A method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag

Abstract

The present invention belongs to the technical field of resource utilization of fluoride in electrolytic aluminum overhaul slag as solid waste, and specifically discloses a method for preparing aluminum-doped tubular magnesium fluoride from electrolytic aluminum overhaul slag. In the method, the overhaul slag is ground and sieved, subjected to a water bath reaction, and then filtered to obtain the magnesium fluoride; the magnesium fluoride is mixed with sodium fluoride and a solution containing aluminum ions under a chelating reaction of a chelating agent and a magnesium salt and ultrasonic conditions, and subjected to a hydrothermal reaction in a reactor for 1 to 2 hours. The magnesium fluoride is then dried in an oven and ground, and finally calcined in a tubular furnace to obtain a metal magnesium fluoride catalyst for catalytic reaction, the specific surface area of ​​which is greater than 180 m 2 / g, the prepared magnesium fluoride can be used for catalytic reactions such as dehydrochlorination reaction, fluorine-chlorine exchange reaction, hydrogenation reaction, and removal of nitrogen oxides. The specific surface area of ​​the prepared tubular magnesium fluoride is larger than that of the block magnesium fluoride, and the corresponding catalytic active sites are more, the catalytic activity is high, and the stability is strong.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of fluoride in solid waste electrolytic aluminum overhaul slag, and in particular to a method for preparing aluminum-doped tubular magnesium fluoride by utilizing electrolytic aluminum overhaul slag. Background Art

[0002] With the rapid development of the electrolytic aluminum industry, smelting waste slag ranks higher and higher in solid waste. During the electrolytic aluminum production process, the lining structure of the electrolytic cell is deformed and cracked due to the penetration and corrosion of the molten high-temperature electrolyte. The aluminum liquid and electrolyte in the cell leak into the bottom of the electrolytic cell through the cracks, making the electrolytic cell unable to be used normally. The cathode lining material removed when repairing the electrolytic cell is called overhaul slag. The overhaul slag contains a large amount of fluoride. If the fluoride is not properly treated, it will pose a great threat to humans and the environment.

[0003] Existing technology uses chemical methods to treat overhaul slag, using calcium hypochlorite as a cyanide remover and calcium chloride and polyaluminum chloride as defluoridants to effectively remove cyanide and fluoride from the overhaul slag. However, this process is complex, and residual waste liquid can cause secondary pollution. Alcoa uses an Ausmelt furnace to treat spent tank linings. This method, under high temperature, decomposes toxic substances in the spent tank lining into non-toxic small molecules. Furthermore, it converts insoluble fluorides into aluminum fluoride and sodium fluoride, which are then returned to the electrolytic aluminum process, achieving the goal of recycling overhaul slag. However, this method consumes a lot of energy and requires expensive equipment investment.

[0004] Due to the small specific surface area and weak surface acidity of magnesium fluoride, its application in catalytic research is greatly limited. Chinese patent CN106669742A discloses a method for preparing a magnesium fluoride catalyst with a high specific surface area and its application. The method comprises reacting an ether or alcohol solution of HF with an organic magnesium solution (the magnesium salt is selected from one of magnesium dihalide, aryl magnesium, and aromatic alcohol magnesium salt, and the organic solvent is selected from one of C1-4 alcohol, C1-4 ester, and benzene). The reaction product obtained after the reaction is dried to obtain a catalyst precursor, which is then fluorinated to obtain a catalyst with a specific surface area greater than 130 m 2 / g magnesium fluoride catalyst, used in dehydrochlorination reactions, can achieve a maximum conversion of 54.44%. Igor Sevonkaev and Egon Matijevic studied the preparation of cubic and polycrystalline spherical MgF2 using magnesium chloride and magnesium acetate as magnesium sources and NaF as a fluorine source via precipitation methods. However, their specific surface areas were not specified, and the acidic sites on the MgF2 surface were relatively few, limiting their application in catalytic research.

[0005] In addition, magnesium fluoride also has the problem of uncontrollable morphology. To address this problem, Asep Bayu DaniNandiyanto et al. used a template method using PS colloidal spheres as templates, introduced dilute solutions of MgCl2 and NH4F, and then subjected them to high-temperature treatment to remove the PS core to obtain hollow spherical MgF2. Pietrowski, M. and Wojciechowska, M. used Mg(NO3)2 and NH4F as raw materials and prepared spherical monodisperse MgF2 by microwave-assisted precipitation. However, this MgF2 preparation method still has problems such as high cost, complex process, high energy consumption, and high cost.

