Method for recovering rare earth chloride from rare earth material

Abstract

The invention provides a method for recovering rare earth chloride from a rare earth material, and belongs to the technical field of rare earth hydrometallurgy. The method provided by the invention comprises the following steps: uniformly mixing a rare earth material with a calcium-containing compound and carbon powder, heating, and carrying out a reaction 1 in a molten state to obtain roasted ore; crushing and grinding the roasted ore, uniformly mixing with water, and then adding hydrochloric acid for reaction 2; after the reaction 2 is finished, carrying out solid-liquid separation to obtain a rare earth chloride solution and leaching residues; the temperature of the reaction 1 is 1500-2000 DEG C, and the time is 0.5-2 hours. According to the method, the rare earth material does not need pretreatment such as grinding and sieving and directly reacts with the calcium-containing compound and the carbon powder, and the technological process is short. The slag rare earth decomposition rate is 98% or above, the rare earth leaching rate is 96% or above, and rare earth resources are effectively recycled.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth hydrometallurgy, in particular to a method for recovering rare earth chloride from rare earth materials. Background Art

[0002] Currently, rare earth recovery from bastnaesite is primarily achieved through oxidative roasting followed by hydrochloric acid leaching. The bastnaesite concentrate is first roasted at approximately 500°C to 600°C, converting it into rare earth oxyfluoride, rare earth oxide, and rare earth fluoride. Leaching is then performed with low-concentration hydrochloric acid to produce a slag and a rare earth chloride solution (low in cerium). The slag undergoes alkaline conversion, water washing to remove fluoride, and hydrochloric acid dissolution to produce a rare earth chloride solution and a cerium-rich slag. After impurities are removed, the rare earth chloride solution is extracted and separated to produce pure rare earth products. This process is lengthy and consumes significant amounts of acid and alkali. Fluorine is discharged as fluoride-containing wastewater during the alkaline conversion process, posing a serious threat to the ecological environment. In recent years, the disclosed prior art mainly focuses on the extraction of fluorine-containing rare earth minerals, while less is disclosed about other types of rare earth minerals (such as iron-thorium materials produced by high-temperature acid smelting of rare earths). The rare earth elements in these materials are difficult to extract using the methods in the disclosed prior art, resulting in a waste of resources.

[0003] CN107083496A discloses a method for extracting rare earth oxide from rare earth materials. The method involves alkali roasting the rare earth material and rare earth polishing powder, followed by water washing, acidification, and impurity removal. The precipitate is filtered, washed, and dried to obtain the finished rare earth oxide. The acidified filtrate is then recycled and added to the alkali roasting process for recycling. The product is then precipitated with oxalic acid, filtered, impurity removed, and calcined to obtain the finished rare earth oxide. This method requires alkali conversion and water washing, and the material must be ground during the alkali conversion process, which places high demands on the particle size of the raw materials. The water washing process also generates a large amount of alkaline wastewater, which has a significant impact on the environment. Furthermore, the process is lengthy, making industrial production difficult.

[0004] CN113564343A discloses a green chemical alkaline defluorination method for roasting fluorine-containing rare earth ores and solid slag. This method includes multiple steps, including traditional alkaline defluorination of roasted fluorine-containing rare earth ores and slag, heating to extract NaF, solid-liquid separation, and heating to extract rare earths. While this method can achieve green chemical defluorination, its lengthy process makes it difficult to commercialize. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for recovering rare earth chloride from rare earth materials.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for recovering rare earth chloride from rare earth materials comprises the following steps:

[0008] After the rare earth material is uniformly mixed with the calcium-containing compound and carbon powder, the mixture is heated and reacted in a molten state to obtain roasted ore.

[0009] The roasted ore is crushed, ground, and mixed evenly with water, and then hydrochloric acid is added to carry out reaction 2;

[0010] After the reaction 2 is completed, the solid and liquid are separated to obtain a rare earth chloride solution and leaching residue;

[0011] The temperature of the reaction 1 is 1500° C.-2000° C., and the time is 0.5-2 h.

