Hydrophobic deep eutectic solvent and method for extracting boric acid from salt lake brine

Abstract

The invention discloses a hydrophobic deep eutectic solvent and a method for extracting boric acid from salt lake brine. The hydrophobic deep eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor, the hydrogen bond donor comprises a dihydroxy-containing dihydric alcohol compound, and the hydrogen bond acceptor comprises a phosphorus-oxygen double bond-containing compound. The hydrophobic deep eutectic solvent has the advantages of being good in extraction effect, low in organic solution loss, small in acid and alkali consumption, free of diluents and the like when being used for extracting boron from salt lake brine, the extraction effect of the process of extracting boric acid from the salt lake brine can be enhanced by applying the hydrophobic deep eutectic solvent, the single-stage extraction efficiency is improved, and the hydrophobic deep eutectic solvent has the advantages of being high in saturation capacity and low in cost. The application prospect is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of salt lake chemical industry, and particularly relates to a hydrophobic deep eutectic solvent and a method for extracting boric acid from salt lake brine. Background Art

[0002] Boric acid is an important basic chemical raw material, known as "industrial MSG". Boric acid is an important component of many chemical products such as glass fiber, permanent magnetic materials, ceramics, detergents, pesticides, flame retardants, etc. It plays an important role in the development of many industries such as metallurgy, building materials, machinery, electronics, chemicals, national defense, agriculture, and medicine. With the rapid development of my country's economy, the demand for boric acid is increasing. After decades of mining, solid boron ore resources have been increasingly exhausted, while my country's salt lake brine contains rich potassium, magnesium, lithium, and boron resources. Therefore, strengthening the effective development and utilization of boron resources in salt lake brine can not only meet the market demand for boric acid, but also be conducive to the comprehensive utilization of important resources such as potassium, magnesium, and lithium in salt lake brine.

[0003] At present, the main boron extraction technologies for salt lake brine at home and abroad include acidification, precipitation, fractional crystallization, adsorption and solvent extraction. Among them, the acidification method is mainly suitable for systems with high boron content (>18g / L), and is generally used in combination with other methods in actual production to obtain a higher extraction rate. The precipitation method has a complex process flow, large acid consumption in the later stage, poor economy, and is difficult to apply on a large scale. The adsorption method is generally used to remove boron from low-boron wastewater, and the adsorption capacity of the materials used in the adsorption method is small, making it difficult to treat boron-rich brine. Since the solvent extraction method has the advantages of good selectivity, thorough impurity separation, and high boron recovery rate, it has broad application prospects in the extraction of boric acid from salt lake brine.

[0004] Solvent extraction has different limitations due to the different extractants used. For example, the monohydric alcohol extractant used has low single-stage extraction rate, many extraction stages required, is greatly affected by the properties of salt lake brine, and has low saturation capacity. The solubility of the dihydric alcohol extractant in low-polarity solvents is very low, and a high-polarity solvent is required, and high-polarity solvents are often highly toxic. Even if dissolved in benzene, toluene, ethyl acetate, amyl acetate, and chloroform, its volatility is too high, resulting in excessive loss of the extractant, and there is also the problem of low saturation capacity, which limits industrial application to a certain extent. At present, the research on dihydric alcohol extractants is mainly concentrated on 1,3-dihydric alcohols, such as 2-butyl-2-ethyl-1,3-propylene glycol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,2,5-trimethyl-1,3-hexanediol, etc.

[0005] Hydrophobic deep eutectic solvent is a new type of green mixed solvent formed by hydrogen bonding between hydrogen bond donors and hydrogen bond acceptors. It has good thermal stability, non-volatility and structural adjustability. It has been widely used in the field of chemical separation as a substitute for traditional organic extractants. Summary of the invention

[0006] The object of the present invention is to provide a hydrophobic deep eutectic solvent and method for extracting boric acid from salt lake brine, so as to overcome the shortcomings of existing diols as boric acid extractants.

