Method for recovering rare earths from high-cerium neodymium-iron-boron scrap

Abstract

The embodiment of the present disclosure provides a method for recovering rare earth from high-cerium neodymium iron boron waste, comprising: crushing, grinding and screening the high-cerium neodymium iron boron waste to obtain a powder raw material; roasting and oxidizing the powder raw material in an air atmosphere to obtain a roasting material containing endogenous Fe 2+ , the roasting and oxidizing treatment temperature is 500-650 DEG C, the roasting time is 4-7 h, and the air flow is 450-650 mL / min; the roasting material is leached with an acid solution, and solid-liquid separation treatment is performed to obtain a rare earth-rich leaching solution and a leaching residue, the TREO leaching rate of the leaching solution is 95%-99%, and the TFe leaching rate is 14-16%. The method uses Fe 2+ generated in the roasting process as a reducing agent to reduce Ce 4+ which is difficult to reduce, and can improve the TREO leaching rate and reduce the TFe leaching rate without additional reducing agent.

Description

Technical Field

[0001] This disclosure relates to the chemical industry, particularly to the metallurgical field of rare earth secondary resource recovery, and specifically to a method for efficiently recovering rare earths from high-cerium neodymium iron boron waste. Background Technology

[0002] High-cerium neodymium iron boron magnets have become an important category of rare earth permanent magnet materials due to their low raw material costs and high balance in the utilization of different rare earth resources. As a result, their production and processing generate waste materials such as scraps and discarded magnets, which have a high total rare earth TREO content, approximately 25wt%~35wt%, making them rare earth secondary resources with significant recycling value.

[0003] Currently, the main method for recycling traditional NdFeB waste is the oxidative roasting-hydrochloric acid preferential dissolution method, which has the advantages of good selectivity, low acid consumption, and ease of large-scale production. However, in the high-cerium NdFeB system, Ce element readily generates rare earth-containing phases of CeO2 structure that are difficult to dissolve in hydrochloric acid during the oxidative roasting process. This results in other valuable rare earth elements such as Nd and Pr remaining in large quantities in the leaching residue along with CeO2, thus leading to a low rare earth resource recovery rate.

[0004] Therefore, how to economically and efficiently recover rare earth resources from high-cerium NdFeB waste is a key issue in the field of rare earth secondary resource recycling. Summary of the Invention

[0005] This disclosure provides a method for recovering rare earth elements from high-cerium neodymium iron boron waste to solve or alleviate one or more technical problems in the related art.

[0006] This application proposes a method for recovering rare earth elements from high-cerium neodymium iron boron waste, the method comprising:

[0007] (1) The high-cerium neodymium iron boron waste is crushed, ground and screened to obtain powder raw material;

[0008] (2) The powder raw material is calcined and oxidized in air atmosphere to obtain a product containing endogenous Fe. 2+ The calcination and oxidation treatment of the feedstock is carried out at a temperature of 500℃~650℃ and a calcination time of 4-7h. The calcination is carried out under the condition of air introduction, and the air flow rate is 450 mL / min~650 mL / min.

[0009] (3) The roasting material is leached with acid to utilize the endogenous Fe generated during the roasting process. 2+ Reduce Ce in the calcined material 4+ The product obtained after the leaching process is subjected to solid-liquid separation to obtain rare earth-rich leachate and leaching residue.

[0010] The TREO leaching rate of the leachate is 95%-99%, and the TFe leaching rate of the leachate is 14-16%.

[0011] This method involves a pre-calcination oxidation treatment before leaching, utilizing the Fe generated during the calcination process. 2+ For reducing agents to reduce the difficult-to-reduce Ce 4+ Reduction can be performed, thereby increasing TREO leaching rate and decreasing TFe leaching rate without the addition of additional reducing agents.

[0012] According to an embodiment of this application, the total rare earth TRE content in the high-cerium NdFeB waste is 25wt% to 35wt%, wherein cerium accounts for 30wt% to 50wt% of the total rare earth, and the high-cerium NdFeB waste further includes at least one of Fe, B, Al, and Co elements.

[0013] According to embodiments of this application, the high-cerium neodymium iron boron waste includes rare earth-containing waste that is unmagnetized and uncoated.

[0014] According to embodiments of this application, the high-cerium neodymium iron boron waste includes at least one of industrial production waste magnets, processing scraps, and scrapped magnets.

