CN113998710A - Method for separating potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate mixed salt - Google Patents
Method for separating potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate mixed salt Download PDFInfo
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
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- C01D3/10—Bromides
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- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
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- C01D7/10—Preparation of bicarbonates from carbonates
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Abstract
The invention discloses a method for separating potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate mixed salt, which comprises the steps of firstly dissolving potassium fluoride, potassium bromide and potassium carbonate in a mother liquor leaching manner; introducing carbon dioxide to convert potassium carbonate dissolved in the leaching mother liquor into potassium bicarbonate, separating to obtain a liquid phase and crude potassium bicarbonate salt, purifying, and returning washing water to the leaching process to serve as the leaching mother liquor; converting potassium bicarbonate in the liquid phase into potassium bromide by adding hydrobromic acid, and then adjusting the solution to be neutral; evaporating and concentrating the neutral solution to obtain potassium bromide and an evaporation finished solution; and cooling the evaporated solution, adding crystal seeds to obtain potassium fluoride hydrate and circulating mother liquor, and returning the circulating mother liquor to the evaporation concentration process. The invention can separate and recycle the chemical resources in the potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate mixed salt, thereby realizing the purposes of recycling and harmless treatment.
Description
Technical Field
The invention relates to a method for separating mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride, in particular to a method for recycling chemical resources in fine chemical industry byproduct waste salt and obtaining an inorganic salt product.
Background
In the fine chemical synthesis process, inorganic alkali potassium carbonate is usually used as an acid-binding agent, and a large amount of mixed salt containing potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride is generated along with the occurrence of fluorination and bromination reactions. The mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride has the characteristics of complex composition, high treatment cost and great environmental hazard, and the conventional salt washing process, high-temperature oxidation, high-temperature carbonization and high-level oxidation can not realize resource utilization and are difficult to directly treat.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and solve the problem that the mixed salt is difficult to recycle, and provides a method for separating the mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride.
The technical purpose of the invention is realized by the following technical scheme.
A method for separating potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate mixed salt comprises the steps of mother liquor leaching, carbon dioxide carbonization, potassium bicarbonate crude salt purification, acid-base regulation and control, evaporation concentration, potassium bromide crude salt purification, cooling and potassium fluoride hydrate preparation, wherein the steps of:
Adding a leaching mother liquor into a potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride mixed salt, wherein the leaching mother liquor is a saturated potassium bicarbonate aqueous solution, and fully stirring and uniformly mixing to dissolve most of potassium fluoride, potassium bromide and potassium carbonate in the mixed salt into the leaching mother liquor to obtain a mixed salt solution;
in the step 1, the stirring speed is 100-300 r/min, and the stirring time is 20-40 min.
Introducing carbon dioxide into the mixed salt solution obtained after the mother solution is leached in the step 1, converting potassium carbonate in the mixed salt solution into potassium bicarbonate, stopping introducing the carbon dioxide when the pH value of the system is reduced to 7-8, and performing solid-liquid separation to obtain crude potassium bicarbonate salt and filtrate;
in step 2, when the pH value of the system is reduced to 7-8, the introduction of carbon dioxide is stopped.
Adding water into the potassium bicarbonate crude salt obtained by solid-liquid separation in the step 2 for washing, wherein the water addition amount is 1.5-2 times of the mass sum of the potassium carbonate, the potassium bicarbonate, the potassium bromide and the potassium fluoride mixed salt, carrying out solid-liquid separation after washing to obtain potassium bicarbonate and washing water, and using the washing water as the leaching mother liquor in the step 1 to return to the mother liquor leaching in the step 1;
in the step 3, the water addition amount is 1.5 to 2 times of the mass of the mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride.
Adding hydrobromic acid into the filtrate subjected to the carbon dioxide carbonization treatment in the step 2 to reduce the pH value of the filtrate to 3-4, adding potassium hydroxide to make the solution neutral to obtain a neutral solution, and completely converting potassium bicarbonate in the system into potassium bromide;
in step 4, hydrobromic acid is added to reduce the pH value of the filtrate to 3-4;
in step 4, an aqueous solution of potassium hydroxide is optionally added in a concentration of 0.1 to 0.5mol/L, the pH of the neutral solution being in the range from 6 to 8, preferably from 7 to 8.
