Method for extracting boron from boron-containing brine based on polyol two aqueous phases

Abstract

The invention relates to a method for extracting boron from boron-containing brine based on polyol two aqueous phases, and the method comprises the following steps: (1) uniformly mixing a boron-containing brine solution, a polyol extraction agent and a first salting-out agent, and carrying out first pH value adjustment to obtain a mixed solution A; (2) carrying out extraction separation on the mixed solution A obtained in the step (1) to obtain a boron-loaded polyol solution and raffinate; (3) uniformly mixing the boron-loaded polyol solution obtained in the step (2), a stripping agent and a second salting-out agent, carrying out second pH value adjustment to obtain a mixed solution B, and carrying out stripping separation to obtain a boron-containing stripping solution and regenerated polyol; according to the method, no organic diluent is used in the extraction and back extraction processes, and the method is environmentally friendly, small in phase interfacial tension, high in phase splitting speed and high in extraction efficiency and has the advantages of being easy to operate, green, efficient and the like.

Description

Technical Field

[0001] This invention relates to the field of chemical separation technology, and in particular to a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction. Background Technology

[0002] Boron and its compounds are important chemical raw materials, essential components of numerous chemical products such as glass fiber, insulating materials, permanent magnets, ceramics, detergents, and flame retardants, and are widely used in defense, chemical, electronics, pharmaceutical, metallurgy, and machinery industries. my country's boron resources are mainly found in solid boron ore and boron-bearing brines. With continuous mining, the reserves of solid boron ore are gradually decreasing, and the grade is declining, no longer meeting the growing domestic industrial demand. However, the brine of salt lakes in western my country contains abundant liquid boron resources with significant development value. Therefore, extracting liquid boron resources from boron-bearing brines using appropriate processes is of great significance for meeting my country's strategic economic development needs and ensuring national energy security.

[0003] Currently, the main methods for extracting boron from boron-containing brine solutions include acidification, precipitation, adsorption, and solvent extraction. Acidification is only suitable for brine with a boron content greater than 20 g / L. After boron extraction, 6-7 g / L of boron still remains in the brine, and the recovery rate of crude boric acid after acidification is only 70-75%, which is relatively low. Adsorption offers high boron recovery and good selectivity, and can extract boron from brine to below 10 mg / L. However, this method has a significant drawback: it requires the boron content in the raw brine to be less than 500 mg / L, and the lower the mineralization of the brine, the better. It is generally used for boron extraction from seawater. Solvent extraction is suitable for brine systems with a boron content of 2-18 g / L. It has lower limitations on the boron content in the brine solution and can extract boron to below 20 mg / L, achieving a boron recovery rate of 99%. It has high boron extraction efficiency and good selectivity, and also has advantages such as simple production equipment, easy operation, and recyclable extractant, making it a relatively ideal method for boron extraction.

[0004] The core of solvent extraction lies in the selection of the extractant. Currently, commonly used boron extractants include monohydric fatty alcohols, dihydric fatty alcohols, monohydric / dihydric mixed alcohols, hydroxyl-containing aromatic compounds, and hydroxyl-containing amine compounds. Among these, fatty alcohol extractants have advantages such as high extraction efficiency, wide availability, low cost, and ease of industrialization, and are widely used in boron extraction from chloride and sulfate-type salt lakes. Monohydric alcohols can only form relatively unstable chain boronic esters with boric acid, resulting in lower boron extraction performance and often requiring multiple extraction stages to achieve ideal results. Dihydric alcohols, because they can react with boric acid to form more stable five- or six-membered ring boronic esters, have higher single-stage extraction rates than monohydric alcohols. However, dihydric alcohols suffer from high viscosity and high solubility during extraction. Studies have found that mixed alcohols composed of monohydric alcohols and / or dihydric alcohols can improve extraction efficiency and reduce extractant solubility.

[0005] Prior art CN101318675A discloses a method using a boron-containing magnesium chloride saturated solution as raw material, adding hydrochloric acid or sulfuric acid to precipitate boric acid, and then using a main chain containing C 5-10 Branched monohydric fatty alcohols were subjected to 5-10 stages of countercurrent extraction, followed by 5-8 stages of countercurrent back-extraction with water, which reduced the B2O3 content in the raw material to below 25 mg / L and achieved a boric acid recovery rate of 99%.

[0006] The prior art CN101676206A discloses a method for extracting boron from brine after lithium extraction from salt lakes using mixed alcohols consisting of 2-ethyl-1,3-hexanediol, isooctyl alcohol, and isoamyl alcohol. The optimal process conditions are achieved when the volume fraction of the extractant is 30%, the pH of the aqueous phase is 3, the phase ratio is 1:1, and the extraction time is 10 min. The extraction rate of boron is much higher than that when using a monohydric alcohol alone, and the maximum saturation capacity of B2O3 is 61.4 g / L.

