A method for recovering fluorine from a high-acid, high-fluoride solution

Abstract

This invention belongs to the field of fluoride-containing wastewater treatment, specifically relating to a method for recovering fluoride from high-acid, high-fluoride solutions. The method involves mixing the high-acid, high-fluoride solution with a first organic phase for a first extraction, yielding a first fluorinated organic phase and a first raffinate. The first raffinate is then mixed with a fluoride-converting agent for a conversion treatment, yielding a conversion solution. The fluoride-converting agent includes a water-soluble boron compound. The B / F molar ratio in the fluoride-converting agent and the first raffinate is 1:2~5. The conversion solution is then mixed with a second organic phase for a second extraction, yielding a second fluorinated organic phase and a defluorinated raffinate. The first and second fluorinated organic phases are then subjected to alkaline back-extraction, either separately or in combination, to obtain a fluoride-containing solution. This method, based on the specific combination of first extraction-conversion-second extraction, can efficiently and selectively recover fluoride from high-acidity, high-fluoride, and complex phase systems.

Description

Technical Field

[0001] This invention belongs to the field of fluoride-containing wastewater resource treatment technology, specifically relating to the fluoride resource recovery of a high-acid, high-fluoride solution system. Background Technology

[0002] Fluorine is widely present in industrial processes such as hydrometallurgy, rare metal smelting, electronic material manufacturing, inorganic salt chemicals, and fluorochemicals. Particularly in tantalum-niobium smelting, nickel-cobalt smelting, boron-based chemicals, new energy material preparation, and electronic-grade chemical production, hydrofluoric acid or fluorine-containing complex systems are commonly used for material decomposition and dissolution, resulting in large quantities of fluoride-containing wastewater. In this type of wastewater, fluorine is primarily present as free fluoride (F). - It exists in the form of HF, fluorine complexes or multiple complex ions, and is characterized by high concentration, complex morphology, strong mobility and great environmental hazard.

[0003] Existing technologies for treating fluoride-containing wastewater mainly include chemical precipitation (lime method, aluminum salt method, iron salt method), adsorption method, membrane separation method, electrochemical method, extraction method, and ion exchange method. For example, patent document CN121735354A discloses a method for separating and recovering fluoride from waste acid solution. The method includes the following steps: S1, take the solution to be treated, add an extractant to extract, and obtain an organic phase and an aqueous phase; the extractant is N235 extractant; S2, add a cerium (III) salt solution as a back-extraction agent to the organic phase, and after separation, recover the cerium fluoride precipitate in the back-extraction solution. Patent document CN121823866A discloses a method for treating high-fluoride wastewater and its application. This method uses low-concentration wastewater from the sulfuric acid process for titanium dioxide production as the acidic medium and phosphate rock as the calcium and phosphorus source. First, an acidic reaction solution containing soluble phosphates is prepared through a dissolution reaction. This solution is then mixed with the high-fluoride wastewater, and after two stages of pH adjustment, calcium fluorophosphate is redeprecipitated, ultimately achieving the removal of high-fluoride wastewater and the resource utilization of the waste acid water. As another example, patent document CN118993412A discloses a method for treating high-fluoride acidic wastewater based on a flotation / seed coupling method. Specifically, ultrasonically flotated sludge is coupled with actual high-fluoride acidic wastewater, using the flotation sludge as a seed crystal to increase the fluoride removal ratio in CaF2 precipitation. The steps include ultrasonic treatment, flotation treatment, acid washing, and seed coupling. In addition, Chinese patent document CN116534963A discloses a defluoridating agent for acidic high-fluoride wastewater, which is composed of the following components: Agent A: calcium aluminate powder, calcium chloride, ferric chloride, potassium dihydrogen phosphate, magnesium chloride, and anionic polyacrylamide; Agent B: aluminum chloride hexahydrate, anionic polyacrylamide, and reverse osmosis concentrate.

[0004] While the aforementioned methods can achieve defluorination to some extent, they generally suffer from low treatment efficiency, poor selectivity, large sludge production, low resource utilization, and high operating costs. Furthermore, for high-fluoride wastewater from different sources, fluoride exists in various forms, making it difficult to adapt defluorination processes and predict the defluorination effect. For example, high-acid, high-fluoride wastewater from tantalum-niobium hydrometallurgical processes presents unique characteristics and treatment challenges compared to fluoride-containing wastewater from general chemical, electroplating, and semiconductor industries: First, this type of wastewater typically originates from the decomposition and leaching of the HF-H2SO4 system and subsequent extraction processes. The system has extremely high acidity (pH ≤ 1), high sulfate concentration, and high ionic strength, resulting in strong corrosiveness and complex system stability. Conventional neutralization and precipitation methods require large amounts of alkaline reagents, significantly increasing treatment costs. Second, the wastewater has a high fluoride content, typically 10–200 g / L, classifying it as high-concentration fluoride-containing resource-based wastewater with significant environmental hazards. However, it also possesses high resource recovery value, placing higher demands on the enrichment capacity and separation depth of the process. Third, fluoride in this type of wastewater is not only in the form of free F - Fluorine exists in the form of HF and forms various stable complexes or complex anions with impurities such as Si, Fe, Al, and Ti. Fluorine exhibits multiple forms, and dynamic transformation equilibrium may exist between different forms, making it difficult to remove. Conventional treatment methods such as precipitation are insufficient for deep defluorination, and direct extraction is also easily limited by the slow transformation of complexed fluorine, leading to a decrease in defluorination efficiency in later stages. Fourth, the wastewater contains a high content of coexisting metal ions, which easily form stable complex structures in high-acid, high-fluorine systems, easily causing impurity co-extraction, organic phase contamination, and accumulation of impurities in the back-extraction solution during the extraction process, further affecting product purity and process stability. Fifth, high-acid, high-salt systems easily cause emulsification, third-phase separation, and other phase separation problems, increasing the difficulty of continuous operation. In summary, the wastewater treated by this invention has characteristics such as "high acidity, high fluorine, high salinity, and complex system," making the efficient separation and resource recovery of fluorine significantly more difficult than that of general fluoride-containing wastewater. There is an urgent need to develop novel recovery processes that can regulate fluorine forms and enhance interphase distribution. Summary of the Invention

[0005] To address the problems of low extraction efficiency, complex and difficult-to-standardize fluoride speciation, difficulty in enrichment and recovery, and low resource utilization in existing high-acid and high-fluoride wastewater treatment technologies, this invention provides a method for recovering fluoride from high-acid and high-fluoride solutions, aiming to efficiently recover fluoride resources from the loaded phase of high-acid and high-fluoride solutions.

