Method for recovering rare earth from rare earth plate slag

Abstract

The invention relates to a method for recovering rare earth from rare earth plate slag, and belongs to the technical field of secondary recovery of rare earth from rare earth waste. The method is characterized by comprising the following steps: (1) adding 30 kilograms of dilute sulphuric acid and 3-15 kilograms of formic acid into one ton of rare earth plate slag, grinding and stirring until the pH value is less than 2, filtering and clarifying to obtain clear liquid for precipitating rare earth and slag for subsequent treatment; and (2) NH4Cl, MgSO4 and H2O2 are prepared in the slag obtained in the step (1), water is added, stirring and precipitation are conducted for 4-6 hours, clarification and filtration are conducted, clear liquid is used for precipitating rare earth, and filtered tailings are conveyed to a slag warehouse after being subjected to filter pressing. The method has the advantages that more than 60% of rare earth can be recycled from the rare earth plate slag, the yield of the rare earth is high, the rare earth is recycled from the rare earth plate slag through secondary utilization, the amazing effect that 2% of rare earth is discharged from the tail of the rare earth plate slag is achieved, the discharge amount of tailings is reduced, and a large amount of national resources are saved.

Description

Technical Field

[0001] The invention relates to a method for recovering rare earth from rare earth plate slag, belonging to the technical field of secondary recovery of rare earth from rare earth waste. Background Art

[0002] There are two main ways to separate rare earths from rare earth concentrates: one is to mix rare earth concentrates with sulfuric acid and roast them, then leach them with water after roasting, and then add ammonium bicarbonate to the leachate to precipitate rare earth carbonate, which is referred to as the acid method. The other is to mix rare earth concentrates with concentrated alkali solution and melt them at high temperature. The rare earth concentrates are decomposed to obtain rare earth hydroxides, and the alkali cakes are washed with water and dissolved with hydrochloric acid, filtered and concentrated to obtain rare earth chlorides, which is referred to as the alkali method.

[0003] At present, most of the Bayan Obo rare earth concentrates are separated by acid method, which will produce a large amount of rare earth carbonate waste residue. Only a small part of these rare earth waste residues can be processed, and most of them are unable to continue to separate rare earths from the slag and are ready to be sent to the tailings storage for permanent storage, which not only occupies a large storage capacity, but also causes a waste of resources.

[0004] Plate slag: waste slag discharged from the plate ore press after rare earth carbonate precipitation and cleaning, ready to be stored in the national slag storage.

[0005] CN117965918A discloses a method and application for recovering rare earth elements from rare earth waste residues, the specific steps of which are: stirring and leaching the crushed rare earth waste residues with a sulfuric acid solution having a pH of 0.7 to 1 at 15 to 35°C, separating the solid and the liquid, and obtaining a rare earth leaching solution and secondary waste residues; wherein the rare earth waste residues are waste residues produced by roasting rare earth concentrates with sulfuric acid. The rare earth waste residues in the method are sulfuric acid rare earth waste residues, which need to be crushed during processing, and the yield of RE0 in the obtained rare earth leaching solution is 35 to 56%.

[0006] CN116676486A discloses a method for recovering iron, phosphorus and rare earth from rare earth waste slag, which is dissolved by sulfuric acid, firstly using P 204 The method comprises the following steps: extracting iron and phosphoric acid with tributyl phosphate, and then recycling the rare earth sulfate solution to the water leaching process to recover rare earth. The method allows iron, phosphorus and rare earth in rare earth waste slag to be enriched and recovered at different treatment stages, but the process adopts multi-stage countercurrent cascade extraction, which increases the complexity of the operation. From the examples thereof, the recovery rate of rare earth is 22-58%. Summary of the invention

[0007] The purpose of the present invention is to provide a method for recovering rare earth from rare earth plate slag which can effectively recover rare earth from waste slag, thereby reducing the discharge of rare earth waste slag and having a high rare earth yield.

[0008] The technical solution of the present invention adopts the following steps: (1) Add 30 kg of dilute sulfuric acid and 3-15 kg of formic acid to one ton of rare earth plate slag, grind and stir until the pH value is less than 2, filter and clarify, and use the clear liquid for rare earth precipitation, and the slag for subsequent treatment; (2) Add NH4Cl, MgSO4 and H2O2 to the residue in step (1), add water and stir to precipitate for 4 to 6 hours, clarify and filter, use the clear liquid to precipitate rare earth, and filter the tailings after filtration and send to the slag storage after filter pressing.

[0009] The concentration of dilute sulfuric acid in step (1) is 10 at; The formic acid concentration in step (1) is 88 at%; The grinding and stirring time in step (1) is 1 hour; The amount of NH4Cl used in step (2) is: calculated based on the theoretical content of rare earth 3 at % in the slag of step (1), which is 0.1 to 0.4 times the rare earth content; The amount of MgSO4 used in step (2) is: calculated based on the theoretical content of rare earth 3 at % in the slag of step (1), which is 2 to 3 times the rare earth content; The concentration of H2O2 in step (2) is 88 at%, and its amount is: calculated based on the theoretical content of rare earth 3 at% in the slag of step (1), which is 0.15 to 0.3 times the rare earth content; The rare earth contained in the clear solution in step (1) and step (2) is rare earth sulfate.

