Method for preparing high-purity tantalum pentoxide and niobium pentoxide from niobium-tantalum iron ore

Abstract

The invention relates to the technical field of niobium-tantalum-iron ore purification, in particular to a method for preparing high-purity tantalum pentoxide and niobium pentoxide from niobium-tantalum-iron ore. The method comprises the following steps: firstly, adding ammonium fluoride and ammonium sulfate to help mineral decomposition and reduce the roasting temperature, then treating the niobium-tantalum iron ore by using a sulfuric acid-hydrofluoric acid mixed solution to fully dissolve niobium-tantalum oxides, then extracting and separating niobium and tantalum by using a specific solvent system, and finally adding ammonia water to precipitate and calcine to obtain the niobium-tantalum iron ore. The high-purity niobium pentoxide and tantalum pentoxide are prepared, the product yield is high, the impurity content is low, and the niobium pentoxide and tantalum pentoxide are suitable for being used as raw materials of capacitor-grade tantalum powder and niobium powder.

Description

Technical Field

[0001] The present invention relates to the technical field of niobium-tantalite purification, and in particular to a method for preparing high-purity tantalum pentoxide and niobium pentoxide from niobium-tantalite. Background Art

[0002] The chemical formula of niobium-tantalite can be expressed as (Fe, Mn)(Nb, Ta)2O6, in which niobium and tantalum coexist, generally Nb2O5 accounts for 35-45wt%, Ta2O5 accounts for 3-7wt%, and it also contains 0.2-0.5wt% of antimony. The properties of antimony are similar to those of niobium and tantalum. Conventional wet smelting processes are difficult to remove a small amount of antimony. A small amount of antimony will have a significant adverse effect on the performance of capacitors. In addition, the presence of Fe will also affect the performance of capacitors and needs to be removed as much as possible. In order to remove a small amount of antimony (Sb) in niobium-tantalite, patent CN109097572A discloses a method for removing impurity antimony in tantalum-niobium wet smelting, which is to add a water-soluble chemical chelating agent to an aqueous solution of fluoroniobic acid or fluorotantalic acid containing antimony impurity metal ions and mix them thoroughly; then, ammonia is passed through the mixed solution obtained in step (1) to neutralize it, producing niobium hydroxide or tantalum hydroxide precipitate, and the precipitate is filtered and washed with pure warm water to remove the antimony impurity metal ions coexisting therein. The complexing agent is one of 2,3-dimercaptopropanesulfonic acid, 2,3-dimercaptosuccinic acid (DMSA), or a mixture of the two. Although this patented technology can basically remove antimony, the yield of niobium / tantalum will decrease. Patent CN102358918A discloses a method for removing antimony from ultra-high-purity tantalum pentoxide and niobium pentoxide, which is achieved by adding D-296 macroporous anion exchange resin to remove antimony from the extraction system. It requires a large amount of solvent, the resin adsorption capacity is limited, and the macroporous anion exchange resin is difficult to recycle after use, and does not have an industrial production prospect.

[0003] In existing technology, niobium-tantalite is primarily used to produce high-purity niobium pentoxide, while the lower-content tantalum is discarded, resulting in a waste of resources. Examples include those described in CN117185350A, CN110563038A, CN108640153A, and CN103408070A. Tantalum is much more expensive than niobium, and tantalum capacitors offer superior performance compared to niobium capacitors in high-end applications such as military and aerospace. Patents CN114540630A, CN118854085A, CN117127030A, and CN115703644A, respectively, report separation of tantalum from niobium and tantalum using a reverse niobium extraction / strip extraction process from raw materials such as ore powder, waste acid, and wastewater containing both niobium and tantalum. However, the use of methyl isobutyl ketone (MIBK) as the extraction agent generally results in low niobium / tantalum separation efficiency, making it difficult to achieve a balanced yield and purity of both niobium and tantalum. If high-purity tantalum pentoxide can be efficiently extracted and prepared from niobium-tantalite ore, and subsequently reduced to prepare capacitor-grade high-purity tantalum powder, it will have important significance and commercial value. Summary of the Invention

[0004] In order to solve the problem in the prior art that it is difficult to directly use niobium-tantalite to prepare niobium-tantalum capacitors with excellent performance, the present invention provides a method for preparing high-purity tantalum pentoxide and niobium pentoxide from niobium-tantalite.

