Method for recovering rare earth elements in neodymium iron boron waste

Abstract

The invention provides a method for recovering rare earth elements in neodymium iron boron waste, which comprises the following steps: S1, adding the neodymium iron boron waste into an oxidation acid solution to obtain an oxidation acid leaching solution; s2, alkali is added into the oxidized pickle liquor to adjust the pH value, then a composite extraction agent is used for extraction treatment, and liquid separation is conducted to obtain raffinate and a loaded organic phase; s3, carrying out first back extraction treatment on the loaded organic phase by using a first hydrochloric acid solution; s4, carrying out second back extraction treatment on the first back extraction raffinate by using a second hydrochloric acid solution; s5, carrying out third back extraction treatment on the second back extraction raffinate by using a third hydrochloric acid solution; wherein the concentration c1 of the first hydrochloric acid solution, the concentration c2 of the second hydrochloric acid solution and the concentration c3 of the third hydrochloric acid solution meet the following condition: c1 < c2 < c3. The rare earth element-containing strip liquor obtained by the method is low in impurity content and can be used for preparing rare earth oxide with relatively high purity.

Description

Technical Field

[0001] The present application belongs to the field of rare earth recovery technology, and specifically relates to a method for recovering rare earth elements from NdFeB waste. Background Art

[0002] With the rapid development of science and technology, NdFeB magnets are widely used in mobile phones, headphones, computer hard disks and other electronic devices due to their excellent magnetic properties. The rapid replacement speed has led to an increase in the amount of NdFeB magnet waste year by year. In addition, a large amount of magnet waste is also generated during the production and processing of NdFeB magnets, especially water-abrasives and material heads, which have less impurities and are of great recycling value. At present, the methods for extracting rare earths from NdFeB waste mainly include hydrochloric acid complete dissolution method, hydrochloric acid partial dissolution method, sulfuric acid double salt method, etc., and then the leaching solution is precipitated step by step to obtain rare earth precipitates. However, there are disadvantages such as long process and high impurity content of rare earth precipitates, which require further purification.

[0003] Therefore, it is necessary to provide a recovery method for separating rare earth elements from other impurity elements in NdFeB waste. Summary of the invention

[0004] In view of this, the present application provides a method for recovering rare earth elements in NdFeB waste, which can effectively recover rare earth elements in NdFeB waste and separate rare earth elements from other impurity elements.

[0005] In a first aspect, the present application provides a method for recovering rare earth elements from NdFeB waste, comprising the following steps: Step S1: adding the NdFeB waste into an oxidizing acid solution to dissolve the NdFeB waste in the 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 using a composite extractant, so that the metal elements in the oxidizing acid leaching solution are extracted into the composite extractant, and the raffinate and the loaded organic phase are separated; Step S3: using a first hydrochloric acid solution to perform a first stripping treatment on the loaded organic phase, so that the Ni, Co, and Mn elements in the loaded organic phase are stripped into the first hydrochloric acid solution, and the liquids are separated to obtain a first stripping raffinate and a stripping solution containing Ni, Co, and Mn; the concentration c1 of the first hydrochloric acid solution is 0.21-1.16 g / L; Step S4: using a second hydrochloric acid solution to perform a second stripping treatment on the first stripping raffinate, so that the Fe element in the first stripping raffinate is stripped into the second hydrochloric acid solution, and the liquids are separated to obtain a second stripping raffinate and an Fe-containing stripping solution; Step S5: Perform a third back-extraction treatment on the second back-extraction raffinate with a third hydrochloric acid solution, so that the rare earth elements in the second raffinate are back-extracted into the third hydrochloric acid solution, and liquid separation is performed to obtain a third back-extraction raffinate and a rare earth element-containing back-extracted solution; wherein, the concentration c1 of the first hydrochloric acid solution, the concentration c2 of the second hydrochloric acid solution, and the concentration c3 of the third hydrochloric acid solution satisfy: c1 < c2 < c3.

