Continuous preparation method and system of chloroiridic acid solution or crystal

Abstract

The invention belongs to the technical field of precious metal compound preparation, and discloses a continuous preparation method and system for a chloroiridic acid solution or crystal, and the continuous preparation method comprises the following steps: 1) uniformly mixing iridium powder with solid alkali and solid oxide, and then carrying out heating reaction to obtain an alkali fusion material; 2) washing the alkali fusion material with water and carrying out solid-liquid separation to obtain a solid; 3) dissolving the solid in concentrated hydrochloric acid to obtain a chloroiridic acid solution; and 4) concentrating and crystallizing the chloroiridic acid solution to obtain a chloroiridic acid crystal. According to the method and the system, the working efficiency can be greatly improved, the simple substance iridium is used as a raw material, the chloroiridic acid solution or crystal with stable yield and product quality can be obtained through a continuous preparation process, and the method and the system have the advantages of simplicity in operation, high yield, less waste liquid, safety, environment friendliness and the like.

Description

Technical Field

[0001] This invention belongs to the field of precious metal compound preparation technology, specifically, it relates to a continuous preparation method and system for chloroiridium acid solution or crystals. Background Technology

[0002] Iridium is a highly malleable, silvery-white noble metal with a melting point of 2410±40℃ and a boiling point of 4130℃, typically forming a face-centered cubic crystal. Iridium is physically and chemically stable, exhibiting strong corrosion resistance and oxidation resistance, and has wide applications in industrial catalysis, high-temperature resistant materials, and antioxidant coatings. For example, iridium compounds are extensively used as homogeneous catalysts in methanol carbonylation to acetic acid and acetic anhydride production processes.

[0003] Chloroiridic acid is an important compound of iridium, appearing as brownish-red needle-like crystals, often in granular or blocky form. It is commonly used as a precursor in the preparation of iridium catalysts. Chloroiridic acid solutions are also indispensable chemical raw materials in fields such as hydrogenation catalysts, polymerization catalysts, and organic synthesis.

[0004] Existing methods for preparing chloroiridium acid mainly include high-temperature chlorination, alkali fusion, and electrolysis. The high-temperature chlorination method involves uniformly mixing iridium powder with sodium chloride, then introducing chlorine gas and carrying out the chlorination reaction at 600-700℃. After the reaction, sodium chloroiridium is leached with water. The leachate is then oxidized by chlorine or nitric acid, and ammonium chloride solution is added to form ammonium chloroiridium precipitate. This precipitate is then dissolved in aqua regia to obtain a chloroiridium acid solution (used in precious metal metallurgy and deep processing of products). This method is inefficient and complex, and the use of chlorine gas increases the operational difficulty. The electrolysis method involves dissolving iridium powder in hydrochloric acid solution using alternating current in a U-shaped electrolytic cell to obtain chloroiridium acid (see patent document 201010290275.5, "An Electrochemical Dissolution Method for Iridium Powder"). This method yields chloroiridium acid with high purity, but its disadvantages include high requirements for electrolysis equipment, long electrolysis time, and limited processing capacity. The most commonly used method for synthesizing chloroiridium acid is the alkali fusion method. This involves mixing iridium powder with a solid alkali (such as NaOH or KOH) and a solid oxidizing agent (such as Na₂O₂ or KNO₃), then heating and melting the mixture. After the reaction is complete, the melt is leached with hydrochloric acid. After multiple filtrations and washings, ammonium chloride solution is added to produce ammonium chloroiridium precipitate, which is then dissolved in aqua regia and distilled under reduced pressure to obtain a chloroiridium acid solution. Patent document 201510847873.0 improves the alkali fusion method by mixing iridium powder with a mixed alkali and heating the mixture at 500-720°C. After the reaction, the mixture is washed with water to remove salt, dissolved in aqua regia, and filtered to obtain the chloroiridium acid product, thus simplifying the synthesis process.