[0012] The purpose of adding the calcium compound in the present invention is that when fluorine is contained in the slag, the fluorine reacts with calcium to form calcium fluoride, thereby playing a role in fixing fluorine. In this process, no hydrogen fluoride gas is generated, water washing is not required, and no fluorine-containing wastewater is generated. The generated calcium fluoride is insoluble in hydrochloric acid, so that the fluorine can be recycled. The purpose of adding carbon powder is that the carbon powder preferentially combines with oxygen to eliminate the necessary conditions for the generation of tetravalent cerium in the rare earth material, thereby ensuring that the product contains a large amount of trivalent cerium that is easily soluble in hydrochloric acid. At the same time, the presence of trivalent cerium in a molten state (1500° C.-2000° C.) can convert elements such as praseodymium and neodymium that are difficult to leach in the slag into elements such as praseodymium and neodymium that are easily leached by hydrochloric acid, thereby improving the leaching rate of other rare earth elements.

[0013] In some embodiments of the present invention, the rare earth material is leaching residue after oxidation roasting of bastnaesite, mixed rare earth concentrate or bastnaesite; or the rare earth material is fluorine-containing rare earth waste or waste residue produced by sulfuric acid roasting of rare earth concentrate.

[0014] When the rare earth material is a waste residue obtained through a rare earth recovery process (for example, fluorocarbon cerium ore oxidation roasting product, leached residue after fluorocarbon cerium ore oxidation roasting, fluorine-containing rare earth waste and materials produced by sulfuric acid roasting rare earth concentrate, etc.), the present invention does not specifically limit the preparation process for producing the waste residue, and the waste residue obtained by the rare earth recovery process in the prior art is applicable to this application. For example: Method 1: Fluorocarbon cerium ore is oxidatively roasted at 500°C to 600°C to convert it into rare earth oxyfluoride, rare earth oxide and rare earth fluoride, and then leached with low-concentration hydrochloric acid to obtain a high-quality residue and a rare earth chloride (less cerium) solution. The high-quality residue is then subjected to alkali conversion, water washing to remove fluorine, hydrochloric acid high-quality dissolution and other processes to obtain a rare earth chloride solution and a cerium-rich slag. Method 2: The material produced by sulfuric acid roasting of rare earth concentrate comprises the following specific steps: roasting the rare earth concentrate with concentrated sulfuric acid at a temperature of 400-500° C. for 2-3 hours to form a rare earth sulfate roasted ore; leaching the rare earth sulfate roasted ore with water to obtain a water extract and a water extract residue; neutralizing the water extract with magnesium to obtain a neutralized liquid and a neutralized residue; the neutralized liquid is a pure rare earth sulfate solution; washing the neutralized residue and the water extract residue with sulfuric acid to obtain a slag wash liquid and a secondary slag; washing the secondary slag with water and then neutralizing and removing impurities with magnesium oxide to obtain an external slag, which can be used as the rare earth material used in the present invention.

[0015] In some embodiments of the present invention, the calcium-containing compound is at least one of calcium oxide, calcium hydroxide and calcium carbonate.

[0016] In some embodiments of the present invention, the amount of the calcium-containing compound added is 3% to 40% of the mass of the rare earth material, and the amount of the carbon powder added is 5% to 40% of the mass of the rare earth material.

[0017] In some embodiments of the present invention, the amount of the calcium-containing compound added is 10% to 20% of the mass of the rare earth material, and the amount of the carbon powder added is 10% to 20% of the mass of the rare earth material.

[0018] In some embodiments of the present invention, after reaction 1 is completed, a step of cooling to room temperature is further included.

[0019] In some embodiments of the present invention, the grinding is grinding to -100 mesh.

[0020] In some embodiments of the present invention, the mass volume ratio of the rare earth material to water is 1 g: 4-6 mL.

[0021] In some embodiments of the present invention, when hydrochloric acid is added to carry out the reaction, the temperature of the reaction system is 40-70°C.

[0022] In some embodiments of the present invention, the endpoint of Reaction 2 is: the pH of the reaction system reaches and remains constant at 1. While adding hydrochloric acid to the reaction, the pH of the reaction system is tested (e.g., using pH test paper). If the acidity does not reach pH 1 as the reaction proceeds, hydrochloric acid is continued to be added until the pH of the reaction system reaches 1, and the pH remains constant as the reaction proceeds.

[0023] In some embodiments of the present invention, the leached residue can be returned to the step of uniformly mixing the rare earth material with the calcium-containing compound and the carbon powder to further recover the rare earth chloride and improve the recovery rate.

[0024] The present invention discloses the following technical effects:

[0025] In the method, the rare earth material does not require pretreatment such as grinding and screening, and directly reacts with the calcium-containing compound and carbon powder. The method provided by the present invention is simpler and has a short process flow.