[0005] The present invention first adds ammonium fluoride and ammonium sulfate to help decompose the mineral and lower the roasting temperature. The niobium-tantalite is then treated with a sulfuric acid-hydrofluoric acid mixture to fully dissolve the niobium-tantalum oxides. Niobium and tantalum are then extracted using a specific solvent system to separate them. Finally, high-purity niobium pentoxide and tantalum pentoxide are produced by adding ammonia for precipitation and calcination. Specifically, the present invention solves the above-mentioned technical problems through the following technical solutions.

[0006] A method for preparing high-purity tantalum pentoxide and niobium pentoxide from niobium-tantalite comprises the following steps:

[0007] (S1) crushing niobium-tantalite, adding ammonium fluoride and ammonium persulfate, ball-milling, and then heating and calcining to obtain a calcined product;

[0008] (S2) dissolving and leaching the calcined product with a mixed acid of hydrofluoric acid and sulfuric acid under high temperature and high pressure conditions under an inert atmosphere to obtain a leachate;

[0009] (S3) subjecting the leachate to multi-stage extraction with a first extractant to obtain a first organic phase and a first aqueous phase, wherein the first extractant comprises methyl isobutyl ketone, an alcoholamine compound, a nitrogen-containing heterocyclic thiol compound, a trialkylphosphine oxide, and a C6-C10 alcohol; subjecting the first organic phase to multi-stage stripping with 3-5 mol / L sulfuric acid as a first stripping agent to obtain a tantalum-rich aqueous solution;

[0010] (S4) adding hydrofluoric acid to the first aqueous phase to adjust the hydrofluoric acid concentration to 5-7 mol / L, performing multi-stage extraction with a second extractant to obtain a second organic phase and a second aqueous phase, wherein the second extractant includes methyl isobutyl ketone, an amine compound, a fluorinated sulfonyl ionic liquid, a phosphate ester, and a C6-C10 alcohol; and performing multi-stage stripping of the second organic phase with 0.2-0.5 mol / L sulfuric acid as a second stripping agent to obtain a niobium-rich aqueous solution;

[0011] (S5) The tantalum-rich aqueous solution and the niobium-rich aqueous solution are precipitated with ammonia water, respectively. The precipitates are washed, dried, and calcined to obtain niobium pentoxide and tantalum pentoxide as products, respectively.

[0012] Furthermore, in step (S1), the niobium content of the columbite-tantalite is 35-50% by weight as niobium pentoxide, and the tantalum content is 3-7% by weight as tantalum pentoxide. The mass ratio of the columbite-tantalite, ammonium fluoride, and ammonium persulfate is 100:3-5:2-3. Adding ammonium fluoride and ammonium persulfate during the columbite-tantalite roasting process aids mineral decomposition, lowers the roasting temperature, and increases the subsequent acid leaching yield, thereby improving the yield of niobium and tantalum. The inventor's previous patent used ammonium fluoride and ammonium sulfate as roasting aids. Experimental results indicate that using ammonium persulfate instead of ammonium sulfate yields better results.

[0013] Furthermore, in step (S1), the ball milling conditions are a ball-to-material ratio of 15-30:1, a rotation speed of 200-400 rpm, and a ball milling time of 0.5-1 hour. Ball milling makes the materials more evenly mixed, which is more conducive to the effect of the roasting aid and improves the leaching rate. The temperature is raised to 750-900°C and maintained for 4-10 hours, with a heating rate of 1-20°C / min, preferably 5-10°C / min.

[0014] Furthermore, in step (S2), the inert atmosphere is at least one of nitrogen and argon; the molar ratio of hydrofluoric acid to sulfuric acid in the mixed acid is 1:5-8, and the concentration of hydrofluoric acid is 1-2 mol / L, preferably 1-1.5 mol / L; the solid-liquid ratio of the calcined product to the mixed acid is 1 kg:4-6 L; and the high temperature and high pressure are 160-220°C and 1.5-3 MPa. Increasing the pressure facilitates the leaching of tantalum and niobium. Increasing the pressure promotes relative movement between the solid and liquid phases during the leaching process. High pressure is achieved by filling the autoclave with an inert gas.

[0015] Furthermore, in step (S3), the volume ratio of the leachate to the first extractant is 1:1-1.5, and the multi-stage extraction is 10-15 levels; the volume ratio of the first organic phase to the stripping agent is 1:1-1.5, and the multi-stage stripping is 5-10 levels.

