A method for recovering fluorine and triethylamine from fluorine-containing organic wastewater

Abstract

The application discloses a method for recovering fluorine and triethylamine from fluorine-containing organic wastewater, and belongs to the technical field of fluoride preparation. The method adopts the synergistic effect of an organic phase of an extractant A and an extractant B under the condition that the pH is 0.5-4, realizes selective extraction of fluorine ions and inhibition of extraction of metal impurity cations under the premise that water-soluble triethylamine is not extracted through a one-step liquid-liquid extraction process, thereby realizing efficient and low-loss recovery of fluorine and triethylamine, and further preparing high-purity fluorides and triethylamine. The method has the advantages of short process, no need of complicated impurity removal process, high fluorine recovery rate, low production cost and the like.

Description

Technical Field

[0001] This invention relates to a method for fluorine recovery in complex environments, specifically a method for recovering fluorine and triethylamine from fluoride-containing organic wastewater, belonging to the field of fluoride preparation technology. Background Technology

[0002] In continuous production processes such as hydrometallurgy, battery material precursor preparation, and high-purity electrolyte production, a certain amount of byproduct solutions with strong corrosiveness and high organic load are often generated. This is especially true in fluoride-containing salt systems, intermediate preparation steps of battery-grade electrolytes, or the regeneration process of metal leaching solutions, where large amounts of fluoride (F...) are produced. - Hydrogen fluoride (HF) and triethylamine (TEA) introduced during the process will simultaneously accumulate in the circulating liquid or mother liquor, giving the solution a complex system characteristic of high fluoride and high amine content. Hydrogen fluoride is extremely corrosive and can rapidly corrode traditional equipment materials such as stainless steel, titanium, and fluoroplastic linings; while TEA, as a highly polar, strongly alkaline, and easily emulsified organic amine, will react with metal ions, acid radicals, or extractants in the system, causing a series of engineering problems such as difficulty in phase separation, decreased electrodeposition performance, and increased difficulty in wastewater treatment. These by-product solutions not only affect the stable operation of the production system but also pose a high risk of environmental emissions; therefore, they must be deeply purified before entering subsequent processes.

[0003] Traditional defluorination and deamine removal technologies, such as lime precipitation, magnesium salt precipitation, ion exchange adsorption, strong acid neutralization, or air stripping, while capable of removing single impurities in some systems, often perform poorly in highly corrosive solutions containing both fluorides and organic amines. On one hand, precipitation methods struggle to achieve high-efficiency defluorination in strong acids or systems containing large amounts of complexes, and the small particle size of the precipitate easily forms colloids, making solid-liquid separation difficult. On the other hand, TEA (tetrafluoroethylene glycol) is highly alkaline and can react with precipitants, adsorbents, or extractants, disrupting the separation interface and inducing emulsification, leading to the formation of a third phase or a stable foam layer, thus rendering traditional processes unsuitable. Furthermore, the simultaneous treatment of fluorides and organic amines... - The multi-stage chemical neutralization or dosing method of / HF and TEA is not only complex and energy-intensive, but may also introduce new inorganic salts or organic pollutants.

[0004] Therefore, developing green purification processes that can achieve simultaneous and efficient removal of fluorine and organic amines under mild conditions has become an urgent need. Summary of the Invention

[0005] To address the problems faced by existing fluoride recovery processes, the present invention aims to provide a method for recovering fluoride and triethylamine (TEA) from fluoride-containing organic wastewater. This method utilizes the synergistic effect of extractant A and extractant B to selectively extract fluoride ions and inhibit the extraction of metal impurity cations without extracting water-soluble triethylamine. This achieves efficient and low-loss recovery of fluoride and triethylamine, and further prepares high-purity fluorides and triethylamine.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a method for recovering fluorine and triethylamine from fluoride-containing organic wastewater, the method comprising the following steps:

[0007] S1 uses an organic phase containing extractant A and extractant B to extract fluoride-containing organic wastewater under an acidic environment, obtaining a raffinate containing water-soluble triethylamine and metal impurity ions and a fluoride-loaded organic phase; the fluoride-containing organic wastewater contains fluoride ions, metal impurity ions and water-soluble triethylamine.

