Method for preparing high-purity rare earth compound through complex precipitation

Abstract

The invention belongs to the field of rare earth hydrometallurgy, and discloses a method for preparing a high-purity rare earth compound through complex precipitation, which comprises the following steps: adding a rare earth compound to be purified into an inorganic compound, and dissolving to obtain rare earth feed liquid; adding an organic complexing agent into the rare earth material liquid according to a preset first proportion, adjusting by using an auxiliary adjusting agent, and adjusting the pH value of the system to a preset value to obtain a rare earth complexing material liquid; and adding a precipitant into the rare earth complexing material liquid according to a preset second proportion for precipitation, and filtering, washing and roasting to obtain the purified rare earth oxide. By adding the organic complexing agent, the occurrence form of rare earth and impurity elements is controlled; the addition of the auxiliary regulator further regulates the form distribution of the rare earth and impurity elements, so that the rare earth is selectively precipitated in the precipitation process, impurity precipitation is reduced, the separation effect in the precipitation process is further improved, and the purification method is simple in process operation and low in production cost.

Description

Technical Field

[0001] This invention relates to the field of rare earth hydrometallurgy, specifically to a method for preparing high-purity rare earth compounds by complexation precipitation. Background Technology

[0002] High-purity rare earth compounds are the material basis for high-performance rare earth magnetic, optical, and electrical functional materials, and are widely used in strategic emerging industries such as national defense, petrochemicals, glass and ceramics, new energy vehicles, integrated circuits, and 5G communications.

[0003] The purity of high-purity rare earth compounds is a key factor affecting the magnetic, optical, and electrical properties of materials. The presence of non-rare earth impurities has a significant impact on the magnetic, optical, and electrical properties of rare earth materials. For example, the presence of alkaline earth metals such as Ca and Mg increases the alkalinity of rare earth polishing slurries and reduces the ionic conductivity of rare earth oxygen sensors; while the presence of Al reduces the saturation magnetization and anisotropic field of NdFeB magnets; and the presence of transition metal impurities such as Cu, Co, Mn, and Zn reduces the Curie temperature, anisotropic field, coercivity, saturation magnetization, and causes unnecessary coloration. The impurity content requirements for high-purity rare earth compounds used in high-performance laser fibers, electronic ceramic materials, superconducting materials, and scintillation crystal materials are even more stringent, with some sensitive impurities needing to be removed to below 0.5 ppm.

[0004] Currently, the main methods for producing high-purity rare earth compounds include solvent extraction, ion exchange or adsorption, and precipitation. Solvent extraction suffers from problems such as easy emulsification of the solution, large solvent loss, and environmental pollution caused by the organic phase, and its purity is difficult to meet standards. Ion exchange can separate multiple elements in a single operation, with the advantages of low pollution and high product purity, but the production cycle is long, continuous processing capacity is limited, and the process cost is high. Precipitation is simple in principle and equipment and easy to operate, but it suffers from poor separation effect and is usually used as a pretreatment for the rough purification of rare earth feed solutions. It is difficult to obtain high-purity rare earth compounds with low impurity content through precipitation. Summary of the Invention

[0005] (I) Purpose of the Invention

[0006] The purpose of this invention is to provide a method for preparing high-purity rare earth compounds by complexation precipitation, which can improve the separation effect and increase the purity of rare earth compounds.

[0007] (II) Technical Solution

[0008] To address the above problems, this invention provides a method for preparing high-purity rare earth compounds via complexation precipitation, comprising:

[0009] S1: Add the rare earth compound to be purified into the inorganic compound and dissolve it to obtain a rare earth solution;

[0010] S2: Add an organic complexing agent and an auxiliary regulator to the rare earth solution at a preset first ratio, and adjust the pH of the system to a preset value to obtain a rare earth complexing solution;

[0011] S3: Add a precipitant to the rare earth complexing liquid at a preset second ratio to precipitate, and after solid-liquid separation, washing and drying or calcination, obtain the purified high-purity rare earth compound.

[0012] In another aspect of the present invention, preferably, the concentration of rare earth ions in the rare earth feed solution is 0.01 mol / L to 1.5 mol / L;

[0013] The rare earth compound mentioned in step S1 includes at least one of rare earth oxides, carbonates, nitrates, chlorides, and sulfates;

[0014] The inorganic compound includes at least one of water, hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid.

