A method for recycling and preparing high-purity magnesium fluoride from fluorine-containing solid waste

Abstract

The present invention provides a method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste, comprising: mixing the fluorine-containing solid waste with magnesium sulfate and then performing a wet ball milling process, putting the obtained wet-milled conversion residue into a sodium hydroxide solution for alkali leaching and then filtering to obtain an alkali-leached conversion residue and an alkali-leached conversion solution; performing acid leaching on the alkali-leached conversion residue to obtain an acid leached solution, performing a magnesium ultrasonic extraction process on the acid leached solution, and performing a magnesium ultrasonic back extraction process on the obtained magnesium-loaded organic phase to obtain a magnesium-free organic phase and a magnesium sulfate solution; acidifying the alkali-leached conversion solution and then filtering to obtain an acidified solution, performing a fluorine extraction process on the acidified solution to obtain a fluorine-loaded organic phase, and using the magnesium sulfate solution as an anti-extraction agent to perform a fluorine back extraction process on the fluorine-loaded organic phase to obtain magnesium fluoride. The method adopted by the present invention can efficiently separate calcium and magnesium in the fluorine-containing solid waste, convert the fluorides in the fluorine-containing solid waste into high-purity magnesium fluoride, and realize the recycling of fluorine and magnesium resources in the fluorine-containing solid waste.

Description

Technical Field

[0001] The present invention belongs to the fields of resource recycling and environmental protection, and particularly relates to a method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste. Background Art

[0002] The implementation of the "dual carbon" policy has promoted the rapid development of the new energy vehicle industry. However, the scrapping volume of lithium batteries, which are the core power source, has also increased year by year. The huge volume and potential pollution have driven the lithium battery recycling industry into a stage of great development. During the pyrolysis recovery process of lithium batteries, alkaline liquids are usually used to adsorb the generated flue gas and gases, thus generating a large amount of fluorine-containing solid waste. At present, fluorine-containing solid waste is generally stacked in place, which not only occupies a large amount of land resources, emits a foul smell and pollutes the air, but also allows harmful substances to leach into the soil with rainwater and pollute groundwater. At the same time, fluorine-containing solid waste contains a large amount of fluorides and has great recycling value. It is very necessary and urgent to harmlessly treat and resourcefully utilize fluorine-containing solid waste.

[0003] At present, the research on the recycling of fluorine-containing solid waste mostly focuses on recovering substances such as gypsum, quartz, calcium chloride, and calcium fluoride from fluorine-containing solid waste. Calcium fluoride and magnesium fluoride coexist in fluorine-containing solid waste, and it is difficult to separate calcium and magnesium in the solid phase, making it difficult to separate and purify calcium fluoride and magnesium fluoride in fluorine-containing solid waste. Moreover, the technology for efficiently separating calcium and magnesium in fluorine-containing solid waste and converting fluorides into high-purity magnesium fluoride and purifying it is still in a blank stage.

[0004] Therefore, how to efficiently separate calcium and magnesium in fluorine-containing solid waste and convert the fluorides in fluorine-containing solid waste into high-purity magnesium fluoride to realize the recycling of fluorine and magnesium resources in fluorine-containing solid waste is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that there are few research reports on recovering high-purity magnesium fluoride from fluorine-containing solid waste in the prior art, which makes it impossible to efficiently separate calcium and magnesium in fluorine-containing solid waste, and the fluorine and magnesium resources in fluorine-containing solid waste cannot be fully utilized, resulting in waste of resources and other technical problems.

[0006] To solve the above problems, the present invention provides a method for recycling and preparing high-purity magnesium fluoride from fluorine-containing solid waste. The method includes: mixing the fluorine-containing solid waste with magnesium sulfate and then performing a wet ball milling process to obtain a wet mill conversion residue and a wet mill conversion liquid, and recycling the wet mill conversion liquid to the wet ball milling process; putting the wet mill conversion residue into a sodium hydroxide solution for alkali leaching and then filtering to obtain an alkali leaching conversion residue and an alkali leaching conversion liquid; performing acid leaching on the alkali leaching conversion residue with sulfuric acid and then filtering to obtain an acid leaching solution, performing a magnesium ultrasonic extraction process on the acid leaching solution with an organic composite extractant and a first diluent to obtain a magnesium raffinate and a magnesium-loaded organic phase, performing a magnesium ultrasonic back-extraction process on the magnesium-loaded organic phase with a back-extraction agent to obtain a magnesium-free organic phase and a magnesium sulfate solution, and recycling the magnesium-free organic phase to the magnesium ultrasonic extraction process; acidifying the alkali leaching conversion liquid with sulfuric acid and then filtering to obtain an acidified solution, performing a fluorine extraction process on the acidified solution with an organic phosphorus extractant and a second diluent to obtain a fluorine raffinate and a fluorine-loaded organic phase, performing a fluorine back-extraction process on the fluorine-loaded organic phase with the magnesium sulfate solution obtained by the magnesium ultrasonic back-extraction process as the back-extraction agent to obtain an acid-containing tail liquid, magnesium fluoride and a fluorine-free organic phase, recycling the acid-containing tail liquid to the magnesium ultrasonic back-extraction process, and recycling the fluorine-free organic phase to the fluorine extraction process.

[0007] As a further technical solution of the present invention, in the alkali leaching process of putting the wet mill conversion residue into a sodium hydroxide solution, the addition amount of sodium hydroxide in the sodium hydroxide solution is 1.5 - 2.0 times of the first theoretical molar ratio, and the first theoretical molar ratio is the molar ratio required for the reaction of sodium hydroxide with the fluoride in the fluorine-containing solid waste. The leaching time of the alkali leaching is 30 - 150 min, the leaching temperature is 60 - 90 °C, the leaching liquid-solid ratio is 8 - 14, and the stirring speed is 200 - 800 r / min.

[0008] As a further technical solution of the present invention, in the wet ball milling process, the wet milling liquid for wet ball milling is distilled water, the liquid-solid ratio is 0.5 - 2, the ball-to-material ratio is 6:1 - 10:1, the ball milling time is 30 - 120 min, and the addition amount of magnesium sulfate is 1.1 - 1.5 times of the second theoretical molar ratio, and the second theoretical molar ratio is the molar ratio required for the reaction of magnesium sulfate with the fluoride in the fluorine-containing solid waste.

