Comprehensive recovery method of neodymium iron boron permanent magnet waste

Abstract

The invention provides a comprehensive recovery method of neodymium-iron-boron permanent magnet waste, which comprises the following steps: acidizing neodymium-iron-boron permanent magnet waste, removing impurities, extracting to obtain an organic phase and a first raffinate, reversely extracting the organic phase, and precipitating by oxalic acid to obtain holmium oxalate; extracting the first raffinate to obtain an organic phase and a second raffinate, reversely extracting the organic phase, and precipitating oxalic acid to obtain dysprosium oxalate; extracting the second raffinate to obtain an organic phase and a third raffinate, reversely extracting the organic phase, and precipitating oxalic acid to obtain gadolinium oxalate; extracting the third raffinate to obtain an organic phase and a fourth raffinate, reversely extracting the organic phase, and precipitating oxalic acid to obtain neodymium oxalate; carrying out oxalic acid precipitation on the fourth raffinate to obtain praseodymium oxalate. According to the method, efficient separation and high-recovery-rate recovery of various rare earth metals in the neodymium-iron-boron permanent magnet waste are achieved through the multi-stage solvent extraction-precipitation-roasting process, high-purity rare earth compounds are obtained, the resource utilization rate is increased, and dependence on original rare earth can be remarkably reduced.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology and relates to a comprehensive recycling method for neodymium iron boron permanent magnet waste. Background Technology

[0002] With the rapid development of modern science and technology, the application scope of rare earth metals has been continuously expanding, and they have now become indispensable raw materials for high-tech new materials. Rare earth permanent magnet materials utilize the special magnetic properties of rare earths to manufacture various super permanent magnets. Due to the characteristics of high magnetic energy product and small size, neodymium iron boron materials are now widely used in various motors, nuclear magnetic resonance imaging devices, maglev trains, and other optical and electronic technologies. Rare earth, as a collective term for 17 metallic elements, has become the "vitamins" of the modern industrial system.

[0003] my country is a major rare earth producer, ranking first in the world in both production and export. It supplies over 90% of the global NdFeB permanent magnet market, and holds a dominant position in rare earth refining capacity (92%) and heavy rare earth separation technology (100%). Such dominance cannot be easily overcome in the short term. Rare earths also play a crucial role in metallurgical machinery, petrochemicals, and glass ceramics. Compared to recycling rare earths from ore, refining rare earths from waste is a more environmentally friendly and cost-effective method. With increasingly stringent environmental regulations, the recycling of processing waste and end-of-life rare earth materials, especially NdFeB permanent magnet waste, has become critical to effectively alleviate supply chain tensions. Therefore, researchers are increasingly focusing on the recycling of NdFeB permanent magnet waste and the development of new magnetic materials.

[0004] CN120193173A discloses a method for recovering rare earth elements from NdFeB waste, the method comprising the following steps: Step S1: adding the NdFeB waste to an oxidizing acid solution to obtain an oxidizing acid leaching solution; Step S2: adjusting the pH of the oxidizing acid leaching solution with alkali and then performing extraction treatment with a composite extractant, separating the raffinate and the loaded organic phase; Step S3: performing a first back-extraction treatment on the loaded organic phase using a first hydrochloric acid solution; Step S4: performing a second back-extraction treatment on the first back-extraction raffinate using a second hydrochloric acid solution; Step S5: performing a third back-extraction treatment on the second back-extraction raffinate using a third hydrochloric acid solution.

[0005] CN105002366A discloses a method for recovering rare earth from the neutralization residue generated during the rare earth recovery process of NdFeB waste, comprising the following steps: (1) roasting the neutralization residue; (2) dissolving, extracting and filtering the powder, acidic extractant and water in proportion; (3) enriching and filtering the liquid B2 and enriching agent in proportion; (4) dissolving and filtering the solid A2, solvent and water in proportion; (5) precipitating and filtering the liquid B4, precipitant and regulator in proportion; (6) after the solid A4 is ignited, it is dissolved to prepare a feed solution, which is then selectively extracted and separated by line A and / or line B, and then subjected to precipitation washing and ignition processes to obtain products such as dysprosium oxide, gadolinium oxide, neodymium oxide and terbium oxide that meet national standards and customer needs.