[0015] In another aspect of the present invention, preferably,

[0016] The organic complexing agent mentioned in step S2 includes at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, iminodiacetic acid, disodium iminodiacetic acid, 4,4'-diaminodiphenyl ether, N-hydroxyethylethylenediaminetriacetic acid, trisodium hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, pentasodium diethylenetriaminepentaacetic acid, 2-hydroxyisobutyric acid, sodium 2-hydroxyisobutyrate, iminodisuccinic acid, and tetrasodium iminodisuccinate.

[0017] The auxiliary regulator includes at least one of an inorganic acid, a first inorganic base, and a soluble inorganic metal salt.

[0018] In another aspect of the present invention, preferably,

[0019] In step S2, the molar ratio of the organic complexing agent to the rare earth ions in the rare earth solution in the preset first ratio is 0.01 to 3:1, preferably 0.1 to 2:1.

[0020] The preset pH value is 0.1 to 5, preferably 0.5 to 3.5.

[0021] In another aspect of the present invention, preferably,

[0022] The inorganic acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid;

[0023] The first inorganic base includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water;

[0024] The soluble inorganic metal salt includes at least one of sodium chloride, sodium nitrate, sodium sulfate, potassium chloride, potassium nitrate, and potassium sulfate.

[0025] In another aspect of the present invention, preferably,

[0026] The precipitant mentioned in step S3 includes at least one of oxalic acid or oxalate, bicarbonate, carbonate, second inorganic base and sulfide.

[0027] The preset second ratio includes a molar ratio of rare earth ions to the precipitant of 1:1.4 to 1:4;

[0028] The precipitation temperature is 10–90℃, and the precipitation time is 10–360 min;

[0029] In another aspect of the present invention, preferably,

[0030] In step S3, after adding a precipitant to the rare earth complex liquid at a preset second ratio for precipitation, aging is also included.

[0031] The aging temperature is 50–98℃, and the aging time is 1–12 hours.

[0032] In another aspect of the present invention, preferably,

[0033] The precipitant includes at least one of oxalic acid, ammonium bicarbonate, sodium bicarbonate, sodium carbonate, magnesium bicarbonate, ammonia, sodium hydroxide, potassium hydroxide, ammonium sulfide, and sodium sulfide.

[0034] The preset second ratio includes a molar ratio of rare earth ions to the precipitant of 1:1.8 to 1:3.5;

[0035] The precipitation temperature is 30–80℃; the precipitation time is 20–240 min.

[0036] The aging temperature is 60–98℃, and the aging time is 2–6 hours.

[0037] In another aspect of the present invention, preferably,

[0038] Step S2 includes:

[0039] A pre-precipitant is added to the rare earth solution, and the pH value of the rare earth solution is adjusted to perform pre-precipitation and solid-liquid separation. Then, an organic complexing agent and an auxiliary regulator are added to the filtrate in a preset first ratio, and the pH of the system is adjusted to a preset value to obtain a rare earth complexing solution.

[0040] The preprecipitant includes at least one of ammonia, sodium hydroxide, potassium hydroxide, ammonium sulfide, potassium sulfide, and sodium sulfide.

[0041] In another aspect of the present invention, preferably, the molar ratio of the amount of preprecipitant added to the impurity ions to be removed is 1 to 4:1, and the pH value of the rare earth solution is adjusted to 3.5 to 5.5 to carry out the preprecipitation reaction.

[0042] In another aspect of the present invention, preferably, the high-purity rare earth compound has an impurity removal rate of more than 85% compared to the rare earth compound to be purified, wherein the impurities removed by the method of preparing the high-purity rare earth compound by complexation precipitation include at least one of calcium, magnesium, aluminum, iron, copper, zinc, cobalt, nickel, manganese, thorium and uranium.

[0043] (III) Beneficial Effects

[0044] The above-described technical solution of the present invention has the following beneficial technical effects:

[0045] This invention controls the occurrence forms of rare earth elements and impurity elements by adding organic complexing agents; the addition of auxiliary regulators further adjusts the distribution of rare earth elements and impurity elements, thereby selectively precipitating rare earth elements and reducing the precipitation of impurity ions, thus improving the separation effect during precipitation. The purification method of this invention has a high rare earth recovery rate and low loss, and the rare earth compounds obtained by precipitation have good crystal form, small particle size and uniform distribution, and less agglomeration, which can effectively reduce the adsorption of impurity elements on the precipitate surface. The purification method of this invention is simple to operate, has a large processing scale, and low production cost. Attached Figure Description