[0005] With the widespread application of iridium, the market demand for its compounds is gradually increasing. However, existing methods for preparing iridium catalysts, especially chloroiridium acid solutions, are mostly laboratory-scale, with small single-batch synthesis, resulting in unstable yields and product quality, long production cycles, high manufacturing costs, insufficient utilization of solvents and raw materials, and large amounts of waste liquid. These problems cannot meet the growing demand for iridium catalysts. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, the present invention aims to provide a continuous preparation method and system for chloroiridic acid solutions or crystals. This method and system can significantly improve work efficiency. Using elemental iridium as raw material, a continuous preparation process can yield chloroiridic acid solutions or crystals with stable yield and product quality. It offers advantages such as simple operation, high yield, low waste liquid, and safety and environmental friendliness.

[0007] A first aspect of the present invention provides a continuous preparation method for chloroiridic acid solution or crystals, the continuous preparation method comprising the following steps:

[0008] 1) Iridium powder is mixed evenly with solid alkali and solid oxide and then heated to react, resulting in alkali-fused material;

[0009] 2) The alkali-fused material is washed with water and subjected to solid-liquid separation to obtain a solid;

[0010] 3) Dissolve the solid in concentrated hydrochloric acid to obtain a chloroiridium acid solution;

[0011] 4) The chloroiridic acid solution was concentrated and crystallized to obtain chloroiridic acid crystals.

[0012] A second aspect of the present invention provides a continuous preparation system for chloroiridic acid solution or crystals used in the above-described continuous preparation method, the continuous preparation system comprising an alkali melting unit, a water washing unit, a separation unit, a dissolution unit, and a crystallization unit;

[0013] The alkali fusion unit is a heating device with a stirring device, the water washing unit is a first stirred reactor, the separation unit is a solid-liquid separation device, the dissolution unit is a second stirred reactor, and the crystallization unit is a rotary evaporator.

[0014] The outlet of the heating device is connected to the solid inlet of the first stirred reactor, the outlet of the first stirred reactor is connected to the inlet of the solid-liquid separation device, the solid outlet of the solid-liquid separation device is connected to the solid inlets of the first stirred reactor and the second stirred reactor, the outlet of the second stirred reactor is connected to the inlet of the solid-liquid separation device, and the liquid outlet of the solid-liquid separation device is connected to the inlet of the wastewater collection device and the rotary evaporator.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The preparation process is carried out continuously, which minimizes material loss caused by material transfer, equipment cleaning and other operations, and improves the utilization rate of precious metals.

[0017] 2. All solid materials containing precious metals in the process are concentrated in the solid-liquid separation equipment before further processing. They can be repeatedly washed and dissolved without being removed, which is beneficial to operation, improves yield, and reduces loss of precious metals.

[0018] 3. During the washing process, operations such as heating, stirring, controlling the washing time, and timely separation of solutions containing alkali metal ions from solids are used to reduce the residue of alkali metal ions in the product. In particular, the washing solution is kept neutral to ensure that the content of alkali metal ions in the product solution is below 100 ppm.

[0019] 4. Using a low-temperature soaking followed by a high-temperature dissolution method for hydrochloric acid dissolution is beneficial for the hydrochloric acid to fully contact and corrode the alkali-melted material, thereby improving dissolution efficiency and product yield.

[0020] 5. The main waste liquid generated by this process is an alkaline aqueous solution containing alkali metal ions produced by centrifugal separation and an acidic aqueous solution produced by concentration and crystallization. The two solutions can be mixed and the pH value adjusted to neutral for treatment. In particular, the washing liquid can be reused when it is neutral. Therefore, this process has the advantages of low waste liquid volume and simple treatment.

[0021] 6. This process is suitable for the continuous preparation of large quantities of chloroiridic acid catalyst solutions and crystals, and has the advantages of mild conditions, simple operation, high yield, stable product quality, and low impurity content.

[0022] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process flow of a continuous preparation system for chloroiridic acid solution or crystals according to the present invention.

[0024] Explanation of reference numerals in the attached drawings: 1. Heating equipment; 2. First stirred reactor; 3. Solid-liquid separation equipment; 4. Second stirred reactor; 5. Rotary evaporator.

[0025] Figure 2 This is an electron microscope image of the material obtained after washing with water in Example 1. Detailed Implementation

[0026] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0027] According to a first aspect of the present invention, a continuous preparation method for chloroiridic acid solution or crystals is provided, the continuous preparation method comprising the following steps:

[0028] 1) Iridium powder is mixed evenly with solid alkali and solid oxide and then heated to react, resulting in alkali-fused material;

[0029] 2) The alkali-fused material is washed with water and subjected to solid-liquid separation to obtain a solid;

[0030] 3) Dissolve the solid in concentrated hydrochloric acid to obtain a chloroiridium acid solution;

[0031] 4) The chloroiridic acid solution was concentrated and crystallized to obtain chloroiridic acid crystals.