[0006] The aforementioned methods cannot achieve separate extraction of rare earth elements or result in low purity and low leaching rates. Therefore, developing a hydrometallurgical process for efficiently separating and purifying rare earth elements from NdFeB permanent magnet waste is of significant practical importance. Summary of the Invention

[0007] The purpose of this invention is to provide a comprehensive recycling method for NdFeB permanent magnet waste. This invention achieves efficient separation and high recovery rate of various rare earth metals in NdFeB permanent magnet waste through a multi-stage solvent extraction-precipitation-calcination process, obtaining high-purity rare earth compounds, improving resource utilization, and significantly reducing dependence on primary rare earths.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a comprehensive recycling method for neodymium iron boron permanent magnet waste, the comprehensive recycling method comprising the following steps:

[0010] The waste NdFeB permanent magnets were subjected to acidification and impurity removal treatment to obtain a rare earth salt solution. The rare earth salt solution was subjected to a first extraction treatment to obtain the extracted Ho organic phase and the first extraction residue. The extracted Ho organic phase was subjected to a first back-extraction treatment and oxalic acid precipitation treatment to obtain Ho2(C2O4)3.

[0011] The first raffinate was subjected to a second extraction treatment to obtain the Dy organic phase and the second raffinate. The Dy organic phase was subjected to a second back-extraction treatment and oxalic acid precipitation to obtain Dy2(C2O4)3.

[0012] The second raffinate was subjected to a third extraction treatment to obtain the extracted Gd organic phase and the third raffinate. The extracted Gd organic phase was subjected to a third back-extraction treatment and oxalic acid precipitation of Gd to obtain Gd2(C2O4)3.

[0013] The third raffinate was subjected to a fourth extraction treatment to obtain the Nd organic phase and the fourth raffinate. The Nd organic phase was subjected to a fourth back-extraction treatment and Nd precipitation with oxalic acid to obtain Nd2(C2O4)3.

[0014] The fourth raffinate was treated with oxalic acid to precipitate Pr, yielding Pr2(C2O4)3.

[0015] This invention acidifies and removes impurities from NdFeB permanent magnet waste, eliminating non-rare earth impurities such as iron and boron. Various rare earth elements are then converted into soluble salts and dissolved in solution for easier subsequent extraction. Based on the characteristics and difficulty of extraction of each rare earth element, Ho, Dy, Gd, Nd, and Pr are extracted and separated sequentially through a multi-stage extraction system, avoiding cross-contamination. This achieves the individual separation of rare earth elements and produces high-purity single rare earth compounds with a purity of 4N. The comprehensive recycling process leaves no residual rare earth waste, meeting green metallurgy requirements and addressing the industry pain points of low separation efficiency and high environmental costs associated with traditional processes.

[0016] In the comprehensive recovery method described in this invention, the extractants used for various rare earth elements are selected based on their pH dependence and differences in coordination ability.

[0017] Preferably, the acid solution used in the acidification and impurity removal treatment includes any one or a combination of at least two of hydrochloric acid, nitric acid, or sulfuric acid.

[0018] Preferably, the pH of the acid solution is 1.5 to 2.5, for example: 1.5, 1.8, 2, 2.2 or 2.5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the mass-to-volume ratio of the acid solution to the NdFeB permanent magnet waste is (8-12):1, for example: 8:1, 9:1, 10:1, 11:1 or 12:1, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the pH of the rare earth salt solution is 1 to 1.5, for example: 1, 1.1, 1.2, 1.3, 1.4 or 1.5, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, the metal elements in the rare earth salt solution include Nd, Pr, Gd, Dy, and Ho.

[0022] Preferably, the extraction system used in the first extraction process includes an extractant and a diluent.

[0023] Preferably, the extractant used in the first extraction process includes C272 extractant.