[0015] According to an embodiment of this application, the sieving process in step (1) includes: performing the sieving process using a 150-300 mesh standard sieve, preferably a 150-250 mesh standard sieve. This allows the waste powder to have a more uniform particle size, effectively eliminating the adverse effects of particle size differences on the subsequent oxidation degree and leaching behavior.

[0016] According to an embodiment of this application, in step (2), the calcination treatment satisfies at least one of the following conditions:

[0017] The powder raw material is placed in a muffle furnace for the calcination treatment. After the muffle furnace is preheated to the target temperature and kept at a constant temperature for 10 minutes, the powder raw material is then placed in.

[0018] The calcination temperature is 550℃~630℃;

[0019] The air flow rate is 450 mL / min to 550 mL / min.

[0020] Therefore, Fe can be generated in situ by controlling the calcination time. 2+ The endogenous Fe was obtained. 2+ The calcining material, and precisely control the Fe content in the calcining material. 2+ With Ce 4+ The content ratio.

[0021] According to an embodiment of this application, the leaching treatment in step (3) satisfies at least one of the following conditions:

[0022] The acid solution includes hydrochloric acid, and the concentration of the hydrochloric acid is 0.5 mol / L to 2 mol / L;

[0023] The liquid-to-solid ratio of the leaching treatment is 5:1 to 20:1 mL / g;

[0024] The leaching temperature for the leaching treatment is 65℃~95℃;

[0025] The leaching time for the leaching treatment is 1 h to 3 h;

[0026] The stirring rate for the leaching treatment is 200 r / min to 400 r / min.

[0027] This can further improve the leaching rate of rare earth elements.

[0028] According to embodiments of this application, the concentration of the hydrochloric acid is 0.8 mol / L to 1.5 mol / L;

[0029] The liquid-to-solid ratio of the leaching treatment is 8:1 to 15:1 mL / g;

[0030] The leaching temperature for the leaching treatment is 75℃~90℃;

[0031] The leaching time for the leaching treatment is 1.5 h to 2.5 h;

[0032] The stirring rate for the leaching treatment is 250 r / min to 400 r / min.

[0033] According to an embodiment of this application, the high-cerium NdFeB waste contains 0.8-1.2 wt% B, 0.2-0.4 wt% Al, 65-67% Fe, and 0.3-0.5 wt% Co, and the total rare earth TRE content in the high-cerium NdFeB waste is 28-32 wt%.

[0034] According to embodiments of this application, the TREO leaching rate of the leachate is 95.05%-98.5%, and the TFe leaching rate of the leachate is 14.02%-15.9%. Attached Figure Description

[0035] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments according to this disclosure and should not be construed as limiting the scope of this disclosure.

[0036] Figure 1 The XRD patterns of the calcined products of Example 2 and the comparative example are shown below.

[0037] Figure 2 Comparison of the cross-sectional morphology of the leaching residue from Example 2 and the comparative example;

[0038] Figure 3 The XRD patterns of the leaching residues from Example 2 and the comparative example are shown. Detailed Implementation

[0039] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this disclosure, and different embodiments can be combined arbitrarily without conflict. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0040] As a first aspect of the present disclosure, this disclosure provides a method for recovering rare earth elements from high-cerium NdFeB waste. The method includes the steps of crushing, grinding, and sieving the high-cerium NdFeB waste to obtain powder raw materials; the steps of calcining and oxidizing the powder raw materials to obtain calcined material containing endogenous Fe2+; and the steps of leaching the calcined material with acid to finally obtain a rare earth-rich leachate.

[0041] As mentioned earlier, to overcome the bottleneck of CeO2's poor solubility in related technologies, three main technical routes have been developed: First, increasing the hydrochloric acid concentration to enhance CeO2 dissolution through a strong acid system. However, this method suffers from high acid consumption, severe equipment corrosion, and significant leaching of iron, significantly increasing the load on subsequent rare earth separation and purification. Second, adding external reducing agents, such as hydrogen peroxide and thiourea, to dissolve CeO2. 4+ Reduced to Ce, which is readily soluble in hydrochloric acid. 3+ While this technical approach can improve the leaching rate of rare earth elements, it suffers from drawbacks such as high reagent costs and the introduction of impurity ions. Thirdly, strengthening leaching methods, such as pressure leaching and microwave-assisted leaching, can improve the leaching effect, but it has shortcomings such as high equipment investment, demanding operating conditions, and poor industrial adaptability.

