Extraction system of boric acid and method for extracting boric acid

Abstract

The invention discloses a boric acid extraction system and a boric acid extraction method, and belongs to the technical field of salt lake chemical industry. The extraction system is composed of isooctyl alcohol, a non-polar organic solvent and 1-decyl-3-methylimidazolium trifluoromethanesulfonate. The method for extracting boric acid comprises the following steps: adjusting the pH value of brine, adding an extraction system for three-stage extraction, and then adding a hydrochloric acid aqueous solution for reverse extraction. According to the extraction system provided by the invention, the selected low-temperature molten salt can promote the boric acid to be transferred into an organic phase by forming hydrogen bonds, so that the extraction efficiency and effect of the boric acid are greatly improved. The method is suitable for extracting boric acid from salt lake brine.

Description

Technical Field

[0001] The invention belongs to the technical field of salt lake chemical industry, and relates to a method for extracting boric acid from salt lake brine, in particular to a boric acid extraction system and a method for extracting boric acid. Background Art

[0002] Boric acid plays an important role in medicine, industry, agriculture and other fields. It is a chemical substance with great value. With the rapid development of global industry, the demand for boric acid is increasing day by day, and efficient acquisition of boric acid has become the focus of attention of related industries. The raw materials for industrial production of boric acid are mainly borate ore and salt lake brine. After years of mining, the ore is facing depletion, so the green and efficient extraction of boric acid from salt lake brine is becoming more and more important. The extraction of boric acid from salt lake brine mainly includes chemical precipitation, ion exchange, membrane separation, adsorption and solvent extraction. Among them, the solvent extraction method is an ideal method for extracting boric acid with broad application prospects due to its advantages such as fewer restrictions on the boric acid content in the solution (boric acid can be effectively extracted at a concentration level above 2g / L), short process flow and simple production equipment.

[0003] Solvent extraction usually uses monohydric alcohol as an extractant. Since monohydric alcohol has a small molecular weight and is usually water-soluble, it needs to be dissolved in an organic solvent. However, organic solvents are usually highly volatile and can pollute the environment. At the same time, monohydric alcohol has the problem of low extraction rate. During extraction, the alcohol hydroxyl group reacts with boric acid to form a complex soluble in alcohol. However, this reaction is reversible and the degree of reaction is limited. The single-stage extraction rate is low. Although multi-stage extraction can further improve the extraction rate, according to the distribution law, even after multi-stage extraction, it is difficult for the target substance to be completely separated in the two phases. When a certain number of stages is reached, the improvement in separation effect may not be obvious after increasing the number of stages. Continuing to increase the number of stages may lead to increased costs with little benefit.

[0004] The Chinese invention patent with application number "202211581040.0" and titled "An extractant for extracting boric acid from salt lake brine and a method for extracting boric acid" discloses the use of ionic liquid extractants to enhance the extraction effect of the process of extracting boric acid from salt lake brine and improve the single-stage extraction efficiency. However, the extraction rate of this method can only reach 90% to 95%. Summary of the invention

[0005] The purpose of the present invention is to provide a boric acid extraction system and a method for extracting boric acid, so as to solve the problem of low extraction rate of boric acid by monohydric alcohol extraction in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A boric acid extraction system, wherein the raw materials constituting the effective components thereof are isooctyl alcohol, a non-polar organic solvent and a low-temperature molten salt;

[0008] The low temperature molten salt includes 1-decyl-3-methylimidazolium trifluoromethanesulfonate.

[0009] As a limitation, the non-polar organic solvent includes ethyl propionate.

[0010] As another limitation, the volume fraction of the isooctyl alcohol in the extraction system is 50%, the volume fraction of the low-temperature molten salt in the extraction system is 10% to 40%, and the remainder is a non-polar organic solvent.

[0011] The present invention also provides a method for extracting boric acid, comprising the following steps performed in sequence:

[0012] S1. adjusting the pH value of the boron-containing brine to 1 to 3, adding the above-mentioned extraction system for extraction, standing and stratifying to obtain a first organic phase and a first aqueous phase;

[0013] S2. Take the first aqueous phase, add the extraction system for extraction, stand and separate, and obtain a second organic phase and a second aqueous phase;

[0014] S3. Take the second aqueous phase, add the extraction system for extraction, stand and separate to obtain a third organic phase and a third aqueous phase;

[0015] S4. Take the first organic phase, the second organic phase and the third organic phase respectively, add aqueous hydrochloric acid solution for back extraction, mix the obtained aqueous phases, and the extraction of boric acid can be completed.

