Boric acid extractant and method of extracting boric acid

Abstract

The application provides a boric acid extractant and a method for extracting boric acid. The boric acid extractant comprises, in percentage by volume, 20-60% of a diluent, 10-40% of a monohydric alcohol, 10-40% of a dihydric alcohol and 5-20% of an ionic liquid; the ionic liquid is selected from any one or more of imidazole ionic liquids, pyridine ionic liquids and quaternary phosphonium ionic liquids, the cation of the ionic liquid contains an alkyl side chain, and the anion of the ionic liquid is selected from any one or more of bis-trifluoromethanesulfonimide, hexafluorophosphate, hydrogen sulfate and methyl sulfonate. The boric acid extractant of the application adopts a four-component system of'monohydric alcohol + dihydric alcohol + ionic liquid + diluent', has a clear synergistic extraction effect, can improve the single-stage extraction rate, greatly reduces the solution loss of the extractant, and is not prone to emulsification and phase separation.

Description

Technical Field

[0001] This invention relates to the field of salt lake chemical technology, and more specifically, to a boric acid extractant and a method for extracting boric acid. Background Technology

[0002] Boron is an important chemical raw material, widely used in glass and ceramics industries. Salt lake brines contain abundant liquid boron resources, making the efficient and environmentally friendly extraction of boric acid from them of great significance. Currently, methods for extracting boron from salt lake brines mainly include acidification crystallization, ion exchange, adsorption, and solvent extraction. Solvent extraction has attracted considerable attention due to its advantages such as minimal limitation by the boric acid content in the solution, short process flow, simple equipment, and ease of operation.

[0003] Extractive solvents for boron extraction are mostly alcohols. The extraction mechanism of monohydric fatty alcohol extraction systems involves the formation of borate esters from boric acid in acidified brine using the monohydric fatty alcohol. The single-stage extraction rate of monohydric fatty alcohols is around 80%, and efficient boron extraction requires strong salting out and high acidity conditions. Significant problems remain in industrial applications: firstly, solvent loss leads to high costs; secondly, it results in significant organic pollution in the effluent. While diols can form stable five-membered and six-membered ring borate esters with boric acid, offering higher extraction efficiency than monohydric alcohols, their higher cost, higher viscosity, longer phase separation time, and greater solubility in the aqueous phase limit their industrial application.

[0004] Even when monohydric alcohols are combined with dihydric alcohols, the water solubility of the dihydric alcohols remains high, leading to continuous loss of the extractant, increased operating costs, and environmental pollution. Furthermore, the high viscosity of dihydric alcohols means that when mixed with monohydric alcohols and diluents, emulsification is still likely to occur during extraction, making phase separation difficult and reducing mass transfer efficiency.

[0005] In recent years, ionic liquids have been introduced into boron extraction systems due to their unique physicochemical properties. Although the extractant in the Chinese patent application with patent publication number CN118341122A contains ionic liquid, the extraction system still mainly relies on the esterification reaction of the monohydric alcohol after the macromolecular monohydric alcohol is combined with the ionic liquid, and fails to give full play to the stability advantage of the dihydric alcohol in forming a six-membered cyclic borate ester.

[0006] Chinese patent application CN119976870A uses 1-decyl-3-methylimidazolium trifluoromethanesulfonate as one of the extraction components, utilizing hydrogen bonding to promote the transfer of boric acid into the organic phase during extraction. However, this system requires back-extraction with hydrochloric acid aqueous solution. The high concentration of acid not only places higher demands on the corrosion resistance of the equipment but also leads to acidolysis loss of ionic liquids, thereby increasing the consumption of extractant and operating costs.

[0007] Therefore, there is an urgent need to develop a new green extraction system that can reduce solubility loss, inhibit emulsification, and improve extraction efficiency. Summary of the Invention

[0008] The main objective of this invention is to provide a boric acid extractant and a method for extracting boric acid, in order to solve the problems of high solubility, easy emulsification and phase separation, and low extraction rate of the extractants used in the extraction of boric acid from brine in the prior art.

[0009] To achieve the above objectives, according to one aspect of the present invention, a boric acid extractant is provided, comprising, by volume percentage: 20-60% diluent, 10-40% monohydric alcohol, 10-40% dihydric alcohol, and 5-20% ionic liquid; wherein the ionic liquid is selected from any one or more of imidazole ionic liquids, pyridine ionic liquids, and quaternary phosphonium ionic liquids, wherein the cation of the ionic liquid contains an alkyl side chain, and the anion of the ionic liquid is selected from any one or more of bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, hydrogen sulfate, and methanesulfonate.

[0010] Further, the ionic liquid is selected from any one or more of 1-dodecyl-3-methylimidazolium hydrogen sulfate, 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-tetradecylpyridine hydrogen sulfate, tetraalkylphosphonium hexafluorophosphate, and tetraalkylphosphonium bis(trifluoromethanesulfonyl)imide; and / or, the diluent is selected from any one or more of kerosene, sulfonated kerosene, solvent oil, n-dodecane, and heptane.

