A rapid screening method for water-soluble fluorides in recycled soot for lithium-ion batteries

Abstract

A rapid screening method for water-soluble fluoride in recycled black powder for lithium-ion batteries includes the following steps: (1) Leaching of water-soluble fluoride ions: Mix black powder sample with deionized water at a certain solid-liquid ratio, stir and leach for a period of time at a set temperature, filter, and obtain leachate containing fluoride ions; (2) Test paper detection: Take 10 mL of the leachate obtained in step (1), immerse fluoride test paper in it, let it stand for 5 minutes and observe the color change of the test paper; (3) Result reporting: Compare the color of the test paper with the standard color chart of fluoride test paper to determine the concentration range of fluoride ions in the leachate; (4) Result judgment: Compare the color of the test paper with the 10 mg / L color scale diagram of the standard color chart of fluoride test paper to determine whether the sample is qualified. This method enables rapid semi-quantitative on-site screening of water-soluble fluoride ions in black powder.

Description

Technical Field

[0001] This invention relates to the field of fluoride ion detection technology, and in particular to a rapid screening method for water-soluble fluorides in recycled black powder used in lithium-ion batteries. Background Technology

[0002] Lithium-ion battery recycled black powder is a core recycled raw material in the battery recycling industry. The water-soluble fluoride content within the raw material directly determines the quality indicators of imported black powder and its deep processing. The current national standard GB / T45203 specifies that the fluoride ion detection method requires large-scale precision analytical instruments. The entire process, including sample pretreatment, isothermal reaction, and instrument reading, is cumbersome, with a single complete test taking more than 2 hours. This method can only be carried out in professional laboratories and cannot be applied to rapid screening scenarios at ports or recycling plants. In actual operations, if large quantities of recycled black powder raw materials are sent to standardized laboratory testing, it will significantly lengthen the raw material storage and turnover cycle and delay production scheduling. Existing simple testing methods cannot adapt to the interference of impurities in the black powder matrix, easily leading to distorted test results. The industry urgently needs a rapid on-site screening solution that does not require large instruments, is easy to operate, and has a short processing time. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention provides a rapid screening method for water-soluble fluorides in recycled black powder used in lithium-ion batteries.

[0004] The objective of this invention is achieved through the following technical solution: A rapid detection method for water-soluble fluoride ions in black powder based on fluoride test paper includes the following steps: (1) Water-soluble fluoride ion leaching: Mix black powder sample with deionized water at a certain solid-liquid ratio, stir and leach for a period of time at a set temperature, filter, and obtain fluoride ion-containing leachate; (2) Test paper detection: Take 10 mL of the leachate obtained in step (1), immerse the fluoride test paper in it, let it stand for 5 minutes and observe the color change of the test paper; (3) Result reporting: Compare the color of the test paper with the standard color chart of fluoride test paper to determine the concentration range of fluoride ions in the leachate; (4) Result judgment: Compare the color of the test paper with the 10 mg / L color scale diagram of the standard color chart of fluoride test paper to determine whether the sample is qualified.

[0005] In step (1), the solid-liquid ratio is 1:350 (g / mL) for type I black powder and 1:80 (g / mL) for type II black powder, and the leaching time is 1-5 minutes. In step (1), a 0.45μm filter membrane is used for filtration.

[0006] In step (3), the detection range of the fluoride test strip is 2mg / L-100mg / L, and the concentration segments are 0-2mg / L, 2mg / L-5mg / L, 5mg / L-10mg / L, 10mg / L-50mg / L, and 50mg / L-100mg / L, respectively. The test results are generated according to the above segments.

[0007] Step (4) The qualification judgment rule is that the test paper color development is below 10mg / L and the test paper color development is above 10mg / L and the qualification is not qualified. The unqualified sample is sent to the laboratory for verification according to the method specified in Appendix D of GB / T45203, so as to determine whether the content of water-soluble fluoride ions in black powder meets the import quality indicators, and realize the rapid semi-quantitative screening of water-soluble fluoride ions in black powder on site. Beneficial effects

[0008] 1. The entire process of pretreatment, test strip color development, and visual judgment of this invention takes only 10 to 30 minutes, compared with the national standard testing time of several hours. It is suitable for rapid initial screening of large quantities of raw materials in ports and factories, shortening the storage time of raw materials and significantly reducing the testing cycle.

