Method for extracting rare earth elements

Abstract

The invention discloses a method for extracting rare earth elements, which comprises the following steps of: contacting a material containing the rare earth elements with a conductive carbon-based material to obtain a precursor; and the precursor is subjected to Joule heat treatment and leaching treatment, and the rare earth element leachate is obtained. The method provided by the invention has a high rare earth element extraction rate.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth element extraction and recovery, and specifically relates to a method for efficiently extracting rare earth elements from multi-source solid waste by utilizing flash Joule heat technology. Background Art

[0002] With the increasing demand for rare earths, how to efficiently recycle rare earth elements contained in waste has become an urgent problem to be solved. The sources of rare earth elements in solid waste mainly include discarded phosphogypsum, electronic waste and some other industrial waste. These solid wastes are usually treated by traditional hydrometallurgical methods, but these methods often require a large amount of chemical reagents, the treatment process is complicated and time-consuming, and it is easy to cause secondary pollution.

[0003] As an emerging heat treatment technology, the flash Joule heating method is characterized by being able to heat substances to extremely high temperatures in a very short time, thereby effectively increasing the reaction rate of the substances and avoiding the energy waste caused by long-term heating. The flash Joule heating method has shown good application prospects in some fields, especially in solid waste treatment and metal recovery. However, there are still problems with the complex extraction process and low extraction rate. Therefore, there is an urgent need for a simple and efficient extraction method to further improve the extraction rate of rare earth elements. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. To this end, the present invention provides a method for extracting rare earth elements, which can significantly improve the extraction rate of rare earth elements.

[0005] Therefore, in the first aspect of the present invention, a method for extracting rare earth elements is proposed, which is characterized in that it includes the following steps: contacting a material containing rare earth elements with a conductive carbon-based material to obtain a precursor; subjecting the precursor to Joule heat treatment and leaching treatment to obtain a rare earth element leaching solution.

[0006] The present invention brings the material containing rare earth elements into contact with the conductive carbon-based material, applies electric current to generate Joule heat, and rapidly heats the mixture in a short time, thereby promoting the dissolution and leaching of the rare earth elements in the material containing rare earth elements. Therefore, the method of the present invention has a higher rare earth element extraction rate.

[0007] In some embodiments, the Joule heat treatment is performed at a temperature of 700 to 2000° C. and for a time of 1 to 60 seconds.

[0008] In some embodiments, the resistance is controlled to be 1-2Ω during the Joule heat treatment.

[0009] In some embodiments, the material containing rare earth elements includes at least one of phosphogypsum, permanent magnets, nickel-hydrogen batteries, and rare earth-enriched plants.

[0010] In some embodiments, contacting a material containing a rare earth element with a conductive carbon-based material comprises:

[0011] mixing a material containing a rare earth element with a conductive carbon-based material;

[0012] Alternatively, a material containing a rare earth element is placed on one side of the conductive carbon-based material.

[0013] In some embodiments, the conductive carbon-based material includes at least one of carbon black, graphene, graphite, carbon nanotubes, and carbon fibers; the conductive carbon-based material exists in a form including at least one of carbon paper, carbon cloth, and carbon felt.

[0014] In some embodiments, the amount of the material containing rare earth elements added to the precursor is 2 to 3 times the mass of the conductive carbon-based material.

[0015] In some embodiments, the leaching solution includes at least one of a sulfuric acid solution, a nitric acid solution, and a hydrochloric acid solution, and the concentration of the solution is 1 to 5 mol / L.

[0016] In some embodiments, the leaching temperature is 85-95° C., and the leaching time is 0.5-1.5 h.

[0017] In some embodiments, after the Joule heat treatment, a cooling treatment is also included, and the cooling treatment includes: rapidly cooling the sample obtained after the Joule heat treatment to room temperature through thermal radiation.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] The present invention provides a method for recovering rare earth elements from multi-source solid waste using flash Joule heating technology. The method is to contact a material containing rare earth elements with a conductive carbon-based material, apply an electric current to generate Joule heat, and rapidly heat the mixture, thereby promoting the dissolution and leaching of rare earth elements in the solid waste. Compared with the traditional roasting and leaching method, the flash Joule heating method has the advantages of simple operation, short time, high energy efficiency, and environmental friendliness. It is suitable for the extraction and processing of a variety of complex mineral resources.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0022] Figure 1 This is a process flow chart of extracting rare earth elements using flash Joule heating technology in Example 1 of the present invention;

