Method for reducing the chlorine content in rare earth oxides and use of ammonium acetate solution
By combining co-current droplet addition with water washing, the problem of excessive chlorine content in rare earth oxides has been solved, achieving a significant reduction in chlorine content and environmentally friendly carbon reduction. This method is applicable to fields such as glass, ceramics, catalysis, and magnetic materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BAOTOU RESEARCH INSTITUTE OF RARE EARTHS
- Filing Date
- 2024-01-23
- Publication Date
- 2026-06-12
AI Technical Summary
The high chlorine content in existing rare earth oxides affects their downstream applications, especially the electrolytic preparation of rare earth metals, and existing methods have failed to effectively reduce the chlorine content.
A rare earth chloride solution and ammonia water were added to an ammonium acetate solution in a co-current dropwise manner to react and generate a reaction suspension. The suspension was then subjected to solid-liquid separation and water washing, and finally calcined in an air atmosphere. The calcination temperature and time were controlled to reduce the chlorine content in the rare earth oxides.
It effectively reduces the chlorine content in rare earth oxides to less than 0.1 wt%, meeting the requirements of downstream applications and avoiding the generation of carbon dioxide, thus achieving the goal of environmental protection and carbon reduction.
Smart Images
Figure BDA0004677486810000081
Abstract
Description
Technical Field
[0001] This invention relates to a method for reducing the chlorine content in rare earth oxides and the use of ammonium acetate solution, particularly to a method for reducing the chlorine content in rare earth oxides obtained based on an ammonia precipitation process for rare earth chlorides and the use of ammonium acetate solution. Background Technology
[0002] Rare earth oxides are generally the final products of rare earth smelting and separation, and also the main raw materials for preparing other rare earth compounds. They are widely used in glass, ceramics, catalysis, magnetic materials, and other fields. Ammonia precipitation of rare earth chlorides is an important process for the separation and extraction of rare earths in rare earth hydrometallurgy. The precipitate from ammonia precipitation of rare earth chlorides is then subjected to high-temperature calcination to obtain the corresponding rare earth oxides.
[0003] Chloride ions and hydroxide ions have similar electronegativity and ionic radii, so in this process, Cl... - The existence of Cl in the precipitate is quite complex, involving both physical and chemical adsorption on the surface and within the precipitate. Among these, the physically adsorbed Cl... - Cl can be removed by washing with water, while Cl in the chemical coordination adsorption state... - Washing with water cannot remove it. Therefore, the current problem with this process is the presence of Cl in the rare earth oxide product. - Excessive impurity content, reaching 5-10%, negatively impacts downstream applications of rare earth oxides, particularly the electrolytic preparation of rare earth metals. Therefore, effectively reducing the chlorine content in the rare earth oxide precursor during the ammonia precipitation of rare earth oxides, and consequently reducing the chlorine content in the resulting rare earth oxides, is a pressing issue that needs to be addressed.
[0004] CN101805007A discloses a method for preparing rare earth hydroxide nanorods, comprising the following steps: dissolving hexadecyltrimethylammonium bromide in deionized water to obtain a CTAB solution; dissolving a rare earth chloride in deionized water to obtain a chloride solution; adding ammonia dropwise to the CTAB solution to obtain a mixed solution; adding the chloride solution dropwise to the above mixed solution, stirring, and aging; washing the precipitate after centrifugation with distilled water, and drying to obtain rare earth hydroxide nanorods. The key point of this preparation method is the preparation of rare earth hydroxides with specific shapes, although the chlorine content remains relatively high. The rare earth oxides obtained after calcination of the rare earth hydroxides prepared by this method still have a high chlorine content.