[0046] Figure 1 This is an overall flowchart of one embodiment of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0048] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0049] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0050] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0051] A method for preparing high-purity rare earth compounds by complexation precipitation. Figure 1An overall flowchart of one embodiment of the present invention is shown, as follows: Figure 1 As shown, it includes:

[0052] S1: Add the rare earth compound to be purified into the inorganic compound and dissolve it to obtain a rare earth solution;

[0053] The time and temperature for dissolving the rare earth compound to be purified in the inorganic compound are not limited here. In this embodiment, the concentration of rare earth ions in the rare earth solution is 0.01 mol / L to 1.5 mol / L.

[0054] The specific contents of the rare earth compound to be purified are not limited here. In this embodiment, the rare earth compound includes at least one of rare earth oxides, carbonates, nitrates, chlorides and sulfates.

[0055] The specific content of the inorganic compound is not limited here. In this embodiment, the inorganic compound includes at least one of water, hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.

[0056] S2: Add an organic complexing agent and an auxiliary regulator to the rare earth solution at a preset first ratio, and adjust the pH of the system to a preset value to obtain a rare earth complexing solution;

[0057] The organic complexing agent mentioned in step S2 includes at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, iminodiacetic acid, disodium iminodiacetic acid, 4,4'-diaminodiphenyl ether, N-hydroxyethylethylenediaminetriacetic acid, trisodium hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, pentasodium diethylenetriaminepentaacetic acid, 2-hydroxyisobutyric acid, sodium 2-hydroxyisobutyrate, iminodisuccinic acid, and tetrasodium iminodisuccinate.

[0058] The auxiliary regulator includes at least one of an inorganic acid, a first inorganic base, and a soluble inorganic metal salt.

[0059] The molar ratio of the organic complexing agent to the rare earth ions in the rare earth solution in the preset first ratio is 0.01 to 3:1, preferably 0.1 to 2:1;

[0060] The preset pH value is 0.1 to 5, preferably 0.5 to 3.5.

[0061] The inorganic acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid;

[0062] The first inorganic base includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water;

[0063] The soluble inorganic metal salt includes at least one of sodium chloride, sodium nitrate, sodium sulfate, potassium chloride, potassium nitrate, and potassium sulfate.

[0064] Organic complexing agents have the ability to form stable complexes with metal ions. In the above precipitation process, organic complexing agents are added to form complexes with rare earth elements and other impurity metal ions. The different binding abilities between the organic complexing agent and the metal ions (the rare earth elements to be purified and the impurity elements) result in different stability of these complexes. The molar ratio of the added organic complexing agent to the rare earth ions in the rare earth solution is 0.01 to 3, preferably 0.1 to 2. In this embodiment, the amount of organic complexing agent added is much greater than the amount of impurity ions, in order to allow all impurity ions and some or all of the rare earth ions to form complexes, thereby achieving a deep separation effect.

[0065] The pH of the system was further adjusted to a preset value because changes in pH affect the binding ability between metal ions and the complexing agent, thereby altering the stability of the complex. Under the pH conditions of this embodiment, the complex formed by rare earth elements and the complexing agent became unstable, while the complex formed by impurity elements became more stable. Furthermore, this embodiment, through precise control of the pH value, can further regulate the speciation distribution of rare earth elements and impurity elements in the solution. At the pH value selected in this embodiment, rare earth elements are more likely to undergo precipitation reactions, while impurity elements remain in a dissolved state and are difficult to precipitate with the precipitant. Thus, rare earth elements can effectively reduce the co-precipitation of impurity elements during the precipitation process, thereby achieving effective separation from impurity elements.

[0066] By adjusting the concentration and type of organic complexing agent, the occurrence forms of rare earth elements and impurity elements in the solution can be controlled, so that in the subsequent precipitation step, rare earth elements are preferentially precipitated, while impurity elements remain in the solution.

[0067] In addition to adjusting the pH value of the system, the presence of auxiliary regulators can also help to combine with impurity elements to form complexes, increasing their stability in the solution. Furthermore, the complexes formed with complexing agents can be made more stable, thereby enhancing the separation effect of rare earth elements and impurity ions during the precipitation process.

[0068] S3: Add a precipitant to the rare earth complexing liquid at a preset second ratio to precipitate, and after solid-liquid separation, washing and drying or calcination, obtain the purified high-purity rare earth compound.