[0007] Existing technology CN102757062A discloses a method using magnesium-containing brine from old salt lakes as raw material, aryl-containing 1,3-di fatty alcohols as boron extraction agents, and a mixed solution of the boron extraction agent and a diluent as the extraction organic phase. This is subjected to multi-stage countercurrent extraction with the raw material to obtain an extract phase containing boric acid. An alkaline aqueous solution is then used as a back-extraction agent, subjected to multi-stage countercurrent back-extraction with the boric acid-containing extract phase to obtain a boron-containing aqueous solution. This method can reduce the boric acid content in magnesium-containing brine to below 30 mg / L while simultaneously obtaining borax. The single-stage boric acid extraction rate reaches over 90%, and the boric acid yield reaches over 95%.

[0008] However, regardless of the alcohol used as the extractant, organic solvents were used as diluents in all the above organic extraction processes, and the dissolution of organic diluents caused serious harm to the salt lake environment. Aqueous two-phase extraction, on the other hand, does not use organic diluents during the extraction process, making it an environmentally friendly and green separation method. However, in traditional polymer aqueous two-phase extraction (such as polyethylene glycol / salt), the proportion of hydroxyl groups in the polymer molecule is small, and the interaction between the polymer terminal hydroxyl groups and boric acid is weak, resulting in a low extraction rate of boron from polymer aqueous two-phase extraction. In organic small molecule aqueous two-phase extraction (such as ethanol / salt, n-propanol / salt, isopropanol / salt, etc.), although the proportion of hydroxyl groups in the organic small molecules is significantly higher than that in the polymer molecules, the chain borate esters formed by the reaction of ethanol, n-propanol, and isopropanol with boric acid are all monohydric alcohols, and their stability is weak, resulting in a low upper limit for the single-stage extraction rate of boron.

[0009] Therefore, developing a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction process has become an urgent problem to be solved. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase system. This method utilizes a polyol-salting-out agent-boron-brine aqueous two-phase system to extract and separate boron from the boron-containing brine. The method is simple, easy to implement, operates under mild conditions, has high extraction efficiency, and requires no organic diluent.

[0011] To achieve this objective, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction, the method comprising the following steps:

[0013] (1) Mix the boron-containing brine aqueous solution, polyol extractant and first salting-out agent evenly, and adjust the pH value to obtain mixed solution A;

[0014] (2) The mixed solution A in step (1) is extracted and separated to obtain a boron-loaded polyol solution and raffinate;

[0015] (3) Mix the boron-loaded polyol solution, the back-extraction agent and the second salting-out agent described in step (2) evenly, adjust the second pH value to obtain mixed solution B, and then separate the boron-containing back-extraction solution and regenerated polyol by back-extraction.

[0016] This invention provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction. The method uses a boron-containing brine aqueous solution as the raw material and a polyol as the boron extraction extractant. The boron-containing brine aqueous solution, the polyol extractant, and a first salting-out agent are mixed evenly, and after pH adjustment, extraction and separation are performed to obtain a polyol aqueous two-phase system with a boron-loaded polyol solution as the upper phase and a brine solution as the lower phase. Then, a back-extraction agent and a second salting-out agent are mixed with the boron-loaded polyol solution to construct a polyol aqueous two-phase system for back-extraction, yielding a boron-containing back-extraction solution and regenerated polyol. This method is simple, easy to implement, operates under mild conditions, has high extraction efficiency, does not use organic diluents, and is green and efficient.

[0017] In this invention, the boron-containing back-extraction solution can be refined to obtain boric acid, and the regenerated polyol is returned to the extraction process as an extractant.

[0018] As a preferred technical solution of the present invention, the boron-containing brine solution in step (1) includes any one or a combination of at least two of the following: boron-containing salt lake raw brine, boron-containing salt lake old brine, boric acid mother liquor after acidification and boron extraction, or underground boron-containing brine.

[0019] In this invention, the boron-containing brine solution mainly comes from the boron-containing salt lake raw brine in Qinghai Province, Xinjiang Uygur Autonomous Region, Tibet Autonomous Region and Inner Mongolia Autonomous Region in western my country. The boron-containing salt lake old brine is obtained by removing potassium and sodium from the raw brine through existing processes.

[0020] Preferably, the concentration of boron in the boron-containing brine aqueous solution in step (1) is 0.5-20 g / L, for example, it can be 0.5 g / L, 1 g / L, 3 g / L, 5 g / L, 7 g / L, 10 g / L, 12 g / L, 15 g / L, 17 g / L or 20 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] In this invention, the boron concentration in the boron-containing brine aqueous solution is 0.5-20 g / L. If the boron concentration in the raw material solution is too high, it will reduce the boron extraction effect. The boron content can be reduced by acidification before being combined with extraction. The acidified brine can also improve the boron extraction effect of the extractant. If the boron concentration in the raw material solution is too low, more extractant is needed to produce the same amount of boric acid product, resulting in low economic benefits.

