Method for preparing regenerated magnetic powder from neodymium iron boron oil sludge waste based on reduction diffusion technology

Abstract

The invention discloses a method for preparing regenerated magnetic powder from neodymium-iron-boron oil sludge waste on the basis of a reduction diffusion technology. The method comprises the following steps that firstly, the neodymium-iron-boron oil sludge waste is pretreated; 2, acid dissolution of the neodymium iron boron oil sludge fine powder; step 3, drying the acidolysis solution; and 4, reduction diffusion. According to the method, particle refinement and primary impurity removal of the iron-boron oil sludge waste are achieved through ball milling and screening, the proportion of Fe, RE and B elements in a pickling solution is controlled through acid dissolution and element adjustment, and then mixed chloride fine powder with accurate components and uniform main phase elements is obtained directly through heating, stirring and evaporation drying; and then the RE2Fe14B regenerated magnetic powder with uniformly distributed phase and neodymium-rich phase is obtained through a reduction diffusion reaction, so that the recovery process of the neodymium-iron-boron oil sludge waste is remarkably shortened, the recovery cost is reduced, and the method is suitable for recycling the neodymium-iron-boron oil sludge waste.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet waste recycling technology, and in particular relates to a method for preparing regenerated magnetic powder from neodymium iron boron sludge waste based on reduction diffusion technology. Background Technology

[0002] Neodymium iron boron (NdFeB) permanent magnets are the third generation of rare-earth permanent magnets and are the most widely used. They exhibit excellent performance in magnetic properties such as intrinsic coercivity, energy product, and remanence, making them the undisputed "king of magnets." To meet the size and shape requirements of various technological fields, the processing of NdFeB magnets generates a large amount of waste, of which 30% is oily sludge containing high abundance of rare earth elements and other valuable elements. my country generates tens of thousands of tons of NdFeB oily sludge waste annually, representing a valuable secondary resource. The development of efficient recycling technologies can prevent the waste of rare earth resources.

[0003] Currently, although hydrometallurgical technology has been industrialized in the recycling of NdFeB sludge waste, its inherent problems, such as long process time, high acid and alkali consumption, and severe environmental pollution, have prompted the industry to actively develop new, greener, and more efficient recycling processes. The development of a technology for recycling NdFeB sludge waste based on a calcium thermal reduction diffusion process achieves efficient recycling of sludge waste and regeneration of NdFeB magnetic powder, and is shorter and more environmentally friendly than hydrometallurgical technology.

[0004] The reduction-diffusion precursor of this recycling technology is typically obtained through mechanical mixing of recovered rare earth / iron mixed oxides, a reducing agent, and supplemented rare earth / boron compounds. However, mechanical mixing cannot produce a sufficiently uniform reduction-diffusion precursor, especially with the addition of a very small amount of rare earth / boron compounds, which further exacerbates the inhomogeneity of the precursor, leading to Nd₂Fe 14 The uneven distribution of the B phase or neodymium-rich phase affects the magnetic properties of the regenerated magnetic powder. Furthermore, this process suffers from significant challenges, including complex rare earth / iron element extraction, difficulty in precisely controlling the main phase element ratio, and incomplete recovery of useful elements. In addition, the high requirements for sludge pretreatment, the complex processes, and the high cost also present problems with this technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology. This method utilizes ball milling and sieving to achieve particle refinement and preliminary impurity removal. The proportions of Fe, RE, and B elements in the pickling solution are controlled through acid dissolution and elemental adjustment. Then, a fine mixed chloride powder with precise composition and uniform main phase elements is obtained directly by heating, stirring, and evaporation. Subsequently, a reduction diffusion reaction yields RE2Fe with uniformly distributed phases and NdFeB-rich phases. 14B-type regenerated magnetic powder significantly shortens the recycling process of NdFeB sludge waste, reduces recycling costs, and solves the problems of uneven element distribution and difficulty in precise control of the ratio of reduction diffusion precursors in existing technologies.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology, characterized in that the method includes the following steps: Step 1: Pretreatment of NdFeB sludge waste: Add anhydrous ethanol to the NdFeB sludge waste and ball mill it, then sieve, centrifuge and dry it in sequence to obtain NdFeB sludge fine powder. Step 2: Acid dissolution of NdFeB oil sludge fine powder: Add excess hydrochloric acid to the NdFeB oil sludge fine powder obtained in Step 1 for acid dissolution. After the NdFeB oil sludge fine powder is completely dissolved, filter out the acid hydrolysate for elemental analysis, and use soluble rare earth salts and boric acid to adjust the element ratio in the acid hydrolysate. The elements include Fe, RE, and B, where RE is a rare earth element. Step 3, drying of acid hydrolysate: The acid hydrolysate after adjusting the element ratio in step 2 is heated and stirred and evaporated to a paste-like state, and then dried to obtain mixed chloride fine powder; Step 4, Reduction Diffusion: The mixed chloride powder obtained in Step 3 is mixed evenly with calcium hydride and potassium chloride in a mortar, and then a reduction diffusion reaction is carried out under an argon atmosphere to obtain RE2Fe. 14 B. Regenerated magnetic powder.