[0032] In this invention, the solid alkali can be at least one of alkali metal hydroxides. The solid oxide can be at least one of alkali metal peroxides.

[0033] Preferably, the alkali metal element in the alkali metal hydroxide and alkali metal peroxide is sodium or potassium.

[0034] According to the present invention, the mass ratio of the solid alkali to the solid oxide can be 1:2-5, and the mass ratio of the iridium powder to the total amount of the solid alkali and solid oxide can be 1:2-5.

[0035] In a preferred embodiment, the heating reaction is carried out under stirring and continuous air flow conditions; the air flow rate is 20 ml / min-200 ml / min; the heating conditions include: programmed temperature rise to 620-750℃ at a rate of 3-4℃ / min, maintaining the temperature for 4-8 hours after reaching the temperature, and then stopping the heating and allowing the temperature to cool naturally.

[0036] Generally, the alkali-fused material is cooled to a temperature greater than 80℃ but less than 100℃ before entering the washing step. Washing is preferably carried out under stirring and heating conditions, and usually requires at least three washes. Washing can be completed when the washing solution reaches a near-neutral pH. After each wash, the solid-liquid mixture must undergo solid-liquid separation. The washing solution is discharged and collected for centralized treatment. The washing solution is an alkaline aqueous solution containing alkali metal ions, while the concentration and crystallization step produces an acidic aqueous solution. The two solutions can be mixed and the pH adjusted to neutral before treatment.

[0037] Preferably, the washing conditions include: a temperature of 40-80℃, preferably 50-70℃; a single washing time of 30min-5h, preferably 1-3h; the amount of deionized water used in a single washing is 30-200 times the mass of iridium powder, preferably 50-100 times; and washing until the washing solution is neutral.

[0038] In this invention, the concentrated hydrochloric acid can be concentrated hydrochloric acid with a concentration of more than 20% (mass fraction of hydrogen chloride), preferably concentrated hydrochloric acid with a concentration of 36% to 38%.

[0039] Preferably, the amount of concentrated hydrochloric acid used is 20-25 times the mass of iridium powder.

[0040] In this invention, the dissolution is carried out by low-temperature soaking followed by high-temperature dissolution. Specifically, the mixture of solid and concentrated hydrochloric acid is heated to 30-40°C and stirred thoroughly for 30 min-3 h. Then, heating and stirring are stopped, and the mixture is soaked at room temperature (generally 25°C) for more than 12 h. The mixture is then heated to reflux for dissolution for 2-10 h, preferably 3-6 h.

[0041] Under normal circumstances, the above-mentioned dissolution method can dissolve the solid more completely. To prevent a small amount of insoluble matter, the dissolved material can be separated into solid and liquid to obtain a chloroiridium acid solution. If there is any solid residue, it can be combined with the next batch of alkali-fused material for processing.

[0042] Depending on the product's intended use and requirements, the chloroiridic acid solution can be further concentrated and crystallized to obtain a higher concentration of chloroiridic acid solution or chloroiridic acid crystals.

[0043] According to a second aspect of the present invention, the present invention provides a continuous preparation system for chloroiridic acid solution or crystals used in the above-described continuous preparation method, the continuous preparation system comprising an alkali fusion unit, a water washing unit, a separation unit, a dissolution unit and a crystallization unit;

[0044] The alkali fusion unit is a heating device with a stirring device, the water washing unit is a first stirred reactor, the separation unit is a solid-liquid separation device, the dissolution unit is a second stirred reactor, and the crystallization unit is a rotary evaporator.

[0045] The outlet of the heating device is connected to the solid inlet of the first stirred reactor, the outlet of the first stirred reactor is connected to the inlet of the solid-liquid separation device, the solid outlet of the solid-liquid separation device is connected to the solid inlets of the first stirred reactor and the second stirred reactor, the outlet of the second stirred reactor is connected to the inlet of the solid-liquid separation device, and the liquid outlet of the solid-liquid separation device is connected to the inlet of the wastewater collection device and the rotary evaporator.