[0026] The method provided by the present invention is applicable to a wide range of rare earth materials, and waste residues or rare earth ores obtained from the rare earth recovery process in the prior art are also applicable to this application. The method provided by the present invention is non-polluting to the atmosphere and water bodies.

[0027] In the method provided by the present invention, the slag rare earth decomposition rate is above 98%, and the rare earth leaching rate is above 96%, which effectively realizes the recycling of rare earth resources, can save energy for enterprises, reduce energy consumption and make full use of mineral resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 The figure is a schematic diagram of the process of recovering rare earth chloride from rare earth materials in the present invention. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0032] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0033] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0034] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0035] Unless otherwise specified, the technical solutions described in the present invention are all conventional solutions in the field, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or are publicly available.

[0036] The analytical method used in the present invention is:

[0037] REO content: analyzed by weight method.

[0038] F content: analyzed by distillation method.

[0039] The REO leaching rate and CeO2, La2O3, Pr6O 11 The calculation formula of Nd2O3 leaching rate is (taking rare earth leaching rate as an example):

[0040] The calculation formula of rare earth leaching rate = (mass of REO in rare earth leaching solution / mass of REO in rare earth material) × 100%.

[0041] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0042] Example 1

[0043] The rare earth material of this embodiment has a REO content of 43.82%. The main rare earth element ratios in REO are: CeO2 accounts for 66.49%, La2O3 accounts for 23.11%, Pr6O 11 It accounts for 2.15%, Nd2O3 accounts for 5.82%, and the F content is 6.77%.

[0044] Weigh 50g of rare earth material, 5g of calcium oxide and 5g of carbon powder and mix them in a graphite crucible. Place the crucible in a muffle furnace and roast it at 1550℃ for 1h. After the roasting is completed, cool it to obtain the roasted ore. Grind the roasted ore and add 200mL of water to make a slurry. Heat it to 40℃, then slowly add hydrochloric acid in batches. Pay attention to the pH value of the reaction process. When the acidity of the reaction system reaches pH=1 and the reaction continues for another 1h, stop the reaction. After the reaction is completed, perform solid-liquid separation to obtain acid leaching residue and acid leaching liquid. Calculate the REO decomposition rate and CeO2, La2O3, Pr6O 11 , Nd2O3 leaching rate, REO leaching rate is 96.89%, CeO2 leaching rate is 97.02%, La2O3 leaching rate is 96.62%, Pr6O 11 The leaching rate is 97.05% and the Nd2O3 leaching rate is 97.58%.

[0045] Example 2

[0046] The rare earth material of this embodiment has a REO content of 33.81%. The main rare earth element ratios in REO are: CeO2 accounts for 59.23%, La2O3 accounts for 30.16%, Pr6O 11 It accounts for 2.77%, Nd2O3 accounts for 7.03%, and the F content is 6.15%.

[0047] Weigh 50g of rare earth material, 7.5g of calcium oxide and 5g of carbon powder and mix them in a graphite crucible. Place the crucible in a muffle furnace and roast it at 1750℃ for 1h. After the roasting, cool it to obtain the roasted ore. Grind the roasted ore and add 250mL of water to make a slurry. Heat it to 50℃ and then slowly add hydrochloric acid in batches. Pay attention to the pH value of the reaction process. When the acidity of the reaction system reaches pH=1 and the reaction continues for 1h, the reaction is stopped. After the reaction is completed, solid-liquid separation is performed to obtain acid leaching residue and acid leaching liquid. The decomposition rate of REO and the content of CeO2, La2O3, and Pr6O are calculated based on the acid leaching residue. 11, Nd2O3 leaching rate, REO leaching rate is 95.89%, CeO2 leaching rate is 95.64%, La2O3 leaching rate is 95.39%, Pr6O 11 The leaching rate is 95.23% and the Nd2O3 leaching rate is 95.75%.

[0048] Example 3

[0049] The rare earth material of this embodiment has a REO content of 34.22%. The main rare earth elements in REO are CeO2 accounting for 55.76%, La2O3 accounting for 29.27%, Pr6O 11 It accounts for 3.03%, Nd2O3 accounts for 8.96%, and the F content is 7.79%.