[0016] As a limitation, the volume ratio of the extraction system to the boron-containing brine, the first aqueous phase or the second aqueous phase is (0.5-3):1, and the volume ratio of the hydrochloric acid aqueous solution to the first organic phase, the second organic phase or the third organic phase is (0.5-5):1.

[0017] As a further limitation, the extraction is carried out at a temperature of 15 to 25° C. and for a time of 10 to 30 minutes.

[0018] As another limitation, the pH value of the aqueous hydrochloric acid solution is ≤1.

[0019] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0020] ① The present invention provides a boric acid extraction system, wherein anions in 1-decyl-3-methylimidazolium trifluoromethanesulfonate can form stable hydrogen bonds with hydroxyl groups in boric acid molecules, making it easier for boric acid molecules to blend into an organic phase, thereby increasing the solubility of boric acid in the organic phase; at the same time, the presence of hydrogen bonds changes the solvation environment of boric acid molecules, and the hydrogen bonds with trifluoromethanesulfonate ions replace the binding of water molecules with boric acid, thereby causing boric acid molecules to be more inclined to transfer to the organic phase; in addition, hydrogen bonds can also affect the aggregation state of boric acid molecules, breaking their original aggregation structure in an aqueous solution, allowing boric acid molecules to interact with trifluoromethanesulfonate ions in a more dispersed state, and smoothly enter the organic phase in the form of single molecules or smaller aggregates, thereby improving the efficiency and effect of extraction;

[0021] ② The present invention provides a boric acid extraction system, wherein the hydroxyl group of isooctyl alcohol reacts with boric acid to form a complex soluble in isooctyl alcohol, and extraction is performed. When the extraction equilibrium is reached, the ratio of the concentration of boric acid in the isooctyl alcohol phase to the concentration in the aqueous phase meets the distribution coefficient, so multiple extractions can realize the transfer of boric acid from the aqueous phase to the isooctyl alcohol phase, thereby achieving the purpose of separating and enriching boric acid; ethyl propionate has good solubility and can effectively dissolve various organic substances. Its chemical stability ensures that its own properties are stable during the extraction process and can be reused after regeneration;

[0022] ③ The present invention provides a boric acid extraction system, the structure of the low-temperature molten salt makes it have almost no measurable vapor pressure at room temperature, and has extremely low volatility compared to traditional organic solvents. The addition of low-temperature molten salt will dilute other components with higher volatility in the extraction system, thereby reducing the volatility of the extraction system as a whole and reducing losses;

[0023] ④ The method for extracting boric acid provided by the present invention only needs to adjust the pH value of the brine to acidic and directly add it into the extraction system for extraction. The process is simple and easy to operate, does not require high temperature and high pressure conditions, is more energy-efficient, and improves the product yield through three-stage extraction. The extraction rate can reach 99.9%, which is suitable for industrial production and can generate huge economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a graph showing the effect of different low-temperature molten salt contents on the extraction rate in Example 1;

[0025] Figure 2 This is a result diagram showing the effect of the number of extraction stages on the extraction rate in Example 1; DETAILED DESCRIPTION

[0026] The present invention is further described in detail below by specific examples. It should be understood that the described examples are only used to explain the present invention, and are not intended to limit the present invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art.

[0028] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0029] The boron-containing brines used in the following examples and comparative examples were all prepared in the laboratory, and the specific component contents are shown in Table 1:

[0030] Table 1 List of components of boron-containing brine

[0031] Element Boric acid Magnesium chloride Content (g / L) 5.1 380

[0032] Example 1

[0033] This embodiment discloses a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0034] S1. Take 500mL of boron-containing brine, adjust the pH value to 3 with hydrochloric acid, add 500mL of extraction system A (mixed by 50% isooctyl alcohol, 40% 1-decyl-3-methylimidazolium trifluoromethanesulfonate and 10% ethyl propionate by volume), extract at 25°C for 20min, stand in a separatory funnel for 20min to separate layers, obtain a first organic phase and a first aqueous phase, take 0.05mL of the first aqueous phase, dilute it 200 times, determine the boric acid content in the aqueous phase by azomethine-H spectrophotometry, and calculate the extraction rate. The formula for calculating the extraction rate E is as follows:

