Rare earth element detection method and application thereof

Abstract

The invention provides a rare earth element detection method and application thereof, and the method comprises the following steps: (1) mixing a to-be-detected sample with aqua regia to obtain a to-be-detected solution; (2) mixing and boiling a solution to be detected with hydrochloric acid, hydroxylamine hydrochloride and glass beads, then mixing with a buffer solution and phenanthroline, detecting absorbance, and calculating the content of iron ions; (3) taking the iron stock solution to prepare a background solution; (4) preparing a series of to-be-detected solutions from the to-be-detected solutions; and (5) carrying out absorbance detection on the series of to-be-detected solutions by taking the background solution as a detection background to obtain the content of the rare earth elements in the to-be-detected samples. According to the method provided by the invention, tedious experimental operations such as extraction, back extraction, matrix precipitation and the like are not needed, the interference of iron elements in the sample is eliminated, large errors cannot be generated on rare earth quantification, detection can be realized only by using a visible spectrophotometer, the method is convenient to popularize, and the method has important significance on production, recovery, research and development of neodymium iron boron.

Description

A method for detecting rare earth elements and its application Technical Field

[0001] This invention belongs to the field of elemental quantitative analysis technology, specifically relating to a method for detecting rare earth elements and its application. Background Technology

[0002] Rare earth elements are known as "industrial vitamins," and high-performance rare earth functional materials such as neodymium iron boron are listed as "key strategic materials" in the field of new materials. However, rare earth elements are non-renewable resources. Achieving centralized, systematic management and efficient recycling of rare earth renewable resources can further promote the high-quality development of the rare earth waste recycling industry.

[0003] Currently, NdFeB waste recycling processes mainly fall into two categories: pyrometallurgical and hydrometallurgical processes. Pyrometallurgical processes offer advantages such as shorter processing times and environmental friendliness, but compared to hydrometallurgical processes, they have smaller processing capacities, lower recovery rates, higher energy consumption, and relatively higher requirements for raw material quality. Hydrometallurgical processes are more adaptable to raw materials, achieving higher rare earth recovery rates and product purity, but the process is longer. Currently, hydrometallurgical processes are the primary method for NdFeB waste recycling.

[0004] The wet processing technology for NdFeB waste includes the total dissolution method, the hydrochloric acid preferential dissolution method, and the sulfuric acid double salt precipitation method. The basic process involves grinding and oxidizing the NdFeB waste to form rare earth elements, iron, and boron, which then oxidize to form roasted slag. In an acidic system, the rare earth elements in the NdFeB roasted slag are dissolved into the solution, while iron is dissolved as little as possible. The solution pH is then adjusted to remove impurities through hydrolysis. Next, solvent extraction is used to separate and extract the rare earth elements. Oxalic acid or carbonate precipitation is then used to obtain rare earth oxalate or rare earth carbonate. Finally, calcination yields a single rare earth oxide product. In the wet NdFeB recovery process, rare earth elements often coexist with iron in the solution; therefore, accurate and rapid determination of the rare earth content is crucial for both production and research.

[0005] Current methods for rare earth element determination mainly include GB / T 14635-2020, "Chemical Analysis Methods for Rare Earth Metals and Their Compounds: Determination of Total Rare Earth Content." This standard includes two methods: Method 1 (oxalate gravimetric method) and Method 2 (EDTA titration). Method 1 has a minimum detection limit of 10% for rare earth carbonates and requires precipitation of rare earth elements with oxalic acid followed by calcination of the precipitate at 950°C to form oxides. Method 2 has a minimum detection limit of 25% for rare earth hydroxides and requires a low iron ion content. This method also cannot meet the quantitative analysis requirements for rare earth elements in different processes of NdFeB waste recycling.