[0011] Furthermore, the monohydric alcohol is C5~C 10 Branched monohydric alcohols and / or C5~C 10 The monohydric alcohol is a straight-chain monohydric alcohol; preferably, the monohydric alcohol is selected from any one or more of isooctanol, n-octanol, isoamyl alcohol, heptanol and 2-ethylhexanol; and / or, the dihydric alcohol is 1,2-diol and / or 1,3-diol; wherein, the 1,2-diol is selected from any one or more of ethylene glycol, 1,2-propanediol and 1,2-butanediol; the 1,3-diol is selected from any one or more of 2-ethyl-1,3-hexanediol, 2,2,6-trimethyl-1,3-heptanediol, 2-butyl-2-ethyl-1,3-propanediol and 2,2,4-trimethyl-1,3-pentanediol; and / or, the volume ratio of the monohydric alcohol to the dihydric alcohol is 1:(0.5~4), preferably 1:(1~2).

[0012] Furthermore, the volume ratio of diluent, monohydric alcohol, dihydric alcohol and ionic liquid is 40~50:20~25:20~25:5~15.

[0013] According to another aspect of the present invention, a method for extracting boric acid using the above-mentioned boric acid extractant is provided. The method includes: step S1, mixing raw materials including a diluent, a monohydric alcohol, a dihydric alcohol, and an ionic liquid to obtain a boric acid extractant; step S2, subjecting a brine containing boron ions to a first acid treatment to adjust the pH value of the brine to <4, obtaining acid-treated brine; step S3, extracting the acid-treated brine using the boric acid extractant to obtain a boron-containing organic phase and an extracted solution; step S4, back-extracting the boron-containing organic phase using a back-extracting agent to obtain a boron-rich solution and an empty organic phase; the pH value of the back-extracting agent is ≥7; step S5, sequentially subjecting the boron-rich solution to evaporation and concentration, a second acid treatment, and cooling crystallization to obtain a boric acid product.

[0014] Furthermore, in step S2, the mass concentration of boron ions in the brine containing boron ions is 0.0002~10 g / L, preferably 1~5 g / L.

[0015] Further, in step S2, the brine is subjected to a first acid treatment using a first pH adjuster; the first pH adjuster is selected from any one or more of hydrochloric acid, sulfuric acid, and nitric acid; the pH value of the brine after acid treatment is ≤1.

[0016] Furthermore, in step S3, the O / A ratio of the extracted material is 1:1 to 1:4; the extraction temperature is 20 to 30°C; the extraction time is 5 to 30 minutes; and the number of extraction stages is 1 to 3.

[0017] Further, the back-extraction agent is water and / or an alkaline solution; wherein the alkaline solution is selected from any one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water and sodium carbonate solution; the molar concentration of the alkaline solution is 0.05~0.1 mol / L; and / or, the O / A ratio of the back-extraction is 1:1~1:2; the back-extraction temperature is 20~30℃, and the back-extraction time is 5~20 min; and / or, the empty organic phase is regenerated to obtain the regenerated boric acid extractant.

[0018] Further, in step S5, the boron-rich solution is evaporated and concentrated until the boron ion content is ≥10 g / L to obtain a concentrated solution; the concentrated solution is then subjected to a second acid treatment using a second pH adjuster to adjust the pH value to 0~2, resulting in an acid-treated solution; the acid-treated solution is then subjected to cooling crystallization, filtration, washing, and drying sequentially to obtain the boric acid product; wherein the second pH adjuster is selected from any one or more of hydrochloric acid, sulfuric acid, and nitric acid; and / or, the drying temperature is 50~80℃.

[0019] Applying the technical solution of this invention, the boric acid extractant of this application adopts a quaternary system of "monohydrin + dihydrin + ionic liquid + diluent," exhibiting a significant synergistic extraction effect. This system can improve the single-stage extraction rate, significantly reduce extractant loss, and is less prone to emulsification and phase separation. Specifically, the cations of the ionic liquid act as hydrogen bond acceptors, forming strong interactions with borate esters. Simultaneously, the micelles formed by its long alkyl side chains in the organic phase selectively enrich and extract borate esters at the phase interface, forming a synergistic extraction effect with the monohydric and dihydric alcohols. This improves the partition coefficient and extraction selectivity, thereby significantly increasing the single-stage extraction rate. Furthermore, the strong hydrophobicity of the ionic liquid effectively inhibits the migration of relatively hydrophilic dihydrins into the aqueous phase, reducing the overall water solubility of the extraction system. This solves the dihydrin loss problem and improves the phase separation performance of the dihydrin, preventing emulsification. This achieves efficient, low-consumption, and green extraction of boric acid, with almost zero loss of the ionic liquid itself. Furthermore, monohydric alcohols are low in cost, dihydric alcohols have excellent extraction performance, and ionic liquids provide synergistic effects. The combination of these three components results in excellent extraction effects for both high and low concentrations of boron. In summary, the boric acid extractant of this application not only achieves high extraction rates and high selectivity for boron but also possesses advantages such as low solubility, minimal phase separation, recyclability, and environmental friendliness, making it suitable for large-scale industrial production and application. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 The XRD pattern of the boric acid product in Example 1 of this application is shown. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] As analyzed in the background section of this application, the extractants used in the prior art for extracting boric acid from brine have problems such as high solubility, easy emulsification and phase separation, and low extraction rate. In order to solve the above problems, this application provides a boric acid extractant and a method for extracting boric acid.