[0007] To achieve this object of the invention, the present invention is achieved through the following technical solutions:

[0008] The present invention provides a hydrophobic deep eutectic solvent for extracting boric acid from salt lake brine, which comprises: a hydrogen bond donor and a hydrogen bond acceptor, wherein the hydrogen bond donor comprises a diol compound containing a dihydroxyl group, and the hydrogen bond acceptor comprises a compound containing a phosphorus oxygen double bond.

[0009] The hydrogen bond donor includes any one of 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diaryl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-3-benzyl-1,3-butanediol, 2-benzyl-2,4-pentanediol, and 2,2-dimethyl-1-benzyl-1,3-propanediol, or a combination of two or more alcohol compounds.

[0010] The hydrogen bond acceptor has the structures shown in formula (I), formula (II) and formula (III): Among them, R1 is any one of C3~C8 straight chain or branched alkyl, C3~C8 straight chain or branched substituted alkyl, phenyl, carboxyl, and amino; R2 is any one of C3~C8 straight chain or branched alkyl, C3~C8 straight chain or branched substituted alkyl, phenyl, carboxyl, and amino; R3 is any one of C3~C8 straight chain or branched alkyl, C3~C8 straight chain or branched substituted alkyl, phenyl, carboxyl, and amino.

[0011] The embodiment of the present invention also provides the use of the aforementioned hydrophobic deep eutectic solvent to extract boric acid in salt lake brine.

[0012] The invention provides a method for extracting boric acid from salt lake brine. The extraction system is mixed with the salt lake brine to perform extraction and stripping treatment, thereby achieving separation and enrichment of the boric acid.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] The hydrophobic deep eutectic solvent provided by the present invention has strong universality and does not require special pre-treatment of salt lake brine. The extraction system of the present invention does not require acidification and regulation of pH (1-6) of salt lake brine, thereby reducing acid consumption. The extraction system of the present invention does not require a diluent.

[0015] The present invention can appropriately increase the proportion of the hydrogen bond donor in the hydrophobic deep eutectic solvent by selecting and matching the hydrogen bond donor and the hydrogen bond acceptor, thereby improving the single-stage extraction efficiency, saturating the extraction capacity, and reducing the use of the hydrophobic deep eutectic solvent.

[0016] The hydrophobic deep eutectic solvent provided by the present invention has stable properties and low volatility, and the dissolution loss of the hydrophobic deep eutectic solvent can be further reduced by selecting and matching the hydrogen bond donor and the hydrogen bond acceptor.

[0017] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. The present invention proposes a new hydrophobic deep eutectic solvent extraction system based on dihydroxy diol compounds / compounds containing phosphorus and oxygen double bonds, which realizes the selective separation of boron and other metal ions in salt lake brine through the selective extraction of boron. The extraction system mentioned in the present invention uses diol as a hydrogen bond donor and a compound containing a phosphorus and oxygen double bond as a hydrogen bond acceptor to form a hydrophobic deep eutectic solvent to extract boric acid, wherein the phosphorus and oxygen double bonds in the compound containing a phosphorus and oxygen double bond have a physical interaction with boric acid, which promotes boric acid to enter the organic phase, thereby improving the extraction efficiency. At the same time, the phosphorus and oxygen double bonds and the hydroxyl groups of alcohols form a hydrophobic deep eutectic solvent through hydrogen bonding, which greatly increases the fluidity and extraction capacity of the entire system. In addition, the extraction system of the present invention is simple to prepare, has a good boron separation effect, and has a good application prospect.

[0018] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Specifically, as one aspect of the technical solution of the present invention, a hydrophobic deep eutectic solvent for extracting boric acid from salt lake brine comprises a hydrophobic deep eutectic solvent formed by a dihydroxy diol compound as a hydrogen bond donor and a phosphorus-oxygen double bond compound as a hydrogen bond acceptor.

[0020] In some embodiments, the phosphorus-oxygen double bond compound includes any one or a combination of two or more of tri-n-butylphosphine oxide, tri-n-octylphosphine oxide, Cyanex923, and trioctyl phosphate, but is not limited thereto.