[0009] 2. This invention requires no large-scale precision laboratory instruments such as ion chromatographs and spectrophotometers. Only simple consumables such as test strips, filter membranes, plastic cups, and syringes are needed. It is not limited by laboratory space and can be operated directly outdoors. The equipment cost is low, and it has a wide range of applications. By adapting differentiated solid-liquid extraction parameters to two types of recycled black powder, and using semi-quantitative colorimetric determination with fluoride test strips, the entire process takes only 10 to 30 minutes. No precision analytical equipment is required, and large-scale initial screening of raw materials can be completed on-site at ports and recycling plants. Unqualified samples can then be sent to a laboratory for precise retesting according to national standards, significantly improving the efficiency of raw material flow.

[0010] 3. This invention is specifically adapted to two types of recycled black powder: it differentiates the solid-liquid ratio of extraction for Type I and Type II black powder, takes into account the fluoride ion dissolution efficiency of both low-impurity and high-impurity raw materials, avoids the result of a single ratio leading to overly high or low test results, and has high screening accuracy.

[0011] 4. Raw materials that pass the initial screening on-site can be directly processed in the warehouse. Only unqualified samples are sent to the laboratory for retesting according to national standards, significantly reducing the number of samples required for laboratory testing and saving on testing manpower and reagent costs. Existing fluoride test strips are only used for routine water quality testing. This invention is the first to apply fluoride test strips with a differentiated extraction process to the screening of water-soluble fluoride in lithium-ion battery recycled black powder, opening up a new path for rapid on-site testing of battery recycling raw materials and filling a gap in industry applications. Attached Figure Description

[0012] Appendix Figure 1 These are the actual samples of the two groups of Class I black powder test strips of this invention. Figure 1 .

[0013] Appendix Figure 2 These are the actual samples of the two groups of Class I black powder test strips of this invention. Figure 2 .

[0014] Appendix Figure 3 The accompanying fluoride standard colorimetric chart is provided for this invention.

[0015] Appendix Figure 4 This is a photograph of the color development of the test strip for samples exceeding the standard according to the present invention. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: Example 1: A rapid screening method for water-soluble fluoride in recycled black powder for lithium-ion batteries includes the following steps: (1) Water-soluble fluoride ion leaching: Mix black powder sample with deionized water at a certain solid-liquid ratio, stir and leach for a period of time at a set temperature, filter, and obtain fluoride ion-containing leachate; (2) Test paper detection: Take 10 mL of the leachate obtained in step (1), immerse fluoride test paper in it, let it stand for 5 minutes and observe the color change of the test paper; (3) Result reporting: Compare the color of the test paper with the standard color chart of fluoride test paper to determine the concentration range of fluoride ions in the leachate; (4) Result judgment: Compare the color of the test paper with the 10 mg / L color scale diagram of the standard color chart of fluoride test paper to determine whether the sample is qualified.

[0017] In step (1), the solid-liquid ratio for Class I black powder is 1:350 (g / mL), and the solid-liquid ratio for Class II black powder is 1:80 (g / mL), with a leaching time of 1-5 minutes.

[0018] In step (1), a 0.45μm filter membrane is used for filtration.

[0019] In step (3), the detection range of the fluoride test strip is 2mg / L-100mg / L, and the concentration segments are 0-2mg / L, 2mg / L-5mg / L, 5mg / L-10mg / L, 10mg / L-50mg / L, and 50mg / L-100mg / L, respectively. The test results are generated according to the above segments.

[0020] Step (4) The qualification judgment rule is that the test paper color development is below 10mg / L and the test paper color development is above 10mg / L and the qualification is not qualified. The unqualified sample is sent to the laboratory for verification according to the method specified in Appendix D of GB / T45203, so as to determine whether the content of water-soluble fluoride ions in black powder meets the import quality indicators, and realize the rapid semi-quantitative screening of water-soluble fluoride ions in black powder on site.