[0024] In a typical embodiment of this application, a boric acid extractant is provided, comprising, by volume percentage: 20-60% diluent, 10-40% monohydric alcohol, 10-40% dihydric alcohol, and 5-20% ionic liquid; the ionic liquid is selected from any one or more of imidazole ionic liquids, pyridine ionic liquids, and quaternary phosphonium ionic liquids, wherein the cation of the ionic liquid contains an alkyl side chain with ≥8 carbon atoms, and the anion of the ionic liquid is selected from any one or more of bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, hydrogen sulfate, and methanesulfonate.

[0025] The boric acid extractant of this application adopts a quaternary system of "monohydrin + diol + ionic liquid + diluent", which has a significant synergistic extraction effect, can improve the single-stage extraction rate, significantly reduce the solubility loss of the extractant, and is not prone to emulsification and phase separation. Specifically, the cation of the ionic liquid can act as a hydrogen bond acceptor to form a strong interaction with the boric acid ester. At the same time, the micelles formed by its long alkyl side chains in the organic phase can selectively enrich and extract the boric acid ester at the phase interface, forming a synergistic extraction effect with the monohydric alcohol and diol, thereby improving the partition coefficient and extraction selectivity, and thus significantly improving the single-stage extraction rate. Meanwhile, the strong hydrophobicity of the ionic liquid can effectively inhibit the migration of the relatively hydrophilic diol to the aqueous phase, reducing the overall water solubility of the extraction system, thereby solving the solubility loss problem of the diol, improving the phase separation performance of the diol, and preventing emulsification. This achieves efficient, low-consumption, and green extraction of boric acid, with almost zero solubility loss of the ionic liquid itself. Furthermore, monohydric alcohols are low in cost, dihydric alcohols have excellent extraction performance, and ionic liquids provide synergistic effects. The combination of these three components results in excellent extraction effects for both high and low concentrations of boron. In summary, the boric acid extractant of this application not only achieves high extraction rates and high selectivity for boron but also possesses advantages such as low solubility, minimal phase separation, recyclability, and environmental friendliness, making it suitable for large-scale industrial production and application.

[0026] In one embodiment of this application, the ionic liquid is selected from any one or more of 1-dodecyl-3-methylimidazolium hydrogen sulfate, 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-tetradecylpyridine hydrogen sulfate, tetraalkylphosphonium hexafluorophosphate, and tetraalkylphosphonium bis(trifluoromethanesulfonyl)imide; and / or, the diluent is selected from any one or more of kerosene, sulfonated kerosene, solvent oil, n-dodecane, and heptane.

[0027] The preferred ionic liquids fall within the aforementioned range, which facilitates enhanced interaction with borate esters through the strong hydrogen bond acceptor function of the nitrogen atom in their cations. Simultaneously, the micelles formed by their long alkyl side chains in the organic phase further selectively enrich and extract borate esters at the phase interface, thereby further improving the extraction selectivity for boron. Furthermore, ionic liquids containing the aforementioned anions (especially bis(trifluoromethanesulfonyl)imide and hexafluorophosphate) exhibit strong hydrophobicity, which helps to better reduce the migration of diols into the aqueous phase, thereby reducing the water solubility of the extractant and decreasing the loss of the organic phase after extraction by 30-50%, while also reducing emulsion phase separation. Quaternary phosphonium-based ionic liquids possess high chemical stability, which helps to improve the performance stability of the extractant in complex brines, thus improving the extraction efficiency and effectiveness. Preferably, the alkyl side chains in the ionic liquid have ≥8 carbon atoms, more preferably 8-14.

[0028] Choosing a diluent within the above-mentioned range helps to reduce the viscosity of the organic phase after extraction and improve the flowability and phase separation performance of the extraction system.

[0029] In one embodiment of this application, the monohydric alcohol is C5~C6. 10 Branches and / or C5~C 10 The monohydric alcohol is a straight-chain monohydric alcohol; preferably, the monohydric alcohol is selected from any one or more of isooctanol, n-octanol, isoamyl alcohol, heptanol and 2-ethylhexanol; and / or, the dihydric alcohol is 1,2-diol and / or 1,3-diol; wherein, the 1,2-diol is selected from any one or more of ethylene glycol, 1,2-propanediol and 1,2-butanediol; the 1,3-diol is selected from any one or more of 2-ethyl-1,3-hexanediol, 2,2,6-trimethyl-1,3-heptanediol, 2-butyl-2-ethyl-1,3-propanediol and 2,2,4-trimethyl-1,3-pentanediol; and / or, the volume ratio of the monohydric alcohol to the dihydric alcohol is 1:(0.5~4), preferably 1:(1~2).

[0030] Preferably, the type of monohydric alcohol is within the above-mentioned range, which facilitates its rapid reaction with boric acid in the brine to form borate ester compounds, thereby improving the extraction rate of the boric acid extractant. Preferably, the type of dihydric alcohol is within the above-mentioned range, which facilitates its formation of stable five-membered and six-membered cyclic borate esters with boric acid, thereby improving the single-stage extraction rate of the boric acid extractant. Preferably, the volume ratio of monohydric alcohol to dihydric alcohol is within the above-mentioned range, which helps the boric acid extractant balance cost and extraction efficiency.