Step 5, evaporating and concentrating
And (4) evaporating and concentrating the neutral solution obtained by the acid-base regulation and control treatment in the step (4), gradually separating out potassium bromide in the process, preserving heat and settling after the solution is evaporated to 120-125 ℃, and performing solid-liquid separation to obtain crude potassium bromide salt and an evaporation finished solution.
Step 6, purifying potassium bromide crude salt
Adding water into the potassium bromide crude salt obtained by evaporation concentration for washing, wherein the added water amount is 0.5-1 time of the mass of the potassium bromide crude salt, carrying out solid-liquid separation after washing to obtain potassium bromide and a washing solution, returning the washing solution to the step 5, and carrying out evaporation concentration on the washing solution, the neutral solution obtained in the step 4 and the filtrate obtained in the step 8;
in step 6, the water addition amount is 0.5-1 times of the mass of the crude potassium bromide salt.
Cooling the evaporation completion liquid obtained after the evaporation concentration treatment in the step 5 to a temperature range of 15-35 ℃ to obtain a low-temperature solution;
in step 7, the temperature of the evaporation finished liquid is 120-125 ℃, and the natural cooling speed is adopted.
And (3) adding potassium fluoride seed crystals into the low-temperature solution subjected to cooling treatment in the step (7), separating out solids, and then performing solid-liquid separation, wherein the solids are potassium fluoride hydrates, and the filtrate is a circulating mother liquor and returns to the evaporation concentration in the step (5), and is evaporated and concentrated together with the neutral solution obtained in the step (4) and the washing solution in the step (6).
In step 8, the potassium fluoride hydrate is potassium fluoride dihydrate and/or potassium fluoride tetrahydrate.
According to the method for separating the mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride, the mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride is extracted and utilized in the form of inorganic substances such as potassium bicarbonate, potassium bromide, potassium fluoride hydrate and the like, so that resource recovery is realized, and pollution and harm to the environment caused by the mixed salt are reduced.
Drawings
FIG. 1 is a process flow diagram of a method for separating mixed salts of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride according to the invention.
FIG. 2 is a graph showing the solubility curves of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride according to the present invention at different temperatures.
FIG. 3 is a graph showing the conversion law of carbonate and bicarbonate at different pH values during the carbonization of carbon dioxide according to the present invention.
Detailed Description
The technical scheme of the invention is further explained by combining specific examples.
Firstly, the components of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride mixed salt (experimental sample) are detected, and the main components are detailed in the following table.
| Serial number | Detecting items | Mass percent (wt%) |
| 1 | Potassium carbonate | 22 |
| 2 | Potassium bicarbonate | 26 |
| 3 | Potassium bromide | 27 |
| 4 | Potassium fluoride | 25 |
Secondly, the potassium carbonate, the potassium bicarbonate, the potassium bromide and the potassium fluoride mixed salt are treated by adopting the technical scheme of the invention at the room temperature of 20-30 ℃.
1. Mother liquor leaching
1kg of mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride is put in a 3L beaker, the mixture is added with a leaching mother liquor and then fully stirred for 0.5h, the leaching mother liquor is a saturated potassium bicarbonate aqueous solution prepared at room temperature, the potassium bicarbonate in the mixed salt cannot be dissolved in the leaching mother liquor due to the fact that the potassium bicarbonate in the leaching mother liquor is in a saturated state and exists in a solid form, and most of the potassium carbonate, the potassium bromide and the potassium fluoride are dissolved in the leaching mother liquor, so that a mixed salt solution is obtained; the leached mixed salt solution is subjected to the next step.
The technical scheme of the invention is adopted for mother liquor leaching, the difference of inorganic salt solubility is utilized to enable potassium bicarbonate in the system to exist in a solid form, the solubility curves of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride at different temperatures are shown in figure 2, the solubility of potassium bicarbonate is the lowest at the same temperature, and the solubilities of the other three components (potassium carbonate, potassium bromide and potassium fluoride) are obviously higher than that of potassium bicarbonate.