[0006] According to the present application, based on the hydrochloric acid total dissolution method, all metal elements in the neodymium iron boron waste are dissolved in the oxidizing acid solution. After adjusting the pH with alkali, a composite extractant is used to extract the metal elements into the organic phase, and then different hydrochloric acid solutions are used for staged back-extraction of the loaded organic phase. In different back-extraction stages, rare earth elements are fully separated from other impurity metal elements. The impurity content in the obtained rare earth element-containing back-extracted solution is low and can be used to prepare rare earth oxides with higher purity.

[0007] In some embodiments, in step S1, the particle fineness of the neodymium iron boron waste is 250 - 325 mesh.

[0008] In some embodiments, in step S1, the oxidizing acid solution includes hydrochloric acid and hydrogen peroxide, wherein the concentration of hydrochloric acid is 90 - 105 g / L, and the concentration of hydrogen peroxide is 10 - 30 g / L.

[0009] In some embodiments, in step S1, the solid-liquid ratio of the neodymium iron boron waste to the oxidizing acid solution is 1:5 - 15.

[0010] In some embodiments, in step S2, the specific operation of adjusting the pH of the oxidized acid leaching solution with alkali includes: adding an aqueous sodium hydroxide solution to make the pH of the solution 10 - 11.

[0011] In some embodiments, in step S2, the composite extractant includes N,N-dioctyldiglycol amide acid (DODGAA), P507-Ni, and kerosene, and the volume ratio of N,N-dioctyldiglycol amide acid, P507-Ni, and kerosene is 2 - 4:1:5 - 7.

[0012] In some embodiments, in step S2, the phase ratio of the composite extractant to the diluted oxidized acid leaching solution is 0.8 - 1.5:1.

[0013] In some embodiments, in step S3, the phase ratio of the first hydrochloric acid solution to the loaded organic phase is 0.8 - 1.5:1.

[0014] In some embodiments, in step S4, the concentration c2 of the second hydrochloric acid solution is 1.2 - 20 g / L.

[0015] In some embodiments, in step S4, the volume ratio of the second hydrochloric acid solution to the loaded organic phase is 0.8~1.5:1.

[0016] In some embodiments, in step S5, the concentration c3 of the third hydrochloric acid solution is 21.1~36.5 g / L.

[0017] In some embodiments, in step S5, the volume ratio of the third hydrochloric acid solution to the loaded organic phase is 0.8~1.5:1.

[0018] In some embodiments, the method further includes: Step S6: Adding a precipitant to the rare earth element stripping solution to cause the rare earth elements to react with the precipitant to precipitate, obtaining a rare earth element precipitate; Step S7: Calcining the rare earth element precipitate to oxidize and decompose the rare earth element precipitate to obtain rare earth oxides.

[0019] In some embodiments, in step S7, the conditions of the calcination treatment include: calcining at 800~900 °C for 0.5~2 h. In some embodiments, the method further includes: Step S8: Adjusting the pH of the raffinate in step S2 to convert the remaining Ni 2+ in the raffinate into Ni(OH)2 to obtain an aqueous boric acid solution.

[0020] In some embodiments, in step S8, sodium hydroxide is used to adjust the pH of the raffinate to 10~11. Description of the Drawings

[0021] Figure 1 It is a process flow diagram for recovering rare earth elements from neodymium-iron-boron waste in an embodiment of the present application. Detailed Embodiments

[0022] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0023] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0024] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0025] Based on the above background technology, the main problem existing in the current recovery of rare earth elements from NdFeB waste is that the impurity content in the recovered rare earth precipitate is high and further purification treatment is required for utilization. The inventors found that: the ionic radii of rare earth elements (neodymium elements) in NdFeB waste are similar to those of impurity elements such as nickel, cobalt, manganese, iron and other impurity elements, and they exist in similar valence states in aqueous solution (such as trivalent state). They have a large affinity for water and are protected by hydrates, resulting in very similar chemical properties, which further increases the difficulty of separation. This makes it very difficult to effectively distinguish them by a single chemical method during the extraction and separation process. The properties of these impurity elements may compete with rare earth elements for stripping agents or form complexes, resulting in the rare earth elements not being effectively stripped out, or the content of impurity elements in the stripping solution being too high, affecting the extraction effect.