[0007] This invention evaporates most of the liquid in the acid hydrolysate by heating and stirring, and completes the element adjustment. The heating and stirring are continued until all the solute in the acid hydrolysate precipitates into a paste, so that the elements are evenly distributed. Since there is still a small amount of liquid in the paste, it is then dried to obtain a mixed dry powder. Compared with direct drying, this method can avoid uneven mixing of the added rare earth elements with other elements in the sludge.

[0008] The above-mentioned method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology is characterized in that the ball milling parameters in step one are: rotation speed 300 r / min~400 r / min, time 12h~36h, and the mass ratio of NdFeB sludge waste, anhydrous ethanol, and milling balls is 1:0.7~1.2:10~15; the particle size of the NdFeB sludge fine powder is not greater than 30 μm.

[0009] This invention uses anhydrous ethanol as a medium for ball milling, which enables NdFeB sludge waste to simultaneously undergo particle refinement and preliminary impurity removal, thereby promoting the subsequent acid dissolution reaction and reducing the impurity content in the acid hydrolysate.

[0010] The above-mentioned method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology is characterized in that the concentration of excess hydrochloric acid in step two is 4 mol / L to 6 mol / L, and the acid dissolution temperature is 60℃ to 80℃.

[0011] This invention controls the size of NdFeB sludge fine powder to be no greater than 30μm after ball milling and sieving. The fine powder can be completely dissolved by using excess hydrochloric acid of 4mol / L to 6mol / L. By setting the acid dissolution temperature to 60℃ to 80℃, a suitable acid dissolution rate can be ensured, avoiding the slow acid dissolution rate caused by temperatures below 60℃ and the violent acid dissolution reaction and increased volatilization loss of hydrochloric acid caused by temperatures above 80℃.

[0012] The above-mentioned method for preparing regenerated magnetic powder from neodymium iron boron sludge waste based on reduction diffusion technology is characterized in that, in step two, the molar ratio of Fe, RE, and B elements in the acid hydrolysis solution after adjusting the element ratio is 14:2.3~2.5:1.00~1.05, the soluble rare earth salt is one or more of nitrates and hydrates containing RE elements, and chlorides and hydrates containing RE elements, and the RE elements are selected from neodymium, praseodymium, dysprosium, terbium, and cerium.

[0013] This invention determines the molar ratio of Fe, RE, and B in the acid hydrolysate by performing elemental analysis, and combines this with RE₂Fe 14 Factors such as the atomic ratio of elements in B and the volatilization of rare earth elements during reduction and diffusion are considered. Adding a certain amount of soluble rare earth salts and boric acid to the acid hydrolysis solution adjusts the molar ratio of Fe, RE, and B to 14:2.3~2.5:1.00~1.05, ensuring that RE₂Fe 14 B ensures stable phase formation and avoids the formation of impurity phases; it also avoids the formation of α-Fe phase when the molar amount of rare earth elements is below 2.3, and the presence of excessive neodymium-rich phase when the molar amount of rare earth elements is above 2.5.