[0031] To further improve the extraction efficiency of boric acid extractant, in one embodiment of this application, the volume ratio of diluent, monohydric alcohol, dihydric alcohol and ionic liquid is 40~50:20~25:20~25:5~15.

[0032] The preferred volume ratio of monohydric alcohol, dihydric alcohol, and ionic liquid is 20~25:20~25:5~15, which helps to improve the synergistic effect of the three, thereby improving the boron partition coefficient while taking into account both cost and extraction performance, and thus achieving efficient extraction and rapid phase separation.

[0033] In another typical embodiment of this application, a method for extracting boric acid using the above-mentioned boric acid extractant is provided. The method includes: step S1, mixing raw materials including a diluent, a monohydric alcohol, a dihydric alcohol, and an ionic liquid to obtain a boric acid extractant; step S2, subjecting a brine containing boron ions to a first acid treatment to adjust the pH value of the brine to <4, obtaining acid-treated brine; step S3, extracting the acid-treated brine using the boric acid extractant to obtain a boron-containing organic phase and an extracted solution; step S4, back-extracting the boron-containing organic phase using a back-extraction agent to obtain a boron-rich solution and an empty organic phase; the pH value of the back-extraction agent is ≥7; step S5, sequentially evaporating and concentrating the boron-rich solution, performing a second acid treatment, and cooling crystallization to obtain a boric acid product.

[0034] In step S1, this application mixes a diluent, a monohydric alcohol, a dihydric alcohol, and an ionic liquid to obtain a boric acid extractant with a significant synergistic extraction effect. This improves the single-stage extraction rate, significantly reduces extractant loss, and is less prone to emulsification and phase separation. Since the form of boron ions in brine varies with pH, ​​in step S2, adjusting the brine pH to the aforementioned range allows boron ions in the brine to be converted into boric acid and stably exist as boric acid molecules. In step S3, the above-mentioned boric acid extractant is used to extract the acid-treated brine. The strong interaction between the ionic liquid in the boric acid extractant and the borate esters, along with the micelles formed by its long alkyl side chains in the organic phase, selectively enriches and extracts the borate esters at the phase interface, thereby improving the single-stage extraction rate. Simultaneously, the strong hydrophobicity of the ionic liquid effectively inhibits the migration of relatively hydrophilic dihydric alcohols into the aqueous phase, reducing extractant loss and improving dihydric alcohol phase separation performance, preventing emulsification, thus achieving efficient, low-consumption, and green extraction of boric acid. Compared to acidic stripping agents, this application uses a stripping agent with a pH value within the aforementioned range to strip the boron-containing organic phase in step S4. This avoids acid decomposition of imidazole or pyridine ionic liquids, thereby reducing ionic liquid loss. Furthermore, the addition of ionic liquids effectively reduces the viscosity of the extraction system, preventing emulsification and significantly accelerating phase separation during extraction and stripping. In step S5, the purity of the boric acid product is further improved by evaporating and concentrating the boron-rich solution, acidifying it, and cooling it to crystallize. In summary, the boric acid extraction method of this application achieves efficient, low-consumption, and green extraction of boric acid. This method not only boasts high extraction efficiency, low solvent loss, and fast phase separation, but also avoids acid decomposition losses of ionic liquids. It also offers advantages such as simple process, flexible operation, environmental friendliness, and good economic benefits, making it better suited for large-scale industrial production of boron extraction from brine.

[0035] In one embodiment of this application, in step S2, the mass concentration of boron ions in the brine containing boron ions is 0.0002~10 g / L, preferably 1~5 g / L.

[0036] The boric acid extractant of this application has excellent extraction effects for both high-concentration and low-concentration boron. It not only has high selectivity for boric acid, but also has low extraction rate for coexisting ions such as lithium and magnesium (lithium loss rate <5%) while efficiently extracting boron, which is beneficial for the subsequent recovery of lithium resources in brine.

[0037] In brine containing boron ions, the mass concentrations of lithium ions are 0.001–5 g / L, magnesium ions are 0.001–150 g / L, sodium ions are 0.001–200 g / L, silicon ions are 0.001–2 g / L, potassium ions are 0.001–50 g / L, calcium ions are 0.001–30 g / L, chloride ions are 1–400 g / L, and sulfate ions are 0.001–50 g / L.

[0038] In one embodiment of this application, in step S2, the brine is subjected to a first acid treatment using a first pH adjuster; the first pH adjuster is selected from any one or more of hydrochloric acid, sulfuric acid, and nitric acid; the pH value of the brine after acid treatment is ≤1.

[0039] Preferably using a pH adjuster within the aforementioned range helps to bring the pH of the acid-treated brine to this range, thereby rapidly and fully converting boron ions in the brine into boric acid and stabilizing the boric acid. Preferably, the pH of the acid-treated brine within the aforementioned range also helps to maximize the extraction partition coefficient of boric acid and reduce the occurrence of side reactions.

[0040] In one embodiment of this application, in step S3, the O / A ratio of the extracted material is 1:1 to 1:4; the extraction temperature is 20 to 30°C; the extraction time is 5 to 30 minutes; and the number of extraction stages is 1 to 3.

