Method for preparing hydroxyl aluminum fluoride and aluminum fluoride from fluorine-containing waste

Abstract

The invention provides a method for preparing aluminum hydroxyl fluoride and aluminum fluoride from fluorine-containing waste, and relates to the technical field of solid waste resource utilization. According to the method, the fluorine-containing waste is leached through the aluminum chloride-diluted hydrochloric acid mixed solution, acid-insoluble impurities are removed through solid-liquid separation, the pH value of the leaching solution is adjusted to 3.5-6, the pH value is the generation end point of aluminum hydroxyfluoride, the fluorine element is efficiently settled through aging, alkali-insoluble impurities are removed through solid-liquid separation, and the aluminum hydroxyfluoride is obtained. And washing the obtained aluminum hydroxyfluoride crude product with an aluminum chloride aqueous solution, dissolving a small amount of sodium salt in the solution, and removing the sodium salt through solid-liquid separation to obtain a pure aluminum hydroxyfluoride product. According to the method provided by the invention, the fluorine element in the fluorine-containing waste can be efficiently recycled, sodium-containing impurities are effectively removed, and the obtained aluminum hydroxyfluoride is high in purity. Moreover, the method provided by the invention is simple to operate and simple in process, and efficient resource utilization of the fluorine-containing waste is realized.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization, and in particular to a method for preparing hydroxyaluminum fluoride and aluminum fluoride by utilizing fluorine-containing waste materials. Background Art

[0002] The modern aluminum electrolysis process is mainly carried out in a modern electrolytic cell composed of alumina as the electrolytic raw material, cryolite as the electrolyte, and a carbon anode and cathode. The electrolyte plays the role of dissolving alumina and reducing it to produce metallic aluminum through electrolysis. In the process of industrial aluminum production, in order to control a certain molecular ratio of aluminum electrolyte, aluminum fluoride raw materials are continuously added to the aluminum electrolytic cell. With the continuous addition of aluminum fluoride, new cryolite is continuously produced during the aluminum electrolysis process, which is bound to cause a large amount of excess electrolyte. The main components of the excess electrolyte are Na3AlF6, AlF3, NaF, and CaF2. With the increase of aluminum production capacity, 40kg of fluorine-containing electrolyte is produced per ton of primary aluminum. my country's aluminum electrolysis industry produces an average of 1.4 million tons of fluorine-containing electrolyte per year. These materials can only be physically accumulated in space, and if they are not properly disposed of, they will also bring great pollution risks to the environment. These fluorine-containing materials are secondary resources that can be recycled and reused. How to effectively treat fluorine-containing waste electrolytes through appropriate processes is a problem that needs to be solved urgently.