[0014] The above-mentioned method for preparing regenerated magnetic powder from neodymium iron boron sludge waste based on reduction diffusion technology is characterized in that the heating temperature in step three is 60℃~80℃.

[0015] This invention controls the precipitation rate of chloride salts in the acid hydrolysate by adjusting the heating temperature of the acid hydrolysate. This avoids excessively high temperatures that cause hydrochloric acid to volatilize rapidly and easily precipitate hydroxides, which is detrimental to subsequent operations, while excessively low temperatures reduce the evaporation efficiency.

[0016] The above-mentioned method for preparing regenerated magnetic powder from neodymium iron boron sludge waste based on reduction diffusion technology is characterized in that the drying temperature in step three is 80℃~120℃ and the drying time is 48h~72h.

[0017] The above-mentioned method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology is characterized in that, in step four, the mass of calcium hydride is 200% to 350% of the mass of the mixed chloride fine powder, and the mass of potassium chloride is 5% to 15% of the mass of calcium hydride.

[0018] This invention, by using calcium hydride as a reducing agent and setting the mass of calcium hydride to 200%~350% of the mass of the mixed chloride fine powder, ensures the full progress of the reduction diffusion reaction, thereby obtaining RE2Fe. 14 B. Pure phase product; avoid concentrations below 200%, which could lead to incomplete reduction of the mixed chloride fine powder and affect RE2Fe. 14 B is stable and readily forms the α-Fe phase; avoid concentrations above 350%, which can lead to RE2Fe formation. 14 Product B is too hard and is not easy to grind, crush, or wash to remove impurities. By using potassium chloride as a flux and setting its mass to 5%–15% of the mass of calcium hydride, the utilization rate of the reducing agent can be enhanced while ensuring a complete reaction. A concentration below 5% is insufficient to improve the utilization rate of the reducing agent and fails to significantly reduce the amount of reducing agent required; a concentration above 15% leads to incomplete reduction and affects the RE2Fe2O3 reaction. 14 Product B is stable and forms a phase.

[0019] The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology is characterized in that the flow rate of argon gas in the argon atmosphere in step four is 0.1 L / min to 0.3 L / min.

[0020] The above-mentioned method for preparing regenerated magnetic powder from neodymium iron boron sludge waste based on reduction diffusion technology is characterized in that the reduction diffusion reaction in step four is carried out by heating to 950℃~1050℃ at a rate of 2℃ / min~5℃ / min and holding at that temperature for 4h~6h.

[0021] This invention ensures that the reduction diffusion reaction of mixed chloride fine powder is complete and stably generates RE2Fe by controlling the heating rate, temperature, and holding time of the reduction diffusion process. 14 Phase B; avoid improper heating rate, reaction temperature, and holding time that could lead to RE2Fe 14 B. The regenerated magnetic powder contains a large number of impurity phases, or the grains are coarsened and the distribution of neodymium-rich phases is uneven due to excessive sintering.

[0022] The above-mentioned method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology is characterized in that, after the reduction diffusion reaction in step four is completed, ultrasonic washing and vacuum drying at 60°C are performed.

[0023] This invention involves the reaction of RE2Fe after a reduction-diffusion reaction.14 B. Regenerated magnetic powder is ultrasonically washed to remove byproducts such as CaO, CaCl2, and KCl, thereby improving purity.

[0024] Compared with the prior art, the present invention has the following advantages: 1. This invention, through acid hydrolysis solution composition analysis, adds soluble rare earth salts and boric acid to adjust the proportions of Fe, RE, and B elements, and then evaporates to dryness, ensuring a precise ratio of main phase elements and uniform micro-mixing of the reduction-diffusion precursor. This avoids the uneven mixing of main phase elements caused by macro-mixing in traditional powder mixing techniques, thus preventing Nd2Fe from being affected by uneven mixing. 14 Uneven distribution of B-phase and rare earth-rich phase.

