Method for preparing high-purity calcium fluoride and calcium sulfate through fluorine-containing mixed acid resourceful treatment

Abstract

The invention discloses a method for preparing high-purity calcium fluoride and calcium sulfate through fluorine-containing mixed acid resourceful treatment, which comprises the following steps: (1) mixing fluorine-containing mixed acid with a halide solution, and filtering and separating after reaction to obtain fluosilicate precipitate and first filtrate; (2) adding an organic alkali into the first filtrate, carrying out reduced pressure distillation, introducing a distillate into a soluble calcium salt solution for reaction, and filtering and separating to obtain calcium fluoride precipitate, an organic alkali filtrate and a second filtrate; (3) adding a heavy metal precipitant into the second filtrate, adjusting the system to an alkaline condition for reaction, and filtering and separating to obtain a heavy metal precipitate and a third filtrate; (4) reacting the third filtrate with a calcium chloride solution, and filtering and separating to obtain calcium sulfate precipitate and fourth filtrate; and (5) adding sodium hydroxide into the fourth filtrate, reacting, separating, and recovering to obtain organic alkali and sodium chloride. According to the method, resource utilization of elements such as fluorine, calcium and sulfur is achieved, and the purity of products such as calcium fluoride and calcium sulfate is not lower than 99%.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, specifically to a method for the resource-based treatment of fluorine-containing mixed acids to prepare high-purity calcium fluoride and calcium sulfate. Background Technology

[0002] Fluorinated mixed acids are widely produced in industrial processes such as semiconductor etching, electroplating, and photovoltaic cleaning. They combine the strong corrosiveness of hydrofluoric acid with the acidity of other inorganic acids. Fluoride ions can easily cause excessive fluoride in water bodies, soil calcification, and corrosion of equipment and pipelines.

[0003] Traditional neutralization precipitation methods have drawbacks such as incomplete fluoride removal and large amounts of sludge. They are difficult to achieve zero emissions in terms of recycling or resource recovery, cannot meet stringent environmental standards, and result in resource waste. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-purity calcium fluoride and calcium sulfate by resource-based treatment of fluorine-containing mixed acid with high purity and removal of heavy metal ions.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-purity calcium fluoride and calcium sulfate through resource-based treatment of fluorine-containing mixed acid, comprising the following steps:

[0006] (1) Mix the fluorinated mixed acid with the halide solution, react and then filter to separate, to obtain fluorosilicate precipitate and first filtrate;

[0007] (2) Add an organic base to the first filtrate, perform vacuum distillation, pass the distillate into a soluble calcium salt solution for reaction, and after filtration and separation, obtain high-purity calcium fluoride precipitate, organic base filtrate and second filtrate; the organic base can be recycled;

[0008] (3) Add a heavy metal precipitant to the second filtrate, adjust the system to alkaline conditions, react, filter and separate to obtain heavy metal precipitate and third filtrate;

[0009] (4) The third filtrate was reacted with calcium chloride solution, and after filtration, calcium sulfate precipitate and the fourth filtrate were obtained;

[0010] (5) Add sodium hydroxide to the fourth filtrate and react to separate it to recover the organic base and sodium chloride; the organic base and sodium chloride can be recycled.

[0011] Preferably, in step (1), the halide is one of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), or calcium chloride (CaCl2).

[0012] Preferably, in step (1), the reaction temperature is 25~40℃ and the reaction time is 0.5~1.5h.

[0013] Preferably, in step (1), the fluorinated mixed acid includes hydrofluoric acid (HF), fluorosilicic acid (H2SiF6), sulfuric acid (H2SO4), hydrochloric acid (HCl) and metal cations; the fluorinated mixed acid needs to be pretreated and the acidity is 1~3 mol / L.

[0014] Preferably, in step (2), the soluble calcium salt is one of calcium chloride (CaCl2), calcium nitrate (Ca(NO3)2), calcium dihydrogen phosphate (Ca(H2PO4)2), calcium bicarbonate (Ca(HCO3)2), calcium bisulfite (Ca(HSO3)2), calcium hypochlorite (Ca(ClO)2), calcium bromide (CaBr2), calcium iodide (CaI2), calcium chlorate (Ca(ClO3)2), calcium perchlorate (Ca(ClO4)2), and calcium permanganate (Ca(MnO4)2).

[0015] Preferably, in step (2), the organic base is one of pyridine, pyridine compounds, quinoline, or isoquinoline organic bases.