[0008] The extractant A has the structure of Formula 1:

[0009] ;

[0010] Formula 1;

[0011] The extractant B has the structure of Formula 2:

[0012] ;

[0013] Formula 2;

[0014] Among them, R1, R2, and R3 are independently selected from C3 to C4. 12 The alkyl group can be a straight-chain alkyl group or a branched alkyl group, such as propyl, heptyl, hexyl, isobutyl, etc.

[0015] S2 back-extracts and evaporates the fluorinated organic phase to obtain fluoride; the raffinate containing water-soluble triethylamine and metal impurity ions is then distilled to recover triethylamine.

[0016] This invention utilizes the synergistic effect of extractant A and extractant B to achieve the recovery of fluoride and triethylamine from fluoride-containing organic wastewater through a one-step liquid-liquid extraction process. Furthermore, combined back-extraction and distillation further enable the preparation of high-purity fluorides and triethylamine. Specifically, extractant A is a tertiary amine compound that undergoes protonation under acidic conditions to form a positively charged ammonium cation. Fluoride ions in the solution can combine with the protonated tertiary amine to form hydrophobic ion pairs, thus being preferentially extracted into the organic phase. While water-soluble triethylamine is also a tertiary amine, its short alkyl chain and strong hydrophilicity make it difficult to stably form ion pairs in the organic phase, and therefore it is not extracted. In addition, extractant B is a neutral phosphorus / oxygen / ester complexing agent. When used alone, its moderate complexing strength and relatively large steric hindrance result in a low extraction rate for fluoride ions, but its unique structure exhibits strong repulsion against metal impurity ions. When extractant B is mixed with extractant A, extractant B interacts with the ammonium cation in the ion pair through the oxygen atom of its P=O bond, while the dipole of P=O also interacts with fluoride ions, forming a more stable ternary complex. This significantly enhances the hydrophobicity and stability of the ion pair in the organic phase, greatly improving the extraction and distribution ratio of fluoride ions. Furthermore, the mixed extractants alter the polarity and spatial configuration of the organic phase, more effectively suppressing the co-extraction of water-soluble triethylamine and cations such as calcium, magnesium, iron, sodium, and potassium, thereby further improving the efficiency of selective separation. Subsequently, efficient removal and recovery of triethylamine are achieved through distillation, and the resulting fluorinated organic phase can be directly used to prepare high-purity fluorides, such as ammonium fluoride, greatly shortening the process flow for recovering fluoride from fluoride-containing organic wastewater and saving production input costs.

[0017] The length of the alkyl chain in R1 affects the hydrophobicity of extractant A. Increased alkyl side chain length enhances hydrophobicity and reduces water solubility, which is beneficial for improving fluoride ion extraction efficiency. However, excessively long side chains increase the viscosity and steric hindrance of the organic phase. Conversely, increased alkyl chains in R2 and R3 improve hydrophobicity, making them easier to retain in the organic phase and improving the stability of the complex. However, excessively long side chains hinder phase separation. Therefore, further optimization involves selecting R1, R2, and R3 independently from C8 to C4. 12 Alkyl groups.

[0018] As a preferred embodiment, the fluoride-containing organic wastewater contains 40-60 g / L of fluoride ions, 60-85 g / L of water-soluble triethylamine, and 0.1-10 g / L of metal impurity ions. The method of this invention can achieve excellent separation results even for wastewater with high fluoride and high organic concentrations, and has high application value.

[0019] As a preferred embodiment, the metal impurity ions include at least one selected from iron ions, calcium ions, magnesium ions, sodium ions, cobalt ions, and potassium ions. The wastewater of this invention can contain various metal impurity cations. Considering the type of fluoride-containing organic wastewater and its recovery efficiency and value, the fluoride-containing organic wastewater of this invention can be derived from electrolyte by-product wastewater.

[0020] As a preferred embodiment, the total volume concentration of extractants A and B in the organic phase containing extractant A and extractant B is 10-70%. Lower concentrations of extractants A and B in the organic phase require more organic phase, resulting in lower extraction efficiency. Conversely, excessively high concentrations of extractants A and B in the organic phase prevent effective extraction. More preferably, the total volume concentration of extractants A and B in the organic phase is 50-60%.

[0021] As a preferred embodiment, the organic phase containing extractant A and extractant B further contains a hydrophobic solvent.