[0006] GB / T 223.49-94, "Chemical Analysis Methods for Iron and Steel Alloys: Extraction Components - Azochlorophosphine-mA Spectrophotometric Determination of Total Rare Earth Elements," describes a method where iron is separated by extraction with acetylacetone-chloroform at approximately pH 2, and rare earth elements are separated from other coexisting elements by extraction with PMBP-benzene in the presence of ammonium thiocyanate and sulfosalicylic acid at pH 5.5. This is followed by back-extraction with dilute hydrochloric acid, where azochlorophosphine-mA reacts with rare earth elements to form a blue complex, the absorbance of which is measured at 670 nm using a spectrophotometer. While this method offers high accuracy, the repeated extraction process is cumbersome, difficult to master, and time-consuming. The standard operating procedures are generally difficult for technical personnel to understand. Furthermore, the use of volatile organic reagents such as acetylacetone-chloroform and PMBP-benzene poses significant health risks and causes severe environmental pollution.

[0007] Therefore, developing a rapid method for determining the total rare earth content during the recycling of NdFeB waste has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method for detecting rare earth elements and its applications. The method provided by this invention eliminates the need for cumbersome experimental procedures such as extraction, back-extraction, and matrix precipitation to separate the rare earth elements from the sample matrix, thus eliminating interference from iron in the sample. It avoids significant errors in rare earth element quantification due to variations in iron content in NdFeB. Detection can be achieved using only an economical and practical visible spectrophotometer, facilitating widespread adoption and holding significant importance for the production, recovery, and research and development of NdFeB.

[0009] To achieve this objective, the present invention adopts the following technical solution: On the one hand, the present invention provides a method for detecting rare earth elements, the method comprising the following steps: (1) mixing the sample to be tested with aqua regia to obtain a solution to be tested; (2) mixing the solution to be tested with hydrochloric acid, hydroxylamine hydrochloride, and glass beads and boiling, then mixing with a buffer solution and o-phenanthroline, detecting the absorbance, and calculating the iron ion content in the solution to be tested by combining with a standard curve; (3) taking an iron reserve solution and mixing with oxalic acid, Zn-EDTA, azophosphine-mA, and hydrogen peroxide. (4) Take the test solution and mix it with the rare earth standard solution, and then mix it with oxalic acid, Zn-EDTA and azophosphine-mA to obtain a series of test solutions; (5) Use the background solution as the detection background and perform absorbance detection on the series of test solutions. According to the detection results, use the total amount of rare earth in the added rare earth standard solution as the abscissa and absorbance as the ordinate to perform linear fitting. The absolute value of the intersection of the fitting curve and the abscissa is the rare earth element content in the test solution. Then calculate the rare earth element content in the test sample.

[0010] Steps (3) and (4) are not in any particular order.

[0011] The above scheme, by detecting the iron content in the sample and preparing a background solution, ensures that the iron content in the solution does not affect the determination of the total rare earth element. Hydrogen peroxide can oxidize all iron to its highest valence state, eliminating the interference of low-valence iron ions on the rare earth determination, and oxalic acid can mask iron ions. The above method does not require cumbersome experimental operations such as extraction, back-extraction, and matrix precipitation to separate the sample matrix from the rare earth elements, eliminating the interference of iron in the sample. It will not cause large errors in the quantification of rare earth elements due to changes in the iron content in NdFeB, and has high detection accuracy. It can be achieved using only an economical and practical visible spectrophotometer, which is easy to promote and has important significance for the production, recovery, and research and development of NdFeB.

[0012] In the above scheme, step (2) is to determine the iron content by conventional o-phenanthroline spectrophotometry. The present invention does not impose too many restrictions on the parameter range.

[0013] Preferably, the sample to be tested is a neodymium iron boron material.

[0014] Preferably, the standard curve in step (2) is obtained by a method including the following steps: diluting the iron ion standard solution to obtain a series of standard solutions, mixing and boiling them with hydrochloric acid, hydroxylamine hydrochloride and glass beads, then titrating them, mixing them with buffer solution and o-phenanthroline after titration, detecting the absorbance, and fitting the standard curve with iron content as the abscissa and absorbance as the ordinate based on the results.

[0015] Preferably, the iron ion content in the iron reserve solution in step (3) is the same as the iron ion content in the test solution.

[0016] Preferably, the concentration of oxalic acid in the background solution in step (3) is 0.025-0.1 g / 50 mL.

[0017] Preferably, the concentration of Zn in the background solution in step (3) is 0.001-0.005 g / 50mL.