[0069] The precipitant mentioned in step S3 includes at least one of oxalic acid or oxalate, bicarbonate, carbonate, second inorganic base and sulfide.

[0070] The preset second ratio includes a molar ratio of rare earth ions to the precipitant of 1:1.4 to 1:4;

[0071] The precipitation temperature is 10–90℃, and the precipitation time is 10–360 min;

[0072] In step S3, after adding a precipitant to the rare earth complex liquid at a preset second ratio for precipitation, aging is also included.

[0073] The aging temperature is 50–98℃, and the aging time is 1–12 hours.

[0074] Furthermore, in this embodiment,

[0075] The precipitant includes at least one of oxalic acid, ammonium bicarbonate, sodium bicarbonate, sodium carbonate, magnesium bicarbonate, ammonia, sodium hydroxide, potassium hydroxide, ammonium sulfide, and sodium sulfide.

[0076] The preset second ratio includes a molar ratio of rare earth ions to the precipitant of 1:1.8 to 1:3.5;

[0077] The precipitation temperature is 30–80℃; the precipitation time is 20–240 min.

[0078] The aging temperature is 60–98℃, and the aging time is 2–6 hours.

[0079] Within the experimental parameters of this embodiment, impurity elements mainly exist in a more stable complex form during precipitation and are not precipitated, remaining in the solution, while rare earth elements are precipitated, thus achieving excellent selective separation and impurity removal. Furthermore, the presence of organic complexing agents, such as disodium ethylenediaminetetraacetate, acts as a surfactant to regulate the interaction between precipitate particles in the solution, controlling the morphology and size of the precipitate particles. It also acts as a retarder or stabilizer (stabilizing the pH of the system) or a dispersant similar to lauric acid during the precipitation process, stabilizing the crystal form, reducing agglomeration, and resulting in small and uniform particle size of the precipitate. This leads to a higher D-value of the obtained high-purity rare earth compound. 50 <2μm. In the precipitation and aging process of this invention, by controlling the temperature and time conditions, the impact of impurity precipitation or adsorption on product purity can be effectively reduced.

[0080] Furthermore, in this embodiment,

[0081] Step S2 includes:

[0082] A pre-precipitant is added to the rare earth solution, and the pH value of the rare earth solution is adjusted to perform pre-precipitation and solid-liquid separation. Then, an organic complexing agent and an auxiliary regulator are added to the filtrate in a preset first ratio, and the pH of the system is adjusted to a preset value to obtain a rare earth complexing solution.

[0083] The role of the pre-precipitant is to selectively precipitate some of the impurity ions in the rare earth solution, while the rare earth and unprecipitated impurity ions remain in the liquid. The pre-precipitant can be the same type as the precipitant or a different type.

[0084] The preprecipitant includes at least one of ammonia, sodium hydroxide, potassium hydroxide, ammonium sulfide, potassium sulfide, and sodium sulfide.

[0085] The molar ratio of the amount of preprecipitant added to the impurity ions to be removed is 1 to 4:1, and the pH of the rare earth solution is adjusted to 3.5 to 5.5 to carry out the preprecipitation reaction.

[0086] Optionally, if the impurity to be removed is Al, at least one of the preprecipitants sodium hydroxide, potassium hydroxide, and ammonia water can be added to the system to adjust the pH to a preset value of 4-5.5. After solid-liquid separation by filtration, the separated liquid is obtained. Under this pH condition, rare earth and other impurity ions exist in the solution in the form of ion complexes, while aluminum reacts with hydroxide ions to form aluminum hydroxide precipitate, thereby achieving the separation effect.

[0087] Optionally, if the impurities to be removed are Fe, Co, Ni, Cu, Zn, etc., at least one of the preprecipitants ammonium sulfide, sodium sulfide, and potassium sulfide can be added to the system. The molar ratio of the amount of preprecipitant added to the sum of the molar amounts of Fe, Co, Ni, Cu, Zn, etc., impurity ions is 1 to 4:1. The pH is adjusted to the preset preprecipitant pH value of 4-5.5. After solid-liquid separation, the separated liquid is obtained. Under these conditions, the above-mentioned impurity ions are in a metastable state and are easily reacted with ammonium sulfide to form sulfide precipitates, while rare earth elements remain in the solution, thereby achieving the separation effect.

