A method for directly preparing lithium carbonate from lithium in oilfield brine

Abstract

The application provides a method for directly preparing lithium carbonate from oilfield brine, which comprises the following steps: mixing the pretreated oilfield brine with a first saponified organic phase to perform a first extraction to obtain a lithium chloride solution; mixing the lithium chloride solution with a second saponified organic phase to perform a second extraction, washing and back extraction, and then performing ion liquid membrane electrodialysis; and finally mixing the ion liquid membrane electrodialysis product with sodium carbonate to perform a reaction to obtain lithium carbonate. The method provided by the application firstly adopts the method of precipitation and extraction to treat the oilfield brine, thereby ensuring the efficiency of the subsequent lithium extraction process and realizing the regeneration of the extraction phase; the method adopts the solvent extraction-ion liquid membrane electrodialysis coupling technology to realize the direct preparation of battery-grade lithium carbonate from the oilfield brine, thereby realizing the deep separation of lithium from high-concentration sodium, potassium, calcium and magnesium in the brine; in addition, compared with the traditional lithium extraction process, the method avoids the problem of long growth cycle caused by the natural evaporation process.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology, and relates to a method for extracting lithium from brine, and more particularly to a method for directly preparing lithium carbonate from oilfield brine. Background Technology

[0002] Lithium plays a crucial role in the development of new energy and low-carbon economies, and is widely used in lithium-ion batteries, specialty glasses, ceramics, and lubricants. It is hailed as the "energy metal" of the 21st century and the "element that drives the world forward," with approximately 71% of lithium used in the manufacture of lithium-ion batteries. Therefore, the comprehensive utilization of lithium resources is essential for the development of new energy. Lithium is mainly found in brine, spodumene, and mica deposits, with brine accounting for about 89.9% of total lithium reserves. However, due to limitations in lithium extraction technology, most lithium currently still comes from lithium ore, and the development and utilization of brine resources are severely insufficient.

[0003] Solvent extraction, as a highly efficient technique for extracting and enriching low-concentration elements in brine, is widely used in lithium extraction. CN113981243A discloses a method for extracting and separating lithium and alkaline earth metals from brine with a high sodium-to-lithium ratio. The method includes: using brine with a high sodium-to-lithium ratio as the aqueous phase, and using a diketone extractant and a halogenated organophosphorus co-extractant as the organic phase, performing at least one stage of countercurrent extraction, followed by sequential sodium back-extraction, lithium back-extraction, calcium back-extraction, and magnesium back-extraction, thereby separating sodium salt solution, lithium salt solution, calcium salt solution, and magnesium salt solution. This technology effectively separates sodium, lithium, and alkaline earth metals such as calcium and magnesium from brine with a high sodium-to-lithium ratio, avoiding the use of co-extractant FeCl3 and problems such as small density difference between the two phases and difficulty in process control during extraction. However, the regeneration of the extractant requires a high-acid environment, and Mg... 2+ Ca 2+ Divalent metal ions preferentially enter the organic phase during lithium extraction and return to the aqueous phase during washing, leading to solvent loss and waste, and reducing extraction efficiency. This is detrimental to industrial production.

[0004] Electrodialysis technology utilizes the interception effect of ion-selective membranes on competitive ions to achieve the separation and enrichment of lithium under the action of an electric field. CN108341421A discloses a method for directly extracting lithium carbonate from brine in a high magnesium-to-lithium ratio salt lake. This method involves treating boron-lithium brine to extract boron, followed by three refining processes. Part of the three-stage refined liquid is passed through a bipolar membrane electrodialysis unit to form a lithium-alkali solution, while the remaining three-stage refined liquid is passed through a forced evaporator to form a concentrated lithium solution. The concentrated lithium solution and refined sodium carbonate solution are then passed through a high-efficiency reactor to form a lithium carbonate precipitate with uniform particle size, ultimately producing a battery-grade lithium carbonate product. This invention has good operability and significantly improves the lithium-ion recovery rate. However, this technology requires pretreatment through natural evaporation concentration, resulting in a long production cycle and high process costs.