[0018] Preferably, the concentration of EDTA in the background solution in step (3) is 0.05-0.25 g / 50 mL.

[0019] Preferably, the concentration of azophosphine-mA in the background solution in step (3) is 0.0005-0.003 g / 50mL.

[0020] Preferably, the concentration of hydrogen peroxide in the background solution in step (3) is 1-1.5 wt%.

[0021] Preferably, the rare earth standard solution in step (4) is a neodymium standard solution.

[0022] Preferably, the rare earth element is a light rare earth element.

[0023] On the other hand, the present invention also provides the application of the rare earth element detection method described above in the recycling of neodymium iron boron magnetic waste.

[0024] Compared with existing technologies, this invention has the following advantages: This invention provides a method for detecting rare earth elements. By detecting the iron content in the sample and preparing a background solution, it ensures that the iron content in the solution does not affect the determination of the total rare earth element. Hydrogen peroxide can oxidize all iron to its highest valence state, eliminating the interference of low-valence iron ions on the determination of rare earth elements. Oxalic acid can mask iron ions. The above methods do not require cumbersome experimental operations such as extraction, back-extraction, and matrix precipitation to separate the sample matrix from the rare earth elements, eliminating the interference of iron in the sample. It will not cause large errors in the quantitative determination of rare earth elements due to changes in the iron content in NdFeB. The detection accuracy is high, and detection can be achieved using only an economical and practical visible spectrophotometer, which is easy to promote and has important significance for the production, recovery, and research and development of NdFeB. Attached Figure Description

[0025] Figure 1 shows the detection results and linear fitting curves obtained in step four of Example 1. Detailed Implementation

[0026] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0027] Example 1 This example provides a method for detecting rare earth elements. The specific steps are as follows: Step 1: Weigh 0.6879 g of neodymium iron boron (NdFeB) with the electroplating layer, oxide layer and attached impurities removed (the total rare earth element content was determined to be 29.0% using XB / T617.1-2014 beforehand, the same below), add 10 mL of aqua regia to dissolve it, then add deionized water to make up to 100 mL, and then take 1 mL of this solution and add water to make up to 100 mL to obtain the test solution A; Step 2: Sequentially transfer 0, 2.00, 4.00, 6.00, 8.00 and 10.0 mL of iron ion standard solution B (prepared in advance with Fe ion concentration of 4 μg / mL) into 150 mL Erlenmeyer flasks, add distilled water to 50.0 mL, then add 1 mL of hydrochloric acid (volume ratio of 37% concentrated hydrochloric acid: water = 1:3), 1 mL of 10% hydroxylamine hydrochloride, and 2 glass beads. Heat to boiling until approximately 15 mL of solution remains. Cool and quantitatively transfer to a 50 mL stoppered colorimetric tube. Add a small piece of Congo red test paper and add saturated sodium acetate solution until the paper just turns red. Add 5 mL of buffer solution (40 g ammonium acetate to 50 mL glacial acetic acid / 100 mL), 2 mL of 0.5% o-phenanthroline solution, and add water to the mark. Shake well. After 15 min of color development, measure the absorbance at 510 nm using a 10 mm cuvette with water as a reference. Plot the absorbance (corrected for blank) against the amount of iron in micrograms.

[0028] Step 3: Take 0.5 mL of solution A and place it in a 150 mL Erlenmeyer flask. Add distilled water to a final volume of 50.0 mL, then add 1 mL of hydrochloric acid (37% concentrated hydrochloric acid:water = 1:3 by volume), 1 mL of 10% hydroxylamine hydrochloride, and 2 glass beads. Heat to boiling until approximately 15 mL of solution remains. Cool and quantitatively transfer the solution to a 50 mL stoppered colorimetric tube. Add a small piece of Congo red test paper and add saturated sodium acetate solution until the test paper just turns red. Add 5 mL of buffer solution (40 g ammonium acetate to 50 mL glacial acetic acid / 100 mL), 2 mL of 0.5% o-phenanthroline solution, and add water to the mark. Shake well. After 15 min of color development, measure the absorbance at 510 nm using a 10 mm cuvette with water as a reference. Based on the iron standard curve prepared in Step 2, determine that the iron ion content of solution A is 160 mg / L, consistent with the iron content in the background solution used for rare earth determination.