[0006] For high-acid, high-fluoride wastewater generated from rare earth metallurgy such as tantalum and niobium, the pH is generally below 1, and it contains a large amount of impurity elements such as Si, Fe, Al, and Ti. These impurity elements usually form stable forms with high fluoride content. The extremely high acidity, high fluoride content, and complex complex forms of this high-acid, high-fluoride wastewater significantly increase the difficulty of fluoride recycling. To address this problem, this invention provides the following improvement solution:

[0007] A method for recovering fluorine from a high-acid, high-fluoride solution, wherein the high-acid, high-fluoride solution is mixed with a first organic phase and subjected to a first extraction to obtain a first fluorine-loaded organic phase and a first raffinate;

[0008] The first raffinate and a fluorine conversion agent are mixed and subjected to conversion treatment to obtain a conversion solution; the fluorine conversion agent includes a water-soluble boron compound; the B / F molar ratio in the fluorine conversion agent and the first raffinate is 1:2~5;

[0009] The transformation solution and the second organic phase were mixed for a second extraction to obtain a second fluorinated organic phase and a defluorinated raffinate.

[0010] The first fluorinated organic phase and the second fluorinated organic phase, either separately or in combination, are subjected to alkaline back-extraction to obtain a fluorinated solution.

[0011] The first organic phase and the second organic phase contain active ingredient A with the structure of Formula 1 and active ingredient B with the structure of Formula 2;

[0012] Formula 1;

[0013] Formula 2;

[0014] R1 and R2 are C3~C on their own. 10 The alkyl group; R3 is a short-chain alkyl or alkoxy group from C1 to C5;

[0015] R4 is C6~C 10 Long-chain alkyl groups;

[0016] pH ≤ 1 in highly acidic and highly fluoride solutions; F - The concentration is 10~200g / L.

[0017] To address the problem of difficult fluoride recovery from high-acid, high-fluoride solutions due to high acidity, high fluoride content, and complex stable complexes, this invention innovatively employs a first extraction with the first organic phase, followed by a transformation-second extraction process. This unique combination of first extraction, transformation, and second extraction can solve the problem of efficient and selective recovery of fluoride from high-acidity, high-fluoride, and complex phase systems.

[0018] In this invention, the high-acid, high-fluoride solution is at least one of tantalum-niobium smelting wastewater and rare metal smelting wastewater;

[0019] The acid anions in the high-acid, high-fluoride solution include sulfate ions;

[0020] Preferably, in a high-acid, high-fluoride solution, the acidity C(H) + ) above 5 mol / L; F - It is 50~200g / L;

[0021] The high-acid, high-fluoride solution also contains at least one metallic element selected from iron, aluminum, silicon, titanium, and nickel.

[0022] Preferably, the component content of the high-acid, high-fluoride solution is: F - 50~200g / L, SO4 2- : 50~800g / L, Fe: 0.010~40g / L, Ti: 0.010~40g / L, Si: 0.010~40g / L; furthermore, F - 100~180g / L, SO4 2- 400~600g / L, Fe: 20~35g / L, Ti: 20~30g / L, Si: 10~20g / L. Acidity C (H + Further, it can be 5~15 mol / L; even further, it can be 10~15 mol / L.

[0023] In this invention, the first organic phase further includes a hydrophobic diluent; the hydrophobic diluent is, for example, sulfonated kerosene.

[0024] In Equation 1, R1 and R2 are individually C6~C 10 R1 is a long-chain alkyl group; R2 is a short-chain alkyl group of C1 to C3. Preferred formulations of Formula 1, consisting of two long-chain alkoxy groups and one short-chain alkyl group, are more suitable for the specific system described in this invention and can achieve better combined F extraction results.

[0025] Preferably, in the first organic phase, the volume content of active ingredient A is 20-80% (preferably 45-75%; more preferably 50-60%); and the volume ratio of active ingredient A to active ingredient B is 5-7:1-2.

[0026] In this invention, the O / A volume ratio in the first extraction process is (10~1):(1~10); it can further be 1~4:1.

[0027] Preferably, the first extraction temperature is 10~60℃; further, it can be room temperature (20±5℃).

[0028] The first extraction time can be adjusted reasonably according to the stratification situation, for example, it can be 1~40 min; further, it can be 5~15 min.

[0029] In this invention, the fluorine conversion agent includes at least one of boric acid (H3BO3), borax (Na2B4O7), or boron oxide (B2O3).

[0030] Furthermore, the B / F molar ratio in the fluorinated conversion agent and the first raffinate is 1:2.5~4; even further, it is 1:3~3.5.

[0031] In this invention, the temperature for the transformation treatment is 15~90℃, preferably 50~70℃;

[0032] Preferably, the conversion reaction time is 10-200 min, and more preferably 30-50 min.

[0033] In this invention, the second organic phase further comprises a hydrophobic diluent;

[0034] Preferably, in the second organic phase, the volume content of active ingredient A is 20-80% (preferably 45-75%; more preferably 50-60%); the volume ratio of active ingredient A to active ingredient B is 5-7:1-2. In this invention, the O / A ratio in the second extraction process is (10-1):(1-10); more preferably it can be 1-4:1.