2. Carbonization of carbon dioxide
Introducing carbon dioxide into the mixed salt solution obtained after the mother solution is leached in the step 1, converting potassium carbonate in the mixed salt solution into potassium bicarbonate, stopping introducing the carbon dioxide when the pH value of the system is reduced to 7-8, and performing solid-liquid separation to obtain crude potassium bicarbonate salt and filtrate, wherein the chemical reaction involved in the carbon dioxide carbonization process is as follows:
K2CO3+CO2+H2O＝KHCO3
because the mixed salt solution obtained after the mother solution is leached in the step 1 belongs to a saturated potassium bicarbonate aqueous solution, potassium carbonate in the system is converted into potassium bicarbonate after carbon dioxide is introduced.
Liquid phase determination: after the carbon dioxide carbonization is finished, respectively taking the carbide solutions with different pH values, after solid-liquid separation, detecting the percentage contents (unit weight percent) of potassium carbonate and potassium bicarbonate in the filtrate by adopting a chemical titration method.
Percentage content of carbonate radical and bicarbonate radical in carbonized filtrate
| Serial number | pH value of filtrate | Potassium carbonate (wt%) | Potassium bicarbonate (wt%) |
| 1 | 7.7 | 0.0 | 16.5 |
| 2 | 7.5 | 0.0 | 15.8 |
| 3 | 7.6 | 0.0 | 16.4 |
| 4 | 7.8 | 0.0 | 16.6 |
| 5 | 7.3 | 0.0 | 15.7 |
Namely, after the technical scheme of the invention is adopted for carbonization, potassium carbonate in the system is completely converted into potassium bicarbonate. The conversion law of carbonate and bicarbonate at different pH values is shown in figure 3.
3. Purification of crude potassium bicarbonate salt
And (2) adding water into the potassium bicarbonate crude salt obtained by solid-liquid separation in the step (2) for washing, wherein the added water amount is 1.5 times of the mass sum of the potassium carbonate, the potassium bicarbonate, the potassium bromide and the potassium fluoride mixed salt, carrying out solid-liquid separation after washing to obtain potassium bicarbonate and washing water, and the washing water can be used as the leaching mother liquor in the step (1) and returns to the mother liquor leaching in the step (1).
The potassium bicarbonate crude salt is purified by adopting the technical scheme of the invention, as shown in the attached figure 2, the solubility of potassium bicarbonate is lower than that of potassium bromide and potassium fluoride at the same temperature, the potassium fluoride and the potassium bromide can be dissolved in washing water through washing, solid-liquid separation is carried out to obtain a potassium bicarbonate product and washing water, the potassium bicarbonate in the washing water is in a saturated state, and the washing water returns to the step 1 to be used as leaching mother liquor.
4. Acid base regulation
And (3) adding hydrobromic acid into the filtrate subjected to the carbon dioxide carbonization treatment in the step (2) to reduce the pH value of the filtrate to 3-4, and adding potassium hydroxide to make the solution neutral to obtain a neutral solution, wherein the pH value range is 6-8. The chemical reactions involved in acid-base regulation are as follows:
1) adding hydrobromic acid
KHCO3+HBr＝KBr+H2O+CO2↑
Liquid phase determination: and (3) after the acid is added, taking the solution at different pH values, and detecting the percentage content (unit weight) of the potassium bicarbonate in the solution.
Percentage of bicarbonate in the acidified solution
| Serial number | pH value of solution | Potassium bicarbonate (wt%) |
| 1 | 3.6 | 0.0 |
| 2 | 3.4 | 0.0 |
| 3 | 3.8 | 0.0 |
| 4 | 3.7 | 0.0 |
| 5 | 3.5 | 0.0 |
Namely, after the technical scheme of the invention is adopted for acidification, the potassium bicarbonate in the system is completely converted into potassium bromide. The conversion law of bicarbonate and carbonate under different pH values is shown in figure 3.
2) Adding potassium hydroxide
HBr+KOH＝KBr+H2O
The acidified solution is acidic and needs to be adjusted to be neutral by adding alkali.
