Component detection and sample preparation method of neodymium iron boron oil sludge

Abstract

The invention discloses a component detection and sample preparation method for neodymium iron boron oil sludge, and relates to the technical field of rare earth detection. The component detection sample preparation method comprises the following steps: carrying out extraction and oil removal treatment on a neodymium iron boron oil sludge sample to be detected by using an organic solvent, carrying out carbonization pretreatment, and carrying out first firing treatment to obtain a first firing treatment sample; grinding the sample subjected to the first-time burning treatment, and then carrying out second-time burning treatment to obtain a sample subjected to second-time burning treatment; and carrying out digestion treatment on the sample subjected to secondary firing treatment. By adopting the method, the content of the rare earth in the oil sludge can be accurately detected, so that a practical basis can be provided for the evaluation of the oil sludge and the recycling of the rare earth.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth detection, in particular to a sample preparation method for component detection of NdFeB sludge. Background Art

[0002] Neodymium iron boron (NdFeB) permanent magnets, due to their exceptional magnetic properties, are widely used in modern industry and high-tech fields. However, with the expansion of production scale and its widening application scope, the waste generated during NdFeB processing has become increasingly prominent. Magnetic sludge in cutting fluid, a major waste stream, not only poses a potential threat to the environment but also wastes significant amounts of rare earth resources. Rare earth elements are a key raw material in the NdFeB magnetic material manufacturing industry. During the production process, NdFeB permanent magnets are cut into various shapes and sizes to meet customer requirements, and this cutting process inevitably generates a large amount of magnetic sludge. After the cutting fluid is removed, the composition of the magnetic sludge is essentially the same as that of the NdFeB, making it highly valuable for recycling. Before recycling, the mixed magnetic sludge must be tested for composition and valuation. Therefore, efficiently recycling the rare earth elements in this magnetic sludge has become a pressing technical challenge.

[0003] Currently, a series of industry standards exist for NdFeB component testing, including "Analysis Methods for the Chemical Composition of NdFeB," such as XB / T617.2, XB / T617.3, and XB / T617.5. These standards provide important technical support for the quality control of NdFeB materials. Furthermore, research and patents have been developed for methods to determine the water content and total rare earth content of magnetic sludge in water-soluble cutting fluids. These findings provide viable solutions for recovering rare earth elements from water-soluble cutting fluids. However, compared to water-soluble cutting fluids, oil-based cutting fluids also play an important role in industrial production. While oil-based cutting fluids offer excellent lubrication and cooling properties, they present more complex waste disposal challenges. In particular, the sludge formed in oil-based cutting fluids, due to its high viscosity and tendency to agglomerate, presents significant challenges for subsequent sample preparation and component analysis. When attempting to digest these agglomerated sludge samples, the lumpy structure prevents complete dissolution, compromising the accuracy and reliability of instrument detection. The existence of this problem seriously hinders the effective recovery and reuse of rare earth components in oily cutting fluids.

[0004] In order to meet the above challenges, the present invention proposes a sample preparation method specifically for component detection of NdFeB sludge, which aims to improve the accuracy of rare earth content detection in sludge by optimizing the sample pretreatment process. Summary of the Invention

[0005] The present invention aims to provide a method for analyzing the composition of NdFeB sludge and preparing a sample to address the above-mentioned problems in the prior art. The method of the present invention can accurately detect the rare earth content in the sludge, thereby providing a practical basis for sludge valuation and rare earth recovery and reuse.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a method for preparing a sample for component detection of NdFeB sludge, comprising the following steps:

[0008] After the NdFeB oil sludge sample to be tested is subjected to extraction and deoiling treatment using an organic solvent, it is subjected to carbonization pretreatment and then to a first burning treatment to obtain a first burning treatment sample;

[0009] After grinding the first calcination-treated sample, performing a second calcination treatment to obtain a second calcination-treated sample;

[0010] The second burning sample is subjected to a digestion treatment.

[0011] Furthermore, the organic solvent is carbon tetrachloride or petroleum ether.

[0012] Furthermore, the carbonization pretreatment is performed by heating in a gradient temperature increase manner.

[0013] Furthermore, the gradient heating method is specifically as follows: first maintain the temperature at 250°C to 300°C for 1 hour, then heat up to 480°C to 520°C and maintain it for 1 hour.

[0014] Furthermore, the temperature of the first calcination treatment is 900°C to 950°C.

[0015] Furthermore, the temperature of the second calcination treatment is 900°C to 950°C.

[0016] Furthermore, a polyacid combination is used to perform the digestion treatment.

[0017] Furthermore, the polyacid combination includes aqua regia and hydrofluoric acid.

[0018] Furthermore, the digestion process adopts a gradient temperature increase program.