[0035] Preferably, the second extraction temperature is 10~60℃; further, it can be room temperature (20±5℃).

[0036] Preferably, the second extraction time can be adjusted reasonably according to the stratification situation, for example, it can be 1~40 min.

[0037] In this invention, the alkaline solution is an aqueous solution containing at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, or ammonia.

[0038] Furthermore, the solute concentration of the alkaline solution can be 5~50 g / L; further, it can be 20~45 g / L.

[0039] The ratio of back-extraction is O / A = (10~1): (1~10); it can be further expressed as 1:1~3.

[0040] The organic phase after back-extraction is recycled.

[0041] In this invention, a fluorine-containing solution is neutralized and evaporated to obtain a fluorine-containing compound.

[0042] Beneficial effects

[0043] This invention innovatively employs a first organic phase extraction to treat high-acid, high-fluoride wastewater, followed by a second extraction using a fluoride transforming agent. This unifies the fluoride elements coexisting in the complex wastewater system in both free and multiple complexed states into a form suitable for the second extraction system, eliminating the problem of incomplete extraction caused by the diversity of fluoride forms at the source. This significantly improves the distribution and migration efficiency of fluoride in the extraction system, thereby greatly enhancing the extraction recovery rate and resource utilization level of fluoride. Simultaneously, this method effectively reduces the number of extraction stages and shortens the treatment process, offering advantages such as high separation efficiency, strong selectivity, and process stability, making it suitable for treating complex wastewater with high acidity and high fluoride content. Attached Figure Description

[0044] Figure 1 This is a flowchart of the processing in Example 1. Detailed Implementation

[0045] In the following case, the fluoride-containing wastewater is taken as an example of tantalum-niobium hydrometallurgical extraction wastewater. This wastewater is a highly acidic and highly corrosive solution, in which F... - The concentration of SO4 was 143.93 g / L. 2- 519.62 g / L, Fe 27.05 g / L, Ti 22.65 g / L, Si 13.87 g / L, acidity C (H + =12.83 mol / L;

[0046] As an optional solution, Equation 1 uses Equation 1A as a typical example:

[0047] Formula 1A;

[0048] Formula 2A;

[0049] Example 1

[0050] Step 1: First Extraction

[0051] An appropriate amount of tantalum-niobium hydrometallurgical ore extraction wastewater was taken, and an extractant consisting of Formula 1A, Formula 2A, and sulfonated kerosene in a volume ratio of 6:1:3 was used. The first extraction experiment was conducted under the conditions of O / A = 2, temperature 25℃, and extraction time 10 min.

[0052] The operation result is: raffinate F after extraction - The concentration of SO4 was 108.84 g / L. 2- 393.00 g / L, Fe 24.60 g / L, Ti 20.36 g / L, Si 12.79 g / L. Fluoride ion extraction rate was 24.37%.

[0053] Step 2: First extraction and back-extraction:

[0054] The organic phase obtained from the first extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 28.0 g / L. The back-extraction ratio was O / A = 1:2, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0055] The operation result is that the F of the back-extraction solution - The concentration was 8.76 g / L, and the back-extraction rate was 99.85%.

[0056] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out; a white NaF product is obtained with a NaF content of 97.4 wt%.

[0057] Step 3: Transformation

[0058] Take the raffinate from step 1, add boric acid (H3BO3) as a transforming agent, and control the boron-fluorine molar ratio n(B):n(F) - The ratio of 1:3 was used to stir the reaction at 60 °C for 40 min. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain the fluorinated aqueous phase and filter residue after the transformation treatment.

[0059] The results showed that the filter residue was amorphous silicon, and the aqueous phase was BF4. - The concentration was 165.50 g / L, F - Concentration 1.46 g / L, Fe 22.08 g / L, Ti 19.36 g / L, Si 0.79 g / L;

[0060] Step 4: Second extraction:

[0061] A suitable amount of the conversion feed solution was taken, and an extractant consisting of Formula 1A, Formula 2A, and sulfonated kerosene in a volume ratio of 6:1:3 was used. A five-stage countercurrent cascade experiment was conducted under the conditions of phase O / A=2, temperature 25℃, and extraction time 15 min. The BF4 in the raffinate... - The concentration can be reduced to 1.31 g / L, and the extraction rate can reach 99.21%. - The concentration is 0.014 g / L.

[0062] Step 5: Second back-extraction:

[0063] The organic phase obtained from the second extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 40.0 g / L. The back-extraction ratio was O / A = 1:1, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0064] The result of the operation was that the BF4 in the back-extraction solution... -The concentration was 75.08 g / L, and the back-extraction rate was 99.96%.

[0065] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out; a white NaBF4 product is obtained with a NaBF4 content of 98.9 wt%.

[0066] Example 2

[0067] Compared with Example 1, the only difference is that the volume ratio of Formula 1A, Formula 2A and sulfonated kerosene in the first extraction organic phase of step 1 is changed to 5:2:3; all other operations and parameters are the same as in Example 1.

[0068] The result of step 1 is: raffinate F after extraction. - The concentration of SO4 was 100.12 g / L. 2- 364.52 g / L, Fe 25.67 g / L, Ti 21.66 g / L, Si 12.31 g / L. Fluoride ion extraction rate was 30.44%.

[0069] The result of step 2 is that the F of the back-extraction solution - The concentration was 10.37 g / L, and the back-extraction rate was 94.68%.

[0070] The result of step 3 was that the filter residue was amorphous silicon, and the aqueous phase was BF4. - The concentration was 151.93 g / L, F - Concentration 1.30 g / L, Fe 23.43 g / L, Ti 20.84 g / L, Si 0.69 g / L;

[0071] BF4 in the raffinate from the second extraction in step 4 - The concentration can be reduced to 1.23 g / L, and the extraction rate can reach 99.19%. - The concentration is 0.011 g / L.