[0023] Figure 2 is the XRD diagram of the phosphogypsum sample in Example 1 of the present invention;

[0024] Figure 3 is a SEM image of the phosphogypsum sample in Example 1 of the present invention;

[0025] Figure 4 This is an EDS spectrum analysis diagram of the phosphogypsum sample in Example 1 of the present invention;

[0026] Figure 5 TG-DTG diagram of the phosphogypsum sample in Example 1 of the present invention;

[0027] Figure 6 The real-time temperature curve diagram recorded by an infrared thermometer when the phosphogypsum samples and the conductive carbon black are heated by a quartz reactor in Examples 1 to 3 of the present invention;

[0028] Figure 7 The XRD diagrams of the samples of the phosphogypsum samples in Examples 1 to 3 of the present invention after being heated using the flash Joule heating technique;

[0029] Figure 8 This is a thermodynamic calculation diagram of the reaction between calcium sulfate and carbon black in phosphogypsum in Example 1 of the present invention;

[0030] Fig. 9 This is a thermodynamic calculation diagram of the reaction between rare earth sulfate and carbon black in Example 1 of the present invention;

[0031] Fig.10 The figure is a trend diagram of the change of the leaching rate of rare earth elements with the heating time in Examples 1 to 3 of the present invention;

[0032] Fig.11 is a trend diagram showing the change of the leaching rate of rare earth elements in phosphogypsum with the concentration of nitric acid in Examples 4 to 9 of the present invention;

[0033] Fig.12 The figure is a trend diagram showing the change of the leaching rate of rare earth elements in phosphogypsum with the concentration of hydrochloric acid and sulfuric acid in Examples 17 to 26 of the present invention;

[0034] Fig.13 This is a SEM image of the residual powder after the leaching process in Example 1 of the present invention is completed;

[0035] Fig.14 This is an EDS spectrum analysis diagram of the residual powder after the leaching process in Example 1 of the present invention is completed;

[0036] Fig.15 This is a SEM image of the rare earth-enriched plant sample in Example 10 of the present invention;

[0037] Fig.16 TG-DTG graph of the rare earth-enriched plant sample in Example 10 of the present invention;

[0038] Fig.17 A real-time temperature curve diagram recorded by an infrared thermometer when the rare earth-enriched plant sample in Example 10 of the present invention is heated by carbon paper;

[0039] Fig.18 The XRD diagram of the rare earth-enriched plant sample in Example 10 of the present invention before and after heating using the flash Joule heating technology;

[0040] Fig.19 is a trend diagram showing the change in the leaching rate of rare earth elements in rare earth-enriched plants as a function of heating temperature in Examples 10 to 13 of the present invention;

[0041] Fig. 20 is a trend diagram showing the change in the leaching rate of rare earth elements in rare earth-enriched plants as a function of heating time in Examples 13 to 16 of the present invention;

[0042] Fig.21 This is a SEM image of the sample after being treated by the flash Joule heating technology in Example 10 of the present invention. DETAILED DESCRIPTION

[0043] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0044] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0045] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0046] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0047] In a first aspect of an embodiment of the present invention, a method for extracting rare earth elements is proposed, which is characterized in that it includes the following steps: contacting a material containing rare earth elements with a conductive carbon-based material to obtain a precursor; subjecting the precursor to Joule heat treatment and leaching treatment to obtain a rare earth element leachate.

[0048] In the present invention, the conductive carbon-based material has good conductivity and can quickly generate a large amount of Joule heat when current passes through it. This rapid heating ability allows the material to reach a high temperature state in a very short time while maintaining the stability of the material's structure and performance. Therefore, the use of conductive carbon-based materials for Joule heat treatment has the advantages of low energy consumption, no need for solvents or reaction gases, etc., and meets environmental protection requirements.

[0049] By bringing the rare earth element-containing material into contact with the conductive carbon-based material, applying an electric current to generate Joule heat, the material is rapidly heated in a short time. Through high-temperature heating, the mineral phase in the rare earth element-containing material is rapidly decomposed and converted into a more soluble form (such as rare earth oxides or metals), thereby significantly improving the extractability of the rare earth elements and promoting the dissolution and leaching of the rare earth elements.

[0050] Therefore, the method of the present invention has a higher rare earth element extraction rate.

[0051] In some embodiments of the present invention, the temperature of the Joule heat treatment is 700-2000° C., and the time is 1-60 seconds.