[0042] The method proposed in this application pre-treats the material with roasting and oxidation before acid leaching, obtaining roasted material containing endogenous Fe2+. By adjusting the process parameters of the roasting and oxidation treatment, the Fe content in the roasted material is precisely controlled. 2+ With Ce 4+ The content ratio is 30%~55%, thus matching Ce. 4+The required stoichiometric ratio for reduction ensures both the reduction effect and avoids an increase in the iron leaching rate, thereby further reducing the acid concentration and acid consumption in subsequent acid leaching steps. In some embodiments, the TREO leaching rate of the leachate can reach 95%-99%, and the TFe leaching rate in the leachate is 14-16%.

[0043] Therefore, without introducing additional reducing agents or significantly increasing the concentration and amount of leaching acid, a relatively objective TREO leaching rate can be obtained based on atmospheric pressure leaching, while reducing the TFe leaching rate in the leachate and reducing the process difficulty of further utilizing the leachate.

[0044] According to some embodiments of this disclosure, high-cerium NdFeB waste can first be crushed, ground, and sieved to obtain powder raw materials. Crushing and grinding can reduce the particle size of the high-cerium NdFeB waste and make the particle size distribution more uniform, and allow the various particulate components in the raw material to mix better, thereby obtaining a more homogeneous system and improving the efficiency of subsequent roasting oxidation and acid leaching treatments.

[0045] According to an embodiment of this application, the total rare earth TRE content in the high-cerium NdFeB waste is 25wt% to 35wt%, wherein cerium accounts for 30wt% to 50wt% of the total rare earth, and the high-cerium NdFeB waste further includes at least one of Fe, B, Al, and Co elements.

[0046] According to embodiments of this application, the high-cerium neodymium iron boron waste includes rare earth-containing waste that is unmagnetized and uncoated.

[0047] According to embodiments of this application, the high-cerium neodymium iron boron waste includes at least one of industrial production waste magnets, processing scraps, and scrapped magnets.

[0048] Specifically, the sieving process in step (1) may include using a 150-300 mesh standard sieve, which can make the particle size of the waste powder more uniform and effectively eliminate the adverse effects of particle size differences on the subsequent oxidation degree and leaching behavior. In some preferred embodiments, a 150-250 mesh standard sieve may be used, such as a 150 mesh, 200 mesh, or 250 mesh standard sieve.

[0049] According to an embodiment of this application, in step (2), the powder raw material obtained in step (1) is subjected to calcination oxidation treatment in an air atmosphere to obtain calcined material containing endogenous Fe2+. Specifically, the calcination oxidation treatment temperature is 500℃~650℃, the calcination time is 4-7h, and the calcination is carried out under the condition of air introduction, with an air flow rate of 450 mL / min~650 mL / min.

[0050] The above process parameters can effectively reduce the Fe content in the calcined material. 2+ With Ce 4+ The content ratio is controlled within a reasonable range to improve the leaching rate of rare earth elements.

[0051] Specifically, the powdered raw material can be placed in a muffle furnace for the aforementioned calcination treatment. After the muffle furnace has been preheated to the target temperature and stabilized, the powdered raw material is then placed in. The target temperature can be the aforementioned calcination temperature, which can be achieved by heating the muffle furnace to the calcination temperature for 10 minutes before placing the powdered raw material in.

[0052] In some embodiments, the calcination temperature can be 500℃ to 630℃, preferably 550℃ to 630℃, such as 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, or 630℃, etc.

[0053] During the roasting process, air can be introduced into the muffle furnace at a constant flow rate. The air flow rate can be 450 mL / min to 550 mL / min. For example, specific flow rates can be 450 mL / min, 480 mL / min, 500 mL / min, 520 mL / min, 530 mL / min, 550 mL / min, etc.