[0072] The result of step 5 is the BF4 content of the back-extraction solution. - The concentration was 75.22 g / L, and the back-extraction rate was 99.82%.

[0073] Example 2 shows that, by only changing the composition of the first organic phase in the first extraction stage (Formula 1A: Formula 2A: sulfonated kerosene = 5:2:3), the F- concentration of the raffinate after the first extraction decreased from 143.93 g / L to 100.12 g / L, and the extraction rate reached 30.44%. Further back-extraction with NaOH yielded an F- concentration of 10.37 g / L in the back-extraction solution, with a back-extraction rate of 94.68%, thus producing NaF product. Subsequently, after boric acid conversion and a second extraction, BF4... -The extraction rate can still reach 99.19%, and NaBF4 product can be obtained by back-extraction, which shows that changing the composition ratio of the first organic phase can still maintain the efficient defluorination and resource recovery effect of the process of the present invention.

[0074] Example 3

[0075] Compared with Example 1, the only difference is that the transformation processing temperature in step 3 is replaced with 50 ℃, while the other operations and parameters are the same as in Example 1.

[0076] The result of step 3 was that the filter residue was amorphous silicon, and the aqueous phase was BF4. - The concentration was 156.20 g / L, F - Concentrations: 3.21 g / L, Fe 22.35 g / L, Ti 19.58 g / L, Si 1.05 g / L;

[0077] BF4 in the raffinate from the second extraction in step 4 - The concentration can be reduced to 1.52 g / L, and the extraction rate can reach 99.03%. - The concentration is 0.020 g / L.

[0078] Step 5: The result of the second back-extraction is the BF4 content of the back-extraction solution. - The concentration was 75.88 g / L, and the back-extraction rate was 98.12%.

[0079] Example 3 shows that the process of the present invention still has good applicability and stability within the transformation temperature range defined in the claims.

[0080] Example 4

[0081] Compared with Example 1, the only difference is that in step 4, the volume ratio of Formula 1A, Formula 2A and sulfonated kerosene in the organic phase is changed to 7:1:2 during the second extraction. All other operations and parameters are the same as in Example 1.

[0082] Step 4: BF4 in the raffinate from the second extraction - The concentration can be reduced to 0.98 g / L, and the extraction rate can reach 99.41%. - The concentration is 0.010 g / L.

[0083] Step 5: The result of the second back-extraction operation is that the BF4 content of the back-extraction solution is... - The concentration was 76.10 g / L, and the back-extraction rate was 92.51%.

[0084] As demonstrated in Example 4, by keeping steps 1, 2, 3, and 5 unchanged and only adjusting the organic phase composition ratio in the second extraction stage of step 4 (Formula 1A: Formula 2A: Sulfonated kerosene = 7:1:2), BF4 can still be achieved.- Highly efficient extraction and separation, raffinate BF4 - The concentration can be reduced to 0.98 g / L, and the extraction rate reaches 99.41%, indicating that step 4 of the present invention still has good defluorination ability and stability within different extractant ratio ranges.

[0085] Example 5

[0086] Compared with Example 1, the only difference is that the stripping agent in step 2 (first extraction and stripping) and step 5 (second extraction) is changed from NaOH to KOH solution with the same molar concentration. The process conditions for the remaining steps 1, 3, and 4 are the same as in Example 1.

[0087] Step 2: The result of the first extraction and back-extraction operation is that the F of the back-extraction solution... - The concentration was 8.77 g / L, and the back-extraction rate was 99.94%. An appropriate amount of back-extraction solution was measured and evaporated at 80℃ until white crystals precipitated. The result was a white KF product.

[0088] Step 4: BF4 in the raffinate from the second extraction - The concentration can be reduced to 1.31 g / L, and the extraction rate can reach 99.21%. - The concentration is 0.014 g / L.

[0089] Step 5: BF4 in the second back-extraction solution - The concentration was 75.05 g / L, and the back-extraction rate was 99.95%.

[0090] Take an appropriate amount of back-extraction solution and evaporate it at 80°C until white crystals precipitate; the result is that a white KBF4 product is obtained.

[0091] As demonstrated in Example 5, keeping steps 1, 3, and 4 unchanged, and only replacing the stripping agent in steps 2 and 5 with a KOH solution of the same molar concentration, the entire process still runs smoothly. The first extraction stripping rate in step 2 reaches 99.94%, yielding KF product; the second stripping rate in step 5 reaches 99.95%, yielding KBF4 product. This indicates that this patent has strong adaptability to stripping agents, allowing for flexible selection of either NaOH or KOH as the stripping agent according to actual needs. Both can achieve efficient recovery of fluorine resources and prepare corresponding sodium or potassium salt products, respectively. The product scheme is flexible and has high resource utilization value.

[0092] Example 6

[0093] Compared with Example 1, the only difference is that in steps 1 and 4, Formula 1B is used ( Replacement 1A, with other operations and parameters the same as in Example 1.

[0094] Step 1: First Extraction

[0095] Take an appropriate amount of tantalum-niobium hydrometallurgical ore extraction wastewater, in which free fluoride ions (F...) are present. - The concentration was 143.93 g / L. The extractant composition was Formula 1B, Formula 2A, and sulfonated kerosene, with a volume ratio of 6:1:3. The first extraction experiment was conducted under the conditions of O / A=2, temperature 25℃, and extraction time 10 min.

[0096] The operation result is: raffinate F after extraction - The concentration of SO4 was 115.27 g / L. 2- 413.20 g / L, Fe 25.63 g / L, Ti 21.77 g / L, Si 13.41 g / L. Fluoride ion extraction rate was 19.91%.

[0097] Step 2: First extraction and back-extraction:

[0098] The organic phase obtained from the first extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 28.0 g / L. The back-extraction ratio was O / A = 1:2, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0099] The result of the operation was that F in the back-extraction solution - The concentration was 7.15 g / L, and the back-extraction rate was 99.79%.

