Determination method for content of cobalt in cobaltosic oxide material

Abstract

The present invention relates to the technical field of cobalt content determination, and disclosed is a determination method for the content of cobalt in a cobaltosic oxide material. The determination method comprises: calcining a cobaltosic oxide sample in an inert atmosphere to completely react cobaltosic oxide into cobaltous oxide; using hydrochloric acid to digest a calcined product obtained by calcination to obtain a digestion solution; using a potassium ferricyanide solution as a titrant to perform potentiometric titration on the digestion solution, wherein the titration process comprises: reacting an excess of the potassium ferricyanide solution with the digestion solution to completely react divalent cobalt in the digestion solution into trivalent cobalt, and then titrating the remaining unreacted potassium ferricyanide solution in a titration system with a cobalt standard solution until a jump point is reached; then calculating the content of cobalt in the sample on the basis of a formula. The method is simple and safe, and provides highly accurate and stable test results.

Description

A method for determining the cobalt content in cobalt tetroxide material Technical Field

[0001] The present disclosure relates to the technical field of cobalt content determination, and in particular to a method for determining the cobalt content in a cobalt trioxide material. Background Art

[0002] The new energy electric vehicle industry is currently developing rapidly, and the demand for power batteries is increasing. As a result, the demand for positive electrode materials is increasing. Lithium cobalt oxide (LiCoO2) has become the preferred material for lithium-ion battery cathode active materials due to its high specific energy, stable discharge voltage, long cycle life and easy preparation.

[0003] As a precursor to lithium cobalt oxide, the accurate measurement of cobalt in cobalt tetroxide is extremely important. Current methods for measuring the cobalt content in cobalt tetroxide have high ranges, poor accuracy, and some even pose safety risks.

[0004] In view of this, the present disclosure is proposed.

[0005] Summary of the Invention

[0006] The purpose of the present disclosure is to provide a method for determining the cobalt content in cobalt trioxide material to solve or improve the above technical problems.

[0007] The present disclosure can be implemented as follows:

[0008] The present disclosure provides a method for determining the cobalt content in a cobalt oxide material, which comprises the following steps:

[0009] The cobalt trioxide sample is burned under an inert atmosphere to completely react the cobalt trioxide into cobaltous oxide; the burned product obtained by burning is digested with hydrochloric acid to obtain a digestion solution; and the digestion solution is potentiometrically titrated using potassium ferricyanide solution as a titrant;

[0010] The titration process includes: reacting an excess amount of potassium ferricyanide solution with a digestion solution to completely react the divalent cobalt in the digestion solution into trivalent cobalt; then titrating the remaining unreacted potassium ferricyanide solution in the titration system with a cobalt standard solution until the jump point is reached;

[0011] The cobalt content in the sample was calculated using the following formula: Co% = {[ρ(V1×K-V2)×n] / [m÷(1-w 灼失量 %)]}×100%;

[0012] Wherein, ρ is the concentration of the cobalt standard solution, in g / mL;

[0013] V1 is the total volume of potassium ferricyanide solution, in mL;

[0014] K is the ratio of the volume of the cobalt standard solution required to titrate the potassium ferricyanide solution of V1 to V1;

[0015] V2 is the volume of cobalt standard solution consumed during back titration, in mL;

[0016] n is the dilution factor;

[0017] m is the mass of the burned material used for digestion, in g;

[0018] w 灼失量 % is the mass percentage of the cobalt oxide sample lost during the ignition process.

[0019] In an optional embodiment, the burning temperature is not less than 900°C.

[0020] In an alternative embodiment, the calcination temperature is 940°C-960°C.

[0021] In an optional embodiment, the burning time is 1 hour to 2 hours.

[0022] In an alternative embodiment, the calcination is performed under an inert gas atmosphere.

[0023] In an alternative embodiment, the calcination is performed under a nitrogen atmosphere.

[0024] In an optional embodiment, after the burning, the burned material is first cooled to below 400° C. and then digested with hydrochloric acid.

[0025] In an optional embodiment, the burning material is cooled to 200°C-220°C.

[0026] In an optional embodiment, the digestion temperature is 200° C.-300° C., and the digestion time is 2 min-3 min.

[0027] In an optional embodiment, 18 mL to 22 mL of hydrochloric acid is used for every 1 g of the burned material.

[0028] In an optional embodiment, an excess amount of potassium ferricyanide solution is reacted with the digestion solution at a pH value of 9.8 to 10.0.