[0024] The first extraction process of this invention uses C272 as the extractant to extract holmium (Ho). Extractant C272 (di(2-ethylhexyl)phosphoric acid) extracts Ho... 3+ The selectivity of Ho is higher than that of other rare earth elements such as Dy, Gd, and Nd. At a specific pH, Ho... 3+ The rare earth elements are extracted into the organic phase, while the other rare earth elements remain in the aqueous phase, i.e., the first raffinate.

[0025] Preferably, the diluent used in the first extraction process includes sulfonated kerosene.

[0026] Preferably, the molar concentration of the extractant in the extraction system used in the first extraction treatment is 0.8 mol / L to 1.2 mol / L, for example: 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L or 1.2 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the number of extraction stages in the first extraction process is 10 to 20, such as 10, 12, 15, 18 or 20 stages, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the pH of the first raffinate is 1.8 to 2.2, for example: 1.8, 1.9, 2, 2.1 or 2.2, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the extraction system used in the second extraction process includes an extractant and a diluent.

[0030] Preferably, the extractant used in the second extraction process includes P507 extractant.

[0031] The P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) used in the second extraction process of this invention is effective against Dy 3+ Its selectivity is superior to Gd, Nd, etc. Dy 3+ It enters the organic phase, while the remaining rare earth elements remain in the second raffinate.

[0032] Preferably, the diluent used in the second extraction process includes sulfonated kerosene.

[0033] Preferably, the molar concentration of the extractant in the extraction system used in the second extraction treatment is 0.3 mol / L to 0.7 mol / L, for example: 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L or 0.7 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the number of extraction stages in the second extraction process is 18 to 25, for example: 18, 19, 20, 22 or 25 stages, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the pH of the second raffinate is 2.5 to 3, for example: 2.5, 2.6, 2.7, 2.8, 2.9 or 3, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the extraction system used in the third extraction process includes an extractant and a diluent.

[0037] Preferably, the extractant used in the third extraction process includes P229 extractant.

[0038] The third extraction process described in this invention uses P229, a phosphonic acid extractant, which is effective against Gd. 3 It has high selectivity and can be separated from the remaining rare earth elements.

[0039] Preferably, the diluent used in the third extraction process includes sulfonated kerosene.

[0040] Preferably, the molar concentration of the extractant in the extraction system used in the third extraction process is 0.8 mol / L to 1.2 mol / L, for example: 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L or 1.2 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, the number of extraction stages in the third extraction process is 12 to 18, for example: 12, 14, 15, 16 or 18 stages, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the pH of the third raffinate is 2.2 to 2.8, for example: 2.2, 2.3, 2.5, 2.7 or 2.8, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the extraction system used in the fourth extraction process includes an extractant and a diluent.

[0044] Preferably, the extractant used in the fourth extraction process includes P204 extractant.

[0045] The P204 (di(2-ethylhexyl)phosphoric acid) used in the fourth extraction process of this invention is effective against Nd2O4. 3 + has stronger extraction ability than Pr 3+ This process allows Nd to enter the organic phase, while Pr remains in the final raffinate. Finally, after precipitation with oxalic acid, sintering yields high-purity Pr2O3.

[0046] Preferably, the diluent used in the fourth extraction process includes sulfonated kerosene.

[0047] Preferably, the molar concentration of the extractant in the extraction system used in the fourth extraction process is 0.8 mol / L to 1.2 mol / L, for example: 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L or 1.2 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the extraction stage of the fourth extraction process is 60 to 80 stages, for example: 60 stages, 65 stages, 70 stages, 75 stages or 80 stages, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] The fourth raffinate of this invention mainly contains Pr 3+ Pr2(C2O4)3 can be precipitated directly by adding oxalic acid, and then calcined to obtain Pr2O3.

[0050] Preferably, the stripping agents used in the first, second, third, and fourth stripping treatments independently include any one or a combination of at least two of hydrochloric acid, nitric acid, or sulfuric acid.