[0029] Step 4, a. Prepare oxalic acid solution (50 g / L), Zn-EDTA solution (3.23 g zinc acetate dihydrate + 25 g disodium ethylenediaminetetraacetate (EDTA) diluted with water to 1 L), azophosphine-mA solution (0.5 g / L), H2O2 solution (30 wt.%), and iron stock solution C (100 μg / mL, commercially available), the same below.

[0030] b. First, take 0.8 mL of iron stock solution C (100 ug / mL) and place it in a 50 mL volumetric flask. Add 2.0 mL of oxalic acid solution, 2.0 mL of Zn-EDTA solution, 4.0 mL of azophosphine-mA solution, and 2.0 mL of H2O. Dilute with water to the mark, mix well, and label it as S0.

[0031] c. Then, take 0.5 mL of solution A and place it in a 50 mL volumetric flask. Add 1.00, 2.00, 3.00, 4.00, and 5.0 mL of rare earth standard solution D (5 ug / mL neodymium standard solution), respectively. Add 2.0 mL of oxalic acid solution, 2.0 mL of Zn-EDTA solution, 4.0 mL of azophosphine-mA solution, and 2.0 mL of H2O. Dilute with water to the mark, mix well, and let stand for 5 min. Label the flasks as S1, S2, S3, S4, and S5, respectively.

[0032] d. Using a 10mm cuvette filled with solution labeled S0 as the background, measure the absorbance of solutions S1, S2, S3, S4, and S5 at a wavelength of 669nm. Plot the mass (ug) of rare earth in the added rare earth standard solution D on the x-axis and the absorbance of the solution on the y-axis. The intersection of the curve with the x-axis is the rare earth content of 0.5 mL of the test solution A (as shown in Figure 1).

[0033] e. Formula for calculating the total rare earth content of NdFeB samples (hereinafter the same): w% = (c × 10 -2 / m)×100% (Formula 1); where: w is the rare earth content in the measured NdFeB sample, %; c is the total rare earth content determined in this experiment, μg; m is the weight of the weighed NdFeB sample, g.

[0034] Step 5: Based on the rare earth content of the test solution A obtained in Step 4, calculate the total rare earth content in the NdFeB sample as 28.8% according to (Formula 1), with a relative error of 0.7%.

[0035] Example 2 This example provides a method for detecting rare earth elements. The specific steps are as follows: Step 1: Weigh 0.7125 g of NdFeB (neodymium iron boron) with the electroplated layer or oxide layer and attached impurities removed, add 10 mL of aqua regia to dissolve it, then add deionized water to make up to 100 mL. Then take 1 mL of this solution and add water to make up to 100 mL to obtain the test solution A. Step 2: Sequentially transfer 0, 2.00, 4.00, 6.00, 8.00, and 10.0 mL of iron ion standard solution B (pre-prepared solution with Fe ion concentration of 4 μg / mL) into 150 mL Erlenmeyer flasks, add distilled water to 50.0 mL, then add 1 mL of hydrochloric acid (volume ratio of 37% concentrated hydrochloric acid:water = 1:3), 1 mL of 10% hydroxylamine hydrochloride, and 2 glass beads. Heat to boiling until about 15 mL of solution remains, cool, and quantitatively transfer to a 50 mL stoppered colorimetric tube. Add a small piece of Congo red test paper, and add saturated sodium acetate solution until the paper just turns red. Add 5 mL of buffer solution (40 g ammonium acetate to 50 mL glacial acetic acid / 100 mL), 2 mL of 0.5% o-phenanthroline solution, and add water to the mark. Shake well. After 15 min of color development, measure the absorbance at 510 nm using a 10 mm cuvette with water as a reference. Plot the absorbance (corrected for blank) against the amount of iron in micrograms.