[0029] In an optional embodiment, the concentration of the potassium ferricyanide solution is 16 g / L-18 g / L.

[0030] In an optional embodiment, an ammonia-ammonium citrate mixture is further added during the reaction of the excess potassium ferricyanide solution with the digestion solution.

[0031] In an optional embodiment, in the ammonia water-ammonium citrate mixture, the usage ratio of ammonia water to ammonium citrate is 350 mL:48 g to 350 mL:52 g.

[0032] In an optional embodiment, the temperature of the ammonia-ammonium citrate mixture used is 3°C-5°C.

[0033] In an optional embodiment, the concentration of the cobalt standard solution is 2.8 g / L-3.2 g / L.

[0034] In an optional embodiment, the mode of potentiometric titration is MET mode.

[0035] In an alternative embodiment, the signal drift of the potentiometric titration is 18 mv / min-22 mv / min.

[0036] In an alternative embodiment, the volume increment of the potentiometric titration is 0.015 mL to 0.025 mL.

[0037] The beneficial effects of the present disclosure include:

[0038] The assay method disclosed herein first ignites the sample under an inert atmosphere, removing any adhering water from the sample while completely reacting cobalt tetroxide to form cobaltous oxide, which can be completely digested with hydrochloric acid. This eliminates the need for hazardous reagents such as perchloric acid, which can easily lead to material loss. This digestion, which allows the cobaltous oxide to completely react to form cobalt chloride, is then potentiometrically titrated using potassium ferricyanide solution as a titrant, resulting in relatively accurate and stable assay results. DETAILED DESCRIPTION

[0039] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0040] The method for determining the cobalt content in the cobalt trioxide material provided by the present disclosure is described in detail below.

[0041] The present disclosure provides a method for determining the cobalt content in a cobalt oxide material, which comprises the following steps:

[0042] The cobalt trioxide sample is burned under an inert atmosphere to completely react the cobalt trioxide into cobaltous oxide; the burned product obtained by burning is digested with hydrochloric acid to obtain a digestion solution; and the digestion solution is potentiometrically titrated using potassium ferricyanide solution as a titrant;

[0043] The titration process includes: reacting an excess amount of potassium ferricyanide solution with a digestion solution to completely react the divalent cobalt in the digestion solution into trivalent cobalt; then titrating the remaining unreacted potassium ferricyanide solution in the titration system with a cobalt standard solution until the jump point is reached;

[0044] The cobalt content in the sample was calculated using the following formula: Co% = {[ρ(V1×K-V2)×n] / [m÷(1-w 灼失量 %)]}×100%;

[0045] Wherein, ρ is the concentration of the cobalt standard solution, in g / mL;

[0046] V1 is the total volume of potassium ferricyanide solution added, in mL;

[0047] K is the ratio of the volume of the cobalt standard solution required to titrate the potassium ferricyanide solution of V1 to V1;

[0048] V2 is the volume of the cobalt standard solution consumed when titrating the remaining unreacted potassium ferricyanide solution, in mL;

[0049] n is the dilution factor;

[0050] m is the mass of the burned material used for digestion, in g;

[0051] w 灼失量 % is the mass percentage of the cobalt oxide sample lost during the ignition process.

[0052] In the present disclosure, the calcination temperature of the cobalt oxide sample is not less than 900°C, such as 900°C, 920°C, 950°C, 980°C or 1000°C. In some optional embodiments, the calcination temperature is 940°C-960°C. Accordingly, the calcination time can be 1h-2h, such as 1h, 1.5h or 2h. The above-mentioned calcination process is carried out under an inert gas atmosphere. For example, the inert gas atmosphere can be a nitrogen atmosphere, an argon atmosphere or a helium atmosphere. In some embodiments, the inert gas atmosphere adopts a nitrogen atmosphere, which is conducive to reducing the testing cost.

[0053] Under the above temperature and time conditions, the cobalt trioxide in the cobalt trioxide sample can be completely reacted into cobaltous oxide. Moreover, the entire calcination process is carried out under inert atmosphere conditions, which helps to prevent the cobaltous oxide generated by calcination from being converted back into cobalt trioxide.

[0054] In some embodiments, the calcination can be performed in a tube furnace. Specifically, the cobalt trioxide sample can be placed in a porcelain boat, and then the porcelain boat can be placed in the tube furnace.

