Method for extracting rare earth from rare earth-containing material by ammonia circulation-calcium sulfate precipitation method

Abstract

The embodiment of the invention discloses a method for extracting rare earth from a rare earth-containing material through an ammonia circulation-calcium sulfate precipitation method. The method comprises the following steps: leaching a rare earth-containing material by using a sulfate ion-containing solution under proper conditions to obtain leaching residues and a leaching solution; adding a proper amount of ammonia water into the leachate, fully stirring, adjusting the pH value, and removing impurities to obtain impurity-removed liquid and impurity-removed slag; adding a proper amount of ammonia water into the impurity-removed liquid, fully stirring, adjusting the pH value, and precipitating to obtain a rare earth hydroxide precipitate and a precipitated liquid; a certain amount of calcium-containing alkaline substances are added into the precipitated liquid for causticization, causticized slurry is obtained after sufficient causticization, and the causticized slurry can be divided into an ammonia-rich route and an ammonia-poor route according to the ammonia content of the causticized slurry. According to the method, high-purity calcium sulfate can be co-produced while rare earth resources in the rare earth-containing materials are recovered and enriched, the discharge of high-salinity wastewater is greatly reduced, and the method has a relatively good application prospect.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of rare earth metallurgy, and particularly to a method for extracting rare earth from rare earth-containing materials by an ammonia cycle-calcium sulfate precipitation method. Background Art

[0002] Rare earths are widely used in many fields due to their excellent properties. With the progress of technology, rare earth functional materials have developed vigorously, and the growth of rare earth demand has become increasingly large. The mining technology of ion-adsorbed rare earth has gone through several generations of innovation, developing from the old-fashioned sodium chloride barrel leaching and pond leaching to ammonium sulfate in-situ leaching and ammonium-free leaching. At the same time, the processing and recycling industries of rare earth resources have also developed vigorously. Hydrometallurgy technology is widely used in the processing industry of rare earth-containing materials. In these processes, rare earth raw ores mostly use ammonium salts, sulfates, and chlorides as leaching agents, and rare earth-containing waste residues or other rare earth-containing materials mostly use hydrochloric acid or sulfuric acid as leaching agents, and use oxalic acid, sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, and ammonium bicarbonate as precipitants. Although rare earth can be efficiently extracted or recycled, it is difficult to avoid generating a large amount of high-salt wastewater and ammonia-nitrogen wastewater with complex components. These wastewaters can usually be treated by evaporation, but the precipitated miscellaneous salts are difficult to reuse and can only be finally treated as waste residues.

[0003] Publication No. CN107217139A discloses a chlorine-free mining process for southern ion-type rare earth ores, which uses magnesium sulfate and sodium sulfate as leaching agents, uses magnesium oxide as a primary precipitant, and after the precipitate is dissolved in sulfuric acid and the aluminum is removed by alkali conversion with sodium hydroxide, sodium bicarbonate is used for secondary precipitation. This method has a complex precipitation process and will generate a large amount of high-salt wastewater that is difficult to reuse.

[0004] Publication No. CN109266838A discloses a method for treating bastnasite and a mixed ore containing bastnasite. This method obtains a calcined product by roasting the mixed ore containing bastnasite, uses hydrochloric acid as a leaching agent, uses a selective deposition process to treat the leaching solution, and uses an alkali decomposition process to treat the leaching residue, and finally obtains cerium fluoride and a rare earth chloride solution with less cerium. This method realizes the recovery of fluorine in the leaching solution, but it is difficult to avoid generating high-salt wastewater containing fluorine and chlorine during the alkali decomposition process, and this part of the wastewater is difficult to reuse and treat. Summary of the Invention

[0005] Therefore, the embodiments of the present invention provide a method for extracting rare earth from rare earth-containing materials by an ammonia cycle-calcium sulfate precipitation method.

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

[0007] A method for extracting rare earth from rare earth-containing materials by an ammonia cycle-calcium sulfate precipitation method, the method comprising the following steps:

[0008] (1) Leach the rare earth-containing material with a sulfate ion-containing solution under suitable conditions. After solid-liquid separation of the leaching product, a leaching residue and a leaching solution are obtained;

[0009] (2) Add an appropriate amount of ammonia water to the leaching solution obtained in step (1), stir well to adjust the pH for impurity removal. After sufficient reaction, solid-liquid separation is carried out to obtain a post-impurity-removal solution and an impurity-removal residue;

[0010] (3) Add an appropriate amount of ammonia water to the post-impurity-removal solution obtained in step (2), stir well to adjust the pH for precipitation. After sufficient reaction, solid-liquid separation is carried out to obtain rare earth hydroxide precipitate and a post-precipitation solution. The hydroxide precipitate can be sent to downstream extraction and smelting processes to separate single rare earth element products after acid dissolution;

