A method for producing lubricating products using tungsten and molybdenum resources

Abstract

The invention discloses a method for producing lubricating products by utilizing tungsten and molybdenum resources, and relates to the technical field of utilization of tungsten and molybdenum resources, and comprises the following steps: adjusting the mass ratio of Mo and WO3 in tungsten and molybdenum resources to 10:2‑8, crushing, roasting, and obtaining roasting material; adding ammonia water to the roasting material for slurry adjustment, and oxygen pressure ammonia leaching; adding sulfuric acid to the leaching solution for acid precipitation to obtain a precipitate; introducing hydrogen sulfide gas to sulfide the precipitate to obtain a thioammonium salt; adding hydrochloric acid to the thioammonium salt for acidification reaction to obtain a trisulfide; calcining the trisulfide under a protective atmosphere; and crushing the calcined material to obtain. The invention utilizes a large amount of tungsten-molybdenum paragenetic ore or waste catalyst containing tungsten and molybdenum in nature, and obtains a mixture of tungsten disulfide and molybdenum disulfide through a hydrometallurgical process, which can be used as a solid lubricating material, effectively reducing the production cost of solid lubricating materials and improving the recovery of tungsten in ores, and reducing environmental pollution.

Description

Technical Field

[0001] The invention relates to the technical field of tungsten and molybdenum resource utilization, and in particular to a method for producing lubricating products by utilizing tungsten and molybdenum resources. Background Art

[0002] As rare metals, tungsten and molybdenum are widely used in steel, aerospace, electronics and other fields. Molybdenum and tungsten belong to the same group of elements in Group VIB, with similar physical and chemical properties. They are easily associated in nature and often form tungsten-molybdenum paragenetic ores. Due to the paragenetic characteristics of tungsten-molybdenum ores, the separation process faces many challenges. In particular, with the development and utilization of high-quality tungsten-molybdenum resources, the composition of existing tungsten-molybdenum resources has become increasingly complex, and there are more and more tungsten-molybdenum paragenetic ores, such as molybdenite associated with scheelite in nature. Therefore, the recovery of molybdenum or tungsten in low-grade tungsten-molybdenum resources has received more and more attention.

[0003] It is difficult to achieve efficient separation and enrichment of tungsten and molybdenum resources during the beneficiation process. The separation process often faces technical difficulties such as uneven ore particle size and low mineral leaching rate. At the same time, the selectivity and efficiency of traditional separation methods such as flotation and gravity separation are also limited when treating paragenetic ores, increasing the separation cost and environmental burden. For example, for molybdenite-black / scheelite paragenetic ores, the beneficiation products are more common as high-tungsten-molybdenum concentrate (WO3>2.0%) and high-molybdenum-tungsten concentrate (Mo>2.0%). However, tungsten-molybdenum paragenetic mixed concentrates (including high-tungsten-molybdenum concentrates, high-molybdenum-tungsten concentrates, and tungsten-molybdenum co-enriched concentrates) also face the problem of difficult separation of molybdenum and tungsten and high resource loss in the metallurgical stage. The molybdenum metallurgical processes (such as the "oxidative roasting-pickling-ammonia leaching-purification-crystallization" route) and tungsten metallurgical processes (such as the "alkali pressure cooking-purification-extraction-crystallization" route) used in industry are all aimed at the separation and extraction of single elements of molybdenum or tungsten, and a large amount of secondary valuable metals are lost in waste liquid or waste slag. In addition, in the process of purifying and removing the secondary metals molybdenum or tungsten, the main metal will also be partially lost to the purification slag, and hazardous waste will be formed at the same time, such as the molybdenum removal slag produced during the purification of sodium tungstate solution.

[0004] Therefore, when developing tungsten-molybdenum co-existing mineral resources, based on the specific market segmentation strategy and from the perspective of energy conservation and environmental protection, the complex and costly tungsten-molybdenum separation process should be avoided. Instead, tungsten and molybdenum are not strictly separated, and tungsten-molybdenum mixed materials are produced to meet the needs of different industries or customers. This strategy has become a key direction for research and technological progress. In addition, metal catalysts used in the chemical industry often contain tungsten and molybdenum at the same time. For example, waste hydrogenation catalysts produced in petrochemical plants are often accompanied by waste catalysts mixed with molybdenum and tungsten (7.0-9.0% molybdenum and 15-19% tungsten oxide). If the existing single tungsten-molybdenum separation process is used for extraction and separation, there will also be problems such as waste of resources and high recycling costs. Summary of the invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a method for producing lubricating products using tungsten and molybdenum resources. The prepared mixture of tungsten disulfide and molybdenum disulfide can be used as a solid lubricating material and is widely used in aerospace, materials, machinery, petrochemical and other fields, effectively reducing the production cost of solid lubricating materials and improving the recovery of tungsten in ores, thereby reducing environmental pollution.

