Metal developing solution as well as preparation method and application thereof

Abstract

The invention relates to the field of material detection, in particular to a metal developing solution and a preparation method and application thereof. The metal developing solution comprises a polyphenol compound, a solvent and a buffer solution, natural polyphenol compounds such as tannic acid are adopted as the color developing agent, so that the color developing agent has good water solubility and no toxicity, and the problems of safety and environmental protection of a traditional dicyclohexanone oxalyl dihydrazone color developing agent are solved; the selected color developing agent does not develop color on cobalt and nickel in a normal state, so that interference of Co < 2 + > and Ni < 2 + > on experimental results is effectively avoided; a plurality of ortho-phenolic hydroxyl structures of the polyphenol compound can be used as multidentate coordination to generate coordination chelation with copper ions, iron ions and the like to form a complex.

Description

Technical Field

[0001] The present invention relates to the field of material detection, and particularly to a metal chromogenic solution, a preparation method thereof, and an application thereof. Background Art

[0002] The inspection standards for various raw materials of new energy batteries are the basic considerations for the battery energy storage performance and safety performance. When impurity metal elements such as iron, copper, cobalt, and nickel are present, during the charge and discharge process, when the voltage reaches the redox potential of the impurity element, it may be reduced to a metal simple substance and deposited on the negative electrode, resulting in large self-discharge of the battery, attenuation of electrical performance, and continuous accumulation with the increase of the number of cycles, eventually piercing the diaphragm and triggering a safety accident. Among them, iron impurities often exist in the form of iron phosphide and show weak magnetism; copper impurities are non-magnetic themselves, so it is very difficult to remove these two impurity elements by magnetic adsorption. Therefore, the accuracy of qualitative and quantitative tests for copper and iron impurity elements is very important.

[0003] In the currently published copper chromogenic test methods, the selected chromogenic reagent is dicyclohexanone oxalyl dihydrazone, and a buffer solution is used as an auxiliary to complete the detection. However, dicyclohexanone oxalyl dihydrazone is toxic, insoluble in water, irritating, and not environmentally friendly; and the chromogenic agent is easily interfered by other impurity metal elements. Therefore, it is very necessary to develop a safer, more environmentally friendly, and selective chromogenic reagent and chromogenic method. Summary of the Invention

[0004] The purpose of the present invention is to provide a metal chromogenic solution, a preparation method thereof, and an application thereof in view of the deficiencies in the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] The first aspect of the present invention is to provide a metal chromogenic solution, comprising: a polyphenolic compound, a solvent, and a buffer solution.

[0007] Preferably, the polyphenolic compound comprises at least one of tannic acid, gallic acid, procyanidin, caffeic acid, epigallocatechin gallate, and quercetin.

[0008] Preferably, the solvent comprises at least one of water and alcohol.

[0009] Preferably, the buffer solution comprises at least one of acetic acid-sodium acetate, ammonia water-ammonium chloride, and sodium acetate-ammonium acetate.

[0010] Preferably, the volume ratio of the mixture of the polyphenolic compound and the solvent to the buffer solution is (0.8 - 3):1.

[0011] The second aspect of the present invention is to provide a method for preparing the above metal chromogenic solution, and the steps include: weighing the polyphenolic compound, dissolving it in the solvent, and then mixing it with the buffer solution to obtain the metal chromogenic solution.

[0012] The third aspect of the present invention is to provide an application of the above metal chromogenic solution or the metal chromogenic solution prepared by the above preparation method in the detection of metal elements in batteries, and the steps include:

[0013] S1. Place the powder material to be tested in a homogenizer, perform jar milling, filter and collect the filtrate, prepare the filtrate into a solution to be determined, and perform suction filtration on the solution to be determined to obtain the analyte;

[0014] S2. Drop the metal chromogenic solution onto the filter membrane retaining the analyte, uniformly moisten the filter membrane, and let it stand for a color reaction;

[0015] S3. After the reaction, observe the solubility and color change of the complex to qualitatively analyze the metal elements in the battery raw materials.

[0016] Preferably, the steps further include:

[0017] S4. If multiple colors are observed in step S3, adjust the pH of the metal chromogenic solution according to the color, and repeat steps S2 - S3 to verify other metal elements.

[0018] Preferably, in step S1, the time of the jar milling treatment is 15 - 30 min.

[0019] Preferably, in step S2, the time of the color reaction is 10 - 35 min.

[0020] Preferably, in step S2, the filter membrane is an acid - and alkali - resistant filter membrane.