[0006] In summary, the existing methods for preparing aluminum-doped tubular magnesium fluoride from electrolytic aluminum overhaul slag all have the problems of complex processes, high costs, small specific surface area and low catalytic activity of the prepared magnesium fluoride. Therefore, the present invention provides an economical and highly operable overhaul slag treatment method to prepare magnesium fluoride with a large specific surface area and high catalytic activity. Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag, so as to solve the problems of the prior art method for preparing MgF2, such as the complex process and high cost, and the small specific surface area and low catalytic activity of the finally obtained MgF2.

[0008] To achieve the above-mentioned object, the present invention provides a basic solution: a method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag, comprising the following steps:

[0009] S1: The overhaul slag produced by electrolytic aluminum is crushed, ground, and sieved, and then dissolved in water to maintain a solid-liquid ratio of 1:5 to 20 between the overhaul slag and the aqueous solution. The solid-liquid mixture is then placed in a water bath at 60-80°C for 1-2 hours. The solid-liquid mixture after the water bath is filtered to obtain a solution containing sodium fluoride and aluminum ions.

[0010] A solid-liquid ratio of the overhaul slag to the aqueous solution is selected from 1:5 to 20 to extract fluoride ions from the overhaul slag to a greater extent.

[0011] S2: Dissolve the chelating agent and magnesium salt in water, mix well, react for 10-30 minutes, and then clarify the solution with 1 mol / L ammonia water;

[0012] Through the chelation reaction between the chelating agent and the magnesium salt, the Mg in the magnesium salt is 2+ Protect it so that free Mg in the solution 2+ The concentration of magnesium fluoride is reduced to prepare for the subsequent generation of magnesium fluoride.

[0013] S3: Under ultrasonic conditions, 10-30 mL of the solution containing sodium fluoride and aluminum ions obtained in step S1 is added dropwise to the clear solution obtained in step S2;

[0014] Adding a solution containing sodium fluoride and aluminum ions drop by drop can ensure that the F in the solution - Keeping it at a low concentration is beneficial to the formation and control of the morphology of magnesium fluoride.

[0015] S4: The solution obtained in step S3 is transferred to a reactor, and after a hydrothermal reaction at a temperature range of 100-200°C for 1-2 hours, the reactor is allowed to cool naturally to room temperature, and the precipitate generated in the reactor is collected by centrifugation and washed three times with deionized water and once with anhydrous ethanol;

[0016] The hydrothermal process for 1 to 2 hours helps magnesium fluoride form a better morphology. Magnesium fluoride is insoluble in water and anhydrous ethanol. Therefore, the precipitate collected by centrifugation is first washed three times with deionized water to remove water-soluble impurities, and then washed once with anhydrous ethanol to remove water-insoluble impurities. Magnesium fluoride will not be filtered out during the washing process.

[0017] S5: The obtained substance after centrifugation is placed in an oven at 60°C for drying and then ground to obtain aluminum-doped magnesium fluoride;

[0018] S6: calcining the magnesium fluoride treated in step S5 in a tubular furnace at 400-600° C. for 2-4 hours to obtain a hollow tubular magnesium fluoride.

[0019] After drying in the oven, the aluminum-doped magnesium fluoride is placed in a tube furnace and calcined in an air atmosphere in the tube furnace to effectively convert CO3 2- The anions are converted into CO2 and removed, which increases the specific surface area and active sites of magnesium fluoride, is beneficial to the subsequent catalytic reaction application, and also makes the tubular structure of magnesium fluoride more stable.

[0020] The principle and beneficial effects of the present invention are as follows: the overhaul slag is ground and sieved, subjected to a water bath reaction, and then filtered to obtain sodium fluoride and a solution containing aluminum ions, so that the fluoride ions are extracted; the slag is mixed with the sodium fluoride and the solution containing aluminum ions under a chelating reaction of a chelating agent and a magnesium salt and ultrasonic conditions, and finally subjected to a hydrothermal reaction in a reactor for 1 to 2 hours, oven-dried and ground, and finally calcined in a tubular furnace to obtain a metal magnesium fluoride catalyst for catalytic reaction, whose specific surface area is greater than 180 m 2 / g, the process is simple and the cost is low. The prepared magnesium fluoride can be used for catalytic reactions such as dehydrochlorination reaction, fluorine-chlorine exchange reaction, hydrogenation reaction, and removal of nitrogen oxides. The prepared magnesium fluoride is tubular, and the specific surface area of ​​the tubular magnesium fluoride is larger than that of the blocky magnesium fluoride, which corresponds to more catalytic active sites, high catalytic activity and strong stability.