[0026] Based on this, the present application provides a method for recovering rare earth elements from NdFeB waste, which can effectively separate rare earth elements and impurity elements and can be used to obtain rare earth precipitates with low impurity content. The technical solutions of the present application are described below through specific embodiments.

[0027] The present application provides a method for recovering rare earth elements from NdFeB waste, which can effectively recover rare earth elements from NdFeB waste and separate rare earth elements from other impurity elements.

[0028] In a first aspect, the present application provides a method for recovering rare earth elements from NdFeB waste, including the following steps: Step S1: Add NdFeB waste into an oxidizing acid solution to dissolve the NdFeB waste in the oxidizing acid solution to obtain an oxidizing acid leaching solution; Step S2: Adjust the pH of the oxidized acid leaching solution by adding alkali, and then perform extraction treatment using a composite extractant to extract metal elements in the oxidized acid leaching solution into the composite extractant, and separate the liquid to obtain a raffinate and a loaded organic phase; Step S3: Perform a first stripping treatment on the loaded organic phase using a first hydrochloric acid solution to strip Ni, Co, and Mn elements in the loaded organic phase into the first hydrochloric acid solution, and separate the liquid to obtain a first stripping raffinate and a stripping solution containing Ni, Co, and Mn; the concentration c1 of the first hydrochloric acid solution is 0.21 - 1.16 g / L; Step S4: Perform a second stripping treatment on the first raffinate using a second hydrochloric acid solution to strip Fe elements in the first raffinate into the second hydrochloric acid solution, and separate the liquid to obtain a second stripping raffinate and a stripping solution containing Fe; Step S5: Perform a third stripping treatment on the second raffinate using a third hydrochloric acid solution to strip rare earth elements in the second raffinate into the third hydrochloric acid solution, and separate the liquid to obtain a third stripping raffinate and a stripping solution containing rare earth elements; wherein, the concentration c1 of the first hydrochloric acid solution, the concentration c2 of the second hydrochloric acid solution, and the concentration c3 of the third hydrochloric acid solution satisfy: c1 < c2 < c3.

[0029] According to the present application, based on the hydrochloric acid total dissolution method, metal elements in the NdFeB waste are all dissolved in the oxidized acid solution, and after dilution, a composite extractant is used to extract the metal elements into the organic phase. Then, different hydrochloric acid solutions are used to perform staged stripping on the loaded organic phase. By limiting the concentration of the first hydrochloric acid solution and gradually increasing the concentration of the hydrochloric acid solution used for stripping treatment, the reaction activities of impurity elements and rare earth elements can be balanced, and rare earth elements can be fully separated from other impurity metal elements at different stripping stages. The impurity content in the obtained stripping solution containing rare earth elements is low and can be used to prepare rare earth oxides with higher purity.