[0036] Step 3: Take 1.0 mL of solution A and place it in a 150 mL Erlenmeyer flask. Add distilled water to a final volume of 50.0 mL, then add 1 mL of hydrochloric acid (37% concentrated hydrochloric acid:water = 1:3 by volume), 1 mL of 10% hydroxylamine hydrochloride, and 2 glass beads. Heat to boiling until approximately 15 mL of solution remains. Cool and quantitatively transfer the solution to a 50 mL stoppered colorimetric tube. Add a small piece of Congo red test paper and add saturated sodium acetate solution until the test paper just turns red. Add 5 mL of buffer solution (40 g ammonium acetate to 50 mL glacial acetic acid / 100 mL), 2 mL of 0.5% o-phenanthroline solution, and add water to the mark. Shake well. After 15 min of color development, measure the absorbance at 510 nm using a 10 mm cuvette with water as a reference. Based on the iron standard curve prepared in Step 2, determine that the iron ion content of solution A is 160 mg / L, consistent with the iron content in the background solution used for rare earth determination.

[0037] Step 4, a. First, take 0.8 mL of iron stock solution C and place it in a 50 mL volumetric flask. Add 2.0 mL of oxalic acid solution, 2.0 mL of Zn-EDTA solution, 4.0 mL of azophosphine-mA solution, and 2.0 mL of H2O. Dilute with water to the mark, mix well, and label it as S0.

[0038] b. Then, take 1.0 mL of solution A and place it in a 50 mL volumetric flask. Add 1.00, 2.00, 3.00, 4.00, and 5.0 mL of rare earth standard solution D (5 ug / mL neodymium standard solution), respectively. Add 2.0 mL of oxalic acid solution, 2.0 mL of Zn-EDTA solution, 4.0 mL of azophosphine-mA solution, and 2.0 mL of H2O. Dilute with water to the mark, mix well, and let stand for 5 min. Label the flasks as S1, S2, S3, S4, and S5, respectively.

[0039] c. Using a 10mm cuvette filled with solution labeled S0 as background, measure the absorbance of solutions S1, S2, S3, S4, and S5 at a wavelength of 669nm. Plot the mass (ug) of rare earth in the added rare earth standard solution D on the x-axis and the absorbance of the solution on the y-axis. The intersection of the curve with the x-axis is the rare earth content of 1.0 mL of the test solution.

[0040] Step 5: Based on the rare earth content of the test solution A obtained in Step 4, calculate the total rare earth content in the NdFeB sample as 29.2% according to (Formula 1).

[0041] Example 3 This example provides a method for detecting rare earth elements. The specific steps are as follows: Step 1: Weigh 0.6988 g of NdFeB (neodymium iron boron) with the electroplated layer or oxide layer and attached impurities removed, add 10 mL of aqua regia to dissolve it, then add deionized water to make up to 100 mL. Then take 1 mL of this solution and add water to make up to 100 mL to obtain the test solution A; Step 2: Sequentially transfer 0, 2.00, 4.00, 6.00, 8.00, and 10.0 mL of iron ion standard solution B (pre-prepared solution with Fe ion concentration of 4 μg / mL) into 150 mL Erlenmeyer flasks, add distilled water to 50.0 mL, then add 1 mL of hydrochloric acid (volume ratio of 37% concentrated hydrochloric acid:water = 1:3), 1 mL of 10% hydroxylamine hydrochloride, and 2 glass beads. Heat to boiling until about 15 mL of solution remains, cool, and quantitatively transfer to a 50 mL stoppered colorimetric tube. Add a small piece of Congo red test paper, and add saturated sodium acetate solution until the paper just turns red. Add 3 mL of buffer solution (40 g ammonium acetate to 50 mL glacial acetic acid / 100 mL), 2 mL of 0.5% o-phenanthroline solution, and add water to the mark. Shake well. After 15 min of color development, measure the absorbance at 510 nm using a 10 mm cuvette with water as a reference. Plot the absorbance (corrected for blank) against the amount of iron in micrograms.