[0035]

[0036] When other conditions remain unchanged, the extraction system A is composed of 50% by volume of isooctyl alcohol, 0-50% by volume of 1-decyl-3-methylimidazolium trifluoromethanesulfonate, and the balance of ethyl propionate, the first aqueous phase is tested, and the results are as follows: Figure 1 As shown;

[0037] Depend on Figure 1 It can be seen that with the increase of low-temperature molten salt, the extraction rate shows a significant upward trend, indicating that the number of active sites in the extraction system that can interact with the target substance increases, thereby more effectively extracting the target substance from the raw material phase. When the volume fraction of low-temperature molten salt is 40%, the extraction rate reaches the highest, and the extraction rate no longer increases when the low-temperature molten salt is further increased.

[0038] S2. Take the first aqueous phase and add extraction system A (the volume ratio of the two is 1:1), extract at 25°C for 20 minutes, let it stand in a separatory funnel for 20 minutes to separate the layers, and obtain the second organic phase and the second aqueous phase. Take the second aqueous phase for detection.

[0039] S3. Take the second aqueous phase and add the extraction system A (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0040] The third aqueous phase was added to the extraction system A (the volume ratio of the two was 1:1), extracted at 25°C for 20 minutes, and allowed to stand in a separatory funnel for 20 minutes to separate the layers to obtain a fourth organic phase and a fourth aqueous phase. The fourth aqueous phase was tested, and the extraction rate results were as follows: Figure 2 As shown;

[0041] Depend on Figure 2 It can be seen that with the increase of the number of extraction stages, the extraction rate of boric acid continues to increase. The extraction rate has reached 99.9% in the third-stage extraction. In the fourth-stage extraction, the extraction rate no longer increases. The fourth organic phase basically does not contain boric acid. Therefore, in order to simplify the operation process, this extraction method only needs to perform three-stage extraction to achieve the best effect.

[0042] S4. Take the first organic phase, the second organic phase and the third organic phase respectively, add an aqueous hydrochloric acid solution (pH 1) of the same volume as the organic phase, stir for 20 minutes at 25°C for back extraction, mix the obtained aqueous phases, and the extraction of boric acid can be completed. The remaining organic phase can be reused.

[0043] Example 2

[0044] This embodiment discloses a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0045] S1. Take 500mL of boron-containing brine, adjust the pH value to 2 with hydrochloric acid, add 250mL of extraction system A (mixed by 50% isooctyl alcohol, 40% 1-decyl-3-methylimidazolium trifluoromethanesulfonate and 10% ethyl propionate by volume), extract at 20°C for 30min, let stand in a separatory funnel for 20min to separate the layers, and obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0046] S2. Take the first aqueous phase and add the extraction system A (the volume ratio of the two is 1:0.5), extract at 20 ° C for 30 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a second organic phase and a second aqueous phase, and take the second aqueous phase for detection;

[0047] S3. Take the second aqueous phase and add the extraction system A (the volume ratio of the two is 1:0.5), extract at 20 ° C for 30 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0048] S4. Take the first organic phase, the second organic phase and the third organic phase respectively, add a hydrochloric acid aqueous solution with a pH value of 1 (the volume ratio of the organic phase to the hydrochloric acid aqueous solution is 1:0.5), stir for 20 minutes at 25°C for back extraction, mix the obtained aqueous phases, and the extraction of boric acid can be completed. The remaining organic phase can be reused.

[0049] Example 3

[0050] This embodiment discloses a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0051] S1. Take 1000mL of boron-containing brine, adjust the pH value to 1 with hydrochloric acid, add 3000mL of extraction system B (mixed by 50% isooctyl alcohol, 30% 1-decyl-3-methylimidazolium trifluoromethanesulfonate and 20% ethyl propionate by volume), extract at 15°C for 10min, let stand in a separatory funnel for 20min to separate the layers, and obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0052] S2. Take the first aqueous phase and add the extraction system B (the volume ratio of the two is 1:3), extract at 15 ° C for 10 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain the second organic phase and the second aqueous phase, and take the second aqueous phase for detection;

[0053] S3. Take the second aqueous phase and add the extraction system B (the volume ratio of the two is 1:3), extract at 15 ° C for 10 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0054] S4. Take the first organic phase, the second organic phase and the third organic phase respectively, add a hydrochloric acid aqueous solution with a pH value of 1 (the volume ratio of the organic phase to the hydrochloric acid aqueous solution is 1:5), stir for 20 minutes at 25°C for back extraction, mix the obtained aqueous phases, and the extraction of boric acid can be completed. The remaining organic phase can be reused.