[0030] Specifically, using the oxidized acid solution in Step S1 can fully dissolve the NdFeB waste, fix metal elements and boron elements in the oxidized acid solution, and effectively improve the recovery rate of each element in the NdFeB waste; at the same time, the oxidant in the oxidized acid solution can not only promote the dissolution of the NdFeB waste, but also oxidize low-valent metal ions to high-valent metal ions (such as Fe 2+ oxidized to Fe 3+ ), and Fe 3+ is more easily extracted by the organic extractant, thereby improving the recovery rate of some metal elements. In addition, metal elements with a single valence state are more easily separated from other elements; In Step S2, after adjusting the pH of the oxidized acid solution with alkali first, then using a composite extractant to perform extraction treatment on it. Adjusting the pH can reduce the solubility of metal elements in the solution, increase the distribution coefficient of metal elements in the composite extractant, so that metal elements are fully extracted into the composite extractant, and improve the recovery rate of metal elements; In steps S3 - S5, by taking advantage of the different distribution coefficients of different metal elements in hydrochloric acid with different concentrations and a composite extractant, a three - stage back - extraction method is used to separate different metal elements, so as to obtain a rare - earth - metal - containing back - extraction solution with a low impurity content. Specifically, using the first hydrochloric acid solution, Ni, Co, and Mn elements in the loaded organic phase can be back - extracted into the first hydrochloric acid solution; using the second hydrochloric acid solution, Fe element in the loaded organic phase can be back - extracted into the second hydrochloric acid solution; using the third hydrochloric acid solution, rare - earth elements in the loaded organic phase can be back - extracted into the third hydrochloric acid solution. It can be understood that generally, the higher the concentration of the hydrochloric acid solution, the easier it is for metal ions to be back - extracted into the hydrochloric acid solution. However, too high a hydrochloric acid concentration may cause rare - earth elements to also be back - extracted. Therefore, first, use the first hydrochloric acid solution with a lower concentration to perform the first back - extraction treatment on the loaded organic phase. By controlling the concentration of the first hydrochloric acid solution, the reaction activities of Ni, Co, and Mn elements and rare - earth elements can be balanced, realizing the selective extraction of Ni, Co, and Mn elements and reducing the influence of these elements on the subsequent recovery of rare - earth elements. Then, based on the concentration of the first hydrochloric acid solution, use the second hydrochloric acid solution with a higher concentration to perform the second back - extraction treatment on the loaded organic phase. Finally, use the third hydrochloric acid solution with a higher concentration to perform the third back - extraction treatment on the extraction solution, which can fully separate rare - earth elements from other impurity metal elements in the loaded organic phase, obtaining a rare - earth - metal - containing back - extraction solution with a low impurity content.

[0031] In some embodiments, in step S1, the particle fineness of the Nd - Fe - B waste is 250 - 325 mesh.

[0032] In the above - mentioned some embodiments, using Nd - Fe - B waste with a lower particle fineness can further promote its reaction with the oxidative acid solution, making the dissolution of the Nd - Fe - B waste more complete, thereby further improving the recovery rate of each element in the Nd - Fe - B waste.

[0033] In some embodiments, in step S1, the oxidative acid solution includes hydrochloric acid and hydrogen peroxide, wherein the concentration of hydrochloric acid is 90 - 105 g / L and the concentration of hydrogen peroxide is 10 - 30 g / L.

[0034] In the above - mentioned some embodiments, using the hydrochloric acid solution including hydrogen peroxide with the above - mentioned concentration as the oxidative acid solution can fully dissolve the Nd - Fe - B waste, thereby further improving the recovery rate of each element in the Nd - Fe - B waste. In addition, chloride ions in hydrochloric acid will not affect the extraction process and the back - extraction process, and the reduction product of hydrogen peroxide is water, which will not introduce new impurities into the system, thus reducing the impurity content in the recovered product.

[0035] In some embodiments, in step S1, the solid - liquid ratio of the Nd - Fe - B waste to the oxidative acid solution is 1:5 - 15.

[0036] In some of the above embodiments, controlling the solid-liquid ratio of the neodymium-iron-boron waste to the oxidation acid solution within the above range can make the neodymium-iron-boron waste dissolve more fully, thereby further improving the recovery rate of each element in the neodymium-iron-boron waste.

[0037] In some embodiments, in step S2, adjusting the pH of the oxidation acid leaching solution by adding alkali specifically includes: making the pH of the solution 10-11 by adding an aqueous sodium hydroxide solution. Based on the above embodiments, under these conditions, the metal elements in the oxidation acid leaching solution can be more easily extracted into the composite extractant, thereby improving the recovery rate of each element in the neodymium-iron-boron waste.

[0038] In some embodiments, in step S2, the composite extractant includes N,N-dioctyldiglycol amide acid, P507-Ni and kerosene, and the volume ratio of N,N-dioctyldiglycol amide acid, P507-Ni and kerosene is 2-4:1:5-7.

[0039] In some of the above embodiments, the composite extractant with the above composition has a good extraction effect on the metal elements in the diluted oxidation acid leaching solution, and can make the metal elements transfer more fully from the diluted oxidation acid leaching solution to the loaded organic phase, thereby further improving the recovery rate of each element in the neodymium-iron-boron waste.