[0019] The present invention also provides a method for detecting the rare earth content of NdFeB sludge, comprising the following steps:

[0020] Perform solid content testing on the NdFeB sludge sample to be tested to obtain the solid content of the sludge;

[0021] After the NdFeB oil sludge sample to be tested is prepared using the above-mentioned component detection sample preparation method, the rare earth content of the dried oil sludge powder is detected;

[0022] The rare earth content in the NdFeB sludge sample to be tested is calculated according to the following formula: rare earth content in sludge = rare earth content of dried sludge powder × solid content of sludge.

[0023] The present invention discloses the following technical effects:

[0024] The present invention develops a sample preparation method for component detection of NdFeB sludge. The method uses physical extraction with an organic solvent to remove most of the grease in advance, reducing the subsequent burning load, avoiding the severe carbonization of the grease at high temperatures that can lead to increased sample agglomeration, and reducing smoke pollution during burning. A segmented temperature-controlled burning method and low-temperature carbonization pretreatment avoid the rapid volatilization of grease and sample splashing caused by traditional one-step high-temperature burning. The low-temperature carbonization stage also reduces volatile organic compound emissions, improving safety. Grinding ensures sufficient oxygen contact with the sample during the subsequent secondary burning, preventing residual oil in the center of the lumps. A burning-grinding-secondary burning method fully disperses the sludge sample and completely removes the oily cutting fluid, solving the agglomeration problem of the traditional single burning method. The final dried powdered sludge sample is digested using a combination of polyacids and microwave digestion to completely dissolve it, preventing low rare earth element detection caused by residual residue. The rare earth content of the sludge is determined by combining the solid content and the rare earth content test results of the dried sample. The method of the present invention can accurately detect the rare earth content in oil sludge, thereby providing a practical basis for oil sludge valuation and rare earth recovery and reuse. DETAILED DESCRIPTION

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0027] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0028] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0029] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0030] Example 1

[0031] A method for preparing samples for component detection of NdFeB sludge:

[0032] 1. Take a ceramic crucible and ignite it in a muffle furnace at 600°C ± 50°C for 2 hours to constant weight. Cool it to room temperature in a desiccator and weigh it. Repeat the ignition-cooling-weighing process until the difference between the two weights is ≤ 0.3 mg. Record the constant weight of the ceramic crucible as m1.

[0033] 2. After the oil sludge is thoroughly stirred with a glass rod, 5 g of sample is immediately placed in a ceramic crucible and the sample weight m2 is recorded.

[0034] 3. Add 10mL of carbon tetrachloride (or petroleum ether) to a ceramic crucible and stir with a glass rod to fully mix the oil sludge and solvent. Soak for 20 minutes (using the principle of like dissolves like). Tilt the crucible to pour out the waste liquid of the upper layer of dissolved grease. The remaining sample should be evaporated in a ventilated place until no obvious solvent is left.

[0035] 4. Place the crucible containing the oil sludge sample in a muffle furnace for the first calcination treatment. Heat it in a gradient heating manner: first hold it at 250°C for 1 hour (to slowly carbonize the residual oil and avoid boiling and splashing), then raise the temperature to 500°C for 1 hour (to further decompose organic carbon compounds), and finally raise it to 950°C for high-temperature calcination for 1 hour. After calcination, remove it and place it in a desiccator to cool to room temperature.

[0036] 5. Take out the dried oil mud blocks from the ceramic crucible and grind them thoroughly with a mortar.

[0037] 6. Place the crucible and the oil sludge powder in a muffle furnace for a second calcination at 950°C for 1 hour. After calcination, obtain dry oil sludge powder, remove it from the oven, and cool it to room temperature in a desiccator.

[0038] 7. After cooling after the second calcination treatment, use an analytical balance to weigh the crucible and sample mass (m3), and repeat the calcination-cooling-weighing process until the difference between two consecutive weighings is ≤0.3mg to ensure that the oily components are completely removed.

[0039] 8. Calculate the solid content of the sludge according to the following formula: (m3-m1) / m2.

[0040] 9. Weigh 0.1 g of the dried sludge powder obtained in step 6 and place it in a microwave digestion tube. Add 5 mL of aqua regia and 2 mL of hydrofluoric acid. Digest the mixture using a gradient temperature program (120°C / 5 min → 180°C / 10 min → 200°C / 15 min). Determine the rare earth content of the dried sludge powder using an inductively coupled plasma optical emission spectrometer. Calculate the rare earth content in the sludge using the following formula: Rare earth content in sludge = Rare earth content of dried sludge powder × solid content of sludge.