[0021] In some embodiments, the dihydroxy diol compound includes 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol and is not limited thereto.

[0022] Furthermore, the alcohol compound is any one or a combination of two or more of the aforementioned diols, and is not limited thereto.

[0023] The present invention provides a method for extracting boric acid from salt lake brine, comprising:

[0024] (1) The hydrogen bond donor and the hydrogen bond acceptor are treated according to a certain method to obtain a hydrophobic deep eutectic solvent.

[0025] (2) The salt lake brine and the hydrophobic deep eutectic solvent are mixed and extracted in a certain volume ratio, and the mixed liquid is treated after a period of time to obtain a raffinate and a boron-containing organic solution.

[0026] (3) The boron-containing organic solution is stripped to obtain a boron-containing solution, and the organic solution can be reused.

[0027] The hydrophobic deep eutectic solvent in step (1) is prepared by mixing the hydrogen bond donor and the hydrogen bond acceptor in a certain molar ratio and heating them at 80° C. for 3 hours.

[0028] The molar ratio of the hydrogen bond donor and the hydrogen bond acceptor of the hydrophobic deep eutectic solvent in step (1) is 5:1 to 1:2, for example: 5:1, 4:1, 3:1, 2:1, 1:1, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] The pH value of the salt lake brine in step (2) is 1 to 6, such as 1, 2, 3, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0030] The volume ratio of the salt lake brine and the hydrophobic deep eutectic solvent in step (2) is (16-1):1, for example: 16:1, 8:1, 4:1, 2:1 or 1:1, etc., not limited to the listed values, other values ​​not listed in the numerical range are also applicable. The optimized technical solution is 2:1-1:1.

[0031] In the process of mixed extraction of the salt lake brine and the hydrophobic deep eutectic solvent, the extraction temperature is 5 to 40° C. and the extraction time is 5 to 15 minutes.

[0032] In step (3), the stripping agent is an alkaline aqueous solution, such as a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution, but is not limited to the alkaline aqueous solutions listed.

[0033] The volume ratio of the obtained boron-containing organic solution to the stripping agent is 1:20-20:1.

[0034] In the process of mixing the boron-containing organic solution with a stripping agent for stripping in step (3), the stripping temperature is 10 to 40° C. and the stripping time is 10 to 20 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0036] The technical scheme of the present invention is further described in detail below in conjunction with several embodiments. This embodiment is implemented on the premise of the technical scheme of the invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments. The experimental materials used in the embodiments used below, unless otherwise specified, can all be purchased from conventional biochemical reagent companies.

[0037] Example 1

[0038] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and tri-n-butylphosphine oxide was used as a hydrogen bond acceptor in a molar ratio of 2:1. The mixture was heated and stirred to form a hydrophobic deep eutectic solvent. A salt lake brine containing 4.29 g / L boric acid and pH = 2.4 was used as a raw material. A single-stage extraction was performed under the conditions of a volume ratio of brine to hydrophobic deep eutectic solvent of 1:1, 2:1, 4:1, 8:1, and 16:1. The extraction time was 10 minutes. After the extraction was balanced, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration in the solution was tested.

[0039] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, 8:1, and 16:1 were 99.68%, 98.21%, 94.51%, 87.84%, and 72.67%, respectively. A 0.5 mol / L sodium hydroxide aqueous solution or a 0.5 mol / L potassium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic solution to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0040] Example 2

[0041] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and tri-n-butylphosphine oxide was used as a hydrogen bond acceptor in a molar ratio of 2:1. The mixture was heated and stirred to form a hydrophobic deep eutectic solvent. A salt lake brine containing 30.37 g / L boric acid and pH = 1.4 was used as a raw material. A single-stage extraction was performed under the conditions of a volume ratio of brine to hydrophobic deep eutectic solvent of 1:1, 2:1, 4:1, and 8:1. The extraction time was 10 minutes. After the extraction was balanced, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration in the solution was tested.