[0016] Furthermore, in step (S3), the alcoholamine compound is selected from at least one of tributanolamine and trihexanolamine; the nitrogen-containing heterocyclic thione compound is selected from at least one of 2-indolinethione, pyridine-4(1H)-thione, pyrimidine-4(3H)-thione, thiazole-2(3H)-thione, tetrahydropyrrole-2-thione, 4-methylthiazole-2-thione, 3-methyl-2-thiazolidinethione, and 3-methyl-2(1H)-pyridinethione; the trialkylphosphine oxide is selected from at least one of tri-n-octylphosphine oxide, tri-n-hexylphosphine oxide, and Cyanex 923; and the C6-10 alcohol is selected from at least one of n-octanol, n-hexanol, n-decanol, and isodecyl alcohol.

[0017] Tantalum's fluorine complexes are more likely to enter the organic phase with organic complexes at low hydrofluoric acid concentrations. Therefore, from a cost-saving perspective, it is more economical to extract and strip tantalum first (in the process flow, operating under low acidity conditions first and then increasing the acidity is easier to implement and less expensive than first increasing the acidity and then reducing it). However, when separating niobium and tantalum in the existing technology, niobium is generally extracted and stripped first. This is because the niobium content in the leachate of niobium-tantalite is relatively high, generally more than 6 times that of tantalum. Extracting tantalum first will cause niobium loss. CN114540630A first extracts and strips tantalum at a low HF concentration, then increases the HF concentration to extract and strip niobium. However, this patent uses the conventional extractant MIBK, and the niobium-tantalum separation coefficient is not high, making it difficult to obtain high-purity niobium and tantalum oxide products, and the loss is relatively serious. The present invention utilizes a specific first extractant, which adds auxiliary extractants, co-extractants, and stabilizers to the conventional extractant MIBK. This significantly improves the niobium / tantalum separation coefficient, enabling tantalum extraction and stripping to be performed first at low HF concentrations, followed by niobium extraction and stripping at high HF concentrations. The inventors have discovered that optimal niobium / tantalum separation can only be achieved when a nitrogen-containing heterocyclic thione is used as the first extractant. For example, 1,3-disulfuric acid-2-thione cannot achieve this effect. This may be because, at low HF concentrations, tantalum typically forms [TaF7] 2- Fluorine-complexed anions require more coordination sites to form stable complexes. Nitrogen-containing heterocyclic thioketones can coordinate simultaneously with both the nitrogen and sulfur atoms, and this chelation effect results in higher selectivity for tantalum. Niobium 1,3-disulfate-2-thione also binds strongly, resulting in decreased selectivity.

[0018] Furthermore, the first extractant is a mixture of methyl isobutyl ketone, alcoholamine compounds, nitrogen-containing heterocyclic thiol compounds, trialkylphosphine oxides, and C6-C10 alcohols in a mass ratio of 40-60:10-15:7-10:4-6:2-3.

[0019] Furthermore, in step (S4), the volume ratio of the first aqueous phase to the second extractant is 1:1-1.5, and the multi-stage extraction is 10-15 stages; the volume ratio of the first organic phase to the stripping agent is 1:1-1.5, and the stripping stages are 5-10 stages. Preferably, in the second extractant, the amine compound is selected from at least one of trioctylamine and trihexylamine; the phosphate ester is selected from at least one of tributyl phosphate, tripentyl phosphate, trihexyl phosphate, and di(2-ethylhexyl)phosphate; the C6-C10 alcohol is selected from at least one of n-octanol, n-hexanol, n-decanol, and isodecanol; and the fluorine-free sulfonyl ionic liquid is selected from at least one of the following structural formulas:

[0020]

[0021] Furthermore, the second extractant is a mixed solvent of methyl isobutyl ketone, amine compounds, fluorine-free sulfonyl ionic liquid, tributyl phosphate, di(2-ethylhexyl) phosphate, and isodecyl alcohol in a mass ratio of 60-80:8-15:5-8:5-8:2-5:2-3.

[0022] Furthermore, in step (S5), ammonia precipitation is performed by adding ammonia to adjust the pH to 10-11, and washing is performed by alternating washing with anhydrous ethanol and deionized water for 3-5 times; calcination is performed at 850-1000° C. for 5-10 hours in an oxygen-containing atmosphere to obtain the product.