[0016] Preferably, the pyridine compound is one of methylpyridine, dimethylpyridine, pyrazine, pyrimidine, and pyridazine.

[0017] Preferably, in step (2), the specific process of vacuum distillation is as follows: the temperature is controlled at 40~50℃, the pressure is controlled at 20~40 kPa, and the reaction time is 1~2h.

[0018] Preferably, the heavy metal precipitant is one of soluble sulfides, dithiocarbamate compounds, and xanthate compounds.

[0019] Preferably, in step (3), the third filtrate is an organic alkaline solution.

[0020] Preferably, in step (3), the alkaline condition is a pH value of 6 to 8.

[0021] Compared with existing technologies, the advantages of this invention are as follows: First, a fluorinated mixed acid is reacted with a halide solution at room temperature to separate fluorosilicate precipitates. Then, an organic base is added to the filtrate, followed by vacuum distillation. The distilled gas is passed through a soluble metal chloride to obtain high-purity calcium fluoride, and the organic base filtrate can be reused. Heavy metal ions are removed using sulfide-based reagents assisted by an organic base. The distillation mother liquor reacts with calcium chloride to obtain high-purity calcium sulfate and pyridine hydrochloride filtrate. The organic base and sodium chloride obtained after processing the filtrate can be reused at the upstream end. The prepared products, calcium fluoride and calcium sulfate, have a purity of not less than 99%, possessing both environmental and economic value. Attached Figure Description

[0022] Figure 1 This is a flowchart of the preparation method in Example 1 of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] The fluorinated mixed acid was taken from etching waste liquid of a photovoltaic silicon wafer. Its composition (mass fraction) was analyzed as follows: HF 12.0%, H₂SO₄ 25.0%, H₂SiF 68.5%, Fe 3+ 0.8%, Cu 2+ 0.3% of the total, 2% of the total heavy metals, and the remainder is water; the NaCl solution concentration is 36.0 g / 100 mL; the purity of pyridine is ≥99.0%; Na2S, NaOH, and CaCl2 are all industrial grade (purity ≥98.0%).

[0026] S1: Fluorosilicate precipitation separation

[0027] 100 parts of the above-mentioned fluorinated mixed acid were placed in a stirrer-equipped perfluoroalkoxy (PFA) reactor. Under constant temperature of 25°C, 10 parts of saturated NaCl solution were slowly added dropwise at a rate of 2 mL / min. After the addition was complete, the reaction was continued with stirring for 0.5 h. After the reaction was completed, the solution was filtered through a PP filter cloth to obtain the precipitate Na₂SiF₆ and the first filtrate. The dry weight of the precipitate Na₂SiF₆ was 10.1 g, with a purity of 97.4%. The volume of the first filtrate was approximately 100 parts, and it was found to contain 7.2% HF and 14.5% H₂SO₄.

[0028] S2: Preparation and decomposition of pyridine hydrofluoric acid salt

[0029] The first filtrate was transferred to a PFA reactor, and 45 parts of pyridine were slowly added at room temperature. The stirring rate was 300 r / min, and the reaction was carried out for 0.5 hours. The vacuum distillation system was started, and the distillation temperature was controlled at 40℃ and the pressure at 20 kPa. Distillation was continued for 1 hour. The distillate was collected using a PFA condenser and absorbed by passing it through a 15% CaCl2 solution (120 parts by mass) with stirring for 0.5 hours. After filtration, CaF2 precipitate and pyridine solution were obtained. The CaF2 precipitate weighed 20.1 g after washing and drying, with a purity of 99.2%. The pyridine content in the pyridine solution was 27.5 parts, with a recovery rate of 92.2%. The pyridine solution was reused in this step. The mother liquor after distillation was solution 2, with a volume of approximately 110 parts.

[0030] S3: Heavy metal ion removal

[0031] Add 5 parts of Na2S solution to the second filtrate in three portions, 20 min apart, stirring to dissolve each time. Adjust the pH to 6.0 with 30% NaOH solution and maintain the reaction at 25°C with stirring for 1 hour. After the reaction, filter to obtain heavy metal filter cake precipitate (mainly Fe2S3, CuS, etc.) and the third filtrate. The dry weight of the heavy metal filter cake precipitate was 2.3 g, and the heavy metal removal rate was ≥99.0%. The third filtrate had a volume of 107 parts and contained SO42-. 2- The mass fraction is approximately 18.6%.