[0022] As a preferred technical solution of the present invention, the volume ratio of the polyol extractant to the boron-containing halide aqueous solution in step (1) is (0.25-4):1, for example, it can be 0.25:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Preferably, the polyol in the polyol extractant includes solid polyols and / or liquid polyols.

[0024] In this invention, a mixture of solid polyol and / or liquid polyol with water is used as a polyol extractant.

[0025] Preferably, the mass fraction of solid polyol in the polyol extractant is 40%-100%, for example, it can be 40%, 50%, 60%, 70%, 80%, 90% or 100%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] Preferably, the volume fraction of liquid polyol in the polyol extractant is 40%-100%, for example, it can be 40%, 50%, 60%, 70%, 80%, 90% or 100%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] In this invention, if the concentration of polyol in the polyol extractant is too low, it may be impossible to separate the phases after mixing, and even if phase separation occurs, the boron extraction effect will not be ideal.

[0028] Preferably, the solid polyol comprises neopentyl glycol.

[0029] Preferably, the liquid polyol comprises any one or a combination of at least two of 2-methyl-1,3-propanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, or 2-methyl-2,4-pentanediol, wherein typical but non-limiting combinations include: combinations of 2-methyl-1,3-propanediol and 1,3-butanediol, combinations of 2-methyl-1,3-propanediol and 3-methyl-1,3-butanediol, combinations of 2-methyl-1,3-propanediol and 2-methyl-2,4-pentanediol, combinations of 1,3-butanediol and 3-methyl-1,3-butanediol, combinations of 1,3-butanediol and 2-methyl-2,4-pentanediol, combinations of 3-methyl-1,3-butanediol and 2-methyl-2,4-pentanediol, etc.

[0030] As a preferred technical solution of the present invention, the mass fraction of the first salting-out agent in the mixed solution A in step (1) is 10%-40%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35% or 40%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the mass fraction of the second salting-out agent in the mixed solution B in step (3) is 10%-40%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35% or 40%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] As a preferred technical solution of the present invention, in step (1), the first salting-out agent includes sulfate.

[0033] Preferably, the sulfate includes any one or a combination of at least two of ammonium sulfate, sodium sulfate, lithium sulfate, or magnesium sulfate, wherein typical but non-limiting combinations include: a combination of ammonium sulfate and sodium sulfate, a combination of ammonium sulfate and lithium sulfate, a combination of ammonium sulfate and magnesium sulfate, a combination of sodium sulfate and lithium sulfate, a combination of sodium sulfate and magnesium sulfate, a combination of lithium sulfate and magnesium sulfate, etc.

[0034] Preferably, in step (3), the second salting-out agent comprises any one or a combination of at least two of ammonium sulfate, sodium sulfate, or lithium sulfate, wherein typical but non-limiting combinations include: a combination of ammonium sulfate and sodium sulfate, a combination of ammonium sulfate and lithium sulfate, and a combination of sodium sulfate and lithium sulfate.

[0035] In this invention, a first salting-out agent is used in the extraction process. Due to its strong hydration effect, the first salting-out agent competes with the polyol for association with water molecules. Since the polyol is water-soluble, the interaction between the polyol and water molecules weakens after the first salting-out agent is added to the polyol solution, resulting in the formation of a separate phase. Because the polyol can react with boric acid to form stable cyclic borate esters, boron is extracted into the polyol solution phase during the phase separation process.

[0036] In this invention, the second salting-out agent is used in the back-extraction process to remove sulfates that react with the back-extraction agents sodium hydroxide, potassium hydroxide, or ammonia. By adding the second salting-out agent, its salting-out effect causes the regenerated polyol to separate into phases, allowing boron to be back-extracted into the brine solution phase. Without the second salting-out agent, the boron-containing back-extraction solution and the regenerated polyol would mix into one phase.

[0037] As a preferred technical solution of the present invention, the endpoint of the first pH value adjustment in step (1) is a pH value of 0.5-7, for example, it can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 or 7, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] This invention adjusts the first pH value to allow more boron in the solution to exist in the form of boric acid molecules, which is beneficial for reacting with polyols to form cyclic boric acid esters, which are then extracted into the polyol solution phase during the phase separation process.

[0039] As a preferred technical solution of the present invention, the extraction and separation in step (2) is a single-stage extraction.

[0040] Preferably, the extraction and separation temperature in step (2) is 20-60℃, for example, it can be 20℃, 30℃, 40℃, 50℃ or 60℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, the mixing time in the extraction and separation in step (2) is 10-30 min, for example, it can be 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the time for standing phase separation in the extraction separation in step (2) is 5-20 min, for example, it can be 5 min, 7 min, 10 min, 12 min, 15 min, 17 min or 20 min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] As a preferred technical solution of the present invention, the stripping agent in step (3) includes an alkaline solution.

[0044] Preferably, the alkaline source in the alkaline solution includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or ammonia water, wherein typical but non-limiting combinations include: a combination of sodium hydroxide and potassium hydroxide, a combination of sodium hydroxide and ammonia water, a combination of potassium hydroxide and ammonia water, etc.