[0051] Preferably, the mass concentration of the back-extraction agent is 1 mol / L to 6 mol / L, for example: 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 6 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the oxalic acid concentration used in the oxalic acid precipitation Ho treatment, oxalic acid precipitation Dy treatment, oxalic acid precipitation Gd treatment, oxalic acid precipitation Nd treatment, and oxalic acid precipitation Pr treatment is 0.05 mol / L to 0.3 mol / L, for example: 0.05 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, or 0.3 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] The reaction equations for the oxalic acid precipitation Ho treatment, oxalic acid precipitation Dy treatment, oxalic acid precipitation Gd treatment, oxalic acid precipitation Nd treatment, and oxalic acid precipitation Pr treatment (hereinafter collectively referred to as rare earth elements RE) described in this invention are as follows:

[0054] 2RE 3+ +3H₂C₂O₄→RE₂(C₂O₄)₃↓+6H + .

[0055] Preferably, the oxalic acid precipitation Ho treatment, oxalic acid precipitation Dy treatment, oxalic acid precipitation Gd treatment, oxalic acid precipitation Nd treatment, and oxalic acid precipitation Pr treatment are calcined independently to obtain oxides.

[0056] Preferably, the roasting temperature is independently between 600℃ and 900℃, for example: 600℃, 650℃, 700℃, 800℃ or 900℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] The reaction equation for calcination described in this invention is as follows:

[0058] RE2(C2O4)3+O2→RE2O3+3CO2↑.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) This invention achieves efficient separation and recovery of various rare earth metals in neodymium iron boron permanent magnet waste through a multi-stage solvent extraction-precipitation-calcination process, obtaining high-purity rare earth compounds, improving resource utilization, and significantly reducing dependence on primary rare earths.

[0061] (2) This invention achieves efficient separation of rare earth elements in neodymium iron boron waste through a multi-stage extraction process, promoting the rare earth recycling technology towards high purity (4N grade), low energy consumption, and zero pollution. It can solve the problem of separating heavy rare earth and light rare earth, and has both economic and environmental advantages, providing key technical support for the recycling of rare earth strategic resources. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the process flow for the comprehensive recycling method of neodymium iron boron permanent magnet waste provided in an embodiment of the present invention. Detailed Implementation

[0063] 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.

[0064] The rare earth salt solutions described in the embodiments and comparative examples of this invention were all prepared by the following method:

[0065] Hydrochloric acid with a pH of 2 was mixed with NdFeB permanent magnet waste at a solid-liquid mass-to-volume ratio of 1:10. The NdFeB permanent magnet waste was then subjected to acidification and impurity removal treatment to obtain a rare earth chloride solution. The mass concentrations of various rare earth ions in the rare earth chloride solution are as follows:

[0066] Nd is 25 g / L, Pr is 7 g / L, Gd is 4 g / L, Dy is 0.5 g / L, and Ho is 0.4 g / L;

[0067] The pH of the rare earth chloride salt solution is 1.3.

[0068] Example 1

[0069] This embodiment provides a comprehensive recycling method for neodymium iron boron permanent magnet waste, and the process flow diagram of the comprehensive recycling method is as follows: Figure 1 As shown, the integrated recycling method includes the following steps:

[0070] The rare earth chloride salt solution was subjected to a first extraction treatment using an extraction system of C272 and sulfonated kerosene (C272 molar concentration of 1 mol / L). The extraction stage was 16 stages, yielding the extracted Ho organic phase and the first raffinate at pH 2. The extracted Ho organic phase was then subjected to a first back-extraction treatment using 6 mol / L hydrochloric acid. Ho was then precipitated using 0.05 mol / L oxalic acid and calcined at 800℃ to obtain Ho2O3.

[0071] The first raffinate was subjected to a second extraction treatment using an extraction system of P507 and sulfonated kerosene (P507 molar concentration of 0.5 mol / L). The extraction stage was 21 stages, yielding an organic phase of extracted Dy and a second raffinate with a pH of 2.8. The organic phase of extracted Dy was subjected to a third back-extraction treatment using 4 mol / L hydrochloric acid. Dy was precipitated using 0.05 mol / L oxalic acid and calcined at 800℃ to obtain Dy2O3.

[0072] The second raffinate was subjected to a third extraction using an extraction system of P229 and sulfonated kerosene (P229 molar concentration of 1 mol / L). The extraction was performed in 15 stages to obtain the organic phase containing Gd and the third raffinate with a pH of 2.5. The organic phase containing Gd was then subjected to a third back-extraction using 3 mol / L hydrochloric acid. Gd was precipitated using 0.1 mol / L oxalic acid and calcined at 800 °C to obtain Gd2O3.

