Method for determining concentration of impurity elements in vanadium electrolyte

Abstract

The application provides a method for testing the concentration of impurity elements in vanadium electrolyte for a vanadium redox flow battery, comprising a reduction method and an oxidation method. The method can be used to determine all metal elements of main groups and side groups contained in the vanadium electrolyte, which can be detected by an inductively coupled plasma mass spectrometer, and one or more than two of Be, Si, B, P, S, As, Se, Br, Te and I elements. The test method of the application can greatly reduce the total salt concentration of the vanadium electrolyte, which is lower than 0.2%wt, meet the sample injection requirements of the inductively coupled plasma mass spectrometer, reduce the dilution multiple of the sample injection solution, and improve the detection accuracy of the impurity elements.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of all-vanadium redox flow battery, in particular to a method for testing the concentration of impurity elements in electrolyte of all-vanadium redox flow battery. BACKGROUND

[0002] All-vanadium redox flow battery has been widely concerned in the field of energy storage due to its high safety, environmental friendliness, independent design of battery power and capacity, and high cost performance in life cycle, and has great application prospects in grid peak shaving, renewable energy generation, household power supply, emergency power supply and the like.

[0003] The electrolyte as an energy storage unit is one of the main components of the all-vanadium redox flow battery. The purity of the electrolyte has a great influence on the long-term stable operation and the charging and discharging efficiency of the electrolyte. For example, some impurities can increase the temperature sensitivity of the electrolyte, cause precipitation in the operation process of the electrolyte, adhere to the membrane, or enter the pipeline to cause blockage of the stack pipeline. Therefore, it is of great significance to monitor the types and concentrations of impurities in the electrolyte.

[0004] At present, the method for testing impurities in the electrolyte includes spectrophotometry for testing the concentrations of silicon, iron and nitrogen. This method has limited types of tested impurity elements and high detection limit, and cannot test the concentrations of trace (<0.01%) and ultra-trace (about 0.0001%) impurity elements in the electrolyte, and cannot simultaneously test the concentrations of multiple elements.

[0005] The inductively coupled plasma spectrometry and inductively coupled plasma mass spectrometry can be used to test the concentrations of trace and ultra-trace impurity elements such as Cr, Fe, Mo, Ni, Co, Cu, Mn, Ti, Zn, Si, Al, As, P, Ca, Mg, Pb, Pt, Au, Ag, Ir, Os, Pd, Re, Rh, Ru and Sb in the electrolyte. The semi-quantitative method is used to determine the element composition in the vanadium electrolyte, and then the qualitative method is used to determine the concentrations of impurity elements in the electrolyte.

[0006] Because the concentrations of vanadium ions, sulfate ions and hydrogen ions in the vanadium electrolyte are high, that is, the total salt concentration in the electrolyte is too high, the instrument detector will be damaged if the electrolyte is directly introduced into the instrument for testing. Therefore, the current method is to dilute the vanadium electrolyte by a certain multiple, so that the total salt concentration is lower than the allowable range of the instrument, and then the electrolyte is introduced into the instrument for testing. This results in lower concentrations of trace and ultra-trace elements, and lower testing accuracy of some elements. SUMMARY

[0007] The present application provides a method for testing the concentration of impurity elements in vanadium electrolyte for all-vanadium redox flow battery, which effectively reduces the total salt concentration of the vanadium electrolyte, reduces the dilution multiple of the vanadium electrolyte, and improves the testing accuracy of impurity elements.

[0008] Vanadium element has four valence states V 2+ , V 3+ , V 4+ , V 5+ , and at most two adjacent valence states exist in the same solution, and the pretreatment methods are different for different valence state combinations.

[0009] The application provides a test method for a vanadium electrolyte containing four valence states existing separately and adjacent valence states mixed.

[0010] The application provides a test method for the concentration of impurity elements in a vanadium electrolyte, including a reduction method and an oxidation method.

[0011] The vanadium electrolyte to be determined contains vanadium ions (V 2+ , V 3+ , V 4+ , V 5+ or a mixed solution of adjacent valence states, total vanadium concentration 1-3 mol / L), sulfate ions (1-8 mol / L), hydrogen ions (1-8 mol / L).

[0012] Reduction method:

[0013] A, draw a standard curve: take the standard substance of the impurity element to be determined, and prepare at least 5 different concentration points of the standard solution of each impurity element to be determined by using water, and each impurity element to be determined in the standard solution is in the concentration range of 0.001-100 μg / L; take water as a blank solution; introduce the blank solution and the standard solution into an inductively coupled plasma mass spectrometer for testing, and take the concentration and signal intensity value (deducting the blank) as the horizontal and vertical coordinates respectively, and draw a standard curve of each impurity element to be determined;

[0014] The method of the application can be used to determine all main group and side group metal elements contained in the vanadium electrolyte, which can be detected by an inductively coupled plasma mass spectrometer, and one or more than two of Be, Si, B, P, S, As, Se, Br, Te and I elements, in the concentration range of 0.001-100 μg / L.

[0015] B, the process is the following step (I) or (II):

[0016] (I) the determination process of the vanadium electrolyte containing one or two of V 2+ , V 3+ (and not containing V 4+ );

[0017] 1) calculate the sulfate content in the electrolyte:

[0018] Take the original vanadium electrolyte to add excess barium chloride solution (0.5-1.5 mol / L), so that the sulfate ion in the electrolyte is completely reacted to form barium sulfate precipitate, after centrifugation, take the precipitate, water washing, centrifugal washing, at least 3 times or more, dry the washed precipitate, burn the precipitate to constant weight, weigh the mass of barium sulfate, and calculate the sulfate content according to the mass of barium sulfate;

[0019] To ensure that the sulfate precipitate is completely, the amount of barium chloride added is calculated as 101%-200% of the amount of barium chloride consumed by all precipitates at the upper limit of the sulfate concentration in claim 2.

[0020] 2) Take the original vanadium electrolyte to add precipitant, stir well, so that the sulfate and vanadium ions form precipitate and precipitate, while consuming a large amount of hydrogen ions in the solution, reducing the concentration of hydrogen ions; the amount of precipitant is the amount of substance required for complete precipitation of sulfate in the vanadium electrolyte; after complete precipitation, centrifuge and collect the supernatant;

[0021] Precipitant: one or both of barium hydroxide and calcium hydroxide;

[0022] 3) Wash the precipitate with water and centrifuge to obtain the supernatant; repeat the washing of the precipitate and centrifuge for 3 times or more, and collect all the supernatant;

[0023] 4) Transfer the supernatant obtained in steps 2) and 3) into a volumetric flask, add water to constant volume; dilute to 2-10 times the volume of the original electrolyte taken in step 2);

[0024] 5) Prepare a sample blank solution: prepare a precipitant aqueous solution of the required concentration according to the ratio of the mass of precipitant required in step 2) to the volume of constant volume in step 4), as the sample blank solution;

[0025] The sample blank solution prepared in step 5) and the solution diluted in step 4) are introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values of the impurity elements; substitute into the standard curve to obtain the concentration of the impurity elements to be tested in the sample blank solution and the concentration of the impurity elements to be tested in the detection sample solution;

[0026] Subtract the concentration of the corresponding impurity elements to be tested in the sample blank solution from the concentration of the corresponding impurity elements to be tested in the detection sample solution, and multiply by the dilution factor in step 4) to obtain the concentration of the impurity elements in the original vanadium electrolyte in step 2);

[0027] Or, (ii) vanadium electrolyte containing one or both of V 4+ , V 5+ or one or both of V

[0028] 1) Calculate the sulfate content in the electrolyte:

[0029] Take the original vanadium electrolyte to add excess barium chloride solution (0.5-1.5 mol / L), so that the sulfate ion in the electrolyte is completely reacted to form barium sulfate precipitate, and the precipitate is taken after centrifugation, washed with water, and then centrifuged and washed at least 3 times or more. Dry the washed precipitate, calcine the precipitate to constant weight, weigh the mass of barium sulfate, and calculate the sulfate content according to the mass of barium sulfate;

[0030] To ensure that the sulfate precipitate is completely precipitated, the amount of barium chloride added is calculated as 101%-200% of the amount of barium chloride consumed when the sulfate concentration in the vanadium electrolyte to be determined is at the upper limit.