[0055] It should be noted that when the cobalt tetroxide sample is directly digested with hydrochloric acid or nitric acid, it cannot be completely digested; therefore, if it is to be completely digested, perchloric acid must be used, but perchloric acid is more dangerous, and perchloric acid will lose materials during the digestion and fuming process, resulting in deviations in the results. The present disclosure adopts a method of first burning at a temperature of not less than 900°C in an inert atmosphere (such as using a tubular furnace), which can avoid the use of perchloric acid and the results are more stable. Through the above-mentioned burning treatment, the cobalt tetroxide in the sample can be converted into cobaltous oxide that is easily soluble in hydrochloric acid, which can be completely digested by hydrochloric acid.

[0056] In the present disclosure, after calcination, the calcined material is first cooled to below 400°C before being digested with hydrochloric acid. For reference, the calcined material can be cooled to 200°C-220°C, such as 200°C, 205°C, 210°C, 215°C, or 220°C. This cooling process is also performed under an inert atmosphere. This treatment prevents the calcined material (primarily composed of cobaltous oxide) from reverting to cobalt tetroxide in air and at temperatures exceeding 400°C.

[0057] The cooled burned product was dried and weighed to calculate the loss on ignition. Here, "loss on ignition" refers to the difference in mass between the cobalt oxide sample and the burned product.

[0058] In the present disclosure, the digestion temperature can be 200° C. to 300° C., such as 200° C., 220° C., 250° C., 280° C., or 300° C. The digestion time can be 2 min to 3 min, such as 2 min, 2.5 min, or 3 min. 18 mL to 22 mL (such as 18 mL, 19 mL, 20 mL, 21 mL, or 22 mL) of hydrochloric acid can be used for every 1 g of the burned material.

[0059] In some embodiments, the digestion process comprises mixing the ignited material to be digested with hydrochloric acid in a container, heating on a hot plate until slightly boiling, then stopping heating after 2-3 minutes, and cooling to room temperature. In this method, the digestion temperature refers to the temperature of the hot plate, and the digestion time refers to the time the reaction continues after slightly boiling.

[0060] Through digestion, cobaltous oxide is completely reacted into cobalt chloride.

[0061] In some embodiments, the entire burnt material obtained from the aforementioned burning process can be directly digested. In other embodiments, only a portion of the burnt material can be digested, thereby reducing the amount of reagents used, lowering testing costs, and shortening testing time.

[0062] Similarly, in some embodiments, after digestion, the resulting digestate can be diluted to a volumetric flask to form a sample solution. During the titration process, a portion of the sample solution can be pipetted for titration. Accordingly, the ratio of the volume of the sample solution pipetted to the volume of the sample solution after dilution is the dilution factor in the calculation formula. In other embodiments, the entire digestate can be directly titrated, in which case the dilution factor is 1.

[0063] In the present disclosure, the potassium ferricyanide solution used in the titration process is a titrant. For reference, the concentration of the potassium ferricyanide solution can be 16 g / L-18 g / L, such as 16 g / L, 16.5 g / L, 17 g / L, 17.5 g / L or 18 g / L.

[0064] The corresponding reaction equations include: Co 2+ +[Fe(CN)6] 3- =Co 3+ +[Fe(CN)6] 4- .

[0065] It should be noted that cobalt oxide samples are often doped with other metal elements (such as Ni, Mn, or Cu). Conventional EDTA would react with these metal elements if used as a titrant. Using potassium ferrocyanide, however, avoids interference from other metals. Furthermore, the redox reaction of potassium ferrocyanide is more suitable for potentiometric titration than the complexation reaction of EDTA, resulting in a faster reaction rate.

[0066] The excess potassium ferricyanide solution and the digestion solution can be reacted under the condition of pH 9.8 to 10.0 (such as 9.8, 9.9 or 10.0). During the reaction of the excess potassium ferricyanide solution and the digestion solution, an ammonia-ammonium citrate mixture used as a buffer solution is also added. Exemplarily, the ammonia-ammonium citrate mixture can be prepared by ammonia and ammonium citrate in an amount ratio of 350 mL:48 g to 350 mL:52 g.

[0067] The temperature of the ammonia-ammonium citrate mixture used above is 3°C-5°C. By controlling the temperature of the ammonia-ammonium citrate mixture at 3°C-5°C, the 2+ In an ammonia solution, it is oxidized by oxygen in the air when the temperature is high.

[0068] In the present disclosure, the concentration of the cobalt standard solution may be 2.8 g / L-3.2 g / L, such as 2.8 g / L, 3.0 g / L or 3.2 g / L.