[0054] The calcination time needs to be adjusted flexibly according to the calcination temperature, following the principle of shorter calcination time for higher temperatures and longer calcination time for lower temperatures, to ensure that sufficient and suitable Fe can be generated under different temperature conditions. 2+ For example, the roasting time can be 4-7 hours. If the roasting time is too short, the waste will not be fully oxidized, and the rare earth phase will be difficult to dissociate effectively; if the roasting time is too long, Fe will be completely oxidized to Fe2+. 3+ Insufficient Fe 2+ Implement Ce 4+ The reduction process cannot achieve the desired effect of enhanced leaching. Preferably, the calcination time is 6 h to 4 h.

[0055] Therefore, Fe can be generated in situ by controlling the calcination time. 2+ The endogenous Fe was obtained. 2+ The calcining material, and precisely control the Fe content in the calcining material. 2+ With Ce 4+ The content ratio. The purpose of controlling the calcination process parameters is to generate Fe with reducing activity in situ within the system by controlling the degree of oxidation. 2+ For subsequent leaching processes, Ce 4+The reduction process provides endogenous reducing components. Therefore, the method proposed in this application completely eliminates the need for external reducing agents, thus fundamentally solving the problems of impurities introduced by exogenous agents and high costs. The above conditions can precisely control the Fe content in the calcined material. 2+ With Ce 4+ The content ratio is 30%~55%, matching Ce 4+ The stoichiometric ratio required for reduction ensures both the reduction effect and avoids Fe... 2+ Excessive use leads to an increase in the subsequent iron leaching rate.

[0056] According to an embodiment of this application, in step (3), the roasted material is leached with acid and subjected to solid-liquid separation to obtain rare earth-rich leachate and leachate residue.

[0057] In some embodiments, the acid solution includes hydrochloric acid. The concentration of the hydrochloric acid is 0.5 mol / L to 2 mol / L, for example, it can be 0.8 mol / L to 1.5 mol / L, specifically 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, or 2 mol / L.

[0058] The liquid-to-solid ratio for leaching can be 5:1 to 20:1 mL / g, for example, 8:1 to 15:1 mL / g. Specifically, it can be 5:1 mL / g, 6:1 mL / g, 7:1 mL / g, 8:1 mL / g, 9:1 mL / g, 10:1 mL / g, 11:1 mL / g, 12:1 mL / g, 13:1 mL / g, 14:1 mL / g, 15:1 mL / g, 18:1 mL / g, 20:1 mL / g, etc. The solid-to-liquid ratio can be adjusted according to the concentration of hydrochloric acid and the total rare earth TRE content in the selected high-cerium NdFeB waste.

[0059] According to the embodiments of this application, the leaching temperature of the leaching treatment can be 65℃~95℃, for example, 75℃~90℃, specifically 65℃, 68℃, 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, 85℃, 88℃, 90℃, etc.

[0060] According to the embodiments of this application, the leaching time for the leaching treatment can be 1 h to 3 h, specifically 1.5 h to 2.5 h.

[0061] In some embodiments, the leaching process can be carried out under stirring, with a stirring rate of 200 r / min to 400 r / min, such as 250 r / min to 400 r / min. This can further improve the leaching rate of rare earth elements.

[0062] According to an embodiment of this application, the high-cerium NdFeB waste contains 0.8-1.2 wt% B, 0.2-0.4 wt% Al, 65-67% Fe, and 0.3-0.5 wt% Co, and the total rare earth element (TRE) content in the high-cerium NdFeB waste is 28-32 wt%. When the high-cerium NdFeB waste is treated using the aforementioned method, the TREO leaching rate of the resulting leachate can be 95.05%-98.5%, and the TFe leaching rate in the leachate is 14.02-15.9%.

[0063] The method proposed in this application will be further described below with reference to specific embodiments. Unless otherwise specified, the reagents used in the following embodiments are all commercially available reagents.

[0064] The following examples and comparative examples all involve the treatment of high-cerium NdFeB waste. The chemical composition of the high-cerium NdFeB waste in each example and comparative example is shown in Table 1 below:

[0065] Table 1

[0066]

