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CN-122010156-A - Method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid

CN122010156ACN 122010156 ACN122010156 ACN 122010156ACN-122010156-A

Abstract

The invention discloses a method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid, which comprises the following steps of (1) mixing fluorine-containing mixed acid with halide solution, filtering and separating after reaction to obtain fluorosilicate precipitate and first filtrate, (2) adding organic alkali into the first filtrate, performing reduced pressure distillation, introducing distillate into soluble calcium salt solution for reaction, filtering and separating to obtain calcium fluoride precipitate, organic alkali filtrate and second filtrate, (3) adding heavy metal precipitant into the second filtrate, adjusting the system to alkaline condition for reaction, filtering and separating to obtain heavy metal precipitate and third filtrate, (4) reacting the third filtrate with calcium chloride solution, filtering and separating to obtain calcium sulfate precipitate and fourth filtrate, adding sodium hydroxide into the fourth filtrate for reaction, separating, and recovering to obtain organic alkali and sodium chloride. The invention realizes the resource utilization of fluorine, calcium, sulfur and other elements, and the purity of the obtained calcium fluoride, calcium sulfate and other products is not less than 99 percent.

Inventors

  • HAN SIYU
  • YANG XIAO
  • ZHOU XIAO
  • HU CHENGZHI
  • LIANG QIAN
  • HAN ZHENGCHANG
  • LI PENGPENG
  • MA JUNJUN
  • BU XULING
  • HUANG HAIFENG
  • TAO ZHIHUI
  • ZHU JIAMING
  • XIE CHENGWEI

Assignees

  • 南京格洛特环境工程股份有限公司
  • 盐城市城投格洛特环境科技股份有限公司

Dates

Publication Date
20260512
Application Date
20251231

Claims (10)

  1. 1. A method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid is characterized by comprising the following steps: (1) Mixing fluorine-containing mixed acid with halide solution, reacting, filtering and separating to obtain fluorosilicate precipitate and first filtrate; (2) Adding organic alkali into the first filtrate, performing reduced pressure distillation, introducing the distillate into a soluble calcium salt solution for reaction, and filtering and separating to obtain high-purity calcium fluoride (CaF 2 ) precipitate, organic alkali filtrate and second filtrate, wherein the organic alkali can be recycled; (3) Adding a heavy metal precipitator into the second filtrate, adjusting the system to alkaline conditions for reaction, and filtering and separating to obtain heavy metal precipitate and third filtrate; (4) Reacting the third filtrate with a calcium chloride (CaCl 2 ) solution, and filtering and separating to obtain a calcium sulfate (CaSO 4 ) precipitate and a fourth filtrate; (5) Adding sodium hydroxide (NaOH) into the fourth filtrate for reaction, separating, and recovering to obtain organic alkali and sodium chloride (NaCl), wherein the organic alkali and the sodium chloride (NaCl) can be recycled.
  2. 2. The method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (1), the halide is one of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl 2 ) or calcium chloride (CaCl 2 ).
  3. 3. The method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (1), the reaction temperature is 25-40 ℃ and the reaction time is 0.5-1.5 h.
  4. 4. The method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (1), the fluorine-containing mixed acid comprises hydrofluoric acid (HF), fluosilicic acid (H 2 SiF 6 ), sulfuric acid (H 2 SO 4 ), hydrochloric acid (HCl) and metal cations, and the acidity of the fluorine-containing mixed acid is 1-3 mol/L.
  5. 5. The method for preparing high purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (2), the soluble calcium salt is one of calcium chloride (CaCl 2 ), calcium nitrate (Ca (NO 3 ) 2 ), calcium dihydrogen phosphate (Ca (H 2 PO 4 ) 2 ), calcium hydrogen carbonate (Ca (HCO 3 ) 2 ), calcium hydrogen sulfite (Ca (HSO 3 ) 2 ), calcium hypochlorite (Ca (ClO) 2 ), calcium bromide (CaBr 2 ), calcium iodide (CaI 2 ), calcium chlorate (Ca (ClO 3 ) 2 ), calcium perchlorate (Ca (ClO 4 ) 2 ), and calcium permanganate (Ca (MnO 4 ) 2 ).
  6. 6. The method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (2), the organic base is one of pyridine, pyridine compound, quinoline and isoquinoline organic base.
  7. 7. The method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (2), the specific process of reduced pressure distillation is that the temperature is controlled to be 40-50 ℃, the pressure is controlled to be 20-40 kPa, and the reaction time is 1-2 hours.
  8. 8. The method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (3), the heavy metal precipitant is one of soluble sulfide, dithiocarbamate compound and xanthate compound.
  9. 9. The method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (3), the third filtrate is an organic alkali solution.
  10. 10. The method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid according to claim 1, wherein in the step (3), the alkaline condition is that the pH value is 6-8.