[0069] In the present disclosure, the titration mode used by the potentiometric titrator is MET mode. The signal drift of the potentiometric titration is set to 18mv / min-22mv / min, such as 18mv / min, 19mv / min, 20mv / min, 21mv / min, or 22mv / min. The volume increment of the potentiometric titration is set to 0.015mL-0.025mL, such as 0.015mL, 0.020mL, or 0.025mL. By adopting the signal drift and volume increment under the above conditions, it is beneficial to obtain more accurate results.

[0070] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0071] Example 1

[0072] This embodiment provides a method for determining the cobalt content in a cobalt oxide material, which comprises the following steps:

[0073] S1: Accurately weigh 10 g of the cobalt oxide sample to be tested into a constant weight porcelain boat.

[0074] S2: Take the sample hook and place the porcelain boat into a tube furnace. Burn it at 950℃ in a nitrogen atmosphere for 1 hour. Cool it to 200℃ in the nitrogen atmosphere and then take it out. Cool it to room temperature in a desiccator, weigh it, calculate the loss on ignition, and seal the burned sample in a plastic bag.

[0075] S3: Accurately weigh 1.0000±0.01g of the calcined sample into a 100mL beaker, add 20mL of (1+1) hydrochloric acid (i.e., a mixture of equal volumes of hydrochloric acid and water), heat to 200℃, maintain a slight boil for 3 minutes, remove and cool, and dilute to a 250mL volumetric flask.

[0076] S4: Add 5g of ammonium chloride (AR) to a 250mL clean beaker, accurately pipette 10mL of 17g / L potassium ferricyanide solution, and 80mL of ammonia-ammonium citrate mixture (ammonia and ammonium citrate are prepared at a ratio of 350mL:50g), accurately pipette the sample solution after it is adjusted to volume in a 5mL volumetric flask, and stir with a magnetic stirrer for 2 minutes; the pH value of the mixed system is 10.0.

[0077] S5: Set the relevant parameters of the potentiometric titrator (MET titration, signal drift of 20.0 mv / min, volume increment of 0.02 mL), titrate with cobalt standard solution (3 g / L) to the jump point, record the volume of cobalt standard consumed, and calculate the cobalt content in the sample according to the following formula: Co% = {[ρ(V1×K-V2)×n] / [m÷(1-w 灼失量 %)]}×100%;

[0078] Wherein, ρ is the concentration of the cobalt standard solution, in g / mL;

[0079] V1 is the total volume of potassium ferricyanide solution added, in mL;

[0080] K is the ratio of the volume of the cobalt standard solution required to titrate the potassium ferricyanide solution of V1 to V1;

[0081] V2 is the volume of the cobalt standard solution consumed when titrating the remaining unreacted potassium ferricyanide solution, in mL;

[0082] n is the dilution factor;

[0083] m is the mass of the burned material used for digestion, in g;

[0084] w 灼失量 % is the mass percentage of the cobalt oxide sample lost during the ignition process.

[0085] S6: Repeat the above steps S1 to S5 and take the average of the two test results.

[0086] The above S1 to S6 were tested every day and data was collected for 30 days. The results are shown in Table 1.

[0087] Table 1 Test results

[0088] As can be seen from Table 1, the test results obtained by the test method provided by the present disclosure have a range of only 0.18% within 30 days, indicating that the test method has good result accuracy and stability.

[0089] Example 2

[0090] This embodiment provides a method for determining the cobalt content in a cobalt oxide material, which comprises the following steps:

[0091] S1: Accurately weigh 10 g of the cobalt oxide sample to be tested into a constant weight porcelain boat.

[0092] S2: Take the sample hook and place the porcelain boat into a tube furnace. Burn it at 900℃ in a nitrogen atmosphere for 2 hours. Cool it to 250℃ in a helium atmosphere, then take it out and cool it to room temperature in a desiccator. Weigh it, calculate the loss on ignition, and seal the burned sample in a plastic bag.

[0093] S3: Accurately weigh 1.0000±0.01g of the calcined sample into a 100mL beaker, add 18mL of (1+1) hydrochloric acid (i.e., a mixture of equal volumes of hydrochloric acid and water), heat to 250℃, maintain a slight boil for 2.5min, remove and cool, and dilute to a 250mL volumetric flask.

