An extraction system for separating boron under alkaline conditions and a method thereof

Abstract

The application discloses an extraction system for separating boron under alkaline conditions and a method thereof. The extraction system comprises a low eutectic solvent formed by an alcohol compound as a hydrogen bond donor and a salicylate compound as a hydrogen bond acceptor. The extraction system provided by the application has wider applicability, can efficiently extract and separate boron from acidic and alkaline solutions, realizes efficient extraction of boron in different solution environments, and even under the condition that pH is greater than 9, the extraction rate of boron can still reach more than 90%. In addition, the extraction system of the application is simple to prepare, low in cost, good in boron separation effect, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of separation technology, specifically relating to an extraction system and method for separating boron under alkaline conditions. Background Technology

[0002] Boron, as an important strategic resource in my country, occupies a crucial position in the strategic development of new energy, low-carbon economy, and nuclear industry. With the rapid development of energy storage electronics and nuclear energy, the demand for boron has increased dramatically both domestically and internationally. Currently, China's total boron reserves (calculated as B2O3) are also abundant, mainly distributed in boron-rich ores and salt lake brines. However, with continuous mining, boron-magnesium ore reserves are rapidly decreasing and their grade is declining, leading to a severe shortage of boron ore resources. Therefore, recovering lithium and boron resources from salt lake brines is of great significance for meeting the needs of my country's strategic economic development and ensuring national energy security. Currently, the main methods for extracting boron from salt lake brines include acidification, precipitation, adsorption, and solvent extraction. Among these, solvent extraction is suitable for brine systems with boron content of 2-18 g / L, has lower limitations on the boron content in the solution, and has advantages such as high selectivity, simple operation, and recyclable extractant, making it widely used. Currently, commonly used boron extractants mainly include monohydric fatty alcohols, dihydric fatty alcohols, monohydric / dihydric mixed alcohols, hydroxyl-containing aromatic compounds, and hydroxyl-containing amine compounds. Fatty alcohol extractants have advantages such as high extraction rate, wide availability, low price, and ease of industrial application, and are widely used in boron extraction from chloride and sulfate-type salt lakes. Monohydric alcohols are mainly suitable for boron extraction from high-magnesium salt lake brines, but they require a large number of extraction stages. Dihydric alcohols, due to their ability to form more stable five- or six-membered ring borate esters with boric acid, have a higher single-stage extraction rate than monohydric alcohols, but they suffer from high viscosity and high solubility. Studies have found that mixing monohydric alcohols and / or dihydric alcohols can improve extraction efficiency and reduce extractant solubility. For example, mixing n-octanol and isoamyl alcohol for boron extraction achieves a multi-stage countercurrent extraction yield of over 99%; a mixture of 2-ethyl-1,3-hexanediol and isooctanol for boron extraction from high-magnesium salt lake brines achieves an extraction rate far higher than that of using monohydric alcohols alone.

[0003] However, the aforementioned systems can only extract and separate boron from acidic or neutral boron-containing solutions. For high-pH solutions, such as alkaline brine from salt lakes with a pH > 8, these systems cannot extract boron. An acid solution needs to be added to adjust the pH of the solution to below 5 before extraction, which not only leads to additional material consumption but also increases the production cost of boron separation. Therefore, developing a method for separating boron under alkaline conditions is an urgent problem to be solved. Summary of the Invention

[0004] The main objective of this invention is to provide an extraction system and method for separating boron under alkaline conditions, overcoming the shortcomings of existing technologies for the extraction and separation of boron from other metal elements in alkaline boron-containing solutions. Currently, monohydric alcohols can extract and separate boric acid from slightly acidic solutions, but this method becomes unusable once the pH value exceeds 5. Dihydric alcohol systems have a slightly wider applicable pH range than monohydric alcohols, but dihydric alcohols have very low solubility in low-polarity solvents, requiring the use of high-polarity solvents. However, high-polarity solvents are often highly toxic, which is detrimental to industrial applications. Furthermore, currently reported monohydric alcohol / dihydric alcohol mixed systems only show good extraction effects on acidic boron-containing solutions, and are difficult to achieve for the extraction and separation of boron from alkaline solutions.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides an extraction system for separating boron under alkaline conditions, the extraction system comprising a low eutectic solvent formed by an alcohol compound as a hydrogen bond donor and a salicylate ester compound as a hydrogen bond acceptor.