[0073] The third raffinate was subjected to a fourth extraction using an extraction system of P204 and sulfonated kerosene (P204 molar concentration of 1 mol / L). The extraction stage was 68 stages, yielding an Nd organic phase and a fourth raffinate. The Nd organic phase was then subjected to a fourth back-extraction using 1 mol / L hydrochloric acid. Nd was precipitated using 0.15 mol / L oxalic acid, and calcined at 800 °C to obtain Nd2O3.

[0074] After oxalic acid precipitation of Pr using the fourth raffinate of 0.3 mol / L oxalic acid, Pr2O3 was obtained by calcination at 800 °C.

[0075] Example 2

[0076] This embodiment provides a comprehensive recycling method for neodymium iron boron permanent magnet waste, and the process flow diagram of the comprehensive recycling method is as follows: Figure 1 As shown, the integrated recycling method includes the following steps:

[0077] The rare earth chloride salt solution was subjected to a first extraction treatment using an extraction system of C272 and sulfonated kerosene (C272 molar concentration of 0.8 mol / L). The extraction stage was 20 stages, resulting in a Ho organic phase and a first raffinate with a pH of 2.2. The Ho organic phase was then subjected to a first back-extraction treatment using 0.056 mol / L hydrochloric acid, followed by Ho precipitation using 0.05 mol / L oxalic acid and calcination at 600 °C to obtain Ho2O3.

[0078] The first raffinate was subjected to a second extraction treatment using an extraction system of P507 and sulfonated kerosene (the molar concentration of P507 was 0.3 mol / L). The extraction was performed in 25 stages to obtain the Dy organic phase and the second raffinate at pH 3. The Dy organic phase was then subjected to a third back-extraction treatment using 4 mol / L hydrochloric acid. Dy was precipitated using 0.05 mol / L oxalic acid and calcined at 700 °C to obtain Dy2O3.

[0079] The second raffinate was subjected to a third extraction using an extraction system of P229 and sulfonated kerosene (P229 molar concentration of 0.8 mol / L). The extraction was performed in 18 stages to obtain the organic phase containing Gd and the third raffinate with a pH of 2.8. The organic phase containing Gd was then subjected to a third back-extraction using 3 mol / L hydrochloric acid. Gd was precipitated using 0.1 mol / L oxalic acid and calcined at 700 °C to obtain Gd2O3.

[0080] The third raffinate was subjected to a fourth extraction using an extraction system of P204 and sulfonated kerosene (P204 molar concentration of 0.8 mol / L). The extraction process consisted of 80 stages, yielding an Nd-extracted organic phase and a fourth raffinate. The Nd-extracted organic phase was then subjected to a fourth back-extraction using 1 mol / L hydrochloric acid. Nd was precipitated using 0.15 mol / L oxalic acid, and calcined at 900 °C to obtain Nd2O3.

[0081] After precipitating Pr with 0.1 mol / L oxalic acid, the fourth raffinate was calcined at 800 °C to obtain Pr2O3.

[0082] Example 3

[0083] This embodiment provides a comprehensive recycling method for neodymium iron boron permanent magnet waste, and the process flow diagram of the comprehensive recycling method is as follows: Figure 1 As shown, the integrated recycling method includes the following steps:

[0084] The rare earth chloride salt solution was subjected to a first extraction treatment using an extraction system of C272 and sulfonated kerosene (C272 molar concentration of 1.2 mol / L). The extraction stage was 10 stages, resulting in a Ho organic phase and a first raffinate at pH 1.8. The Ho organic phase was then subjected to a first back-extraction treatment using 6 mol / L hydrochloric acid, followed by Ho precipitation using 0.05 mol / L oxalic acid and calcination at 700℃ to obtain Ho2O3.