[0009] As a further technical solution of the present invention, in the acid leaching process of performing acid leaching on the alkali leaching conversion residue with sulfuric acid, the addition amount of sulfuric acid is 1.5 - 2.0 times of the third theoretical molar ratio, and the third theoretical molar ratio is the molar ratio required for the reaction of sulfuric acid with the hydroxide in the alkali leaching conversion residue. The acid leaching time is 30 - 150 min, the acid leaching temperature is 25 - 50 °C, and the stirring speed is 400 - 800 r / min.

[0010] As a further technical solution of the present invention, in the magnesium ultrasonic extraction process, the first diluent is sulfonated kerosene, the volume ratio of the sulfonated kerosene to the organic composite extractant is 1:1 - 2:1, the extraction O / A ratio is 1:2 - 1:4, the extraction temperature is 20 - 40 °C, the ultrasonic frequency is 20 - 35 KHZ, the ultrasonic extraction time is 3 - 5 min, the extraction stage number is 2 - 5, the organic composite extractant includes dinonylnaphthalenesulfonic acid, diisooctyl phosphate and n-decanol, and the volume ratio of the dinonylnaphthalenesulfonic acid, the diisooctyl phosphate and the n-decanol is 75:15:10.

[0011] As a further technical solution of the present invention, in the magnesium ultrasonic stripping process, the stripping agent is sulfuric acid with a concentration of 1.5 - 3.5 mol / L, the stripping O / A ratio is 4:1 - 1:1, the stripping temperature is 20 - 40 °C, the ultrasonic frequency is 20 - 35 KHZ, the ultrasonic extraction time is 3 - 5 min, and the stripping stage number is 2 - 5.

[0012] As a further technical solution of the present invention, the pH of the acidifying solution is 1 - 5.

[0013] As a further technical solution of the present invention, in the fluorine extraction process, the volume ratio of the organophosphorus extractant to the second diluent is 0.5:1 - 2:1, the extraction O / A ratio is 1:1 - 1:4, the extraction temperature is 25 - 55 °C, the extraction time is 15 - 75 min, and the extraction stage number is 2 - 5.

[0014] As a further technical solution of the present invention, in the fluorine extraction process, the organophosphorus extractant includes monoester phosphate, diester phosphate or triester phosphate, and the second diluent includes silicate ester or polyorganosiloxane.

[0015] As a further technical solution of the present invention, in the fluorine stripping process, the stripping O / A ratio is 4:1 - 1:1, the stripping temperature is 25 - 55 °C, the stripping time is 15 - 75 min, and the stripping stage number is 2 - 5.

[0016] Beneficial effects: The present invention provides a method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste. First, the fluorine-containing solid waste is mixed with magnesium sulfate and then subjected to a wet ball milling process to convert fluorides such as calcium fluoride in the fluorine-containing solid waste into magnesium fluoride, so that the wet-milled conversion residue mainly contains magnesium fluoride and calcium sulfate. Then, the wet-milled conversion residue is put into a sodium hydroxide solution for alkali leaching to efficiently separate fluorine and magnesium in the wet-milled conversion residue. The obtained alkali-leached conversion residue mainly contains magnesium hydroxide and calcium-containing compounds, and the alkali-leached conversion liquid mainly contains soluble fluorides. The alkali-leached conversion residue is subjected to sulfuric acid leaching and then filtered, so that magnesium hydroxide is converted into soluble magnesium sulfate and enters the acid leaching solution, and the solid obtained after filtration mainly contains calcium-containing compounds, thereby efficiently separating magnesium and calcium. Then, the acid leaching solution is successively subjected to a magnesium ultrasonic extraction process and a magnesium ultrasonic back-extraction process to purify magnesium sulfate in the acid leaching solution to obtain a pure magnesium sulfate solution. The alkali-leached conversion liquid is successively subjected to acidification, a fluorine extraction process, and a fluorine back-extraction process using the magnesium sulfate solution obtained by the magnesium ultrasonic back-extraction process as an anti-extraction agent, so that the purified magnesium sulfate solution purifies fluorine in the alkali-leached conversion liquid to obtain high-purity magnesium fluoride. The process of the present invention is simple, has low energy consumption, little pollution, and the prepared magnesium fluoride product has high purity, realizing the efficient separation of calcium and magnesium in the fluorine-containing solid waste and the high-quality conversion and purification of all fluorides into magnesium fluoride. In addition, by recycling the wet-milled conversion liquid, the empty magnesium organic phase, the acid-containing tail liquid, and the empty fluorine organic phase, the amount of waste liquid generated in the process is greatly reduced, reducing pollution. The present invention can efficiently recycle magnesium and fluorine in the fluorine-containing solid waste, not only solving the safety problems and ecological hidden dangers existing in the fluorine-containing solid waste, but also realizing the sustainable utilization of resources. Brief Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present specification or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 is the flow chart of the method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste in the embodiment of the present invention Figure 1 ;

[0019] Figure 2 is the flow chart of the method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste in the embodiment of the present invention Figure 2 。 Detailed Embodiments

[0020] The technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention belong to the scope of protection of the present invention.

[0021] Meanwhile, throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention pertains. In case of any contradiction, this specification shall prevail.

[0022] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0023] Example 1

[0024] As Figure 1 and Figure 2 shown, this first embodiment provides a method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste. The method includes: S101 Mixing the fluorine-containing solid waste with magnesium sulfate and then performing a wet ball milling process to obtain a wet-milled conversion residue and a wet-milled conversion liquid, and recycling the wet-milled conversion liquid to the wet ball milling process; S102 Placing the wet-milled conversion residue into a sodium hydroxide solution for alkali leaching and then filtering to obtain an alkali-leached conversion residue and an alkali-leached conversion liquid; S103 Acid-leaching the alkali-leached conversion residue with sulfuric acid and then filtering to obtain an acid-leached solution. Using an organic composite extractant and a first diluent to perform a magnesium ultrasonic extraction process on the acid-leached solution to obtain a magnesium raffinate and a magnesium-loaded organic phase. Using an anti-extraction agent to perform a magnesium ultrasonic anti-extraction process on the magnesium-loaded organic phase to obtain an empty magnesium organic phase and a magnesium sulfate solution, and recycling the empty magnesium organic phase to the magnesium ultrasonic extraction process; S104 Acidifying the alkali-leached conversion liquid with sulfuric acid and then filtering to obtain an acidified solution. Using an organic phosphorus extractant and a second diluent to perform a fluorine extraction process on the acidified solution to obtain a fluorine raffinate and a fluorine-loaded organic phase. Using the magnesium sulfate solution obtained from the magnesium ultrasonic anti-extraction process as an anti-extraction agent to perform a fluorine anti-extraction process on the fluorine-loaded organic phase to obtain an acid-containing tail liquid, magnesium fluoride, and an empty fluorine organic phase. Recycling the acid-containing tail liquid to the magnesium ultrasonic anti-extraction process and recycling the empty fluorine organic phase to the fluorine extraction process.