[0046] In this invention, the heating device can be selected from one of the following high-temperature furnaces: box-type muffle furnace, tube furnace, crucible furnace, etc.

[0047] The first stirred reactor is equipped with a deionized water inlet and a pH measuring device, which can be used to measure the pH value of the washing liquid in the reactor.

[0048] The solid-liquid separation equipment can be a centrifuge.

[0049] The second stirred reactor is equipped with a concentrated hydrochloric acid inlet and heating and reflux devices.

[0050] In this invention, the various devices can be connected by pipelines, pumps, conveyor belts, screw conveyors, etc., to achieve material transport and thus continuous preparation. These connection methods are conventionally used in the field and will not be described in detail here.

[0051] The substances, devices, and process parameters not limited in this invention can be selected according to existing technology and are conventional technical means in this field.

[0052] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0053] In the following embodiments, the data is obtained using the following method:

[0054] The concentrations of iridium and sodium ions in the chloroiridium acid solution were determined by ICP (inductively coupled plasma mass spectrometry, Agilent 7500cx).

[0055] Example 1

[0056] like Figure 1 As shown, the continuous preparation system for chloroiridic acid solution or crystals includes an alkali fusion unit, a water washing unit, a separation unit, a dissolution unit, and a crystallization unit; the alkali fusion unit is a heating device 1 with a stirring device, the water washing unit is a first stirred reactor 2, the separation unit is a solid-liquid separation device 3, the dissolution unit is a second stirred reactor 4, and the crystallization unit is a rotary evaporator 5.

[0057] The outlet of the heating device 1 is connected to the solid inlet of the first stirred reactor 2, and the outlet of the first stirred reactor 2 is connected to the inlet of the solid-liquid separation device 3. The solid outlet of the solid-liquid separation device 3 is connected to the solid inlets of the first stirred reactor 2 and the second stirred reactor 4, respectively. The outlet of the second stirred reactor 4 is connected to the inlet of the solid-liquid separation device 3, and the liquid outlet of the solid-liquid separation device 3 is connected to the inlet of the wastewater collection device and the rotary evaporator 5, respectively. The heating device 1 is a high-temperature furnace; the first stirred reactor 2 is equipped with a deionized water inlet and a pH measuring device; the solid-liquid separation device 3 is a centrifuge; and the second stirred reactor 4 is equipped with a concentrated hydrochloric acid inlet and a heating and reflux device.

[0058] The continuous preparation method of chloroiridium acid solution or crystals using the above-mentioned continuous preparation system includes: weighing 300g of iridium powder, 225g of sodium hydroxide, and 675g of sodium peroxide, mixing them evenly, and heating them in heating device 1. Air is introduced at 100mL / min, stirring is started, and the temperature is increased to 700℃ at 3℃ / min, held at the temperature for 5 hours, and then heating is stopped and the temperature is lowered. When the temperature drops to 90℃, the alkali-fused material is added to the first stirred reactor 2 through the solid inlet, and deionized water is added to the first stirred reactor 2 through the deionized water inlet. The amount of deionized water is 80 times that of the iridium powder. Under stirring conditions, the first stirred reactor 2 is heated to 60℃ and washed with water for 2 hours.

[0059] The mixture is pumped and piped to solid-liquid separation unit 3. After solid-liquid separation, the alkaline wastewater is collected and centrally treated, while the solid is returned to the first stirred reactor 2 for further washing. This washing process is repeated four times with neutral water. The solid is then obtained after centrifugation. Electron micrographs of the solid are shown below. Figure 2 As shown, the solid is fed into the second stirred reactor 4, and 36% concentrated hydrochloric acid is added at 20 times the amount of iridium powder. The mixture is heated to 35°C under stirring and maintained for 2 hours. Heating and stirring are then stopped, and the mixture is left to soak for 12 hours. Heating and heating are continued until reflux, followed by further heating and dissolution for 5 hours, until the solution turns reddish-brown. The dissolved material is then pumped and piped to the solid-liquid separation device 3. The separated liquid is the chloroiridium acid solution, which can be sent to the rotary evaporator 5 for concentration and crystallization to further obtain reddish-brown chloroiridium acid crystals.