[0006] The present invention proposes a method for producing lubricating products using tungsten and molybdenum resources, comprising the following steps:

[0007] 1) Oxidation roasting: convert the mass of W element into WO3, adjust the mass ratio of Mo and WO3 in tungsten and molybdenum resources to 10:2-8, crush and roast to obtain roasting material;

[0008] 2) Oxygen-pressure ammonia leaching: Add ammonia water to the roasted material to prepare the slurry, carry out oxygen-pressure ammonia leaching in a pressure autoclave, and filter to obtain the leaching liquid and leaching residue;

[0009] 3) Acid precipitation: add sulfuric acid to the leaching solution to adjust the pH of the system for acid precipitation, filter and separate to obtain the precipitate;

[0010] 4) Sulfidation: introducing hydrogen sulfide gas to carry out sulfidation treatment on the precipitate to obtain thioammonium salt containing ammonium tetrathiomolybdate and ammonium tetrathiotungstate;

[0011] 5) Acidification: Add hydrochloric acid to the thioammonium salt for acidification reaction, filter and separate to obtain trisulfide;

[0012] 6) Calcination: calcining the trisulfide under a protective atmosphere;

[0013] 7) Crushing: crush the calcined material to obtain.

[0014] Preferably, in step 1), ball milling is used to crush the product to a size of ≥200 mesh;

[0015] Preferably, in step 1), the calcination temperature is 500-650° C. and the calcination time is 3.5-4.5 h.

[0016] Preferably, in step 2), the concentration of aqueous ammonia is 20-25%, and the liquid-to-solid ratio is 1-5:1.

[0017] Preferably, in step 2), the process conditions of oxygen-pressure ammonia leaching are as follows: oxygen partial pressure is 15-20 MPa, pH is 10.5-12.0, temperature is 170-200° C., and leaching time is 60-120 min.

[0018] Preferably, in step 3), 30-40% sulfuric acid is added to adjust the pH to 1-2 for acid precipitation, and the acid precipitation temperature is 45-55°C.

[0019] Preferably, in step 4), the vulcanization temperature is 20-30° C. and the vulcanization time is 1-2 h.

[0020] Preferably, in step 5), hydrochloric acid is added for acidification reaction, the end point pH of the reaction is controlled to be 1.0-1.5, the acidification reaction temperature is 60-80° C., and the reaction time is 1-2 h.

[0021] Preferably, in step 6), the calcination temperature is 980-1020° C. and the calcination time is 40-60 min.

[0022] Preferably, the tungsten-molybdenum resources include tungsten-molybdenum paragenetic ores and waste catalysts containing tungsten and molybdenum.

[0023] In the present invention, the effects of the above steps and the chemical reactions involved mainly include:

[0024] In the oxidation roasting process, the volatile components in the tungsten-molybdenum mixed raw materials are removed by roasting and the characteristic factors (most of which exist in nature or secondary waste in a low-valent state) are oxidized; the main chemical reactions involved include:

[0025] 2MoS2+7O2→2MoO3+4SO2↑

[0026] In the oxygen-pressure ammonia leaching process, tungsten and molybdenum are fully oxidized and react with ammonia water to generate corresponding soluble ammonium salts such as ammonium tungstate and ammonium molybdate, which enter the liquid phase and are filtered and separated to obtain a tungsten-molybdenum mixed solution; the main chemical reactions involved include:

[0027] MoO3+2NH3·H2O→ (NH4)2MoO4 + H2O

[0028] WO3+2NH3·H2O→ (NH4)2WO4 + H2O

[0029] In the acid precipitation process, a mixed precipitate rich in ammonium tungstate and ammonium molybdate is obtained by sulfuric acid precipitation; under stirring conditions, dilute sulfuric acid is slowly added to the reactor, and a white flocculent precipitate appears, which is a mixed precipitate of ammonium tungstate and ammonium molybdate.