[0025] The present invention provides a method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste. First, the fluorine-containing solid waste is mixed with magnesium sulfate and then subjected to a wet ball milling process to convert fluorides in the fluorine-containing solid waste, such as calcium fluoride, into magnesium fluoride, so that the wet grinding conversion residue mainly contains magnesium fluoride and calcium sulfate. Then, the wet grinding conversion residue is put into a sodium hydroxide solution for alkali leaching to efficiently separate fluorine and magnesium in the wet grinding conversion residue. The alkali leaching conversion residue mainly contains magnesium hydroxide and calcium-containing compounds (such as calcium sulfate), and the alkali leaching conversion solution mainly contains soluble fluorides. The alkali leaching conversion residue is subjected to sulfuric acid leaching and then filtered, so that magnesium hydroxide is converted into soluble magnesium sulfate and enters the acid leaching solution, and the solid obtained after filtration mainly contains calcium-containing compounds (such as calcium sulfate), thereby efficiently separating magnesium and calcium. Then, the acid leaching solution is successively subjected to a magnesium ultrasonic extraction process and a magnesium ultrasonic back-extraction process to purify magnesium sulfate in the acid leaching solution to obtain a pure magnesium sulfate solution. The alkali leaching conversion solution is successively subjected to acidification, a fluorine extraction process, and a fluorine back-extraction process using the magnesium sulfate solution obtained by the magnesium ultrasonic back-extraction process as an anti-extraction agent, so that the purified magnesium sulfate solution purifies fluorine in the alkali leaching conversion solution to obtain high-purity magnesium fluoride. The process of the present invention is simple, has low energy consumption, little pollution, and the prepared magnesium fluoride product has high purity, realizing the efficient separation of calcium and magnesium in the fluorine-containing solid waste and the high-quality conversion and purification of all fluorides into magnesium fluoride. In addition, by recycling the wet grinding conversion solution, the empty magnesium organic phase, the acid-containing tail liquid, and the empty fluorine organic phase, the amount of waste liquid generated in the process is greatly reduced, reducing pollution. The present invention can efficiently recover and utilize magnesium and fluorine in the fluorine-containing solid waste, not only solving the safety problems and ecological hidden dangers existing in the fluorine-containing solid waste, but also realizing the sustainable utilization of resources. The prepared high-purity magnesium fluoride can be widely used in strategic emerging industries such as high-end equipment manufacturing, new energy, and electronic information.

[0026] In some possible embodiments, in the alkali leaching process of putting the wet grinding conversion residue into a sodium hydroxide solution, the addition amount of sodium hydroxide in the sodium hydroxide solution is 1.5 - 2.0 times the first theoretical molar ratio, and the first theoretical molar ratio is the molar ratio required for the reaction of sodium hydroxide with fluorides in the fluorine-containing solid waste. The leaching time of the alkali leaching is 30 - 150 min, the leaching temperature is 60 - 90 °C, the leaching liquid-solid ratio is 8 - 14, and the stirring speed is 200 - 800 r / min.

[0027] It should be noted that the content of fluorides in the fluorine-containing solid waste can be detected by those skilled in the art by using existing instruments or methods, and will not be elaborated in detail here.

[0028] In addition, in this embodiment, the addition amount of sodium hydroxide in the sodium hydroxide solution is 1.5 - 2.0 times the first theoretical molar ratio. This is because by adding an excessive amount of sodium hydroxide and adopting appropriate alkali leaching conditions, the fluorine in the wet-milled conversion residue can be fully leached into the alkali leaching conversion solution, so that fluorine and magnesium can be efficiently separated.

[0029] In some possible implementation manners, in the wet ball milling process, the wet milling liquid for wet ball milling is distilled water, the liquid-solid ratio is 0.5 - 2, the ball-to-material ratio is 6:1 - 10:1, the ball milling time is 30 - 120 min, the addition amount of magnesium sulfate is 1.1 - 1.5 times the second theoretical molar ratio, and the second theoretical molar ratio is the molar ratio required for the reaction of magnesium sulfate with the fluoride in the fluorine-containing solid waste.

[0030] Those skilled in the art can understand that by using distilled water as the wet milling liquid for wet ball milling, adding an excessive amount of magnesium sulfate and adopting appropriate wet milling conditions, high-quality conversion of all fluorides in the fluorine-containing solid waste into magnesium fluoride can be achieved.

[0031] In some possible implementation manners, in the acid leaching of the alkali leaching conversion residue with sulfuric acid, the addition amount of sulfuric acid is 1.5 - 2.0 times the third theoretical molar ratio, and the third theoretical molar ratio is the molar ratio required for the reaction of sulfuric acid with the hydroxide in the alkali leaching conversion residue. The acid leaching time is 30 - 150 min, the acid leaching temperature is 25 - 50 °C, and the stirring speed is 400 - 800 r / min.

[0032] It should be noted that those skilled in the art can detect and calculate the content of hydroxide in the alkali leaching conversion residue by using existing instruments or methods, and details are not described here.

[0033] In addition, in this embodiment, the addition amount of sulfuric acid in the acid leaching of the alkali leaching conversion residue with sulfuric acid is 1.5 - 2.0 times the third theoretical molar ratio. This is because by adding an excessive amount of sulfuric acid and adopting appropriate acid leaching conditions, the hydroxide in the alkali leaching conversion residue can react with sulfuric acid to form soluble magnesium sulfate and enter the acid leaching solution, and the solid obtained after acid leaching filtration mainly contains calcium-containing compounds (such as calcium sulfate), thereby achieving efficient separation of magnesium and calcium.

[0034] In some possible embodiments, in the magnesium ultrasonic extraction process, the first diluent is sulfonated kerosene, the volume ratio of the sulfonated kerosene to the organic composite extractant is 1:1 - 2:1, the extraction O / A ratio is 1:2 - 1:4, the extraction temperature is 20 - 40 °C, the ultrasonic frequency is 20 - 35 KHZ, the ultrasonic extraction time is 3 - 5 min, the number of extraction stages is 2 - 5, the organic composite extractant includes dinonylnaphthalenesulfonic acid, diisooctyl phosphate and n-decanol, and the volume ratio of the dinonylnaphthalenesulfonic acid, the diisooctyl phosphate and the n-decanol is 75:15:10.