[0041] Optimal O / A ratios within the aforementioned range facilitate thorough phase separation, thereby improving extraction efficiency. Optimal extraction temperatures within the aforementioned range help reduce ionic liquid decomposition, alcohol volatilization, and other side reactions caused by high temperatures, maintaining the stability of the extractant and reducing energy consumption. Optimal extraction times within the aforementioned range ensure the extraction reaction proceeds fully while improving production efficiency. Optimal extraction stages within the aforementioned range help increase the boron extraction rate and reduce residual boron content in the post-extraction solution. Preferred extraction method is centrifugal extraction (optionally a three-stage countercurrent centrifugal extraction), which allows for phase separation within seconds. Compared to traditional mixing and clarifying tanks, centrifugal extraction significantly shortens the process cycle, thereby improving production efficiency.

[0042] In one embodiment of this application, in step S4, the back-extraction agent is water and / or an alkaline solution; wherein the alkaline solution is selected from any one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water and sodium carbonate solution; the molar concentration of the alkaline solution is 0.05~0.1mol / L; and / or, the O / A ratio of the back-extraction is 1:1~1:2; the back-extraction temperature is 20~30℃, and the back-extraction time is 5~20min; and / or, the empty organic phase is regenerated to obtain a regenerated boric acid extractant.

[0043] Preferring a specific type of back-extraction agent within the aforementioned range helps reduce hydrolysis or acidolysis of the ionic liquid, minimizing ionic liquid loss and thus reducing boric acid extractant consumption. It also facilitates extractant recycling. Preferring an O / A ratio within the aforementioned range helps ensure sufficient transfer of boric acid to the aqueous phase, reducing entrainment loss in the organic phase. Preferring a specific temperature and time within the aforementioned range helps improve back-extraction efficiency and reduce emulsion separation. Back-extraction can be performed in a two-stage countercurrent centrifugal extractor. Furthermore, the empty organic phase can be regenerated to restore extraction capacity, enabling recycling and reducing the need for fresh extractant replenishment, thereby lowering raw material costs.

[0044] In one embodiment of this application, in step S5, the boron-rich solution is evaporated and concentrated until the boron ion content is ≥10 g / L to obtain a concentrated solution; the concentrated solution is subjected to a second acid treatment using a second pH adjuster to adjust the pH value to 0~2 to obtain an acid-treated solution; the acid-treated solution is then subjected to cooling crystallization, filtration, washing, and drying to obtain a boric acid product; wherein the second pH adjuster is selected from any one or more of hydrochloric acid, sulfuric acid, and nitric acid; and / or the drying temperature is 50~80℃.

[0045] Evaporation and concentration of the boron-rich solution to achieve a boron ion content within the aforementioned range is preferred, as this facilitates rapid and complete crystallization of boric acid during subsequent cooling. A second acid treatment of the concentrated solution using a second pH adjuster of the aforementioned type to adjust its pH within the aforementioned range helps stabilize the boric acid in its molecular form, reducing the formation of borate impurities and decomposition or volatilization caused by high-temperature concentration. This, in turn, improves the purity and yield of boric acid crystals during subsequent cooling crystallization. Cooling crystallization further enhances the purity of boric acid to over 99.0%, meeting industrial-grade standards. Washing helps remove impurities. A drying temperature within the aforementioned range is preferred to remove moisture, yielding solid boric acid for easy storage and transportation.

[0046] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0047] Example 1

[0048] The brine composition is as follows: 1662.5 mg / L B ions, 396.9 mg / L Li ions, 319.7 mg / L Na ions, 79.3 mg / L Si ions, 22.3 mg / L K ions, and 12.6 mg / L SO42-. 2- 0.8 mg / L of Ca ions and 2300 mg / L of Cl ions.

[0049] Preparation of boric acid extractant: Diluent (kerosene), monohydric alcohol (n-octanol), dihydric alcohol (2-ethyl-1,3-hexanediol) and ionic liquid (1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) are mixed in a volume ratio of 40:20:25:15 to obtain boric acid extractant.

[0050] First acid treatment of brine: The pH of the brine is adjusted to 1 using hydrochloric acid to obtain acid-treated brine.

[0051] Extraction: A centrifugal extractor was used to extract the acid-treated brine with boric acid as the extractant. The O / A ratio was 1:1, the extraction temperature was 25℃, and the extraction time was 10 min. Two-stage countercurrent extraction was performed to obtain a boron-containing organic phase and the extracted solution. The phase separation time was 5 minutes, and no emulsification was observed.

[0052] Back-extraction: A centrifugal extractor was used to back-extract the boron-containing organic phase using a 0.05 mol / L NaOH solution. The O / A ratio was 1:1, the extraction temperature was 25℃, and the extraction time was 10 min, yielding a boron-rich solution and an empty organic phase. The empty organic phase was then regenerated to obtain the regenerated boric acid extractant.

[0053] Preparation of boric acid: A boron-rich solution was evaporated and concentrated until the boron ion content was 12 g / L, yielding a concentrated solution. The concentrated solution was then subjected to a second acid treatment with hydrochloric acid to adjust the pH to 1, yielding an acid-treated solution. The acid-treated solution was cooled to room temperature for crystallization and filtration. The filtered solid was washed with water and anhydrous ethanol and then dried at 60°C to obtain the boric acid product (solid). The XRD pattern of the boric acid product is shown below. Figure 1 As shown, the XRD pattern is consistent with the standard card.

[0054] Example 2

[0055] The difference from Example 1 is that the mass concentration of B ions in the brine is 452 mg / L.