[0045] As a preferred technical solution of the present invention, the volume ratio of the boron-loaded polyol solution to the stripping agent in step (3) is 1:(0.25-4), for example, it can be 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the temperature for back-extraction separation in step (3) is 20-60°C, for example, it can be 20°C, 30°C, 40°C, 50°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the mixing time in the back-extraction separation in step (3) is 10-30 min, for example, it can be 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the time for phase separation during the back-extraction separation in step (3) is 5-20 min, for example, it can be 5 min, 7 min, 10 min, 12 min, 15 min, 17 min or 20 min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] As a preferred technical solution of the present invention, the endpoint of the second pH adjustment in step (3) is a pH value of 8-14, for example, it can be 8, 9, 10, 11, 12, 13 or 14, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] This invention uses the adjustment of a second pH value to "release" bound boric acid molecules from the polyol, thereby transferring them back into the brine aqueous solution phase to complete the back-extraction.

[0051] As a preferred technical solution of the present invention, the method specifically includes the following steps:

[0052] (1) A boron-containing brine aqueous solution with a boron concentration of 0.5-20 g / L, a polyol extractant, and a first salting-out agent are mixed evenly, and the pH value is adjusted to 0.5-7 to obtain a mixed solution A; wherein, the boron-containing brine aqueous solution includes any one or a combination of at least two of the following: boron-containing salt lake raw brine, boron-containing salt lake old brine, boric acid mother liquor after acidification and boron extraction, or underground boron-containing brine; the volume ratio of the polyol extractant to the boron-containing brine aqueous solution is (0.25-4):1, and the polyol in the polyol extractant includes solid polyol and / or liquid polyol, wherein the solid polyol in the polyol extractant... The mass fraction of the polyol extractant is 40%-100%, the volume fraction of the liquid polyol in the polyol extractant is 40%-100%, the solid polyol includes neopentyl glycol, and the liquid polyol includes any one or a combination of at least two of 2-methyl-1,3-propanediol, 1,3-butanediol, 3-methyl-1,3-butanediol or 2-methyl-2,4-pentanediol. The mass fraction of the first salting-out agent in the mixed solution A is 10%-40%, and the first salting-out agent includes a sulfate, which includes any one or a combination of at least two of ammonium sulfate, sodium sulfate, lithium sulfate or magnesium sulfate.

[0053] (2) The mixed solution A in step (1) is extracted and separated to obtain a boron-loaded polyol solution and raffinate; wherein the extraction and separation is a single-stage extraction, the extraction and separation temperature is 20-60℃, the mixing time in the extraction and separation is 10-30min, and the standing separation time in the extraction and separation is 5-20min;

[0054] (3) The boron-loaded polyol solution described in step (2) is mixed evenly with the back-extraction agent and the second salting-out agent, and the pH value is adjusted to 8-14 to obtain a mixed solution B. The boron-containing back-extraction solution and the regenerated polyol are obtained by back-extraction separation. The back-extraction agent includes an alkaline solution, and the alkaline source in the alkaline solution includes any one or at least two of sodium hydroxide, potassium hydroxide or ammonia water. The mass fraction of the second salting-out agent in the mixed solution B is 10%-40%. The volume ratio of the boron-loaded polyol solution to the back-extraction agent is 1:(0.25-4). The temperature of the back-extraction separation is 20-60℃. The mixing time in the back-extraction separation is 10-30 min. The standing separation time in the back-extraction separation is 5-20 min. The second salting-out agent includes any one or at least two of ammonium sulfate, sodium sulfate or lithium sulfate.

[0055] Compared with the prior art, the present invention has at least the following beneficial effects:

[0056] (1) The polyol aqueous two-phase extraction system provided by the present invention has low interfacial tension, fast phase separation speed, fast extraction rate, no formation of a third phase and no emulsification problem; it has a wide range of required boron concentration and pH, and the extraction efficiency of single-stage extraction is high, with boron single-stage extraction rate reaching more than 90% and boron single-stage back-extraction rate reaching more than 95%.

[0057] (2) No organic diluents are used in the extraction and back-extraction process. It is green and environmentally friendly, simple and easy to operate, and the operating conditions are mild. Detailed Implementation

[0058] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0059] Example 1

[0060] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction method, the method comprising the following steps:

[0061] (1) Mix 5 mL of boron halide aqueous solution with boron concentration of 2 g / L, 5 mL of 2-methyl-1,3-propanediol solution and 1.5 g of ammonium sulfate evenly, and adjust the pH value to 5 to obtain mixed solution A; wherein, the volume fraction of 2-methyl-1,3-propanediol in the 2-methyl-1,3-propanediol solution is 90%;

[0062] (2) The mixed solution A described in step (1) is placed in a constant temperature magnetic stirrer for single-stage extraction for 10 min. The extraction and separation temperature is 30℃. After that, the mixture is allowed to stand for 10 min to separate phases, resulting in a polyol aqueous dual phase with boron-loaded polyol solution as the upper phase and salt solution as the lower phase.