[0022] As a preferred embodiment, the volume ratio of extractant A to extractant B is (5~35):(5~35). When extractant A accounts for a larger proportion, although its extraction capacity for fluoride ions is strong, the lack of sufficient extractant B to form a stable ternary complex reduces the stability of the ion pair formed by fluoride ions and protonated tertiary amine in the organic phase, resulting in a limited increase in the extraction distribution ratio of fluoride ions. Simultaneously, the repulsion effect on metal impurity ions is weakened, leading to the co-extraction of some metal ions. Conversely, when extractant B accounts for a larger proportion, its extraction rate for fluoride ions alone is low. Although it effectively repels metal impurity ions, the overall extraction efficiency of fluoride ions is significantly reduced, making efficient fluoride recovery impossible. Therefore, rationally controlling the volume ratio of extractant A to extractant B can fully leverage their synergistic effect, ensuring a high extraction rate of fluoride ions while effectively suppressing the co-extraction of metal impurity ions, thereby achieving efficient separation of fluoride from triethylamine and metal impurity ions. More preferably, the volume ratio of extractant A to extractant B is (25~30):(25~30).

[0023] As a preferred embodiment, the hydrophobic solvent includes at least one of kerosene, sulfonated kerosene, D60 solvent oil, and 200# kerosene.

[0024] As a preferred embodiment, in S1, the extraction conditions are: pH 0.5–4, O / A ratio of (1–5):1, extraction temperature 15–60°C, and extraction time 1–10 min. Extraction under acidic conditions promotes the protonation of extractant A, thereby achieving a synergistic extraction effect. More preferably, the extraction pH is 2.5–3, and the O / A ratio is (3–4):1. In the extraction process of this invention, when the O / A ratio increases, i.e., the volume of the organic phase increases relative to the aqueous phase, more extractant molecules can bind with fluoride ions, thereby increasing the fluoride ion extraction rate. However, this also increases the amount of organic phase used and subsequent processing costs. Conversely, when the O / A ratio is too small, the number of extractant molecules in the organic phase is relatively insufficient, resulting in incomplete extraction of fluoride ions and a decrease in extraction efficiency.

[0025] All ratios mentioned in this invention are volume ratios.

[0026] As a preferred embodiment, in S1, the extraction method employs at least one of single-stage extraction, multi-stage countercurrent extraction, multi-stage co-current extraction, multi-stage cross-current extraction, and fractional extraction.

[0027] The present invention provides an extraction method for fluoride-containing organic wastewater. By selecting a preferred extractant and optimizing conditions such as solution pH, extractant concentration, and phase ratio, the method can achieve efficient and highly selective extraction of fluoride ions and inhibit the extraction of high-valence metal ions such as calcium, magnesium, iron, potassium, and sodium, as well as triethylamine, thereby achieving selective separation of fluoride from metal impurity ions and triethylamine.

[0028] As a preferred embodiment, in S2, the back-extraction conditions are: an O / A ratio of (1~8):(2~1), a temperature of 20~40℃, and a pH of 6~8. When the pH of the back-extraction system is low, the back-extractant becomes insufficiently alkaline, making it difficult to effectively neutralize the protonated extractant A in the fluorinated organic phase. This prevents fluoride ions from being released from the ion pair, resulting in reduced back-extraction efficiency. Conversely, when the pH is too high, the hydroxide ion concentration in the back-extractant is too high, leading to irreversible chemical changes in the extractant's molecular structure, reducing the regeneration efficiency of the organic phase and affecting its recyclability. Furthermore, the selection of the O / A ratio needs to balance back-extraction efficiency and the concentration of fluoride ions in the back-extraction solution. When the O / A ratio increases (i.e., the relative volume of the organic phase increases), a unit volume of aqueous phase needs to process more loaded organic phase, resulting in incomplete back-extraction and an increase in the amount of fluoride ions remaining in the organic phase, thus reducing back-extraction efficiency. However, this will increase the concentration of fluoride ions in the back-extraction solution. When the O / A ratio decreases, the relative capacity of water to hold fluoride ions increases, which is beneficial for the transfer of fluoride ions from the organic phase and can improve the back-extraction efficiency. However, the concentration of fluoride ions in the back-extraction solution will decrease, and the energy consumption for subsequent evaporation and concentration will increase.