[0007] The embodiments of the present invention also provide the application of the aforementioned extraction system for separating boron under alkaline conditions in the separation of boron, preferably the application in the separation of boron in alkaline solutions.

[0008] This invention also provides a method for separating boron from an alkaline solution, comprising:

[0009] The aforementioned extraction system for separating boron under alkaline conditions is provided;

[0010] Furthermore, the extraction system is mixed with an alkaline boron-containing solution for extraction and back-extraction to achieve the separation and enrichment of boron.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] (1) In the extraction system provided by the present invention, alcohols are used as hydrogen bond donors and salicylic acid esters are used as hydrogen bond acceptors to form a low eutectic solvent. This system has high selectivity for boron and has advantages such as wide applicable pH, low system viscosity, and easy phase separation, which are not available in other current boron extraction systems.

[0013] (2) The extraction system provided by the present invention has a wider range of applicability and can efficiently extract and separate boron from acidic, neutral and alkaline solutions, achieving efficient extraction of boron in different solution environments. Even under conditions where pH is greater than 9, the boron extraction rate can still reach more than 90%. In addition, the extraction system of the present invention is simple to prepare, has low cost, and has good boron separation effect, and has a good application prospect. Detailed Implementation

[0014] In view of the deficiencies of existing technologies, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. This invention proposes a novel low-eutectic extraction system based on mixed alcohols / salicylic acid esters, which achieves selective separation of boron from other metal ions in alkaline boron-containing solutions through selective extraction of boron. The extraction system mentioned in this invention uses mono- / diols as hydrogen bond donors and salicylic acid esters as hydrogen bond acceptors to form a low-eutectic solvent for boron extraction. The phenolic hydroxyl groups in the salicylic acid esters can undergo coordination extraction with the polycyclic boron compounds under alkaline conditions. Simultaneously, the hydroxyl groups in the salicylic acid esters form a low-eutectic solvent with the alcohols through hydrogen bonds, greatly increasing the fluidity and extraction capacity of the entire system. Even under conditions with a pH greater than 9, the boron extraction rate can still reach over 90%. Furthermore, the extraction system of this invention is simple to prepare, low in cost, and has good boron separation effect, showing great application prospects.

[0015] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Specifically, as one aspect of the technical solution of the present invention, an extraction system for separating boron under alkaline conditions includes a low eutectic solvent formed by an alcohol compound as a hydrogen bond donor and a salicylate ester compound as a hydrogen bond acceptor.

[0017] In some preferred embodiments, the salicylates include salicylates having a phenolic hydroxyl group and an ortho-benzoic acid group.

[0018] Furthermore, the salicylate ester compounds include any one or a combination of two or more of isooctyl salicylate, n-octyl salicylate, butyl salicylate, propyl salicylate, hexyl salicylate, and isoamyl salicylate, and are not limited thereto.

[0019] In some preferred embodiments, the alcohol compounds include, but are not limited to, monohydric alcohols and / or dihydric alcohols.

[0020] Furthermore, the alcohol compound is a mixture of monohydric alcohols and dihydric alcohols.

[0021] In some preferred embodiments, the alcohol compounds include any one or more combinations of 2,2,4-trimethyl-1,3-pentanediol, 2,2,5-trimethyl-1,3-hexanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-ethylhexanol, isooctanol, n-octanol, dodecyl alcohol, and A1416 mixed alcohols, and are not limited thereto.

[0022] In some preferred embodiments, the molar ratio of the alcohol compound to the salicylate compound is 1-10:10-1.

[0023] The extraction system used in this invention is a low eutectic solvent formed by alcohol / salicylic acid ester. This not only overcomes the problem that diols are difficult to dissolve in conventional solvents, but also greatly promotes the ability of alcohol / ester to form complexes with borates because the alcohol / ester directly forms a low eutectic system. In addition, salicylic acid ester itself can also coordinate with boron, thus making it more widely applicable. Even in solutions with pH > 9, the extraction rate of boron can still reach more than 90%.

[0024] Another aspect of the present invention provides the application of the aforementioned extraction system for separating boron under alkaline conditions in the separation of boron, preferably in the separation of boron from alkaline solutions.

[0025] Another aspect of the present invention provides a method for separating boron from an alkaline solution, comprising:

[0026] The aforementioned extraction system for separating boron under alkaline conditions is provided;

[0027] Furthermore, the extraction system is mixed with an alkaline boron-containing solution for extraction and back-extraction to achieve the separation and enrichment of boron.