[0021] Preferably, the metal elements include: Cu 2+ 、Fe 2+ / 3+ 、Zn 2+ 、Al 3+ 。

[0022] The present invention adopts the above technical solutions, and compared with the prior art, has the following technical effects:

[0023] (1) The present invention uses natural polyphenolic compounds such as tannic acid as chromogenic agents, which have good water solubility and no toxicity, making up for the safety and environmental protection problems of traditional chromogenic agents such as dicyclohexanone oxalyl dihydrazone;

[0024] (2) The chromogenic agent selected in the present invention does not show color to cobalt and nickel under normal conditions, effectively avoiding the interference of Co 2+ 、Ni 2+ on the experimental results;

[0025] (3) The soluble metal complex formed by the method of the present invention under certain test conditions can adjust the solubility of the complex by adding a chromogenic solution or buffer solution to adjust the acidity and alkalinity, realizing the qualitative test of various metal ions; the multiple ortho-phenolic hydroxyl structures of polyphenolic compounds can act as multidentate ligands, coordinating and chelating with metal ions such as copper ions and iron ions to form complexes. Among them, the pH value of the solution significantly affects the reaction direction and the state of the complex. Under acidic conditions, the phenolic hydroxyl groups are protonated, the coordination ability is weakened, and monodentate or bidentate complexes are formed, with a relatively light color change; under neutral and alkaline conditions, the phenolic hydroxyl groups dissociate, the coordination ability is enhanced to form multidentate chelates, and quinone substances are generated with the increase of pH, and the color deepens. Detailed implementation manners

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0028] The present invention will be further described below in conjunction with specific embodiments, but it is not limited to the present invention.

[0029] Example 1

[0030] This example provides a preparation method and application of a metal chromogenic solution. The steps include:

[0031] (1) Preparation method of the chromogenic solution: Weigh 0.5 g of tannic acid and add it to 500 mL of ultrapure water, stir for 20 min and ultrasonicate for 10 min to mix the solution evenly to obtain solution A. Weigh 10.0 g of sodium acetate and dissolve it in 800 mL of ultrapure water. After stirring and mixing evenly, measure 1.52 mL of acetic acid and add it to the above solution and stir evenly to obtain buffer solution B. According to the dosage of the test sample, use a pipette to respectively suck 5 mL of solution A and solution B and place them in a 25 mL small beaker, mix them in a volume ratio of 1:1, and ultrasonicate for 10 min to mix evenly to obtain a chromogenic solution with a pH of 7.

[0032] (2) Pretreatment of the battery material analyte: A series of pretreatments were carried out on 1 kg of lithium iron phosphate cathode material to collect the analyte solution. One-third of the volume of the analyte solution was measured and filtered by suction. Then the filter membrane was transferred to the stage of the test microscope, and 0.5 mL of the chromogenic solution was pipetted onto the filter membrane, evenly wetting the entire filter membrane without excess. After standing for 20 min until the chromogenic reaction ended, the color change was observed using a microscope.

[0033] If dark green is observed, it indicates the presence of copper ions in the battery material analyte.

[0034] If in addition to the dark green complex, blue-black is also observed, it indicates that iron ions may also be present in the battery material. Adjust the pH value of the metal chromogenic solution to 4 and observe the color change. If a blue-black complex continues to appear, it indicates that iron ions do exist in the battery material. If while the blue-black increases, yellowish-brown also appears, it indicates that aluminum ions are also present in the battery material.

[0035] If in addition to dark green, light yellow is also observed, it indicates that zinc ions may also be present in the battery material. Adjust the pH value of the metal chromogenic solution to 9 and observe the color change. If light yellow continues to appear, it indicates that zinc ions do exist in the battery material.

[0036] The corresponding pH values and colors of different polyphenolic compounds are shown in Table 1;

[0037] Table 1

[0038]

[0039] Example 2

[0040] This example provides another preparation method and application of a metal chromogenic solution. The steps include:

[0041] (1) Preparation method of the chromogenic solution: Weigh 0.5 g of gallic acid and add it to 500 mL of ultrapure water, stir for 20 min and sonicate for 10 min to mix the solution evenly to obtain solution A. Weigh 5.25 g of ammonium chloride and dissolve it in 800 mL of ultrapure water, stir and mix evenly, then measure 0.12 mL of ammonia water and add it to the above solution and stir evenly to obtain buffer solution B. According to the dosage of the test sample, use a pipette to respectively pipette 5 mL of solution A and solution B into a 25 mL small beaker, mix them in a volume ratio of 1:1, and sonicate for 10 min to mix evenly to obtain a weakly alkaline chromogenic solution.

[0042] (2) Pretreatment of the battery material analyte: A series of pretreatments were carried out on 1 kg of lithium iron phosphate cathode material to collect the analyte solution. One-third of the volume of the analyte solution was measured and filtered by suction. Then, the filter membrane was transferred to the stage of the test microscope, and a pipette was used to aspirate 0.5 mL of the chromogenic solution and add it to the filter membrane, evenly wetting the entire filter membrane without overdosage. After standing for 20 min until the chromogenic reaction ended, the color change was observed using a microscope. If blue-green color was observed, it indicated the presence of copper ions in the battery material analyte.