[0035] Those skilled in the art can understand that by using dinonylnaphthalenesulfonic acid, diisooctyl phosphate and n-decanol as the organic composite extractant, it can selectively combine with the extracted magnesium metal ions; by using sulfonated kerosene as the first diluent, which has a low specific gravity and belongs to an inert solvent, it can be used to adjust the extractant concentration, reduce the viscosity and specific gravity of the organic phase, and is conducive to phase separation; by the volume ratio of the sulfonated kerosene to the organic composite extractant being 1:1 - 2:1, the extraction O / A ratio being 1:2 - 1:4, the extraction temperature being 20 - 40 °C, the ultrasonic frequency being 20 - 35 KHZ, the ultrasonic extraction time being 3 - 5 min, the number of extraction stages being 2 - 5, and the volume ratio of the dinonylnaphthalenesulfonic acid, the diisooctyl phosphate and the n-decanol being 75:15:10, the extraction efficiency can be improved to obtain a magnesium-loaded organic phase.

[0036] In some possible embodiments, in the magnesium ultrasonic stripping process, the stripping agent is sulfuric acid with a concentration of 1.5 - 3.5 mol / L, the stripping O / A ratio is 4:1 - 1:1, the stripping temperature is 20 - 40 °C, the ultrasonic frequency is 20 - 35 KHZ, the ultrasonic extraction time is 3 - 5 min, and the number of stripping stages is 2 - 5.

[0037] This is because, through the multi-stage stripping method with the stripping agent being sulfuric acid with a concentration of 1.5 - 3.5 mol / L, the stripping O / A ratio being 4:1 - 1:1, the stripping temperature being 20 - 40 °C, the ultrasonic frequency being 20 - 35 KHZ, the ultrasonic extraction time being 3 - 5 min, and the number of stripping stages being 2 - 5, the stripping efficiency can be improved to obtain a high-purity magnesium sulfate solution.

[0038] In some possible embodiments, the pH of the acidified solution is 1 - 5.

[0039] Those skilled in the art can understand that after the alkali leaching conversion solution is acidified with sulfuric acid and filtered, the pH of the acidified solution is 1 - 5 to ensure that the acidity of the acidified solution is similar to the acidity required for the subsequent fluorine extraction process and fluorine stripping process, facilitating the subsequent extraction and stripping process for the acidified solution.

[0040] In some possible embodiments, in the fluorine extraction process, the volume ratio of the organophosphorus extractant to the second diluent is 0.5:1 - 2:1, the extraction O / A ratio is 1:1 - 1:4, the extraction temperature is 25 - 55 °C, the extraction time is 15 - 75 min, and the number of extraction stages is 2 - 5.

[0041] This is because through the multi-stage extraction process with the volume ratio of the organophosphorus extractant to the second diluent being 0.5:1 - 2:1, the extraction O / A ratio being 1:1 - 1:4, the extraction temperature being 25 - 55 °C, the extraction time being 15 - 75 min, and the number of extraction stages being 2 - 5, the extraction efficiency can be improved to obtain a fluorine-loaded organic phase.

[0042] In some possible embodiments, in the fluorine extraction process, the organophosphorus extractant includes monoalkyl phosphate, dialkyl phosphate, or trialkyl phosphate, and the second diluent includes silicate ester or polyorganosiloxane.

[0043] This is because by using monoalkyl phosphate, dialkyl phosphate, or trialkyl phosphate as the organophosphorus extractant, the fluoride ions in the acidified solution can be selectively extracted; by using silicate ester or polyorganosiloxane as the second diluent, the extraction performance of the extractant can be improved, the phase separation performance of the extractant can be improved, and the generation of the third phase and the consumption of the extractant can be reduced.

[0044] In some possible embodiments, in the fluorine stripping process, the stripping O / A ratio is 4:1 - 1:1, the stripping temperature is 25 - 55 °C, the stripping time is 15 - 75 min, and the number of stripping stages is 2 - 5.

[0045] Those skilled in the art can understand that through the multi-stage fluorine stripping process with the stripping O / A ratio being 4:1 - 1:1, the stripping temperature being 25 - 55 °C, the stripping time being 15 - 75 min, and the number of stripping stages being 2 - 5, the stripping efficiency can be improved to obtain high-purity magnesium fluoride.

[0046] To further elaborate on the technical solutions of the present application to support the technical problems to be solved by the present application, the following provides specific exemplary descriptions of the method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste, such as Examples 2 - 6.

[0047] Example 2

[0048] This example recovers and prepares high-purity magnesium fluoride from fluorine-containing solid waste through the following steps:

[0049] Mix the fluorine-containing solid waste with magnesium sulfate and then carry out the wet ball milling process to obtain wet milled conversion slag and wet milled conversion liquid, and recycle the wet milled conversion liquid to the wet ball milling process; the wet milling liquid for wet ball milling is distilled water, the liquid-solid ratio is 2, the ball-to-material ratio is 10:1, the ball milling time is 120 min, the addition amount of magnesium sulfate is 1.5 times the second theoretical molar ratio, and the second theoretical molar ratio is the molar ratio required for magnesium sulfate to react with the fluoride in the fluorine-containing solid waste;

[0050] Put the wet milled conversion slag into sodium hydroxide solution for alkali leaching and then filter to obtain alkali leached conversion slag and alkali leached conversion liquid; the addition amount of sodium hydroxide in the sodium hydroxide solution is 2.0 times the first theoretical molar ratio, and the first theoretical molar ratio is the molar ratio required for sodium hydroxide to react with the fluoride in the fluorine-containing solid waste. The leaching time for alkali leaching is 150 min, the leaching temperature is 80 °C, the leaching liquid-solid ratio is 12, and the stirring speed is 800 r / min;

