calculate the concentration of vanadium ions c2 based on the volume of potassium permanganate consumed at this point, where c2 = 5cV2 / V, where c is the concentration of potassium permanganate (mol / L), V2 is the volume of potassium permanganate consumed (L), and V is the volume of solution b (L). Therefore, the concentration of tetravalent vanadium ions in the test solution is c1, and the concentration of pentavalent vanadium ions is c2 - c1. Or B, when the test solution is a vanadium electrolyte containing divalent vanadium as the negative electrode, or a mixture of divalent and trivalent vanadium, the solution will be purple or dark green; 1) Take a vanadium electrolyte containing divalent vanadium or a mixture of divalent and trivalent vanadium at the negative electrode, and divide it into two portions, a and b, to be tested; then add potassium permanganate solution of known concentration to solution a dropwise until the solution turns bright blue or blue. Based on the volume of potassium permanganate consumed at this time, the concentration of vanadium ions c1 is calculated, c1 = 5cV1 / V, where c is the concentration of potassium permanganate in mol / L, V1 is the volume of potassium permanganate consumed in L, and V is the volume of solution a in L. 2) Add potassium permanganate solution of known concentration to solution b dropwise until the solution turns light pink or light red. Based on the volume of potassium permanganate consumed at this time, the concentration of vanadium ions, c2, is calculated as c2 = 5cV2 / V, where c is the concentration of potassium permanganate in mol / L, V2 is the volume of potassium permanganate consumed in L, and V is the volume of solution b in L. Therefore, the concentration of divalent vanadium ions in the test solution is 2c1-c2, and the concentration of trivalent vanadium ions is 2c2-3c1.

2. The determination method according to claim 1, characterized in that, The reducing agent includes one or more of the following: ferrous ammonium sulfate at a mass concentration of 1%-50% (preferably 2-30%, more preferably 5-20%), citric acid at a mass concentration of 1%-50% (preferably 2-30%, more preferably 5-20%), oxalic acid at a mass concentration of 1%-50% (preferably 2-30%, more preferably 5-20%), and hydrazine hydrate at a mass concentration of 1%-50% (preferably 2-30%, more preferably 5-20%).

3. The determination method according to claim 1, characterized in that, The concentration of potassium permanganate is 0.01-5 mol / L, preferably 0.01-1 mol / L, and more preferably 0.02-0.5 mol / L.

4. The determination method according to claim 1, characterized in that, The electrolyte is a vanadium redox flow battery electrolyte. This method can be used for rapid detection of vanadium ion concentration in vanadium redox flow battery electrolytes under any environment, especially for rapid on-site detection of vanadium redox flow battery systems.

5. The determination method according to claim 1, characterized in that, The concentration of vanadium ions in the test solution is 0-4 mol / L, preferably 0.1-3 mol / L, and more preferably 0.2-3 mol / L.