[0043] Example 3

[0044] This example provides another method for preparing and applying a metal chromogenic solution, and the steps include:

[0045] (1) Method for preparing the chromogenic solution: Weigh 0.5 g of procyanidin and add it to 500 mL of ultrapure water, stir for 20 min and sonicate for 10 min to make the solution mix evenly to obtain solution A. Weigh 5.03 g of ammonium chloride and dissolve it in 800 mL of ultrapure water. After stirring and mixing evenly, measure 0.38 mL of ammonia water and add it to the above solution and stir evenly to obtain buffer solution B. According to the dosage of the test sample, use a pipette to aspirate 5 mL of solution A and solution B respectively and place them in a 25 mL small beaker, mix them in a volume ratio of 1:1, and sonicate for 10 min to mix evenly to obtain a weakly alkaline chromogenic solution.

[0046] (2) Pretreatment of the battery material analyte: A series of pretreatments were carried out on 1 kg of lithium iron phosphate cathode material to collect the analyte solution. One-third of the volume of the analyte solution was measured and filtered by suction. Then, the filter membrane was transferred to the stage of the test microscope, and a pipette was used to aspirate 0.5 mL of the chromogenic solution and add it to the filter membrane, evenly wetting the entire filter membrane without overdosage. After standing for 20 min until the chromogenic reaction ended, the color change was observed using a microscope. If purple complexes were observed, it indicated the presence of copper ions in the battery material analyte.

[0047] Comparative Example 1

[0048] Adjust the pH of the metal chromogenic solution to weakly alkaline, and the rest are the same as in Example 1. The observed color was dark green. Although it could also show color, it was confused with the color of the battery material, and it was impossible to clearly distinguish whether there were copper ions in the battery material.

[0049] Comparative Example 2

[0050] Adjust the pH of the metal chromogenic solution to acidic, and the rest are the same as in Example 3. The observed color was grayish brown. Although it could also show color, it was confused with the color of the battery material, and it was impossible to clearly distinguish whether there were copper ions in the battery material.

[0051] When the metal color-developing solution of Examples 1-3 is used to detect copper ions in battery materials, the color change is obvious, showing a good color-developing effect. Comparing Comparative Example 1 with Example 1 and Comparative Example 2 with Example 3, the color is confused with the battery materials, indicating that the pH of the metal color-developing solution will also have a certain impact on color development. It should be noted that the metal color-developing solution described in the present invention is not limited to detecting metal elements in battery materials. Those skilled in the art can select appropriate polyphenolic compounds to prepare metal color-developing solutions for detecting metal elements in other materials.

[0052] The above are only the preferred embodiments of the present invention, and do not limit the implementation modes and protection scope of the present invention accordingly. For those skilled in the art, it should be able to realize that the solutions obtained by equivalent substitution and obvious changes made by using the content of the specification of the present invention should all be included in the protection scope of the present invention.

Claims

1. A metal color-developing solution, characterized in that, Comprising: Polyphenolic compounds, a solvent, and a buffer solution.

2. The metal color developing solution according to claim 1, characterized in that, The polyphenolic compounds include at least one of tannic acid, gallic acid, proanthocyanidins, caffeic acid, epigallocatechin gallate, and quercetin.

3. The metal color-developing solution according to claim 1, wherein, The solvent includes at least one of water and alcohol.

4. The metal color-developing solution according to claim 1, characterized in that, The buffer solution includes at least one of acetic acid-sodium acetate, ammonia-ammonium chloride, and sodium acetate-ammonium acetate.

5. The metal color developing solution according to claim 1, characterized in that, The volume ratio of the mixture of the polyphenolic compounds and the solvent to the buffer solution is (0.8 - 3):

1.

6. A method for preparing the metal color-developing solution according to any one of claims 1-5, characterized in that, The steps include: Weigh the polyphenolic compounds, dissolve them in the solvent, and then mix with the buffer solution to obtain the metal colorimetric solution.

7. Use of the metal color developing solution according to any one of claims 1-5 or the metal color developing solution prepared by the preparation method according to claim 6 in the detection of metal elements in battery raw materials, characterized in that the steps Comprising: S1. Place the powder material to be tested in a homogenization tank, perform pot milling treatment, filter and collect the filtrate, prepare the filtrate into a solution with a to-be-determined volume, and perform suction filtration on the solution with the to-be-determined volume to obtain the analyte; S2. Drop the metal colorimetric solution onto the filter membrane retaining the analyte, uniformly moisten the filter membrane, and let it stand for a color reaction; S3. After the reaction ends, observe the solubility and color change of the complex to qualitatively analyze the metal elements in the battery raw materials.

8. The application according to claim 7, wherein The steps further include: S4. If multiple colors are observed in step S3, adjust the pH of the metal colorimetric solution according to the color, and repeat steps S2 - S3 to verify other metal elements.

9. The application according to claim 7, characterized in that, In step S2, the time for the color reaction is 10 - 35 min.

10. The application according to claim 7, wherein The metallic elements include: Cu 2+ , Fe 2+ / 3+ , Zn 2+ , Al 3+ .

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