[0052] The Joule heat treatment enables the material to quickly reach a high temperature state in a very short time. Therefore, the extraction of rare earth elements in the present invention has high extraction efficiency and extraction rate and is environmentally friendly.

[0053] As an example, the temperature of the Joule heat treatment is 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, etc.

[0054] As an example, the time of the Joule heat treatment is 1s, 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, etc.

[0055] In some embodiments of the present invention, the resistance is controlled to be 1-2Ω during the Joule heat treatment.

[0056] During the Joule heat treatment process, the heat generated is directly related to the resistance. The resistance determines the amount of heat generated when the current passes through the material. By precisely controlling the resistance, the heating power and temperature can be adjusted, thereby achieving precise heat treatment of the material. This can further improve the extraction rate of rare earth elements.

[0057] As an example, the control resistance is 1.1Ω, 1.2Ω, 1.3Ω, 1.4Ω, 1.5Ω, 1.6Ω, 1.7Ω, 1.8Ω, 1.9Ω, 2Ω, etc.

[0058] In some embodiments of the present invention, the Joule heat treatment is performed in a vacuum atmosphere or in air.

[0059] When Joule heat treatment is performed in a vacuum atmosphere, the treated material will not react chemically with oxygen or other gases, thus avoiding common problems such as oxidation, decarburization, and carburization, and maintaining the original purity of the material; in addition, the vacuum environment can reduce heat loss, improve heat treatment efficiency, and help achieve a more uniform temperature field, ensuring the uniformity and consistency of the material during the heat treatment process.

[0060] When Joule heat treatment is performed in air, Joule heat treatment in air can achieve rapid heating and rapid cooling, thereby improving the heat treatment efficiency.

[0061] Thereby, the extraction rate and extraction efficiency of rare earth elements can be further improved.

[0062] In some embodiments of the present invention, the material containing a rare earth element is brought into contact with a conductive carbon-based material, comprising:

[0063] mixing a material containing a rare earth element with a conductive carbon-based material;

[0064] Alternatively, a material containing a rare earth element is placed on one side of the conductive carbon-based material.

[0065] In some embodiments of the present invention, the Joule heat treatment is performed as follows:

[0066] The precursor is loaded into a quartz tube, and graphite rods are used as electrodes on both sides of the quartz tube, or directly placed on a conductive carbon-based material, and connected to a flash Joule heating system for Joule heat treatment.

[0067] In some embodiments of the present invention, the material containing rare earth elements includes at least one of phosphogypsum, permanent magnets, nickel-hydrogen batteries, and rare earth-enriched plants. Therefore, the method of the present invention can be applied to the extraction of rare earth elements from various types of solid materials, and is applicable to the extraction and processing of various complex mineral resources, and has the advantage of wide applicability.

[0068] In some embodiments of the present invention, the conductive carbon-based material includes at least one of carbon black, graphene, graphite, carbon nanotubes, and carbon fibers; the conductive carbon-based material exists in a form including at least one of carbon paper, carbon cloth, and carbon felt.

[0069] In the present invention, the material containing rare earth elements is physically crushed, ground into powder and then fully mixed with the conductive carbon-based material, or the material containing rare earth elements is directly placed on a conductive carbon-based material in the form of carbon paper, carbon cloth or carbon felt, and then the conductive carbon material is connected to a flash Joule heating system for rapid heating. Therefore, the operation method of the present invention is simple and efficient, and has a high rare earth element extraction rate.

[0070] In some embodiments of the present invention, the amount of the material containing rare earth elements added to the precursor is 2 to 3 times the mass of the conductive carbon-based material.

[0071] As an example, the added amount of the material containing rare earth elements is 2 times, 2.2 times, 2.4 times, 2.6 times, 2.8 times, 3 times, etc., the mass of the conductive carbon-based material.

[0072] In some embodiments of the present invention, the solution for leaching treatment includes at least one of a sulfuric acid solution, a nitric acid solution, and a hydrochloric acid solution, and the concentration of the solution is 1 to 5 mol / L.

[0073] In the present invention, the hydrogen ions (H + ) reacts chemically with ions on the surface of rare earth minerals, dissolving rare earth elements from the mineral phase and converting them into soluble salts that enter the solution, thereby recovering the rare earth elements. The inventors have proved through a large number of experiments that acid solutions in this concentration range can effectively leach rare earth elements without wasting acid solutions, thereby significantly improving the leaching rate of rare earth elements.