[0021] Solution 2 is the preferred solution of the basic solution. In step S1, the sieve for sieving the overhaul slag is a 100-mesh sieve. Small particles of the overhaul slag are preferably screened out as much as possible to facilitate a more complete subsequent preparation reaction.

[0022] Option 3 is a preferred option of Option 2. The chelating agent in step S2 is one of sodium salt of ethylenediaminetetraacetic acid, sodium citrate, and sodium tartrate.

[0023] Option 4 is a preferred option of Option 3, wherein the magnesium salt is one of magnesium sulfate, magnesium chloride, and magnesium acetate.

[0024] By selecting sodium salt of ethylenediaminetetraacetic acid as the chelating agent and magnesium acetate as the magnesium salt, the selection of sodium salt of ethylenediaminetetraacetic acid and magnesium acetate are respectively the better choices among the other substances. The reaction between the two is more conducive to the formation of the morphology of magnesium fluoride. The specific reaction is as follows:

[0025] Scheme 5 is a preferred embodiment of Scheme 4. The filling degree of the solution obtained in step S3 in the reactor is 70%. In order to ensure the normal progress of the hydrothermal reaction, the filling degree of the reactor is not allowed to exceed 70% for safety reasons. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a technical roadmap for resource utilization of electrolytic aluminum overhaul slag in a method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag;

[0027] Figure 2 This is a physical picture of the unscreened and screened electrolytic aluminum overhaul slag in a method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag according to the present invention;

[0028] Figure 3 This is a scanning electron microscope image of magnesium fluoride in the form of a flower rod, a cabbage flower, a block, a sphere, and a tubular shape in a method of preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag according to the present invention;

[0029] Figure 4 is a scanning electron microscope image of magnesium fluoride prepared in Example 1 of the present invention;

[0030] Figure 5 is a scanning electron microscope image of magnesium fluoride prepared in Example 2 of the present invention;

[0031] Figure 6is a scanning electron microscope image of magnesium fluoride prepared in Example 3 of the present invention;

[0032] Figure 7 1 is a scanning electron microscope image of magnesium fluoride prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below through specific embodiments:

[0034] The present invention provides a method for preparing aluminum-doped tubular magnesium fluoride by using electrolytic aluminum overhaul slag, the method comprising the following steps:

[0035] (1) The overhaul slag produced by electrolytic aluminum is crushed, ground and screened. During the grinding and screening process, the overhaul slag is screened a number of times with a 100-mesh sieve. The overhaul slag is dissolved in water. The solid-liquid ratio of the overhaul slag to the aqueous solution is maintained at 1:5~20. The solid-liquid mixture is placed in a water bath at a temperature of 60~80℃ for 1~2 hours. The solid-liquid mixture after the water bath is filtered to obtain a solution containing sodium fluoride and aluminum ions.

[0036] (2) The chelating agent and the specific magnesium salt are dissolved in water in a certain proportion, mixed evenly, and fully reacted for 10 to 30 minutes. The mixed solution of the chelating agent and the magnesium salt is clarified with 1 mol / L ammonia water, and ammonia water is added dropwise until it is clarified, so that the pH of the solution is about 8. The main component of the chelating agent is one of sodium salt of ethylenediaminetetraacetic acid, sodium citrate, and sodium tartrate. The main component of the specific magnesium salt is one of magnesium sulfate, magnesium chloride, and magnesium acetate. This reaction uses sodium salt of ethylenediaminetetraacetic acid as the chelating agent participating in the reaction, and uses magnesium acetate as the magnesium salt participating in the reaction to react according to the ionic reaction equation: In this process, the specific reaction process is as follows:

[0037] C 10 H 14 N2O8Na2·2H2O+Mg(CH3COO)2=C 10 H 14 N2O8Mg+2CH3COONa+2H2O

[0038] (3) Under ultrasonic conditions, 10-30 mL of the solution containing sodium fluoride and aluminum ions obtained in (1) is added dropwise to the clear solution obtained in (2). The specific reaction process is as follows:

[0039] C 10 H 14 N2O8Mg+2NaF=MgF2+C 10 H 14 N2O8Na2;

[0040] (4) The solution obtained in (3) was transferred to a reactor for hydrothermal reaction. The filling degree of the solution in the reactor was 70%, the temperature of the hydrothermal reaction was 100-200 °C, and the hydrothermal reaction time was 1-2 hours. After the reactor was cooled to room temperature naturally, the precipitated material in the reactor was collected by centrifugation and washed three times with deionized water to remove water-soluble impurities, and then washed once with anhydrous ethanol to remove water-insoluble impurities.