[0063] (3) The boron-loaded polyol solution described in step (2) is mixed evenly with sodium hydroxide solution and sodium sulfate, and the pH value is adjusted to 13 to obtain mixed solution B. Boron-containing back-extraction solution and regenerated polyol are obtained by back-extraction separation. The mass fraction of sodium sulfate in mixed solution B is 20%, the volume ratio of the boron-loaded polyol solution to the sodium hydroxide solution is 1:1, the temperature of back-extraction separation is 35°C, the back-extraction time is 10 min, and the standing separation time in back-extraction separation is 10 min.

[0064] Example 2

[0065] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction method, the method comprising the following steps:

[0066] (1) Mix 5 mL of boron halide aqueous solution with boron concentration of 5 g / L, 10 mL of neopentyl glycol solution and 1.8 g of ammonium sulfate evenly, and adjust the pH value to 3 to obtain mixed solution A; wherein the mass fraction of neopentyl glycol in the neopentyl glycol solution is 60%;

[0067] (2) The mixed solution A described in step (1) is placed in a constant temperature magnetic stirrer for single-stage extraction for 20 min. The extraction and separation temperature is 40℃. After that, the mixture is allowed to stand for 15 min to separate phases, resulting in a polyol aqueous dual phase with boron-loaded polyol solution as the upper phase and salt solution as the lower phase.

[0068] (3) The boron-loaded polyol solution described in step (2) is mixed evenly with sodium hydroxide solution and sodium sulfate, and the pH value is adjusted to 12 to obtain mixed solution B. Boron-containing back-extraction solution and regenerated polyol are obtained by back-extraction separation. The mass fraction of sodium sulfate in mixed solution B is 25%, the volume ratio of the boron-loaded polyol solution to the sodium hydroxide solution is 1:2, the temperature of back-extraction separation is 40℃, the back-extraction time is 20min, and the standing separation time in back-extraction separation is 15min.

[0069] Example 3

[0070] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction method, the method comprising the following steps:

[0071] (1) Mix 5 mL of boron halide aqueous solution with a boron concentration of 10 g / L, 5 mL of 1,3-butanediol solution and 1.3 g of ammonium sulfate evenly, and adjust the pH value to 4 to obtain mixed solution A; wherein, the volume fraction of 1,3-butanediol in the 1,3-butanediol solution is 60%;

[0072] (2) The mixed solution A described in step (1) is placed in a constant temperature magnetic stirrer for single-stage extraction for 10 min. The extraction and separation temperature is 50℃. After that, the mixture is allowed to stand for 10 min to separate phases, resulting in a polyol aqueous dual phase with boron-loaded polyol solution as the upper phase and salt solution as the lower phase.

[0073] (3) The boron-loaded polyol solution described in step (2) is mixed evenly with sodium hydroxide solution and sodium sulfate, and the pH value is adjusted to 13 to obtain mixed solution B. Boron-containing back-extraction solution and regenerated polyol are obtained by back-extraction separation. The mass fraction of sodium sulfate in mixed solution B is 18%, the volume ratio of the boron-loaded polyol solution to the sodium hydroxide solution is 1:2, the temperature of back-extraction separation is 50°C, the back-extraction time is 10 min, and the standing separation time in back-extraction separation is 10 min.

[0074] Example 4

[0075] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction method, the method comprising the following steps:

[0076] (1) Mix 5 mL of boron halide aqueous solution with boron concentration of 5 g / L, 5 mL of 3-methyl-1,3-butanediol solution and 1.6 g of ammonium sulfate evenly, and adjust the pH value to 3 to obtain mixed solution A; wherein, the volume fraction of 3-methyl-1,3-butanediol in the 3-methyl-1,3-butanediol solution is 60%;

[0077] (2) The mixed solution A described in step (1) is placed in a constant temperature magnetic stirrer for single-stage extraction for 10 min. The extraction and separation temperature is 35℃. After that, the mixture is allowed to stand for 10 min to separate phases, resulting in a polyol aqueous dual phase with boron-loaded polyol solution as the upper phase and salt solution as the lower phase.

[0078] (3) The boron-loaded polyol solution described in step (2) is mixed evenly with sodium hydroxide solution and sodium sulfate, and the pH value is adjusted to 12 to obtain mixed solution B. Boron-containing back-extraction solution and regenerated polyol are obtained by back-extraction separation. The mass fraction of sodium sulfate in mixed solution B is 22%, the volume ratio of the boron-loaded polyol solution to the sodium hydroxide solution is 1:1.5, the temperature of back-extraction separation is 40℃, the back-extraction time is 15min, and the standing separation time in back-extraction separation is 15min.