[0011] (4) Add a certain amount of calcium-containing alkaline substance to the post-precipitation solution obtained in step (3) for causticization. After sufficient causticization, a causticized slurry is obtained, which can be divided into a rich ammonia route and a lean ammonia route depending on the ammonia content in the causticized slurry;

[0012] (5) Rich ammonia route: Carry out solid-liquid separation on the causticized slurry obtained in step (4) to obtain a causticized residue and a post-causticization solution. After the causticized residue is dried to remove ammonia, high-purity gypsum and gaseous ammonia are obtained;

[0013] (6) Lean ammonia route: Carry out aeration stripping on the causticized slurry obtained in step (4) to obtain a deammoniated slurry and gaseous ammonia. After solid-liquid separation of the deammoniated slurry, high-purity gypsum and a deammoniated post-solution with a low salt content can be obtained;

[0014] (7) The gaseous ammonia obtained in step (5) can be absorbed by water or the post-causticization solution and returned to the impurity removal and precipitation processes in steps (2) and (3) as ammonia water. The post-causticization solution obtained in step (5) is rich in ammonia water. Depending on the concentration of ammonia water, it can be directly or after absorbing the gaseous ammonia in step (5) and returned to the impurity removal and precipitation processes in steps (2) and (3) as ammonia water.

[0015] Further, in step (1), the rare earth-containing material includes a mixture formed by one or more of rare earth-containing waste residues, rare earth raw ores, rare earth resource recovery, and common rare earth intermediate products in the rare earth smelting and separation process;

[0016] The sulfate ion-containing solution includes a mixture formed by one or more of ammonium sulfate, ammonium bisulfate, sodium sulfate, sodium bisulfate, magnesium sulfate, potassium sulfate, potassium bisulfate, aluminum sulfate, potassium alum, sodium alum, ferric aluminum sulfate, ferric sulfate, ferrous sulfate, ammonium ferrous sulfate, potassium ferric sulfate, or sulfuric acid. The concentration of the sulfate ion-containing solution is any concentration.

[0017] Further, in step (2), the concentration of the ammonia water is any concentration, and the pH range for impurity removal is 3 - 6, with 4.8 - 5.4 being preferred.

[0018] Further, in step (3), the concentration of ammonia water is any concentration, and the precipitation pH value ranges from 5 to 10, preferably 7 to 8.

[0019] Further, in step (4), the calcium-containing alkaline substance includes a mixture formed by compounding one or more of calcium oxide, calcium hydroxide, calcium carbonate, and calcium bicarbonate, or a slurry, suspension, or aqueous solution prepared with water.

[0020] The embodiments of the present invention have the following advantages:

[0021] A method for extracting rare earths from rare earth-containing materials by an ammonia cycle-calcium sulfate method provided by the present invention can recover and enrich rare earth resources in rare earth-containing materials while co-producing high-purity calcium sulfate, and greatly reduce the discharge of high-salt wastewater, having good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, other implementation drawings can be obtained by extension based on the provided drawings without creative efforts.

[0023] Figure 1 It is a process flow diagram of the method for extracting rare earths from rare earth-containing materials by the ammonia cycle-calcium sulfate precipitation method provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following specific embodiments illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] Example 1

[0026] Take 1000 g of ion-adsorbed rare earth ore soil (rare earth content 1.20‰, calculated as oxide), leach it with 1500 mL of ammonium sulfate solution with a mass concentration of 4.0% to obtain 1000 mL of leaching mother liquor with a rare earth concentration of 1.05 g / L (calculated as oxide). After the leaching solution is adjusted to pH 5.4 for impurity removal and precipitation with 8 mL of 25% ammonia water and then filtered, the filtrate is further adjusted to pH 7.5 for precipitation with 4 mL of 25% ammonia water to obtain 1.25 g of rare earth hydroxide precipitate. Add 3 g of quicklime to the post-precipitation solution for neutralization and heat aeration for stripping. The gas phase is absorbed by 50 mL of water to obtain 50 mL of 6% ammonia water, and the liquid phase is filtered to obtain 7.2 g of calcium sulfate.