Description

Method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid Technical Field The invention relates to the technical field of environmental protection, in particular to a method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid. Background The fluorine-containing mixed acid is widely generated in industrial links such as semiconductor etching, electroplating, photovoltaic cleaning and the like, has strong corrosiveness of hydrofluoric acid and acidity of other inorganic acids, and fluorine ions are easy to cause excessive fluorine in water and calcification of soil and can corrode equipment pipelines. The traditional neutralization precipitation method has the defects of incomplete fluorine removal, large sludge amount and the like, is difficult to realize zero emission in the aspects of reuse or recycling, cannot meet the severe environmental protection standard, and causes resource waste. Disclosure of Invention The invention aims to provide a method for preparing high-purity calcium fluoride and calcium sulfate by recycling fluorine-containing mixed acid for removing heavy metal ions, wherein the purity of the calcium fluoride and the calcium sulfate is high. In order to achieve the aim, the invention provides the following technical scheme that the method for preparing the high-purity calcium fluoride and calcium sulfate by recycling the fluorine-containing mixed acid comprises the following steps: (1) Mixing fluorine-containing mixed acid with halide solution, reacting, filtering and separating to obtain fluorosilicate precipitate and first filtrate; (2) Adding organic alkali into the first filtrate, performing reduced pressure distillation, introducing the distillate into a soluble calcium salt solution for reaction, and filtering and separating to obtain high-purity calcium fluoride precipitate, organic alkali filtrate and second filtrate, wherein the organic alkali can be recycled; (3) Adding a heavy metal precipitator into the second filtrate, adjusting the system to alkaline conditions for reaction, and filtering and separating to obtain heavy metal precipitate and third filtrate; (4) Reacting the third filtrate with a calcium chloride solution, and filtering and separating to obtain a calcium sulfate precipitate and a fourth filtrate; (5) And adding sodium hydroxide into the fourth filtrate to react, separating, and recovering to obtain organic alkali and sodium chloride, wherein the organic alkali and the sodium chloride can be recycled. Preferably, in the step (1), the halide is one of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl 2) or calcium chloride (CaCl 2). Preferably, in the step (1), the reaction temperature is 25-40 ℃ and the reaction time is 0.5-1.5 h. Preferably, in the step (1), the fluorine-containing mixed acid comprises hydrofluoric acid (HF), fluosilicic acid (H 2SiF6), sulfuric acid (H 2SO4), hydrochloric acid (HCl) and metal cations, wherein the fluorine-containing mixed acid needs to be pretreated, and the acidity is 1-3 mol/L. Preferably, in the step (2), the soluble calcium salt is one of calcium chloride (CaCl 2), calcium nitrate (Ca (NO 3)2), monocalcium phosphate (Ca (H 2PO4)2), calcium bicarbonate (Ca (HCO 3)2), calcium bisulfide (Ca (HSO 3)2), calcium hypochlorite (Ca (ClO) 2), calcium bromide (CaBr 2), calcium iodide (CaI 2), calcium chlorate (Ca (ClO 3)2), calcium perchlorate (Ca (ClO 4)2), and calcium permanganate (Ca (MnO 4)2)). Preferably, in the step (2), the organic base is one of pyridine, pyridine compound, quinoline and isoquinoline organic base. Preferably, the pyridine compound is one of picoline, lutidine, pyrazine, pyrimidine and pyridazine. Preferably, in the step (2), the specific process of reduced pressure distillation is that the temperature is controlled to be 40-50 ℃, the pressure is controlled to be 20-40 kPa, and the reaction time is 1-2 hours. Preferably, the heavy metal precipitant is one of soluble sulfide, dithio carbamate compound and xanthate compound. Preferably, in step (3), the third filtrate is an organic alkali solution. Preferably, in the step (3), the alkaline condition is that the pH value is 6-8. Compared with the prior art, the method has the beneficial effects that firstly, the mixed acid containing fluorine reacts with the halide solution at normal temperature to separate out fluorosilicate precipitate, then, organic alkali is added into the filtrate, the filtrate is distilled under reduced pressure, the distilled gas is introduced into soluble metal chloride to obtain high-purity calcium fluoride, and the organic alkali filtrate can be recycled. Removing heavy metal ions by using organic alkali to assist sulfide reagent, reacting distillation mother liquor with calcium chloride to obtain high-purity calcium sulfate and pyridine hydrochloride filtrate, and treating the filtrate to obtain the o