[0067] Example 1

[0068] High-cerium NdFeB waste (25.44 wt% Ce) was crushed using a sealed sample preparation machine, with a single crushing time of 15 s and an interval of 1 min to avoid over-crushing and overheating that could lead to spontaneous combustion. After crushing, the sample was passed through a 200-mesh standard sieve to obtain powder with uniform particle size. 17 g of the waste powder was accurately weighed and evenly spread in an alumina boat measuring 90 mm × 60 mm × 20 mm. The muffle furnace was preheated to 550 °C and held at that temperature for 10 min, with air continuously introduced at a rate of 550 mL / min. The boat was then placed in the constant-temperature zone of the furnace and isothermally calcined for 5.5 h to obtain a product containing endogenous Fe. 2+ The calcined feedstock was re-ground and passed through a 200-mesh sieve. 10 g of the oxidized feedstock was weighed and placed in a 300 mL beaker. Leaching was performed using 0.8 mol / L hydrochloric acid at a stirring rate of 250 r / min. The leaching parameters were: liquid-to-solid ratio 15:1 mL / g, leaching temperature 90℃, and leaching time 2 h. After vacuum filtration and dilution of the filtrate, the elemental concentrations were determined using ICP-OES. The calculated total rare earth TREO leaching rate was 98.23%, and the total iron TFe leaching rate was 15.89%.

[0069] Example 1-1

[0070] The same raw material (25.44 wt% Ce) as in Example 1 was used, except that the predetermined temperature for the roasting and oxidation treatment was 600°C (other conditions were the same as in Example 1, and the same applies below). Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 97.12%, and the total iron TFe leaching rate was 15.39%.

[0071] Examples 1-2

[0072] The same raw material (25.44 wt% Ce) as in Example 1 was used, except that the predetermined temperature for the roasting and oxidation treatment was 500°C. After vacuum filtration and dilution of the filtrate, the elemental concentrations were determined by ICP-OES. The total rare earth TREO leaching rate was calculated to be 98.32%, and the total iron TFe leaching rate was 15.86%.

[0073] Examples 1-3

[0074] The same raw material (25.44 wt% Ce) as in Example 1 was used, except that the leaching process parameters were a liquid-to-solid ratio of 10:1 mL / g. Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 97.26%, and the total iron TFe leaching rate was 14.98%.

[0075] Examples 1-4

[0076] The same raw material (25.44 wt% Ce) as in Example 1 was used, except that the leaching process parameters were a liquid-to-solid ratio of 20:1 mL / g. Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 98.50%, and the total iron TFe leaching rate was 15.90%.

[0077] Examples 1-5

[0078] The same raw material (25.44 wt% Ce) as in Example 1 was used, except that the leaching process parameters were 1 mol / L hydrochloric acid. Vacuum filtration was performed, and the filtrate was brought to a final volume. The elemental concentrations were determined using ICP-OES, and the total rare earth TREO leaching rate was calculated to be 98.41%, and the total iron TFe leaching rate was 15.61%.

[0079] Examples 1-6

[0080] The same raw material (25.44 wt% Ce) as in Example 1 was used, except that the leaching process parameters were 0.5 mol / L hydrochloric acid leaching. Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined by ICP-OES after volume adjustment. The total rare earth TREO leaching rate was calculated to be 95.83%, and the total iron TFe leaching rate was 14.26%.

[0081] Example 2

[0082] High-cerium NdFeB waste (30.56 wt% Ce) was crushed using a sealed sample preparation machine, with a single crushing time of 15 s and a 1-min interval to avoid over-crushing and overheating that could lead to spontaneous combustion. After crushing, the sample was passed through a 200-mesh standard sieve to obtain powder with uniform particle size. 17 g of the waste powder was accurately weighed and evenly spread in an alumina boat measuring 90 mm × 60 mm × 20 mm. The muffle furnace was preheated to 600℃ and held at that temperature for 10 min, with air continuously introduced at a rate of 500 mL / min. The boat was then placed in the constant-temperature zone of the furnace and isothermally calcined for 5 h to obtain a product containing endogenous Fe. 2+ The calcined feedstock was re-ground and passed through a 200-mesh sieve. 10 g of the oxidized feedstock was weighed and placed in a 300 mL beaker. Leaching was performed using 1 mol / L hydrochloric acid at a stirring rate of 300 r / min. The leaching parameters were a liquid-to-solid ratio of 10:1 mL / g, a leaching temperature of 85℃, and a leaching time of 2 h. The solution was then vacuum filtered, and the elemental concentrations were determined using ICP-OES after the filtrate was brought to a final volume. The calculated total rare earth TREO leaching rate was 95.62%, and the total iron TFe leaching rate was 14.96%.