[0003] At present, there is a certain research foundation for fluorine-containing waste electrolytes in China. For example, CN108754543A discloses a method for separating carbon residue from aluminum electrolyte, wherein an acid solution with a concentration of 1 mol / L is subjected to a neutralization reaction with carbon residue under stirring and heating conditions, and when the pH is less than 5 and the fluoride ion leaching rate is higher than 94%, the leaching is completed to obtain a leaching solution; the leaching solution is filtered to obtain a filter residue and a filtrate, and the filter residue is washed and dried to obtain a carbon residue product; a salt solution is added to the obtained filtrate to precipitate fluorine; the fluorine precipitation solution is filtered to obtain a filter residue and a filtrate, and the filter residue is washed and dried to obtain a basic aluminum fluoride product, and the obtained filtrate is used to prepare an acid solution. CN108728867A discloses a harmless separation method for waste cathode carbon blocks from aluminum electrolysis, which comprises crushing and screening waste cathode carbon blocks from aluminum electrolysis to obtain carbon block particles; placing the carbon block particles in an acid solution with a concentration of 1 mol / L for leaching under heating and stirring conditions to obtain a leaching solution, filtering the leaching solution to separate a filtrate and a filter residue, and washing and drying the filter residue to obtain a carbon powder product; adding a salt solution to the filtrate for fluorine precipitation to obtain a fluorine precipitation solution and filtering it to separate a filtrate and a filter cake, and washing and drying the filter cake to obtain a basic metal fluoride product. CN108677020A discloses a method for harmless and resourceful treatment of waste aluminum electrolytes, comprising the steps of electrolyzing waste aluminum, crushing and screening to obtain aluminum electrolyte particles; preparing an acid solution with a concentration of 1 mol / L and an aluminum salt solution with a concentration of 1 mol / L, placing the aluminum electrolyte particles in the prepared acid solution for leaching under heating and stirring conditions, controlling the solution pH to be less than 5, and ending the leaching when the fluoride ion leaching rate is higher than 94%, filtering impurities, and obtaining a leaching solution; adding the prepared aluminum salt solution to the obtained leaching solution, heating and stirring, and controlling the Al 3+ / Na + When the pH is greater than 0.3 and precipitation occurs in the solution, the solution is filtered to obtain a filter residue and a filtrate. The filter residue is washed and dried to obtain a basic aluminum fluoride product, and the obtained filtrate is evaporated and crystallized to obtain a sodium salt product. CN111690823A discloses a method for preparing aluminum fluoride for aluminum electrolytic cells, wherein the lithium-potassium-aluminum electrolyte leachate is added with alkali to adjust the pH, and the Al 3+ 、F - OH -The precipitation reaction is carried out in a certain proportion, the reaction temperature is 20-110°C, the reaction time is 20-120min, a certain amount of precipitation is obtained, and the obtained precipitation product is calcined at 350-650°C for 1-3h to obtain anhydrous aluminum fluoride. CN109759423A discloses a comprehensive utilization method of aluminum electrolytic carbon slag, the aluminum electrolytic waste carbon slag is crushed, screened and ball-milled, and then floated, using water glass as an inhibitor and kerosene as a capture agent to obtain carbon; the electrolyte discharged from the bottom flow of the flotation tank is filtered to obtain a filtrate; a mixed solution containing HNO3 and Al(NO3)3 is added to the filtrate, and the reaction is carried out at 60-65°C for 1-1.5h to obtain a solid-liquid mixture; the solid-liquid mixture is solid-liquid separated to obtain a filter residue, and the filter residue is leached with a high-concentration hydrofluoric acid solution, and solid-liquid separation is performed to obtain AlF3.

[0004] The above patents all use acid leaching, filtering and then adding salt solution to precipitate fluoride to recover fluoride ions. The obtained sodium salts are all soluble substances. Soluble sodium salts are difficult to completely remove as impurities. The national standards for most products require sodium content as an important restrictive indicator. Taking aluminum fluoride as an example, the national standard GBT-4292-2017 requires a minimum sodium content of less than 0.6%, and a better grade requires less than 0.3%. However, the sodium content in the basic aluminum fluoride prepared according to the experimental conditions of the above patents is high (3 to 7wt%), and the sodium removal effect is not good. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing hydroxyaluminum fluoride and aluminum fluoride using fluorine-containing waste materials. The sodium content in the hydroxyaluminum fluoride and aluminum fluoride prepared by the method provided by the present invention is less than 0.45wt%, and the sodium content is low.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing aluminum hydroxyfluoride by using fluorine-containing waste materials, comprising the following steps:

[0008] The fluorine-containing waste powder and the aluminum chloride-dilute hydrochloric acid mixed solution are first mixed, leached, and solid-liquid separated to obtain a leachate;

[0009] The pH value of the leaching solution is adjusted to 3.5-6, and the leaching solution is aged and solid-liquid separated to obtain a crude aluminum hydroxyfluoride product;

[0010] The crude hydroxyaluminum fluoride is mixed with an aqueous solution of aluminum chloride for a second time, and the solid and liquid are separated to obtain a pure hydroxyaluminum fluoride.

[0011] Preferably, the fluorine content in the fluorine-containing waste powder is ≥ 26wt%;

[0012] The pH value of the dilute hydrochloric acid in the aluminum chloride-dilute hydrochloric acid mixed solution is 1-2, and the concentration of aluminum chloride is 15-500 g / L;

[0013] The solid-to-liquid ratio of the fluorine-containing waste powder to the aluminum chloride-dilute hydrochloric acid mixed solution is 70-90g:1L.

[0014] Preferably, the leaching temperature is 40-90° C. and the leaching time is 1.5-3.5 h.

[0015] Preferably, the alkali solution used for adjusting the pH value includes a sodium hydroxide aqueous solution or a sodium aluminate aqueous solution; the alkali solution is added dropwise; and the temperature of the dropwise addition is 40 to 90°C.

[0016] Preferably, the aging temperature is 40-80° C. and the aging time is 30-60 min.

[0017] Preferably, the concentration of the aluminum chloride aqueous solution is 14 to 80 g / L.