[0021] The complete screening method of this invention includes water-soluble fluoride ion leaching, colorimetric detection with test strips, concentration-segmented reporting, and pass / fail determination. The water-soluble fluoride ion leaching process differentiates the solid-liquid ratio based on the type of recycled black powder. Type I black powder has low impurity content, using a solid-liquid ratio of 1:350 g / mL; Type II black powder has high impurity and soluble salt content, using a solid-liquid ratio of 1:80 g / mL. The corresponding mass of black powder is weighed and mixed with deionized water, stirred at room temperature for 1 to 5 minutes to ensure sufficient dissolution of water-soluble fluorides from the raw material. After stirring, filtration is performed using a 0.4 μm filter membrane to remove solid particles and colloidal impurities from the black powder, eliminating interference from the solid matrix on subsequent colorimetric detection with the test strips, and obtaining a clear fluoride-containing leachate.

[0022] In the colorimetric detection process, accurately measure 10 mL of the filtered leachate as the test sample, completely immerse the fluoride test strip in the leachate, and let it stand for 5 minutes to ensure sufficient colorimetric reaction. After standing, remove the test strip and observe the colorimetric area on the surface.

[0023] The concentration-segmented reporting process is equipped with a dedicated fluoride test strip standard colorimetric card. The effective detection range of the test strip covers 2 mg / L to 100 mg / L, divided into five concentration ranges: 0 to 2 mg / L, 2 to 5 mg / L, 5 to 10 mg / L, 10 to 50 mg / L, and 50 to 100 mg / L. The colorimetric test strip is visually compared with each color block on the colorimetric card, and the corresponding range is used as the fluoride ion concentration report result of the sample, realizing semi-quantitative graded screening.

[0024] The pass / fail determination process uses the 10mg / L color patch on the colorimetric card as the pass / fail dividing line. If the color of the test strip is lighter than that of the 10mg / L color patch, the water-soluble fluoride content of this batch of black powder is considered to be within the standard and meets the import quality requirements. If the color of the test strip is darker than that of the 10mg / L color patch, the sample is considered to be unqualified. This batch of samples is retained separately and sent to the laboratory for precise quantitative testing using the method specified in Appendix D of the national standard GB / T45203 to confirm the actual fluoride content.

[0025] The pass / fail determination process uses the 10mg / L color patch on the colorimetric card as the pass / fail dividing line. If the color of the test strip is lighter than that of the 10mg / L color patch, the water-soluble fluoride content of this batch of black powder is considered to be within the standard and meets the import quality requirements. If the color of the test strip is darker than that of the 10mg / L color patch, the sample is considered to be unqualified. This batch of samples is retained separately and sent to the laboratory for precise quantitative testing using the method specified in Appendix D of the national standard GB / T45203 to confirm the actual fluoride content.

[0026] Example 2: Class I Lithium-ion Regenerated Black Powder Rapid Screening 1. Sample pretreatment leaching: Weigh 1.00g of Class I secondary black powder into a wide-mouth plastic cup, add 350mL of deionized water and stir for 3 minutes to complete the fluoride ion dissolution; filter with a syringe and a 0.45μm filter membrane and collect the clear leachate.

[0027] 2. Test strip test: Draw 10 mL of filtrate into a reaction dish using a syringe, add 10 drops of the matching colorimetric reagent, and shake to mix well; after puncturing the center of the fluoride test strip, immerse it completely in the liquid and let it stand for 5 minutes.

[0028] 3. Concentration Comparison Report: Take out the test strip and visually compare it with the standard fluoride colorimetric card, and record the corresponding concentration range. Figure 1 The colorimetric analysis of the test strip for sample 1 in this invention matched the 0-2 mg / L range, and it was determined that no water-soluble fluoride was detected. Figure 2 The colorimetric range of sample 2 in this invention is matched to 5-10 mg / L.

[0029] 4. Acceptance Criteria: If the color of both samples is lighter than that of the 10mg / L standard color patch, the corresponding water-soluble fluoride mass fraction of the black powder is ≤0.40%, and the samples are deemed acceptable and do not need to be sent to the laboratory for retesting.