[0042] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, and 8:1 were 98.53%, 96.41%, 85.29%, and 60.92%, respectively. A 0.5 mol / L sodium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic solution to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0043] Example 3

[0044] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and tri-n-butylphosphine oxide was used as a hydrogen bond acceptor in a molar ratio of 2:1. The mixture was heated and stirred to form a hydrophobic deep eutectic solvent. A salt lake brine containing 16.99 g / L boric acid and pH = 5.5 was used as a raw material. The volume ratio of brine to hydrophobic deep eutectic solvent was 1:1, 2:1, 4:1, 8:1, 16:1. Single-stage extraction was performed. The extraction time was 10 min. After the extraction was balanced, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration in the solution was tested.

[0045] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, 8:1, and 16:1 were 97.52%, 95.97%, 91.32%, 64.31%, and 40.09%, respectively. A 0.5 mol / L sodium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic solution to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0046] Example 4

[0047] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and tri-n-octylphosphine oxide was used as a hydrogen bond acceptor in a molar ratio of 2:1. The mixture was heated and stirred to form a hydrophobic deep eutectic solvent. A salt lake brine containing 4.29 g / L boric acid and pH = 2.4 was used as a raw material. A single-stage extraction was performed under the conditions of a volume ratio of brine to hydrophobic deep eutectic solvent of 1:1, 2:1, 4:1, 8:1, and 16:1. The extraction time was 10 minutes. After the extraction was balanced, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration in the solution was tested.

[0048] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, 8:1, and 16:1 were 97.84%, 96.36%, 92.66%, 82.66%, and 62.68%, respectively. A 0.5 mol / L sodium hydroxide aqueous solution or a 0.5 mol / L potassium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic solution to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0049] Example 5

[0050] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and tri-n-octylphosphine oxide was used as a hydrogen bond acceptor in a molar ratio of 2:1. The mixture was heated and stirred to form a hydrophobic deep eutectic solvent. A salt lake brine containing 30.37 g / L boric acid and pH = 1.4 was used as a raw material. A single-stage extraction was performed under the conditions of a volume ratio of brine to hydrophobic deep eutectic solvent of 1:1, 2:1, 4:1, and 8:1. The extraction time was 10 minutes. After the extraction equilibrium was reached, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration in the solution was tested.

[0051] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, and 8:1 were 97.82%, 94.29%, 73.96%, and 45.14%, respectively. A 0.5 mol / L sodium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic solution to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0052] Example 6

[0053] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and tri-n-octylphosphine oxide was used as a hydrogen bond acceptor in a molar ratio of 2:1. The mixture was heated and stirred to form a hydrophobic deep eutectic solvent. A salt lake brine containing 16.99 g / L boric acid and pH = 5.5 was used as a raw material. A single-stage extraction was performed under the conditions of a volume ratio of brine to hydrophobic deep eutectic solvent of 1:1, 2:1, 4:1, and 8:1. The extraction time was 10 minutes. After the extraction was balanced, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration in the solution was tested.

[0054] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, and 8:1 were 97.46%, 94.51%, 79.36%, and 54.17%, respectively. A 0.5 mol / L potassium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic solution to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0055] Example 7

[0056] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and Cyanex 923 as a hydrogen bond acceptor at a molar ratio of 5:1. The hydrophobic deep eutectic solvent was formed by heating and stirring. A salt lake brine containing 4.29 g / L boric acid and pH = 2.4 was used as a raw material. The volume ratio of brine to hydrophobic deep eutectic solvent was 1:1, 2:1, 4:1, 8:1, 16:1. Single-stage extraction was performed. The extraction time was 10 min. After the extraction was balanced, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration in the solution was tested.

[0057] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, 8:1, and 16:1 were 97.51%, 95.96%, 91.31%, 79.31%, and 61.09%, respectively. A 0.5 mol / L sodium hydroxide aqueous solution or a 0.5 mol / L potassium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic phase to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0058] Example 8

[0059] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and Cyanex 923 as a hydrogen bond acceptor at a molar ratio of 5:1. The hydrophobic deep eutectic solvent was formed by heating and stirring. A salt lake brine containing 30.37 g / L boric acid and pH = 1.4 was used as a raw material. The volume ratio of brine to hydrophobic deep eutectic solvent was 1:1, 2:1, 4:1, 8:1. Single-stage extraction was performed. The extraction time was 10 min. After the extraction was balanced, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration u in the solution was tested.