[0028] In some preferred embodiments, the alkaline boron-containing solution is brine from a salt lake with a pH value greater than 7.

[0029] In some preferred embodiments, the concentration of boron in the alkaline boron-containing solution is 0.5 g / L to 30 g / L.

[0030] In some preferred embodiments, the pH value of the alkaline boron-containing solution is greater than 8.

[0031] In some preferred embodiments, the alkaline boron-containing solution further includes alkali metal ions, which include any one or more combinations of lithium, sodium, potassium, rubidium, and cesium, and are not limited thereto.

[0032] In some preferred embodiments, the anions in the alkaline boron-containing solution include any one or more combinations of hydroxide ions, carbonate ions, chloride ions, sulfate ions, nitrate ions, and organic acid ions, and are not limited thereto.

[0033] Furthermore, the organic acid anions include, but are not limited to, citrate anions.

[0034] In some preferred embodiments, the volume ratio of the extraction system to the alkaline boron-containing solution during the extraction process is 1:20-20:1, that is, the O / A ratio during the extraction process is 1 / 20-20 / 1.

[0035] In some preferred embodiments, the extraction includes single-stage extraction or cascade extraction.

[0036] Furthermore, the single-stage extraction time is 1-120 min.

[0037] Furthermore, the number of stages in the cascade extraction is 2-10.

[0038] In some preferred embodiments, the volume ratio of the boron-rich solution obtained during the back-extraction process to the back-extraction solution is 1:20-20:1, that is, the ratio of O / A during the back-extraction process is 1 / 20-20 / 1.

[0039] In some preferred embodiments, the back-extraction includes single-stage back-extraction or cascade extraction.

[0040] Furthermore, the single-stage back-extraction time is 1-120 min.

[0041] Furthermore, the number of stages in the cascade back-extraction is 2-10.

[0042] In some preferred embodiments, the back-extraction solution used in the back-extraction process includes an alkaline solution.

[0043] Furthermore, the alkaline solution includes any one or more combinations of sodium hydroxide, potassium hydroxide, and lithium hydroxide, but is not limited thereto.

[0044] Furthermore, the concentration of hydroxide ions in the alkaline solution is 0.01 mol / L to 2 mol / L.

[0045] This patent proposes a highly effective synergistic extraction system for boron based on alcohols / salicylic acid esters as a low eutectic solvent, and applies it to the extraction of boron from alkaline boron-containing solutions. In this extraction system, alcohols act as hydrogen bond donors and salicylic acid esters as hydrogen bond acceptors, forming a low eutectic solvent. This system exhibits high selectivity for boron and possesses advantages not found in other current boron extraction systems, such as a wide applicable pH range, low system viscosity, and easy phase separation.

[0046] The salicylate compounds involved in this invention include isooctyl salicylate, n-octyl salicylate, butyl salicylate, propyl salicylate, hexyl salicylate, isoamyl salicylate, and other salicylate compounds having phenolic hydroxyl groups and ortho-benzoic acid groups. The alcohol compounds are diols such as 2,2,4-trimethyl-1,3-pentanediol, 2,2,5-trimethyl-1,3-hexanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, and 2-butyl-2-ethyl-1,3-propanediol, as well as monools such as 2-ethylhexanol, isooctyl alcohol, n-octanol, dodecyl alcohol, and A1416 mixed alcohols.

[0047] The alkaline boron-containing solution described in this invention refers to a boron-containing solution with a pH range of 7-14, the pH of which is adjusted by sodium hydroxide, potassium hydroxide, lithium hydroxide or ammonium solution, wherein the concentration of boron ranges from 0.5 g / L to 30 g / L, and other coexisting ions are mainly alkali metal ions such as lithium, sodium, potassium, rubidium and cesium, and coexisting anions, in addition to hydroxide ions, are carbonate ions, chloride ions, sulfate ions, nitrate ions and organic acid anions such as citrate ions.

[0048] Compared to O / A = 1 / 20-20 / 1, the extraction process described in this invention has a single-stage oscillating extraction time of 1 min-120 min and a cascade extraction stage of 2-10 stages.

[0049] In the back-extraction process described in this invention, the back-extraction solution is an alkaline solution such as sodium hydroxide, potassium hydroxide, or lithium hydroxide, with a hydroxide ion concentration of 0.01 mol / L to 2 mol / L. The back-extraction ratio is O / A = 1 / 20 to 20 / 1. The single-stage back-extraction shaking time is 1 min to 120 min, and the number of cascade back-extraction stages is 2 to 10.