[0030] In the sulfidation process, hydrogen sulfide gas is introduced to convert ammonium tungstate and ammonium molybdate into ammonium tetrathiotungstate and ammonium tetrathiomolybdate; the main chemical reactions involved include:

[0031] (NH4)2MoO4 +H2S→(NH4)2MoS4+4H2O

[0032] (NH4)2WO4 +H2S→(NH4)2WS4+4H2O

[0033] In the acidification process, hydrochloric acid is used to convert tungsten and molybdenum into trisulfide; the main chemical reactions involved include:

[0034] (NH4)2MoS4+2HCl→MoS3+2NH4Cl+H2S

[0035] (NH4)2WS4+2HCl→WS3+2NH4Cl+H2S

[0036] During the calcination process, trisulfide is converted into disulfide under a protective atmosphere; the main chemical reactions involved include:

[0037] MoS3→MoS2+S WS3→WS2+S .

[0038] Both tungsten disulfide and molybdenum disulfide have good lubrication properties and can be used as solid lubricants in multiple scenarios. Among them, molybdenum disulfide can be extracted from high-molybdenum ores, while tungsten disulfide is obtained through chemical synthesis. However, with the development and utilization of high-quality tungsten and molybdenum resources, the composition of existing tungsten and molybdenum resources has become increasingly complex, there are more and more tungsten-molybdenum symbiotic ores, and the grade of ore resources has decreased, making it difficult to extract natural single molybdenum disulfide resources from ores. It often needs to rely on imports and has high costs; tungsten disulfide is synthesized by sulfiding tungsten, and the synthesis cost is relatively high. Therefore, the comprehensive development and utilization of low-grade tungsten-molybdenum symbiotic resources to prepare lubricating materials is of great significance and industry value.

[0039] The present invention utilizes a large number of tungsten-molybdenum paragenetic ores in nature, such as molybdenite associated with scheelite in nature. Since the physical and chemical properties of molybdenum and tungsten are very similar, the current scheelite beneficiation technology cannot achieve complete and efficient separation and recovery of tungsten and molybdenum, and even if it is achieved, it will lead to excessively high production costs and negative environmental impacts. Therefore, the present invention utilizes the physical and chemical properties of paragenetic ores or tungsten-molybdenum mixed waste to develop an excellent solid lubricant with efficient and comprehensive utilization. The present invention combines oxidative roasting with oxygen ammonia leaching to improve the leaching rate of tungsten and molybdenum, and then obtains a mixture of tungsten disulfide and molybdenum disulfide through hydrometallurgical processes such as acid precipitation and sulfidation. As a lubricating material, it is superior to a single molybdenum disulfide or tungsten disulfide, and the friction coefficient is only 0.04-0.095; the composite lubricating material prepared by the present invention can be widely used in aerospace, materials, machinery, petrochemical and other fields as a solid lubricating material, effectively reducing the production cost of solid lubricating materials and improving the recovery of tungsten in ores, and reducing environmental pollution. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is described in detail below through specific embodiments. Example 1

[0041] 1) Oxidation roasting: Take 200g of tungsten-molybdenum paragenetic ore (its main element content is: Mo 7.21%, W 6.25% in terms of WO3, Si 45%, Fe 10%, Ca 9.0%, Mg 5.5%), ball-mill the tungsten-molybdenum paragenetic ore to ≥200 mesh, add 72g of MoO3 (48g in terms of Mo), control the mass ratio of Mo to WO3 to 10:2, and mix the materials; then transfer them to a rotary kiln for roasting at a temperature of 500°C, a roasting time of 4.5h, and a rotary kiln speed of 3min / rev to obtain a roasted material;

[0042] 2) Oxygen-pressure ammonia leaching: add 15% ammonia water to the roasted material to adjust the slurry, control the liquid-solid ratio to 1.5:1, and carry out oxygen-pressure ammonia leaching in a pressure autoclave with an oxygen partial pressure of 15 MPa, a temperature of 170°C, and a leaching time of 120 min. Filter to obtain the leachate and leaching residue;