[0050] Weigh 50g of rare earth material, 5g of calcium oxide and 7.5g of carbon powder and mix them in a graphite crucible. Place the crucible in a muffle furnace and roast it at 1950℃ for 0.5h. After the roasting is completed, cool it to obtain the roasted ore. Grind the roasted ore and add 200mL of water to make a slurry. Heat it to 50℃. Then slowly add hydrochloric acid in batches. Keep an eye on the pH value of the reaction process. When the acidity of the reaction system reaches pH=1 and the reaction continues for 1h, stop the reaction. After the reaction is completed, perform solid-liquid separation to obtain acid leaching residue and acid leaching liquid. Calculate the REO decomposition rate and CeO2, La2O3, Pr6O 11 , Nd2O3 leaching rate, REO leaching rate is 95.88%, CeO2 leaching rate is 97.70%, La2O3 leaching rate is 97.54%, Pr6O 11 The leaching rate is 97.22% and the Nd2O3 leaching rate is 97.73%.

[0051] Example 4

[0052] The rare earth material of this embodiment has a REO content of 41.40%. The main rare earth elements in REO are CeO2 accounting for 55.18%, La2O3 accounting for 30.11%, Pr6O 11 It accounts for 3.92%, Nd2O3 accounts for 9.65%, and the F content is 5.48%.

[0053] Weigh 50g of rare earth material, 10g of calcium oxide, and 5g of carbon powder and mix them in a graphite crucible. Place the crucible in a muffle furnace and roast it at 2000℃ for 0.5h. After the roasting is completed, cool it to obtain the roasted ore. Grind the roasted ore and add 250mL of water to make a slurry. Heat it to 50℃, then slowly add hydrochloric acid in batches. Keep an eye on the pH value of the reaction process. When the acidity of the reaction system reaches pH=1 and the reaction continues for 1h, stop the reaction. After the reaction is completed, perform solid-liquid separation to obtain acid leaching residue and acid leaching liquid. Calculate the REO decomposition rate and CeO2, La2O3, and Pr6O based on the acid leaching residue. 11 , Nd2O3 leaching rate, REO leaching rate is 98.88%, CeO2 leaching rate is 98.69%, La2O3 leaching rate is 98.45%, Pr6O 11 The leaching rate is 98.32% and the Nd2O3 leaching rate is 98.73%.

[0054] Comparative Example 1

[0055] The rare earth material in this comparative example has a REO content of 41.40%, and the main rare earth element ratios in REO are CeO2 accounting for 55.18%, La2O3 accounting for 30.11%, Pr6O 11 It accounts for 3.92%, Nd2O3 accounts for 9.65%, and the F content is 5.48%.

[0056] Weigh 50g of rare earth material and 5g of calcium oxide and mix them in a graphite crucible. Place the crucible in a muffle furnace and roast it at 1600℃ for 2h. After the roasting, the roasted ore is obtained. After grinding the roasted ore, add 200mL of water to make a slurry and heat it to 50℃. Then slowly add hydrochloric acid in batches and pay attention to the pH value of the reaction process. When the acidity of the reaction system is pH=1 and the reaction continues for 1h, the reaction is stopped. After the reaction is completed, solid-liquid separation is performed to obtain acid leaching residue and acid leaching liquid. The decomposition rate of REO and the content of CeO2, La2O3, and Pr6O are calculated based on the acid leaching residue. 11 , Nd2O3 leaching rate, REO leaching rate is 60.16%, CeO2 leaching rate is 42.22%, La2O3 leaching rate is 87.38%, Pr6O 11 The leaching rate is 86.81% and the Nd2O3 leaching rate is 86.88%.

[0057] Comparative Example 2

[0058] Weigh 50g of rare earth material, 5g of calcium oxide and 1g of carbon powder and mix them in a graphite crucible. Place the crucible in a muffle furnace and roast it at 1600℃ for 2h. After the roasting, the roasted ore is obtained. After grinding the roasted ore, add 200mL of water to make a slurry and heat it to 50℃. Then slowly add hydrochloric acid in batches and pay attention to the pH value of the reaction process. When the acidity of the reaction system is pH=1 and the reaction continues for 1h, the reaction is stopped. After the reaction is completed, solid-liquid separation is performed to obtain acid leaching residue and acid leaching liquid. The decomposition rate of REO and the content of CeO2, La2O3, and Pr6O are calculated based on the acid leaching residue. 11 , Nd2O3 leaching rate, REO leaching rate is 61.13%, CeO2 leaching rate is 46.24%, La2O3 leaching rate is 83.23%, Pr6O 11 The leaching rate is 83.23% and the Nd2O3 leaching rate is 83.54%.