[0055] Comparative Example 1

[0056] This comparative example provides a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0057] S1. Take 500 mL of boron-containing brine, adjust the pH value to 3 with hydrochloric acid, add 500 mL of extraction system C (mixed by 50% by volume of isooctyl alcohol, 40% of 1-octyl-3-methylimidazolium hexafluorophosphate and 10% of ethyl propionate), extract at 25 ° C for 20 min, stand in a separatory funnel for 20 min to separate the layers, and obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0058] S2. Take the first aqueous phase and add the extraction system C (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain the second organic phase and the second aqueous phase, and take the second aqueous phase for detection;

[0059] S3. Take the second aqueous phase and add the extraction system C (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0060] S4. Take the first organic phase and add an equal volume of aqueous hydrochloric acid solution (pH 1), stir at 25°C for 20 minutes for back extraction, and detect the obtained aqueous phase.

[0061] Comparative Example 2

[0062] This comparative example provides a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0063] S1. Take 500 mL of boron-containing brine, adjust the pH value to 3 with hydrochloric acid, add 500 mL of extraction system D (mixed by 50% by volume of isooctyl alcohol, 40% of 1-hydroxyethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt and 10% of ethyl propionate), extract at 25°C for 20 min, stand in a separatory funnel for 20 min to separate the layers, and obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0064] S2. Take the first aqueous phase and add the extraction system D (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain the second organic phase and the second aqueous phase, and take the second aqueous phase for detection;

[0065] S3. Take the second aqueous phase and add the extraction system D (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0066] S4. Take the first organic phase and add an equal volume of aqueous hydrochloric acid solution (pH 1), stir at 25°C for 20 minutes for back extraction, and detect the obtained aqueous phase.

[0067] Comparative Example 3

[0068] This comparative example provides a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0069] S1. Take 500 mL of boron-containing brine, adjust the pH value to 3 with hydrochloric acid, add 500 mL of extraction system E (mixed by 50% by volume of isooctyl alcohol, 40% of 1-methyl-1-propylpyrrolidine bistrifluoromethanesulfonyl imide salt and 10% of ethyl propionate), extract at 25 ° C for 20 min, stand in a separatory funnel for 20 min to separate the layers, and obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0070] S2. Take the first aqueous phase and add the extraction system E (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain the second organic phase and the second aqueous phase, and take the second aqueous phase for detection;

[0071] S3. Take the second aqueous phase and add the extraction system E (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0072] S4. Take the first organic phase and add an equal volume of aqueous hydrochloric acid solution (pH 1), stir at 25°C for 20 minutes for back extraction, and detect the obtained aqueous phase.

[0073] Comparative Example 4

[0074] This comparative example provides a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0075] S1. Take 500 mL of boron-containing brine, adjust the pH value to 3 with hydrochloric acid, add 500 mL of extraction system F (mixed by 50% by volume of isooctyl alcohol, 40% of 1-hexyl-3-methylimidazolium tetrafluoroborate and 10% of ethyl propionate), extract at 25 ° C for 20 min, stand in a separatory funnel for 20 min to separate the layers, and obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0076] S2. Take the first aqueous phase and add the extraction system F (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a second organic phase and a second aqueous phase, and take the second aqueous phase for detection;

[0077] S3. Take the second aqueous phase and add the extraction system F (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0078] S4. Take the first organic phase and add an equal volume of aqueous hydrochloric acid solution (pH 1), stir at 25°C for 20 minutes for back extraction, and detect the obtained aqueous phase.

[0079] Comparative Example 5

[0080] This comparative example provides a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0081] S1. Take 500mL of boron-containing brine, adjust the pH value to 3 with hydrochloric acid, add 500mL of extraction system A (mixed by 50% by volume of isooctyl alcohol, 40% of 1-decyl-3-methylimidazolium trifluoromethanesulfonate and 10% of ethyl propionate), extract at 25°C for 20min, stand in a separatory funnel for 20min to separate the layers, obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0082] S2. Take the first aqueous phase and add the extraction system A (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain the second organic phase and the second aqueous phase, and take the second aqueous phase for detection;

[0083] S3. Take the second aqueous phase and add the extraction system A (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0084] S4. Take the first organic phase and add an equal volume of aqueous hydrochloric acid solution (pH 2), stir at 25°C for 20 minutes for back extraction, and detect the obtained aqueous phase.