[0051] Leach the alkali leached conversion slag with sulfuric acid and then filter to obtain the acid leaching solution. In the process of leaching the alkali leached conversion slag with sulfuric acid, the addition amount of sulfuric acid is 2.0 times the third theoretical molar ratio, and the third theoretical molar ratio is the molar ratio required for sulfuric acid to react with the hydroxide in the alkali leached conversion slag. The acid leaching time is 150 min, the acid leaching temperature is 40 °C, and the stirring speed is 800 r / min; carry out magnesium ultrasonic extraction process on the acid leaching solution with an organic composite extractant and a diluent to obtain magnesium raffinate and magnesium-loaded organic phase. In the magnesium ultrasonic extraction process, the diluent is sulfonated kerosene, the volume ratio of sulfonated kerosene to the organic composite extractant is 1.5:1, the extraction O / A ratio is 1:4, the extraction temperature is 30 °C, the ultrasonic frequency is 35 KHZ, the ultrasonic extraction time is 5 min, the extraction stage number is 5, and the organic composite extractant includes dinonylnaphthalene sulfonic acid, diisooctyl phosphate and n-decanol, and the volume ratio of dinonylnaphthalene sulfonic acid, diisooctyl phosphate and n-decanol is 75:15:10; carry out magnesium ultrasonic back extraction process on the magnesium-loaded organic phase with a back extractant to obtain magnesium-free organic phase and magnesium sulfate solution, and recycle the magnesium-free organic phase to the magnesium ultrasonic extraction process. In the magnesium ultrasonic back extraction process, the back extractant is sulfuric acid with a concentration of 3.5 mol / L, the back extraction O / A ratio is 4:1, the back extraction temperature is 30 °C, the ultrasonic frequency is 35 KHZ, the ultrasonic extraction time is 5 min, and the back extraction stage number is 5;

[0052] The alkali leaching conversion liquid is acidified with sulfuric acid and then filtered to obtain an acidified liquid with a pH of 3. The acidified liquid is subjected to a fluorine extraction process using an organophosphorus extractant and a diluent to obtain a fluorine raffinate and a fluorine-loaded organic phase. In the fluorine extraction process, the volume ratio of the organophosphorus extractant to the diluent is 1:1, the extraction O / A ratio is 1:4, the extraction temperature is 45°C, the extraction time is 75 min, the number of extraction stages is 5, the organophosphorus extractant is a monoester of phosphoric acid, and the diluent includes a silicate ester. The magnesium sulfate solution obtained by the magnesium ultrasonic back-extraction process is used as a back-extraction agent to perform a fluorine back-extraction process on the fluorine-loaded organic phase to obtain an acid-containing tail liquid, magnesium fluoride, and a fluorine-free organic phase. The acid-containing tail liquid is recycled to the magnesium ultrasonic back-extraction process, and the fluorine-free organic phase is recycled to the fluorine extraction process. In the fluorine back-extraction process, the back-extraction O / A ratio is 4:1, the back-extraction temperature is 40°C, the back-extraction time is 75 min, and the number of back-extraction stages is 5.

[0053] In this example, the recovery rate of magnesium is 98.4%, the recovery rate of fluorine is 95.3%, and the purity of MgF2 is 99.5%.

[0054] Example 3

[0055] This example recovers and prepares high-purity magnesium fluoride from fluorine-containing solid waste through the following steps:

[0056] The fluorine-containing solid waste is mixed with magnesium sulfate and then subjected to a wet ball milling process to obtain a wet-milled conversion residue and a wet-milled conversion liquid, and the wet-milled conversion liquid is recycled to the wet ball milling process; the wet-milling liquid for wet ball milling is distilled water, the liquid-solid ratio is 0.5, the ball-to-material ratio is 6:1, the ball milling time is 30, the addition amount of magnesium sulfate is 1.1 times the second theoretical molar ratio, and the second theoretical molar ratio is the molar ratio required for magnesium sulfate to react with the fluoride in the fluorine-containing solid waste;

[0057] The wet-milled conversion residue is put into a sodium hydroxide solution for alkali leaching and then filtered to obtain an alkali-leached conversion residue and an alkali-leached conversion liquid; the addition amount of sodium hydroxide in the sodium hydroxide solution is 1.5 times the first theoretical molar ratio, and the first theoretical molar ratio is the molar ratio required for sodium hydroxide to react with the fluoride in the fluorine-containing solid waste. The leaching time for alkali leaching is 30 min, the leaching temperature is 60°C, the leaching liquid-solid ratio is 8, and the stirring speed is 200 r / min;

[0058] The alkali leaching conversion residue is acid leached with sulfuric acid and then filtered to obtain an acid leaching solution. In the acid leaching of the alkali leaching conversion residue with sulfuric acid, the addition amount of sulfuric acid is 1.5 times the third theoretical molar ratio, and the third theoretical molar ratio is the molar ratio required for sulfuric acid to react with hydroxides in the alkali leaching conversion residue. The acid leaching time is 30 min, the acid leaching temperature is 25 °C, and the stirring speed is 400 r / min. The acid leaching solution is subjected to a magnesium ultrasonic extraction process using an organic composite extractant and a diluent to obtain a magnesium raffinate and a magnesium-loaded organic phase. In the magnesium ultrasonic extraction process, the diluent is sulfonated kerosene, the volume ratio of the sulfonated kerosene to the organic composite extractant is 1:1, the extraction O / A ratio is 1:2, the extraction temperature is 20 °C, the ultrasonic frequency is 20 KHz, the ultrasonic extraction time is 3 min, and the extraction stage number is 2. The organic composite extractant includes dinonylnaphthalenesulfonic acid, diisooctyl phosphate, and n-decanol, and the volume ratio of the dinonylnaphthalenesulfonic acid, the diisooctyl phosphate, and the n-decanol is 75:15:10. The magnesium-loaded organic phase is subjected to a magnesium ultrasonic stripping process using a stripping agent to obtain an empty magnesium organic phase and a magnesium sulfate solution. The empty magnesium organic phase is recycled to the magnesium ultrasonic extraction process. In the magnesium ultrasonic stripping process, the stripping agent is sulfuric acid with a concentration of 1.5 mol / L, the stripping O / A ratio is 1:1, the stripping temperature is 20 °C, the ultrasonic frequency is 20 KHz, the ultrasonic stripping time is 3 min, and the stripping stage number is 3.

[0059] The alkali leaching conversion solution is acidified with sulfuric acid and then filtered to obtain an acidified solution with a pH of 5. The acidified solution is subjected to a fluorine extraction process using an organophosphorus extractant and a diluent to obtain a fluorine raffinate and a fluorine-loaded organic phase. In the fluorine extraction process, the volume ratio of the organophosphorus extractant to the diluent is 0.5:1, the extraction O / A ratio is 1:1, the extraction temperature is 25 °C, the extraction time is 15 min, and the extraction stage number is 2. The organophosphorus extractant is phosphodiester, and the diluent is polyorganosiloxane. The magnesium sulfate solution obtained by the magnesium ultrasonic stripping process is used as a stripping agent to perform a fluorine stripping process on the fluorine-loaded organic phase to obtain an acid-containing tail liquid, magnesium fluoride, and an empty fluorine organic phase. The acid-containing tail liquid is recycled to the magnesium ultrasonic stripping process, and the empty fluorine organic phase is recycled to the fluorine extraction process. In the fluorine stripping process, the stripping O / A ratio is 1:1, the stripping temperature is 25 °C, the stripping time is 15 min, and the stripping stage number is 2.