[0031] 2) Take the original vanadium electrolyte, and test the concentrations of V 4+ , V 5+ in the electrolyte according to the standard "NB / T 42006-2013 Test Method for Electrolyte for All-vanadium Redox Flow Battery".

[0032] 3) Take the same original electrolyte as in step 1) above, and add a reducing agent, hydrazine hydrate, or use an electrochemical reduction method to reduce V 4+ , V 5+ in the electrolyte to V 2+ and / or V 3+ , i.e. to make the electrolyte not contain V 4+ ; this is used as the initial electrolyte.

[0033] The amount of hydrazine hydrate used is the minimum amount required to completely reduce V 4+ and V 5+ to V 3+ , and the amount of substance required to completely reduce V 4+ and V 5+ to V 2+ is the maximum amount of addition;

[0034] 4) Add a precipitating agent to the initial vanadium electrolyte obtained in step 3), and stir well to make sulfate and vanadium ions form precipitates and precipitate; the amount of precipitating agent used is the amount of substance required for complete precipitation of sulfate in the vanadium electrolyte; after complete precipitation, centrifuge and collect the supernatant;

[0035] Precipitating agent: one or both of barium hydroxide and calcium hydroxide;

[0036] 5) Wash the precipitate with water and centrifuge to obtain the supernatant; repeat the washing and centrifugation of the precipitate 3 times or more, and collect all the supernatants;

[0037] 6) Transfer the supernatants obtained in steps 4) and 5) into a volumetric flask, and add water to constant volume; dilute to 2-10 times the volume of the original electrolyte taken in step 3);

[0038] 7) Prepare sample blank solution and test:

[0039] Prepare the precipitant aqueous solution of the required concentration according to the ratio of the required precipitant mass in step 4) to the volume of the constant volume in step 6), as sample blank solution 1;

[0040] If the electrochemical reduction method is used in step 3), the sample blank solution 1 and the solution diluted in step 6) are introduced into the inductively coupled plasma mass spectrometer respectively to test the signal intensity values of the impurity elements; the concentrations of the impurity elements in the sample blank solution 1 and the detection sample solution are obtained by substituting into the standard curve;

[0041] The concentration of the impurity elements in the original vanadium electrolyte in step 3) is obtained by subtracting the corresponding impurity element concentration in the sample blank solution 1 from the corresponding impurity element concentration in the detection sample solution and multiplying by the dilution factor in step 6);

[0042] If the reducing agent hydrazine is added to the initial electrolyte in step 3), prepare the hydrazine aqueous solution of the required concentration according to the ratio of the required hydrazine mass in step 3) to the volume of the constant volume in step 6), as sample blank solution 2;

[0043] The sample blank solution 1, the sample blank solution 2 and the solution diluted in step 6) are introduced into the inductively coupled plasma mass spectrometer respectively to test the signal intensity values of the impurity elements; the concentrations of the impurity elements in the sample blank solution 1, the sample blank solution 2 and the detection sample solution are obtained by substituting into the standard curve;

[0044] The concentration of the impurity elements in the original vanadium electrolyte in step 3) is obtained by subtracting the corresponding impurity element concentration in the sample blank solution 1 and the sample blank solution 2 from the corresponding impurity element concentration in the detection sample solution and multiplying by the dilution factor in step 6).

[0045] The oxidation method includes:

[0046] A. Draw the standard curve: take the standard substance of the impurity element to be tested, prepare standard solutions of at least 5 different concentration points of each impurity element to be tested with water, and each impurity element to be tested in the standard solution is in the concentration range of 0.001-100 μg / L; take water as the blank solution; introduce the blank solution and the standard solution into the inductively coupled plasma mass spectrometer respectively to test, and draw the standard curve of each impurity element to be tested respectively with the concentration and the signal intensity value (blank) as the horizontal and vertical coordinates;

[0047] The method of the present invention can be used to determine all main group and subgroup metallic elements contained in vanadium electrolytes, with a concentration range of 0.001 to 100 μg / L detectable by inductively coupled plasma mass spectrometry, and one or more of the elements Be, Si, B, P, S, As, Se, Br, Te, and I.

[0048] B. The process consists of the following steps (I) or (II):

[0049] (I) V 5+ Vanadium electrolyte (V only in V 5+ It exists, and it does not contain V. 4+ The measurement process of );

[0050] 1) Calculate the sulfate content in the electrolyte: Take the original electrolyte and add excess barium chloride solution (0.5-1.5 mol / L) to make the sulfate ions in the electrolyte react completely and form barium sulfate precipitate. After centrifugation, take the precipitate, wash it with water, and then centrifuge and wash it again, at least 3 times. Dry the washed precipitate, ignite the precipitate to constant weight, weigh the barium sulfate, and calculate the sulfate content based on the mass of barium sulfate.

[0051] To ensure complete sulfate precipitation, the amount of barium chloride added should be calculated as 101%-200% of the amount of barium chloride required for complete precipitation when the sulfate concentration in the vanadium electrolyte composition to be tested reaches its upper limit.

[0052] 2) Take the original electrolyte and heat it to 60-100℃, keep it at the temperature for more than 1 hour, and after precipitation is complete, centrifuge and keep the supernatant; wash the precipitate with water and centrifuge to collect the supernatant; repeat washing the precipitate and centrifuging more than 3 times, collect the supernatant, and mix all the supernatants to obtain a mixture.

[0053] 3) Add a precipitant to the mixture and stir thoroughly to allow sulfate ions to precipitate and precipitate out. At the same time, this will consume a large amount of hydrogen ions in the solution, thus reducing the hydrogen ion concentration. The amount of precipitant used is the amount of substance required for complete precipitation of sulfate ions in the vanadium electrolyte. After complete precipitation, centrifuge and collect the supernatant.

[0054] Precipitating agent: one or both of barium hydroxide and calcium hydroxide;

[0055] 4) Wash the precipitate with water and centrifuge to collect the supernatant; repeat the washing and centrifugation process for more than 3 times, and collect all the supernatant.

[0056] 5) Transfer the supernatant obtained in steps 3) and 4) into a volumetric flask, add water to make up to the final volume; dilute to 2-10 times the volume of the original electrolyte taken in step 2);

[0057] 6) Preparation of sample blank solution: according to the ratio of the required precipitant mass in step 3) to the volume of the constant volume in step 4), the required concentration of the precipitant aqueous solution is prepared as the sample blank solution;

[0058] The sample blank solution and the solution diluted in step 5) are introduced into the inductively coupled plasma mass spectrometer respectively to test the impurity element signal intensity value; the standard curve is substituted to obtain the concentration of the impurity element to be measured in the sample blank solution and the concentration of the impurity element to be measured in the detection sample solution;

[0059] The concentration of the impurity element in the original vanadium electrolyte in step 2) is obtained by subtracting the corresponding impurity element concentration in the sample blank solution from the corresponding impurity element concentration in the detection sample solution and then multiplying by the dilution multiple in step 5);

[0060] Or, (ii) vanadium electrolyte containing one or two of V 2+ , V 3+ , V 4+ ;

[0061] 1) Calculation of sulfate content in electrolyte: take the original electrolyte and add excess barium chloride solution (0.5-1.5 mol / L) to make the sulfate ions in the electrolyte react completely to generate barium sulfate precipitate; after centrifugation, take the precipitate, wash with water, and then centrifuge and wash again, at least 3 times or more; dry the washed precipitate, calcine the precipitate to constant weight, weigh the mass of barium sulfate, and calculate the sulfate content according to the mass of barium sulfate;

[0062] To ensure complete precipitation of sulfate, the amount of barium chloride added is calculated as 101%-200% of the amount of barium chloride consumed for complete precipitation at the upper limit of the sulfate concentration in claim 5.