[0029] As a preferred embodiment, the back-extraction method employs at least one of single-stage back-extraction, multi-stage countercurrent back-extraction, multi-stage parallel-flow back-extraction, and multi-stage cross-flow back-extraction.

[0030] As a preferred embodiment, the back-extraction uses at least one of ammonia water, sodium hydroxide, and calcium hydroxide at a concentration of 1-3M as the back-extraction agent. When ammonia water is used as the back-extraction agent, solid ammonium fluoride can be obtained through an acid-base neutralization reaction. More preferably, the back-extraction agent is ammonia water at a concentration of 1-1.5M.

[0031] By optimizing the back-extraction conditions, the fluorine extracted from the negative fluorine organic phase can be desorbed, thereby regenerating the organic phase.

[0032] As a preferred embodiment, in step S2, the distillation recovery is carried out at a pressure of 10–200 mmHg, a temperature of 20–90°C, and a time of 20–200 min. Triethylamine azeotropically reacts with water at approximately 75°C under normal pressure. This invention uses a low-pressure distillation method to lower the boiling point of triethylamine to approximately 30–50°C, thereby achieving triethylamine recovery under relatively mild conditions. More preferably, the distillation recovery is carried out at a pressure of 22–40 mmHg and a temperature of 30–40°C.

[0033] As a preferred embodiment, the purity of the triethylamine recovered by distillation is further improved by adding calcium oxide to absorb excess water.

[0034] As a preferred embodiment, in S2, the purity of the fluoride is 95% or higher; in S2, the purity of the triethylamine is 98% or higher.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Through the synergistic effect of extractant A and extractant B, the present invention can selectively extract fluoride ions and inhibit the extraction of metal impurity cations without extracting water-soluble triethylamine through a one-step liquid-liquid extraction process, thereby achieving efficient and low-loss recovery of fluorine and triethylamine, and further preparing high-purity fluorides and triethylamine.

[0037] (2) The method of the present invention has the advantages of short process, no need for complicated impurity removal process, and low production cost. The method of the present invention can achieve a total fluorine recovery rate of more than 95% and a fluorine loss of less than 0.5%.

[0038] (3) When ammonia is used as the back-extraction agent, ammonium fluoride is generated by back-extraction and then evaporated and crystallized to directly obtain high-quality ammonium fluoride products, realizing the recovery of fluorine. The prepared products are crystalline, have smooth surfaces and good crystallinity, and can be directly used to prepare etchants, chemical polishing agents, fluxes, semiconductor materials, etc. Attached Figure Description

[0039] Figure 1 The image shows the XRD pattern of the ammonium chloride product prepared in Example 1 of this invention.

[0040] Figure 2 This is a SEM image of the ammonium chloride product prepared in Example 1 of the present invention. Detailed Implementation

[0041] The following specific embodiments are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the claims.

[0042] The chemical reagents used in the following specific examples are all conventional commercially available products.

[0043] This invention discloses a method for recovering fluoride and triethylamine from fluoride-containing organic wastewater, comprising the following steps:

[0044] S1 uses an organic phase containing extractant A and extractant B to extract fluoride-containing organic wastewater under an acidic environment, obtaining a raffinate containing water-soluble triethylamine and metal impurity ions and a fluoride-loaded organic phase; the fluoride-containing organic wastewater contains fluoride ions, metal impurity ions and water-soluble triethylamine.

[0045] S2 performs back-extraction and evaporation concentration on the fluorinated organic phase under alkaline conditions to obtain fluoride; the raffinate containing water-soluble triethylamine and metal impurity ions is then distilled to recover triethylamine.

[0046] Example 1

[0047] This embodiment provides a method for recovering fluorine and triethylamine from fluoride-containing organic wastewater. The fluoride-containing organic wastewater used in this embodiment has the main components listed in Table 1.

[0048]

[0049] The specific process of this embodiment is as follows:

[0050] S1 uses an organic phase containing extractant A and extractant B to extract fluoride-containing organic wastewater (raw material liquid), extracting all fluoride ions. The organic phase consists of 30 vol% extractant A + 30 vol% extractant B + 40 vol% sulfonated kerosene. Under the conditions of phase O / A = 4, pH = 2.5, extraction temperature = 25℃, and extraction time = 5 min, a four-stage countercurrent extraction is performed to obtain a raffinate containing metal impurity cations, water-soluble triethylamine, and a fluoride-loaded organic phase.