[0056] Preparation of boric acid extractant: The diluent (sulfonated kerosene), monohydric alcohol (isooctanol), dihydric alcohol (2-ethyl-1,3-hexanediol) and ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) were mixed in a volume ratio of 45:20:25:10 to obtain the boric acid extractant.

[0057] First acid treatment of brine: The pH of the brine is adjusted to 1 using hydrochloric acid to obtain acid-treated brine.

[0058] Extraction: Boric acid was used as an extractant to extract the acid-treated brine. The O / A ratio was 1:1, the extraction temperature was 25℃, and the extraction time was 10 min. A single-stage extraction was performed to obtain a boron-containing organic phase and an extracted solution.

[0059] Back-extraction: The boron-containing organic phase was back-extracted using a 0.05 mol / L NaOH solution with an O / A ratio of 1:1, at a temperature of 25 °C, and for 10 min, resulting in a boron-rich solution and an empty organic phase.

[0060] Boric acid preparation: The boron-rich solution was evaporated and concentrated until the boron ion content was 12 g / L to obtain a concentrated solution. The solution was then treated with hydrochloric acid to adjust the pH to 1, resulting in an acid-treated solution. The acid-treated solution was then cooled at room temperature for crystallization and filtered. The filtered solid was washed with water and anhydrous ethanol and then dried at 60°C to obtain the boric acid product.

[0061] Example 3

[0062] The difference from Example 1 is that the mass concentration of B ions in the brine is 1.66 g / L. First acid treatment of the brine: The pH of the brine was adjusted to <1 using hydrochloric acid to obtain acid-treated brine.

[0063] Preparation of boric acid extractant: Kerosene, n-octanol, 2-ethyl-1,3-hexanediol and 1-dodecyl-3-methylimidazolium hydrogen sulfate were mixed in a volume ratio of 50:20:20:10 to obtain boric acid extractant, and finally boric acid product was obtained.

[0064] Example 4

[0065] The difference from Example 1 is that the mass concentration of B ions in the brine is 1.66 g / L. First acid treatment of the brine: The pH of the brine was adjusted to <1 using hydrochloric acid to obtain acid-treated brine.

[0066] Preparation of boric acid extractant: Kerosene, isooctyl alcohol, 2-ethyl-1,3-hexanediol and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt were mixed in a volume ratio of 35:20:30:15 to obtain boric acid extractant.

[0067] Extraction: The O / A ratio for extraction was 1:2, and the extraction time was 15 min.

[0068] Back-extraction process: Deionized water is used to back-extract the boron-containing organic phase to finally obtain the boric acid product.

[0069] Example 5

[0070] The difference from Example 1 lies in the extraction: extraction was carried out in a three-stage countercurrent centrifugal extractor at a speed of 3000 rpm and a total flow rate of 5 L / h for both phases. The back-extraction stage was completed in a two-stage countercurrent centrifugal extractor using deionized water as the back-extraction agent, ultimately yielding the boric acid product.

[0071] Example 6

[0072] The difference from Example 1 is that in the preparation of the boric acid extractant, kerosene, n-octanol, 2-ethyl-1,3-hexanediol and 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt are mixed in a volume ratio of 60:15:20:5 to obtain the boric acid extractant, and finally the boric acid product is obtained.

[0073] Example 7

[0074] The difference from Example 1 is that in the preparation of the boric acid extractant, kerosene, n-octanol, 2-ethyl-1,3-hexanediol and 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt are mixed in a volume ratio of 20:20:40:20 to obtain the boric acid extractant, and finally the boric acid product is obtained.

[0075] Example 8

[0076] The difference from Example 1 is that in the preparation of the boric acid extractant, n-dodecane, isoamyl alcohol, 2,2,4-trimethyl-1,3-pentanediol and tetraalkylphosphonium bis(trifluoromethanesulfonyl)imide salt are mixed in a volume ratio of 40:20:25:15 to obtain the boric acid extractant, and finally the boric acid product is obtained.

[0077] Example 9

[0078] The difference from Example 1 is that in the preparation of the boric acid extractant, kerosene, n-octanol, 2-ethyl-1,3-hexanediol and 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt are mixed in a volume ratio of 50:25:20:5 to obtain the boric acid extractant, and finally the boric acid product is obtained.

[0079] Example 10

[0080] The difference from Example 1 is that during the extraction process, the O / A ratio was 1:4, the extraction temperature was 30°C, and the extraction time was 30 min, ultimately yielding the boric acid product.

[0081] Example 11

[0082] The difference from Example 1 is that, during the extraction process, the O / A ratio was 1:5, the extraction temperature was 50°C, and the extraction time was 40 minutes, ultimately yielding the boric acid product.

[0083] Example 12

[0084] The difference from Example 1 is that, during the back-extraction process, the O / A ratio is 1:2, the back-extraction temperature is 30°C, and the back-extraction time is 20 min, ultimately yielding the boric acid product.

[0085] Example 13

[0086] The difference from Example 1 is that during the back-extraction process, the O / A ratio is 1:4, the back-extraction temperature is 50°C, and the back-extraction time is 30 min, ultimately yielding the boric acid product.