[0063] 2) Take the original vanadium electrolyte and test the concentration of V 2+ , V 3+ , V 4+ in the electrolyte according to the standard "NB / T 42006-2013 Test Method for Electrolyte for All-Vanadium Redox Flow Battery";

[0064] 3) Take the same original electrolyte as in step 1) and add an oxidizing agent H2O2 or use an electrochemical oxidation method to make V 2+ , V 3+ , V 4+ in the electrolyte be completely oxidized to V 5+ , i.e., to make the electrolyte not contain V 4+ ; this is used as the initial electrolyte;

[0065] The amount of H2O2 is used to completely oxidize V 2+ , V 3+ , V 4+ in the electrolyte to V5+ 100% - 110% of the amount of substance required;

[0066] 4) The initial vanadium electrolyte obtained in step 3) is heated to 60-100°C and kept at this temperature for more than 1 hour until the precipitation is complete, then centrifuged to retain the supernatant; the precipitate is washed with water and centrifuged to obtain the supernatant; the precipitate is repeatedly washed and centrifuged for more than 3 times, and the supernatants are collected; and all the supernatants are mixed to obtain a mixed solution;

[0067] 5) The precipitate is washed with water and centrifuged to obtain the supernatant; the precipitate is repeatedly washed and centrifuged for more than 3 times, and all the supernatants are collected;

[0068] 6) The supernatants obtained in steps 2) and 3) are transferred into a volumetric flask, and water is added to make up the volume; and the volume is diluted to 2-10 times the volume of the original electrolyte taken in step 2);

[0069] 7) The supernatants obtained in steps 5) and 6) are transferred into a volumetric flask, and water is added to make up the volume; and the volume is diluted to 2-10 times the volume of the original electrolyte taken in step 3);

[0070] 8) Preparation of sample blank solution:

[0071] The sample blank solution 1 is prepared according to the ratio of the mass of the precipitant required in step 5) to the volume made up in step 7);

[0072] If the electrochemical oxidation method is used in step 2), the sample blank solution 1 and the solution diluted in step 7) are introduced into an inductively coupled plasma mass spectrometer respectively to test the signal intensity values of the impurity elements; and the concentrations of the impurity elements in the sample blank solution 1 and the detection sample solution are obtained by substituting into the standard curve;

[0073] The concentration of the impurity elements in the original vanadium electrolyte in step 3) is obtained by subtracting the concentration of the corresponding impurity elements in the sample blank solution 1 from the concentration of the corresponding impurity elements in the detection sample solution, and then multiplying by the dilution factor in step 7);

[0074] Or, if the oxidant H2O2 is added to the original electrolyte in step 3), the sample blank solution 2 is prepared according to the ratio of the amount of the oxidant H2O2 required in step 3) to the volume made up in step 7);

[0075] The sample blank solution 1, the sample blank solution 2 and the solution diluted in step 7) are introduced into an inductively coupled plasma mass spectrometer respectively to test the signal intensity values of the impurity elements; and the concentrations of the impurity elements in the sample blank solution 1, the sample blank solution 2 and the detection sample solution are obtained by substituting into the standard curve;

[0076] Subtract the concentration of the corresponding impurity element to be detected in the sample blank solution 1 and the sample blank solution 2 from the concentration of the corresponding impurity element to be detected in the detection sample solution, and multiply the dilution factor in step 7) to obtain the concentration of the impurity element in the original vanadium electrolyte in step 3).

[0077] The technical scheme of the present application has the following beneficial effects:

[0078] The method of the present application greatly reduces the total salt concentration of the vanadium electrolyte, which is lower than 0.2%wt, meets the sample injection requirements of the inductively coupled plasma mass spectrometer, reduces the dilution factor of the sample injection solution, and improves the detection accuracy of impurity elements.

[0079] The precipitant barium hydroxide and calcium hydroxide, the oxidizing agent H2O2, and the reducing agent hydrazine hydrate used in the present application do not introduce a large amount of solute, i.e., do not increase the total salt concentration of the original solution.

[0080] The electrochemical oxidation and electrochemical reduction method used in the present application does not introduce a large amount of solute, i.e., does not increase the total salt concentration of the original solution. DETAILED DESCRIPTION

[0081] Example 1 (reduction method)

[0082] No. 1 vanadium electrolyte: vanadium electrolyte containing V 2+ , V 3+ ;

[0083] A. Draw a standard curve: take standard material (PE company, N9300233) containing impurity elements to be detected (Ag, In, Al, K, As, Li, Mg, Cu), and prepare a standard solution containing the above-mentioned impurity elements to be detected by using water. The concentration of each impurity element to be detected in the standard solution is equal, and is 1 μg / L, 5 μg / L, 10 μg / L, 15 μg / L, and 20 μg / L. Take water as a blank solution. Introduce the blank solution and the standard solution into an inductively coupled plasma mass spectrometer for testing. Take the concentration and the signal intensity value (blank) as the horizontal and vertical coordinates, respectively, and draw a standard curve of each impurity element to be detected.

[0084] 1) Calculate the content of sulfate ions in the electrolyte:

[0085] Take 1 mL of No. 1 vanadium electrolyte and add 10 mL of 1.5 mol / L barium chloride solution to make the sulfate ions in the electrolyte react completely to form barium sulfate precipitate. After centrifugation, take the precipitate, wash with water, and centrifuge and wash for 3 times. Dry the washed precipitate, and burn the precipitate to constant weight. The mass of the barium sulfate is 1.0524 g. According to the mass of the barium sulfate, the content of sulfate ions is calculated to be 4.509 mol / L.

[0086] 2) Take the original vanadium electrolyte 50 mL, add barium hydroxide 38.552 g, stir well, so that the sulfate and vanadium ions form a precipitate and precipitate, while consuming a large amount of hydrogen ions in the solution, reducing the hydrogen ion concentration; after the precipitate is completely precipitated, centrifuge and collect the supernatant;

[0087] 3) The precipitate is washed with water and centrifuged to obtain the supernatant; the precipitate is repeatedly washed and centrifuged for more than 3 times, and all the supernatants are collected;

[0088] 4) The supernatants obtained in steps 2) and 3) are transferred into a volumetric flask, and water is added to constant volume; dilute to 5 times the volume of the original electrolyte taken in step 2);

[0089] 5) Prepare a sample blank solution: prepare a precipitant aqueous solution of the required concentration according to the ratio of the mass of the precipitant required in step 2) to the volume of the constant volume in step 4), as the sample blank solution;

[0090] The sample blank solution prepared in step 5) and the solution diluted in step 4) are introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values of the impurity elements; the standard curve is obtained by substituting the standard curve, and the concentration of the impurity elements to be tested in the sample blank solution and the concentration of the impurity elements to be tested in the test sample solution are obtained; the concentration of the corresponding impurity elements to be tested in the test sample solution is subtracted from the concentration of the corresponding impurity elements to be tested in the sample blank solution, as shown in Table 1, column 2; multiply by the dilution multiple in step 4) to obtain the concentration of the impurity elements in the No. 1 original vanadium electrolyte, as shown in Table 1, column 3;

[0091] Table 1 Test results of impurity concentration of No. 1 electrolyte

[0092] Element Measured impurity concentration (pg / L) Original solution impurity concentration (pg / L) Ag 1.963 9.82 In 1.539 7.70 Al 1.935 9.68 K 2.674 13.37 As 4.900 24.50 Li 2.421 12.11 Mg 3.357 16.79 Cu 9.709 48.55

[0093] Example 2 (reduction method, hydrazine hydrate)