[0051] The structural formula of extractant A is:

[0052] ;

[0053] Formula 1;

[0054] The structural formula of extractant B is:

[0055] ;

[0056] Formula 2;

[0057] Wherein, R1 is a C3 alkyl group, R2 is a C6 alkyl group, and R3 is a C7 alkyl group.

[0058] The extraction rates of metal cations and triethylamine were both less than 0.5%. The residual concentrations of high-valence metal cations such as calcium, magnesium, iron, potassium, and sodium in the raffinate were 0.825 g / L, 1.20 g / L, 3.12 g / L, 0.889 g / L, and 1.414 g / L, respectively, and a fluorine-loaded organic phase with a fluorine content of 10.90 g / L was obtained.

[0059] S2 uses 1M ammonia water as the stripping agent to strip the fluorinated organic phase. The stripping method is single-stage stripping, with a stripping ratio of O / A of 8:1, a stripping temperature of 25℃, a stripping time of 5 min, and an equilibrium pH of 8. Subsequently, the water in the ammonium fluoride solution is evaporated and concentrated at 90℃ for 60 min, precipitating solid ammonium fluoride. After rinsing with anhydrous ethanol and drying in an oven at 90℃ for 6 h, solid ammonium fluoride product is obtained with a purity of 99.93% and a yield of 75.93%.

[0060] S3 involves low-temperature, low-pressure distillation of the raffinate containing water-soluble triethylamine and metal impurity ions. Triethylamine is distilled off under reduced pressure at 22 mmHg and 40°C, yielding a product with a purity of 95.1%, containing a small amount of water. Solid calcium oxide is added to absorb the excess water. After drying with calcium oxide, the purity of the triethylamine is increased to 99.5%.

[0061] The results showed that the fluorine extraction rate was higher than 99.5%, the extraction rate of other metal cation impurities was lower than 0.5%, the back-extraction of fluorine in the fluorine-loaded organic phase was almost complete, higher than 99%, the triethylamine purity reached 99.5%, and the recovery rate reached 98.7%.

[0062] Example 2

[0063] Compared with Example 1, the only difference is that the pH in the extraction in S1 is changed to 3, while other operations and parameters are the same as in Example 1.

[0064] The results showed that the extraction rate of fluorine was 89.72%, the extraction rates of other metal cation impurities were all less than 0.3%, the fluorine back-extraction rate was 99.1%, the purity of triethylamine was 98.8%, the recovery rate was 97.6%, and the purity of ammonium fluoride solid product in S2 was 99.1%.

[0065] Example 3

[0066] Compared with Example 1, the only difference is that the ratio in the extraction of S1 is changed to 3, and the other operations and parameters are the same as in Example 1.

[0067] The results showed that the fluorine extraction rate reached 91.85%, the extraction rates of other metal cations were still below 0.4%, the fluorine back-extraction rate was close to 100%, the triethylamine purity was 99.2%, and the recovery rate reached 97.8%. The purity of the ammonium fluoride solid product in S2 was 94.63%.

[0068] Example 4

[0069] Compared with Example 1, the only difference is that the concentration of ammonia as the back-extraction agent is 1.5M, and the other operations and parameters are the same as in Example 1.

[0070] The results showed that the fluorine extraction rate reached 99.50%, while the extraction rates of other metal cations were still below 0.5%, the fluorine back-extraction rate was still close to 100%, the back-extraction solution was alkaline, and excess alkali was wasted. The triethylamine purity was 98.13%, and the recovery rate was 97.8%. The purity of the ammonium fluoride solid product in S2 was 95.60%.

[0071] Example 5

[0072] Compared with Example 1, the only difference is that R1 is changed to a C4 alkyl group, R2 is changed to a C5 alkyl group, and R3 is changed to a C8 alkyl group. All other operations and parameters are the same as in Example 1.