[0025] 2. This invention obtains a reduction diffusion precursor—mixed chloride fine powder—by heating, stirring, and evaporating the acid hydrolysate. On the one hand, it avoids the cumbersome process and chemical reagent consumption caused by the stepwise precipitation of rare earth and iron elements using chemical precipitants in traditional processes. On the other hand, it ensures the complete recovery and utilization of rare earth, iron, and boron, avoiding insufficient precipitation of rare earth and iron elements and the waste of boron elements and environmental pollution caused by boron waste residue. It also ensures the recovery and utilization of valuable elements such as cobalt in the raw material sludge.

[0026] 3. This invention effectively removes impurities from NdFeB sludge waste by pre-treating the NdFeB sludge waste and acid dissolving the fine NdFeB sludge powder, while ensuring the universality and adjustability of the process flow. Then, a precisely proportioned and highly uniform reduction-diffusion precursor is obtained by drying the acid hydrolysate, and a uniformly phased regenerated magnetic powder is obtained by reduction-diffusion. The overall process is simple, short, and cost-effective, and there are no other high-energy-consuming processes except for the reduction-diffusion process.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 The Nd2Fe obtained in Example 1 of this invention 14 XRD pattern of B regenerated magnetic powder.

[0029] Figure 2 The Nd2Fe obtained in Example 1 of this invention 14 Microstructure diagram of B regenerated magnetic powder.

[0030] Figure 3 The (Nd,Pr)2Fe obtained in Example 2 of this invention 14 XRD pattern of B regenerated magnetic powder.

[0031] Figure 4 The (Nd,Ce,Dy)2Fe obtained in Example 3 of this invention14 XRD pattern of B regenerated magnetic powder. Detailed Implementation

[0032] Example 1 The method in this embodiment includes the following steps: Step 1: Pretreatment of NdFeB sludge waste: NdFeB sludge waste, anhydrous ethanol, and grinding balls are added to a ball mill jar at a mass ratio of 1:0.7:10 and ball milled at 300 r / min for 36 h. Then, the mixture is sieved through a 500 mesh sieve, centrifuged, and vacuum dried at 60℃ to obtain NdFeB sludge fine powder. Step 2: Acid dissolution of NdFeB sludge powder: Take 8g of the NdFeB sludge powder obtained in Step 1, add 50mL of 4mol / L hydrochloric acid, and place it in a 60℃ water bath with stirring to dissolve. After the NdFeB sludge powder is completely dissolved, filter out the acid hydrolysate for ICP (inductively coupled plasma atomic emission spectrometry) component analysis. The results are shown in Table 1. Add 1.10g of Nd(NO3) to the acid hydrolysate. 3· Dissolve 6H2O and 0.09g of H3BO3 completely, and adjust the molar ratio of Fe, RE, and B elements in the acid hydrolysis solution to 14:2.3:1.0; Step 3, drying of acid hydrolysate: The acid hydrolysate after adjusting the element ratio in step 2 is placed in a 60℃ water bath and stirred and evaporated to a paste state. Then it is placed in an 80℃ oven and dried for 72 hours to obtain mixed chloride fine powder. Step 4, Reduction and Diffusion: Weigh 5g of the mixed chloride fine powder obtained in Step 3, mix it evenly with 10g of calcium hydride powder and 0.5g of potassium chloride granules in an agate mortar, place the mixture in a stainless steel crucible and put it in a tube furnace, introduce argon gas at a flow rate of 0.1L / min, heat to 950℃ at a rate of 2℃ / min and hold for 6h, cool, and then perform multiple ultrasonic washes with water as the medium to remove byproducts, obtaining Nd2Fe 14 B. Regenerated magnetic powder.