5. Concentrating by evaporation
And (4) evaporating and concentrating the neutral solution obtained by the acid-base regulation and control treatment in the step (4), gradually separating out potassium bromide in the process, preserving heat and settling after the solution is evaporated to 120-125 ℃, and performing solid-liquid separation to obtain potassium bromide crude salt and an evaporation completion solution.
Solid phase assay: after evaporation was complete, the percentage contents (in wt%) of potassium bromide, potassium fluoride and water in the settled solids were determined at different temperatures.
Evaporation concentration to separate out solid composition
Namely, the potassium bromide crude salt can be obtained by adopting the technical scheme of the invention to carry out evaporation concentration.
6. Purification of crude potassium bromide salt
And (3) adding water into the potassium bromide crude salt obtained by evaporation concentration for washing, wherein the added water amount is 0.8 times of the mass of the potassium bromide crude salt, carrying out solid-liquid separation after washing to obtain potassium bromide and a washing solution (containing potassium bromide), and returning the washing solution to the step 5 to carry out evaporation concentration together with the neutral solution obtained in the step 4.
7. Cooling down
And (5) cooling the evaporation completion liquid obtained after the evaporation concentration treatment in the step (the temperature of the evaporation completion liquid is 120-125 ℃, and the natural cooling speed is adopted), wherein the supersaturation degree of the potassium fluoride is high, the solution is not separated out in the whole cooling process, and the low-temperature solution is obtained after the temperature of the solution is reduced to a temperature range of 15-35 ℃, and then the next step is carried out.
8. Preparation of potassium fluoride hydrate
Adding potassium fluoride seed crystals (namely potassium fluoride) into the low-temperature solution subjected to cooling treatment in the step 7, separating out solids, and then performing solid-liquid separation (after the potassium fluoride seed crystals are added, the solution can generate crystallization), wherein the solids are potassium fluoride hydrate, the filtrate is circulating mother liquor and returns to the evaporation concentration in the step 5, and the circulating mother liquor, the neutral solution obtained in the step 4 and the washing solution in the step 6 are evaporated and concentrated together.
Solid phase assay: the potassium fluoride exists in different hydrate forms, and the existence form of potassium fluoride hydrate separated out at different temperatures is detected by X-ray diffraction (XRD).
Forms of potassium fluoride hydrate at different temperatures
| Serial number | Temperature (. degree.C.) | |
| 1 | 35 | KF·2H2O |
| 2 | 30 | KF·2H2O |
| 3 | 25 | KF·2H2O |
| 4 | 20 | KF·4H2O |
| 5 | 15 | KF·4H2O |
Namely, the technical scheme of the invention is adopted to prepare the potassium fluoride hydrate, and the potassium fluoride dihydrate and the potassium fluoride tetrahydrate can be obtained.
According to the above experimental analysis, 1kg of a mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride was treated, as detailed in examples 1 to 3 below.
Example 1
1kg of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride mixed salt is taken, leaching mother liquor (saturated potassium bicarbonate aqueous solution) is added, carbon dioxide is introduced after uniform stirring, the pH value of the salt solution is reduced to 7.8, solid-liquid separation is carried out, and crude potassium bicarbonate salt and filtrate are obtained. Adding water into the crude potassium bicarbonate salt for washing, wherein the added water amount is 1.5 times of the mass of the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate, carrying out solid-liquid separation after washing is finished, obtaining a solid potassium bicarbonate product, and returning the obtained solution to the leaching step to serve as a leaching mother solution; hydrobromic acid was added to the filtrate to reduce the pH to 3.6, and potassium hydroxide was added to bring the solution pH to 7.3. Heating the obtained neutral solution to 121 ℃ for evaporation concentration, performing solid-liquid separation after heat preservation and sedimentation to obtain crude potassium bromide salt and an evaporation finished solution. Adding water into the potassium bromide crude salt for washing, wherein the added water amount is 0.8 times of the mass of the potassium bromide crude salt, carrying out solid-liquid separation after washing is finished, obtaining a solid which is a potassium bromide product, and returning the obtained solution to an evaporation concentration process; cooling the evaporated solution to 30 ℃, adding potassium fluoride crystal seeds, carrying out solid-liquid separation after heat preservation and sedimentation to obtain potassium fluoride hydrate and residual mother liquor, and returning the residual mother liquor filtrate to the evaporation and concentration process for recycling.