[0094] No. 2 vanadium electrolyte: vanadium electrolyte containing V 4+ and V 5+

[0095] A, draw a standard curve: take the standard material (PE company, N9300233) of the impurity elements (Ag, In, Al, K, As, Li, Mg) to be tested, and prepare a standard solution of each impurity element to be tested with water. The concentration of each impurity element to be tested in the standard solution is 1 μg / L, 5 μg / L, 10 μg / L, 15 μg / L, 20 μg / L; water is used as a blank solution; the blank solution and the standard solution are introduced into an inductively coupled plasma mass spectrometer to test, and the concentration and signal intensity value (blank) are taken as the horizontal and vertical coordinates, respectively, to draw a standard curve for each impurity element to be tested;

[0096] 1) Calculate the content of sulfate in the electrolyte: ​

[0097] Take 1 mL of No. 2 vanadium electrolyte and add 10 mL of 1.5 mol / L barium chloride solution to make the sulfate ions in the electrolyte react completely to form barium sulfate precipitate. After centrifugation, take the precipitate, wash with water, and centrifuge and wash for 3 more times. Dry the washed precipitate, calcine the precipitate to constant weight, and weigh the mass of barium sulfate, 1.0337 g. Calculate the sulfate content as 4.429 mol / L according to the mass of barium sulfate;

[0098] 2) Take the original vanadium electrolyte and test the concentrations of V 4+ , V 5+ in the electrolyte according to the standard “NB / T 42006-2013 Test Method for Electrolyte for All-vanadium Redox Flow Battery”. The concentrations of V 4+ and V 5+ are 0.698 mol / L and 0.963 mol / L, respectively;

[0099] 3) Take 50 mL of No. 2 original electrolyte and add 1.7 g of hydrazine hydrate with a mass concentration of 98% to reduce V 4 , V + , and V 5+ in the electrolyte to V 2+ and V 3+ , i.e., to make the electrolyte not contain V 4+ . Take this as the initial electrolyte;

[0100] 4) Add 37.868 g of barium hydroxide to the initial vanadium electrolyte obtained in step 3) and stir thoroughly to make sulfate and vanadium ions form precipitate and precipitate out. After the precipitate is completely formed, centrifuge and collect the supernatant;

[0101] 5) Wash the precipitate with water and centrifuge to take the supernatant. Repeat the washing and centrifugation of the precipitate for 3 times or more and collect all the supernatants;

[0102] 6) Transfer the supernatants obtained in steps 4) and 5) into a volumetric flask and add water to constant volume. Dilute to 10 times the volume of the original electrolyte taken in step 3);

[0103] 7) Prepare sample blank solution and test:

[0104] Prepare the precipitant aqueous solution with the required concentration according to the ratio of the mass of precipitant required in step 4) to the volume of constant volume in step 6) as sample blank solution 1;

[0105] Prepare the hydrazine hydrate aqueous solution with the required concentration according to the ratio of the mass of hydrazine hydrate required in step 3) to the volume of constant volume in step 6) as sample blank solution 2;

[0106] The sample blank solution 1, the sample blank solution 2 and the solution diluted in step 6) are introduced into the inductively coupled plasma mass spectrometer respectively to test the impurity element signal intensity value; the standard curve is obtained by substituting the standard curve, the concentration of the impurity element to be measured in the sample blank solution 1, the concentration of the impurity element to be measured in the sample blank solution 2 and the concentration of the impurity element to be measured in the detection sample solution;

[0107] The concentration of the impurity element in the 2nd original vanadium electrolyte is obtained by subtracting the corresponding impurity element concentration in the sample blank solution 1 and the sample blank solution 2 from the corresponding impurity element concentration in the detection sample solution, see Table 2, the second column of values; and multiplying the dilution multiple in step 6), see Table 2, the third column of values;

[0108] Table 2 Test results of impurity concentration of No. 2 electrolyte

[0109] Element Measured impurity concentration (pg / L) Original solution impurity concentration (pg / L) Ag 1.115 11.15 In 0.895 8.95 Al 0.985 9.85 K 1.521 15.21 As 2.102 21.02 Li 1.315 13.15 Mg 1.847 18.47

[0110] Example 3 (reduction method, electrochemical reduction)

[0111] No. 3 vanadium electrolyte: vanadium electrolyte containing V 4+ and V 5+

[0112] A, draw a standard curve: take the standard material of the impurity element to be measured (Ag, In, Al, K, As, Li, Mg) (PE company, N9300233), prepare a standard solution of each impurity element to be measured with water, the concentration of each impurity element to be measured in the standard solution is 1 μg / L, 5 μg / L, 10 μg / L, 15 μg / L, 20 μg / L; water as blank solution; the blank solution and the standard solution are introduced into the inductively coupled plasma mass spectrometer respectively to test, and the concentration and signal intensity value (blank) are taken as the horizontal and vertical coordinates respectively, and the standard curve of each impurity element to be measured is drawn respectively;

[0113] 1) Calculate the content of sulfate radical in the electrolyte:

[0114] Take 1 mL of No. 3 vanadium electrolyte and add 10 mL of 1.5 mol / L barium chloride solution to make the sulfate ions in the electrolyte react completely to form barium sulfate precipitate, centrifuge the precipitate, wash with water, and centrifuge and wash for 3 times, dry the washed precipitate, and burn the precipitate to constant weight, and weigh the mass of barium sulfate 1.0257 g, and calculate the mass of barium sulfate to obtain the content of sulfate radical 4.395 mol / L;

[0115] 2) Take the original vanadium electrolyte, and test the concentration of V 4+ , V 5+ in the electrolyte according to the standard "NB / T 42006-2013 Test Method for Electrolyte for All-vanadium Redox Flow Battery", which are 0.724 mol / L and 0.836 mol / L respectively;​

[0116] 3) Take 50 mL of the original electrolyte (No. 3) and add it to the cathode side of the battery. Place 50 mL of electrolyte containing V on the anode side. 2+ and V 3+ The vanadium electrolyte (laboratory-supplied electrolyte) was used to reduce the vanadium content in the cathode-side electrolyte using an electrochemical reduction method. 4+ V 5+ Restored to V 2 + and V 3+ Even if the electrolyte does not contain V 4+ This is used as the initial electrolyte.

[0117] 4) Add 37.577 g of barium hydroxide to the initial vanadium electrolyte obtained in step 3) and stir thoroughly to allow sulfate and vanadium ions to precipitate out; after precipitation is complete, centrifuge and collect the supernatant.

[0118] 5) Wash the precipitate with water and centrifuge to collect the supernatant; repeat the washing and centrifugation process for more than 3 times, and collect all the supernatant.

[0119] 6) Transfer the supernatant obtained in steps 4) and 5) into a volumetric flask, add water to make up to the final volume; dilute to 10 times the volume of the original electrolyte taken in step 3).

[0120] 7) Prepare a blank sample solution and test it:

[0121] Prepare an aqueous solution of precipitant of the required concentration according to the ratio of the required mass of precipitant in step 4) to the volume of precipitant adjusted in step 6), and use it as sample blank solution 1.

[0122] The sample blank solution 1 and the diluted solution in step 6) were respectively introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values ​​of impurity elements; the values ​​were then substituted into the standard curve to obtain the concentrations of the impurity elements to be tested in the sample blank solution 1 and the concentrations of the impurity elements to be tested in the test sample solution.

[0123] Subtract the concentration of the corresponding impurity element in the test sample solution from the concentration of the blank sample solution 1, as shown in the second column of Table 3; then multiply by the dilution factor in step 6) to obtain the concentration of the impurity element in the original vanadium electrolyte No. 3, as shown in the third column of Table 3.