[0060] In this example, the recovery rate of magnesium is 82.4%, the recovery rate of fluorine is 79.3%, and the purity of MgF2 is 88.7%.

[0061] Example 4

[0062] In this embodiment, high-purity magnesium fluoride is recovered and prepared from fluorine-containing solid waste through the following steps:

[0063] Mix the fluorine-containing solid waste with magnesium sulfate and perform a wet ball milling process to obtain a wet milled conversion residue and a wet milled conversion liquid, and recycle the wet milled conversion liquid to the wet ball milling process; the wet milling liquid for wet ball milling is distilled water, the liquid-solid ratio is 1, the ball-to-material ratio is 8:1, the ball milling time is 90 min, the addition amount of the magnesium sulfate is 1.3 times the second theoretical molar ratio, and the second theoretical molar ratio is the molar ratio required for the reaction of the magnesium sulfate with the fluoride in the fluorine-containing solid waste;

[0064] Put the wet milled conversion residue into a sodium hydroxide solution for alkali leaching and then filter to obtain an alkali leached conversion residue and an alkali leached conversion liquid; the addition amount of sodium hydroxide in the sodium hydroxide solution is 1.6 times the first theoretical molar ratio, and the first theoretical molar ratio is the molar ratio required for the reaction of the sodium hydroxide with the fluoride in the fluorine-containing solid waste. The leaching time for alkali leaching is 60 min, the leaching temperature is 90 °C, the leaching liquid-solid ratio is 10, and the stirring speed is 400 r / min;

[0065] Leach the alkali leached conversion residue with sulfuric acid and then filter to obtain an acid leaching solution. In the process of leaching the alkali leached conversion residue with sulfuric acid, the addition amount of the sulfuric acid is 1.7 times the third theoretical molar ratio, and the third theoretical molar ratio is the molar ratio required for the reaction of the sulfuric acid with the hydroxide in the alkali leached conversion residue. The acid leaching time is 120 min, the acid leaching temperature is 35 °C, and the stirring speed is 600 r / min; perform a magnesium ultrasonic extraction process on the acid leaching solution with an organic composite extractant and a diluent to obtain a magnesium raffinate and a magnesium-loaded organic phase. In the magnesium ultrasonic extraction process, the diluent is sulfonated kerosene, the volume ratio of the sulfonated kerosene to the organic composite extractant is 2:1, the extraction O / A ratio is 1:3, the extraction temperature is 30 °C, the ultrasonic frequency is 30 KHz, the ultrasonic extraction time is 4 min, the extraction stage number is 4, the organic composite extractant includes dinonylnaphthalene sulfonic acid, diisooctyl phosphate, and n-decanol, and the volume ratio of the dinonylnaphthalene sulfonic acid, the diisooctyl phosphate, and the n-decanol is 75:15:10; perform a magnesium ultrasonic back extraction process on the magnesium-loaded organic phase with a back extractant to obtain an empty magnesium organic phase and a magnesium sulfate solution, and recycle the empty magnesium organic phase to the magnesium ultrasonic extraction process. In the magnesium ultrasonic back extraction process, the back extractant is sulfuric acid with a concentration of 2.5 mol / L, the back extraction O / A ratio is 2:1, the back extraction temperature is 30 °C, the ultrasonic frequency is 30 KHz, the ultrasonic extraction time is 4 min, and the back extraction stage number is 4;

[0066] The alkali leaching conversion solution is acidified with sulfuric acid and then filtered to obtain an acidified solution with a pH of 2. The acidified solution is subjected to a fluorine extraction process using an organophosphorus extractant and a diluent to obtain a fluorine raffinate and a fluorine-loaded organic phase. In the fluorine extraction process, the volume ratio of the organophosphorus extractant to the diluent is 2:1, the extraction O / A ratio is 1:4, the extraction temperature is 35 °C, the extraction time is 30 min, the number of extraction stages is 3. The organophosphorus extractant is a triphosphate ester, and the diluent is a silicate ester. The magnesium sulfate solution obtained by the magnesium ultrasonic stripping process is used as a stripping agent to perform a fluorine stripping process on the fluorine-loaded organic phase to obtain an acid-containing tail liquid, magnesium fluoride, and an empty fluorine-loaded organic phase. The acid-containing tail liquid is recycled to the magnesium ultrasonic stripping process, and the empty fluorine-loaded organic phase is recycled to the fluorine extraction process. In the fluorine stripping process, the stripping O / A ratio is 2:1, the stripping temperature is 35 °C, the stripping time is 35 min, and the number of stripping stages is 5.

[0067] In this example, the recovery rate of magnesium is 94.6%, the recovery rate of fluorine is 93.7%, and the purity of MgF2 is 99.3%.

[0068] Example 5

[0069] This example recovers and prepares high-purity magnesium fluoride from fluorine-containing solid waste through the following steps:

[0070] The fluorine-containing solid waste is mixed with magnesium sulfate and then subjected to a wet ball milling process to obtain a wet milled conversion residue and a wet milled conversion solution. The wet milled conversion solution is recycled to the wet ball milling process. The wet milling liquid for wet ball milling is distilled water, the liquid-solid ratio is 1.5, the ball-to-material ratio is 9:1, the ball milling time is 100 min, and the addition amount of magnesium sulfate is 1.4 times the second theoretical molar ratio. The second theoretical molar ratio is the molar ratio required for magnesium sulfate to react with the fluoride in the fluorine-containing solid waste.

[0071] The wet milled conversion residue is put into a sodium hydroxide solution for alkali leaching and then filtered to obtain an alkali leached conversion residue and an alkali leached conversion solution. The addition amount of sodium hydroxide in the sodium hydroxide solution is 2.0 times the first theoretical molar ratio. The first theoretical molar ratio is the molar ratio required for sodium hydroxide to react with the fluoride in the fluorine-containing solid waste. The leaching time for alkali leaching is 120 min, the leaching temperature is 80 °C, the leaching liquid-solid ratio is 10, and the stirring speed is 600 r / min.