[0087] Comparative Example 1

[0088] The difference from Example 1 is in the preparation of the boric acid extractant: kerosene, n-octanol and 2-ethyl-1,3-hexanediol are mixed in a volume ratio of 50:25:25 to obtain the boric acid extractant, and finally the boric acid product is obtained.

[0089] Comparative Example 2

[0090] The difference from Example 1 is that the boric acid extractant is prepared by mixing kerosene, n-octanol, 2-ethyl-1,3-hexanediol and 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in a volume ratio of 20:20:20:40 to obtain the boric acid extractant, and finally obtain the boric acid product.

[0091] Comparative Example 3

[0092] The difference from Example 1 is that the ionic liquid in the boric acid extractant is replaced with 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), and the final product is boric acid extractant and boric acid product.

[0093] Test method:

[0094] Extraction rate test: The mass concentration of boron in the aqueous phase before and after extraction was determined by ICP-OES. The extraction rate was calculated using the following formula: Single-stage extraction rate = (C0 - C1) / C0 × 100%; where C0 is the mass concentration of boron in the aqueous phase before extraction, and C1 is the mass concentration of boron in the aqueous phase after single-stage extraction.

[0095] Multistage extraction rate = (C0 - C) n ) / C0×100%; where C n The mass concentration of boron in the aqueous phase after n-stage extraction.

[0096] Back-extraction rate test: The mass concentration of boron in the aqueous phase before and after back-extraction was determined by ICP-OES. The back-extraction rate was calculated using the following formula: Back-extraction rate = B1 / B0 × 100%; where B0 is the mass of boron in the boron-containing organic phase before back-extraction, and B1 is the mass of boron in the aqueous phase after back-extraction.

[0097] Total boron back-extraction rate = Sum of the mass of boron in the aqueous phase after each back-extraction stage / Total mass of boron in the boron-containing organic phase before back-extraction × 100%; For example, when using three-stage extraction, the total boron back-extraction rate = (Mass of boron in the aqueous phase after the first stage back-extraction + Mass of boron in the aqueous phase after the second stage back-extraction + Mass of boron in the aqueous phase after the third stage back-extraction) / Total mass of boron in the boron-containing organic phase before back-extraction × 100%.

[0098] Lithium loss rate calculation: The mass concentration of lithium in the aqueous phase before and after extraction was determined by ICP-OES. The lithium loss rate was calculated using the following formula: Lithium loss rate = (Li0 - Li1) / Li0 × 100%; where Li0 is the mass concentration of lithium in the aqueous phase before extraction, and Li1 is the mass concentration of lithium in the aqueous phase after extraction.

[0099] Purity test of boric acid products: The mass fraction of H3BO3 in boric acid products was determined by ICP-OES.

[0100] Ionic liquid loss detection: ICP-MS analysis was performed on the aqueous phase after extraction.

[0101] The test results are shown in Table 1.

[0102] Table 1

[0103]

[0104] As can be seen from the above, compared with the traditional mixing and clarification tank, the phase separation time of the centrifugal extraction process in Example 5 is shortened from more than 15 minutes to less than 5 seconds, the amount of organic phase entrainment is reduced by 80%, and the extraction efficiency is significantly improved. After three-stage countercurrent centrifugal extraction, the three-stage boron extraction rate reaches 99.9%, and the residual boron content in the aqueous phase is less than 5 ppm.

[0105] The extractant in Comparative Example 1 did not contain ionic liquid, its phase separation time was approximately 15 minutes, and diol loss was detected in the organic phase. Therefore, the addition of ionic liquid to the boric acid extractant of this application can significantly improve the extraction rate and phase separation speed, and reduce dissolution loss.

[0106] To verify the zero-loss characteristic of the ionic liquid, ICP-MS analysis was performed on the aqueous phase after extraction in the embodiments of this application. The results showed that no abnormal levels of fluorine and sulfur were detected in the aqueous phase, indicating that the ionic liquid did not undergo hydrolysis or dissolution during the extraction process, resulting in almost zero loss. In contrast, when diols (without ionic liquids) were used alone under the same conditions, approximately 0.15% water and trace amounts of methanol were detected in the organic phase, proving that diols are lost in the aqueous phase. Therefore, the introduction of ionic liquids effectively "anchors" diols in the organic phase, reducing organic phase loss by 30-50%.

[0107] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0108] The boric acid extractant of this application adopts a quaternary system of "monohydrin + diol + ionic liquid + diluent", which has a significant synergistic extraction effect, can improve the single-stage extraction rate, significantly reduce the solubility loss of the extractant, and is not prone to emulsification and phase separation. Specifically, the cation of the ionic liquid can act as a hydrogen bond acceptor to form a strong interaction with the boric acid ester. At the same time, the micelles formed by its long alkyl side chains in the organic phase can selectively enrich and extract the boric acid ester at the phase interface, forming a synergistic extraction effect with the monohydric alcohol and diol, thereby improving the partition coefficient and extraction selectivity, and thus significantly improving the single-stage extraction rate. Meanwhile, the strong hydrophobicity of the ionic liquid can effectively inhibit the migration of the relatively hydrophilic diol to the aqueous phase, reducing the overall water solubility of the extraction system, thereby solving the solubility loss problem of the diol, improving the phase separation performance of the diol, and preventing emulsification. This achieves efficient, low-consumption, and green extraction of boric acid, with almost zero solubility loss of the ionic liquid itself. Furthermore, monohydric alcohols are low in cost, dihydric alcohols have excellent extraction performance, and ionic liquids provide synergistic effects. The combination of these three components results in excellent extraction effects for both high and low concentrations of boron. In summary, the boric acid extractant of this application not only achieves high extraction rates and high selectivity for boron but also possesses advantages such as low solubility, minimal phase separation, recyclability, and environmental friendliness, making it suitable for large-scale industrial production and application.