[0100] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out.

[0101] The result of the operation was a white NaF product.

[0102] Step 3: Transformation

[0103] Take the raffinate from step 1, wherein the raffinate F after extraction - The concentration of SO4 was 115.27 g / L. 2- 413.20 g / L, Fe 25.63 g / L, Ti 21.77 g / L, Si 13.41 g / L. Boric acid (H3BO3) was added to the wastewater as a transforming agent, and the boron-fluorine molar ratio n(B):n(F) was controlled. - The ratio of 1:3 was used to stir the reaction at 60 °C for 40 min. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain the fluorinated aqueous phase and filter residue after the transformation treatment.

[0104] The results showed that the filter residue was amorphous silicon, and the aqueous phase was BF4. - The concentration was 172.36 g / L, F -The concentrations were 2.03 g / L, Fe 24.78 g / L, Ti 20.36 g / L, and Si 0.81 g / L;

[0105] Step 4: Second extraction:

[0106] A suitable amount of the conversion feed solution was taken, and an extractant consisting of Formula 1B, Formula 2A, and sulfonated kerosene in a volume ratio of 6:1:3 was used. A five-stage countercurrent cascade experiment was conducted under the conditions of O / A = 2, temperature 25℃, and extraction time 15 min. The BF4 in the raffinate... - The concentration can be reduced to 4.76 g / L, and the extraction rate can reach 97.24%. - The concentration is 0.089 g / L.

[0107] Step 5: Second back-extraction:

[0108] The organic phase obtained from the second extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 40.0 g / L. The back-extraction ratio was O / A = 1:1, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0109] The result of the operation was that the BF4 in the back-extraction solution... - The concentration was 82.81 g / L, and the back-extraction rate was 98.81%.

[0110] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out.

[0111] The result of the operation was a white NaBF4 product.

[0112] Example 7

[0113] Compared with Example 1, the only difference is that in the first organic phase, the volume ratio of Formula 1A, Formula 2A, and sulfonated kerosene is 3:0.5:6.5; and in the second organic phase, the volume ratio of Formula 1A, Formula 2A, and sulfonated kerosene is 4:1:5. All other operations and parameters are the same as in Example 1. The results are as follows:

[0114] Step 1: First Extraction

[0115] An appropriate amount of tantalum-niobium hydrometallurgical extraction wastewater was taken, with the volume ratio of Formula 1A, Formula 2A, and sulfonated kerosene at 3:0.5:6.5. The first extraction experiment was conducted under the conditions of O / A = 2, temperature 25℃, and extraction time 10 min.

[0116] The operation result is: raffinate F after extraction - The concentration of SO4 was 124.56 g / L. 2-426.45 g / L, Fe 26.67 g / L, Ti 21.63 g / L, Si 13.11 g / L. Fluoride ion extraction rate was 13.46%.

[0117] Step 2: First extraction and back-extraction:

[0118] The organic phase obtained from the first extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 28.0 g / L. The back-extraction ratio was O / A = 1:2, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0119] The operation result is that the F of the back-extraction solution - The concentration was 4.84 g / L, and the back-extraction rate was 99.95%.

[0120] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out; a white NaF product is obtained.

[0121] Step 3: Transformation

[0122] Take the raffinate from step 1, add boric acid (H3BO3) as a transforming agent, and control the boron-fluorine molar ratio n(B):n(F) - The ratio of 1:3 was used to stir the reaction at 60 °C for 40 min. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain the fluorinated aqueous phase and filter residue after the transformation treatment.

[0123] The results showed that the filter residue was amorphous silicon, and the aqueous phase was BF4. - The concentration was 189.45 g / L, F - Concentrations: 1.87 g / L, Fe 23.95 g / L, Ti 20.57 g / L, Si 0.81 g / L;

[0124] Step 4: Second extraction:

[0125] Take an appropriate amount of the conversion feed solution and use an extractant with a volume ratio of Formula 1A, Formula 2A, and sulfonated kerosene of 4:1:5. Conduct a 5-stage countercurrent cascade experiment under the conditions of O / A=2, temperature 25℃, and extraction time 15 min. The BF4 in the raffinate... - The concentration can be reduced to 9.56 g / L, and the extraction rate can reach 94.95%. - The concentration is 0.042 g / L.

[0126] Step 5: Second back-extraction:

[0127] The organic phase obtained from the second extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 40.0 g / L. The back-extraction ratio was O / A = 1:1, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0128] The result of the operation was that the BF4 in the back-extraction solution... - The concentration was 85.93 g / L, and the back-extraction rate was 95.54%.

[0129] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out; a white NaBF4 product is obtained.

[0130] Example 7 shows that the total content of active ingredients in the organic phase is a key factor affecting the extraction and back-extraction efficiency. Within the preferred ratio range defined in the claims, the process of the present invention can achieve the best synergistic extraction effect. Deviating from this range will lead to a comprehensive decrease in efficiency at each stage and a significant weakening of the deep defluorination effect.

[0131] Comparative Example 1

[0132] Compared with Example 1, the only difference is that steps 1 and 2 are not performed. The wastewater is directly treated in step 3 and subsequent processes. All other operations and parameters are the same as in Example 1.

[0133] Step 3: Transformation

[0134] Boric acid (H3BO3) was added to the wastewater from the hydrometallurgical extraction of tantalum and niobium as a transforming agent, and the boron-fluorine molar ratio n(B):n(F) was controlled. - The ratio of 1:3 was used to stir the reaction at 60 °C for 40 min. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain the fluorinated aqueous phase and filter residue after the transformation treatment.