[0033] Table 1. Main phase elemental composition analysis results of the acid hydrolysate after filtration in Example 1

[0034] Regarding Nd2Fe in this embodiment 14 XRD analysis of B regenerated magnetic powder yielded the following results: Figure 1 As shown, this Nd2Fe 14 The main component of B-regenerated magnetic powder is Nd2Fe. 14 B; Regarding the Nd2Fe 14 Microstructural analysis of B-regenerated magnetic powder, such as Figure 2 As shown, this Nd2Fe 14 B. The regenerated magnetic powder has high particle uniformity and sphericity.

[0035] Example 2 The method in this embodiment includes the following steps: Step 1: Pretreatment of NdFeB sludge waste: NdFeB sludge waste, anhydrous ethanol, and grinding balls are added to a ball mill jar at a mass ratio of 1:1.2:15 and ball milled at 400 r / min for 12 h. Then, the mixture is sieved through a 500 mesh sieve, centrifuged, and then vacuum dried at 60℃ to obtain NdFeB sludge fine powder. Step 2: Acid dissolution of NdFeB sludge powder: Take 8g of NdFeB sludge powder obtained in Step 1, add 40mL of 6mol / L hydrochloric acid, and place in an 80℃ water bath with stirring to dissolve. After the NdFeB sludge powder is completely dissolved, filter out the acid hydrolysate for ICP analysis, and then add 1.62g of Pr(NO3) to the acid hydrolysate. 3· 6H₂O, 1.62g of Nd(NO₃) 3· 6H2O and 0.11g of H3BO3 were dissolved completely, and the molar ratio of Fe, RE and B elements in the acid hydrolysis solution was adjusted to 14:2.5:1.05; Step 3, drying of acid hydrolysate: The acid hydrolysate after adjusting the element ratio in step 2 is placed in an 80℃ water bath and stirred and evaporated to a paste state. Then it is placed in a 120℃ oven and dried for 48 hours to obtain mixed chloride fine powder. Step 4, Reduction Diffusion: Weigh 5g of the mixed chloride fine powder obtained in Step 3, mix it evenly with 17.5g of calcium hydride powder and 2.63g of potassium chloride granules in an agate mortar, place the mixture in a stainless steel crucible and put it in a tube furnace, introduce argon gas at a flow rate of 0.3L / min, heat to 1050℃ at a rate of 5℃ / min and hold for 4h, cool, and then perform multiple ultrasonic washes with water as the medium to remove byproducts, obtaining (Nd,Pr)2Fe 14 B. Regenerated magnetic powder.

[0036] For (Nd,Pr)2Fe in this embodiment 14 XRD analysis of B regenerated magnetic powder yielded the following results: Figure 3 As shown, the (Nd,Pr)2Fe 14 The diffraction peaks of the main phase of B regenerated magnetic powder conform to Nd2Fe. 14 B crystal structure.

[0037] Example 3 The method in this embodiment includes the following steps: Step 1: Pretreatment of NdFeB sludge waste: Add NdFeB sludge waste, anhydrous ethanol, and grinding balls to a ball mill jar at a mass ratio of 1:1.0:12 and ball mill at 350 r / min for 24 h. Then, sieve the waste through a 500 mesh screen, centrifuge, and vacuum dry at 60℃ to obtain NdFeB sludge fine powder. Step 2: Acid dissolution of NdFeB sludge powder: Take 8g of NdFeB sludge powder obtained in Step 1, add 50mL of 5mol / L hydrochloric acid, and place it in a 70℃ water bath with stirring to dissolve. After the NdFeB sludge powder is completely dissolved, filter out the acid hydrolysate for ICP analysis, and then add 0.73g of Nd(NO3) to the acid hydrolysate. 3· 6H₂O, 0.73g of Ce(NO₃) 3· 6H₂O, 0.73g of Dy(NO₃) 3· 6H2O and 0.11g of H3BO3 were fully dissolved, and the molar ratio of Fe, RE and B elements in the acid hydrolysis solution was adjusted to 14:2.4:1.05; Step 3, drying of acid hydrolysate: The acid hydrolysate after adjusting the element ratio in step 2 is placed in a 70℃ water bath and stirred and evaporated to a paste state. Then it is placed in a 100℃ oven and dried for 60 hours to obtain mixed chloride fine powder. Step 4, Reduction and Diffusion: Weigh 5g of the mixed chloride fine powder obtained in Step 3, mix it evenly with 15g of calcium hydride powder and 1.5g of potassium chloride granules in an agate mortar, place the mixture in a stainless steel crucible and put it in a tube furnace, introduce argon gas at a flow rate of 0.2L / min, heat to 1000℃ at a rate of 3℃ / min and hold for 5h, cool, and then perform multiple ultrasonic washes with water as the medium to remove byproducts, obtaining (Nd,Ce,Dy)2Fe 14 B. Regenerated magnetic powder.