[0032] S4: Preparation of high-purity calcium sulfate

[0033] The third filtrate was transferred to a PP reactor and heated to 40°C. Saturated CaCl2 solution (16 parts) was slowly added, and the mixture was stirred for 1 hour. The mixture was then filtered to separate CaSO4 precipitate and the fourth filtrate. The CaSO4 precipitate, after washing and drying, was high-purity calcium sulfate with a dry weight of 23.1 g and a purity of 99.6%, meeting the industrial-grade high-purity CaSO4 standard. The fourth filtrate (98 parts) mainly consisted of pyridine hydrochloride (approximately 18.3% by mass).

[0034] S5: Pyridine and sodium chloride recovery and reuse

[0035] Add 18 parts of 30% NaOH solution to the fourth filtrate, stir and react for 1.0 h, then start the vacuum distillation system, controlling the temperature at 65℃ and the pressure at 15 kPa, and perform distillation separation. Collect pyridine as the distillate, and the amount detected is 10 parts, with a recovery rate of 94.0%, which is reused in step S2. Cool the distillation residue to room temperature and crystallize it, then filter to obtain solid NaCl with a dry weight of 8.2 g and a purity of 98.5%, which is reused in step S1.

[0036] Ultimately, the fluorine recovery rate of the fluorine-containing mixed acid was 93.5%, the sulfate conversion rate was 98.0%, the total pyridine recovery rate was 93.1%, and the sodium chloride recovery rate was 92.7%, achieving the resource utilization of the fluorine-containing mixed acid without secondary pollution emissions.

[0037] Example 2

[0038] The fluorinated mixed acid was taken from polishing waste liquid of an aluminum profile. Analysis showed its composition (mass fraction) to be: HF 18.0%, H₂SO₄ 20.0%, H₂SiF₆ 12.0%, Al 3+ 1.2%, Zn 2+0.5%, the remainder is water, density 1.40 g / mL; saturated NaCl solution concentration is 36.2 g / 100 mL; dimethylpyridine purity ≥ 99.0%; Na2S, NaOH, and CaCl2 are all industrial grade (purity ≥ 98.0%).

[0039] S1: Fluorosilicate precipitation separation

[0040] Take 100 parts of the above-mentioned fluorinated mixed acid (actual mass 100g) and place it in a PFA reactor equipped with a stirrer. Under constant temperature of 40℃, slowly add 20 parts of saturated NaCl solution at a dropping rate of 3 mL / min. After the addition is complete, stir the reaction for 1.5 h. Filter to obtain the precipitate Na2SiF6 and the first filtrate; the dry weight of the precipitate Na2SiF6 is 26.8g, with a purity of 98.2%; the volume of the first solution is approximately 110 parts, containing approximately 16.8% HF and approximately 18% H2SO4.

[0041] S2: Preparation and decomposition of dimethylpyridine hydrofluoric acid salt

[0042] The first filtrate was transferred to a PFA reactor, and 50 parts of dimethylpyridine were slowly added at room temperature. The mixture was stirred at 350 r / min for 2.0 h. A vacuum distillation system was started, controlling the distillation temperature at 48℃ and the pressure at 20 kPa, and distillation was continued for 2.0 h. The distillate was collected using a PFA condenser and passed through a 20% CaCl2 solution (200 parts by mass) for absorption. The absorption was stirred for 0.5 h, followed by filtration to obtain 15.7 g of CaF2 precipitate with a purity of 99.0%. The dimethylpyridine solution contained 31.8 parts of pyridine, with a recovery rate of 93.6%, which was reused in this step. The mother liquor from the distillation was the second filtrate, with a volume of 120 parts.

[0043] S3: Heavy metal ion removal

[0044] Eight parts of Na₂S solution were added to the second filtrate in four portions, 15 minutes apart. After stirring and dissolving, the pH was adjusted to 8 with 30% NaOH solution, and the reaction was carried out at 25°C for 2.0 h. Filtration yielded a heavy metal filter cake precipitate (mainly Al₂S₃ and ZnS) and a third filtrate. The dry weight of the heavy metal filter cake precipitate was 4.1 g, with a heavy metal removal rate ≥99.2%. The third filtrate contained approximately 118 parts of SO₄²⁻. 2- The mass fraction is approximately 15.2%.