[0135] The results showed that the filter residue consisted of amorphous silicon, partially undissolved boric acid, and BF4 in the aqueous phase. - The concentration was 178.51 g / L, F - The concentrations were 49.36 g / L, Fe 22.15 g / L, Ti 19.06 g / L, and Si 4.61 g / L;

[0136] Step 4: Extraction:

[0137] A suitable amount of the conversion feed solution was taken, and an extractant consisting of Formula 1A, Formula 2A, and sulfonated kerosene in a volume ratio of 6:1:3 was used. A five-stage countercurrent cascade experiment was conducted under the conditions of phase O / A=2, temperature 25℃, and extraction time 15 min. The BF4 in the raffinate... - The concentration was reduced to 22.35 g / L, and the extraction rate reached 87.48%. - The concentration was 38.74 g / L.

[0138] Scheme B uses a large amount of material, and it is difficult to effectively promote the high-selectivity transformation of highly complex F, which is detrimental to subsequent extraction.

[0139] Comparative Example 2

[0140] Compared with Example 1, the only difference is that the wastewater raw liquid is pre-treated by the transformation process in step 3, and then the first extraction in step 1, the first extraction back-extraction in step 2, the second extraction in step 4, and the second back-extraction in step 5 are performed in sequence according to the conditions of Example 1. All other operations and parameters are the same as in Example 1.

[0141] Step 3: Transformation

[0142] Taking a suitable amount of tantalum-niobium hydrometallurgical ore extraction wastewater as an example, this wastewater is a highly acidic and highly corrosive solution, in which F - The concentration of SO4 was 143.93 g / L. 2- 519.62 g / L, Fe 27.05 g / L, Ti 22.65 g / L, Si 13.87 g / L. Boric acid (H3BO3) was added to the wastewater as a transforming agent, and the boron-fluorine molar ratio n(B):n(F) was controlled. - The ratio of 1:3 was used to stir the reaction at 60 °C for 40 min. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain the fluorinated aqueous phase and filter residue after the transformation treatment.

[0143] The results showed that the filter residue consisted of amorphous silicon, partially undissolved boric acid, and BF4 in the aqueous phase. - The concentration was 178.51 g / L, F - Concentrations: 49.36 g / L, Fe 21.63 g / L, Ti 18.24 g / L, Si 4.61 g / L;

[0144] Step 1: First Extraction

[0145] Take an appropriate amount of the transformation solution and use an extractant composed of Formula 1A, Formula 2A, and sulfonated kerosene in a volume ratio of 6:1:3. Conduct the first extraction experiment under the conditions of O / A = 2, temperature 25℃, and extraction time 10 min.

[0146] The operation result was: BF4 in the raffinate after extraction. - It is 122.46 g / L, F - 46.85 g / L, Fe 20.60 g / L, Ti18.36 g / L, Si 4.51 g / L. BF4 - The extraction rate was 31.40%, F - The extraction rate was 5.09%.

[0147] Step 2: First extraction and back-extraction:

[0148] The organic phase obtained from the first extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 28.0 g / L. The back-extraction ratio was O / A = 1:2, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0149] The result of the operation was that the BF4 in the back-extraction solution... - The concentration was 14.03 g / L, and the F of the back-extraction solution was... - The concentration was 0.63 g / L;

[0150] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out;

[0151] The result of the operation was a white mixed product of NaF and NaBF4.

[0152] Step 4: Second extraction:

[0153] Take an appropriate amount of the raffinate after the first extraction; the raffinate after extraction is BF4. - It is 122.46 g / L, F - The extract contained 46.85 g / L Fe, 20.60 g / L Ti, 18.36 g / L Si, and 4.51 g / L. An extractant composition of Formula 1A, Formula 2A, and sulfonated kerosene was used, with a volume ratio of 6:1:3. A five-stage countercurrent cascade experiment was conducted under the conditions of O / A=2, temperature 25℃, and extraction time 15 min. The BF4 in the raffinate... - The concentration can be reduced to 9.80 g / L, and the extraction rate can reach 91.99%. - The concentration was 37.50 g / L.

[0154] Step 5: Second back-extraction:

[0155] Step 4 involves reacting with an alkaline back-extraction agent, NaOH, at a concentration of 40.0 g / L. The back-extraction ratio is O / A = 1:1, the back-extraction temperature is 25 ℃, and the back-extraction time is 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase are obtained.

[0156] The result of the operation was that the BF4 in the back-extraction solution... - The concentration was 56.30 g / L, and the back-extraction rate was 99.94%.

[0157] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out;

[0158] The result of the operation was the acquisition of white NaF and NaBF4 products.

[0159] Comparative Example 2, which pre-converts the wastewater by converting it entirely with boric acid before performing two-stage extraction, has several drawbacks compared to Example 1. Firstly, the pre-conversion process leads to incomplete conversion. Because the wastewater has not undergone the first extraction, the fluoride concentration is high, with a large amount existing in both free and stable complexed states with Si, Fe, and Ti. Boric acid must simultaneously compete with multiple forms of fluoride for reaction, resulting in a complex system and limited kinetics. Furthermore, the conversion residue contains not only amorphous silicon but also some undissolved boric acid, leading to a fluoride conversion rate far lower than that of Example 1 after the first extraction. Secondly, the incomplete conversion completely negates the process's ability to recover different components. Steps 1 and 5 extract HBF4 and a small amount of F instead of pure free HF. - The mixture, in step 2, yielded a mixed crystal of NaBF4 and NaF instead of pure NaF product through back-extraction, thus failing to achieve the pure NaF preparation described in Example 1; BF4 - Extraction rate decreased significantly, raffinate BF4 - and F - All values ​​were significantly too high, resulting in complete failure of deep defluorination. Thirdly, steps 1 and 4 both involve HBF4 extraction, while steps 2 and 5 involve back-extraction. The two extraction-back-extraction units have overlapping functions, yet both cannot operate efficiently due to incomplete transformation, indicating significant process redundancy. The above comparison clearly demonstrates that the first extraction must remove free HF to create a favorable chemical environment for subsequent boric acid transformation, thus achieving thorough transformation and efficient extraction. Comparative Example 2, by disrupting the transformation sequence, resulted in incomplete transformation, failed fractional recovery, and ineffective deep defluorination, effectively demonstrating the scientific nature and irreplaceable nature of the process sequence design in this invention.