[0043] 3) Acid precipitation: Under the condition of stirring speed of 300 rpm, control the liquid temperature in the kettle at 45°C, slowly add 30% sulfuric acid to the leaching solution to adjust the pH to 2 for acid precipitation, and a white flocculent precipitate will appear, which is filtered and separated to obtain a mixture of ammonium tungstate and ammonium molybdate;

[0044] 4) Sulfidation: Introduce hydrogen sulfide gas into the sulfidator to sulfidize the precipitate. The sulfidation temperature is 20°C, the sulfidation time is 2h, and the total air flow rate is 5L / min;

[0045] 5) Acidification: Add hydrochloric acid to the thioammonium salt for acidification reaction, control the end point pH of the reaction to be 1.0, the reaction temperature to be 60°C, and the reaction time to be 1 hour;

[0046] 6) Calcination: calcining the trisulfide under nitrogen protection at a temperature of 980°C and a calcination time of 60 min;

[0047] 7) Crushing: The calcined material was crushed to obtain 112 g of product, MoS2: WS2 = 7.6: 1. Example 2

[0048] 1) Oxidation roasting: Take 300g of tungsten-molybdenum paragenetic ore (its main element content is: Mo 7.21%, W 6.25% in terms of WO3, Si 45%, Fe 10%, Ca 9.0%, Mg 5.5%), ball-mill the tungsten-molybdenum paragenetic ore to ≥200 mesh, add 37.88g of MoO3 (converted to Mo is 25.25g), control the mass ratio of Mo and WO3 to 10:4, and mix the materials; then transfer them to a rotary kiln for roasting at a roasting temperature of 550°C, a roasting time of 4.5h, and a rotary kiln speed of 3min / rev to obtain a roasted material;

[0049] 2) Oxygen-pressure ammonia leaching: add 18% ammonia water to the roasted material to adjust the slurry, control the liquid-solid ratio to 3:1, and carry out oxygen-pressure ammonia leaching in a pressure autoclave with an oxygen partial pressure of 17 MPa, a temperature of 180°C, and a leaching time of 100 min. Filter to obtain the leachate and leaching residue;

[0050] 3) Acid precipitation: Under the condition of stirring speed of 300 rpm, control the liquid temperature in the kettle at 50°C, slowly add 30% sulfuric acid to the leaching solution to adjust the pH to 1.5 for acid precipitation, and a white flocculent precipitate will appear, which is filtered and separated to obtain a mixture of ammonium tungstate and ammonium molybdate;

[0051] 4) Sulfidation: hydrogen sulfide gas is introduced into the sulfidator to perform sulfidation treatment on the precipitate. The sulfidation temperature is 25°C, the sulfidation time is 1.5h, and the total air flow rate is 5L / min;

[0052] 5) Acidification: Add hydrochloric acid to the thioammonium salt for acidification reaction, control the end point pH of the reaction to be 1.0, the reaction temperature to be 65°C, and the reaction time to be 1.5h;

[0053] 6) Calcination: calcining the trisulfide under nitrogen protection at a temperature of 1000°C and a calcination time of 50 min;

[0054] 7) Crushing: The calcined material was crushed to obtain 93 g of product, MoS2: WS2 = 3.9:1. Example 3

[0055] 1) Oxidation roasting: Take 500g of tungsten-molybdenum paragenetic ore (its main element content is: Mo 7.21%, W 6.25% in terms of WO3, Si 45%, Fe 10%, Ca 9.0%, Mg 5.5%), ball-mill the tungsten-molybdenum paragenetic ore to ≥200 mesh, add MoO324.05g (converted to Mo is 16.03g) thereto, control the mass ratio of Mo and WO3 to 10:6, and mix the materials; then transfer them into a rotary kiln for roasting, the roasting temperature is 600℃, the roasting time is 4h, and the rotary kiln speed is 3min / revolution to obtain the roasted material;

[0056] 2) Oxygen-pressure ammonia leaching: add 20% ammonia water to the roasted material to adjust the slurry, control the liquid-solid ratio to 4:1, and carry out oxygen-pressure ammonia leaching in a pressure autoclave, with an oxygen partial pressure of 15-20Mpa, a temperature of 190°C, and a leaching time of 80min. Filter to obtain the leachate and leaching residue;