[0018] Preferably, the temperature of the second mixing is 40-80° C., and the time is 30-60 min.

[0019] The present invention also provides a method for preparing aluminum fluoride using fluorine-containing waste materials, comprising the following steps: mixing the pure hydroxyaluminum fluoride obtained by the method described in the above technical scheme with a hydrofluoric acid aqueous solution, acidifying, separating the solid from the liquid, and calcining the obtained solid component to obtain aluminum fluoride.

[0020] Preferably, the mass concentration of the hydrofluoric acid aqueous solution is 18-32%;

[0021] The acidification temperature is 70-80° C. and the acidification time is 1-2.5 h.

[0022] Preferably, the calcination temperature is 750-950° C., and the holding time is 15-20 seconds.

[0023] The present invention first mixes fluorine-containing waste powder and aluminum chloride-dilute hydrochloric acid mixed solution, leaches and dissolves fluorine-containing waste, removes acid-insoluble impurities by solid-liquid separation, and obtains a leachate; the pH value of the leachate is adjusted to 3.5-6, which is the end point of hydroxyaluminum fluoride generation, and efficiently precipitates fluorine elements by aging, removes alkali-insoluble impurities by solid-liquid separation, and washes the obtained crude hydroxyaluminum fluoride (hydroxyaluminum fluoride and a small amount of sodium salt) with an aluminum chloride aqueous solution, dissolves a small amount of sodium salt in the solution, removes it by solid-liquid separation, and obtains pure hydroxyaluminum fluoride. The method provided by the present invention can efficiently recover fluorine elements in fluorine-containing waste, and effectively remove sodium-containing impurities, and the obtained hydroxyaluminum fluoride has high purity. Moreover, the method provided by the present invention is simple to operate and simple in process, and realizes efficient resource utilization of fluorine-containing waste.

[0024] The invention uses hydrofluoric acid solution to acidify pure hydroxyaluminum fluoride and then calcines it, so that the prepared aluminum fluoride has low sodium content, high aluminum fluoride purity and good fluidity. The indicators of the aluminum fluoride product are better than the quality of the current national standard dry-process aluminum fluoride product. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing aluminum fluoride using fluorine-containing waste materials, comprising the following steps:

[0026] The fluorine-containing waste powder and the aluminum chloride-dilute hydrochloric acid mixed solution are first mixed, leached, and solid-liquid separated to obtain a leachate;

[0027] The pH value of the leaching solution is adjusted to 3.5-6, and the leaching solution is aged and solid-liquid separated to obtain a crude aluminum hydroxyfluoride product;

[0028] The crude hydroxyaluminum fluoride is mixed with an aqueous solution of aluminum chloride for a second time, and the solid and liquid are separated to obtain a pure hydroxyaluminum fluoride.

[0029] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0030] The invention first mixes fluorine-containing waste powder and aluminum chloride-dilute hydrochloric acid mixed solution, performs leaching, and separates the solid and liquid to obtain a leaching solution.

[0031] In the present invention, the fluorine content in the fluorine-containing waste powder is preferably ≥26wt%, more preferably 26-50wt%, and in embodiments, it can be 26wt%, 30wt%, 35wt%, 40wt%, 45wt% or 50wt%. In the present invention, the fluorine-containing waste powder is preferably obtained by sieving the fluorine-containing waste after crushing, and the part under the sieve is the fluorine-containing waste powder; the sieve size of the sieving is preferably 120-230 mesh, and in specific embodiments, it can be 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh, 200 mesh, 210 mesh, 220 mesh or 230 mesh.

[0032] The present invention has no special limitation on the fluorine-containing waste. Fluorine-containing waste with a fluorine content of ≥26wt% known to those skilled in the art can be used, such as lithium-containing waste generated by one or more of aluminum-containing electrolytes, rare earths, metallurgy, glass and pharmaceuticals.

[0033] In the present invention, the pH value of the dilute hydrochloric acid in the aluminum chloride-dilute hydrochloric acid mixed solution is preferably 1-2, and in specific embodiments, it can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2; the concentration of aluminum chloride in the aluminum chloride-dilute hydrochloric acid mixed solution is preferably 15-500 g / L, and in specific embodiments, it can be 15 g / L, 50 g / L, 100 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L, 350 g / L, 400 g / L, 450 g / L or 500 g / L.