[0160] Comparative Example 3

[0161] Compared with Example 1, the only difference is that step 3 transformation processing was not performed, and the raffinate from step 1 was directly processed in step 4 and subsequent processing.

[0162] Step 4: Second extraction:

[0163] Take the first raffinate from step 1, its composition is F - The concentration of SO4 was 108.84 g / L. 2- The concentrations of Fe, Ti, and Si were 393.00 g / L, 24.60 g / L, 20.36 g / L, and 12.79 g / L, respectively. An extractant composition of Formula 1A, Formula 2A, and sulfonated kerosene was used, with a volume ratio of 6:1:3. A five-stage countercurrent cascade experiment was conducted under the conditions of O / A=2, temperature 25℃, and extraction time 15 min. The F in the raffinate... - When the concentration was reduced to 42.65 g / L, the extraction rate could only reach 51.62%.

[0164] Step 5: Second extraction and back-extraction:

[0165] The organic phase obtained from the second extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 40.0 g / L. The back-extraction ratio was O / A = 1:1, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0166] The operation result is that the F of the back-extraction solution - The concentration was 27.10 g / L, and the back-extraction rate was 81.88%.

[0167] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out.

[0168] The result of the operation was a white NaF product.

[0169] Comparative Example 3 did not undergo boric acid conversion, thus failing to uniformly transform the multi-impurity stable system in the wastewater into BF4 with a simple structure and low hydration energy. - The morphology of fluorine cannot fundamentally eliminate the extraction kinetic bottlenecks and thermodynamic limits caused by the diversity of fluorine forms, making it impossible for the extraction process to achieve deep defluorination.

[0170] The above comparison fully demonstrates that the first extraction to improve the feed liquid environment and the subsequent introduction of boric acid conversion step in Embodiment 1 of the present invention is a key technical means to achieve deep defluorination and diversified product recovery. It has significant advanced and technical advantages in terms of defluorination depth, process efficiency and resource utilization level.

[0171] Comparative Example 4

[0172] Compared with Example 1, the only difference is that Formula 2A is not added in steps 1 and 4, while the other operations and parameters are the same as in Example 1.

[0173] Step 1: First Extraction

[0174] Take an appropriate amount of tantalum-niobium hydrometallurgical ore extraction wastewater, in which free fluoride ions (F...) are present. - The concentration was 143.93 g / L. The extractant composition was Formula 1A and sulfonated kerosene, with a volume ratio of 6:4. The first extraction experiment was conducted under the conditions of O / A = 2, temperature 25℃, and extraction time 10 min.

[0175] The results were: the phase separation time was prolonged, and the raffinate F after extraction was... - The concentration of SO4 was 112.56 g / L. 2- 417.51 ​​g / L, Fe 22.41 g / L, Ti 21.61 g / L, Si 12.47 g / L. Fluoride ion extraction rate was 21.79%.

[0176] Step 2: First extraction and back-extraction:

[0177] The organic phase obtained from the first extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 28.0 g / L. The back-extraction ratio was O / A = 1:2, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0178] The operation result is that the F of the back-extraction solution - The concentration was 7.76 g / L, and the back-extraction rate was 98.95%.

[0179] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out.

[0180] The result of the operation was a white NaF product.

[0181] Step 3: Transformation

[0182] Take the raffinate from step 1, and extract the raffinate F. - The concentration of SO4 was 112.56 g / L. 2- 417.51 ​​g / L, Fe 22.41 g / L, Ti 21.61 g / L, Si 12.47 g / L. Boric acid (H3BO3) was added to the wastewater as a transforming agent, and the boron-fluorine molar ratio n(B):n(F) was controlled. - The ratio of 1:3 was used to stir the reaction at 60 °C for 40 min. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain the fluorinated aqueous phase and filter residue after the transformation treatment.

[0183] The results showed that the filter residue was amorphous silicon, and the aqueous phase was BF4. - The concentration was 169.24 g / L, F - Concentration 1.89 g / L, Fe 22.18 g / L, Ti 21.36 g / L, Si 0.88 g / L;

[0184] Step 4: Second extraction:

[0185] A suitable amount of the conversion feed solution was taken, and an extractant consisting of Formula 1A and sulfonated kerosene in a volume ratio of 6:4 was used. A five-stage countercurrent cascade experiment was conducted under the conditions of phase O / A = 2, temperature 25℃, and extraction time 15 min. With prolonged phase separation time, the BF4 in the raffinate... - The concentration was reduced to 3.52 g / L, and the extraction rate reached 97.92%. - The concentration is 0.879 g / L.

[0186] Step 5: Second back-extraction:

[0187] The organic phase obtained from the second extraction was mixed with an alkaline back-extraction agent NaOH at a concentration of 40.0 g / L. The back-extraction ratio was O / A = 1:1, the back-extraction temperature was 25 ℃, and the back-extraction time was 10 min. After standing and phase separation, the back-extraction solution and the regenerated organic phase were obtained.

[0188] The result of the operation was that the BF4 in the back-extraction solution... - The concentration was 82.16 g / L, and the back-extraction rate was 99.15%.

[0189] Take an appropriate amount of the back-extraction solution and evaporate it at 80°C until white crystals precipitate out.

[0190] The result of the operation was a white NaBF4 product.

[0191] As can be seen from Example 1 and Comparative Example 4, the synergistic extraction system of Formula 1A and Formula 2A used in this invention is not a simple superposition of two components, but an organic combination of hydrogen bond synergistic association and solvation effect regulation, which produces a significant synergistic effect. The addition of Formula 2A plays an irreplaceable key role in achieving high extraction rate, deep defluorination and high product yield in the whole process.