[0124] Table 3. Test results of impurity concentration in electrolyte No. 3

[0125] Element Measured impurity concentration (pg / L) Original solution impurity concentration (pg / L) Ag 0.992 9.92 In 1.201 12.01 Al 1.511 15.11 K 2.081 20.81 As 1.619 16.19 Li 1.617 16.17 Mg 2.167 21.67

[0126] Example 4 (Oxidation Method)

[0127] Vanadium electrolyte No. 4: Contains only V 5+ V-free 2+ V 3+and V 4+ Vanadium electrolyte

[0128] A, draw standard curve: take the measured impurity elements (Ag, In, Al, K, As, Li, Mg) standard material (PE company, N9300233), with water preparation of each of the measured impurity element standard solution, each of the measured impurity element concentration in the standard solution is 1 μg / L, 5 μg / L, 10 μg / L, 15 μg / L, 20 μg / L; with water as blank; the blank and standard solution are introduced into the inductively coupled plasma mass spectrometer test, with concentration and signal intensity value (deducting blank) as the horizontal and vertical coordinates, respectively, to draw each of the measured impurity element standard curve;

[0129] 1) calculate the content of sulfate in electrolyte:

[0130] Take 1 mL of No. 4 vanadium electrolyte and add 10 mL of 1.5 mol / L barium chloride solution, so that the sulfate ions in the electrolyte react completely to form barium sulfate precipitate. After centrifugation, take the precipitate, wash with water, and then centrifuge and wash again, at least 3 times. Dry the washed precipitate, and burn the precipitate to constant weight. Weigh the mass of barium sulfate, 1.0426 g. According to the mass of barium sulfate, the content of sulfate is calculated to be 4.467 mol / L.

[0131] 2) Take 50 mL of No. 4 electrolyte and heat to 90℃ for 1.5 hours. After the precipitate is completely precipitated, centrifuge and reserve the supernatant. Wash the precipitate with water and centrifuge to obtain the supernatant. Repeat the washing and centrifugation of the precipitate for 3 times or more, and collect the supernatant. Mix all the supernatants to obtain a mixed solution.

[0132] 3) Add 38.193 g of barium hydroxide to the mixed solution and stir thoroughly to allow the sulfate to form a precipitate and be precipitated out, while consuming a large amount of hydrogen ions in the solution to reduce the concentration of hydrogen ions. After the precipitate is completely precipitated, centrifuge and collect the supernatant.

[0133] 4) Wash the precipitate with water and centrifuge to obtain the supernatant. Repeat the washing and centrifugation of the precipitate for 3 times or more, and collect all the supernatants.

[0134] 5) Transfer the supernatant obtained in steps 3) and 4) to a volumetric flask and add water to constant volume. Dilute to 10 times the volume of the original No. 4 electrolyte taken in step 2).

[0135] 6) Prepare a sample blank solution: prepare a water solution of the required concentration of precipitant according to the ratio of the mass of precipitant required in step 3) to the volume of constant volume in step 4), as the sample blank solution.

[0136] The sample blank solution and the solution diluted in step 5) are respectively introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values of impurity elements; the standard curve is obtained by substituting the concentration of the impurity elements to be measured in the sample blank solution and the concentration of the impurity elements to be measured in the detection sample solution;

[0137] The concentration of the impurity elements in the original vanadium electrolyte of step 2) is obtained by subtracting the corresponding impurity element concentration in the sample blank solution from the corresponding impurity element concentration in the detection sample solution, as shown in Table 4, column 2; and then multiplying by the dilution factor in step 5), as shown in Table 4, column 3;

[0138] Table 4 Test results of impurity concentrations of No. 4 electrolyte

[0139]

[0140]

[0141] Example 5 (oxidation method, with hydrogen peroxide)

[0142] No. 5 vanadium electrolyte: containing V 2+ , V 3+ vanadium electrolyte

[0143] A, draw a standard curve: take the standard material (PE company, N9300233) of the impurity elements (Ag, In, Al, K, As, Li, Mg) to be measured, and prepare a standard solution of each impurity element to be measured with water, and the concentration of each impurity element to be measured in the standard solution is 1 μg / L, 5 μg / L, 10 μg / L, 15 μg / L, 20 μg / L; water as blank solution; the blank solution and the standard solution are respectively introduced into an inductively coupled plasma mass spectrometer to test, and the concentration and signal intensity value (blank) are taken as the horizontal and vertical coordinates respectively, and the standard curve of each impurity element to be measured is drawn;

[0144] 1) Calculate the content of sulfate ions in the electrolyte:

[0145] Take 1 mL of No. 5 vanadium electrolyte and add 10 mL of 1.5 mol / L barium chloride solution to make the sulfate ions in the electrolyte react completely to form barium sulfate precipitate. After centrifugation, take the precipitate, wash with water, and centrifuge again, at least 3 times. Dry the washed precipitate, and burn the precipitate to constant weight. The mass of barium sulfate is 1.0024 g. According to the mass of barium sulfate, the content of sulfate ions is calculated to be 4.295 mol / L;

[0146] 2) Take No. 5 original vanadium electrolyte, and test the concentrations of V 2+ , V 3+ in the electrolyte according to the standard "NB / T 42006-2013 Test Method for Electrolyte for All-vanadium Redox Flow Battery", which are 0.654 mol / L and 0.673 mol / L, respectively;

[0147] 3) Take 50 mL of the original electrolyte No. 5, add 9.375 g of 30% wt H2O2 solution, so that V 2+ , V 3+ is completely oxidized to V 5+ , i.e. so that the electrolyte does not contain V 4+ ; use this as the initial electrolyte;

[0148] 4) Heat the initial vanadium electrolyte obtained in step 3) to 100°C and keep the temperature constant for 1.5 hours, after the precipitation is complete, centrifuge and retain the supernatant; wash the precipitate with water and centrifuge to obtain the supernatant; repeatedly wash the precipitate and centrifuge for more than 3 times, collect the supernatant, and mix all the supernatants to obtain a mixed solution;

[0149] 5) Add 36.722 g of barium hydroxide to the mixed solution, stir well, so that the sulfate ions form a precipitate and are separated out, and at the same time consume a large amount of hydrogen ions in the solution, so that the concentration of hydrogen ions is reduced; after the precipitation is complete, centrifuge and collect the supernatant;

[0150] 6) Wash the precipitate with water and centrifuge to obtain the supernatant; repeatedly wash the precipitate and centrifuge for more than 3 times, collect all the supernatants;

[0151] 7) Transfer the supernatant obtained in steps 5) and 6) into a volumetric flask, add water to constant volume; dilute to 10 times the volume of the original electrolyte taken in step 3);

[0152] 8) Prepare a sample blank solution:

[0153] Prepare a precipitant aqueous solution of the required concentration according to the ratio of the mass of the precipitant required in step 5) to the volume of the constant volume in step 7), as sample blank solution 1;

[0154] Prepare an oxidizing agent H2O2 solution of the required concentration according to the ratio of the amount of oxidizing agent H2O2 required in step 3) to the volume of the constant volume in step 7), as sample blank solution 2;

[0155] Introduce sample blank solution 1, sample blank solution 2 and the solution diluted in step 7) into an inductively coupled plasma mass spectrometer respectively to test the signal intensity values of the impurity elements; substitute into the standard curve to obtain the concentrations of the impurity elements to be tested in sample blank solution 1, sample blank solution 2 and the detection sample solution;

[0156] Subtract the concentrations of the corresponding impurity elements to be tested in sample blank solution 1 and sample blank solution 2 from the concentration of the corresponding impurity elements to be tested in the detection sample solution, see the values in the second column of Table 5; then multiply by the dilution factor in step 7) to obtain the concentrations of the impurity elements in the original vanadium electrolyte in step 3), see the values in the third column of Table 5;

[0157] Table 5 No. 5 electrolyte impurity concentration test results

[0158] Element Measured impurity concentration (pg / L) Original solution impurity concentration (pg / L) Ag 1.849 18.49 In 1.642 16.42 Al 2.010 20.10 K 2.312 23.12 As 2.230 22.30 Li 2.091 20.91 Mg 2.610 26.10

[0159] Example 6 (oxidation method, electrochemical oxidation method)