[0079] Example 5

[0080] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction method, the method comprising the following steps:

[0081] (1) Mix 5 mL of boron halide aqueous solution with a boron concentration of 10 g / L, 10 mL of 2-methyl-2,4-pentanediol solution and 2 g of ammonium sulfate evenly, and adjust the pH value to 2 to obtain mixed solution A; wherein, the volume fraction of 2-methyl-2,4-pentanediol in the 2-methyl-2,4-pentanediol solution is 65%;

[0082] (2) The mixed solution A described in step (1) is placed in a constant temperature magnetic stirrer for single-stage extraction for 20 min. The extraction and separation temperature is 30℃. After that, the mixture is allowed to stand for 20 min to separate phases, resulting in a polyol aqueous dual phase with boron-loaded polyol solution as the upper phase and salt solution as the lower phase.

[0083] (3) The boron-loaded polyol solution described in step (2) is mixed evenly with sodium hydroxide solution and sodium sulfate, and the pH value is adjusted to 13 to obtain mixed solution B. Boron-containing back-extraction solution and regenerated polyol are obtained by back-extraction separation. The mass fraction of sodium sulfate in mixed solution B is 20%, the volume ratio of the boron-loaded polyol solution to the sodium hydroxide solution is 1:1.5, the temperature of back-extraction separation is 30°C, the back-extraction time is 15 min, and the standing separation time in back-extraction separation is 15 min.

[0084] Example 6

[0085] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction method, the method comprising the following steps:

[0086] (1) Mix 10 mL of boron halide aqueous solution with boron concentration of 0.5 g / L, 2.5 mL of 2-methyl-1,3-propanediol solution and 1.25 g of sodium sulfate evenly, and adjust the pH value to 7 to obtain mixed solution A; wherein, the volume fraction of 2-methyl-1,3-propanediol in the 2-methyl-1,3-propanediol solution is 40%;

[0087] (2) The mixed solution A described in step (1) is placed in a constant temperature magnetic stirrer for single-stage extraction for 30 min. The extraction and separation temperature is 20℃. After that, the mixture is allowed to stand for 5 min to separate phases, resulting in a polyol aqueous dual phase with boron-loaded polyol solution as the upper phase and salt solution as the lower phase.

[0088] (3) The boron-loaded polyol solution described in step (2) is mixed evenly with ammonia solution and sodium sulfate, and the pH value is adjusted to 8 to obtain mixed solution B. Boron-containing back-extraction solution and regenerated polyol are obtained by back-extraction separation. The mass fraction of sodium sulfate in mixed solution B is 20%, the volume ratio of the boron-loaded polyol solution to the ammonia solution is 1:3, the temperature of back-extraction separation is 20°C, the back-extraction time is 10 min, and the standing separation time in back-extraction separation is 5 min.

[0089] Example 7

[0090] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction method, the method comprising the following steps:

[0091] (1) Mix 5 mL of boron halide aqueous solution with a boron concentration of 20 g / L, 20 mL of 2-methyl-1,3-propanediol solution and 10 g of ammonium sulfate evenly, and adjust the pH value to 0.5 to obtain mixed solution A; wherein, the volume fraction of 2-methyl-1,3-propanediol in the 2-methyl-1,3-propanediol solution is 50%;

[0092] (2) The mixed solution A described in step (1) is placed in a constant temperature magnetic stirrer for single-stage extraction for 30 min. The extraction and separation temperature is 60℃. After that, the mixture is allowed to stand for 20 min to separate phases, resulting in a polyol aqueous dual phase with boron-loaded polyol solution as the upper phase and salt solution as the lower phase.

[0093] (3) The boron-loaded polyol solution described in step (2) is mixed evenly with sodium hydroxide solution and sodium sulfate, and the pH value is adjusted to 14 to obtain mixed solution B. Boron-containing back-extraction solution and regenerated polyol are obtained by back-extraction separation. The mass fraction of sodium sulfate in mixed solution B is 40%, the volume ratio of the boron-loaded polyol solution to the sodium hydroxide solution is 1:4, the temperature of back-extraction separation is 60℃, the back-extraction time is 30min, and the standing separation time in back-extraction separation is 20min.

[0094] Example 8

[0095] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction. The difference from Embodiment 1 is that the mass fraction of ammonium sulfate in step (1) is adjusted to 5%.

[0096] Example 9

[0097] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction. The difference from Example 1 is that step (1) adjusts the pH of the mixed solution A to 8, while the rest is the same as in Example 1.

[0098] Example 10

[0099] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction. The difference from Example 1 is that step (3) adjusts the pH of the mixed solution B to 6, while the rest is the same as in Example 1.

[0100] Example 11

[0101] This embodiment provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction. The difference from Example 1 is that the volume fraction of 2-methyl-1,3-propanediol in the 2-methyl-1,3-propanediol solution in step (1) is 25%, while the rest are the same as in Example 1.

[0102] Comparative Example 1

[0103] This comparative example provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction, which differs from Example 1 in that the addition of the first salting-out agent in step (1) is omitted.