[0059] Comparative Example 3

[0060] The REO content in the rare earth material compared in this study is 41.40%, and the main rare earth element ratios in REO are CeO2 accounting for 55.18%, La2O3 accounting for 30.11%, Pr6O 11 It accounts for 3.92%, Nd2O3 accounts for 9.65%, and the F content is 5.48%.

[0061] Weigh 50g of rare earth material, 5g of calcium oxide and 5g of carbon powder and mix them in a graphite crucible. Place the crucible in a muffle furnace and roast it at 1300℃ for 3h. After the roasting, the roasted ore is obtained. After grinding the roasted ore, add 200mL of water to make a slurry and heat it to 50℃. Then slowly add hydrochloric acid in batches and pay attention to the pH value of the reaction process. When the acidity of the reaction system is pH=1 and the reaction continues for 1h, the reaction is stopped. After the reaction is completed, solid-liquid separation is performed to obtain acid leaching residue and acid leaching liquid. The decomposition rate of REO and the content of CeO2, La2O3, and Pr6O are calculated by acid leaching residue. 11 , Nd2O3 leaching rate, REO leaching rate is 31.73%, CeO2 leaching rate is 13.70%, La2O3 leaching rate is 69.04%, Pr6O 11 The leaching rate is 69.52% and the Nd2O3 leaching rate is 66.22%.

[0062] The statistical results of Examples 1-4 and Comparative Examples 1-3 are shown in Table 1. Comparative Examples 1-3 show that temperature and the addition of carbon powder significantly affect the process of the present invention. Increasing the temperature allows the reaction process to proceed in a molten state, which can promote the reaction. The addition of appropriate carbon powder first combines with oxygen to eliminate the necessary conditions for the production of tetravalent cerium in the rare earth material, ensuring that the product contains a large amount of trivalent cerium that is easily soluble in hydrochloric acid. At the same time, the presence of trivalent cerium in a molten state (1500°C-2000°C) can convert elements such as praseodymium and neodymium that are difficult to leach in the slag into elements such as praseodymium and neodymium that are easily leached by hydrochloric acid, thereby increasing the leaching rate of other rare earth elements.

[0063] Table 1 Experimental data of different implementation cases

[0064]

[0065]

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for recovering rare earth chloride from rare earth materials, characterized in that: The following steps are involved: After the rare earth material is uniformly mixed with the calcium-containing compound and carbon powder, the mixture is heated and reacted in a molten state to obtain roasted ore. The roasted ore is crushed, ground, and mixed evenly with water, and then hydrochloric acid is added to carry out reaction 2; After the reaction 2 is completed, the solid and liquid are separated to obtain a rare earth chloride solution and leaching residue; The temperature of the reaction 1 is 1500° C.-2000° C., and the time is 0.5-2 h.

2. The method for recovering rare earth chloride from rare earth materials according to claim 1, characterized in that: The rare earth material is leaching residue after oxidation roasting of bastnaesite, mixed rare earth concentrate or bastnaesite; or the rare earth material is fluorine-containing rare earth waste or waste residue produced by roasting rare earth concentrate with sulfuric acid.

3. The method for recovering rare earth chloride from rare earth materials according to claim 1, characterized in that: The calcium-containing compound is at least one of calcium oxide, calcium hydroxide and calcium carbonate.

4. The method for recovering rare earth chloride from rare earth materials according to claim 1, characterized in that: The added amount of the calcium-containing compound is 3% to 40% of the mass of the rare earth material, and the added amount of the carbon powder is 5% to 40% of the mass of the rare earth material.

5. The method for recovering rare earth chloride from rare earth materials according to claim 1, characterized in that: The grinding is grinding to -100 mesh.

6. The method for recovering rare earth chloride from rare earth materials according to claim 1, characterized in that: The mass volume ratio of the rare earth material to water is 1 g: 4-6 mL.

7. The method for recovering rare earth chloride from rare earth materials according to claim 1, characterized in that: When hydrochloric acid is added to carry out the reaction, the temperature of the reaction system is 40-70°C.

8. The method for recovering rare earth chloride from rare earth materials according to claim 1, characterized in that: The reaction endpoint of the reaction 2 is: the pH in the reaction system is 1 and remains constant.

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