[0042] Step 3: Take 0.5 mL of solution A and place it in a 150 mL Erlenmeyer flask. Add distilled water to a final volume of 50.0 mL, then add 1 mL of hydrochloric acid (37% concentrated hydrochloric acid:water = 1:3 by volume), 1 mL of 10% hydroxylamine hydrochloride, and 2 glass beads. Heat to boiling until approximately 15 mL of solution remains. Cool and quantitatively transfer the solution to a 50 mL stoppered colorimetric tube. Add a small piece of Congo red test paper and add saturated sodium acetate solution until the test paper just turns red. Add 4 mL of buffer solution (40 g ammonium acetate plus 50 mL glacial acetic acid / 100 mL), 2 mL of 0.5% o-phenanthroline solution, and add water to the mark. Shake well. After 15 min of color development, measure the absorbance at 510 nm using a 10 mm cuvette with water as a reference. Based on the iron standard curve prepared in Step 2, determine that the iron ion content of solution A is 160 mg / L, consistent with the iron content in the background solution used for rare earth determination.

[0043] Step 4, a. First, take 0.8 mL of iron stock solution C and place it in a 50 mL volumetric flask. Add 1.5 mL of oxalic acid solution, 2.0 mL of Zn-EDTA solution, 4.0 mL of azophosphine-mA solution, and 2.0 mL of H2O. Dilute with water to the mark, mix well, and label it as S0.

[0044] b. Then, take 0.5 mL of solution A and place it in a 50 mL volumetric flask. Add 1.00, 2.00, 3.00, 4.00, and 5.0 mL of rare earth standard solution D (5 ug / mL neodymium standard solution), 2.0 mL of oxalic acid solution, 2.0 mL of Zn-EDTA solution, 4.0 mL of azophosphine-mA solution, and 2.0 mL of H2O, respectively. Dilute with water to the mark, mix well, and let stand for 5 min. Label the flasks as S1, S2, S3, S4, and S5, respectively.

[0045] c. Using a 10mm cuvette filled with solution labeled S0 as the background, measure the absorbance of solutions S1, S2, S3, S4, and S5 at a wavelength of 669nm. Plot the mass (ug) of rare earth in the added rare earth standard solution D on the x-axis and the absorbance of the solution on the y-axis. The intersection of the curve with the x-axis is the rare earth content of 0.5 mL of the test solution.

[0046] Step 5: Based on the rare earth content of the test solution A obtained in Step 4, calculate the total rare earth content in the NdFeB sample as 28.4% according to (Formula 1).

[0047] Comparative Example 1 provides a method for detecting rare earth elements. The specific steps are the same as in Example 1, except that iron ions are not added to the background solution.

[0048] The total rare earth content in the NdFeB sample was finally calculated to be 56.7%, with a relative error of 95.52%.

[0049] Comparative Example 2 provides a method for detecting rare earth elements. The specific steps are the same as in Example 1, except that Zn-EDTA is not added.

[0050] The total rare earth content in the NdFeB sample was finally calculated to be 42.2%, with a relative error of 45.52%.

[0051] Comparative Example 3 provides a method for the detection of rare earth elements. The specific steps are as follows: Prepare reagents in advance: nitric acid (1 part 68% nitric acid + 3 parts water); oxalic acid (50 g / L); azophosphorus mA solution (0.4 g / L); rare earth standard solution (4 μg / mL); prepared with mixed rare earth oxides or high-purity oxides; pure iron blank solution (3 mg / mL); Analytical steps: Step 1: Accurately weigh 0.1 g of the sample into a 150 mL conical flask, add 10 mL of nitric acid, heat the sample until completely dissolved, remove and cool, transfer the solution into a 50 mL volumetric flask, dilute with water to the mark, and mix well; Step 2: Accurately transfer 5 mL of the above solution into a 25 mL volumetric flask, add 7 mL of oxalic acid solution and 2.0 mL of azophosphorus mA solution, mix well, dilute with water to the mark, and mix well.

[0052] Step 3: Transfer a portion of the test solution into a 2 or 3 cm cuvette. Measure the absorbance at a spectrophotometer wavelength of 660 nm, using a pure iron blank solution as a reference. Determine the rare earth content from the standard curve.

[0053] To construct the standard curve, accurately weigh several 5 mL aliquots of pure iron blank solution into a series of 25 mL volumetric flasks. Accurately transfer 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 4.5, and 5.0 mL of rare earth standard solution. Follow the above operating steps. Using the blank solution without rare earth as a reference, plot the rare earth content on the x-axis and the absorbance value on the y-axis to construct the standard curve.