[0074] As an example, the solution concentration is 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, etc.

[0075] In some embodiments of the present invention, the temperature of the leaching treatment is 85-95° C., and the time of the leaching treatment is 0.5-1.5 h.

[0076] According to the embodiment of the present invention, when the leaching temperature is 85-95° C., the leaching efficiency of rare earth elements can be significantly improved and the leaching time can be reduced, thereby further improving the extraction rate of rare earth elements.

[0077] In some embodiments of the present invention, after the Joule heat treatment, a cooling treatment is also included, and the cooling treatment includes: rapidly cooling the sample obtained after the Joule heat treatment to room temperature through thermal radiation.

[0078] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0079] Embodiment 1:

[0080] This embodiment provides a method for extracting rare earth elements using flash Joule heating technology. The extraction process is as follows: Figure 1 As shown, the following steps are included:

[0081] (1) Select phosphogypsum solid containing 0.1% rare earth, crush it and ball-mill it into powder. The XRD pattern of the sample is as follows: Figure 2 As shown, SEM Figure 3 As shown, EDS spectrum analysis is as follows Figure 4 As shown, TG-DTG analysis is as follows Figure 5 The HSC software was used to analyze the thermodynamic curve of the reaction process during the heating process. Figure 8 This is the thermodynamic calculation diagram of the reaction between calcium sulfate and carbon black in phosphogypsum. Fig. 9 This is the thermodynamic calculation diagram of the reaction between rare earth sulfate and carbon black.

[0082] (2) Phosphogypsum powder and carbon black are mixed in a mass ratio of 2.5:1 and ground evenly to prepare a mixture.

[0083] (3) The mixture is placed in a quartz tube. A high current pulse (voltage intensity 30V, current intensity 27A, heating duration 20s) is applied under vacuum to heat the sample to a maximum temperature of 1900°C, the reaction time is about 1s, and then it is quickly cooled to room temperature. The heating curve is as follows: Figure 6 The XRD of the precursor sample after treatment is shown as Figure 7 shown.

[0084] (4) The product after flash Joule heat treatment was added to a 3 mol / L dilute HCl solution with a liquid-to-solid ratio of 30 mL:1 g, and stirred at 90°C for 1 h. Fig.10 As shown, the rare earth element leaching rate was tested to be 91.91%.

[0085] (5) After the leaching process is completed, the solid residue is collected and its SEM is as follows Fig.13 As shown, EDS spectrum analysis is as follows Fig.14 shown.

[0086] Embodiment 2:

[0087] The difference between Example 2 and Example 1 is that in step (3) of Example 2, the heating duration is 5 seconds, so that the sample is instantly heated to a maximum temperature of about 700°C, the reaction time is about 1 second, and then quickly cooled to room temperature. The heating curve is as follows: Figure 6 The XRD of the treated sample is shown as Figure 7 The leaching rate of rare earth elements is shown in Fig.10 shown.

[0088] Embodiment 3:

[0089] The difference between Example 3 and Example 1 is that in step (3) of Example 3, the heating duration is 10 seconds, the sample is heated to a maximum temperature of about 1350°C, the reaction time is about 1 second, and then it is quickly cooled to room temperature. The heating curve is as follows: Figure 6 The XRD of the treated sample is shown as Figure 7 The leaching rate of rare earth elements is shown in Fig.10 shown.

[0090] Embodiment 4:

[0091] The difference between Example 4 and Example 1 is that in step (3) of Example 4, the reaction current intensity is 25A. In step (4), 3 mol / L dilute HNO 3 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.11 shown.

[0092] Embodiment 5:

[0093] The difference between Example 5 and Example 4 is that in step (4) of Example 5, 0.5 mol / L dilute HNO 3 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.11 shown.

[0094] Embodiment 6:

[0095] The difference between Example 6 and Example 4 is that in step (4) of Example 6, 1 mol / L HNO 3 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.11 shown.

[0096] Embodiment 7:

[0097] The difference between Example 7 and Example 4 is that in step (4) of Example 7, 2 mol / L HNO 3 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.11 shown.

[0098] Embodiment 8:

[0099] The difference between Example 8 and Example 4 is that in step (4) of Example 8, 4 mol / L HNO 3 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.11 shown.

[0100] Embodiment 9:

[0101] The difference between Example 9 and Example 4 is that in step (4) of Example 9, 5 mol / L HNO 3 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.11 shown.