[0057] 3) Acid precipitation: Under the condition of stirring speed of 400 rpm, control the liquid temperature in the kettle at 50°C, slowly add 40% sulfuric acid to the leaching solution to adjust the pH to 1 for acid precipitation, and a white flocculent precipitate will appear, which is filtered and separated to obtain a mixture of ammonium tungstate and ammonium molybdate;

[0058] 4) Sulfidation: hydrogen sulfide gas is introduced into the sulfidator to perform sulfidation treatment on the precipitate, the sulfidation temperature is 25°C, the sulfidation time is 1 hour, and the total air flow rate is 5L / min, to obtain ammonium tetrathiomolybdate and ammonium tetrathiotungstate sulfide salts;

[0059] 5) Acidification: Add hydrochloric acid to the thioammonium salt for acidification reaction, control the end point pH of the reaction to be 1.5, the reaction temperature to be 70°C, and the reaction time to be 1.5h;

[0060] 6) Calcination: Calcine the trisulfide under nitrogen protection at a temperature of 1010°C and a calcination time of 45 min;

[0061] 7) Crushing: The calcined material was crushed to obtain 114 g of product, MoS2: WS2 = 2.6: 1. Example 4

[0062] 1) Oxidation roasting: Take 1000g of tungsten-molybdenum paragenetic ore (its main element content is: Mo 7.21%, W 6.25% in terms of WO3, Si 45%, Fe 10%, Ca 9.0%, Mg 5.5%), ball-mill the tungsten-molybdenum paragenetic ore to ≥200 mesh, add 9g of MoO3 (converted to Mo is 6g) to it, control the mass ratio of Mo and WO3 to 10:8, and mix the materials; then transfer them to a rotary kiln for roasting at a roasting temperature of 650°C, a roasting time of 3.5h, and a rotary kiln speed of 3min / rev to obtain a roasted material;

[0063] 2) Oxygen-pressure ammonia leaching: add 22% ammonia water to the roasted material to adjust the slurry, control the liquid-solid ratio to 5:1, and carry out oxygen-pressure ammonia leaching in a pressure autoclave with an oxygen partial pressure of 20 MPa, a temperature of 200°C, and a leaching time of 60 min. Filter to obtain the leaching liquid and leaching residue;

[0064] 3) Acid precipitation: Under the condition of stirring speed of 400 rpm, control the liquid temperature in the kettle at 55°C, slowly add 40% sulfuric acid to the leaching solution to adjust the pH to 1 for acid precipitation, and a white flocculent precipitate will appear, which is filtered and separated to obtain a mixture of ammonium tungstate and ammonium molybdate;

[0065] 4) Sulfidation: Introduce hydrogen sulfide gas into the sulfidator to sulfidize the precipitate. The sulfidation temperature is 30°C, the sulfidation time is 1 hour, and the total air flow rate is 5L / min;

[0066] 5) Acidification: Add hydrochloric acid to the thioammonium salt for acidification reaction, control the end point pH of the reaction to be 1.5, the reaction temperature to be 80°C, and the reaction time to be 2h;

[0067] 6) Calcination: calcining the trisulfide under nitrogen protection at a temperature of 1020°C and a calcination time of 40 min;

[0068] 7) Crushing: The calcined material was crushed to obtain 188g of product, MoS2:WS2=1.9:1. Example 5

[0069] 1) Oxidative roasting: Take 500g of tungsten-molybdenum mixed waste catalyst, the main components of which are as follows: WO315%, MoO3 7.5% (converted to Mo 5%), Al2O350%, Ni 5%, wet-mill the tungsten-molybdenum mixed waste catalyst ≥200 mesh, add MoO3105g (converted to Mo is 70g) to it, control the mass ratio of Mo and WO3 to 10:8, and mix; then transfer to a rotary kiln for roasting, roasting conditions: temperature: 650℃, time: 3.5h, rotation speed: 3min / revolution, to obtain a roasted material;

[0070] 2) Oxygen-pressure ammonia leaching: add 22% ammonia water to the roasted material to adjust the slurry, control the liquid-solid ratio to 5:1, and carry out oxygen-pressure ammonia leaching in a pressure autoclave, with an oxygen partial pressure of 20 MPa, a temperature of 200°C, and a leaching time of 60 min. Filter the leaching solution, and treat the leached residue separately;

[0071] 3) Acid precipitation: At a stirring speed of 400 rpm and a temperature in the kettle of 55°C, add 40% sulfuric acid to adjust the pH to 1.0 for acid precipitation. The white flocculent precipitate is a mixture of ammonium tungstate and ammonium molybdate.