[0160] No. 6 vanadium electrolyte: containing V 2+ , V 3+ vanadium electrolyte

[0161] A, draw a standard curve: take the standard material (PE company, N9300233) of the impurity elements (Ag, In, Al, K, As, Li, Mg) to be measured, prepare a standard solution of each impurity element to be measured with water, and the concentration of each impurity element to be measured in the standard solution is 1 μg / L, 5 μg / L, 10 μg / L, 15 μg / L, 20 μg / L; with water as a blank solution; the blank solution and the standard solution are introduced into the inductively coupled plasma mass spectrometer for testing, and the concentration and signal intensity value (determined by blank) are taken as the horizontal and vertical coordinates respectively, and the standard curve of each impurity element to be measured is drawn respectively;

[0162] 1) Calculate the content of sulfate in the electrolyte:

[0163] Take 1 mL of No. 6 vanadium electrolyte and add 10 mL of 1.5 mol / L barium chloride solution to make the sulfate ions in the electrolyte react completely to form barium sulfate precipitate. After centrifugation, take the precipitate, wash with water, and centrifuge again. Wash at least 3 times, dry the washed precipitate, and burn the precipitate to constant weight. The mass of barium sulfate is 1.0547 g. According to the mass of barium sulfate, the content of sulfate is calculated to be 4.519 mol / L;

[0164] 2) Take No. 6 vanadium electrolyte, and test the concentration of V 2+ , V 3+ in the electrolyte according to the standard "NB / T 42006-2013 Test Method for Electrolyte for All-vanadium Redox Flow Battery". The concentration of V 2+ and V 3+ is 0.594 mol / L and 0.811 mol / L respectively;

[0165] 3) Take 50 mL of No. 6 original electrolyte and place it in the anode side of the battery. Place 50 mL of vanadium electrolyte containing V 5+ and V 4+ (including laboratory-prepared electrolyte) in the cathode side. Use electrochemical oxidation method to make V 2+ , V 3+ in the electrolyte be completely oxidized to V 5+ , i.e. to make the electrolyte not contain V 4+ ; use it as the initial electrolyte;

[0166] 4) The initial vanadium electrolyte obtained in step 3) is heated to 100°C and kept at this temperature for more than 1 hour until the precipitation is complete, then centrifuged to retain the supernatant; the precipitate is washed with water and centrifuged to obtain the supernatant; the precipitate is repeatedly washed and centrifuged for more than 3 times, and all the supernatants are collected and mixed to obtain a mixed solution;

[0167] 5) Barium hydroxide 38.637 g is added to the mixed solution, and stirred thoroughly to precipitate sulfate and consume a large amount of hydrogen ions in the solution, so that the concentration of hydrogen ions is reduced; after the precipitation is complete, the supernatant is collected by centrifugation;

[0168] 6) The precipitate is washed with water and centrifuged to obtain the supernatant; the precipitate is repeatedly washed and centrifuged for more than 3 times, and all the supernatants are collected;

[0169] 7) The supernatants obtained in steps 5) and 6) are transferred into a volumetric flask, and water is added to make up the volume; the solution is diluted to 10 times the volume of the original electrolyte solution taken in step 3);

[0170] 8) Preparation of sample blank solution:

[0171] The sample blank solution 1 is prepared according to the ratio of the mass of the precipitant required in step 5) to the volume of the solution prepared in step 7);

[0172] If the electrochemical oxidation method is used in step 2), the sample blank solution 1 and the solution diluted in step 7) are introduced into an inductively coupled plasma mass spectrometer respectively to test the signal intensity values of the impurity elements; the concentrations of the impurity elements in the sample blank solution 1 and the test sample solution are obtained by substituting into the standard curve;

[0173] The concentration of the corresponding impurity element in the test sample solution is subtracted from the concentration of the corresponding impurity element in the sample blank solution 1, as shown in the second column of Table 6; then multiplied by the dilution factor in step 7) to obtain the concentration of the impurity element in the original vanadium electrolyte in step 3), as shown in the third column of Table 6;

[0174] Table 6 Test results of impurity concentrations in No. 6 electrolyte

[0175] Element Measured impurity concentration (pg / L) Original solution impurity concentration (pg / L) Ag 1.601 16.01 In 1.315 13.15 Al 1.023 10.23 K 1.912 19.12 As 2.511 25.11 Li 2.341 23.41 Mg 2.108 21.08

[0176] Example 7 (direct dilution and detection, comparative example of Example 1, precision test)

[0177] No. 7 vanadium electrolyte: vanadium electrolyte containing V 2+ and V 3+

[0178] ​A, draw standard curve: take the impurity elements (As, Cu) standard material (PE company, N9300233), with water to prepare each standard solution of the impurity elements, the concentration of each impurity element in the standard solution is 1 μg / L, 5 μg / L, 10 μg / L, 15 μg / L, 20 μg / L; With water as blank; The blank and standard solution are introduced into the inductively coupled plasma mass spectrometer for testing, and the concentration and signal intensity value (deducting blank) are taken as the horizontal and vertical coordinates respectively, and the standard curve of each impurity element is drawn respectively;

[0179] 1) Prepare the detection sample solution. Take 1 mL of No. 7 vanadium electrolyte, place it in a 1 L volumetric flask, add pure water to dilute to constant volume, dilute to 1000 times the volume of No. 2 original electrolyte, and obtain the sample solution to be tested;

[0180] 2) The solution diluted in step 1) is introduced into the inductively coupled plasma mass spectrometer to test the impurity element signal intensity value; Substitute into the standard curve to obtain the concentration of the impurity element to be tested in the detection sample solution;

[0181] The values obtained by deducting the sample blank in comparative example 1 and example 7 are not multiplied by the dilution multiple, and 6 independent sample repeatability tests are carried out respectively, and the precision of the method of the application is evaluated according to the relative standard deviation. The results of two tests are shown in Table 7:

[0182] Table 7 Comparison of determination results of example 1 and example 7

[0183]

[0184] n is the number of measurements of the sample;

[0185] w i is the ith measurement value of the sample;

[0186] is the average value of n measurements,

[0187]

[0188] As shown in Table 7, the comparison of example 1 and example 7 shows that the method used in example 1 has low dilution multiple, high impurity concentration, and smaller relative standard deviation, which indicates that the method of the application has better precision and reproducibility.

[0189] Example 8 (accuracy test, standard addition recovery)

[0190] 8 No. Vanadium electrolyte: vanadium electrolyte containing V 2+ and V 3+

[0191] ​A, draw standard curve: take In element standard material (PE company, N9300233), with water to prepare In element standard solution, In element concentration in standard solution is 1 μg / L, 5 μg / L, 10 μg / L, 15 μg / L, 20 μg / L;With water as blank liquid;The blank liquid and standard solution are introduced into inductively coupled plasma mass spectrometer respectively, and the concentration and signal intensity value (deducting blank) are taken as the horizontal and vertical coordinates respectively, and the standard curve of In element is drawn;

[0192] 1) Calculate the content of sulfate radical in electrolyte:

[0193] Take 1 mL of No. 8 vanadium electrolyte and add 10 mL of 1.5 mol / L barium chloride solution to make the sulfate radical in the electrolyte react completely to form barium sulfate precipitate. After centrifugation, take the precipitate, wash with water, and centrifuge for washing 3 times. Dry the washed precipitate, and burn the precipitate to constant weight. Weigh the mass of barium sulfate 1.0099 g, and calculate the content of sulfate radical as 4.327 mol / L according to the mass of barium sulfate;

[0194] 2) Take 50 mL of No. 8 original vanadium electrolyte and add 36.996 g of barium hydroxide, and stir thoroughly to make the sulfate radical and vanadium ion form precipitate and precipitate, and at the same time consume a large amount of hydrogen ions in the solution to reduce the concentration of hydrogen ions. After the precipitate is completely precipitated, centrifuge and collect the supernatant;

[0195] 3) Wash the precipitate with water and centrifuge to obtain the supernatant. Repeat the washing and centrifugation of the precipitate for more than 3 times, and collect all the supernatant;

[0196] 4) Transfer the supernatant obtained in steps 2) and 3) into a volumetric flask, and add water to constant volume; Dilute to 5 times the volume of the original electrolyte taken in step 2);

[0197] 5) Prepare sample blank solution: prepare the required concentration of precipitant aqueous solution according to the ratio of the mass of precipitant required in step 2) to the volume of constant volume in step 4), as the sample blank solution;

[0198] Introduce the sample blank solution prepared in step 5) and the solution diluted in step 4) into the inductively coupled plasma mass spectrometer respectively to test the signal intensity value of In element; Substitute into the standard curve to obtain the In element concentration in the sample blank solution and the In element concentration in the detection sample solution;

[0199] Subtract the In element concentration in the sample blank solution from the In element concentration in the detection sample solution to obtain the measured In element concentration of No. 8 electrolyte;

[0200] 6) Take another 50 mL of No. 8 electrolyte, and add 250 μL of In standard solution (PE company, N9300233) with a concentration of 10 mg / L to obtain the spiked electrolyte.