[0088] Furthermore, before the feed solution is pre-precipitated, a pre-precipitation complexing agent is added. The pre-precipitation complexing agent coordinates with the rare earth elements to prevent rare earth precipitation. The pre-precipitation complexing agent can be the same type as the above-mentioned organic complexing agent, or it can be different from the above-mentioned organic complexing agent.

[0089] The pre-precipitating complexing agent can be nitrotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, or 2-hydroxyisobutyric acid. The molar ratio of the amount of pre-precipitating complexing agent added to rare earth ions is 0.5:1 to 1.1:1.

[0090] The rare earth compound prepared by the purification method described above has an impurity removal rate of more than 85% and a rare earth recovery rate of more than 98% compared to the rare earth compound to be purified. The impurities removed by the purification method include at least one of calcium, magnesium, aluminum, iron, copper, zinc, cobalt, nickel, manganese, thorium and uranium. Furthermore, the impurities that are more easily removed by the purification method include at least one of calcium, magnesium, zinc, cobalt, nickel, manganese, thorium and uranium.

[0091] This invention controls the occurrence forms of rare earth elements and impurity elements by adding organic complexing agents; the addition of auxiliary regulators further adjusts the morphological distribution of impurity elements, thereby selectively precipitating rare earth elements and reducing impurity precipitation, thus improving the separation effect during precipitation. The purification method of this invention has a high rare earth recovery rate, good precipitate crystal form, small and uniform particles, and less agglomeration, which can effectively reduce the adsorption of impurity elements on the precipitate surface and minimize rare earth loss during precipitation. The purification method of this invention is simple to operate and has low production costs.

[0092] Example 1

[0093] The rare earth compound to be purified was 3N-grade lanthanum oxide, with impurities of calcium, magnesium, aluminum, iron, zinc, and copper in the product at concentrations of 48 ppm, 35 ppm, 6 ppm, 8 ppm, 5 ppm, and 2 ppm, respectively. First, the lanthanum oxide sample was dissolved in hydrochloric acid to obtain a lanthanum chloride solution with a rare earth ion concentration of 20 g / L (based on REO). The organic complexing agent N-hydroxyethylethylenediaminetriacetic acid was added to the lanthanum chloride solution, and the mixture was stirred to dissolve and initiate a complexation reaction. Hydrochloric acid and sodium chloride were added as auxiliary regulators to adjust the system, resulting in a rare earth complex solution. The molar ratio of the added organic complexing agent N-hydroxyethylethylenediaminetriacetic acid to lanthanum was 1.1. After adjustment with the auxiliary regulators, the pH of the rare earth complex solution was 1.2. Oxalic acid was used as a precipitant to directly precipitate the rare earth complex solution. The molar ratio of rare earth to oxalic acid was 1:2.5. The precipitation temperature was 80℃, the aging time was 0.5 h, the precipitation time was 25 min, and the aging temperature was 60℃. After precipitation, the product was filtered, washed, and calcined to obtain purified lanthanum oxide. The impurity content of the purified lanthanum oxide was determined by glow discharge mass spectrometry (GDMS). The impurity contents of calcium, magnesium, aluminum, iron, zinc, and copper in the purified lanthanum oxide product were found to be 5.3 ppm, 3.8 ppm, 0.8 ppm, 0.6 ppm, 1 ppm, and 0.1 ppm, respectively, with removal rates of 88.96%, 89.14%, 86.67%, 92.5%, 80%, and 95%, respectively. The lanthanum oxide recovery rate was 99%.