[0034] In the present invention, the solid-to-liquid ratio of the fluorine-containing waste powder to the aluminum chloride-dilute hydrochloric acid mixed solution is preferably 60-100 g:1L, and in specific embodiments it can be 60 g:1L, 65 g:1L, 70 g:1L, 75 g:1L, 80 g:1L, 85 g:1L, 90 g:1L, 95 g:1L or 100 g:1L.

[0035] In the present invention, the leaching temperature is preferably 40-90°C, and in specific embodiments it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C; the leaching time is preferably 1.5-3.5h, and in specific embodiments it can be 1.5h, 2h, 2.5h, 3h or 3.5h; the leaching is preferably carried out under stirring conditions.

[0036] The present invention has no special limitation on the solid-liquid separation, and any solid-liquid separation method well known to those skilled in the art may be used, such as filtration, suction filtration or centrifugal separation.

[0037] After obtaining the leaching solution, the present invention adjusts the pH value of the leaching solution to 3.5-6, performs aging, and performs solid-liquid separation to obtain a crude hydroxyaluminum fluoride product.

[0038] In the present invention, the alkali solution used for pH adjustment preferably includes sodium hydroxide aqueous solution or sodium aluminate aqueous solution; the concentration of the alkali solution is preferably 18-25wt%, and in a specific embodiment, the concentration of the alkali solution can be 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt% or 25wt%. In the present invention, the pH value is 3.5-6, and in a specific embodiment, it can be 3.5, 4, 4.5, 5, 5.5 or 6.

[0039] In the present invention, the alkali solution is added dropwise; the temperature of the dropwise addition is preferably 40-90°C, and in specific embodiments may be 40°C, 50°C, 60°C, 70°C, 80°C or 90°C; the dropwise addition is preferably carried out under stirring conditions.

[0040] In the present invention, the aging temperature is preferably 40-80°C, and in specific embodiments it can be 40°C, 50°C, 60°C, 70°C or 80°C; the aging time is preferably 30-60min, and in specific embodiments it can be 30min, 35min, 40min, 45min, 50min, 55min or 60min.

[0041] The present invention has no special limitation on the solid-liquid separation, and any solid-liquid separation method well known to those skilled in the art may be used, such as filtration, suction filtration or centrifugal separation.

[0042] After obtaining the crude hydroxyaluminum fluoride, the present invention secondly mixes the crude hydroxyaluminum fluoride with an aqueous solution of aluminum chloride, and separates the solid from the liquid to obtain pure hydroxyaluminum fluoride.

[0043] In the present invention, the mass concentration of the aluminum chloride aqueous solution is preferably 0.5-6%, more preferably 1-5%, further preferably 1.2-4%, specifically preferably 0.5%, 1%, 1.2%, 1.5%, 2%, 2.5%, 3%, 3.5%, 3.6%, 4%, 4.5% or 5%.

[0044] In the present invention, the temperature of the second mixing is preferably 40-80°C, and in specific embodiments it can be 40°C, 50°C, 60°C, 70°C or 80°C; the time of the second mixing is preferably 30-60 min, and in specific embodiments it can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0045] The present invention has no special limitation on the solid-liquid separation, and any solid-liquid separation method well known to those skilled in the art may be used, such as filtration, suction filtration or centrifugal separation.

[0046] After the solid-liquid separation is completed, the present invention preferably further comprises drying the solid component obtained by the solid-liquid separation to obtain pure aluminum hydroxyfluoride. In the present invention, the drying temperature is preferably 100-120°C, more preferably 110-115°C; the present invention has no special limitation on the drying time, and drying to constant weight is sufficient.

[0047] The present invention also provides a method for preparing aluminum fluoride using fluorine-containing waste materials, comprising the following steps: mixing the pure hydroxyaluminum fluoride obtained by the method described in the above technical scheme with a hydrofluoric acid aqueous solution, acidifying, separating the solid from the liquid, and calcining the obtained solid component to obtain aluminum fluoride.

[0048] In the present invention, the mass concentration of the hydrofluoric acid aqueous solution is preferably 18 to 32%, more preferably 20 to 30%, and further preferably 25 to 28%.

[0049] In the present invention, the pH value of the system during the acidification process is preferably 1.5-3, and can be 1.5, 2, 2.5 or 3 in a specific embodiment.

[0050] In the present invention, the acidification temperature is preferably 70-80°C, and in specific embodiments it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C; the acidification time is preferably 1-2.5h, and in specific embodiments it can be 1h, 1.5h, 2h or 2.5h.