[0201] 7) Take all the volume of the added electrolyte in step 6, repeat steps 2)-5);

[0202] The test results are shown in Table 8

[0203] Table 8 Test results of In element concentration in electrolyte

[0204]

[0205]

[0206] Calculate the added recovery rate P of In according to the data in Table 8

[0207]

[0208] C 加标 C is the concentration of In in the mixed solution measured after adding the standard solution,

[0209] C 未加标 C is the concentration of In in the mixed solution measured after not adding the standard solution,

[0210] V is the final dilution volume of the solution, 250 mL

[0211] C 标 C is the concentration of In standard solution, 100 mg / L;

[0212] V 标 V is the volume of In standard solution added, 25 μL;

[0213] The requirement for the recovery rate of trace components in experimental analysis is (100±10)%, the added recovery rate shown in Table 8 is within (100±5)%, which meets the requirements, indicating that the determination results are accurate.

Claims

1. A method for determining the concentration of impurity elements in a vanadium electrolyte, comprising: A. Plotting Standard Curves: Take the standard substances of the impurity elements to be tested, and prepare standard solutions with water at least 5 different concentration points for each impurity element to be tested. The concentration of each impurity element to be tested in the standard solutions should be within the range of 0.001-100 μg / L. Use water as the blank solution. Introduce the blank solution and the standard solution into an inductively coupled plasma mass spectrometer for testing. Plot the standard curves for each impurity element to be tested with the concentration and signal intensity values ​​as the x and y axes, respectively. The method of the present invention can be used to determine all main group and subgroup metal elements contained in vanadium electrolytes, with a concentration range of 0.001~100 μg / L that can be detected by inductively coupled plasma mass spectrometry, as well as one or more of the elements Be, Si, B, P, S, As, Se, Br, Te, and I. B. The process consists of the following steps (I) or (II): (a) Contains V 2+ V 3+ One or two of the vanadium electrolytes, and which do not contain V 4+ The measurement process; 1) Calculate the sulfate content in the electrolyte: Add excess 0.5-1.5 mol / L barium chloride solution to the original vanadium electrolyte to ensure complete reaction of sulfate ions in the electrolyte, forming barium sulfate precipitate. After centrifugation, take the precipitate, wash it with water, and then centrifuge and wash it again, at least 3 times. Dry the washed precipitate, ignite the precipitate to constant weight, weigh the mass of barium sulfate, and calculate the sulfate content based on the mass of barium sulfate. To ensure complete sulfate precipitation, the amount of barium chloride added should be calculated as 101%-200% of the amount of barium chloride required for complete precipitation at the upper limit of 8 mol / L sulfate concentration. 2) Take the original vanadium electrolyte, add the precipitant, and stir thoroughly to allow sulfate and vanadium ions to precipitate and precipitate out. At the same time, it consumes a large number of hydrogen ions in the solution, thus reducing the hydrogen ion concentration. The amount of precipitant used is the amount required for complete precipitation of sulfate ions in the vanadium electrolyte; after complete precipitation, centrifuge and collect the supernatant; Precipitating agent: one or two of barium hydroxide and calcium hydroxide; 3) Wash the precipitate with water and centrifuge to collect the supernatant; repeat the washing and centrifugation process for more than 3 times, and collect all the supernatant. 4) Transfer the supernatant obtained in steps 2) and 3) into a volumetric flask, add water to make up to the final volume; dilute to 2-10 times the volume of the original electrolyte taken in step 2); 5) Prepare sample blank solution: Prepare an aqueous solution of precipitant of the required concentration according to the ratio of the required mass of precipitant in step 2) to the volume of the solution in step 4), as the sample blank solution; The sample blank solution prepared in step 5) and the diluted solution in step 4) are respectively introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values ​​of impurity elements; the values ​​are then substituted into the standard curve to obtain the concentrations of the impurity elements to be tested in the sample blank solution and the concentrations of the impurity elements to be tested in the test sample solution. Subtract the concentration of the corresponding impurity element in the blank sample solution from the concentration of the corresponding impurity element in the test sample solution, and then multiply by the dilution factor in step 4) to obtain the concentration of the impurity element in the original vanadium electrolyte in step 2). Or, (ii) containing V 4+ V 5+ The determination process of one or two vanadium electrolytes; 1) Take the original vanadium electrolyte and repeat step 1) of step (I) above; 2) Take the original vanadium electrolyte and test the Vt content in the electrolyte according to the standard "NB / T 42006-2013 Test Method for Electrolytes for Vanadium Redox Flow Batteries". 4+ V 5+ The concentration; 3) Take the same original electrolyte as in step 1), add hydrazine hydrate as a reducing agent or use an electrochemical reduction method to reduce the V in the electrolyte. 4+ V 5+ Restored to V 2+ and / or V 3+ Even if the electrolyte does not contain V 4+ ; This is used as the initial electrolyte; The amount of hydrazine hydrate used is to reduce the V in the electrolyte. 4+ and V 5+ Completely restored to V 3+ The required amount of substance is the minimum amount to be added, in order to reduce the V in the electrolyte. 4+ and V 5+ Completely restored to V 2+ The required amount of substance is the maximum amount that can be added. 4) Add a precipitant to the initial vanadium electrolyte obtained in step 3) and stir thoroughly to allow sulfate and vanadium ions to precipitate out; the amount of precipitant used is the amount of substance required for complete precipitation of sulfate in the vanadium electrolyte; after complete precipitation, centrifuge and collect the supernatant. Precipitating agent: one or two of barium hydroxide and calcium hydroxide; 5) Repeat step 3) of step (I) above; 6) Transfer the supernatant obtained in steps 4) and 5) into a volumetric flask, add water to make up to the final volume; dilute to 2-10 times the volume of the original electrolyte taken in step 3); 7) Prepare a blank sample solution and test it: Prepare an aqueous solution of precipitant of the required concentration according to the ratio of the required mass of precipitant in step 4) to the volume of precipitant adjusted in step 6), and use it as sample blank solution 1. If the electrochemical reduction method is used in step 3), the sample blank solution 1 and the diluted solution in step 6) are respectively introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values ​​of impurity elements; the values ​​are then substituted into the standard curve to obtain the concentration of the impurity element to be tested in the sample blank solution 1 and the concentration of the impurity element to be tested in the test sample solution. Subtract the concentration of the corresponding impurity element in sample blank solution 1 from the concentration of the corresponding impurity element in the test sample solution, and then multiply by the dilution factor in step 6) to obtain the concentration of the impurity element in the original vanadium electrolyte in step 3). Alternatively, if hydrazine hydrate, a reducing agent, is added to the initial electrolyte in step 3), prepare an aqueous solution of hydrazine hydrate of the required concentration according to the ratio of the mass of hydrazine hydrate required in step 3) to the volume of the solution made in step 6), and use it as sample blank solution 2. Sample blank solution 1, sample blank solution 2, and the diluted solution from step 6) were respectively introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values ​​of impurity elements; the values ​​were then substituted into the standard curve to obtain the concentrations of the impurity elements to be tested in sample blank solution 1, sample blank solution 2, and the test sample solution. Subtract the concentrations of the corresponding impurity elements in sample blank solution 1 and sample blank solution 2 from the concentration of the corresponding impurity element in the test sample solution, and then multiply by the dilution factor in step 6) to obtain the concentration of the impurity element in the original vanadium electrolyte in step 3).