[0083] Example 2-1

[0084] The same raw material (30.56 wt% Ce) as in Example 2 was used, except that the predetermined temperature for the roasting and oxidation treatment was 550°C (other conditions were the same as in Example 2, and the same applies below). Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 96.35%, and the total iron TFe leaching rate was 15.04%.

[0085] Example 2-2

[0086] The same raw material (30.56 wt% Ce) as in Example 2 was used, except that the predetermined temperature for the calcination oxidation treatment was 630°C. After vacuum filtration and dilution of the filtrate, the elemental concentrations were determined by ICP-OES. The total rare earth TREO leaching rate was calculated to be 95.22%, and the total iron TFe leaching rate was 14.59%.

[0087] Example 2-3

[0088] The same raw material (30.56 wt% Ce) as in Example 2 was used, except that the leaching process parameters were a liquid-to-solid ratio of 5:1 mL / g. Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 95.06%, and the total iron TFe leaching rate was 14.08%.

[0089] Examples 2-4

[0090] The same raw material (30.56 wt% Ce) as in Example 2 was used, except that the leaching process parameters were a liquid-to-solid ratio of 15:1 mL / g. Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 98.13%, and the total iron TFe leaching rate was 15.57%.

[0091] Examples 2-5

[0092] The same raw material (30.56 wt% Ce) as in Example 2 was used, except that the leaching process parameters were 0.8 mol / L hydrochloric acid leaching. Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined by ICP-OES after volume adjustment. The total rare earth TREO leaching rate was calculated to be 95.58%, and the total iron TFe leaching rate was 14.87%.

[0093] Examples 2-6

[0094] The same raw material (30.56 wt% Ce) as in Example 2 was used, except that the leaching process parameters were 1.5 mol / L hydrochloric acid leaching. Vacuum filtration was performed, and after the filtrate was brought to a final volume, the elemental concentrations were determined using ICP-OES. The calculated total rare earth TREO leaching rate was 98.33%, and the total iron TFe leaching rate was 15.69%.

[0095] Example 3

[0096] This embodiment represents the preferred process conditions of the present invention, and the steps are as follows:

[0097] High-cerium NdFeB waste (35.46 wt% Ce) was crushed using a sealed sample preparation machine, with a single crushing time of 15 s and a 1-min interval to avoid over-crushing and overheating that could lead to spontaneous combustion. After crushing, the sample was passed through a 200-mesh standard sieve to obtain powder with uniform particle size. 17 g of the waste powder was accurately weighed and evenly spread in an alumina boat measuring 90 mm × 60 mm × 20 mm. The muffle furnace was preheated to 630 °C and held at that temperature for 10 min, with air continuously introduced at a rate of 450 mL / min. The boat was then placed in the constant-temperature zone of the furnace and isothermally calcined for 4.5 h to obtain a product containing endogenous Fe. 2+ The calcined feedstock was re-ground and passed through a 200-mesh sieve. 10 g of the oxidized feedstock was weighed and placed in a 300 mL beaker. Leaching was performed using 1.2 mol / L hydrochloric acid at a stirring rate of 350 r / min. The leaching parameters were: liquid-to-solid ratio 12:1 mL / g, leaching temperature 80℃, and leaching time 2.5 h. After vacuum filtration and dilution of the filtrate, the elemental concentrations were determined using ICP-OES. The calculated total rare earth TREO leaching rate was 95.05%, and the total iron TFe leaching rate was 14.02%.

[0098] Example 3-1

[0099] The same raw material (35.46 wt% Ce) as in Example 3 was used, except that the predetermined temperature for the roasting and oxidation treatment was 580°C (other conditions were the same as in Example 3, and the same applies below). Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 97.06%, and the total iron TFe leaching rate was 14.12%.

[0100] Example 3-2

[0101] The same raw material (35.46 wt% Ce) as in Example 3 was used, except that the predetermined temperature for the roasting and oxidation treatment was 650°C. After vacuum filtration and dilution of the filtrate, the elemental concentrations were determined by ICP-OES. The total rare earth TREO leaching rate was calculated to be 95.06%, and the total iron TFe leaching rate was 14.03%.

[0102] Example 3-3

[0103] The same raw material (35.46 wt% Ce) as in Example 3 was used, except that the leaching process parameters were a liquid-to-solid ratio of 8:1 mL / g. Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 95.08%, and the total iron TFe leaching rate was 14.07%.