[0085] Comparative Example 6

[0086] This comparative example provides a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0087] S1. Take 500mL of boron-containing brine, adjust the pH value to 5 with hydrochloric acid, add 500mL of extraction system A (mixed by 50% isooctyl alcohol, 40% 1-decyl-3-methylimidazolium trifluoromethanesulfonate and 10% ethyl propionate by volume), extract at 25°C for 20min, let stand in a separatory funnel for 20min to separate the layers, obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0088] S2. Take the first aqueous phase and add the extraction system A (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain the second organic phase and the second aqueous phase, and take the second aqueous phase for detection;

[0089] S3. Take the second aqueous phase and add the extraction system A (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0090] S4. Take the first organic phase and add an equal volume of aqueous hydrochloric acid solution (pH 1), stir at 25°C for 20 minutes for back extraction, and detect the obtained aqueous phase.

[0091] Comparative Example 7

[0092] This comparative example provides a method for extracting boric acid, which specifically comprises the following steps performed in sequence:

[0093] S1. Take 500mL of boron-containing brine, adjust the pH value to 3 with hydrochloric acid, add 500mL of extraction system A (mixed by 50% by volume of isooctyl alcohol, 40% of 1-decyl-3-methylimidazolium trifluoromethanesulfonate and 10% of ethyl propionate), extract at 25°C for 20min, stand in a separatory funnel for 20min to separate the layers, obtain a first organic phase and a first aqueous phase, and take the first aqueous phase for detection;

[0094] S2. Take the first aqueous phase and add the extraction system A (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain the second organic phase and the second aqueous phase, and take the second aqueous phase for detection;

[0095] S3. Take the second aqueous phase and add the extraction system A (the volume ratio of the two is 1:1), extract at 25 ° C for 20 minutes, stand in a separatory funnel for 20 minutes to separate the layers, and obtain a third organic phase and a third aqueous phase, and take the third aqueous phase for detection;

[0096] S4. Take the first organic phase and add a hydrochloric acid aqueous solution with a pH value of 1 (the volume ratio of the first organic phase to the hydrochloric acid aqueous solution is 1:0.3), stir at 25°C for 20 minutes for back extraction, and detect the obtained aqueous phase.

[0097] Test results

[0098] Since the first organic phase contains the most boric acid, in order to accurately determine the stripping rate of each embodiment and comparative example, the stripping rate is calculated based on the first organic phase and the aqueous phase after the hydrochloric acid stripping. The extraction rate and stripping rate results of each embodiment and comparative example are shown in Table 2:

[0099] Table 2 Extraction rate and stripping rate list

[0100] serial number Primary extraction rate (%) Secondary extraction rate (%) Tertiary extraction rate (%) Stripping rate (%) Example 1 69.5 95.3 99.9 99.9 Example 2 81.4 99.9 99.9 99.9 Example 3 76.4 99.8 99.9 99.9 Comparative Example 1 60.3 80.6 88.6 90.6 Comparative Example 2 50.8 60.4 70.8 96.6 Comparative Example 3 65.5 80.2 90.4 93.7 Comparative Example 4 65.2 66.4 67.2 99.9 Comparative Example 5 68.4 94.8 99.9 87.6 Comparative Example 6 30.9 52.7 70.3 99.9 Comparative Example 7 69.9 95.1 99.9 83.6

[0101] As can be seen from Table 2, the extraction system and extraction method of boric acid provided by the present invention have a three-stage extraction rate of 99.9% after three extractions, and the interaction between the extraction system provided by the present invention and the extracted material is unique. After the extraction is completed, the organic phase and the extracted material can be efficiently separated by simple stripping, so that the extracted material is precipitated from the organic phase, and the properties of the organic phase are not affected. It has high chemical stability and will not deteriorate after extraction-stripping. After multiple extractions-stripping, it can still maintain its original chemical properties and extraction capacity, so that it can be reused;