[0104] Comparative Example 2

[0105] This comparative example provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction, which differs from Example 1 in that the addition of the second salting-out agent in step (3) is omitted.

[0106] Comparative Example 3

[0107] This comparative example provides a method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction. The difference from Example 1 is that the 2-methyl-1,3-propanediol solution of the polyol extractant in step (1) is replaced with the n-propanol solution of the monohydric alcohol extractant. All other aspects are the same as in Example 1.

[0108] Test method: The concentration of boron in the solutions of Examples 1-11 and Comparative Examples 1-3 was detected using an inductively coupled plasma atomic emission spectrometer (ICP-OES) (preferably with a wavelength of 249.677 nm). The boron extraction rate and back-extraction rate were calculated according to the following formulas: Boron extraction rate (%) = Amount of boron in the boron-loaded polyol solution / Amount of boron in the boron-containing brine solution × 100%; Boron back-extraction rate (%) = Amount of boron in the boron-containing back-extraction solution / Amount of boron in the boron-loaded polyol solution × 100%.

[0109] The test results are shown in Table 1.

[0110] Table 1

[0111]

[0112] The test results show that:

[0113] (1) As can be seen from Examples 1 to 7, the method for extracting boron from boron-containing brine based on polyol aqueous two-phase extraction provided by the present invention can achieve efficient extraction of boron from boron-containing brine, with a single-stage extraction rate of boron of over 90% and a single-stage back-extraction rate of boron of over 95%.

[0114] (2) As can be seen from Examples 1 and 8, the present invention can achieve better phase separation effect by further limiting the mass fraction of the first salting-out agent. When the concentration of the first salting-out agent is too low, a two-phase aqueous solution cannot be formed, and only a mixed and clear single-phase solution can be obtained. Therefore, the mass fraction of the first salting-out agent needs to be controlled within a certain range to ensure that a two-phase aqueous solution can be formed.

[0115] (3) It can be seen from the combined examples 1 and 9 that when the pH value of the mixed solution A is adjusted to 8, the solution becomes alkaline and the extraction rate of boron decreases significantly.

[0116] (4) It can be seen from the combined examples 1 and 10 that when the pH value of the mixed solution B is adjusted to 6, the solution is acidic and the back-extraction rate of boron decreases significantly.

[0117] (5) As can be seen from the combined examples 1 and 11, when the concentration of the polyol extractant is too low, a two-phase aqueous solution cannot be formed. Therefore, the concentration of the polyol extractant needs to be limited.

[0118] (6) As can be seen from the combined examples 1 and 2, without the addition of the first and second salting-out agents, phase separation is impossible during extraction and back-extraction. Therefore, the present invention, through the addition of the first salting-out agent, utilizes its strong hydration effect to compete with the polyol for association with water molecules. Since the polyol is soluble in water, the interaction between the polyol and water molecules weakens after the first salting-out agent is added to the polyol solution, resulting in a separate phase. Because the polyol can react with boric acid to form stable cyclic borate esters, boron is extracted into the polyol solution phase during phase separation. The present invention, through the addition of the second salting-out agent, utilizes its salting-out effect to separate the regenerated polyol phase and back-extract boron into the brine solution phase. Without the second salting-out agent, the boron-containing back-extraction solution and the regenerated polyol would be mixed into one phase.

[0119] (7) As can be seen from the combined examples 1 and 3, if the polyol extractant of the present invention is replaced with a monohydric alcohol extractant, since the monohydric alcohol molecule contains only one hydroxyl group, it can only form a chain borate ester with boric acid, and the extraction performance of boron is low.

[0120] In summary, this invention utilizes a polyol-salting-out agent-boron-containing brine aqueous two-phase system to extract and separate boron from boron-containing brine. This method is simple, easy to implement, operates under mild conditions, has high extraction efficiency, and requires no organic diluent.

[0121] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for extracting boron from boron-containing brine based on a polyol aqueous two-phase extraction process, characterized in that, The method includes the following steps: (1) Mix the boron-containing brine aqueous solution, polyol extractant and first salting-out agent evenly, and adjust the pH value to obtain mixed solution A; (2) The mixed solution A in step (1) is extracted and separated to obtain a boron-loaded polyol solution and raffinate; (3) Mix the boron-loaded polyol solution, the back-extraction agent and the second salting-out agent described in step (2) evenly, adjust the second pH value to obtain mixed solution B, and then separate the boron-containing back-extraction solution and regenerated polyol by back-extraction.

2. The method according to claim 1, characterized in that, The boron-containing brine solution in step (1) includes any one or a combination of at least two of the following: boron-containing salt lake raw brine, boron-containing salt lake old brine, boric acid mother liquor after boron extraction by acidification, or underground boron-containing brine; Preferably, the concentration of boron in the boron-containing brine aqueous solution in step (1) is 0.5-20 g / L.