[0104] Examples 3-4

[0105] The same raw material (35.46 wt% Ce) as in Example 3 was used, except that the leaching process parameters were a liquid-to-solid ratio of 20:1 mL / g. Vacuum filtration was performed, and the elemental concentrations of the filtrate were determined using ICP-OES after volume adjustment. The calculated total rare earth TREO leaching rate was 98.36%, and the total iron TFe leaching rate was 15.73%.

[0106] Examples 3-5

[0107] The same raw material (35.46 wt% Ce) as in Example 3 was used, except that the leaching process parameters were 0.8 mol / L hydrochloric acid leaching. Vacuum filtration was performed, and after the filtrate was brought to a final volume, the elemental concentrations were determined by ICP-OES. The calculated total rare earth TREO leaching rate was 95.05%, and the total iron TFe leaching rate was 14.07%.

[0108] Examples 3-6

[0109] The same raw material (35.46 wt% Ce) as in Example 3 was used, except that the leaching process parameters were 1.5 mol / L hydrochloric acid leaching. After vacuum filtration and volume adjustment of the filtrate, the elemental concentrations were determined by ICP-OES. The calculated total rare earth TREO leaching rate was 98.40%, and the total iron TFe leaching rate was 15.83%.

[0110] Comparative Example 1

[0111] This comparative example represents the mainstream industrial process for recycling NdFeB waste. It uses the same raw material as Example 2 (30.56wt% Ce), and the pretreatment and hydrochloric acid leaching conditions are identical to those in Example 2. The air flow rate during the roasting process is also 500 mL / min. The difference is that the waste powder is roasted at 600℃ for 8 hours until completely oxidized. No significant Fe was found in the roasted material. 2+ Residue. After leaching, vacuum filtration was performed, and the elemental concentrations of the filtrate were determined by ICP-OES after the filtrate was brought to a constant volume. The calculated total rare earth leaching rate was only 84.30%, and the total iron leaching rate was 12.61%.

[0112] For ease of comparison, the main chemical components of the leaching residues of Example 2 and the comparative example are listed in Table 2:

[0113] Table 2

[0114]

[0115] refer to Figure 1 The XRD patterns show that in Comparative Example 1, iron mainly exists as Fe2O3, while cerium is mainly insoluble CeO2; however, in Example 2, in addition to Fe2O3, the calcined product also shows characteristic peaks of Fe3O4, and cerium exists as Ce7O in a mixed valence state. 12 Yes. This result indicates that the process of the present invention can achieve the in-situ generation of reducing components containing Fe2+ by controlling the calcination conditions, thereby realizing the production of sparingly soluble Ce. 4+ The conversion to easily soluble mixed-valence cerium oxides.

[0116] refer to Figure 2 The cross-sectional morphology shows that, in comparison (e.g.) Figure 2 As shown in (b) of the example, the leaching residue contains a distinct white rare earth phase, while in Example 2 (as shown in the example), the leaching residue contains a distinct white rare earth phase. Figure 2 The white rare earth phase in the leaching residue shown in (a) has essentially disappeared. Figure 3XRD analysis of the leaching residue and the composition analysis of the leaching residue in Table 2 show that the TREO content in the leaching residue of Example 2 is only 1.28 wt%, far lower than the 5.65 wt% of the comparative example. Furthermore, no obvious rare earth phase was detected in the residue, confirming that the rare earth elements have been largely leached into the solution. This corresponds to a rare earth leaching rate of 95.62% in Example 2, significantly higher than the 84.30% of the comparative example. It should be noted that although the proportion of Ce in the residual rare earth elements in the leaching residue of Example 2 is 44.86 wt%, slightly lower than the 57.63 wt% of the comparative example, the absolute residual amount of Ce is still far lower than that of the comparative example due to the extremely low total rare earth residual amount (1.28 wt%). This indicates that this process significantly enhances the leaching efficiency of cerium and greatly reduces the residue of cerium and other rare earth elements in the residue.

[0117] In summary, the optimal process of this invention demonstrates excellent recovery performance for high-cerium NdFeB waste containing 30%-50% wt% of total rare earth elements. Compared to conventional complete oxidation processes, the total rare earth leaching rate in Example 2 (30.56 wt% Ce) of this invention is increased by 11.32%, and the total rare earth leaching rate in all three examples remains stable above 95%, solving the problem of difficult rare earth recovery from high-cerium waste. Furthermore, the process is convenient to operate, suitable for continuous industrial production, and combines economic efficiency with practicality.