[0040] In some embodiments, in step S2, the phase ratio of the composite extractant to the diluted oxidation acid leaching solution is 0.8-1.5:1. Based on the above embodiments, under these conditions, the metal elements in the oxidation acid leaching solution can be more fully extracted into the composite extractant, thereby improving the recovery rate of each element in the neodymium-iron-boron waste; an appropriate amount of the composite extractant can also reduce the subsequent recovery cost.

[0041] In some embodiments, in step S3, the concentration c1 of the first hydrochloric acid solution is 0.21-1.16 g / L.

[0042] In some of the above embodiments, when the concentration of the first hydrochloric acid solution is within the above range, the Ni, Co, and Mn elements in the loaded organic phase can be back-extracted and transferred into the first hydrochloric acid solution, thereby separating the Ni, Co, and Mn elements in the loaded organic phase from other metal elements. The obtained Ni, Co, and Mn-containing back-extraction solution can be further separated and utilized subsequently, and the first back-extraction raffinate is subjected to subsequent back-extraction treatment.

[0043] In some embodiments, in step S3, the phase ratio of the first hydrochloric acid solution to the loaded organic phase is 0.8-1.5:1.

[0044] In some embodiments, in step S4, the concentration of the second hydrochloric acid solution is 1.2-20 g / L.

[0045] In some of the above embodiments, when the concentration of the second hydrochloric acid solution is within the above range, the Fe element in the loaded organic phase can be back-extracted and transferred into the second hydrochloric acid solution, so as to separate the Fe element from other metal elements in the first back-extraction raffinate. The obtained Fe-containing back-extraction solution can be used to recover the Fe element subsequently, and the second back-extraction raffinate is subjected to subsequent back-extraction treatment.

[0046] In some embodiments, in step S4, the volume ratio of the second hydrochloric acid solution to the loaded organic phase is 0.8 - 1.5:1.

[0047] In some embodiments, in step S5, the concentration of the third hydrochloric acid solution is 21.1 - 36.5 g / L.

[0048] In some of the above embodiments, when the concentration of the third hydrochloric acid solution is within the above range, the rare earth elements in the loaded organic phase can be back-extracted and transferred into the third hydrochloric acid solution, so as to separate the rare earth elements from other metal elements in the second back-extraction raffinate. The obtained rare earth element-containing back-extraction solution has a low content of other impurity metal elements (such as Ni, Co, Mn, Fe elements, etc.) at this time, and thus can be directly used to prepare rare earth oxides with a relatively high purity.

[0049] In some embodiments, in step S5, the volume ratio of the third hydrochloric acid solution to the loaded organic phase is 0.8 - 1.5:1.

[0050] It can be understood that in the three-stage back-extraction process, specifically regarding the back-extraction and transfer of metal elements, the volume of the loaded organic phase is less affected. Therefore, the addition amounts of the three different concentrations of hydrochloric acid solutions in the three-stage back-extraction process can all be determined based on the amount of the loaded organic phase.

[0051] In some embodiments, the method further includes: Step S6: Adding a precipitant to the rare earth element-containing back-extraction solution to react the rare earth elements with the precipitant to form a rare earth element-containing precipitate; Step S7: Calcining the rare earth element-containing precipitate to oxidize and decompose the rare earth element-containing precipitate to obtain rare earth oxides.

[0052] In some of the above embodiments, high-purity rare earth oxides can be prepared from the rare earth element-containing back-extraction solution through steps S6 and S7. The rare earth elements are precipitated by the precipitant, and then high-purity rare earth oxides can be obtained through calcination treatment.

[0053] In some embodiments, the precipitant may include, but is not limited to, oxalic acid and ammonium bicarbonate.

[0054] In some embodiments, the conditions for the calcination treatment include: calcining at 800 - 900 °C for 0.5 - 2 h. As an example, the oxalate of rare earth elements after drying is heated to 850 °C and calcined for 1 h to obtain neodymium oxide. In some embodiments, the method further includes: Step S8: Adjust the pH of the raffinate in Step S2 to convert the remaining Ni 2+ in the raffinate into Ni(OH)2 to obtain an aqueous boric acid solution.