[0010] The beneficial effects of the present invention are: The present invention can recover more than 60% of rare earths from rare earth slag, has a high rare earth yield, realizes secondary utilization and recovery of rare earths from rare earth slag, achieves an amazing effect of 2% rare earths in the tailings of rare earth slag, reduces the discharge of tailings, and saves a large amount of national resources. DETAILED DESCRIPTION

[0011] The present invention is further described below in conjunction with the embodiments, but does not constitute a limitation on the scope of protection of the present invention: Example 1

[0012] Add 30 kg of 5 at % dilute sulfuric acid and 3-15 kg of 2 at % formic acid to one ton of rare earth plate slag, grind and stir for 1 hour, pH value is less than 2, filter and clarify, the clear liquid is used to precipitate rare earth, and the slag is used for subsequent treatment; The slag from the above step is prepared according to the theoretical content of rare earth in the slag of 3 at %, with MgSO4 with twice the rare earth content, NH4Cl with 0.1 times the rare earth content, and hydrogen peroxide with 0.15 times the rare earth content. Water is added and stirred for precipitation for 4 to 6 hours. The slag is clarified and filtered, and the clear liquid is used to precipitate the rare earth. The tailings after filtration are sent to the slag storage after filter pressing. After testing, the rare earth yield is 33.5%, and the rare earth content of the rare earth plate slag is 3.5%. Example 2

[0013] Add 30 kg of 15at% dilute sulfuric acid and 3-15 kg of 17at% formic acid to one ton of rare earth plate slag, grind and stir for 1 hour, pH value is less than 2, filter and clarify, the clear liquid is used to precipitate rare earth, and the slag is used for subsequent treatment; The slag from the above step is prepared according to the theoretical content of rare earth in the slag of 3 at %, with MgSO4 with twice the rare earth content, NH4Cl with 0.45 times the rare earth content, and hydrogen peroxide with 0.35 times the rare earth content. Water is added and stirred for precipitation for 4 to 6 hours. The slag is clarified and filtered, and the clear liquid is used to precipitate the rare earth. The tailings after filtration are sent to the slag storage after filter pressing. After testing, the rare earth yield is 38.8%, and the rare earth content of the rare earth plate slag is 3.2%. Example 3

[0014] Add 30 kg of 10at% dilute sulfuric acid and 15 kg of 5at% formic acid to one ton of rare earth plate slag, grind and stir for 1 hour, pH value is less than 2, filter and clarify, the clear liquid is used to precipitate rare earth, and the slag is used for subsequent treatment; The slag in the above step is prepared according to the theoretical content of rare earth in the slag of 3 at %, and MgSO4 with 2 to 3 times the rare earth content, NH4Cl with 0.1 to 0.4 times the rare earth content, and hydrogen peroxide with 0.15 to 0.3 times the rare earth content. Water is added and stirred for precipitation for 4 to 6 hours. The slag is clarified and filtered, and the clear liquid is used to precipitate the rare earth. The tailings after filtration are sent to the slag storage after filter pressing. After testing, the rare earth yield can reach 61.5%, and the rare earth content of the rare earth plate slag is less than 2%.

[0015] Based on the above test methods, it is known that Example 3 is the best process method and is worthy of promoting large-scale production.

Claims

1. A method for recovering rare earth from rare earth plate slag, characterized in that: Use the following steps: (1) Add 30 kg of dilute sulfuric acid and 3-15 kg of formic acid to one ton of rare earth plate slag, grind and stir until the pH value is less than 2, filter and clarify, and use the clear liquid for rare earth precipitation, and the slag for subsequent treatment; (2) Add NH4Cl, MgSO4 and H2O2 to the residue in step (1), add water and stir to precipitate for 4 to 6 hours, clarify and filter, use the clear liquid to precipitate rare earth, and filter the tailings after filtration and send to the residue storage after filter pressing.

2. The method for recovering rare earth from rare earth plate slag according to claim 1, characterized in that: The concentration of dilute sulfuric acid in step (1) is 10 at %.

3. The method for recovering rare earth from rare earth plate slag according to claim 1, characterized in that: The formic acid concentration in step (1) is 88 at%.

4. The method for recovering rare earth from rare earth plate slag according to claim 1, characterized in that: The grinding and stirring time in step (1) is 1 hour.

5. The method for recovering rare earth from rare earth plate slag according to claim 1, characterized in that: The amount of NH4Cl used in step (2) is: calculated based on the theoretical content of rare earth 3 at % in the slag of step (1), which is 0.1 to 0.4 times the rare earth content.

6. The method for recovering rare earth from rare earth plate slag according to claim 1, characterized in that: The amount of MgSO4 used in step (2) is 2 to 3 times the rare earth content calculated based on the theoretical rare earth content of 3 at % in the slag of step (1).

7. The method for recovering rare earth from rare earth plate slag according to claim 1, characterized in that: The concentration of H2O2 in step (2) is 88 at%, and its dosage is calculated based on the theoretical content of rare earth of 3 at% in the slag of step (1), which is 0.15 to 0.3 times the rare earth content.

8. The method for recovering rare earth from rare earth plate slag according to claim 1, characterized in that: The rare earth contained in the clear solution in step (1) and step (2) is rare earth sulfate.