[0054] The mass fraction (%) of rare earth elements in the sample was calculated using Formula 2: w = (m1 × V0 × 10) -6 ) / (mV)×100%(Formula 2)Where, m1 is the mass of rare earth obtained from the standard curve, g; m is the mass of the sample, g; V0 is the total volume of the sample solution, mL; V is the volume of the sample solution transferred, mL.

[0055] The rare earth content in the sample was finally calculated to be 22.95%, with a relative error of 20.86%.

[0056] The data above shows that the method provided by this invention does not require cumbersome experimental operations such as extraction, back-extraction, and matrix precipitation to separate the sample matrix from rare earth elements, eliminating the interference of iron elements in the sample. It will not cause large errors in the quantification of rare earth elements due to changes in the iron content in NdFeB, and has high detection accuracy. It can be detected using only an economical and practical visible spectrophotometer, which is easy to promote. Comparing Examples 1, 4-5 and Comparative Example 1, it can be found that this invention can effectively improve the detection accuracy compared with the prior art by using specific raw materials.

[0057] The applicant declares that the rare earth element detection method and its application are illustrated by the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0058] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0059] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for detecting rare earth elements, characterized in that, The rare earth element detection method includes the following steps: (1) Mix the sample to be tested with aqua regia to obtain the test solution; (2) Mix the test solution with hydrochloric acid, hydroxylamine hydrochloride and glass beads and boil, then mix with buffer solution and o-phenanthroline, detect the absorbance, and calculate the iron ion content in the test solution by combining with the standard curve; (3) Take the iron reserve solution and mix with oxalic acid, Zn-EDTA, azophosphine-mA and hydrogen peroxide to obtain the background solution; (4) Take the test solution and mix with the rare earth standard solution, then mix with oxalic acid, Zn-EDTA and azophosphine-mA to obtain a series of test solutions; (5) Use the background solution as the detection background, detect the absorbance of the series of test solutions, and perform linear fitting based on the detection results with the total amount of rare earth in the added rare earth standard solution as the abscissa and the absorbance as the ordinate. The absolute value of the intersection of the obtained fitting curve and the abscissa is the rare earth element content in the test solution, and then calculate the rare earth element content in the test sample; Steps (3) and (4) are not distinguished by order.

2. The rare earth element detection method according to claim 1, characterized in that, The sample to be tested is a neodymium iron boron material.

3. The rare earth element detection method according to claim 1 or 2, characterized in that, The standard curve in step (2) is obtained by a method including the following steps: diluting the iron ion standard solution to obtain a series of standard solutions, mixing them with hydrochloric acid, hydroxylamine hydrochloride and glass beads, boiling them, titrating them, mixing them with buffer solution and o-phenanthroline after titration, detecting the absorbance, and fitting the standard curve with iron content as the abscissa and absorbance as the ordinate based on the results.

4. The method for detecting rare earth elements according to any one of claims 1-3, characterized in that, The iron ion content in the iron reserve solution in step (3) is the same as the iron ion content in the test solution.

5. The method for detecting rare earth elements according to any one of claims 1-4, characterized in that, The concentration of oxalic acid in the background solution in step (3) is 0.025-0.1 g / 50mL.

6. The method for detecting rare earth elements according to any one of claims 1-5, characterized in that, The concentration of Zn in the background solution in step (3) is 0.001-0.005 g / 50mL; preferably, the concentration of EDTA in the background solution in step (3) is 0.05-0.25 g / 50mL.

7. The method for detecting rare earth elements according to any one of claims 1-6, characterized in that, The concentration of azophosphine-mA in the background solution in step (3) is 0.0005-0.003 g / 50mL; preferably, the concentration of hydrogen peroxide in the background solution in step (3) is 1-1.5 wt%.

8. The method for detecting rare earth elements according to any one of claims 1-7, characterized in that, The rare earth standard solution mentioned in step (4) is a neodymium standard solution.

9. The method for detecting rare earth elements according to any one of claims 1-8, characterized in that, The rare earth element is a light rare earth element.

10. The application of a rare earth element detection method according to any one of claims 1-9 in the recycling of neodymium iron boron magnetic waste.

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