Example 2
Taking 1kg of mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride, adding the leaching mother liquor, uniformly stirring, introducing carbon dioxide, reducing the pH value of the salt solution to 7.5, and carrying out solid-liquid separation to obtain crude potassium bicarbonate salt and filtrate. Adding water into the crude potassium bicarbonate salt for washing, wherein the added water amount is 1.2 times of the mass of the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate, carrying out solid-liquid separation after washing is finished, obtaining a solid potassium bicarbonate product, and returning the obtained solution to the leaching step to serve as a leaching mother solution; hydrobromic acid was added to the filtrate to reduce the pH to 3.8, and potassium hydroxide was added to bring the solution pH to 6.8. Heating the obtained neutral solution to 123 ℃ for evaporation concentration, performing solid-liquid separation after heat preservation and sedimentation to obtain potassium bromide crude salt and evaporation finished liquid. Adding water into the potassium bromide crude salt for washing, wherein the added water amount is 1 time of the mass of the potassium bromide crude salt, carrying out solid-liquid separation after washing is finished, obtaining a solid potassium bromide product, and returning the obtained solution to an evaporation concentration process; cooling the evaporated solution to 20 ℃, adding potassium fluoride crystal seeds, carrying out solid-liquid separation after heat preservation and sedimentation to obtain potassium fluoride hydrate and residual mother liquor, and returning the residual mother liquor filtrate to the evaporation and concentration process for recycling.
Example 3
Taking 1kg of mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride, adding the leaching mother liquor, uniformly stirring, introducing carbon dioxide, reducing the pH value of the salt solution to 7.3, and carrying out solid-liquid separation to obtain crude potassium bicarbonate salt and filtrate. Adding water into the crude potassium bicarbonate salt for washing, wherein the added water amount is 1 time of the mass of the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate, carrying out solid-liquid separation after washing is finished, obtaining a solid potassium bicarbonate product, and returning the obtained solution to the leaching step to serve as a leaching mother solution; hydrobromic acid was added to the filtrate to reduce the pH to 3, and potassium hydroxide was added to bring the solution pH to 7.5. Heating the obtained neutral solution to 122 ℃ for evaporation concentration, performing solid-liquid separation after heat preservation and sedimentation to obtain crude potassium bromide salt and an evaporation finished solution. Adding water into the potassium bromide crude salt for washing, wherein the added water amount is 0.8 times of the mass of the potassium bromide crude salt, carrying out solid-liquid separation after washing is finished, obtaining a solid which is a potassium bromide product, and returning the obtained solution to an evaporation concentration process; cooling the evaporated solution to 25 ℃, adding potassium fluoride crystal seeds, carrying out solid-liquid separation after heat preservation and sedimentation to obtain potassium fluoride hydrate and residual mother liquor, and returning the residual mother liquor filtrate to the evaporation and concentration process for recycling.
According to the invention, the process parameters are adjusted, so that the resource treatment of the potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride mixed salt can be realized. The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.