[0038] For (Nd,Ce,Dy)2Fe in this embodiment 14 XRD analysis of B regenerated magnetic powder yielded the following results: Figure 4 As shown, the (Nd,Ce,Dy)2Fe 14 The diffraction peaks of the main phase of B regenerated magnetic powder conform to Nd2Fe. 14 B crystal structure.

[0039] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology, characterized in that, The method includes the following steps: Step 1: Pretreatment of NdFeB sludge waste: Add anhydrous ethanol to the NdFeB sludge waste and ball mill it, then sieve, centrifuge and dry it in sequence to obtain NdFeB sludge fine powder. Step 2: Acid dissolution of NdFeB oil sludge fine powder: Add excess hydrochloric acid to the NdFeB oil sludge fine powder obtained in Step 1 for acid dissolution. After the NdFeB oil sludge fine powder is completely dissolved, filter out the acid hydrolysate for elemental analysis, and use soluble rare earth salts and boric acid to adjust the element ratio in the acid hydrolysate. The elements include Fe, RE, and B, where RE is a rare earth element. Step 3, drying of acid hydrolysate: The acid hydrolysate after adjusting the element ratio in step 2 is heated and stirred and evaporated to a paste-like state, and then dried to obtain mixed chloride fine powder; Step 4, Reduction Diffusion: The mixed chloride powder obtained in Step 3 is mixed evenly with calcium hydride and potassium chloride in a mortar, and then a reduction diffusion reaction is carried out under an argon atmosphere to obtain RE2Fe. 14 B. Regenerated magnetic powder.

2. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, The parameters for ball milling in step one are: rotation speed 300 r / min~400 r / min, time 12h~36h, and the mass ratio of NdFeB oil sludge waste, anhydrous ethanol, and grinding balls is 1:0.7~1.2:10~15; the particle size of the NdFeB oil sludge fine powder is not greater than 30μm.

3. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, The concentration of hydrochloric acid in step two is 4 mol / L to 6 mol / L, and the acid dissolution temperature is 60℃ to 80℃.

4. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, In step two, after adjusting the element ratio, the molar ratio of Fe, RE, and B in the acid hydrolysis solution is 14:2.3~2.5:1.00~1.

05. The soluble rare earth salt is one or more of the following: nitrates containing RE and their hydrates, and chlorides containing RE and their hydrates. The RE element is selected from neodymium, praseodymium, dysprosium, terbium, and cerium.

5. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, The heating temperature in step three is 60℃~80℃.

6. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, The drying temperature in step three is 80℃~120℃, and the drying time is 48h~72h.

7. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, In step four, the mass of calcium hydride is 200% to 350% of the mass of the mixed chloride fine powder, and the mass of potassium chloride is 5% to 15% of the mass of calcium hydride.

8. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, In step four, the flow rate of argon gas in the argon atmosphere is 0.1 L / min to 0.3 L / min.

9. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, The reduction diffusion reaction procedure described in step four is as follows: the temperature is increased to 950℃~1050℃ at a rate of 2℃ / min~5℃ / min, and held at that temperature for 4h~6h.

10. The method for preparing regenerated magnetic powder from NdFeB sludge waste based on reduction diffusion technology according to claim 1, characterized in that, After the reduction-diffusion reaction described in step four is completed, ultrasonic washing and vacuum drying at 60°C are performed.

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