[0041] Example 2

[0042] A method for preparing samples for component detection of NdFeB sludge:

[0043] 1. Take a ceramic crucible and ignite it in a muffle furnace at 600°C ± 50°C for 2.5 hours to constant weight. Cool it to room temperature in a desiccator and weigh it. Repeat the ignition-cooling-weighing process until the difference between the two weights is ≤ 0.3 mg. Record the constant weight of the ceramic crucible as m1.

[0044] 2. After the oil sludge is thoroughly stirred with a glass rod, immediately take a 4g sample and place it in a ceramic crucible, and record the sample weight m2.

[0045] 3. Add 8 mL of carbon tetrachloride (or petroleum ether) to a ceramic crucible and stir with a glass rod to thoroughly mix the oil sludge and solvent. Soak for 18 minutes (using the principle of like dissolves like). Tilt the crucible to pour out the waste liquid containing the dissolved oil. Allow the remaining sample to evaporate in a well-ventilated area until no noticeable solvent is present.

[0046] 4. Place the crucible containing the oil sludge sample in a muffle furnace for the first calcination treatment. Heat it in a gradient heating manner: first maintain it at 280°C for 1 hour (to slowly carbonize the residual oil and avoid boiling and splashing), then increase the temperature to 480°C for 1 hour (to further decompose organic carbon compounds), and finally increase it to 900°C for high-temperature calcination for 1 hour. After calcination, remove it from the furnace and place it in a desiccator to cool to room temperature.

[0047] 5. Take out the dried oil mud blocks from the ceramic crucible and grind them thoroughly with a mortar.

[0048] 6. Place the crucible and the oil sludge powder in a muffle furnace for a second calcination treatment at 900°C for 1 hour. After calcination, the dry oil sludge powder is removed and placed in a desiccator to cool to room temperature.

[0049] 7. After cooling after the second calcination treatment, use an analytical balance to weigh the crucible and sample mass (m3), and repeat the calcination-cooling-weighing process until the difference between two consecutive weighings is ≤0.3mg to ensure that the oily components are completely removed.

[0050] 8. Calculate the solid content of the sludge according to the following formula: (m3-m1) / m2.

[0051] 9. Weigh 0.1 g of the dried sludge powder obtained in step 6 and place it in a microwave digestion tube. Add 5 mL of aqua regia and 2 mL of hydrofluoric acid. Digest the mixture using a gradient temperature program (120°C / 5 min → 180°C / 10 min → 200°C / 15 min). Determine the rare earth content of the dried sludge powder using an inductively coupled plasma optical emission spectrometer. Calculate the rare earth content in the sludge using the following formula: Rare earth content in sludge = Rare earth content of dried sludge powder × solid content of sludge.

[0052] Example 3

[0053] A method for preparing samples for component detection of NdFeB sludge:

[0054] 1. Take a ceramic crucible and ignite it in a muffle furnace at 600°C ± 50°C for 3 hours to constant weight. Cool it to room temperature in a desiccator and weigh it. Repeat the ignition-cooling-weighing process until the difference between the two weights is ≤ 0.3 mg. Record the constant weight of the ceramic crucible as m1.

[0055] 2. After the oil sludge is thoroughly stirred with a glass rod, immediately take a 3g sample and place it in a ceramic crucible, and record the sample weight m2.

[0056] 3. Add 5 mL of carbon tetrachloride (or petroleum ether) to a ceramic crucible and stir with a glass rod to fully mix the oil sludge and solvent. Soak for 15 minutes (using the principle of like dissolves like). Tilt the crucible to pour out the waste liquid of the upper layer of dissolved grease. The remaining sample should be evaporated in a ventilated place until no obvious solvent is left.

[0057] 4. Place the crucible containing the oil sludge sample in a muffle furnace for the first calcination treatment. Heat it in a gradient heating manner: first maintain it at 300°C for 1 hour (to slowly carbonize the residual oil and avoid boiling and splashing), then increase the temperature to 520°C for 1 hour (to further decompose organic carbon compounds), and finally increase the temperature to 920°C for high-temperature calcination for 1 hour. After calcination, remove it and place it in a desiccator to cool to room temperature.

[0058] 5. Take out the dried oil mud blocks from the ceramic crucible and grind them thoroughly with a mortar.

[0059] 6. Place the crucible and the oil sludge powder in a muffle furnace for a second calcination treatment at 920°C for 1 hour. After calcination, the dry oil sludge powder is removed and placed in a desiccator to cool to room temperature.

[0060] 7. After cooling after the second calcination treatment, use an analytical balance to weigh the crucible and sample mass (m3), and repeat the calcination-cooling-weighing process until the difference between two consecutive weighings is ≤0.3mg to ensure that the oily components are completely removed.

[0061] 8. Calculate the solid content of the sludge according to the following formula: (m3-m1) / m2.