[0072] 4) Sulfidation: introduce hydrogen sulfide gas into the sulfurizer to perform sulfurization treatment on the ammonium tungstate and ammonium molybdate mixture, with the sulfurization temperature at 30°C, the sulfurization time at 1h, and the gas flow rate at 5L / min;

[0073] 5) Acidification: Add hydrochloric acid to the thioammonium salt for acidification reaction, control the end point pH of the reaction to be 1.5, the reaction temperature to be 80°C, and the reaction time to be 2h;

[0074] 6) Calcination: Calcine the trisulfide (a mixture of tungsten trisulfide and molybdenum trisulfide) under nitrogen protection, calcination temperature: 1020℃, time: 40min;

[0075] 6) Crushing: The calcined material is crushed by air flow to obtain 275g of product.

[0076] The friction coefficient of the composites prepared in Examples 1-5 was tested (using an inclined friction coefficient tester), and commercially available tungsten sulfide and molybdenum sulfide were used for testing and comparison. The test results are shown in Table 1.

[0077] Table 1

[0078] Example 1 Example 2 Example 3 Example 4 Example 5 Tungsten disulfide (99%) Molybdenum disulfide (99%) Friction coefficient 0.059 0.065 0.042 0.047 0.056 0.06 0.08

[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for producing lubricating products using tungsten and molybdenum resources, characterized in that: The following steps are involved: 1) Oxidation roasting: convert the mass of W element into WO3, adjust the mass ratio of Mo and WO3 in tungsten and molybdenum resources to 10:2-8, crush and roast to obtain roasting material; The tungsten and molybdenum resources include tungsten-molybdenum paragenetic ore and waste catalysts containing tungsten and molybdenum; 2) Oxygen-pressure ammonia leaching: Add ammonia water to the roasted material to prepare the slurry, carry out oxygen-pressure ammonia leaching in a pressure autoclave, and filter to obtain the leaching liquid and leaching residue; 3) Acid precipitation: add sulfuric acid to the leaching solution to adjust the pH of the system for acid precipitation, filter and separate to obtain the precipitate; 4) Sulfidation: introducing hydrogen sulfide gas to carry out sulfidation treatment on the precipitate to obtain thioammonium salt containing ammonium tetrathiomolybdate and ammonium tetrathiotungstate; 5) Acidification: Add hydrochloric acid to the thioammonium salt for acidification reaction, filter and separate to obtain trisulfide; 6) Calcination: calcining the trisulfide under a protective atmosphere; 7) Crushing: crush the calcined material to obtain.

2. The method according to claim 1, characterized in that In step 1), the powder is crushed by ball milling to a size of ≥200 mesh.

3. The method according to claim 1 or 2, characterized in that: In step 1), the calcination temperature is 500-650°C and the calcination time is 3.5-4.5h.

4. The method according to claim 1, characterized in that In step 2), the concentration of aqueous ammonia is 20-25%, and the liquid-to-solid ratio is 1-5:

1.

5. The method according to claim 1, characterized in that: In step 2), the process conditions of oxygen-pressure ammonia leaching are as follows: oxygen partial pressure is 15-20 MPa, pH is 10.5-12.0, temperature is 170-200° C., and leaching time is 60-120 min.

6. The method according to claim 1, characterized in that In step 3), the acid precipitation operation is as follows: under stirring, 30-40% sulfuric acid is added to the leaching solution to adjust the pH to 1-2 for acid precipitation, and the acid precipitation temperature is 45-55°C.

7. The method according to claim 1, characterized in that In step 4), the vulcanization temperature is 20-30°C and the vulcanization time is 1-2h.

8. The method according to claim 1, characterized in that In step 5), hydrochloric acid is added for acidification reaction, the end point pH of the reaction is controlled to be 1.0-1.5, the acidification reaction temperature is 60-80°C, and the reaction time is 1-2h.

9. The method according to claim 1, characterized in that: In step 6), the calcination temperature is 980-1020° C. and the calcination time is 40-60 min.