[0073] The results showed that the fluorine extraction rate was 92.36%, which was lower than that in Example 1. The extraction rates of other metal cation impurities were all below 0.6%. The fluorine back-extraction rate was 98.8%, the triethylamine purity was 98.5%, the recovery rate was 96.9%, and the purity of the ammonium fluoride solid product in S2 was 99.0%. This indicates that the change in the alkyl chain length in extractants A and B has a certain impact on the extraction ability of fluoride ions. When the carbon chain lengths of R1, R2, and R3 are within the range set in Example 1, it is more conducive to forming a stable synergistic extraction system with fluoride ions, thereby obtaining a higher fluorine extraction rate.

[0074] Example 6

[0075] Compared with Example 1, the only difference is that the organic phase in S1 is changed to consist of 20v% extractant A + 20v% extractant B + 60v% sulfonated kerosene, while the rest of the operation and parameters are the same as in Example 1.

[0076] The results showed that the extraction rate of fluorine was 82.45%, the extraction rates of other metal cation impurities were all below 0.4%, the fluorine back-extraction rate was 98.5%, the purity of triethylamine was 98.3%, the recovery rate reached 97.2%, and the purity of the ammonium fluoride solid product in S2 was 97.2%. This indicates that when the volume fractions of extractant A and extractant B in the organic phase decrease, the extraction capacity for fluoride ions decreases due to the reduced extractant concentration, resulting in a lower fluorine extraction rate.

[0077] Example 7

[0078] Compared with Example 1, the only difference is that during back-extraction, the temperature is raised to 50°C for back-extraction; the other operations and parameters are the same as in Example 1.

[0079] The result was that the fluorine stripping rate decreased to 87.6%.

[0080] Comparative Example 1

[0081] Compared with Example 1, the only difference is that a single extractant A is used as the organic phase, and its volume is the same as the total volume of the combined extractants. Other operations and parameters are the same as in Example 1.

[0082] The results showed that the fluorine extraction rate was only 72.3%, while the extraction rates of other metal cation impurities were higher than 5%, significantly reducing the fluorine selectivity; the back-extraction rate also dropped to 86.4%, and the triethylamine recovery purity was only 92.7%.

[0083] Comparative Example 2

[0084] Compared with Example 1, the only difference is that a single extractant B is used to prepare the organic phase, and its volume is the same as the total volume of the combined extractants. All other conditions and parameters are the same as in Example 1.

[0085] The results were as follows: the fluorine extraction rate was only 58.5%, the metal cation impurity extraction rate was less than 0.1%, the back-extraction rate was as low as 79.2%, and the triethylamine recovery purity was 91.4%.

[0086] As can be seen from Example 1 and Comparative Examples 1 and 2, the combined extractant system is significantly superior to the single extractant in terms of fluorine selectivity, back-extraction efficiency and triethylamine cycle stability, thus avoiding the subsequent complex impurity removal process.

[0087] Comparative Example 3

[0088] Compared with Example 1, the only difference is that the distillation step is at 90°C and ambient temperature and pressure, while the remaining operations and parameters are the same as in Example 1.

[0089] The results showed that the triethylamine recovery purity was 85.6%, and the water content increased significantly.

[0090] Comparative Example 4

[0091] The organic phase composition in S1 was changed to consist of 40v% extractant A + 40v% extractant B + 20v% sulfonated kerosene, with the remaining operations and parameters the same as in Example 1.

[0092] The results showed that the fluorine extraction rate reached 99.7%, but the organic phase was too viscous and difficult to separate.

[0093] Comparative Example 5

[0094] Compared with Example 1, the only difference is that the pH in the extraction process of S1 is 5, while the other operations and parameters are the same as in Example 1.

[0095] The result was that the fluorine extraction rate was only 19.13%.

[0096] Comparative Example 6

[0097] Compared with Example 1, the only difference is that R1 is changed to a C2 alkyl group, and the other operations and parameters are the same as in Example 1.

[0098] The results showed that the extraction rate of fluorine decreased significantly to 65.32%, the extraction rates of other metal cation impurities remained below 0.5%, the fluorine back-extraction rate was 98.8%, the triethylamine purity was 98.5%, the recovery rate reached 96.9%, and the purity of the ammonium fluoride solid product in S2 was 99.0%. This indicates that when the carbon chain length of R1 in extractant A is shortened to a C2 alkyl group, its extraction ability for fluoride ions is significantly weakened. This is because the shorter alkyl chain leads to a decrease in the solubility of the extractant in the organic phase and its binding ability with fluoride ions.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the various operating conditions of the present invention. Although the present invention has been described in detail with reference to the above embodiments and comparative examples, those skilled in the art should understand that modifications can still be made to the technical solutions and technical conditions described in the above embodiments, or equivalent substitutions can be made to some or all of the technical solutions and technical conditions. These modifications or substitutions do not cause the essence of the corresponding technical solutions and technical conditions to deviate from the scope of the technical solutions and technical conditions of the various embodiments of the present invention, and these should also be considered as the protection scope of the present invention.