[0192] Comparative Example 5

[0193] Compared with Example 1, the difference is that the high-acid and high-fluoride wastewater from tantalum and niobium smelting is directly subjected to multi-stage cross-flow extraction treatment without subsequent transformation, second extraction and back-extraction steps. All other operations and parameters are the same as in Example 1.

[0194] Step 1: Cross-flow extraction:

[0195] An appropriate amount of tantalum-niobium hydrometallurgical extraction wastewater was taken, and an extractant consisting of Formula 1A, Formula 2A, and sulfonated kerosene in a volume ratio of 6:1:3 was used. Cross-flow extraction experiments were conducted under the conditions of O / A = 2, temperature 25℃, and extraction time 10 min.

[0196] The operation result is:

[0197]

[0198] Comparative Example 5 used direct multi-stage cross-flow extraction to treat high-acid, high-fluoride wastewater from tantalum and niobium smelting. Although it showed some defluorination effect in the initial stages, the defluorination efficiency decreased sharply with the increase of extraction stages. After 12 stages of cross-flow extraction, the raffinate F... -The concentration remained high at 6.70 g / L and could not be reduced further, indicating incomplete defluorination. The root cause of this result lies in the coexistence of fluoride in the wastewater in both free and various stable complexed states. It is speculated that the slow dissociation and transformation of the complexed fluoride is the kinetic bottleneck of the entire process. Example 1, through an innovative segmented process, first recovers easily extractable free HF using a first extraction to prepare NaF product, and then uses a boric acid conversion reaction to uniformly convert the remaining difficult-to-extract complexed fluoride into BF4, which has a simple structure and low hydration energy. - The chemical transformation method employed in this invention fundamentally eliminates the limitations imposed on the extraction process by the diversity of fluorine forms. The above comparison clearly demonstrates that simply increasing the number of extraction stages cannot overcome the fundamental constraint of fluorine form diversity in complex systems. The key innovation in achieving deep defluorination and efficient resource recovery lies in the chemical form transformation method employed in this invention.

Claims

1. A method for recovering fluorine from a high-acid, high-fluoride solution, characterized in that, A high-acid, high-fluoride solution is mixed with a first organic phase for a first extraction to obtain a first fluoride-loaded organic phase and a first raffinate. The first raffinate and a fluorine conversion agent are mixed and subjected to conversion treatment to obtain a conversion solution; the fluorine conversion agent includes a water-soluble boron compound; the B / F molar ratio in the fluorine conversion agent and the first raffinate is 1:2~5; The transformation solution and the second organic phase were mixed for a second extraction to obtain a second fluorinated organic phase and a defluorinated raffinate. The first fluorinated organic phase and the second fluorinated organic phase, either separately or in combination, are subjected to alkaline back-extraction to obtain a fluorinated solution. The first organic phase and the second organic phase contain active ingredient A with the structure of Formula 1 and active ingredient B with the structure of Formula 2; Formula 1; Formula 2; R1 and R2 are C3~C on their own. 10 The alkyl group; R3 is a short-chain alkyl or alkoxy group from C1 to C5; R4 is C6~C 10 Long-chain alkyl groups; pH ≤ 1 in highly acidic and highly fluoride solutions; F - The concentration is 10~200g / L.

2. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, The high-acid, high-fluoride solution is at least one of the following: tantalum and niobium smelting wastewater and rare metal smelting wastewater; The acid anions in the high-acid, high-fluoride solution include sulfate ions; The high-acid, high-fluoride solution contains at least one metallic element selected from iron, aluminum, silicon, titanium, and nickel. Preferably, in a high-acid, high-fluoride solution, F - 50~200g / L; acidity C (H + (Above 5 mol / L) Preferably, the component content of the high-acid, high-fluoride solution is: F - 50~200g / L, SO4 2- Fe: 50~800 g / L, Ti: 0.010~40 g / L, Si: 0.010~40 g / L; More preferably, F - 100~180g / L, SO4 2- : 200~600g / L, Fe: 20~35g / L, Ti: 20~30g / L, Si: 10~20g / L; Acidity C (H + The concentration is 5~15 mol / L.

3. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, In Equation 1, R1 and R2 are individually C6~C 10 R3 is a long-chain alkyl group; R3 is a short-chain alkyl group from C1 to C3. The first organic phase also contains a hydrophobic diluent; Preferably, in the first organic phase, the volume content of active ingredient A is 20-80%, more preferably 45-75%; the volume ratio of active ingredient A to active ingredient B is 5-7:1-2.

4. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, The O / A volume ratio in the first extraction process is (10~1):(1~10). Preferably, the first extraction temperature is 10~60℃; Preferably, the first extraction time is 1 to 40 minutes.

5. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, Fluorine conversion agents include at least one of boric acid (H3BO3), borax (Na2B4O7), or boron oxide (B2O3).

6. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, The temperature for the transformation treatment is 15~90℃, preferably 50~70℃; Preferably, the transformation reaction time is 10~200 min.

7. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, The second organic phase also contains a hydrophobic diluent; Preferably, in the second organic phase, the volume content of active ingredient A is 20-80%, more preferably 45-75%; the volume ratio of active ingredient A to active ingredient B is 5-7:1-2.

8. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, In the second extraction process, O / A = (10~1): (1~10); Preferably, the second extraction temperature is 10~60℃; Preferably, the second extraction time is 1 to 40 minutes.

9. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, The alkaline solution is an aqueous solution containing at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, or ammonia. The ratio of back-extraction is O / A = (10~1): (1~10); The organic phase after back-extraction is recycled.

10. The method for recovering fluoride from a high-acid, high-fluoride solution as described in claim 1, characterized in that, Fluorine-containing solutions are neutralized and evaporated to obtain fluorine-containing compounds.

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