[0094] S4: Add ammonium chloride (AR) to a 250-mL clean beaker, accurately pipette 10 mL of 16 g / L potassium ferricyanide solution, and 80 mL of ammonia-ammonium citrate mixture (ammonia and ammonium citrate prepared at a ratio of 350 mL:48 g), accurately pipette the sample solution that has been fixed to volume in a 5-mL volumetric flask, and stir with a magnetic stirrer for 2 minutes; the pH value of the mixed system is 9.8.

[0095] S5: Set the relevant parameters of the potentiometric titrator (MET titration, signal drift of 18.0 mv / min, volume increment of 0.015 mL), titrate with a cobalt standard solution (2.8 g / L) to the break point, and record the volume of cobalt standard consumed. The calculation formula is the same as in Example 1.

[0096] S6: Repeat the above steps S1 to S5 and take the average of the two test results.

[0097] The above S1 to S6 were tested every day and data was collected for 30 days. The range of the test results within 30 days was only less than 0.2%, indicating that the test method has good result accuracy and stability.

[0098] Table 2 Test results

[0099] As can be seen from Table 2, the test results obtained by the test method provided by the present disclosure have a range of only 0.20% within 30 days, indicating that the test method has good result accuracy and stability.

[0100] Example 3

[0101] This embodiment provides a method for determining the cobalt content in a cobalt oxide material, which comprises the following steps:

[0102] S1: Accurately weigh 10 g of the cobalt oxide sample to be tested into a constant weight porcelain boat.

[0103] S2: Take the sample hook and place the porcelain boat into the tube furnace. Burn it at 960℃ in nitrogen atmosphere for 1.5h. Cool it to 180℃ in argon atmosphere, take it out, cool it to room temperature in a desiccator, weigh it, calculate the loss on ignition, and seal the burned sample in a plastic bag.

[0104] S3: Accurately weigh 1.0000±0.01g of the calcined sample into a 100mL beaker, add 22mL of (1+1) hydrochloric acid (i.e., a mixture of equal volumes of hydrochloric acid and water), heat to 300℃, maintain a slight boil for 2min, remove and cool, and dilute to a 250mL volumetric flask.

[0105] S4: Add ammonium chloride (AR) to a 250-mL clean beaker, accurately pipette 10 mL of 18 g / L potassium ferricyanide solution, and 80 mL of ammonia-ammonium citrate mixture (ammonia and ammonium citrate prepared at a ratio of 350 mL:52 g), accurately pipette the sample solution that has been adjusted to volume in a 5-mL volumetric flask, and stir with a magnetic stirrer for 2 minutes; the pH value of the mixed system is 10.0.

[0106] S5: Set the relevant parameters of the potentiometric titrator (MET titration, signal drift of 22.0 mv / min, volume increment of 0.025 mL), titrate with a cobalt standard solution (3.2 g / L) to the break point, and record the volume of cobalt standard consumed. The calculation formula is the same as in Example 1.

[0107] S6: Repeat the above steps S1 to S5 and take the average of the two test results.

[0108] The above S1 to S6 were tested every day and data was collected for 30 days. The range of the test results within 30 days was only less than 0.2%, indicating that the test method has good result accuracy and stability.

[0109] Table 3 Test results

[0110] As can be seen from Table 3, the test results obtained by the test method provided by the present disclosure have a range of only 0.20% within 30 days, indicating that the test method has good result accuracy and stability.

[0111] Comparative Example 1

[0112] The cobalt tetroxide sample identical to that in Example 1 was measured using the EDTA potentiometric titration method.

[0113] The specific operations are as follows:

[0114] Weigh 1g of cobalt tetroxide sample, add 15mL of perchloric acid to digest until white smoke is separated, cool slightly, add 20mL of (1+1) hydrochloric acid solution and continue digesting until the solution is clear, cool and dilute to 250mL; pipette 10mL of sample solution into a 100mL beaker, add a magnet, add 20mL of ammonium acetate-ammonia buffer and 1mL of Cu-EDTA indicator in sequence, place on the titration stand, and titrate with 0.3mol / L EDTA standard titrant to the jump point, record the volume of EDTA standard titrant consumed, and calculate the cobalt content in the sample solution.

[0115] The calculation formula is as follows: Co% = (C × V × 0.05893 × n) / m × 100%;

[0116] Wherein, C is the concentration of EDTA standard titration solution, in mol / L;

[0117] V is the volume of EDTA standard titration solution consumed, in mL;

[0118] n is the dilution factor;

[0119] m is the mass of the sample weighed, in g.