[0060] The concentration of iridium in the chloroiridium acid solution was found to be 3.63 wt%, and the concentration of sodium ions was 0.009 wt%.

[0061] Example 2

[0062] The continuous preparation system used is the same as in Example 1, except that it does not include the rotary evaporator 5. The continuous preparation method of the chloroiridium acid solution includes: weighing 400g of iridium powder, 320g of sodium hydroxide, and 1280g of sodium peroxide, mixing them evenly, and then heating them in heating device 1. Air is introduced at 100mL / min, stirring is started, and the temperature is increased to 720℃ at 3℃ / min, held at the temperature for 7h, and then heating is stopped and the temperature is lowered. When the temperature drops below 95℃, the alkali-fused material is added to the first stirred reactor 2 through the solid inlet, and deionized water is added to the first stirred reactor 2 through the deionized water inlet. The amount of deionized water is 70 times that of the iridium powder. Under stirring conditions, the first stirred reactor 2 is heated to 60℃ and washed with water for 3h.

[0063] The mixture is pumped and piped to solid-liquid separation unit 3. After solid-liquid separation, the alkaline wastewater is collected and centrally treated, while the solid is returned to the first stirred reactor 2 for further washing. This washing process is repeated five times, with the washing liquid being neutral. After centrifugation, the solid is sent to the second stirred reactor 4, where 36% concentrated hydrochloric acid is added at 25 times the amount of iridium powder. The mixture is heated to 40°C under stirring and maintained for 2 hours. Heating and stirring are then stopped, and the mixture is soaked for 24 hours. Heating and heating are continued until reflux, followed by further heating and dissolution for 5 hours, until the solution turns reddish-brown. The dissolved material is then pumped and piped to solid-liquid separation unit 3, and the separated liquid is the chloroiridium acid solution.

[0064] The concentration of iridium in the chloroiridic acid solution was found to be 3.64 wt%, and the concentration of sodium ions was 0.008 wt%.

[0065] Example 3

[0066] The continuous preparation system used is the same as in Example 1, except that it does not include the rotary evaporator 5. The continuous preparation method of the chloroiridium acid solution includes: weighing 200g of iridium powder, 200g of sodium hydroxide, and 400g of sodium peroxide, mixing them evenly, and then heating them in heating device 1. Air is introduced at 100mL / min, stirring is started, and the temperature is increased to 680℃ at 3℃ / min, held at the temperature for 5 hours, and then heating is stopped and the temperature is lowered. When the temperature drops below 85℃, the alkali-fused material is added to the first stirred reactor 2 through the solid inlet, and deionized water is added to the first stirred reactor 2 through the deionized water inlet. The amount of deionized water is 80 times that of the iridium powder. Under stirring conditions, the first stirred reactor 2 is heated to 60℃ and washed with water for 1 hour.

[0067] The mixture is pumped and piped to solid-liquid separation unit 3. After solid-liquid separation, the alkaline wastewater is collected and centrally treated, while the solid is returned to the first stirred reactor 2 for further washing. This washing is repeated four times, with the washing liquid being neutral. After centrifugation, the solid is sent to the second stirred reactor 4, where 36% concentrated hydrochloric acid is added at 20 times the amount of iridium powder. The mixture is heated to 40°C under stirring and maintained for 2 hours. Heating and stirring are then stopped, and the mixture is soaked for 12 hours. Heating and heating are continued until reflux, followed by further heating and dissolution for 5 hours, until the solution turns reddish-brown. The dissolved material is then pumped and piped to solid-liquid separation unit 3, and the separated liquid is the chloroiridium acid solution.

[0068] The concentration of iridium in the chloroiridic acid solution was found to be 3.61 wt%, and the concentration of sodium ions was 0.006 wt%.

[0069] As can be seen from the data in the examples, the method of the present invention can achieve continuous preparation of chloroiridic acid, with mild process conditions, relatively stable iridium concentration, and low sodium ion content. Figure 2 As can be seen, the iridium oxide particles obtained by this invention are of uniform size, indicating that the alkali melting is relatively sufficient and there is no fusion.