[0055] In some of the above embodiments, in the raffinate of Step S2, there is also a small amount of unextracted Ni 2+ and borate. By adjusting the pH of the raffinate, the remaining Ni 2+ in the raffinate can be converted into Ni(OH)2 precipitate to obtain an aqueous boric acid solution, thereby realizing the recycling of boron elements in the NdFeB waste.

[0056] In some embodiments, in Step S8, sodium hydroxide is used to adjust the pH of the raffinate to 10 - 11.

[0057] The solutions of the present application will be described below with reference to the following specific examples. Unless otherwise specified, the raw materials used in the following examples are all from ordinary commercially available products, and the devices or equipment used are all purchased from conventional market sales channels.

[0058] Example 1 A method for recovering rare earth elements from NdFeB waste, the process flow chart of which is as Figure 1 shown, specifically: 200 g of NdFeB waste ground through a 300 - mesh sieve is added to an oxidative acid solution of 100 g / L hydrochloric acid and 10 g / L H2O2 to completely dissolve the rare earth and metal elements. The solid - liquid ratio is 1:5. After dissolution is completed, sodium hydroxide aqueous solution is added until the pH value reaches 10 - 11. A composite extractant prepared with DODGAA, P507 - Ni, and kerosene is used for extraction. The ratio of the composite extractant to the diluted oxidative acid leaching solution is 1:1, where the volume percentages of DODGAA, P507 - Ni, and kerosene are 2:1:7. The obtained loaded organic phase is first added with 0.5 g / L hydrochloric acid with a ratio of 1:1 to the loaded organic phase to strip Ni, Co, and Mn, then added with 1.2 g / L hydrochloric acid with a ratio of 1:1 to the loaded organic phase to strip Fe, and finally added with 22 g / L hydrochloric acid with a ratio of 1:1 to the loaded organic phase to strip Pr, Nd, and Dy to obtain a rare - earth - element - containing stripping solution.

[0059] Separately, the same batch of 200 g of NdFeB waste is crushed and added to 1 L of concentrated hydrochloric acid for dissolution at room temperature. The filtrate after dissolution and filtration of the concentrated hydrochloric acid is sampled and analyzed, and it is measured that: RE (rare earth elements): 41.72 g / L.

[0060] The rare earth elements in the stripping solution containing rare earth elements were measured to be 39.22 g / L, and the impurity metal elements were measured to be 0.80 g / L. The recovery rate of rare earth elements was calculated to be 94%, and the content of impurity metal elements in the stripping solution containing rare earth elements was 2%.

[0061] Examples 2 to 27 A method for recovering rare earth elements from Nd-Fe-B waste is substantially the same as that in Example 1, except that some parameters are different. The specific differences can be seen in Table 1.

[0062] The recovery rate of rare earth elements is shown in Table 1, and the content of impurity metal elements in the stripping solution containing rare earth elements is shown in Table 1.

[0063] Comparative Example 1 A method for recovering rare earth elements from Nd-Fe-B waste is as follows: Using the double salt precipitation method, the Nd-Fe-B waste is calcined at a temperature of 700 °C for 2 h, and then concentrated sulfuric acid with a mass ratio of concentrated sulfuric acid to the material of 1.49 g / g is added to dissolve the Nd-Fe-B material, obtaining a solution containing rare earth sulfate and ferrous sulfate. Then, sodium sulfate with a mass ratio of raw material to ammonium sulfate of 1:2.5 is added to the solution to convert the rare earth sulfate into a double salt precipitate of neodymium sodium sulfate, while ferrous sulfate remains dissolved in the solution, separating the rare earth elements and iron elements. The double salt of neodymium sodium sulfate is added to sodium hydroxide solution, and the pH of the solution is adjusted to 10 - 12 to obtain a rare earth hydroxide precipitate, which is washed with deionized water to reduce sodium ions and sulfate ions, obtaining high-purity rare earth oxides. The calculated recovery rate of rare earth elements is 82.9%.