[0051] The present invention has no special limitation on the solid-liquid separation, and any solid-liquid separation method well known to those skilled in the art may be used, such as filtration, suction filtration or centrifugal separation.

[0052] After the solid-liquid separation is completed, the present invention preferably further comprises drying the solid component to obtain aluminum fluoride containing crystalline water (eg, AIF3·3H2O). In the present invention, the drying temperature is preferably 110-115°C, and the drying is performed until constant weight.

[0053] In the present invention, the calcination temperature is preferably 750-950°C, and in specific embodiments it can be 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C or 950°C; the calcination time is preferably 15-20s (seconds), and in specific embodiments it can be 15s, 16s, 17s, 18s, 19s or 20s; the calcination atmosphere is preferably air.

[0054] After the calcination is completed, the present invention preferably further comprises granulating the obtained aluminum fluoride to obtain aluminum fluoride particles. In the present invention, the granulation preferably comprises granulation using a dry granulator.

[0055] The aluminum fluoride prepared by the present invention has the characteristics of high purity and good fluidity. The main content of aluminum fluoride in GB / T4292-2017 is less than 92%, and the aluminum fluoride content of the aluminum fluoride product is greater than 96%, which is better than the quality of the current national standard dry-process aluminum fluoride product.

[0056] In order to further illustrate the present invention, the method for preparing hydroxyaluminum fluoride and aluminum fluoride from fluorine-containing waste provided by the present invention is described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] The aluminum electrolyte waste slag is crushed and passed through a 150-mesh sieve. The sieve-less portion is fluorine-containing waste powder. The molar ratio of sodium fluoride to aluminum fluoride in the fluorine-containing waste powder is 2.9, CaF2 2.8wt%, MgF2 4.1wt%, KF 4.7wt%, LiF 6.7wt%, and Al2O3 3.2wt%.

[0059] Dilute hydrochloric acid with a pH of 1 was mixed with aluminum chloride, and stirred at 80° C. until dissolved to obtain an aluminum chloride-dilute hydrochloric acid mixed solution, wherein the aluminum chloride concentration was 250 g / L.

[0060] Add fluorine-containing waste powder to the aluminum chloride-dilute hydrochloric acid mixed solution, leaching for 2 hours at 80°C under stirring conditions, and filter to obtain a leachate. Add 20wt% sodium hydroxide aqueous solution to the leachate at 80°C under stirring conditions until the solution pH = 5.0, continue stirring for 1.5 hours, filter, wash the obtained solid component with 3.6wt% aluminum chloride aqueous solution at 80°C, filter, add the obtained solid component to 20wt% hydrofluoric acid aqueous solution at 80°C, acidify for 2 hours at 200r / min, add 20wt% hydrofluoric acid aqueous solution during the acidification process to control the system pH = 2, dry the obtained solid at 115°C, and obtain high-purity aluminum fluoride (chemical formula AlF3·3H2O) The chemical composition is shown in Table 1. Among them, the solid-liquid ratio of fluorine-containing waste powder to aluminum chloride-dilute hydrochloric acid mixed solution is 90g:1L.

[0061] Example 2

[0062] High-purity hydroxyaluminum fluoride was prepared according to the method of Example 1, which differed from Example 1 only in that: passing through a 120-mesh sieve, the pH value of dilute hydrochloric acid was 1.2, the concentration of aluminum chloride in the aluminum chloride-dilute hydrochloric acid mixed solution was 200 g / L, the solid-liquid ratio of the fluorine-containing waste powder to the aluminum chloride-dilute hydrochloric acid mixed solution was 70 g:1 L, the concentration of the aluminum chloride aqueous solution for washing was 1.2 wt%, filtered, the obtained solid component was added to a 20 wt% hydrofluoric acid aqueous solution at 80°C, acidified at 200 r / min for 2 h, 20 wt% hydrofluoric acid aqueous solution was added dropwise during the acidification process to control the system pH value to 2, the obtained solid was dried at 115°C to obtain high-purity aluminum fluoride, and the chemical composition of the high-purity aluminum fluoride is shown in Table 1. Among them, the solid-liquid ratio of the fluorine-containing waste powder to the aluminum chloride-dilute hydrochloric acid mixed solution was 90 g:1 L.