[0023] The preparation method of the present invention utilizes existing equipment and, by adding ammonium fluoride and ammonium persulfate, reduces the roasting temperature, reduces the amount of hydrofluoric acid used in subsequent leaching, improves the leaching rate, and improves the yield of tantalum and niobium. Through two extractions and back extractions, tantalum and niobium are extracted respectively using two different extractants, thereby achieving efficient separation of tantalum and niobium. The final products, tantalum pentoxide and niobium pentoxide, have high purity and high yield, are suitable for use as capacitor-grade tantalum powder and niobium powder, and have extremely high economic value. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is further described below in conjunction with specific embodiments. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0025] The elemental analysis results of the niobium-tantalite used in the examples of the present invention are shown in Table 1 below:

[0026] Table 1 Elemental analysis results of niobium-tantalite

[0027] Element <![CDATA[Nb2O5]]> <![CDATA[Ta2O5]]> <![CDATA[Fe2O3]]> <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[MnO2]]> <![CDATA[Sb2O3 <!-- 3 -->]]> Content (wt%) 6.22 46.75 22.71 16.38 2.76 3.64 0.76

[0028] Example 1

[0029] (S1) crushing 100 kg of niobium-tantalite, adding 5 kg of ammonium fluoride and 2 kg of ammonium persulfate, adding the mixture into a ball mill, ball milling for 1 h at a ball-to-material ratio of 20:1 and a rotation speed of 300 rpm, and then heating to 850 °C at a heating rate of 5 °C / min and calcining for 8 h to obtain a calcined product;

[0030] (S2) transferring the calcined product into a high-pressure reactor, adding a mixed acid, wherein the mixed acid is a mixed acid of 1 mol / L hydrofluoric acid and 6 mol / L sulfuric acid, and the mass volume ratio of the calcined product to the mixed acid is 1 kg:5 L; charging nitrogen to make the system pressure 1.5 MPa, and dissolving and leaching the calcined product with the mixed acid of hydrofluoric acid and sulfuric acid under high temperature and high pressure conditions of 200° C. and 1.5 MPa to obtain a leachate.

[0031] The niobium-tantalite ore was leached under different conditions and the total leaching rate of niobium and tantalum was tested. The results are shown in Table 2 below.

[0032] Table 2 Effect of leaching conditions on leaching rate

[0033]

[0034] Based on the data in Table 2, the optimal leaching conditions were determined to be 200°C, 1.5 MPa, and a high-temperature, high-pressure condition. Increasing the temperature and pressure facilitates leaching, but further increasing the temperature and pressure at 200°C and 1.5 MPa does not significantly improve the leaching rate. Furthermore, adding a certain amount of ammonium fluoride and ammonium persulfate to the columbite-tantalite can also increase the leaching rate. Subsequent examples all used the leaching conditions of No. 1 for dissolution leaching of columbite-tantalite.

[0035] (S3) The leachate (obtained by number 1 in Table 2) is subjected to multi-stage extraction with a first extractant to obtain a first organic phase and a first aqueous phase, the volume ratio of the leachate to the first extractant is 1:1, the number of extraction stages is 10, and the first extractant is a mixture of methyl isobutyl ketone, trihexanolamine, tetrahydropyrrole-2-thione, Cyanex 923, and isodecyl alcohol in a mass ratio of 50:10:8:5:2; the first organic phase is subjected to multi-stage stripping with 3 mol / L sulfuric acid as a first stripping agent, the volume ratio of the first organic phase to the first stripping agent is 1:1, the number of stripping stages is 5, and after stripping, a tantalum-rich aqueous solution is obtained;

[0036] (S4) adding hydrofluoric acid to the first aqueous phase to adjust the hydrofluoric acid concentration to 6 mol / L, performing multi-stage extraction with a second extractant, wherein the volume ratio of the first aqueous phase to the second extractant is 1:1, and the number of extraction stages is 10, to obtain a second organic phase and a second aqueous phase, wherein the second extractant is a mixture of methyl isobutyl ketone, trioctylamine, [HSO3-pPy]HSO4, tributyl phosphate, di(2-ethylhexyl) phosphate, and isodecyl alcohol in a mass ratio of 65:12:5:8:2:2; and performing multi-stage stripping of the second organic phase with 0.2-0.5 mol / L sulfuric acid as a second stripping agent, wherein the volume ratio of the second organic phase to the second stripping agent is 1:1, and the number of stripping stages is 5, to obtain a niobium-rich aqueous solution;

[0037] (S5) The tantalum-rich aqueous solution and the niobium-rich aqueous solution are respectively adjusted to pH 10 with aqueous ammonia, precipitated, and the precipitates are alternately washed three times with anhydrous ethanol and deionized water, dried to constant weight, and calcined at 900° C. for 8 h in an air atmosphere to obtain niobium pentoxide and tantalum pentoxide, respectively.