[0085] The first raffinate was subjected to a second extraction treatment using an extraction system of P507 and sulfonated kerosene (P507 molar concentration of 0.7 mol / L). The extraction stage was 18 stages, yielding an organic phase of extracted Dy and a second raffinate with a pH of 2.5. The organic phase of extracted Dy was then subjected to a third back-extraction treatment using 4 mol / L hydrochloric acid. Dy was precipitated using 0.05 mol / L oxalic acid and calcined at 600℃ to obtain Dy2O3.

[0086] The second raffinate was subjected to a third extraction using an extraction system of P229 and sulfonated kerosene (P229 molar concentration of 1.2 mol / L). The extraction was performed in 13 stages to obtain the organic phase containing Gd and the third raffinate with a pH of 2.2. The organic phase containing Gd was then subjected to a third back-extraction using 3 mol / L hydrochloric acid. Gd was precipitated using 0.1 mol / L oxalic acid and calcined at 700 °C to obtain Gd2O3.

[0087] The third raffinate was subjected to a fourth extraction using an extraction system of P204 and sulfonated kerosene (P204 molar concentration of 1.2 mol / L). The extraction was performed in 60 stages to obtain the Nd organic phase and the fourth raffinate. The Nd organic phase was then subjected to a fourth back-extraction using 1 mol / L hydrochloric acid. Nd was precipitated using 0.15 mol / L oxalic acid and calcined at 600 °C to obtain Nd2O3.

[0088] After oxalic acid precipitation of Pr using the fourth raffinate of 0.3 mol / L oxalic acid, Pr2O3 was obtained by calcination at 700 °C.

[0089] Example 4

[0090] The only difference between this embodiment and Example 1 is that the molar concentration of C272 in the first extraction treatment is 0.5 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0091] Example 5

[0092] The only difference between this embodiment and Example 1 is that the molar concentration of C272 in the first extraction treatment is 1.5 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0093] Example 6

[0094] The only difference between this embodiment and Example 1 is that the molar concentration of P507 in the second extraction treatment is 0.1 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0095] Example 7

[0096] The only difference between this embodiment and Example 1 is that the molar concentration of P507 in the second extraction treatment is 1 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0097] Example 8

[0098] The only difference between this embodiment and Example 1 is that the molar concentration of P229 in the third extraction treatment is 0.5 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0099] Example 9

[0100] The only difference between this embodiment and Example 1 is that the molar concentration of P229 in the third extraction treatment is 1.5 mol / L. All other conditions and parameters are exactly the same as in Example 1.

[0101] Example 10

[0102] The only difference between this embodiment and Example 1 is that the molar concentration of P204 in the fourth extraction treatment is 0.5 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0103] Example 11

[0104] The only difference between this embodiment and Example 1 is that the molar concentration of P204 in the fourth extraction treatment is 0.5 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0105] Example 12

[0106] The only difference between this embodiment and Embodiment 1 is that the pH of the rare earth chloride salt solution is controlled at 0.5; all other conditions and parameters are exactly the same as in Embodiment 1.

[0107] Example 13

[0108] The only difference between this embodiment and Embodiment 1 is that the pH of the rare earth chloride salt solution is controlled at 2; all other conditions and parameters are exactly the same as in Embodiment 1.

[0109] Example 14

[0110] The only difference between this embodiment and Embodiment 1 is that the pH of the first raffinate is controlled at 1.5, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0111] Example 15

[0112] The only difference between this embodiment and Embodiment 1 is that the pH of the first raffinate is controlled at 2.5, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0113] Example 16

[0114] The only difference between this embodiment and Embodiment 1 is that the pH of the second raffinate is controlled at 2, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0115] Example 17

[0116] The only difference between this embodiment and Embodiment 1 is that the pH of the second raffinate is controlled at 3.5; all other conditions and parameters are exactly the same as in Embodiment 1.