[0050] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments. These embodiments are implemented on the premise of the technical solution of the invention, and provide detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0051] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0052] Example 1

[0053] 2,2,4-Trimethyl-1,3-pentanediol was used as the hydrogen bond donor, and isooctyl salicylate was used as the hydrogen bond acceptor, with a molar ratio of 1:4. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 5 g / L boron trioxide and with a pH of 9.3 as raw material, a single-stage extraction was performed under a phase ratio of O / A = 1 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0054] The concentration of boron trioxide in the extract residue was determined to be 1.0 g / L, and the extraction rate was calculated to be 80%.

[0055] The boron-loaded organic phase was back-extracted with a sodium hydroxide solution at a concentration of 0.5 mol / L. The back-extraction ratio was O / A = 1 / 1, the back-extraction time was 5 min, and the extraction stage was 1. After the back-extraction reached equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then determined by titration.

[0056] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 3.5 g / L, the calculated back-extraction rate was 87.5%, and the total yield was approximately 70%.

[0057] Example 2

[0058] 2,2,4-Trimethyl-1,3-pentanediol was used as the hydrogen bond donor, and butyl salicylate was used as the hydrogen bond acceptor, with a molar ratio of 1:2. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 5 g / L boron trioxide and with a pH of 9.3 as raw material, a single-stage extraction was performed under a phase ratio of O / A = 2 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0059] The concentration of boron trioxide in the extract residue was determined to be 0.5 g / L, and the extraction rate was calculated to be 90%.

[0060] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 1.0 mol / L. The back-extraction ratio was O / A = 2 / 1, the back-extraction time was 5 min, and the back-extraction stage was 1. After the back-extraction reached equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then determined by titration.

[0061] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 7.2 g / L, the calculated back-extraction rate was 80%, and the total yield was approximately 72%.

[0062] Example 3

[0063] 2,2,4-Trimethyl-1,3-hexanediol and n-octanol were used as hydrogen bond donors, and amyl salicylate was used as a hydrogen bond acceptor, with a molar ratio of 1:1:2. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 4 g / L boron trioxide and with a pH of 8.0 as raw material, a single-stage extraction was performed under a phase ratio of O / A = 1 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0064] The concentration of boron trioxide in the extract residue was determined to be 0.2 g / L, and the extraction rate was calculated to be 95%.

[0065] The boron-loaded organic phase was back-extracted with a sodium hydroxide solution at a concentration of 0.5 mol / L. The back-extraction ratio was O / A = 2 / 1, the back-extraction time was 5 min, and the back-extraction stage was 1. After the back-extraction reached equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then determined by titration.

[0066] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 6.8 g / L, the calculated back-extraction rate reached 90%, and the total yield was approximately 85.5%.

[0067] Example 4

[0068] 2-Butyl-2-ethyl-1,3-propanediol and dodecanol were used as hydrogen bond donors, and isooctyl salicylate was used as a hydrogen bond acceptor, with a molar ratio of 1:0.5:3. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 4 g / L boron trioxide and with a pH of 8.0 as raw material, a three-stage countercurrent extraction was performed under a phase ratio of O / A = 1 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0069] The concentration of boron trioxide in the extract residue was determined to be 0.02 g / L, and the extraction rate was calculated to be 99.5%.

[0070] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 0.5 mol / L. The back-extraction ratio was O / A = 2 / 1, and the back-extraction time was 5 min. Two-stage countercurrent back-extraction was performed. After reaching equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then titrated to determine its concentration.

[0071] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 7.56 g / L, the calculated back-extraction rate was 95%, and the total yield was approximately 89.3%.

[0072] Example 5

[0073] 2,2,4-Trimethyl-1,3-hexanediol and 2-ethylhexanol were used as hydrogen bond donors, and isooctyl salicylate was used as a hydrogen bond acceptor, with a molar ratio of 1:0.2:3. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 4 g / L boron trioxide and with a pH of 8.0 as raw material, a three-stage countercurrent extraction was performed under a phase ratio of O / A = 1 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0074] The concentration of boron trioxide in the extract residue was determined to be 0.02 g / L, and the extraction rate was calculated to be 99.5%.

[0075] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 0.5 mol / L. The back-extraction ratio was O / A = 2 / 1, and the back-extraction time was 5 min. Two-stage countercurrent back-extraction was performed. After reaching equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then titrated to determine its concentration.