[0038] Example 2

[0039] Other conditions were the same as those in Example 1, except that in step (S3), Cyanex 923 was replaced by an equal volume of tri-n-hexylphosphine oxide.

[0040] Example 3

[0041] Other conditions are the same as those in Example 1, except that in step (S3), the first extractant is a mixture of methyl isobutyl ketone, trihexanolamine, tetrahydropyrrol-2-thione, Cyanex 923, and isodecyl alcohol in a mass ratio of 40:10:10:6:2; and the second extractant is a mixture of methyl isobutyl ketone, trihexylamine, [HSO3-pHIM]HSO4, tributyl phosphate, di(2-ethylhexyl) phosphate, and isodecyl alcohol in a mass ratio of 60:8:8:5:5:3.

[0042] Example 4

[0043] The other conditions are the same as those in Example 1, except that in step (S3), the first extractant is a mixture of methyl isobutyl ketone, tributanolamine, 2-indolinethione, Cyanex 923, and isodecyl alcohol in a mass ratio of 60:15:7:5:3; the second extractant is a mixture of methyl isobutyl ketone, trioctylamine, [HSO3-pPy]HSO4, tributyl phosphate, di(2-ethylhexyl) phosphate, and isodecyl alcohol in a mass ratio of 80:15:8:5:3:3.

[0044] Comparative Example 1

[0045] Other conditions were the same as those in Example 1, except that tetrahydropyrrole-2-thione was replaced with 1,3-disulfuric acid-2-thione of equal mass.

[0046] Comparative Example 2

[0047] Other conditions were the same as those in Example 1, except that the first extractant was a mixture of methyl isobutyl ketone, trihexanolamine, Cyanex 923, and isodecyl alcohol in a mass ratio of 50:10:5:2, i.e., tetrahydropyrrolidine-2-thione was not added.

[0048] Comparative Example 3

[0049] Other conditions are the same as those in Example 1, except that both the first extractant and the second extractant are methyl isobutyl ketone (MIBK).

[0050] The final products of tantalum pentoxide and niobium pentoxide obtained in the above examples and comparative examples were tested for impurity content using an inductively coupled plasma optical emission spectrometer. The results are shown in Table 3 below.

[0051] Table 3 Product purity yield test

[0052]

[0053] The results in Table 3 demonstrate that the preparation method of the present invention, using columbite-tantalite as the raw material, produces capacitor-grade tantalum pentoxide and niobium pentoxide products with high yield and high purity. By adding ammonium fluoride and ammonium sulfate as roasting aids and using specific first and second extractants, product loss is reduced and impurity content is lowered.

Claims

1. A method for preparing high-purity tantalum pentoxide and niobium pentoxide from niobium-tantalite, characterized in that: The following steps are involved: (S1) crushing niobium-tantalite, adding ammonium fluoride and ammonium persulfate, ball-milling, and then heating and calcining to obtain a calcined product; (S2) dissolving and leaching the calcined product with a mixed acid of hydrofluoric acid and sulfuric acid under high temperature and high pressure conditions under an inert atmosphere to obtain a leachate; (S3) the leachate is subjected to multi-stage extraction with a first extractant to obtain a first organic phase and a first aqueous phase, wherein the first extractant includes methyl isobutyl ketone, an alcohol amine compound, a nitrogen-containing heterocyclic thioketone compound, a trialkylphosphine oxide, and a C6-C10 alcohol; the first organic phase is subjected to multi-stage stripping with 3-5 mol / L sulfuric acid as a first stripping agent to obtain a tantalum-rich aqueous solution; (S4) hydrofluoric acid is added to the first aqueous phase to adjust the hydrofluoric acid concentration to 5-7 mol / L, and multi-stage extraction is performed with a second extractant to obtain a second organic phase and a second aqueous phase, wherein the second extractant includes methyl isobutyl ketone, an amine compound, a fluorine-free sulfonyl ionic liquid, a phosphate ester, and a C6-C10 alcohol; the second organic phase is subjected to multi-stage stripping with 0.2-0.5 mol / L sulfuric acid as a second stripping agent to obtain a niobium-rich aqueous solution; (S5) The tantalum-rich aqueous solution and the niobium-rich aqueous solution are precipitated with ammonia water, respectively. The precipitates are washed, dried, and calcined to obtain niobium pentoxide and tantalum pentoxide as products, respectively.