[0117] Example 18

[0118] The only difference between this embodiment and Embodiment 1 is that the pH of the third raffinate is controlled at 2, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0119] Example 19

[0120] The only difference between this embodiment and Embodiment 1 is that the pH of the second raffinate is controlled at 3, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0121] Performance testing:

[0122] The purity of the various rare earth oxides obtained in the above embodiments was tested, and the test results are shown in Table 1:

[0123] Table 1

[0124]

[0125]

[0126] As shown in Table 1, and as demonstrated in Examples 1-19, in the comprehensive recycling method for NdFeB permanent magnet waste described in this invention, the concentration of the extractant in the extraction system affects the extraction effect, which in turn affects the extraction effect of various rare earth elements, and consequently the purity of various rare earth oxides. Controlling the molar concentration of C272 in the extraction system used for the first extraction treatment to 0.8 mol / L–1.2 mol / L, the molar concentration of P507 in the extraction system used for the second extraction treatment to 0.3 mol / L–0.7 mol / L, the molar concentration of P229 in the extraction system used for the third extraction treatment to 0.8 mol / L–1.2 mol / L, and the molar concentration of P204 in the extraction system used for the fourth extraction treatment to 0.8 mol / L–1.2 mol / L, results in better extraction effects for the corresponding rare earth elements. This method achieves efficient and sequential separation of rare earth elements from NdFeB waste, promotes the development of rare earth recycling technology, and the obtained rare earth oxides meet the 4N purity standard.

[0127] A comparison of Examples 1 and 4-11 shows that in the comprehensive recycling method for NdFeB permanent magnet waste described in this invention, the concentration of the extractant in the extraction system affects the extraction effect, which in turn affects the extraction effect of various rare earth elements, and consequently affects the purity of various rare earth oxides. The molar concentration of C272 in the extraction system used for the first extraction treatment is controlled at 0.8 mol / L to 1.2 mol / L; the molar concentration of P507 in the extraction system used for the second extraction treatment is controlled at 0.3 mol / L to 0.7 mol / L; and the molar concentration of P229 in the extraction system used for the third extraction treatment is controlled at... The concentration of P2O4 in the extraction system used in the fourth extraction process is controlled between 0.8 mol / L and 1.2 mol / L. This ensures good extraction of the corresponding rare earth elements and does not affect subsequent extractions. If the concentration of the extractant used in a certain extraction step is too low, the corresponding rare earth elements will not be completely extracted, resulting in unextracted rare earth elements in the rare earth oxides extracted later, leading to a significant decrease in purity. If the concentration of the extractant used in a certain extraction step is too high, other rare earth elements will be doped into the obtained rare earth oxides, resulting in a decrease in purity.

[0128] A comparison of Examples 1 and 12-19 shows that in the comprehensive recycling method for NdFeB permanent magnet waste described in this invention, the pH of the solutions (rare earth salt solution and raffinate obtained in each step) affects the extraction effect. Controlling the pH of the rare earth salt solution to 1-1.5, the pH of the first raffinate to 1.8-2.2, the pH of the second raffinate to 2.5-3, and the pH of the third raffinate to 2.2-2.8 improves the extraction effect. If the pH is too low, H... + High concentrations decrease rare earth extraction rates; if the pH is too high, OH... - Increased concentration leads to the formation of hydroxides, which can cause organic emulsification and make it difficult for the organic and liquid materials to separate, thus affecting the efficiency of rare earth separation.

[0129] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A comprehensive recycling method for neodymium iron boron permanent magnet waste, characterized in that, The comprehensive recycling method includes the following steps: The waste NdFeB permanent magnets were subjected to acidification and impurity removal treatment to obtain a rare earth salt solution. The rare earth salt solution was subjected to a first extraction treatment to obtain the extracted Ho organic phase and the first extraction residue. The extracted Ho organic phase was subjected to a first back-extraction treatment and oxalic acid precipitation treatment to obtain Ho2(C2O4)3. The first raffinate was subjected to a second extraction treatment to obtain the Dy organic phase and the second raffinate. The Dy organic phase was subjected to a second back-extraction treatment and oxalic acid precipitation to obtain Dy2(C2O4)3. The second raffinate was subjected to a third extraction treatment to obtain the extracted Gd organic phase and the third raffinate. The extracted Gd organic phase was subjected to a third back-extraction treatment and oxalic acid precipitation of Gd to obtain Gd2(C2O4)3. The third raffinate was subjected to a fourth extraction treatment to obtain the Nd organic phase and the fourth raffinate. The Nd organic phase was subjected to a fourth back-extraction treatment and Nd precipitation with oxalic acid to obtain Nd2(C2O4)3. The fourth raffinate was treated with oxalic acid to precipitate Pr, yielding Pr2(C2O4)3.