[0094] Example 2

[0095] The rare earth compound to be purified was 3N5 grade scandium oxide. The impurities in the product were 180 ppm for calcium, 5 ppm for magnesium, 18 ppm for aluminum, 80 ppm for iron, 7.9 ppm for zinc, and 1.6 ppm for copper; and 510 ppm for sodium, 46 ppm for potassium, 52 ppm for thorium, and 13 ppm for uranium. First, the scandium oxide sample was dissolved in nitric acid to obtain a scandium nitrate solution, with a rare earth ion concentration of 20 g / L (based on REO). An organic complexing agent, iminodiacetic acid, was added to the scandium nitrate solution, and the mixture was stirred to dissolve and undergo a complexation reaction. Nitric acid and sulfuric acid were added as auxiliary regulators to adjust the system, resulting in a rare earth complexed solution. The molar ratio of the added complexing agent iminodiacetic acid to scandium was 2.5; the pH after adjustment with auxiliary regulators was 1.1. First, ammonium sulfide was used as a pre-precipitant to selectively precipitate impurities; after solid-liquid separation, oxalic acid was used as a precipitant to selectively precipitate rare earth elements. The molar ratio of rare earth elements to oxalic acid was 1:2.3, the precipitation temperature was 25℃, the aging time was 1h, the precipitation time was 50min, and the aging temperature was 60℃. After precipitation, the scandium oxide product was obtained through filtration, washing, and calcination. The impurity content of the purified scandium oxide was analyzed using glow discharge mass spectrometry (GDMS). The contents of calcium, magnesium, aluminum, iron, zinc, and copper impurities in the purified scandium oxide product were found to be 15 ppm, 0.6 ppm, 2.5 ppm, 1.8 ppm, 0.5 ppm, and 0.2 ppm, respectively, with removal rates of 91.67%, 88%, 86.11%, 97.75%, 93.67%, and 87.5%. The contents of sodium, potassium, thorium, and uranium impurities were 80 ppm, 6.5 ppm, 3.6 ppm, and 0.8 ppm, respectively, with removal rates of 84.31%, 85.87%, 93.08%, and 93.85%. The scandium oxide recovery rate was 98.5%.

[0096] Example 3

[0097] The rare earth compound to be purified was ytterbium oxide of grade 4N. The impurities in the product were: calcium (8 ppm), magnesium (0.5 ppm), aluminum (2 ppm), iron (3 ppm), zinc (1 ppm), and copper (0.9 ppm), respectively; and potassium (5 ppm), cobalt (0.5 ppm), nickel (0.5 ppm), and manganese (0.5 ppm), respectively. First, the ytterbium oxide sample was dissolved in nitric acid to obtain a ytterbium nitrate solution with a rare earth ion concentration of 16 g / L (based on REO). An organic complexing agent, ethylenediaminetetraacetic acid (EDTA), was added to the ytterbium nitrate solution, and the mixture was stirred to dissolve and undergo a complexation reaction. Sodium hydroxide was added as an auxiliary regulator to adjust the system, resulting in a rare earth complex solution. The molar ratio of EDTA to ytterbium was 1.2. After adjustment with the auxiliary regulator, the pH was 5.0. First, ammonium sulfide was used as a pre-precipitant to selectively precipitate impurities. After solid-liquid separation, sodium hydroxide was used as a precipitant to selectively precipitate rare earth elements. The molar ratio of rare earth elements to sodium hydroxide was 1:3.3. The precipitation temperature was 25℃, the aging time was 0.5h, the precipitation time was 35min, and the aging temperature was 60℃. After precipitation, filtration, washing, and calcination yielded ytterbium oxide with low non-rare earth impurity content. The impurity content of the ytterbium oxide prepared by complex precipitation was determined using glow discharge mass spectrometry (GDMS). The purified ytterbium oxide product contained calcium, magnesium, aluminum, iron, zinc, and copper impurities of 1.2 ppm, 0.08 ppm, 0.1 ppm, 0.27 ppm, 0.15 ppm, and 0.09 ppm, respectively, with removal rates of 85%, 84%, 95%, 91%, 85%, and 90%. The contents of potassium, cobalt, nickel, and manganese impurities were 0.39 ppm, <0.05 ppm, <0.05 ppm, and <0.05 ppm, respectively, with removal rates of 92.2%, >90%, >90%, and >90%. The ytterbium oxide recovery rate was 99.3%. The purification parameters and results of Examples 4-39 are shown in Table 1, and the purification parameters and results of Comparative Examples 1-3 are shown in Table 2.

[0098] Table 1. Purification parameters and purification results for Examples 1-36

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108] Note: The above product particle size distribution (D) 90 -D 10 ) / (2D 50 ) < 1

[0109] Table 2 Purification parameters and purification results for Comparative Examples 1-3

[0110]

[0111]

[0112] As can be seen from Tables 1 and 2, the purification method of the present invention has an impurity removal rate of greater than 85%, a particle size D50 of the purified high-purity rare earth compound product that is less than or equal to 2 μm, and a rare earth recovery rate of over 98%, all of which are superior to the rare earth compounds purified by comparative examples 1-3.

[0113] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

[0114] The present invention has been described above with reference to embodiments thereof. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

[0115] Although embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to the embodiments of the present invention without departing from the spirit and scope of the invention.