[0109] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A boric acid extractant, characterized in that, The boric acid extractant comprises, by volume percentage: 20-60% diluent, 10-40% monohydric alcohol, 10-40% dihydric alcohol and 5-20% ionic liquid; The ionic liquid is selected from any one or more of imidazole ionic liquids, pyridine ionic liquids, and quaternary phosphonium ionic liquids. The cation of the ionic liquid contains an alkyl side chain. The anion of the ionic liquid is selected from any one or more of bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, hydrogen sulfate, and methanesulfonate.

2. The boric acid extractant according to claim 1, characterized in that, The ionic liquid is selected from any one or more of 1-dodecyl-3-methylimidazolium hydrogen sulfate, 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-tetradecylpyridine hydrogen sulfate, tetraalkylphosphonium hexafluorophosphate, and tetraalkylphosphonium bis(trifluoromethanesulfonyl)imide; And / or, the diluent is selected from any one or more of kerosene, sulfonated kerosene, solvent oil, n-dodecane, and heptane.

3. The boric acid extractant according to claim 1, characterized in that, The monohydric alcohol is C5~C6. 10 Branched monohydric alcohols and / or C5~C 10 A straight-chain monohydric alcohol; preferably, the monohydric alcohol is selected from any one or more of isooctyl alcohol, n-octanol, isoamyl alcohol, heptanol and 2-ethylhexanol; And / or, the diol is 1,2-diol and / or 1,3-diol; wherein, the 1,2-diol is selected from any one or more of ethylene glycol, 1,2-propanediol, and 1,2-butanediol; and the 1,3-diol is selected from any one or more of 2-ethyl-1,3-hexanediol, 2,2,6-trimethyl-1,3-heptanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2,4-trimethyl-1,3-pentanediol. And / or, the volume ratio of the monohydric alcohol to the dihydric alcohol is 1:(0.5~4), preferably 1:(1~2).

4. The boric acid extractant according to any one of claims 1 to 3, characterized in that, The volume ratio of the diluent, the monohydric alcohol, the dihydric alcohol, and the ionic liquid is 40~50:20~25:20~25:5~15.

5. A method for extracting boric acid using the boric acid extractant according to any one of claims 1 to 4, characterized in that, The method includes: Step S1: Mix the raw materials including diluent, monohydric alcohol, dihydric alcohol and ionic liquid to obtain boric acid extractant; Step S2: The brine containing boron ions is subjected to a first acid treatment to adjust the pH value of the brine to <4, thereby obtaining acid-treated brine. Step S3: The acid-treated brine is extracted using the boric acid extractant to obtain a boron-containing organic phase and an extracted solution. Step S4: The boron-containing organic phase is back-extracted using a back-extraction agent to obtain a boron-rich solution and an empty organic phase; the pH value of the back-extraction agent is ≥7; Step S5 involves sequentially evaporating and concentrating the boron-rich solution, treating it with a second acid, and cooling it to crystallize, thereby obtaining the boric acid product.

6. The method according to claim 5, characterized in that, In step S2, the mass concentration of boron ions in the brine containing boron ions is 0.0002~10 g / L, preferably 1~5 g / L.

7. The method according to claim 5, characterized in that, In step S2, the brine is subjected to the first acid treatment using a first pH adjuster; the first pH adjuster is selected from any one or more of hydrochloric acid, sulfuric acid, and nitric acid; the pH value of the brine after the acid treatment is ≤1.

8. The method according to any one of claims 5 to 7, characterized in that, In step S3, the extracted O / A ratio is 1:1 to 1:4; The extraction temperature is 20~30℃, and the extraction time is 5~30min; The extraction process has 1 to 3 stages.

9. The method according to any one of claims 5 to 7, characterized in that, In step S4, the stripping agent is water and / or an alkaline solution; wherein the alkaline solution is selected from any one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water, and sodium carbonate solution; The molar concentration of the alkaline solution is 0.05~0.1 mol / L; And / or, the O / A ratio of the back-extraction is 1:1 to 1:2; the back-extraction temperature is 20 to 30°C; and the back-extraction time is 5 to 20 minutes. And / or, the empty organic phase is regenerated to obtain a regenerated boric acid extractant.

10. The method according to any one of claims 5 to 7, characterized in that, In step S5, the boron-rich solution is evaporated and concentrated until the mass content of boron ions is ≥10g / L to obtain a concentrated solution; the concentrated solution is then subjected to a second acid treatment using a second pH adjuster to adjust the pH value to 0~2 to obtain an acid-treated solution. The acid-treated solution is subjected to cooling crystallization, filtration, washing, and drying sequentially to obtain the boric acid product; wherein the second pH adjuster is selected from any one or more of hydrochloric acid, sulfuric acid, and nitric acid. And / or, the drying temperature is 50~80℃.

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