[0045] S4: Preparation of high-purity calcium sulfate

[0046] The third filtrate was transferred to a PFA reactor and heated to 45°C. A saturated CaCl2 solution (90 parts) was slowly added, and the mixture was stirred for 2.0 hours. The mixture was then filtered to separate the CaSO4 precipitate and the fourth filtrate. The CaSO4 precipitate, after washing and drying, was high-purity CaSO4 with a dry weight of 25.8 g and a purity of 99.5%. The fourth filtrate (193 parts) mainly consisted of dimethylpyridine hydrochloride, with a mass fraction of approximately 22%.

[0047] S5: Pyridine and sodium chloride recovery and reuse

[0048] Add 28 parts of 30% sodium hydroxide solution to the fourth filtrate. After reacting for 1.0 h, start the vacuum distillation system, control the temperature at 70℃ and the pressure at 15 kPa, and perform distillation separation. Collect 13.7 parts of dimethylpyridine from the distillate, with a recovery rate of 91.0%, and reuse it in step S2. Cool the distillation residue to room temperature and crystallize it. Filter to obtain NaCl solid with a dry weight of 7.7 g and a purity of 98.3%, which is reused in step S1.

[0049] Ultimately, the fluorine recovery rate of the fluorine-containing mixed acid was 92.8%, the sulfate conversion rate was 94.5%, the total pyridine recovery rate was 90.3%, and the sodium chloride recovery rate was 91.7%. It is suitable for the treatment of mixed acids with high fluorine content and multiple metals, and achieves efficient recovery of fluorine and sulfur resources.

[0050] Comparative Example 1

[0051] This comparative example uses the traditional lime milk direct neutralization process to treat fluoride-containing mixed acid.

[0052] The fluorinated mixed acid is completely identical to that in Example 1: the components (mass fraction) are HF 12.0%, H2SO4 25.0%, H2SiF 68.5%, Fe 3+ 0.8%, Cu 2+ 0.3%, total heavy metals 2%, the remainder is water; the 30% NaOH solution, lime milk (Ca(OH)2 content ≥95.0%), and Na2S are all industrial grade (purity ≥98.0%).

[0053] S1: Neutralization and precipitation

[0054] 100 parts by mass of the above-mentioned fluorinated mixed acid were placed in a stirred PFA reactor, and lime slurry was slowly added dropwise under constant temperature of 25℃. The amount of Ca(OH)2 added was calculated based on the initial acidity theory (approximately 50 parts are needed to neutralize all HF, H2SO4, and H2SiF6), and the actual amount used was 35 parts (approximately 0.7 times the theoretical value). The dropping rate was 2 mL / min, and the reaction was continued with stirring for 2.0 h after the addition was complete. After the reaction was completed, the mixture was filtered to obtain a mixed precipitate (mainly containing CaF2, CaSO4, and metal hydroxides, etc.) and a first filtrate. The dry weight of the mixed precipitate was 48.5 g, with a purity of only 82.3%; the volume of the first filtrate was approximately 120 parts, and it was found to contain 1.8% HF and SO42-. 2- The quality fraction is approximately 5.2%.

[0055] S2: Heavy metal ion removal

[0056] Five parts of Na₂S solution were added to the first filtrate in three portions. The pH of the system was adjusted to 6.0 with NaOH solution. The mixture was stirred at 25°C for 1 hour and then filtered. A heavy metal sulfide filter cake (dry weight 2.2 g, mainly FeS and CuS) and a second filtrate were obtained. The volume of the second filtrate was 118 parts, containing SO₄²⁻. 2- The mass fraction was approximately 4.8%, and the heavy metal removal rate was 98.5%.

[0057] S3: Deep Neutralization Treatment

[0058] Lime slurry was added dropwise to the second filtrate to adjust the pH to 7.5-8.0. After stirring for 1.0 h, the mixture was filtered to obtain a small amount of secondary precipitate (dry weight 3.2 g, purity 85.1%) and the final neutralized residue. 115 portions of the residue were analyzed, and the mass fraction of fluoride ions was 0.3%, and SO42- was [not specified]. 2- The mass fraction is 2.1%, and further advanced treatment is required before it can be discharged.