[0005] CN102701260A discloses a method for spray pyrolysis of a rare earth chloride solution containing additives. This method involves mixing a trivalent rare earth chloride solution of a certain concentration with additives, then mixing it with a gas carrier at a certain flow rate, and spraying the mixture into a calcining furnace in a spray form for calcination. The resulting product is then naturally cooled to obtain a powder with a trivalent rare earth hydroxide content of 90-99 wt%. This method does not employ an ammonia precipitation process and fails to improve upon existing processes. Summary of the Invention
[0006] In view of this, one object of the present invention is to provide a method for reducing the chlorine content in rare earth oxides, which reduces the chlorine content in the resulting rare earth oxide precursor, thereby reducing the chlorine content in the resulting rare earth oxide. The chlorine content in the rare earth oxide can be less than 0.1 wt%. Another object of the present invention is to provide a use for an ammonium acetate solution. The present invention achieves the above objects using the following technical solutions.
[0007] On one hand, the present invention provides a method for reducing the chlorine content in rare earth oxides, comprising the following steps:
[0008] 1) Rare earth chloride solution and ammonia water are added dropwise to the base liquid in a co-current manner to react and obtain a reaction suspension; wherein, the base liquid is ammonium acetate solution;
[0009] 2) The reaction suspension is subjected to solid-liquid separation, and the solid is washed with water to obtain rare earth oxide precursors.
[0010] According to the method of the present invention, preferably, in step 1), the molar ratio of the solute in the ammonia water added during the parallel-flow dripping process to the rare earth ions in the rare earth chloride solution is controlled to be 2.8 to 3.4:1.
[0011] According to the method of the present invention, preferably, in step 1), the pH value of the reaction system is controlled to be 7.0 to 7.5 during the parallel drop addition; and the temperature during the parallel drop addition is 40 to 80°C.
[0012] According to the method of the present invention, preferably, in step 1), the volume of the bottom liquid is one-half to three-quarters of the sum of the volumes of the rare earth chloride solution and the ammonia water.
[0013] According to the method of the present invention, preferably, in step 1), the concentration of rare earth chloride solution is 95-300 g / L; the concentration of ammonia water is 3.5-5 mol / L; and the concentration of ammonium acetate solution is 0.5-2.2 mol / L.
[0014] According to the method of the present invention, preferably, in step 1), after the parallel droplet addition is completed, the pH value of the reaction solution is adjusted to 8.5-11; after the parallel droplet addition is completed, the reaction is stirred for 20-30 minutes to obtain a reaction suspension.
[0015] According to the method of the present invention, preferably, in step 2), the solid is washed with water until the washing solution is substantially free of chloride ions.
[0016] The method according to the present invention preferably further includes the following steps:
[0017] 3) The rare earth oxide precursor obtained in step 2) is calcined to obtain rare earth oxides; wherein the chlorine content in the obtained rare earth oxides is less than or equal to 0.1 wt%.
[0018] According to the method of the present invention, preferably, in step 3), the calcination temperature is 800-1100℃ and the calcination time is 1-6h.
[0019] On the other hand, the present invention also provides the use of ammonium acetate solution in reducing the chlorine content in rare earth oxides, comprising the following steps:
[0020] 1) Rare earth chloride solution and ammonia water are added dropwise to the base liquid in a co-current manner to react and obtain a reaction suspension; wherein, the base liquid is ammonium acetate solution;
[0021] 2) The reaction suspension is subjected to solid-liquid separation, and the solid is washed with water to obtain rare earth oxide precursors.
[0022] The method according to the present invention reduces the chlorine content in the rare earth oxide precursor, resulting in a lower chlorine content in the obtained rare earth oxide. The chlorine content in the obtained rare earth oxide is less than or equal to 0.1 wt%. The method of using ammonium acetate solution as the base liquid during the co-current addition of the rare earth chloride solution and ammonia water significantly reduces the chlorine content in the obtained rare earth oxide. Detailed Implementation
[0023] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.
[0024] The method for reducing the chlorine content in rare earth oxides according to the present invention employs an ammonia precipitation process. Compared with the carbon precipitation transformation using ammonium bicarbonate solution in the prior art (e.g., in CN114671450A, samarium chloride solution and ammonium bicarbonate solution are added in parallel to generate samarium carbonate precursor), this method can avoid the generation of carbon dioxide in the roasting step, thereby achieving the purpose of reducing carbon emissions.