Claims (9)
1. The method for separating the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate is characterized by comprising the steps of mother liquor leaching, carbon dioxide carbonization, crude potassium bicarbonate salt purification, acid-base regulation, evaporation concentration, crude potassium bromide salt purification, cooling and potassium fluoride hydrate preparation, wherein:
step 1, mother liquor leaching
Adding a leaching mother liquor into a potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride mixed salt, wherein the leaching mother liquor is a saturated potassium bicarbonate aqueous solution, and fully stirring and uniformly mixing to dissolve most of potassium fluoride, potassium bromide and potassium carbonate in the mixed salt into the leaching mother liquor to obtain a mixed salt solution;
step 2, carbonizing carbon dioxide
Introducing carbon dioxide into the mixed salt solution obtained after the mother solution is leached in the step 1, converting potassium carbonate in the mixed salt solution into potassium bicarbonate, stopping introducing the carbon dioxide when the pH value of the system is reduced to 7-8, and performing solid-liquid separation to obtain crude potassium bicarbonate salt and filtrate;
step 3, purifying the crude potassium bicarbonate salt
Adding water into the potassium bicarbonate crude salt obtained by solid-liquid separation in the step 2 for washing, wherein the water addition amount is 1.5-2 times of the mass sum of the potassium carbonate, the potassium bicarbonate, the potassium bromide and the potassium fluoride mixed salt, carrying out solid-liquid separation after washing to obtain potassium bicarbonate and washing water, and using the washing water as the leaching mother liquor in the step 1 to return to the mother liquor leaching in the step 1;
step 4, acid-base regulation
Adding hydrobromic acid into the filtrate subjected to the carbon dioxide carbonization treatment in the step 2 to reduce the pH value of the filtrate to 3-4, adding potassium hydroxide to make the solution neutral to obtain a neutral solution, and completely converting potassium bicarbonate in the system into potassium bromide;
step 5, evaporating and concentrating
Evaporating and concentrating the neutral solution obtained by the acid-base regulation and control treatment in the step 4, gradually separating out potassium bromide in the process, preserving heat and settling after the solution is evaporated to 120-125 ℃, and performing solid-liquid separation to obtain crude potassium bromide salt and an evaporation completion solution;
step 6, purifying potassium bromide crude salt
Adding water into the potassium bromide crude salt obtained by evaporation concentration for washing, wherein the added water amount is 0.5-1 time of the mass of the potassium bromide crude salt, carrying out solid-liquid separation after washing to obtain potassium bromide and a washing solution, returning the washing solution to the step 5, and carrying out evaporation concentration on the washing solution, the neutral solution obtained in the step 4 and the circulating mother solution obtained in the step 8;
step 7, cooling
Cooling the evaporation completion liquid obtained after the evaporation concentration treatment in the step 5, and obtaining a low-temperature solution after the temperature of the solution is reduced to a temperature range of 15-35 ℃;
step 8, preparation of potassium fluoride hydrate
Adding potassium fluoride seed crystals into the low-temperature solution subjected to cooling treatment in the step 7, separating out solids, and then performing solid-liquid separation, wherein the solids are potassium fluoride hydrate, and the filtrate is returned to the evaporation concentration in the step 5 as circulating mother liquor, and is subjected to evaporation concentration together with the neutral solution obtained in the step 4 and the washing solution in the step 6.
2. The method for separating the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate as claimed in claim 1, wherein in step 1, the stirring speed is 100-300 r/min and the stirring time is 20-40 min.
3. The method for separating the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate as claimed in claim 1, wherein in step 2, when the pH value of the system is reduced to 7-8, the introduction of carbon dioxide is stopped.
4. The method for separating the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate as claimed in claim 1, wherein in step 3, the amount of water added is 1.5-2 times of the mass of the mixed salt of potassium carbonate, potassium bicarbonate, potassium bromide and potassium fluoride.
5. The method of claim 1, wherein in step 4, hydrobromic acid is added to lower the pH of the filtrate to 3-4.
6. The process of claim 1, wherein in step 4, an aqueous solution of potassium hydroxide is added to the mixture at a concentration of 0.1 to 0.5mol/L, and the pH value of the neutral solution is in the range of 6 to 8, preferably 7 to 8.
7. The method for separating the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate as claimed in claim 1, wherein in step 6, the amount of water added is 0.5-1 times of the mass of the crude salt of potassium bromide.
8. The method for separating the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate as claimed in claim 1, wherein the temperature of the evaporation completion liquid is 120-125 ℃ in step 7, and the natural cooling rate is adopted.
9. The method for separating the mixed salt of potassium fluoride, potassium bromide, potassium carbonate and potassium bicarbonate as claimed in claim 1, wherein in step 8, the potassium fluoride hydrate is potassium fluoride dihydrate and/or potassium fluoride tetrahydrate.
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| CN115650280A (en) * | 2022-09-09 | 2023-01-31 | 昆明理工大学 | Preparation method of gallium salt |
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