[0102] Embodiment 10:

[0103] The difference between Example 10 and Example 1 is as follows: In step (1) of Example 10, the material is replaced with rare earth-enriched plants, and the SEM spectrum is as follows Fig.15 As shown, TG-DTG analysis is as follows Fig.16 As shown. In step (2), the rare earth-enriched plant is directly placed on the conductive carbon paper. In step (3), the reaction is carried out in air, the reaction temperature is 1000°C, the reaction time is 15s, and the heating curve is as shown Fig.17 As shown. The XRD of the samples before and after treatment is as follows Fig.18 The leaching rate of rare earth elements is shown in Fig.19 The SEM image of the sample after treatment with flash Joule heating technology is shown in Fig.21 shown.

[0104] Embodiment 11:

[0105] The difference between Example 11 and Example 10 is that in step (3) of Example 11, the reaction temperature is 700°C, and the leaching rate of rare earth elements is Fig.19 shown.

[0106] Embodiment 12:

[0107] The difference between Example 12 and Example 10 is that in step (3) of Example 12, the reaction temperature is 800°C, and the leaching rate of rare earth elements is as follows: Fig.19 shown.

[0108] Embodiment 13:

[0109] The difference between Example 13 and Example 10 is that in step (3) of Example 13, the reaction temperature is 900°C, and the leaching rate of rare earth elements is Fig.19 shown.

[0110] Embodiment 14:

[0111] The difference between Example 14 and Example 10 is that in step (3) of Example 14, the reaction time is 1 s, and the leaching rate of rare earth elements is as follows: Fig. 20 shown.

[0112] Embodiment 15:

[0113] The difference between Example 15 and Example 10 is that in step (3) of Example 15, the reaction time is 10 s, and the leaching rate of rare earth elements is as follows: Fig. 20 shown.

[0114] Embodiment 16:

[0115] The difference between Example 16 and Example 10 is that in step (3) of Example 16, the reaction time is 60s, and the leaching rate of rare earth elements is as follows: Fig. 20 shown.

[0116] Embodiment 17:

[0117] The difference between Example 17 and Example 4 is that in step (4) of Example 17, 1 mol / L dilute H 2 SO 4 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.12 shown.

[0118] Embodiment 18:

[0119] The difference between Example 18 and Example 4 is that in step (4) of Example 18, 2 mol / L dilute H 2 SO 4 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.12 shown.

[0120] Embodiment 19:

[0121] The difference between Example 19 and Example 4 is that in step (4) of Example 19, 3 mol / L dilute H 2 SO 4 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.12 shown.

[0122] Embodiment 20:

[0123] The difference between Example 20 and Example 4 is that in step (4) of Example 20, 4 mol / L dilute H 2 SO 4 The solution leaches the rare earth elements, and the leaching rate is as follows Fig.12 shown.

[0124] Embodiment 21:

[0125] The difference between Example 21 and Example 4 is that in step (4) of Example 21, 5 mol / L dilute H 2 SO 4The solution leaches the rare earth elements, and the leaching rate is as follows Fig.12 shown.

[0126] Embodiment 22:

[0127] The difference between Example 22 and Example 17 is that in step (4) of Example 22, 1 mol / L dilute HCl solution is used to leach the rare earth elements, and the leaching rate is as follows: Fig.12 shown.

[0128] Embodiment 23:

[0129] The difference between Example 23 and Example 17 is that in step (4) of Example 23, 2 mol / L dilute HCl solution is used to leach the rare earth elements, and the leaching rate is as follows: Fig.12 shown.

[0130] Embodiment 24:

[0131] The difference between Example 24 and Example 17 is that in step (4) of Example 24, 3 mol / L dilute HCl solution is used to leach the rare earth elements, and the leaching rate is as follows: Fig.12 shown.

[0132] Embodiment 25:

[0133] The difference between Example 25 and Example 17 is that in step (4) of Example 25, 4 mol / L dilute HCl solution is used to leach the rare earth elements, and the leaching rate is as follows: Fig.12 shown.

[0134] Embodiment 26:

[0135] The difference between Example 26 and Example 17 is that in step (4) of Example 26, 5 mol / L dilute HCl solution is used to leach the rare earth elements, and the leaching rate is as follows: Fig.12 shown.

[0136] The reaction conditions and rare earth element leaching rate results of the above examples are shown in Table 1.