[0076] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 7.56 g / L, the calculated back-extraction rate was 95%, and the total yield was approximately 89.3%.

[0077] Example 6

[0078] 2-Ethyl-1,3-hexanediol and 2-ethylhexanol were used as hydrogen bond donors, and isooctyl salicylate was used as a hydrogen bond acceptor, with a molar ratio of 1:0.2:3. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 4 g / L boron trioxide and with a pH of 8.0 as raw material, a three-stage countercurrent extraction was performed under a phase ratio of O / A = 1 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0079] The concentration of boron trioxide in the extract residue was determined to be 0.02 g / L, and the extraction rate was calculated to be 99.5%.

[0080] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 0.5 mol / L. The back-extraction ratio was O / A = 2 / 1, and the back-extraction time was 5 min. Two-stage countercurrent back-extraction was performed. After reaching equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then titrated to determine its concentration.

[0081] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 7.56 g / L, the calculated back-extraction rate was 95%, and the total yield was approximately 89.3%.

[0082] Example 7

[0083] 2-Ethyl-1,3-hexanediol and 2-ethylhexanol were used as hydrogen bond donors, and isooctyl salicylate was used as a hydrogen bond acceptor, with a molar ratio of 1:2:3. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 2 g / L boron trioxide and with a pH of 6.5 as raw material, a three-stage countercurrent extraction was performed under a phase ratio of O / A = 1 / 2 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0084] The concentration of boron trioxide in the extract residue was determined to be 0.02 g / L, and the extraction rate was calculated to be 99%.

[0085] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 0.5 mol / L. The back-extraction ratio was O / A = 2 / 1, and the back-extraction time was 5 min. Two-stage countercurrent back-extraction was performed. After reaching equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then titrated to determine its concentration.

[0086] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 7.56 g / L, the calculated back-extraction rate was 95%, and the total yield was approximately 89.3%.

[0087] Example 8

[0088] 2-Ethyl-1,3-hexanediol was used as the hydrogen bond donor, and isooctyl salicylate was used as the hydrogen bond acceptor, with a molar ratio of 1:3. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 5 g / L boron trioxide and with a pH of 5 as raw material, a three-stage countercurrent extraction was performed under a phase ratio of O / A = 1 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0089] The concentration of boron trioxide in the extract residue was determined to be 0.05 g / L, and the extraction rate was calculated to be 99%.

[0090] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 0.25 mol / L, with a back-extraction ratio of O / A = 1 / 1 and a back-extraction time of 5 min. Three-stage countercurrent back-extraction was performed. After reaching equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then titrated to determine its concentration.

[0091] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 4.70 g / L, the calculated back-extraction rate was 99%, and the total yield was approximately 98.1%.

[0092] Example 9

[0093] 2-Ethyl-1,3-hexanediol and 2-ethylhexanol were used as hydrogen bond donors, and isooctyl salicylate was used as a hydrogen bond acceptor, with a molar ratio of 1:2:3. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 15 g / L boron trioxide and with a pH of 5.5 as raw material, a three-stage countercurrent extraction was performed under a phase ratio of O / A = 4 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0094] The concentration of boron trioxide in the extract residue was determined to be 0.75 g / L, and the extraction rate was calculated to be 95%.

[0095] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 0.25 mol / L, with a back-extraction ratio of O / A = 1 / 1 and a back-extraction time of 5 min. Three-stage countercurrent back-extraction was performed. After reaching equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then titrated to determine its concentration.

[0096] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 3.56 g / L, the calculated back-extraction rate was 95%, and the total yield was approximately 90.3%.

[0097] Comparative Example 1

[0098] 2,2,4-Trimethyl-1,3-pentanediol was used as the hydrogen bond donor, and menthol as the hydrogen bond acceptor, with a molar ratio of 2:1. The mixture was heated and stirred to form a low-eutectic solvent. Using a salt lake brine containing 12 g / L boron trioxide and with a pH of 7 as raw material, a single-stage extraction was performed under a phase ratio of O / A = 1:1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated. It should be noted that after the mixture cooled naturally to room temperature, a large amount of solid crystals formed, making normal extraction impossible. Therefore, extraction requires conditions above 40 degrees Celsius.

[0099] The concentration of boron trioxide in the extract residue was determined to be 4.0 g / L, and the extraction rate was calculated to be 67%.

[0100] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 0.25 mol / L, with a back-extraction ratio of O / A = 1 / 1 and a back-extraction time of 5 min. Single-stage back-extraction was performed, and after equilibrium was reached, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then titrated to determine its concentration.