2. The method according to claim 1, characterized in that In step (S1), the niobium content in the niobium-tantalite is 35-50 wt% calculated as niobium pentoxide, and the tantalum content is 3-7 wt% calculated as tantalum pentoxide; the mass ratio of the niobium-tantalite, ammonium fluoride, and ammonium persulfate is 100:3-5:2-3.

3. The method according to claim 1, characterized in that In step (S2), the inert atmosphere is at least one of nitrogen and argon; in the mixed acid, the molar ratio of hydrofluoric acid to sulfuric acid is 1:5-8, and the concentration of hydrofluoric acid is 1-2 mol / L, preferably 1-1.5 mol / L.

4. The method according to claim 1, wherein In step (S2), the solid-liquid ratio of the calcined product and the mixed acid is 1kg:4-6L; the high temperature and high pressure are 160-220°C and 1.5-3MPa.

5. The method according to claim 1, wherein In step (S3), the volume ratio of the leachate to the first extractant is 1:1-1.5, and the multi-stage extraction is 10-15 stages; the volume ratio of the first organic phase to the stripping agent is 1:1-1.5, and the stripping stages are 5-10 stages.

6. The method according to claim 1, characterized in that In step (S3), the alcoholamine compound is selected from at least one of tributanolamine and trihexanolamine; the nitrogen-containing heterocyclic thione compound is selected from at least one of 2-indolinethione, pyridine-4(1H)-thione, pyrimidine-4(3H)-thione, thiazole-2(3H)-thione, tetrahydropyrrole-2-thione, 4-methylthiazole-2-thione, 3-methyl-2-thiazolidinethione, and 3-methyl-2(1H)-pyridinethione; the trialkylphosphine oxide is selected from at least one of tri-n-octylphosphine oxide, tri-n-hexylphosphine oxide, and Cyanex 923; and the C6-10 alcohol is selected from at least one of n-octanol, n-hexanol, n-decanol, and isodecyl alcohol.

7. The method according to claim 1, characterized in that The first extractant is a mixture of methyl isobutyl ketone, alcoholamine compounds, nitrogen-containing heterocyclic thiol compounds, trialkylphosphine oxides, and C6-C10 alcohols in a mass ratio of 40-60:10-15:7-10:4-6:2-3.

8. The method according to claim 1, characterized in that In step (S4), the volume ratio of the first aqueous phase to the second extractant is 1:1-1.5, and the multi-stage extraction is 10-15 stages; the volume ratio of the first organic phase to the stripping agent is 1:1-1.5, and the stripping stages are 5-10 stages. Preferably, in the second extractant, the amine compound is selected from at least one of trioctylamine and trihexylamine; the phosphate ester is selected from at least one of tributyl phosphate, tripentyl phosphate, trihexyl phosphate, and di(2-ethylhexyl)phosphate; the C6-C10 alcohol is selected from at least one of n-octanol, n-hexanol, n-decanol, and isodecanol; and the fluorine-free sulfonyl ionic liquid is selected from at least one of the following structural formulas:

9. The method according to claim 1, characterized in that The second extractant is a mixed solvent of methyl isobutyl ketone, amine compounds, fluorine-free sulfonyl ionic liquid, tributyl phosphate, di(2-ethylhexyl) phosphate, and isodecanol in a mass ratio of 60-80:8-15:5-8:5-8:2-5:2-3.

10. The method according to claim 1, characterized in that In step (S5), ammonia precipitation is performed by adding ammonia to adjust the pH to 10-11, and washing is performed by alternating washing with anhydrous ethanol and deionized water for 3-5 times; calcination is performed at 850-1000° C. for 5-10 hours in an oxygen-containing atmosphere to obtain the product.

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