[0041] (5) The substance produced after centrifugation is dried in an oven at 60°C and then ground to obtain aluminum-doped magnesium fluoride;

[0042] (6) The aluminum-doped magnesium fluoride treated in (5) is placed in a tubular furnace at 400-600 °C and calcined for 2-4 h to obtain a hollow tubular magnesium fluoride.

[0043] The technical solution of the present invention is described in more detail below through specific embodiments, but is not intended to limit the scope of protection of the present invention.

[0044] Example 1

[0045] A method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag, the method comprising the following steps:

[0046] (1) Pass the electrolytic aluminum overhaul slag through a 100-mesh sieve, then take 10 g of the overhaul slag and dissolve it in water. Place it in a water bath at 80 °C for 1 h. After the water bath, filter it to obtain a solution containing sodium fluoride and aluminum ions.

[0047] (2) Dissolve 5 mmol of disodium ethylenediaminetetraacetic acid and 2.5 mmol of magnesium acetate in water, mix well, react for 10 minutes, and then use 1 mol / L ammonia water to clarify the solution. The specific reaction during the process is as follows:

[0048] C 10 H 14 N2O8Na2·2H2O+Mg(CH3COO)2=C 10 H 14 N2O8Mg+2CH3COONa+2H2O

[0049] Among them C 10 H 14 N2O8Na2·2H2O is disodium ethylenediaminetetraacetate, Mg(CH3COO)2 is magnesium acetate, C 10 H 14 N2O8Mg is magnesium salt of ethylenediaminetetraacetic acid, and CH3COONa is sodium acetate.

[0050] (3) Under ultrasonic conditions, 10 ml of sodium fluoride solution leached from overhaul slag was added dropwise to the clarified solution obtained in (2). The specific reaction during the process is as follows:

[0051] C 10 H 14 N2O8Mg+2NaF=MgF2+C 10 H 14 N2O8Na2

[0052] (4) The solution obtained in (3) was transferred to a reactor and hydrothermaled at 180 °C for 2 hours. The reactor was then allowed to cool naturally to room temperature. The precipitate in the reactor was collected by centrifugation and washed three times with deionized water and once with anhydrous ethanol.

[0053] (5) The centrifuged material was dried in an oven at 60°C and then ground to obtain aluminum-doped magnesium fluoride.

[0054] (6) The aluminum-doped magnesium fluoride treated in (5) is calcined in a tube furnace at 400-600 °C for 2-4 h. The resulting magnesium fluoride has the following morphology: Figure 4 As shown, the specific surface area of ​​the prepared magnesium fluoride is 100m 2 / g.

[0055] The magnesium fluoride was pressed into a sheet with a diameter of 5 × 5 mm and placed in the middle of a nickel alloy tube reactor. A mixed gas of nitrogen and HCFC-244bb (tetrachloropropane) was introduced, with a gas flow ratio of 3:2 and a flow rate of 60 h. -1 The reaction temperature was set at 450°C and the reaction time was 24 hours. The gas mixture after the reaction was passed through a kettle of alkaline water at 45°C, and the product composition was analyzed by gas chromatography. The results showed that the conversion rate of HCFC-244bb (tetrachloropropane) gas reached 30.82%.

[0056] Example 2

[0057] A method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag, the method comprising the following steps:

[0058] (1) Pass the electrolytic aluminum overhaul slag through a 100-mesh sieve, then take 10 g of the overhaul slag and dissolve it in water. Place it in a water bath at 80 °C for 1 h. After the water bath, filter it to obtain a solution containing sodium fluoride and aluminum ions.