[0030] Attached image description: Figure 1 Appendix Figure 2 Images of the two sets of Type I black powder test strips are attached. Figure 3 The fluoride standard colorimetric card accompanying this invention is divided into seven standard colorimetric blocks of 0, 2, 5, 10, 20, 50, and 100 mg / L for visual classification and comparison.

[0031] Example 3: This invention provides a rapid screening method for Class II lithium-ion regenerated black powder. 1. Sample pretreatment leaching: Weigh 1.00g of Class II secondary black powder and place it in a wide-mouth plastic cup. Add 80mL of deionized water and stir for 4 minutes to fully dissolve the water-soluble fluoride inside. Filter through a 0.45μm filter membrane to remove solid impurities and collect the clear leachate.

[0032] 2. Test strip detection: Take 10 mL of filtrate and place it in a reaction dish. Add 10 drops of colorimetric reagent and shake well. After puncturing the fluoride test strip, immerse it in the liquid and let it stand for 5 minutes to complete the colorimetric reaction.

[0033] 3. Concentration comparison report: The colorimetric results of the test strips match the range of 10 to 50 mg / L. Figure 4 The sample results were 10 mg / L-20 mg / L.

[0034] 4. Acceptance Criteria: The color depth is deeper than the 10mg / L standard color patch. Figure 4 Sample results: greater than 10 mg / L, indicating that the water-soluble fluoride content of this batch of Class II black powder exceeded the standard, with a corresponding mass fraction ≥0.10%. The sample was sealed separately and transferred to the laboratory for precise retesting using the national standard method in Appendix D of GB / T45203 to confirm the actual fluoride content.

[0035] Attached image description: Figure 4This is a picture of the color development of the test strip for the sample exceeding the standard in this embodiment. It can be seen that the color depth is higher than that of the standard color block of 10mg / L.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A rapid screening method for water-soluble fluorides in recycled black powder for lithium-ion batteries, comprising the following steps: (1) Leaching of water-soluble fluoride ions: Mix black powder sample with deionized water at a certain solid-liquid ratio, stir and leach for a period of time at a set temperature, filter, and obtain leachate containing fluoride ions; (2) Test paper detection: Take 10 mL of the leachate obtained in step (1), immerse the fluoride test paper in it, let it stand for 5 minutes and observe the color change of the test paper; (3) Result report: Compare the color of the test paper with the standard color chart of the fluoride test paper to determine the concentration range of fluoride ions in the leachate; (4) Result judgment: Compare the color of the test paper with the 10 mg / L color scale diagram of the standard color chart of the fluoride test paper to determine whether the sample is qualified.

2. The rapid screening method for water-soluble fluorides in recycled black powder for lithium-ion batteries according to claim 1, characterized in that, In step (1), the solid-liquid ratio for Class I black powder is 1:350g / mL, and the solid-liquid ratio for Class II black powder is 1:80g / mL, with a leaching time of 1-5 minutes.

3. The rapid screening method for water-soluble fluorides in recycled black powder for lithium-ion batteries according to claim 2, wherein in step (1), a 0.45μm filter membrane is used for filtration.

4. The method for rapid screening of water-soluble fluorides in recycled black powder for lithium-ion batteries according to claim 3, characterized in that, In step (3), the detection range of the fluoride test strip is 2mg / L-100mg / L, and the concentration segments are 0-2mg / L, 2mg / L-5mg / L, 5mg / L-10mg / L, 10mg / L-50mg / L, and 50mg / L-100mg / L, respectively. The test results are generated according to the above segments.

5. The method for rapid screening of water-soluble fluorides in recycled black powder for lithium-ion batteries according to claim 3, characterized in that, Step (4) The qualification judgment rule is that the test paper color development is below 10mg / L and the test paper color development is above 10mg / L and the qualification is not qualified. The unqualified sample is sent to the laboratory for verification according to the method specified in Appendix D of GB / T45203, so as to determine whether the content of water-soluble fluoride ions in black powder meets the import quality indicators, and realize the rapid semi-quantitative screening of water-soluble fluoride ions in black powder on site.

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