Claims

1. A method for recovering fluorine and triethylamine from fluoride-containing organic wastewater, characterized in that: Includes the following steps: S1 uses an organic phase containing extractant A and extractant B to extract fluoride-containing organic wastewater under pH conditions of 0.5–4, to obtain a raffinate containing water-soluble triethylamine and metal impurity ions and a fluoride-loaded organic phase; the fluoride-containing organic wastewater contains fluoride ions, metal impurity ions and water-soluble triethylamine. The extractant A has the structure of Formula 1: ； Formula 1; The extractant B has the structure of Formula 2: ； Formula 2; Among them, R1, R2, and R3 are independently selected from C3 to C4. 12 Alkyl groups; S2 back-extracts and evaporates the fluorinated organic phase to obtain fluoride; the raffinate containing water-soluble triethylamine and metal impurity ions is then distilled to recover triethylamine.

2. The method for recovering fluoride and triethylamine from fluoride-containing organic wastewater according to claim 1, characterized in that: The fluoride-containing organic wastewater contains 40-60 g / L of fluoride ions, 60-85 g / L of water-soluble triethylamine, and 0.1-10 g / L of metal impurity ions; And / or, The metal impurity ions include at least one of iron ions, calcium ions, magnesium ions, sodium ions, cobalt ions, and potassium ions.

3. The method for recovering fluoride and triethylamine from fluoride-containing organic wastewater according to claim 1, characterized in that: The organic phase containing extractant A and extractant B has a total volume concentration of extractant A to 70%. And / or, The organic phase containing extractant A and extractant B also contains a hydrophobic solvent.

4. A method for recovering fluoride and triethylamine from fluoride-containing organic wastewater according to claim 1 or 3, characterized in that: The volume ratio of extractant A to extractant B is (5~35):(5~35).

5. The method for recovering fluoride and triethylamine from fluoride-containing organic wastewater according to claim 3, characterized in that: The hydrophobic solvent includes at least one of kerosene, sulfonated kerosene, D60 solvent oil, and 200# kerosene.

6. The method for recovering fluoride and triethylamine from fluoride-containing organic wastewater according to claim 1, characterized in that: In S1, The extraction conditions are: pH 0.5–4, O / A ratio (1–5):1, extraction temperature 15–60℃, and extraction time 1–10 min. And / or, The extraction method employs at least one of the following: single-stage extraction, multi-stage countercurrent extraction, multi-stage co-current extraction, multi-stage cross-current extraction, and fractionation extraction.

7. A method for recovering fluoride and triethylamine from fluoride-containing organic wastewater according to claim 1 or 5, characterized in that: In S2, The back-extraction conditions are: an O / A ratio of (1~8):(2~1), a temperature of 20~40℃, and an equilibrium pH of 6~8; and / or, The back-extraction method employs at least one of the following: single-stage back-extraction, multi-stage countercurrent back-extraction, multi-stage parallel-flow back-extraction, and multi-stage cross-flow back-extraction.

8. The method for recovering fluoride and triethylamine from fluoride-containing organic wastewater according to claim 7, characterized in that: The back-extraction process uses at least one of ammonia, sodium hydroxide, and calcium hydroxide with a concentration of 1-3M as the back-extraction agent.

9. The method for recovering fluoride and triethylamine from fluoride-containing organic wastewater according to claim 1, characterized in that: In S2, The distillation recovery is carried out at a pressure of 10–200 mmHg, a temperature of 20–90 °C, and a time of 20–200 min.

10. A method for recovering fluorine and triethylamine from fluoride-containing organic wastewater according to claim 1 or 9, characterized in that: In S2, the purity of the fluoride is 95% or higher; in S2, the purity of the triethylamine is 98% or higher.

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