[0062] 9. Weigh 0.1 g of the dried sludge powder obtained in step 6 and place it in a microwave digestion tube. Add 5 mL of aqua regia and 2 mL of hydrofluoric acid. Digest the mixture using a gradient temperature program (120°C / 5 min → 180°C / 10 min → 200°C / 15 min). Determine the rare earth content of the dried sludge powder using an inductively coupled plasma optical emission spectrometer. Calculate the rare earth content in the sludge using the following formula: Rare earth content in sludge = Rare earth content of dried sludge powder × solid content of sludge.

[0063] Comparative Example 1

[0064] A method for detecting the composition of NdFeB sludge:

[0065] 1. Take a ceramic crucible and ignite it in a muffle furnace at 600°C ± 50°C for 2 hours to constant weight. Cool it to room temperature in a desiccator and weigh it. Repeat the ignition-cooling-weighing process until the difference between the two weights is ≤ 0.3 mg. Record the constant weight of the ceramic crucible as m1.

[0066] 2. After the oil sludge is thoroughly stirred with a glass rod, 5 g of sample is immediately placed in a ceramic crucible and the sample weight m2 is recorded.

[0067] 3. Place the crucible containing the oil sludge sample in a muffle furnace and heat it to 950℃ for 1 hour. After calcination, remove the crucible and place it in a desiccator to cool to room temperature.

[0068] 4. Use an analytical balance to weigh the crucible and sample mass (m3), and repeat the ignition-cooling-weighing process until the difference between two consecutive weighings is ≤ 0.3 mg.

[0069] 5. Calculate the solid content of the sludge according to the following formula: (m3-m1) / m2.

[0070] 6. Weigh 0.1 g of the dried oil sludge obtained in step 4 and place it in a microwave digestion tube. Add 5 mL of aqua regia and 2 mL of hydrofluoric acid and digest using a gradient temperature program (120°C / 5 min → 180°C / 10 min → 200°C / 15 min). If the sample cannot be completely digested, allow it to settle and collect the supernatant for analysis using an inductively coupled plasma emission spectrometer to determine the rare earth content of the dried oil sludge. Calculate the rare earth content of the oil sludge using the following formula: Rare earth content in oil sludge = Rare earth content of dried oil sludge × solid content of oil sludge.

[0071] Example 4

[0072] The methods of Example 1 and Comparative Example 1 were used to test NdFeB sludge samples with known rare earth content, and the results are shown in Table 1. According to the test results, it can be seen that the method of the present invention significantly improves the accuracy of detecting the rare earth content of NdFeB sludge.

[0073] Table 1 Test results of rare earth content in NdFeB sludge samples

[0074]

[0075] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing samples for component detection of NdFeB sludge, characterized in that: The following steps are involved: After the NdFeB oil sludge sample to be tested is subjected to extraction and deoiling treatment using an organic solvent, it is subjected to carbonization pretreatment and then to a first burning treatment to obtain a first burning treatment sample; After grinding the first calcination-treated sample, performing a second calcination treatment to obtain a second calcination-treated sample; The second burning sample is subjected to a digestion treatment.

2. The component detection sample preparation method according to claim 1, characterized in that: The organic solvent is carbon tetrachloride or petroleum ether.

3. The component detection sample preparation method according to claim 1, characterized in that: The carbonization pretreatment is performed by heating in a gradient temperature increasing manner.

4. The component detection sample preparation method according to claim 3, characterized in that: The gradient heating method is specifically as follows: first, maintain the temperature at 250° C. to 300° C. for 1 hour, then heat the temperature to 480° C. to 520° C. and maintain the temperature for 1 hour.

5. The component detection sample preparation method according to claim 1, characterized in that: The temperature of the first calcination treatment is 900°C to 950°C.

6. The component detection sample preparation method according to claim 1, characterized in that: The temperature of the second calcination treatment is 900°C to 950°C.

7. The component detection sample preparation method according to claim 1, characterized in that: The digestion treatment is performed using a combination of polyacids.

8. The component detection sample preparation method according to claim 7, characterized in that: The polyacid combination includes aqua regia and hydrofluoric acid.

9. The component detection sample preparation method according to claim 1, characterized in that: The digestion process adopts a gradient temperature program.

10. A method for detecting rare earth content in NdFeB sludge, characterized in that: The following steps are involved: Perform solid content testing on the NdFeB sludge sample to be tested to obtain the solid content of the sludge; After preparing the NdFeB sludge sample to be tested by the component detection and sample preparation method according to any one of claims 1 to 9, the rare earth content of the dried sludge powder is detected; The rare earth content in the NdFeB sludge sample to be tested is calculated according to the following formula: rare earth content in sludge = rare earth content of dried sludge powder × solid content of sludge.

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