[0072] The alkali leaching conversion residue is leached with sulfuric acid and then filtered to obtain a leaching solution. In the process of leaching the alkali leaching conversion residue with sulfuric acid, the addition amount of sulfuric acid is 2.0 times the third theoretical molar ratio, and the third theoretical molar ratio is the molar ratio required for sulfuric acid to react with the hydroxide in the alkali leaching conversion residue. The leaching time is 90 min, the leaching temperature is 50 °C, and the stirring speed is 600 r / min. The magnesium ultrasonic extraction process is carried out on the leaching solution with an organic composite extractant and a diluent to obtain a magnesium raffinate and a magnesium-loaded organic phase. In the magnesium ultrasonic extraction process, the diluent is sulfonated kerosene, and the volume ratio of the sulfonated kerosene to the organic composite extractant is 2:1. The extraction O / A ratio is 1:3, the extraction temperature is 30 °C, the ultrasonic frequency is 30 KHZ, the ultrasonic extraction time is 5 min, and the extraction stage number is 5. The organic composite extractant includes dinonylnaphthalenesulfonic acid, diisooctyl phosphate, and n-decanol, and the volume ratio of dinonylnaphthalenesulfonic acid, diisooctyl phosphate, and n-decanol is 75:15:10. The magnesium ultrasonic stripping process is carried out on the magnesium-loaded organic phase with a stripping agent to obtain an empty magnesium organic phase and a magnesium sulfate solution, and the empty magnesium organic phase is recycled to the magnesium ultrasonic extraction process. In the magnesium ultrasonic stripping process, the stripping agent is sulfuric acid with a concentration of 2.5 mol / L, the stripping O / A ratio is 2:1, the stripping temperature is 30 °C, the ultrasonic frequency is 30 KHZ, the ultrasonic extraction time is 5 min, and the stripping stage number is 4.

[0073] The alkali leaching conversion solution is acidified with sulfuric acid and then filtered to obtain an acidified solution, and the pH of the acidified solution is 1. The fluoride extraction process is carried out on the acidified solution with an organic phosphorus extractant and a diluent to obtain a fluoride raffinate and a fluoride-loaded organic phase. In the fluoride extraction process, the volume ratio of the organic phosphorus extractant to the diluent is 1:1, the extraction O / A ratio is 1:3, the extraction temperature is 45 °C, the extraction time is 55 min, and the extraction stage number is 5. The organic phosphorus extractant is a monoester of phosphoric acid, and the diluent is a silicate ester. The fluoride stripping process is carried out on the fluoride-loaded organic phase with the magnesium sulfate solution obtained by the magnesium ultrasonic stripping process as a stripping agent to obtain an acid-containing tail liquid, magnesium fluoride, and an empty fluoride organic phase. The acid-containing tail liquid is recycled to the magnesium ultrasonic stripping process, and the empty fluoride organic phase is recycled to the fluoride extraction process. In the fluoride stripping process, the stripping O / A ratio is 2:1, the stripping temperature is 35 °C, the stripping time is 35 min, and the stripping stage number is 4.

[0074] In this example, the recovery rate of magnesium is 96.4%, the recovery rate of fluoride is 94.3%, and the purity of MgF2 is 99.1%.

[0075] Example 6

[0076] In this embodiment, high-purity magnesium fluoride is recovered and prepared from fluorine-containing solid waste through the following steps:

[0077] Mix the fluorine-containing solid waste with magnesium sulfate and carry out a wet ball milling process to obtain wet milled conversion slag and wet milled conversion liquid, and recycle the wet milled conversion liquid to the wet ball milling process; the wet milling liquid for wet ball milling is distilled water, the liquid-solid ratio is 2, the ball-to-material ratio is 8:1, the ball milling time is 90 min, the addition amount of the magnesium sulfate is 1.4 times the second theoretical molar ratio, and the second theoretical molar ratio is the molar ratio required for the reaction of the magnesium sulfate with the fluoride in the fluorine-containing solid waste;

[0078] Put the wet milled conversion slag into a sodium hydroxide solution for alkali leaching and then filter to obtain alkali leached conversion slag and alkali leached conversion liquid; the addition amount of sodium hydroxide in the sodium hydroxide solution is 1.7 times the first theoretical molar ratio, and the first theoretical molar ratio is the molar ratio required for the reaction of the sodium hydroxide with the fluoride in the fluorine-containing solid waste. The leaching time for alkali leaching is 120 min, the leaching temperature is 80 °C, the leaching liquid-solid ratio is 10, and the stirring speed is 800 r / min;

[0079] Leach the alkali leached conversion slag with sulfuric acid and then filter to obtain an acid leaching solution. In the process of leaching the alkali leached conversion slag with sulfuric acid, the addition amount of the sulfuric acid is 2.0 times the third theoretical molar ratio, and the third theoretical molar ratio is the molar ratio required for the reaction of the sulfuric acid with the hydroxide in the alkali leached conversion slag. The acid leaching time is 90 min, the acid leaching temperature is 50 °C, and the stirring speed is 800 r / min; Carry out a magnesium ultrasonic extraction process on the acid leaching solution with an organic composite extractant and a diluent to obtain a magnesium raffinate and a magnesium-loaded organic phase. In the magnesium ultrasonic extraction process, the diluent is sulfonated kerosene, the volume ratio of the sulfonated kerosene to the organic composite extractant is 1.5:1, the extraction O / A ratio is 1:4, the extraction temperature is 30 °C, the ultrasonic frequency is 30 KHz, the ultrasonic extraction time is 5 min, the extraction stage number is 5, the organic composite extractant includes dinonylnaphthalene sulfonic acid, diisooctyl phosphate, and n-decanol, and the volume ratio of the dinonylnaphthalene sulfonic acid, the diisooctyl phosphate, and the n-decanol is 75:15:10; Carry out a magnesium ultrasonic back extraction process on the magnesium-loaded organic phase with a back extractant to obtain an empty magnesium organic phase and a magnesium sulfate solution, and recycle the empty magnesium organic phase to the magnesium ultrasonic extraction process. In the magnesium ultrasonic back extraction process, the back extractant is sulfuric acid with a concentration of 3.5 mol / L, the back extraction O / A ratio is 3:1, the back extraction temperature is 30 °C, the ultrasonic frequency is 35 KHz, the ultrasonic extraction time is 5 min, and the back extraction stage number is 4;

[0080] The alkali leaching conversion solution is acidified with sulfuric acid and then filtered to obtain an acidified solution with a pH of 5. An organic phosphorus extractant and a diluent are used to perform a fluorine extraction process on the acidified solution to obtain a fluorine raffinate and a fluorine-loaded organic phase. In the fluorine extraction process, the volume ratio of the organic phosphorus extractant to the diluent is 2:1, the extraction O / A ratio is 1:2, the extraction temperature is 55°C, the extraction time is 75 min, and the number of extraction stages is 3. The organic phosphorus extractant is a triphosphate ester, and the diluent is a silicate ester. The magnesium sulfate solution obtained by the magnesium ultrasonic stripping process is used as a stripping agent to perform a fluorine stripping process on the fluorine-loaded organic phase to obtain an acid-containing tail liquid, magnesium fluoride, and a fluorine-free organic phase. The acid-containing tail liquid is recycled to the magnesium ultrasonic stripping process, and the fluorine-free organic phase is recycled to the fluorine extraction process. In the fluorine stripping process, the stripping O / A ratio is 2:1, the stripping temperature is 35°C, the stripping time is 35 min, and the number of stripping stages is 4.