[0120] Repeat the above steps and take the average of the two test results.

[0121] The above operation was followed every day to perform the test and collect data for 30 days. The results are shown in Table 4.

[0122] Table 4 Test results

[0123] As can be seen from Table 4, the test results obtained by the above EDTA potentiometric titration test method have a range of up to 0.81% within 30 days, indicating that the test results of this method are less stable.

[0124] Comparative Example 2

[0125] The same cobalt tetroxide sample as in Example 1 was measured using potassium ferrocyanide potentiometric titration.

[0126] The specific operations are as follows:

[0127] Weigh 1g of cobalt tetroxide sample and add 15mL of perchloric acid to digest until white smoke forms. After cooling slightly, add 20mL of (1+1) hydrochloric acid solution and continue digesting until the solution is clear. After cooling, adjust the volume to 250mL. In a clean 250mL beaker, add 5g of ammonium chloride (AR), accurately pipette 10mL of potassium ferricyanide solution (same as in Example 1), and 80mL of ammonia-ammonium citrate mixture (same as in Example 1). Accurately pipette 5mL of the adjusted sample solution, stir with a magnetic stirrer for 3 minutes, place on a titration stand, and titrate with a cobalt standard solution (2g / L) to the tipping point. Record the volume of cobalt standard consumed to calculate the cobalt content in the sample solution.

[0128] The calculation formula is as follows: Co% = {[ρ(V1×K-V2)×n] / m}×100%;

[0129] Wherein, ρ is the concentration of the cobalt standard solution, in g / mL;

[0130] V1 is the total volume of potassium ferricyanide solution added, in mL;

[0131] K is the ratio of the volume of the cobalt standard solution required to titrate the potassium ferricyanide solution of V1 to V1;

[0132] V2 is the volume of the cobalt standard solution consumed when titrating the remaining unreacted potassium ferricyanide solution, in mL;

[0133] n is the dilution factor;

[0134] m is the mass of the burned material used for digestion, in g;

[0135] Repeat the above steps and take the average of the two test results.

[0136] The test was performed according to the above operation every day, and data was collected for 30 days. The results are shown in Table 5.

[0137] Table 5 Test results

[0138] As can be seen from Table 5, the test results obtained by the potassium ferrocyanide potentiometric titration test method have a range of up to 0.50% within 30 days, indicating that the test results of this method have poor stability.

[0139] Comparative Example 3

[0140] The difference between this comparative example and Example 1 is that the product was not cooled in a nitrogen atmosphere after calcination, and the other operations were the same as those in Example 1.

[0141] The test results obtained in this comparative example fluctuate greatly, indicating that this method cannot obtain stable test results.

[0142] Comparative Example 4

[0143] The difference between this comparative example and Example 1 is that the temperature of the ammonia water-ammonium citrate mixture used in the titration process is room temperature, and the other operations are the same as those in Example 1.

[0144] The test results of this comparative example are shown in Table 6.

[0145] Table 6 Test results

[0146] As can be seen from Table 6, although the range of the test results obtained by the above method within 30 days is less than 0.5%, it is still higher than 0.20%, indicating that the stability of the test results of this method cannot meet the requirements.

[0147] Comparative Example 5

[0148] The difference between this comparative example and Example 1 is that the potentiometric titration mode adopts the DET mode, and the other operations are the same as those in Example 1.

[0149] The test results of this comparative example are shown in Table 7.

[0150] Table 7 Test results

[0151] As can be seen from Table 7, although the range of the test results obtained by the above method within 30 days is less than 0.5%, it is still higher than 0.20%, indicating that the stability of the test results of this method cannot meet the requirements.

[0152] Comparative Example 6

[0153] The difference between this comparative example and Example 1 is that the volume increment in the potentiometric titration mode is 0.1 mL, and the other operations are the same as those in Example 1.

[0154] The test results of this comparative example are shown in Table 8.

[0155] Table 8 Test results

[0156] As can be seen from Table 8, the range of the test results obtained by the above method within 30 days is 0.39, indicating that the stability of the test results of this method cannot meet the requirements.