[0025] The method for reducing the chlorine content in rare earth oxides according to the present invention includes the following steps:
[0026] (1) Co-current dropwise addition step; (2) Precursor preparation step; (3) Calcination step. In addition, it includes the preparation step of ammonium acetate solution. These are described in detail below.
[0027] <Steps for parallel-flow dripping>
[0028] A rare earth chloride solution and ammonia water are added dropwise in a co-current manner to a base solution to produce a reaction suspension; wherein the base solution is an ammonium acetate solution. This invention surprisingly discovers that using an ammonium acetate solution as the base solution, followed by the co-current dropwise addition of the rare earth chloride solution and ammonia water, can reduce the chlorine content in the obtained precursor, thereby reducing the chlorine content in the obtained rare earth oxides. If ammonium acetate is not added and only water is used as the base solution, the technical effect of this invention cannot be achieved. This invention believes that by adding ammonium acetate as an acid-base stabilizer to the reaction system, the pH value during the reaction can be lowered to control the concentration of hydroxide ions, thereby reducing the relative supersaturation of the precipitated product (i.e., the rare earth oxide precursor), inhibiting the nucleation rate of the precipitated crystals, and promoting crystal growth, thus reducing the chlorine content in the rare earth oxide precursor. - The content of impurities is reduced, thereby decreasing the chlorine content in the resulting rare earth oxides.
[0029] Rare earth chloride solution refers to an aqueous solution of rare earth chloride. The rare earth elements in the rare earth chloride solution are not particularly limited, but are preferably selected from one or more of lanthanum, cerium, praseodymium, and neodymium.
[0030] The concentration of the rare earth chloride solution can be 95–300 g / L, preferably 100–200 g / L, and more preferably 100–150 g / L. The concentration of ammonia water can be 3.5–5 mol / L, preferably 4–5 mol / L, and more preferably 4–4.5 mol / L. This is beneficial for promoting the crystal growth of the precipitated product and reducing post-processing costs.
[0031] Ammonium acetate solution refers to an aqueous solution of ammonium acetate, which can be prepared by dissolving solid ammonium acetate in deionized water. The concentration of the ammonium acetate solution is 0.5–2.2 mol / L, preferably 0.8–2.0 mol / L, and more preferably 1.0–1.5 mol / L. The ammonium acetate solution serves as the base solution, and no seed crystals are present in the ammonium acetate solution.
[0032] The volume of the base liquid can be one-half to three-quarters of the sum of the volumes of the rare earth chloride solution and the ammonia solution, preferably two-thirds.
[0033] During co-current dropping, the pH of the reaction system is controlled at 7.0–7.5. The molar ratio of the solute in the added ammonia water to the rare earth ions in the rare earth chloride solution is controlled at 2.8–3.4:1, preferably 2.9–3.3:1, and more preferably 3.0–3.2:1. This facilitates the complete conversion of rare earth chloride to rare earth hydroxide and helps reduce the supersaturation of the precursor product during the reaction, thereby reducing the Cl content in the precursor product. - content.
[0034] When adding the mixture dropwise, the stirring speed can be controlled at 150–300 rpm, preferably 200–275 rpm, and more preferably 225–250 rpm. This is beneficial for the diffusion of rare earth ions and hydroxide ions in the reaction system and for crystal growth, thereby reducing the Cl content in the precursor. - content.
[0035] The reaction temperature during co-current dropwise addition can be 40–80°C, preferably 50–80°C. For example, it can be 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C.
[0036] After the parallel-flow addition is complete, adjust the pH of the reaction solution to 8.5–11, preferably 9.0–10.5, and more preferably 9.5–10.0. This facilitates complete precipitation of rare earth ions and improves the yield.
[0037] In some implementations, after the addition is complete, the reaction is stirred for another 20 to 30 minutes to obtain a reaction suspension.
[0038] <Steps to obtain the precursor>
[0039] The reaction suspension was subjected to solid-liquid separation, and the solid was washed with water to obtain rare earth oxide precursors. These rare earth oxide precursors are rare earth hydroxides.
[0040] Solid-liquid separation can be achieved by filtration or centrifugation, with filtration being preferred. When washing the solid with water, deionized water, purified water, or distilled water can be used.