[0059] A comprehensive comparison of the process effects of Example 1 and Comparative Example 1 is shown in Table 1:

[0060] Table 1. Comprehensive comparison of process effects between Example 1 and Comparative Example 1

[0061] The traditional lime slurry neutralization process used in the comparison has obvious shortcomings:

[0062] Low resource recovery efficiency: Due to incomplete neutralization (the actual amount of Ca(OH)2 added is less than the theoretical value) and complex precipitation forms, the resource recovery rates of fluorine and sulfate are only 84.2% and 88.5%, respectively, which are significantly lower than those of the patented process (93.5% and 98.0%).

[0063] The product has no utilization value: the obtained precipitate is a mixed waste residue with complex composition and low purity (≤85.1%), which cannot be used as an industrial product and can only be disposed of as hazardous waste, which is in stark contrast to the high-purity CaF2 (99.2%) and CaSO4 (99.6%) obtained by this invention.

[0064] There are issues of secondary pollution and cost: the final residual liquid still contains excessive levels of sulfur. - and SO4 2- This process requires additional handling; moreover, all processing reagents (such as Ca(OH)2 and Na2S) are consumed only once, with no recycling, resulting in high processing costs and failing to meet the principles of a green circular economy. In summary, the process of this invention, through stepwise precipitation, pyridine medium circulation, and reagent recovery, offers comprehensive advantages in achieving high-value recovery of fluorine and sulfur resources, avoiding secondary pollution, and reducing processing costs.

[0065] Comparative Example 2

[0066] The fluorinated mixed acid was taken from a photovoltaic silicon wafer etching waste liquid, and its composition was the same as in Example 1 (mass fraction: HF 12.0%, H2SO4 25.0%, H2SiF6 8.5%, Fe). 3+ 0.8%, Cu 2+ 0.3% of the total, 2% of the total heavy metals, and the remainder being water); the NaCl solution concentration was 36.0 g / 100 mL; the purity of aniline was ≥99.0%; Na2S, NaOH, and CaCl2 were all industrial grade (purity ≥98.0%).

[0067] S1: Fluorosilicate precipitation separation

[0068] Same as Example 1. Take 100 parts of fluorinated mixed acid, and under constant temperature of 25°C, slowly add 10 parts of saturated NaCl solution at a dropping rate of 2 mL / min. After reacting for 0.5 h, filter to obtain the precipitate Na2SiF6 with a dry weight of 10.1 g and a purity of 97.4%. Also, the first filtrate, with a volume of approximately 100 parts, contains 7.2% HF and 14.5% H2SO4.

[0069] S2: Preparation and decomposition of aniline hydrofluoric acid

[0070] The first filtrate was transferred to a PFA reactor, and 45 parts of aniline (replacing pyridine) were slowly added at room temperature. The stirring rate was 300 r / min, and the reaction was carried out for 0.5 hours. The vacuum distillation system was started. Due to the high boiling point of aniline, the distillation temperature was controlled at 50℃ and the pressure at 20 kPa, and distillation was continued for 1 hour. The distillate was collected using a PFA condenser and passed into a 15% CaCl2 solution (120 parts by mass) for absorption, with stirring for 0.5 hours. Filtration was performed to separate CaF2 precipitate and aniline solution. The CaF2 precipitate, after washing and drying, weighed 19.5 g (purity 98.5%, slightly lower than in Example 1). The aniline content in the aniline solution was 24.8 parts, with a recovery rate of 85.0% (calculated based on the initial addition amount). The aniline solution was reused in this step. The mother liquor after distillation was the second filtrate, with a volume of approximately 112 parts.

[0071] S3: Heavy metal ion removal

[0072] Same as Example 1. Add 5 parts of Na₂S solution to the second filtrate in three portions, 20 min apart. Adjust the pH to 6.0 with 30% NaOH. React at 25°C for 1 hour, then filter to obtain a heavy metal filter cake with a dry weight of 2.3 g and a heavy metal removal rate ≥99.0%. Also obtain a third filtrate with a volume of 10⁷ parts, containing SO₄²⁻. 2- The mass fraction is approximately 18.6%.

[0073] S4: Preparation of high-purity calcium sulfate

[0074] The preparation steps are the same as in Example 1. The third filtrate was heated to 40°C, and 16 parts of saturated CaCl2 solution were added. After reacting for 1 hour, the mixture was filtered to obtain CaSO4 precipitate with a dry weight of 23.1 g and a purity of 99.6%, as well as the fourth filtrate with a volume of 98 parts. The main component was aniline hydrochloride with a mass fraction of about 18.5%. Due to the weak basicity of aniline, the salt concentration was slightly higher.