[0101] The concentration of boron trioxide in the back-extraction aqueous phase was determined to be 6.5 g / L, the calculated back-extraction rate was 81%, and the total yield was approximately 54.3%.

[0102] Comparative Example 2

[0103] 2,2,4-Trimethyl-1,3-hexanediol was used as the hydrogen bond donor, and thymol as the hydrogen bond acceptor, with a molar ratio of 2:1. The mixture was stirred to form a low-eutectic solvent. Using a salt lake brine containing 6 g / L boron trioxide and with a pH of 9 as raw material, a single-stage extraction was performed under a phase ratio of O / A = 1 / 1 for 5 minutes. After extraction equilibrium, the mixture was allowed to stand and undergo natural phase separation. The boron content in the solution was then titrated.

[0104] The concentration of boron trioxide in the extract residue was determined to be 1.5 g / L, and the extraction rate was calculated to be 75%.

[0105] The boron-loaded organic phase was back-extracted with sodium hydroxide solution at a concentration of 0.5 mol / L, with a back-extraction ratio of O / A = 1 / 1 and a back-extraction time of 5 min. Single-stage back-extraction was performed, and after equilibrium was reached, the mixture was allowed to stand and undergo natural phase separation. The boron in the back-extraction solution was then determined by titration.

[0106] The concentration of boron trioxide in the aqueous phase of the back-extraction was determined to be 4.0 g / L, with a calculated back-extraction rate of 89% and a total yield of approximately 67%. It is worth noting that thymol has a strong corrosive effect and its practical application does not comply with production safety management regulations.

[0107] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0108] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. An extraction system for separating boron under alkaline conditions, characterized in that, The extraction system comprises a low eutectic solvent formed by an alcohol compound as a hydrogen bond donor and a salicylate compound as a hydrogen bond acceptor; wherein the alcohol compound comprises any one or a combination of two or more of 2,2,4-trimethyl-1,3-pentanediol, 2,2,5-trimethyl-1,3-hexanediol, 2-ethyl-2-butyl-1,3-propanediol, and 2-ethyl-1,3-hexanediol; the salicylate compound comprises any one or a combination of two or more of isooctyl salicylate, n-octyl salicylate, butyl salicylate, propyl salicylate, hexyl salicylate, and isoamyl salicylate; and the molar ratio of the alcohol compound to the salicylate compound is 1~10:10~1.

2. The application of the extraction system for separating boron under alkaline conditions as described in claim 1 in the separation of boron from alkaline solutions.

3. A method for separating boron from an alkaline solution, characterized in that, include: Provides the extraction system for separating boron under alkaline conditions as described in claim 1; Furthermore, the extraction system is mixed with an alkaline boron-containing solution for extraction and back-extraction to achieve the separation and enrichment of boron; wherein the pH value of the alkaline boron-containing solution is greater than 8.

4. The method according to claim 3, characterized in that: The concentration of boron in the alkaline boron-containing solution is 0.5 g / L to 30 g / L.

5. The method according to claim 3, characterized in that: The alkaline boron-containing solution also includes alkali metal ions, which include any one or more combinations of lithium, sodium, potassium, rubidium, and cesium.

6. The method according to claim 3, characterized in that: The anions in the alkaline boron-containing solution include any one or more combinations of hydroxide ions, carbonate ions, chloride ions, sulfate ions, nitrate ions, and citrate ions.

7. The method according to claim 3, characterized in that: During the extraction process, the volume ratio of the extraction system to the alkaline boron-containing solution is 1:20-20:

1.

8. The method according to claim 3, characterized in that: The extraction includes single-stage extraction or cascade extraction; wherein the time for single-stage extraction is 1-120 min; and the number of stages for cascade extraction is 2-10.

9. The method according to claim 3, characterized in that: During the back-extraction process, the volume ratio of the boron-rich solution obtained from the extraction to the back-extraction solution is 1:20-20:

1.

10. The method according to claim 3, characterized in that: The back-extraction includes single-stage back-extraction or cascade back-extraction; wherein the time of single-stage back-extraction is 1-120 min; and the number of stages of cascade back-extraction is 2-10 stages.

11. The method according to claim 3, characterized in that: The back-extraction process uses a back-extraction solution comprising any one or more alkaline solutions selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide; the concentration of hydroxide ions in the alkaline solution is 0.01 mol / L to 2 mol / L.