[0041] According to one embodiment of the present invention, the reaction suspension is filtered to obtain a filter cake and a mother liquor. The filter cake is washed multiple times with deionized water until the washing liquid is substantially free of Cl. - The test can be done using silver nitrate; the solution continues to be tested until the washing solution does not become cloudy upon contact with the silver nitrate solution.
[0042] Preferably, after washing the solid with water until it is substantially free of chloride ions, the solid is then washed with a C1-C3 alkyl alcohol to obtain a rare earth oxide precursor, which facilitates the next step of calcination. C1-C3 alkyl alcohols refer to alkyl alcohols with 1 to 3 carbon atoms. In some specific embodiments, the C1-C3 alkyl alcohol may be selected from methanol, ethanol, or isopropanol.
[0043] <Roasting Steps>
[0044] The obtained rare earth oxide precursor is calcined to obtain rare earth oxides. In this invention, calcination is performed in an air atmosphere.
[0045] The chlorine content in the obtained rare earth oxide is less than or equal to 0.1 wt%, preferably less than 0.1 wt%, and more preferably less than 0.08 wt%.
[0046] The calcination temperature can be 800–1100℃, preferably 850–1000℃, and more preferably 950–1000℃. The calcination time can be 1–6 hours, preferably 2–5 hours, and more preferably 3–4 hours. This is beneficial for obtaining rare earth oxides and further reducing the chlorine content.
[0047] According to a specific embodiment of the present invention, a method for reducing the chlorine content in rare earth oxides includes the following specific steps:
[0048] 1) At 40–80°C, rare earth chloride solution and ammonia water are added dropwise to the base liquid in a co-current manner to react and obtain a reaction suspension; wherein, the base liquid is ammonium acetate solution;
[0049] 2) The reaction suspension is subjected to solid-liquid separation, and the solid is washed with water to obtain rare earth oxide precursors;
[0050] 3) The rare earth oxide precursor obtained in step 2) is calcined to obtain rare earth oxides; wherein the chlorine content in the obtained rare earth oxides is less than or equal to 0.1 wt%.
[0051] <Applications>
[0052] This invention also provides the use of ammonium acetate solution in reducing the chlorine content in rare earth oxides, comprising the following steps:
[0053] 1) Rare earth chloride solution and ammonia water are added dropwise to the base liquid in a co-current manner to react and obtain a reaction suspension; wherein, the base liquid is ammonium acetate solution;
[0054] 2) The reaction suspension is subjected to solid-liquid separation, and the solid is washed with water to obtain rare earth oxide precursors. Detailed descriptions are provided above and will not be repeated here.
[0055] The test methods for the following embodiments and comparative examples are described below:
[0056] REO content: Tested using the EDTA volumetric method.
[0057] Chlorine content in rare earth oxides: tested using silver nitrate turbidimetric method.
[0058] Example 1
[0059] Dissolve 15.4g of ammonium acetate solid in 200mL of deionized water to prepare a 1.0mol / L ammonium acetate solution for later use.
[0060] At 80℃ and 250 rpm, 200 mL of 100 g / L lanthanum chloride solution and 100 mL of 4 mol / L ammonia solution were added dropwise in a co-current manner to a reactor containing the prepared ammonium acetate solution (as the base solution). The molar ratio of solute in the ammonia solution to lanthanum ions in the lanthanum chloride solution was controlled at 3.0:1 during the dropwise addition. The pH of the reaction system was maintained between 7.0 and 7.5. After the addition was complete, the pH of the reaction solution was adjusted to 9.0, and stirring was continued for 30 min to obtain a reaction suspension.
[0061] The reaction suspension obtained above was filtered, and the filter cake was washed with deionized water until the washing solution did not produce turbidity when it came into contact with silver nitrate solution (i.e., there were basically no chloride ions in the washing solution). The filter cake was then washed once with ethanol to obtain the lanthanum oxide precursor.
[0062] The lanthanum oxide precursor obtained above was calcined at 1000℃ for 3 hours to obtain a low-chloride lanthanum oxide product. The chlorine content in lanthanum oxide is shown in Table 1 below.