[0118] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "multiple" means two or more, unless otherwise explicitly specified.

[0119] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0120] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" a second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of a second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" a second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. The foregoing disclosure provides many different embodiments or examples for implementing different structures of this disclosure. To simplify this disclosure, components and arrangements of specific examples are described above. Of course, these are merely examples and are not intended to limit this disclosure. Furthermore, reference numerals and / or reference letters may be repeated in different examples of this disclosure; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0121] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this disclosure, and these should all be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for recovering rare earth elements from high-cerium NdFeB waste, characterized in that, include: (1) The high-cerium neodymium iron boron waste is crushed, ground and screened to obtain powder raw material; (2) The powder raw material is calcined and oxidized in air atmosphere to obtain a product containing endogenous Fe. 2+ The calcination and oxidation treatment of the feedstock is carried out at a temperature of 500℃~650℃ and a calcination time of 4-7h. The calcination is carried out under the condition of air introduction, and the air flow rate is 450 mL / min~650 mL / min. (3) The roasting material is leached with acid to utilize the endogenous Fe generated during the roasting process. 2+ Reduce Ce in the calcined material 4+ The product obtained after the leaching process is subjected to solid-liquid separation to obtain rare earth-rich leachate and leaching residue. The TREO leaching rate of the leachate is 95%-99%, and the TFe leaching rate of the leachate is 14-16%.

2. The method according to claim 1, characterized in that, The total rare earth element (TRE) content in the high-cerium NdFeB waste is 25wt%–35wt%, of which cerium accounts for 30wt%–50wt% of the total rare earth element. The high-cerium neodymium iron boron waste further includes at least one of the elements Fe, B, Al, and Co.

3. The method according to claim 2, characterized in that, The high-cerium neodymium iron boron waste includes rare earth-containing waste that is unmagnetized and uncoated.

4. The method according to claim 3, characterized in that, The high-cerium neodymium iron boron waste includes at least one of the following: industrial waste magnets, processing scraps, and scrapped magnets.

5. The method according to claim 1, characterized in that, The screening process in step (1) includes: The sieving process is performed using a 150-300 mesh standard sieve, preferably a 150-250 mesh standard sieve.

6. The method according to claim 1, characterized in that, In step (2), the calcination treatment satisfies at least one of the following conditions: The powder raw material is placed in a muffle furnace for the calcination treatment. After the muffle furnace is preheated to the target temperature and kept at a constant temperature for 10 minutes, the powder raw material is then placed in. The calcination temperature is 550℃~630℃; The air flow rate is 450 mL / min to 550 mL / min.

7. The method according to claim 1, characterized in that, The leaching treatment in step (3) satisfies at least one of the following conditions: The acid solution includes hydrochloric acid, and the concentration of the hydrochloric acid is 0.5 mol / L to 2 mol / L; The liquid-to-solid ratio of the leaching treatment is 5:1 to 20:1 mL / g; The leaching temperature for the leaching treatment is 65℃~95℃; The leaching time for the leaching treatment is 1 h to 3 h; The stirring rate for the leaching treatment is 200 r / min to 400 r / min.

8. The method according to claim 7, characterized in that, The concentration of the hydrochloric acid is 0.8 mol / L to 1.5 mol / L; The liquid-to-solid ratio of the leaching treatment is 8:1 to 15:1 mL / g; The leaching temperature for the leaching treatment is 75℃~90℃; The leaching time for the leaching treatment is 1.5 h to 2.5 h; The stirring rate for the leaching treatment is 250 r / min to 400 r / min.

9. The method according to claim 1, characterized in that, The high-cerium NdFeB waste contains 0.8-1.2 wt% B, 0.2-0.4 wt% Al, 65-67% Fe, and 0.3-0.5 wt% Co. The total rare earth element (TRE) content in the high-cerium NdFeB waste is 28-32 wt%.

10. The method according to claim 9, characterized in that, The TREO leaching rate of the leachate is 95.05%-98.5%, and the TFe leaching rate of the leachate is 14.02%-15.9%.

Images