[0027] Example 2

[0028] Take 100 g of powdered neodymium-iron-boron waste (rare earth content 10%, calculated as oxide), leach it with 500 mL of sulfuric acid solution with a mass concentration of 20%, wash it with 300 mL of clear water to obtain 750 mL of leaching mother liquor with a rare earth concentration of 12.5 g / L (calculated as oxide). After the leaching solution is adjusted to pH 5.4 for impurity removal and precipitation with 315 mL of 25% ammonia water and then filtered, the filtrate is further adjusted to pH 7.5 for precipitation with 35 mL of 25% ammonia water to obtain 14.5 g of rare earth hydroxide precipitate. Add 45 g of quicklime to the post-precipitation solution and filter to obtain 1000 mL of filtrate with an ammonia content of 6%. The filter residue is dried and deammoniated to obtain 105 g of calcium sulfate, and the gas phase is absorbed by the filtrate to obtain 1000 mL of 8% ammonia water.

[0029] Although the present invention has been described in detail above with general descriptions and specific examples, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A method for extracting rare earths from rare earth-containing materials by an ammonia cycle-calcium sulfate precipitation method, characterized in that, The method includes the following steps: (1) Leach the rare earth-containing material with a sulfate ion-containing solution under suitable conditions. After solid-liquid separation of the leaching product, a leaching residue and a leaching solution are obtained; (2) Add an appropriate amount of ammonia water to the leaching solution obtained in step (1), stir well to adjust the pH for impurity removal. After full reaction, solid-liquid separation is carried out to obtain a post-impurity removal solution and an impurity removal residue; (3) Add an appropriate amount of ammonia water to the post-impurity removal solution obtained in step (2), stir well to adjust the pH for precipitation. After full reaction, solid-liquid separation is carried out to obtain rare earth hydroxide precipitate and a post-precipitation solution. Among them, the hydroxide precipitate can be sent to downstream extraction and smelting processes to separate single rare earth element products after acid dissolution; (4) Add a certain amount of calcium-containing alkaline substance to the post-precipitation solution obtained in step (3) for causticization. After full causticization, a causticization slurry is obtained, which can be divided into a rich ammonia route and a lean ammonia route depending on the ammonia content in the causticization slurry; (5) Rich ammonia route: Carry out solid-liquid separation on the causticization slurry obtained in step (4) to obtain a causticization residue and a post-causticization solution. Among them, the causticization residue is dried to remove ammonia to obtain high-purity gypsum and gaseous ammonia; (6) Lean ammonia route: Carry out aeration stripping on the causticization slurry obtained in step (4) to obtain a deammoniated slurry and gaseous ammonia. After solid-liquid separation of the deammoniated slurry, high-purity gypsum and a deammoniated solution with a low salt content can be obtained; (7) The gaseous ammonia obtained in step (5) can be absorbed by water or the post-causticization solution and returned to the impurity removal and precipitation processes in steps (2) and (3) as ammonia water. The post-causticization solution obtained in step (5) is rich in ammonia water. Depending on the concentration of ammonia water in it, it can be directly or after absorbing the gaseous ammonia in step (5) and returned to the impurity removal and precipitation processes in steps (2) and (3) as ammonia water.

2. The method for extracting rare earths from rare earth-containing materials by the ammonia cycle-calcium sulfate precipitation method according to claim 1, characterized in that, In step (1), the rare earth-containing material includes a mixture formed by one or more of rare earth-containing waste residues, rare earth raw ores, rare earth resource recovery, and rare earth intermediate products commonly found in rare earth smelting and separation processes; the sulfate ion-containing solution includes a mixture formed by one or more of ammonium sulfate, ammonium bisulfate, sodium sulfate, sodium bisulfate, magnesium sulfate, potassium sulfate, potassium bisulfate, aluminum sulfate, potassium alum, sodium alum, ferric aluminum sulfate, ferric sulfate, ferrous sulfate, ammonium ferrous sulfate, potassium ferric sulfate, or sulfuric acid. The concentration of the sulfate ion-containing solution is any concentration.

3. The method for extracting rare earths from rare earth-containing materials by the ammonia cycle-calcium sulfate precipitation method according to claim 1, characterized in that, In step (2), the concentration of the ammonia water is any concentration, and the pH value range for impurity removal is 3 - 6, with 4.8 - 5.4 being preferred.

4. The method for extracting rare earths from rare earth-containing materials by ammonia cycle-calcium sulfate precipitation method according to claim 1, characterized in that, In step (3), the concentration of the ammonia water is any concentration, and the pH value range for precipitation is 5 - 10, with 7 - 8 being preferred.

5. The method for extracting rare earths from rare earth-containing materials by the ammonia cycle-calcium sulfate precipitation method according to claim 1, characterized in that, In step (4), the calcium-containing alkaline substance includes a mixture formed by one or more of calcium oxide, calcium hydroxide, calcium carbonate, calcium bicarbonate, or a slurry, suspension, or aqueous solution prepared with water.

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