[0059] (2) Dissolve 5 mmol of disodium ethylenediaminetetraacetic acid and 5 mmol of magnesium acetate in water, mix well, react for 10 minutes, and then use 1 mol / L ammonia water to clarify the solution;

[0060] (3) Under ultrasonic conditions, add 10 ml of sodium fluoride solution leached from the overhaul slag dropwise to the clarified solution obtained in (2);

[0061] (4) The solution obtained in (3) was transferred to a reactor and hydrothermaled at 180 °C for 2 hours. The reactor was then allowed to cool naturally to room temperature. The precipitate in the reactor was collected by centrifugation and washed three times with deionized water and once with anhydrous ethanol.

[0062] (5) The centrifuged material was dried in an oven at 60°C and then ground to obtain aluminum-doped magnesium fluoride.

[0063] (6) The aluminum-doped magnesium fluoride treated in (5) is calcined in a tube furnace at 400-600 °C for 2-4 h. The resulting magnesium fluoride has the following morphology: Figure 5 As shown, the specific surface area of ​​the prepared magnesium fluoride is 182m 2 / g.

[0064] The magnesium fluoride obtained was pressed into tablets with a diameter of 5×5 mm. The conversion rate of HCFC-244bb (tetrachloropropane) gas was found to be 59.82% by the method described in Example 1.

[0065] Example 3

[0066] A method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag, the method comprising the following steps:

[0067] (1) Pass the electrolytic aluminum overhaul slag through a 100-mesh sieve, then take 10 g of the overhaul slag and dissolve it in water. Place it in a water bath at 80 °C for 1 h. After the water bath, filter it to obtain a solution containing sodium fluoride and aluminum ions.

[0068] (2) Dissolve 2.5 mmol of magnesium acetate in water, mix well, and react for 10 minutes. Then, use 1 mol / L ammonia water to clarify the solution to promote complete dissolution of the reactants. The specific reaction of Mg(CH3COO)2 decomposition during the process is as follows:

[0069] Mg(CH3COO)2→Mg 2+ +2CH3COO -

[0070] (3) Under ultrasonic conditions, 10 ml of sodium fluoride solution leached from overhaul slag was added dropwise to the clarified solution obtained in (2). The specific reaction during the process is as follows:

[0071] 2NaF+Mg(CH3COO)2=MgF2+2CH3COONa

[0072] (4) The solution obtained in (3) was transferred to a reactor and hydrothermaled at 180 °C for 2 hours. The reactor was then allowed to cool naturally to room temperature. The precipitate in the reactor was collected by centrifugation and washed three times with deionized water and once with anhydrous ethanol.

[0073] (5) The centrifuged material was dried in an oven at 60°C and then ground to obtain aluminum-doped magnesium fluoride.

[0074] (6) The aluminum-doped magnesium fluoride treated in (5) is calcined in a tube furnace at 400-600 °C for 2-4 h. The resulting magnesium fluoride has the following morphology: Figure 6 As shown, the specific surface area of ​​the prepared magnesium fluoride is 36m 2 / g.

[0075] The magnesium fluoride obtained was pressed into tablets with a diameter of 5×5 mm. The conversion rate of HCFC-244bb (tetrachloropropane) gas was found to be 5.6% by the method described in Example 1.

[0076] Example 4

[0077] A method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag, the method comprising the following steps:

[0078] (1) Pass the electrolytic aluminum overhaul slag through a 100-mesh sieve, then take 10 g of the overhaul slag and dissolve it in water. Place it in a water bath at 80 °C for 1 h. After the water bath, filter it to obtain a solution containing sodium fluoride and aluminum ions.

[0079] (2) Dissolve 5 mmol of disodium ethylenediaminetetraacetic acid and 10 mmol of magnesium acetate in water, mix well, react for 10 minutes, and then use 1 mol / L ammonia water to clarify the solution;

[0080] (3) Under ultrasonic conditions, add 10 ml of sodium fluoride solution leached from the overhaul slag dropwise to the clarified solution obtained in (2);

[0081] (4) The solution obtained in (3) was transferred to a reactor and hydrothermaled at 180 °C for 2 hours. The reactor was then allowed to cool naturally to room temperature. The precipitate in the reactor was collected by centrifugation and washed three times with deionized water and once with anhydrous ethanol.

[0082] (5) The centrifuged material was dried in an oven at 60°C and then ground to obtain aluminum-doped magnesium fluoride.

[0083] (6) The aluminum-doped magnesium fluoride treated in (5) is calcined in a tube furnace at 400-600 °C for 2-4 h. The resulting magnesium fluoride has the following morphology: Figure 7As shown, the specific surface area of ​​the prepared magnesium fluoride is 60m 2 / g.