[0070] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A continuous preparation method for chloroiridic acid solution or crystals, characterized in that, The continuous preparation method includes the following steps: 1) Iridium powder is mixed evenly with solid alkali and solid oxide and then heated to react, resulting in alkali-fused material; 2) The alkali-fused material is washed with water and subjected to solid-liquid separation to obtain a solid; 3) Dissolve the solid in concentrated hydrochloric acid to obtain a chloroiridium acid solution; 4) The chloroiridic acid solution was concentrated and crystallized to obtain chloroiridic acid crystals.

2. The continuous preparation method of chloroiridium acid solution or crystals according to claim 1, wherein, The solid alkali is at least one of alkali metal hydroxides; the solid oxide is at least one of alkali metal peroxides; Preferably, the alkali metal element in the alkali metal hydroxide and alkali metal peroxide is sodium or potassium.

3. The continuous preparation method of chloroiridium acid solution or crystals according to claim 1 or 2, wherein, The mass ratio of the solid alkali to the solid oxide is 1:2-5, and the mass ratio of the iridium powder to the total amount of the solid alkali and solid oxide is 1:2-5.

4. The continuous preparation method of chloroiridium acid solution or crystals according to claim 1, wherein, The heating reaction is carried out under stirring and continuous air flow conditions; the air flow rate is 20 mL / min-200 mL / min; the heating conditions include: programmed temperature rise to 620-750℃, heating rate of 3-4℃ / min, holding the temperature for 4-8 hours after reaching the temperature, and then stopping the heating and allowing it to cool naturally.

5. The continuous preparation method of chloroiridium acid solution or crystals according to claim 1, wherein, The washing conditions include: a temperature of 40-80℃, preferably 50-70℃; a single washing time of 30min-5h, preferably 1-3h; a single washing with deionized water amount of 30-200 times the mass of iridium powder, preferably 50-100 times; and washing until the washing solution is neutral.

6. The continuous preparation method of chloroiridium acid solution or crystals according to claim 1, wherein, The concentrated hydrochloric acid is concentrated hydrochloric acid with a concentration of more than 20%, preferably concentrated hydrochloric acid with a concentration of 36% to 38%; The amount of concentrated hydrochloric acid used is 20-25 times the mass of iridium powder.

7. The continuous preparation method of chloroiridic acid solution or crystals according to claim 1, wherein, Dissolution is carried out by low-temperature soaking followed by high-temperature dissolution: the mixture of solid and concentrated hydrochloric acid is heated to 30-40°C and stirred thoroughly for 30 min-3 h. Then, heating and stirring are stopped, and the mixture is soaked at room temperature for more than 12 h. The mixture is then heated to reflux for dissolution for 2-10 h, preferably 3-6 h.

8. The continuous preparation method of chloroiridic acid solution or crystals according to claim 1 or 7, wherein, Step 3) includes solid-liquid separation of the dissolved material to obtain a chloroiridium acid solution.

9. The continuous preparation system for chloroiridic acid solution or crystals used in the continuous preparation method according to any one of claims 1-8, characterized in that, The continuous preparation system includes an alkali melting unit, a water washing unit, a separation unit, a dissolution unit, and a crystallization unit; The alkali fusion unit is a heating device with a stirring device, the water washing unit is a first stirred reactor, the separation unit is a solid-liquid separation device, the dissolution unit is a second stirred reactor, and the crystallization unit is a rotary evaporator. The outlet of the heating device is connected to the solid inlet of the first stirred reactor, the outlet of the first stirred reactor is connected to the inlet of the solid-liquid separation device, the solid outlet of the solid-liquid separation device is connected to the solid inlets of the first stirred reactor and the second stirred reactor, the outlet of the second stirred reactor is connected to the inlet of the solid-liquid separation device, and the liquid outlet of the solid-liquid separation device is connected to the inlet of the wastewater collection device and the rotary evaporator.

10. The continuous preparation system for chloroiridium acid solution or crystals according to claim 9, wherein, The heating equipment is a high-temperature furnace, selected from one of a box-type muffle furnace, a tube furnace, or a crucible furnace; The first stirred reactor is equipped with a deionized water inlet and a pH measuring device; The solid-liquid separation equipment is a centrifuge; The second stirred reactor is equipped with a concentrated hydrochloric acid inlet and heating and reflux devices.

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