[0060] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, and 8:1 were 97.46%, 95.29%, 79.36%, and 51.17%, respectively. A 0.5 mol / L sodium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic solution to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0061] Example 9

[0062] 2,2,4-trimethyl-1,3-pentanediol was used as a hydrogen bond donor and Cyanex923 as a hydrogen bond acceptor at a molar ratio of 5:1. The mixture was heated and stirred to form a hydrophobic deep eutectic solvent. A salt lake brine containing 16.99 g / L boric acid and pH = 5.5 was used as a raw material. The volume ratio of brine to hydrophobic deep eutectic solvent was 1:1, 2:1, 4:1, 8:1, 16:1. Single-stage extraction was performed. The extraction time was 10 min. After the extraction was balanced, the mixture was centrifuged, the lower aqueous solution was taken, and the boric acid concentration in the solution was tested.

[0063] It was determined that the extraction rates of different volume ratios of 1:1, 2:1, 4:1, 8:1, and 16:1 were 97.05%, 94.72%, 87.65%, 64.69%, and 40.76%, respectively. A 0.5 mol / L sodium hydroxide aqueous solution was used as a stripping agent to strip the obtained boron-containing organic solution. The volume ratio of the boron-containing organic solution to the stripping agent was 2:1, and the stripping was carried out at 20°C for 20 minutes. After standing and stratifying, an aqueous solution containing boric acid was obtained. After measurement and calculation, the stripping rate exceeded 90.00%.

[0064] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0065] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A hydrophobic deep eutectic solvent for extracting boric acid from salt lake brine, characterized in that: It comprises a hydrogen bond donor and a hydrogen bond acceptor, wherein the hydrogen bond donor comprises a diol compound containing a dihydroxyl group, and the hydrogen bond acceptor comprises a compound containing a phosphorus-oxygen double bond; the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 5:1 to 1:

2.

2. The hydrophobic deep eutectic solvent according to claim 1, wherein the hydrogen bond donor comprises any one of 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diaryl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-3-benzyl-1,3-butanediol, 2-benzyl-2,4-pentanediol, and 2,2-dimethyl-1-benzyl-1,3-propanediol, or a combination of two or more alcohol compounds; The hydrogen bond acceptor has a structure as shown in formula (I), formula (II) or formula (III): in, R1 is any one of C3~C8 straight chain or branched alkyl, C3~C8 straight chain or branched substituted alkyl, phenyl, carboxyl, and amino; R2 is any one of C3~C8 straight chain or branched alkyl, C3~C8 straight chain or branched substituted alkyl, phenyl, carboxyl, and amino; R3 is any one of C3~C8 straight chain or branched alkyl, C3~C8 straight chain or branched substituted alkyl, phenyl, carboxyl, and amino.

3. A method for extracting boric acid from salt lake brine, characterized in that: The method uses the hydrophobic deep eutectic solvent for extracting boric acid from salt lake brine as described in any one of claims 1 to 2.

4. The method according to claim 3, characterized in that: The concentration of boric acid in the salt lake brine is 0.5-50 g / L.

5. The method according to claim 3, characterized in that: The volume ratio of the hydrophobic deep eutectic solvent to the salt lake brine is 1:16 to 1:

5.

6. The method according to claim 3, characterized in that: The pH of the salt lake brine is in the range of 1-9.

7. The method according to claim 3, characterized in that: In the process of mixing and extracting the hydrophobic deep eutectic solvent with salt lake brine, the extraction temperature is 5 to 40° C. and the extraction time is 5 to 15 minutes to obtain a boron-containing organic solution.

8. The method according to claim 3, characterized in that: The method also includes: using a stripping agent to strip the boron-containing organic solution to obtain a boron-containing aqueous solution.

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