[0075] S5: Aniline and sodium chloride recovery and reuse

[0076] Add 18 parts of 30% NaOH solution to the fourth filtrate, stir and react for 1.0 h, then start the vacuum distillation system. Aniline has a high boiling point, so control the temperature at 80℃ and the pressure at 15 kPa for distillation separation. Collect aniline as distillate, with a measured amount of 8.8 parts and a recovery rate of 88.0% (based on theoretical production). Recycle it to step S2. Cool the distillation residue to crystallize, filter to obtain solid NaCl with a dry weight of 7.8 g and a purity of 97.5%. Recycle it to step S1.

[0077] Ultimately, the fluorine recovery rate of the fluorinated mixed acid was 90.2%, lower than 93.5% in Example 1; the sulfate conversion rate was 97.5%, slightly lower than 98.0% in Example 1; the total aniline recovery rate was 86.5%, lower than the pyridine recovery rate of 93.1% in Example 1; and the sodium chloride recovery rate was 89.0%, lower than 92.7% in Example 1. The process in Comparative Example 2 achieved resource utilization of the fluorinated mixed acid without secondary pollution emissions. However, compared to pyridine, aniline, due to its weaker basicity and greater volatility and oxidation, resulted in a decrease in the recovery rate of key components and poorer operational stability.

[0078] A comprehensive comparison of the process effects of Example 1 and Comparative Example 2 is shown in Table 2:

[0079] Table 2 provides a comprehensive comparison of the process effects of Example 1 and Comparative Example 2.

[0080] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-purity calcium fluoride and calcium sulfate through resource-based treatment of fluorine-containing mixed acids, characterized in that: Includes the following steps: (1) Mix the fluorinated mixed acid with the halide solution, react and then filter to separate, to obtain fluorosilicate precipitate and first filtrate; (2) Add an organic base to the first filtrate, perform vacuum distillation, pass the distillate into a soluble calcium salt solution for reaction, and after filtration and separation, obtain high-purity calcium fluoride (CaF2) precipitate, organic base filtrate and second filtrate; the organic base can be recycled; (3) Add a heavy metal precipitant to the second filtrate, adjust the system to alkaline conditions, react, filter and separate to obtain heavy metal precipitate and third filtrate; (4) The third filtrate was reacted with calcium chloride (CaCl2) solution, and after filtration and separation, calcium sulfate (CaSO4) precipitate and the fourth filtrate were obtained; (5) Add sodium hydroxide (NaOH) to the fourth filtrate and react to separate the organic base and sodium chloride (NaCl); the organic base and sodium chloride (NaCl) can be recycled.

2. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (1), the halide is one of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2) or calcium chloride (CaCl2).

3. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (1), the reaction temperature is 25~40℃ and the reaction time is 0.5~1.5h.

4. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (1), the fluorinated mixed acid includes hydrofluoric acid (HF), fluorosilicic acid (H2SiF6), sulfuric acid (H2SO4), hydrochloric acid (HCl) and metal cations; the fluorinated mixed acid needs to be pretreated and the acidity is 1~3 mol / L.

5. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (2), the soluble calcium salt is one of calcium chloride (CaCl2), calcium nitrate (Ca(NO3)2), calcium dihydrogen phosphate (Ca(H2PO4)2), calcium bicarbonate (Ca(HCO3)2), calcium bisulfite (Ca(HSO3)2), calcium hypochlorite (Ca(ClO)2), calcium bromide (CaBr2), calcium iodide (CaI2), calcium chlorate (Ca(ClO3)2), calcium perchlorate (Ca(ClO4)2), and calcium permanganate (Ca(MnO4)2).

6. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (2), the organic base is one of pyridine, pyridine compounds, quinoline, or isoquinoline organic bases.

7. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (2), the specific process of vacuum distillation is as follows: the temperature is controlled at 40~50℃, the pressure is controlled at 20~40kPa, and the reaction time is 1~2h.

8. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (3), the heavy metal precipitant is one of soluble sulfides, dithiocarbamate compounds, and xanthate compounds.

9. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (3), the third filtrate is an organic alkali solution.

10. The method for preparing high-purity calcium fluoride and calcium sulfate by resource utilization of fluorine-containing mixed acid according to claim 1, characterized in that, In step (3), the alkaline condition is a pH value of 6 to 8.

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