[0102] By comparing Example 1 with Comparative Examples 1 to 4, it can be seen that when all other parameters remain unchanged, only the components of the low-temperature molten salt in the extraction system are changed, resulting in a decrease in the extraction rate or stripping rate of boric acid to varying degrees, indicating that the extraction system composed of 1-decyl-3-methylimidazolium trifluoromethanesulfonate provided by the present invention is significantly better than other similar molten salts;

[0103] By comparing Example 1 and Comparative Example 5, it can be seen that the pH value of hydrochloric acid has a significant effect on the stripping rate. When the pH value is ≤1, it is conducive to the forward stripping and the extraction recovery rate reaches a peak value. When the pH value is >1, the stripping rate decreases. This is because the H + As the concentration of boric acid increases, it tends to exist in the aqueous phase as B(OH)3 molecules rather than as B(OH)4 - Exist in ionic form (the solubility of the molecular form in the aqueous phase is relatively large, so it is easier to transfer from the organic phase to the aqueous phase, thereby increasing the stripping rate);

[0104] By comparing Example 1 and Comparative Example 6, it can be seen that when the pH value of the boron-containing brine is ≤3, the extraction rate of boric acid is high and stable, and when the pH value increases from 3 to gradually tend to neutral, the extraction rate of boric acid decreases significantly. This is because at a lower pH, boric acid mainly exists in molecular form. As the pH increases, boric acid will gradually combine with hydroxide ions to form borate ions. When the pH is between 1 and 3, it is beneficial for boric acid to form a complex with the extractant, thereby improving the extraction efficiency.

[0105] By comparing Example 1 and Comparative Example 7, it can be seen that as the volume of the hydrochloric acid aqueous solution increases, the concentration of the extracted substance in the hydrochloric acid aqueous solution is relatively reduced, the stripping driving force provided by the hydrochloric acid aqueous solution is relatively enhanced, more extracted substances have the opportunity to transfer from the organic phase to the aqueous phase, and the stripping rate is usually increased.

[0106] In summary, the boric acid extraction system and extraction method provided by the present invention are the optimal results obtained after a large number of experiments. When extracting boric acid from brine, the tertiary extraction rate can reach 99.9%. Changing the composition of the extraction system, the pH value of the boron-containing brine and the pH value of the hydrochloric acid aqueous solution will affect the extraction and stripping of boric acid.

Claims

1. A boric acid extraction system, characterized in that: The raw materials constituting its effective ingredients are isooctyl alcohol, non-polar organic solvent and low-temperature molten salt; The low temperature molten salt includes 1-decyl-3-methylimidazolium trifluoromethanesulfonate.

2. The boric acid extraction system according to claim 1, characterized in that: The non-polar organic solvent includes ethyl propionate.

3. A boric acid extraction system according to claim 1 or 2, characterized in that: The isooctyl alcohol accounts for 50% by volume of the extraction system, the low-temperature molten salt accounts for 10% to 40% by volume of the extraction system, and the remainder is a non-polar organic solvent.

4. A method for extracting boric acid, characterized in that: The process includes the following steps: S1. Adjust the pH value of the boron-containing brine to 1-3, add the extraction system according to any one of claims 1-3 for extraction, and allow to stand for stratification to obtain a first organic phase and a first aqueous phase; S2. Take the first aqueous phase, add the extraction system according to any one of claims 1 to 3 for extraction, and stand for stratification to obtain a second organic phase and a second aqueous phase; S3. Take the second aqueous phase, add the extraction system according to any one of claims 1 to 3 for extraction, and allow to stand for stratification to obtain a third organic phase and a third aqueous phase; S4. Take the first organic phase, the second organic phase and the third organic phase respectively, add aqueous hydrochloric acid solution for back extraction, mix the obtained aqueous phases, and the extraction of boric acid can be completed.

5. The method for extracting boric acid according to claim 4, characterized in that: The volume ratio of the extraction system to the boron-containing brine, the first aqueous phase or the second aqueous phase is 0.5-3:1, and the volume ratio of the hydrochloric acid aqueous solution to the first organic phase, the second organic phase or the third organic phase is 0.5-5:

1.

6. The method for extracting boric acid according to claim 5, characterized in that: The extraction temperature is 15-25° C. and the extraction time is 10-30 min.

7. The method for extracting boric acid according to any one of claims 4 to 6, characterized in that: The pH value of the hydrochloric acid aqueous solution is ≤1.

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