[0063] Example 3

[0064] High-purity aluminum hydroxyfluoride was prepared according to the method of Example 1, which differed from Example 1 only in that: passing through a 120-mesh sieve, the pH value of dilute hydrochloric acid was 2, the aluminum chloride concentration in the aluminum chloride-dilute hydrochloric acid mixed solution was 200 g / L, the solid-liquid ratio of the fluorine-containing waste powder to the aluminum chloride-dilute hydrochloric acid mixed solution was 70 g:1 L, stirring was continued for 1 h after adding sodium hydroxide aqueous solution, the concentration of the aluminum chloride aqueous solution for washing was 3 wt%, filtration was performed, the obtained solid component was added to a 20 wt% hydrofluoric acid aqueous solution at 80° C., acidified at 200 r / min for 2 h, 20 wt% hydrofluoric acid aqueous solution was added dropwise during the acidification process to control the system pH value to 2, the obtained solid was dried at 115° C. to obtain high-purity aluminum fluoride, and the chemical composition of the high-purity aluminum fluoride (chemical formula AlF3·3H2O) is shown in Table 1. Among them, the solid-liquid ratio of the fluorine-containing waste powder to the aluminum chloride-dilute hydrochloric acid mixed solution was 90 g:1 L.

[0065] Table 1 Main chemical components (wt%) of high purity aluminum fluoride prepared in Examples 1 to 3

[0066] Chemical Elements F Al Na Ca C <![CDATA[H2O]]> Example 1 51.95 24.5 0.35 0.053 0.036 23.111 Example 2 51.0 25.01 0.44 0.100 0.046 23.404 Example 3 51.3 24.8 0.40 0.090 0.040 23.37

[0067] As can be seen from Table 1, the sodium content in the high-purity aluminum fluoride prepared by the present invention is below 0.44wt%, the calcium content is below 0.1wt%, and the carbon content is below 0.046wt%. The sodium, calcium and carbon contents are low, and the aluminum fluoride has high purity.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing aluminum hydroxyfluoride using fluorine-containing waste materials, comprising the following steps: The fluorine-containing waste powder and the aluminum chloride-dilute hydrochloric acid mixed solution are first mixed, leached, and solid-liquid separated to obtain a leachate; The pH value of the leaching solution is adjusted to 3.5-6, and the leaching solution is aged and solid-liquid separated to obtain a crude aluminum hydroxyfluoride product; The crude hydroxyaluminum fluoride is mixed with an aqueous solution of aluminum chloride for a second time, and the solid and liquid are separated to obtain a pure hydroxyaluminum fluoride.

2. The method according to claim 1, characterized in that The fluorine content of the fluorine-containing waste powder is ≥ 26wt%; The pH value of the dilute hydrochloric acid in the aluminum chloride-dilute hydrochloric acid mixed solution is 1-2, and the concentration of aluminum chloride is 15-500 g / L; The solid-to-liquid ratio of the fluorine-containing waste powder to the aluminum chloride-dilute hydrochloric acid mixed solution is 70-90g:1L.

3. The method according to claim 1 or 2, characterized in that: The leaching temperature is 40-90° C. and the leaching time is 1.5-3.5 hours.

4. The method according to claim 1, characterized in that: The alkali solution used for adjusting the pH value includes a sodium hydroxide aqueous solution or a sodium aluminate aqueous solution; the alkali solution is added dropwise; and the temperature of the dropwise addition is 40 to 90°C.

5. The method according to claim 1 or 4, characterized in that: The aging temperature is 40-80° C. and the aging time is 30-60 min.

6. The method according to claim 1, characterized in that The concentration of the aluminum chloride aqueous solution is 14-80 g / L.

7. The method according to claim 1 or 6, characterized in that: The temperature of the second mixing is 40-80° C., and the time is 30-60 min.

8. A method for preparing aluminum fluoride using fluorine-containing waste materials, comprising the following steps: The pure aluminum hydroxyfluoride obtained by the method according to any one of claims 1 to 7 is mixed with a hydrofluoric acid aqueous solution, acidified, solid-liquid separated, and the obtained solid component is calcined to obtain aluminum fluoride.

9. The method according to claim 8, characterized in that The mass concentration of the hydrofluoric acid aqueous solution is 18-32%; The acidification temperature is 70-80° C. and the acidification time is 1-2.5 h.

10. The method according to claim 8, characterized in that The calcination temperature is 750-950° C., and the heat preservation time is 15-20 seconds.