[0064] Table 1

[0065] As can be seen from Table 1, by using the method for recovering rare earth elements from Nd-Fe-B waste provided in this application, compared with Comparative Example 1, the rare earth elements have a higher recovery rate, and at the same time, the content of impurity metal elements in the stripping solution containing rare earth elements obtained by recovery is less, and it can be used to prepare high-purity rare earth oxides without further purification.

[0066] The above are only the preferred embodiments of this application, and are not intended to limit this application. Any modifications, equivalent replacements, and improvements made within the principle of this application shall be included in the protection scope of this application.

Claims

1. A method for recovering rare earth elements from NdFeB waste, characterized in that: The following steps are involved: Step S1: adding NdFeB waste into an oxidizing acid solution to dissolve the NdFeB waste in the oxidizing acid solution to obtain an oxidizing acid leaching solution; Step S2: adding alkali to the oxidizing acid leaching solution to adjust the pH, and then using a composite extractant to perform extraction treatment, so that the metal elements in the oxidizing acid leaching solution are extracted into the composite extractant, and the liquids are separated to obtain a raffinate and a loaded organic phase; Step S3: using a first hydrochloric acid solution to perform a first stripping treatment on the loaded organic phase, so that the Ni, Co, and Mn elements in the loaded organic phase are stripped into the first hydrochloric acid solution, and the liquids are separated to obtain a first stripping raffinate and a stripping solution containing Ni, Co, and Mn; the concentration c1 of the first hydrochloric acid solution is 0.21-1.16 g / L; Step S4: using a second hydrochloric acid solution to perform a second stripping treatment on the first raffinate, so that the Fe element in the first raffinate is stripped into the second hydrochloric acid solution, and the liquids are separated to obtain a second stripping raffinate and an Fe-containing stripping liquid; Step S5: using a third hydrochloric acid solution to perform a third stripping treatment on the second raffinate, so that the rare earth elements in the second raffinate are stripped into the third hydrochloric acid solution, and the liquids are separated to obtain a third stripping raffinate and a stripping liquid containing rare earth elements; wherein the concentration c1 of the first hydrochloric acid solution, the concentration c2 of the second hydrochloric acid solution and the concentration c3 of the third hydrochloric acid solution satisfy: c1<c2<c3.

2. The method according to claim 1, characterized in that In the step S1, the particle fineness of the NdFeB waste is 250-325 meshes.

3. The method according to claim 1, characterized in that In step S1, the oxidizing acid solution includes hydrochloric acid and hydrogen peroxide, wherein the concentration of the hydrochloric acid is 90-105 g / L, and the concentration of the hydrogen peroxide is 10-30 g / L.

4. The method according to claim 1, characterized in that: In the step S1, the solid-to-liquid ratio of the NdFeB waste to the oxidizing acid solution is 1:5-15.

5. The method according to claim 1, characterized in that In step S2, the composite extractant includes N,N-dioctyl diglycol amic acid, P507-Ni and kerosene, and the volume ratio of N,N-dioctyl diglycol amic acid, P507-Ni and kerosene is 2-4:1:5-7.

6. The method according to claim 1, characterized in that In step S4, the concentration c2 of the second hydrochloric acid solution is 1.2-20 g / L.

7. The method according to claim 1, characterized in that In step S5, the concentration c3 of the third hydrochloric acid solution is 21.1-36.5 g / L.

8. The method according to claim 1, characterized in that Also includes: Step S6: adding a precipitant to the rare earth element-containing stripping solution to allow the rare earth element to react with the precipitant to precipitate, thereby obtaining a precipitate containing the rare earth element; Step S7: calcining the rare earth element-containing precipitate to oxidize and decompose the rare earth element-containing precipitate to obtain rare earth oxides.

9. The method according to any one of claims 1 to 8, characterized in that: Also includes: Step S8: Adjust the pH of the raffinate in step S2 so that the remaining Ni 2+ Converted into Ni(OH)2 to obtain aqueous boric acid solution.

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