[0081] In this example, the recovery rate of magnesium is 92.8%, the recovery rate of fluorine is 90.7%, and the purity of MgF2 is 89.6%.

[0082] Finally, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0083] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0084] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste, characterized in that, The method includes: Mixing the fluorine-containing solid waste with magnesium sulfate and then performing a wet ball milling process to obtain a wet-milled conversion residue and a wet-milled conversion liquid, and recycling the wet-milled conversion liquid to the wet ball milling process; Putting the wet-milled conversion residue into a sodium hydroxide solution for alkali leaching and then filtering to obtain an alkali-leached conversion residue and an alkali-leached conversion liquid; in the process of putting the wet-milled conversion residue into the sodium hydroxide solution for alkali leaching, the addition amount of sodium hydroxide in the sodium hydroxide solution is 1.5 - 2.0 times of the first theoretical molar ratio, the first theoretical molar ratio is the molar ratio required for the reaction of sodium hydroxide with the fluoride in the fluorine-containing solid waste, the leaching time of the alkali leaching is 30 - 150 min, the leaching temperature is 60 - 90 °C, the liquid-solid ratio of the leaching solution is 8 - 14, and the stirring speed is 200 - 800 r / min; Leaching the alkali-leached conversion residue with sulfuric acid and then filtering to obtain an acid leaching solution, performing a magnesium ultrasonic extraction process on the acid leaching solution with an organic composite extractant and a first diluent to obtain a magnesium raffinate and a magnesium-loaded organic phase, performing a magnesium ultrasonic stripping process on the magnesium-loaded organic phase with a stripping agent to obtain an empty magnesium organic phase and a magnesium sulfate solution, and recycling the empty magnesium organic phase to the magnesium ultrasonic extraction process; Acidifying the alkali-leached conversion liquid with sulfuric acid and then filtering to obtain an acidified solution, performing a fluorine extraction process on the acidified solution with an organophosphorus extractant and a second diluent to obtain a fluorine raffinate and a fluorine-loaded organic phase, using the magnesium sulfate solution obtained by the magnesium ultrasonic stripping process as a stripping agent to perform a fluorine stripping process on the fluorine-loaded organic phase to obtain an acid-containing tail liquid, magnesium fluoride and an empty fluorine organic phase, recycling the acid-containing tail liquid to the magnesium ultrasonic stripping process, and recycling the empty fluorine organic phase to the fluorine extraction process.

2. The method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste according to claim 1, wherein: In the wet ball milling process, the wet milling liquid for wet ball milling is distilled water, the liquid-solid ratio is 0.5 - 2, the ball-to-material ratio is 6:1 - 10:1, the ball milling time is 30 - 120 min, and the addition amount of magnesium sulfate is 1.1 - 1.5 times of the second theoretical molar ratio, and the second theoretical molar ratio is the molar ratio required for the reaction of magnesium sulfate with the fluoride in the fluorine-containing solid waste.

3. The method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste according to claim 2, wherein: In the process of leaching the alkali-leached conversion residue with sulfuric acid, the addition amount of sulfuric acid is 1.5 - 2.0 times of the third theoretical molar ratio, the third theoretical molar ratio is the molar ratio required for the reaction of sulfuric acid with the hydroxide in the alkali-leached conversion residue, the acid leaching time is 30 - 150 min, the acid leaching temperature is 25 - 50 °C, and the stirring speed is 400 - 800 r / min.

4. The method for recovering and preparing high-purity magnesium fluoride from fluorine-containing solid waste according to claim 3, wherein: In the magnesium ultrasonic extraction process, the first diluent is sulfonated kerosene, and the volume ratio of the sulfonated kerosene to the organic composite extractant is 1:1 - 2:

1. The extraction O / A ratio is 1:2 - 1:4, the extraction temperature is 20 - 40°C, the ultrasonic frequency is 20 - 35 KHZ, the ultrasonic extraction time is 3 - 5 min, the extraction stage number is 2 - 5. The organic composite extractant includes dinonylnaphthalene sulfonic acid, diisooctyl phosphate and n-decanol, and the volume ratio of the dinonylnaphthalene sulfonic acid, the diisooctyl phosphate and the n-decanol is 75:15:

10.

5. The method for recycling and preparing high-purity magnesium fluoride from fluorine-containing solid waste according to claim 4, characterized in that: In the magnesium ultrasonic stripping process, the stripping agent is sulfuric acid with a concentration of 1.5 - 3.5 mol / L, the stripping O / A ratio is 4:1 - 1:1, the stripping temperature is 20 - 40°C, the ultrasonic frequency is 20 - 35 KHZ, the ultrasonic extraction time is 3 - 5 min, and the stripping stage number is 2 - 5.

6. The method for recycling and preparing high-purity magnesium fluoride from fluorine-containing solid waste according to claim 5, characterized in that: The pH of the acidifying solution is 1 - 5.

7. The method for recycling and preparing high-purity magnesium fluoride from fluorine-containing solid waste according to claim 6, characterized in that: In the fluorine extraction process, the volume ratio of the organophosphorus extractant to the second diluent is 0.5:1 - 2:1, the extraction O / A ratio is 1:1 - 1:4, the extraction temperature is 25 - 55°C, the extraction time is 15 - 75 min, and the extraction stage number is 2 - 5.

8. The method for recycling and preparing high-purity magnesium fluoride from fluorine-containing solid waste according to claim 7, characterized in that: In the fluorine extraction process, the organophosphorus extractant includes monoester phosphate, diester phosphate or triester phosphate, and the second diluent includes silicate ester or polyorganosiloxane.

9. The method for recycling and preparing high-purity magnesium fluoride from fluorine-containing solid waste according to claim 8, characterized in that: In the fluorine stripping process, the stripping O / A ratio is 4:1 - 1:1, the stripping temperature is 25 - 55°C, the stripping time is 15 - 75 min, and the stripping stage number is 2 - 5.

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