3. The method according to claim 1 or 2, characterized in that, In step (1), the volume ratio of the polyol extractant to the boron-containing halide aqueous solution is (0.25-4):1; Preferably, the polyol in the polyol extractant includes solid polyols and / or liquid polyols; Preferably, the mass fraction of solid polyol in the polyol extractant is 40%-100%; Preferably, the volume fraction of the liquid polyol in the polyol extractant is 40%-100%; Preferably, the solid polyol comprises neopentyl glycol; Preferably, the liquid polyol includes any one or a combination of at least two of 2-methyl-1,3-propanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, or 2-methyl-2,4-pentanediol.

4. The method according to any one of claims 1-3, characterized in that, In step (1), the mass fraction of the first salting-out agent in the mixed solution A is 10%-40%; Preferably, the mass fraction of the second salting-out agent in the mixed solution B in step (3) is 10%-40%.

5. The method according to any one of claims 1-4, characterized in that, Step (1) The first salting-out agent comprises sulfate; Preferably, the sulfate includes any one or a combination of at least two of ammonium sulfate, sodium sulfate, lithium sulfate, or magnesium sulfate; Preferably, in step (3), the second salting-out agent comprises any one or a combination of at least two of ammonium sulfate, sodium sulfate, or lithium sulfate.

6. The method according to any one of claims 1-5, characterized in that, Step (1) The endpoint of the first pH adjustment is a pH value of 0.5-7.

7. The method according to any one of claims 1-6, characterized in that, The extraction and separation described in step (2) is a single-stage extraction; Preferably, the extraction and separation temperature in step (2) is 20-60℃; Preferably, the mixing time in the extraction and separation process in step (2) is 10-30 min; Preferably, the time for phase separation during the extraction and separation in step (2) is 5-20 min.

8. The method according to any one of claims 1-7, characterized in that, The stripping agent in step (3) includes an alkaline solution; Preferably, the alkaline source in the alkaline solution includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or ammonia water; Preferably, the volume ratio of the boron-loaded polyol solution to the stripping agent in step (3) is 1:(0.25-4); Preferably, the temperature for back-extraction separation in step (3) is 20-60℃; Preferably, the mixing time in the back-extraction separation in step (3) is 10-30 min; Preferably, the time for phase separation during the back-extraction separation in step (3) is 5-20 min.

9. The method according to any one of claims 1-8, characterized in that, Step (3) The endpoint of the second pH adjustment is a pH value of 8-14.

10. The method according to any one of claims 1-9, characterized in that, The method specifically includes the following steps: (1) A boron-containing brine aqueous solution with a boron concentration of 0.5-20 g / L, a polyol extractant, and a first salting-out agent are mixed evenly, and the pH value is adjusted to 0.5-7 to obtain a mixed solution A; wherein, the boron-containing brine aqueous solution includes any one or a combination of at least two of the following: boron-containing salt lake raw brine, boron-containing salt lake old brine, boric acid mother liquor after acidification and boron extraction, or underground boron-containing brine; the volume ratio of the polyol extractant to the boron-containing brine aqueous solution is (0.25-4):1, and the polyol in the polyol extractant includes solid polyol and / or liquid polyol, wherein the solid polyol in the polyol extractant... The mass fraction of the polyol extractant is 40%-100%, the volume fraction of the liquid polyol in the polyol extractant is 40%-100%, the solid polyol includes neopentyl glycol, and the liquid polyol includes any one or a combination of at least two of 2-methyl-1,3-propanediol, 1,3-butanediol, 3-methyl-1,3-butanediol or 2-methyl-2,4-pentanediol. The mass fraction of the first salting-out agent in the mixed solution A is 10%-40%, and the first salting-out agent includes a sulfate, which includes any one or a combination of at least two of ammonium sulfate, sodium sulfate, lithium sulfate or magnesium sulfate. (2) The mixed solution A in step (1) is extracted and separated to obtain a boron-loaded polyol solution and raffinate; wherein the extraction and separation is a single-stage extraction, the extraction and separation temperature is 20-60℃, the mixing time in the extraction and separation is 10-30min, and the standing separation time in the extraction and separation is 5-20min; (3) The boron-loaded polyol solution described in step (2) is mixed evenly with the back-extraction agent and the second salting-out agent, and the pH value is adjusted to 8-14 to obtain a mixed solution B. The boron-containing back-extraction solution and the regenerated polyol are obtained by back-extraction separation. The back-extraction agent includes an alkaline solution, and the alkaline source in the alkaline solution includes any one or at least two of sodium hydroxide, potassium hydroxide or ammonia water. The mass fraction of the second salting-out agent in the mixed solution B is 10%-40%. The volume ratio of the boron-loaded polyol solution to the back-extraction agent is 1:(0.25-4). The temperature of the back-extraction separation is 20-60℃. The mixing time in the back-extraction separation is 10-30 min. The standing separation time in the back-extraction separation is 5-20 min. The second salting-out agent includes any one or at least two of ammonium sulfate, sodium sulfate or lithium sulfate.

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