2. The determination method according to claim 1, characterized in that: The vanadium electrolyte to be tested contains vanadium ions as its main component. 2+ V 3+ V 4+ V 5+ The total vanadium concentration is 1-3 mol / L, the sulfate ion concentration is 1-8 mol / L, and the hydrogen ion concentration is 1-8 mol / L.

3. The determination method according to claim 1, characterized in that: In step 3) of step (I), the amount of water used to wash the precipitate should not exceed 1 / 5 of the volume of the initial electrolyte taken in step 2) of step (I); The mass concentration of hydrazine hydrate is 60%-98%.

4. A method for determining the concentration of impurity elements in vanadium electrolyte, characterized in that: include: A. Plotting Standard Curves: Take the standard substances of the impurity elements to be tested, and prepare standard solutions with water at least 5 different concentration points for each impurity element to be tested. The concentration of each impurity element to be tested in the standard solutions should be within the range of 0.001-100 μg / L. Use water as the blank solution. Introduce the blank solution and the standard solution into an inductively coupled plasma mass spectrometer for testing. Plot the standard curves for each impurity element to be tested with the concentration and signal intensity values ​​as the x and y axes, respectively. The method of the present invention can be used to determine all main group and subgroup metal elements contained in vanadium electrolytes, with a concentration range of 0.001~100 μg / L that can be detected by inductively coupled plasma mass spectrometry, as well as one or more of the elements Be, Si, B, P, S, As, Se, Br, Te, and I. B. The process consists of the following steps (I) or (II): (a) V 5+ The determination process of vanadium electrolyte; 1) Calculate the sulfate content in the electrolyte: Take the original electrolyte and add excess barium chloride solution with a concentration of 0.5-1.5 mol / L to ensure that the sulfate ions in the electrolyte react completely and form barium sulfate precipitate. After centrifugation, take the precipitate, wash it with water, and then centrifuge and wash it again, at least 3 times. Dry the washed precipitate, ignite the precipitate to constant weight, weigh the barium sulfate, and calculate the sulfate content based on the mass of barium sulfate. To ensure complete sulfate precipitation, the amount of barium chloride added should be calculated as 101%-200% of the amount of barium chloride required for complete precipitation at the upper limit of 8 mol / L sulfate concentration. 2) Take the original electrolyte and heat it to 60-100℃, keep it at the temperature for more than 1 hour, and after precipitation is complete, centrifuge and keep the supernatant; wash the precipitate with water and centrifuge to collect the supernatant; repeat washing the precipitate and centrifuging more than 3 times, collect the supernatant, and mix all the supernatants to obtain a mixture. 3) Add a precipitant to the mixture and stir thoroughly to allow sulfate ions to precipitate and precipitate out. At the same time, this consumes a large number of hydrogen ions in the solution, thus reducing the hydrogen ion concentration. The amount of precipitant used is the amount required for complete precipitation of sulfate ions in the vanadium electrolyte; after complete precipitation, centrifuge and collect the supernatant; Precipitating agent: one or two of barium hydroxide and calcium hydroxide; 4) Wash the precipitate with water and centrifuge to collect the supernatant; repeat the washing and centrifugation process for more than 3 times, and collect all the supernatant. 5) Transfer the supernatant obtained in steps 3) and 4) into a volumetric flask, add water to make up to the final volume; dilute to 2-10 times the volume of the original electrolyte taken in step 2); 6) Prepare sample blank solution: Prepare an aqueous solution of precipitant of the required concentration according to the ratio of the required mass of precipitant in step 3) to the volume of the solution in step 4), as the sample blank solution; The sample blank solution and the diluted solution from step 5) were respectively introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values ​​of impurity elements; the values ​​were then substituted into the standard curve to obtain the concentrations of the impurity elements to be tested in the sample blank solution and the sample solution. Subtract the concentration of the corresponding impurity element in the blank sample solution from the concentration of the corresponding impurity element in the test sample solution, and then multiply by the dilution factor in step 5) to obtain the concentration of the impurity element in the original vanadium electrolyte in step 2). Or, (ii) containing V 2+ V 3+ V 4+ The determination process of one or two vanadium electrolytes; 1) Take the original vanadium electrolyte and repeat step 1) of step (I) above; 2) Take the original vanadium electrolyte and test the Vt content in the electrolyte according to the standard "NB / T 42006-2013 Test Method for Electrolytes for Vanadium Redox Flow Batteries". 2+ V 3+ V 4+ The concentration; 3) Take the same original electrolyte as in step 1), add the oxidant H2O2 or use an electrochemical oxidation method to increase the V in the electrolyte. 2+ V 3+ V 4+ Completely oxidized to V 5+ Even if the electrolyte does not contain V 4+ This is used as the initial electrolyte. The amount of H2O2 used is to reduce the V in the electrolyte. 2+ V 3+ V 4+ Completely oxidized to V 5+ 100%-110% of the required amount of substance; 4) Heat the initial vanadium electrolyte obtained in step 3) to 60-100℃ and keep it at that temperature for more than 1 hour until precipitation is complete. Centrifuge and retain the supernatant. Wash the precipitate with water and centrifuge to collect the supernatant. Repeat washing the precipitate and centrifuging more than 3 times to collect the supernatant. Mix all the supernatants to obtain a mixture. 5) Repeat step 3) of step (I) above; 6) Repeat step 4) of step (I) above; 7) Transfer the supernatant obtained in steps 5) and 6) into a volumetric flask, add water to make up to the final volume; dilute to 2-10 times the volume of the original electrolyte taken in step 3); 8) Prepare sample blank solution: Prepare an aqueous solution of precipitant of the required concentration according to the ratio of the required mass of precipitant in step 5) to the volume of precipitant adjusted in step 7), and use it as sample blank solution 1. If the electrochemical oxidation method is used in step 2), the sample blank solution 1 and the diluted solution in step 7) are respectively introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values ​​of impurity elements; the values ​​are then substituted into the standard curve to obtain the concentration of the impurity element to be tested in the sample blank solution 1 and the concentration of the impurity element to be tested in the test sample solution. Subtract the concentration of the corresponding impurity element in sample blank solution 1 from the concentration of the corresponding impurity element in the test sample solution, and then multiply by the dilution factor in step 7) to obtain the concentration of the impurity element in the original vanadium electrolyte in step 3). Alternatively, if oxidant H2O2 is added to the original electrolyte in step 3), prepare an oxidant H2O2 solution of the required concentration according to the ratio of the amount of oxidant H2O2 required in step 3) to the volume of the solution made in step 7), and use it as sample blank solution 2. Sample blank solution 1, sample blank solution 2, and the diluted solution from step 7) were respectively introduced into an inductively coupled plasma mass spectrometer to test the signal intensity values ​​of impurity elements; the values ​​were then substituted into the standard curve to obtain the concentrations of the impurity elements to be tested in sample blank solution 1, sample blank solution 2, and the test sample solution. Subtract the concentrations of the corresponding impurity elements in sample blank solution 1 and sample blank solution 2 from the concentration of the corresponding impurity element in the test sample solution, and then multiply by the dilution factor in step 7) to obtain the concentration of the impurity element in the original vanadium electrolyte in step 3).

5. The determination method according to claim 4, characterized in that: The vanadium electrolyte to be tested contains vanadium ions as its main component. 2+ V 3+ V 4+ V 5+ The total vanadium concentration is 1-3 mol / L, the sulfate ion concentration is 1-8 mol / L, and the hydrogen ion concentration is 1-8 mol / L.

6. The determination method according to claim 4, characterized in that: In steps 2) and 4) of step (I), the amount of water used to wash the precipitate is 1 / 5 of the volume of the original electrolyte taken in step 2) of step (I); the mass concentration of H2O2 is 10-30%.

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