[0116] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing high-purity rare earth compounds by complexation precipitation, characterized in that, include: S1: Add the rare earth compound to be purified into the inorganic compound and dissolve it to obtain a rare earth solution; S2: Add an organic complexing agent and an auxiliary regulator to the rare earth solution at a preset first ratio, and adjust the pH of the system to a preset value to obtain a rare earth complexing solution; S3: Add a precipitant to the rare earth complexing liquid at a preset second ratio to precipitate, and after solid-liquid separation, washing and drying or calcination, obtain the purified high-purity rare earth compound.

2. The method according to claim 1, characterized in that, The rare earth ion concentration in the rare earth feed solution is 0.01 mol / L to 1.5 mol / L; The rare earth compound mentioned in step S1 includes at least one of rare earth oxides, carbonates, nitrates, chlorides, and sulfates; The inorganic compound includes at least one of water, hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid.

3. The method according to claim 1, characterized in that, The organic complexing agent mentioned in step S2 includes at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, iminodiacetic acid, disodium iminodiacetic acid, 4,4'-diaminodiphenyl ether, N-hydroxyethylethylenediaminetriacetic acid, trisodium hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, pentasodium diethylenetriaminepentaacetic acid, 2-hydroxyisobutyric acid, sodium 2-hydroxyisobutyrate, iminodisuccinic acid, and tetrasodium iminodisuccinate. The auxiliary regulator includes at least one of an inorganic acid, a first inorganic base, and a soluble inorganic metal salt.

4. The method according to claim 1, characterized in that, In step S2, the molar ratio of the organic complexing agent to the rare earth ions in the rare earth solution in the preset first ratio is 0.01 to 3:1, preferably 0.1 to 2:

1. The preset pH value is 0.1 to 5, preferably 0.5 to 3.

5.

5. The method according to claim 3, characterized in that, The inorganic acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; The first inorganic base includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water; The soluble inorganic metal salt includes at least one of sodium chloride, sodium nitrate, sodium sulfate, potassium chloride, potassium nitrate, and potassium sulfate.

6. The method according to claim 1, characterized in that, The precipitant mentioned in step S3 includes at least one of oxalic acid or oxalate, bicarbonate, carbonate, second inorganic base and sulfide. The preset second ratio includes a molar ratio of rare earth ions to the precipitant of 1:1.4 to 1:4; The precipitation temperature is 10–90℃, and the precipitation time is 10–360 min.

7. The method according to claim 1, characterized in that, In step S3, after adding a precipitant to the rare earth complex liquid at a preset second ratio for precipitation, aging is also included. The aging temperature is 50–98℃, and the aging time is 1–12 hours.

8. The method according to claim 6, characterized in that, The precipitant includes at least one of oxalic acid, ammonium bicarbonate, sodium bicarbonate, sodium carbonate, magnesium bicarbonate, ammonia, sodium hydroxide, potassium hydroxide, ammonium sulfide, and sodium sulfide. The preset second ratio includes a molar ratio of rare earth ions to the precipitant of 1:1.8 to 1:3.5; The precipitation temperature is 30–80℃; the precipitation time is 20–240 min. The aging temperature is 60–98℃, and the aging time is 2–6 hours.

9. The method according to claim 1, characterized in that, Step S2 includes: A pre-precipitant is added to the rare earth solution, and the pH value of the rare earth solution is adjusted to perform pre-precipitation and solid-liquid separation. Then, an organic complexing agent and an auxiliary regulator are added to the filtrate in a preset first ratio, and the pH of the system is adjusted to a preset value to obtain a rare earth complexing solution. The preprecipitant includes at least one of ammonia, sodium hydroxide, potassium hydroxide, ammonium sulfide, potassium sulfide, and sodium sulfide.

10. The method according to claim 8, characterized in that, The molar ratio of the amount of preprecipitant added to the impurity ions to be removed is 1 to 4:1, and the pH of the rare earth solution is adjusted to 3.5 to 5.5 to carry out the preprecipitation reaction.

11. The method according to any one of claims 1-10, characterized in that, The high-purity rare earth compound has an impurity removal rate of more than 85% compared to the rare earth compound to be purified, and the impurities removed by the method of preparing high-purity rare earth compound by complex precipitation include at least one of calcium, magnesium, aluminum, iron, copper, zinc, cobalt, nickel, manganese, thorium and uranium.

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