[0063] Examples 2-3 and Comparative Examples 1-3
[0064] Except for the process parameters shown in Table 1, everything else is the same as in Example 1.
[0065] Table 1
[0066]
[0067] Note: The rare earth chloride solution concentrations in Table 1 are calculated using REO values; M in Table 1 represents the molar ratio of the solute in the ammonia water added to the bottom solution during the parallel-flow dropping process to the rare earth ions in the rare earth chloride solution. An ammonium acetate solution concentration of 0 means that no ammonium acetate solution was added, and only water was added as the bottom solution. When the ammonium acetate solution concentration is greater than 0, the bottom solution is an ammonium acetate solution.
[0068] As can be seen from the comparison between Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, the method of the present invention can effectively reduce the chlorine content (i.e., Cl) in rare earth oxide products during the ammonia precipitation rare earth process. - content).
[0069] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.
Claims
1. A method for reducing the chlorine content in rare earth oxides, characterized in that, Includes the following steps: 1) A rare earth chloride solution and ammonia water are added dropwise to a base solution in a parallel flow to react and obtain a reaction suspension; wherein, the base solution is an ammonium acetate solution; the volume of the base solution is one-half to three-quarters of the sum of the volumes of the rare earth chloride solution and the ammonia water; the concentration of the rare earth chloride solution is 95–300 g / L; the concentration of the ammonia water is 3.5–5 mol / L; and the concentration of the ammonium acetate solution is 0.5–2.2 mol / L. Specifically, the molar ratio of the solute in the ammonia water and the rare earth ions in the rare earth chloride solution during the co-current dropping process is controlled to be 2.8–3.4:1; the pH of the reaction system during the co-current dropping process is controlled to be 7.0–7.5; the temperature during the co-current dropping process is 40–80℃; the stirring speed during the co-current dropping process is controlled to be 150–300 rpm; and after the co-current dropping process is completed, the pH of the reaction solution is adjusted to 8.5–11. 2) The reaction suspension was subjected to solid-liquid separation, and the solid was washed with water to obtain rare earth oxide precursors; 3) The rare earth oxide precursor obtained in step 2) is calcined to obtain rare earth oxides; wherein the chlorine content in the obtained rare earth oxides is less than or equal to 0.1 wt%.
2. The method according to claim 1, characterized in that, In step 1), after the dropwise addition is complete, continue stirring for 20-30 minutes to obtain a reaction suspension.
3. The method according to claim 1, characterized in that, In step 2), the solid is washed with water until the washing solution is basically free of chloride ions.
4. The method according to claim 1, characterized in that, In step 3), the roasting temperature is 800–1100℃ and the roasting time is 1–6 h.
5. The use of an ammonium acetate solution in reducing the chlorine content in rare earth oxides, characterized in that, Includes the following steps: 1) A rare earth chloride solution and ammonia water are added dropwise to a base solution in a parallel flow to react and obtain a reaction suspension; wherein, the base solution is an ammonium acetate solution; the volume of the base solution is one-half to three-quarters of the sum of the volumes of the rare earth chloride solution and the ammonia water; the concentration of the rare earth chloride solution is 95–300 g / L; the concentration of the ammonia water is 3.5–5 mol / L; and the concentration of the ammonium acetate solution is 0.5–2.2 mol / L. Specifically, the molar ratio of the solute in the ammonia water and the rare earth ions in the rare earth chloride solution during the co-current dropping process is controlled to be 2.8–3.4:1; the pH of the reaction system during the co-current dropping process is controlled to be 7.0–7.5; the temperature during the co-current dropping process is 40–80℃; the stirring speed during the co-current dropping process is controlled to be 150–300 rpm; and after the co-current dropping process is completed, the pH of the reaction solution is adjusted to 8.5–11. 2) The reaction suspension was subjected to solid-liquid separation, and the solid was washed with water to obtain rare earth oxide precursors; 3) The rare earth oxide precursor obtained in step 2) is calcined to obtain rare earth oxides; wherein the chlorine content in the obtained rare earth oxides is less than or equal to 0.1 wt%.