[0137] Table 1 Comparison of rare earth element leaching rates of various embodiments

[0138]

[0139]

[0140] From Example 1 to Example 3 in Table 1 and Figure 6 as well as Fig.10It can be seen that the reaction temperature and time of the Joule heat treatment are heated within the temperature and time range of the present invention, and the phosphogypsum solid is heated at an instantaneous high temperature, thereby promoting the dissolution and leaching of rare earth elements in the phosphogypsum solid. In addition, as the heating temperature increases, the more sufficient the heating is, the higher the leaching rate of the rare earth elements is. Therefore, it is shown that the present invention has a higher rare earth element extraction rate.

[0141] It can be seen from Examples 4 to 9 in Table 1 that Fig.11 It can be seen that when other conditions are suitable and unchanged, the leaching rate of rare earth elements increases with the increase of acid solution concentration and finally tends to equilibrium. Therefore, it is shown that rare earth elements can be effectively extracted when the acid solution concentration is 1-5 mol / L.

[0142] From Examples 10 to 16 in Table 1 and Fig.19 as well as Fig. 20 It can be seen that when other conditions are suitable and unchanged, the leaching rate of rare earth elements in rare earth-enriched plants increases with the increase of reaction temperature and reaction time, and the maximum leaching rate can reach 97.23%. Therefore, it is shown that the present invention has a high rare earth element extraction efficiency and extraction rate.

[0143] From Examples 17 to 26 in Table 1 and Fig.12 It can be seen that both sulfuric acid solution and hydrochloric acid solution have good rare earth element leaching rates. Moreover, for the material of phosphogypsum solid, its leaching rate in hydrochloric acid and nitric acid is higher than that of sulfuric acid, indicating that hydrochloric acid and nitric acid are more suitable for the leaching of rare earth elements in phosphogypsum solid, and there may be different types of acid solutions with material preferences. Therefore, it can guide those skilled in the art to select the most suitable acid solution for leaching rare earth elements, thereby improving the extraction rate and reducing the amount of acid solution used.

[0144] This indicates that the method for extracting rare earth elements by Joule heat of the present invention is simple to operate, efficient, and has a high rare earth element extraction efficiency.

[0145] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0146] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for extracting rare earth elements, characterized in that: The following steps are involved: placing a material containing a rare earth element in contact with a conductive carbon-based material to obtain a precursor; The precursor is subjected to Joule heat treatment and leaching treatment to obtain a rare earth element leaching solution.

2. The method according to claim 1, characterized in that The Joule heat treatment is performed at a temperature of 700 to 2000° C. and for a time of 1 to 60 seconds.

3. The method according to claim 1 or 2, characterized in that: During the Joule heat treatment, the resistance is controlled to be 1-2Ω.

4. The method according to any one of claims 1 to 3, characterized in that: The material containing rare earth elements includes at least one of phosphogypsum, permanent magnets, nickel-hydrogen batteries, and rare earth-enriched plants.

5. The method according to any one of claims 1 to 4, characterized in that: The step of bringing the material containing the rare earth element into contact with the conductive carbon-based material comprises: Mixing the material containing the rare earth element with the conductive carbon-based material; Alternatively, the material containing the rare earth element is placed on one side of the conductive carbon-based material.

6. The method according to claim 5, characterized in that The conductive carbon-based material includes at least one of carbon black, graphene, graphite, carbon nanotubes, and carbon fibers; the conductive carbon-based material exists in a form including at least one of carbon paper, carbon cloth, and carbon felt.

7. The method according to claim 5 or 6, characterized in that: When the material containing the rare earth element is mixed with the conductive carbon-based material, the amount of the material containing the rare earth element added to the precursor is 2 to 3 times the mass of the conductive carbon-based material.

8. The method according to any one of claims 1 to 7, characterized in that: The leaching solution includes at least one of a sulfuric acid solution, a nitric acid solution, and a hydrochloric acid solution, and the concentration of the solution is 1 to 5 mol / L.

9. The method according to any one of claims 1 to 8, characterized in that: The temperature of the leaching treatment is 85-95° C., and the time of the leaching treatment is 0.5-1.5 h.

10. The method according to any one of claims 1 to 9, characterized in that: After the Joule heat treatment, a cooling treatment is also included, and the cooling treatment includes: rapidly cooling the sample obtained after the Joule heat treatment to room temperature through thermal radiation.

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