[0157] In summary, the method for determining cobalt in cobalt tetroxide provided by the present disclosure is simple and safe to operate. It not only avoids interference from possible adhering water in the sample, but also avoids the loss that may be caused by the perchloric acid fuming process in the commonly used method. In addition, it avoids the error interference caused by titration in the DET mode, and the obtained test data is highly stable and accurate. Industrial Applicability

[0158] The method for determining cobalt in cobalt tetroxide materials provided by the present disclosure is simple to operate, has high determination accuracy, and good stability, and has high promotion and application value. It is particularly suitable for the evaluation, determination, and detection of cobalt in cobalt tetroxide materials in the battery industry, and is beneficial to the battery industry in controlling the quality of cobalt tetroxide materials.

Claims

1. A method for determining the cobalt content in cobalt tetroxide material, characterized in that, it includes the following steps: Burn the cobalt tetroxide sample under an inert atmosphere to completely react cobalt tetroxide into cobaltous oxide; digest the calcined product obtained by calcination with hydrochloric acid to obtain a digestion solution; Use potassium ferricyanide solution as a titrant to perform potentiometric titration on the digestion solution; Among them, the titration process includes: reacting an excessive amount of potassium ferricyanide solution with the digestion solution to completely react divalent cobalt in the digestion solution into trivalent cobalt; then titrating the remaining unreacted potassium ferricyanide solution in the titration system with a cobalt standard solution until the jump point; Calculate the cobalt content in the sample according to the following formula: Co% = {[ρ(V 1 ×K - V 2 )×n] / [m÷(1 - w 灼失量 %)]}×100%; Among them, ρ is the concentration of the cobalt standard solution, with the unit of g / mL; V 1 is the total volume of the potassium ferricyanide solution added, in mL; K is the ratio of the volume of cobalt standard solution required to titrate the potassium ferricyanide solution of V 1 to V 1 ; V 2 is the volume of the cobalt standard solution consumed when titrating the remaining unreacted potassium ferricyanide solution, with the unit of mL; n is the dilution factor; m is the mass of the calcined product used for digestion, with the unit of g; w 灼失量 % is the mass percentage of the mass lost during the burning process in the mass of the cobalt tetroxide sample.

2. The determination method according to claim 1, characterized in that, the calcination temperature is not lower than 900 °C.

3. The determination method according to claim 2, characterized in that, the calcination temperature is 940 °C - 960 °C.

4. The determination method according to any one of claims 1 - 3, characterized in that, the calcination time is 1 h - 2 h.

5. The determination method according to any one of claims 1 - 4, characterized in that, the calcination is carried out under an inert gas atmosphere.

6. The determination method according to claim 5, characterized in that, the calcination is carried out under a nitrogen atmosphere.

7. The determination method according to any one of claims 1 - 6, characterized in that, after calcination, the calcined product is cooled to below 400 °C before being digested with hydrochloric acid.

8. The determination method according to claim 7, characterized in that, the calcined product is cooled to 200 °C - 220 °C.

9. The determination method according to any one of claims 1 - 8, characterized in that, the digestion temperature is 200 °C - 300 °C, and the digestion time is 2 min - 3 min.

10. The determination method according to any one of claims 1 - 9, characterized in that, for every 1 g of the calcined product, 18 mL - 22 mL of the hydrochloric acid is used.

11. The determination method according to any one of claims 1 - 10, characterized in that, the excessive potassium ferricyanide solution reacts with the digestion solution under the condition of a pH value of 9.8 to 10.

0.

12. The determination method according to any one of claims 1 - 11, characterized in that, the concentration of the potassium ferricyanide solution is 16 g / L - 18 g / L.

13. The determination method according to any one of claims 1 - 12, characterized in that, during the reaction of the excessive potassium ferricyanide solution with the digestion solution, an ammonia - ammonium citrate mixture is also added.

14. The determination method according to claim 13, characterized in that, in the ammonia - ammonium citrate mixture, the dosage ratio of ammonia to ammonium citrate is 350 mL:48 g to 350 mL:52 g.

15. The determination method according to claim 13 or 14, characterized in that, the temperature of the used ammonia - ammonium citrate mixture is 3 °C - 5 °C.

16. The determination method according to any one of claims 1 - 15, characterized in that, The concentration of the cobalt standard solution is 2.8 g / L - 3.2 g / L.

17. According to the determination method described in any one of claims 1-16, characterized in that the potentiometric titration mode is the MET mode.

18. According to the determination method described in any one of claims 1-17, characterized in that the signal drift of the potentiometric titration is 18 mv / min - 22 mv / min.

19. According to the determination method described in any one of claims 1-18, characterized in that the volume increment of the potentiometric titration is 0.015 mL - 0.025 mL.

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