2. The comprehensive recycling method as described in claim 1, characterized in that, The acid solution used in the acidification and impurity removal treatment includes any one or a combination of at least two of hydrochloric acid, nitric acid, or sulfuric acid. Preferably, the pH of the acid solution is 1.5 to 2.5; Preferably, the mass-to-volume ratio of the acid solution to the NdFeB permanent magnet waste is (8-12):

1.

3. The comprehensive recycling method as described in claim 1 or 2, characterized in that, The pH of the rare earth salt solution is 1 to 1.5; Preferably, the metal elements in the rare earth salt solution include Nd, Pr, Gd, Dy, and Ho.

4. The comprehensive recycling method according to any one of claims 1-3, characterized in that, The extraction system used in the first extraction process includes an extractant and a diluent; Preferably, the extractant used in the first extraction process includes C272 extractant; Preferably, the diluent used in the first extraction process includes sulfonated kerosene; Preferably, the molar concentration of the extractant in the extraction system used in the first extraction treatment is 0.8 mol / L to 1.2 mol / L; Preferably, the number of extraction stages in the first extraction process is 10 to 20.

5. The comprehensive recycling method according to any one of claims 1-4, characterized in that, The pH of the first raffinate is 1.8–2.2; Preferably, the extraction system used in the second extraction process includes an extractant and a diluent; Preferably, the extractant used in the second extraction process includes P507 extractant; Preferably, the diluent used in the second extraction process includes sulfonated kerosene; Preferably, the molar concentration of the extractant in the extraction system used in the second extraction treatment is 0.3 mol / L to 0.7 mol / L; Preferably, the number of extraction stages in the second extraction process is 18 to 25.

6. The comprehensive recycling method according to any one of claims 1-5, characterized in that, The pH of the second raffinate is 2.5–3; Preferably, the extraction system used in the third extraction process includes an extractant and a diluent; Preferably, the extractant used in the third extraction process includes P229 extractant; Preferably, the diluent used in the third extraction process includes sulfonated kerosene; Preferably, the molar concentration of the extractant in the extraction system used in the third extraction process is 0.8 mol / L to 1.2 mol / L; Preferably, the third extraction process has 12 to 18 extraction stages.

7. The comprehensive recycling method according to any one of claims 1-6, characterized in that, The pH of the third raffinate is 2.2–2.8; Preferably, the extraction system used in the fourth extraction process includes an extractant and a diluent; Preferably, the extractant used in the fourth extraction process includes P204 extractant; Preferably, the diluent used in the fourth extraction process includes sulfonated kerosene; Preferably, the molar concentration of the extractant in the extraction system used in the fourth extraction process is 0.8 mol / L to 1.2 mol / L; Preferably, the fourth extraction process has 60 to 80 extraction stages.

8. The integrated recycling method according to any one of claims 1-7, characterized in that, The stripping agents used in the first stripping treatment, the second stripping treatment, the third stripping treatment and the fourth stripping treatment independently include any one or a combination of at least two of hydrochloric acid, nitric acid or sulfuric acid; Preferably, the mass concentration of the back-extraction agent is 1 mol / L to 6 mol / L.

9. The integrated recycling method according to any one of claims 1-8, characterized in that, The oxalic acid concentration used in the oxalic acid precipitation Ho treatment, oxalic acid precipitation Dy treatment, oxalic acid precipitation Gd treatment, oxalic acid precipitation Nd treatment, and oxalic acid precipitation Pr treatment is 0.05 mol / L to 0.3 mol / L.

10. The integrated recycling method according to any one of claims 1-9, characterized in that, The oxalic acid Ho precipitation treatment, oxalic acid Dy precipitation treatment, oxalic acid Gd precipitation treatment, oxalic acid Nd precipitation treatment and oxalic acid Pr precipitation treatment were then independently calcined to obtain oxides. Preferably, the roasting temperature is independently 600℃~900℃.

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