[0084] The magnesium fluoride obtained was pressed into tablets with a diameter of 5×5 mm. The conversion rate of HCFC-244bb (tetrachloropropane) gas was found to be 9.8% by the method described in Example 1.

[0085] Table 1 Experimental data table of Examples 1 to 4

[0086] Solid-liquid ratio of overhaul slag and aqueous solution Ratio of EDTA sodium salt and magnesium acetate <![CDATA[Specific surface area m 2 / g]]> HCFC-244bb conversion rate / % Example 1 1:15 2:1 100 30.82% Example 2 1:15 1:1 182 59.82% Example 3 1:15 0:1 36 5.6% Example 4 1:15 1:2 60 9.8%

[0087] Table 2 Comparison of the results and specific surface areas of magnesium fluoride catalysts prepared in different patents and Example 2 for dehydrochlorination of HCFC-244bb

[0088] Patent Name HCFC-244bb conversion rate / % <![CDATA[Specific surface area m 2 / g]]> CN106669742A 54.44 More than 130 This patent 59.82 Greater than 180

[0089] As can be seen from the table above, the present invention collects the cathode lining material of the electrolytic cell, i.e., the overhaul slag, and uses the magnesium fluoride preparation method provided by the present invention to prepare a metal tubular magnesium fluoride catalyst under the preparation conditions of Example 2, with a specific surface area greater than 180 m 2 / g, while the specific surface area of ​​magnesium fluoride prepared in the comparative document CN106669742A is only greater than 130m 2 / g (as shown in Table 2). Compared with the preparation results of the reference documents, the tubular magnesium fluoride prepared in the present invention has a large specific surface area, more catalytic active sites, and better catalytic effect. The preparation method of the present invention provides a solution to the current problem of small specific surface area of ​​magnesium fluoride. The prepared tubular magnesium fluoride has good catalytic performance in catalytic reactions such as dehydrochlorination reaction, fluorine-chlorine exchange reaction, hydrogenation reaction, and removal of nitrogen oxides, especially dehydrochlorination reaction. Under the catalytic action of the tubular magnesium fluoride, the gas conversion rate can reach 59.82%.

[0090] The above is only an embodiment of the present invention, and the common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag, characterized in that: The steps include: S1: The overhaul slag produced by electrolytic aluminum is crushed, ground, and sieved, and then dissolved in water to maintain a solid-liquid ratio of the overhaul slag to the aqueous solution at 1:5-20. The solid-liquid mixture is placed in a water bath at 60-80°C for 1-2 hours, and the solid-liquid mixture after the water bath is filtered to obtain a solution containing sodium fluoride and aluminum ions; S2: Dissolve 5 mmol of chelating agent and 5 mmol of magnesium salt in water, mix well, react for 10-30 min, and then clarify the solution with 1 mol / L ammonia water. S3: Under ultrasonic conditions, 10 to 30 mL of the solution containing sodium fluoride and aluminum ions obtained in step S1 is added dropwise to the clear solution obtained in step S2; S4: transferring the solution obtained in step S3 to a reactor, performing a hydrothermal reaction in the temperature range of 100-200° C. for 1-2 hours, waiting for the reactor to naturally cool to room temperature, collecting the precipitate generated in the reactor by centrifugation, and washing it three times with deionized water and once with anhydrous ethanol; S5: The material obtained after centrifugation is placed in an oven at 60°C for drying and then ground to obtain aluminum-doped magnesium fluoride; S6: calcining the magnesium fluoride treated in step S5 in a tubular furnace at 400-600° C. for 2-4 hours to obtain a hollow tubular magnesium fluoride.

2. The method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag according to claim 1, characterized in that: The sieve used to sieve the overhaul slag in step S1 is a 100-mesh sieve.

3. The method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag according to claim 1, characterized in that: The chelating agent in step S2 is one of ethylenediaminetetraacetic acid sodium salt, sodium citrate, and sodium tartrate.

4. The method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag according to claim 3, characterized in that: The magnesium salt is one of magnesium sulfate, magnesium chloride and magnesium acetate.

5. The method for preparing aluminum-doped tubular magnesium fluoride using electrolytic aluminum overhaul slag according to claim 4, characterized in that: The filling degree of the reactor with the solution obtained in step S3 is 70%.

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