[0005] In recent years, oil and gas field brine resources have attracted considerable attention. Oil and gas field brines are natural water systems in groundwater that possess unique physical and chemical properties due to the proximity of oil and gas. Compared to salt lake brines, oil and gas field brines have the advantages of high lithium content and a low magnesium-to-lithium ratio, making lithium extraction relatively easier. However, oil and gas field brines also face challenges such as high mineralization, high calcium content, and high organic matter content.

[0006] CN116287780A discloses a method for extracting lithium from brine in oil and gas fields. This method involves pretreating the brine, followed by extraction, elution, and back-extraction to obtain a concentrated lithium solution, thus completing the lithium extraction process. While this method achieves good lithium extraction and back-extraction effects, it fails to achieve deep separation from sodium and potassium. Further preparation of lithium carbonate products would affect product quality.

[0007] Coupled solvent extraction with electrodialysis technology will provide a new approach for oilfield brine extraction. Summary of the Invention

[0008] The purpose of this invention is to provide a method for directly preparing lithium carbonate from oilfield brine by coupling solvent extraction with electrodialysis technology to achieve deep separation of lithium from sodium, potassium, calcium and magnesium in oilfield brine and prepare high-quality lithium carbonate products.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for directly preparing lithium carbonate from oilfield brine, the method comprising the following steps:

[0011] (1) Pre-treat the oilfield brine to obtain pre-treated brine;

[0012] (2) The pretreated brine obtained in step (1) is mixed with the first saponified organic phase for a first extraction. The first saponified organic phase is obtained by first saponification of the first organic phase using a first saponifying agent. The first organic phase includes a first extractant and a first solvent to obtain a lithium chloride solution.

[0013] (3) The lithium chloride solution obtained in step (2) is mixed with the second saponified organic phase for a second extraction. The second saponified organic phase is obtained by using a second saponifying agent to perform a second saponification on the second organic phase. The second organic phase includes a second extractant, a co-extractant, and a second solvent to obtain an extractable organic phase. The extractable organic phase is washed and back-extracted to obtain a first-refined lithium chloride solution.

[0014] (4) The primary refined lithium chloride solution obtained in step (3) is subjected to ion liquid membrane electrodialysis to obtain secondary refined lithium concentrate.

[0015] (5) The secondary refined lithium concentrate obtained in step (4) is mixed with sodium carbonate and reacted to obtain lithium carbonate.

[0016] The method provided by this invention first treats oilfield brine using precipitation and extraction. Precipitation removes a large amount of calcium ions from the brine, and the first extraction removes the remaining magnesium and calcium ions, ensuring the efficiency of subsequent lithium extraction processes and the quality of the regenerated organic phase, while also reducing the difficulty of extractant regeneration. Next, extraction and electrodialysis are coupled. In the second extraction process, lithium is initially separated from sodium and potassium. Then, electrodialysis further separates and concentrates lithium, achieving deep separation of lithium from sodium, potassium, calcium, and magnesium in the oilfield brine and directly preparing high-quality lithium carbonate. This realizes a continuous lithium extraction and concentration process. Furthermore, compared to traditional lithium extraction processes, it avoids the growth cycle problems caused by natural evaporation.

[0017] Preferably, in the oilfield brine of step (1), the lithium ion concentration is ≥70mg / L, the magnesium ion concentration is ≥2g / L, the calcium ion concentration is ≥6g / L, the potassium ion concentration is ≥7g / L, and the sodium ion concentration is ≥40g / L.

[0018] Preferably, the pretreatment in step (1) includes: filtering the oilfield brine, mixing it with a precipitant, and then aging and separating it to obtain pretreated brine.

[0019] Preferably, the precipitant comprises sodium sulfate.

[0020] Preferably, in step (2), the first extractant comprises any one or at least two of P204, P507, C272 or P227. Typical but non-limiting combinations include the combination of P204 and P507, the combination of P507 and C272, the combination of C272 and P227, the combination of P204, P507 and C272, the combination of P507, C272 and P227, or the combination of P204, P507, C272 and P227.

[0021] Preferably, in step (2), the concentration of the first extractant in the first organic phase is 0.5-1.5 mol / L, for example, it can be 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, in step (2), the first solvent includes any one or a combination of at least two of sulfonated kerosene, cyclohexane, or n-octanol. Typical but non-limiting combinations include a combination of sulfonated kerosene and cyclohexane, a combination of cyclohexane and n-octanol, a combination of sulfonated kerosene and n-octanol, or a combination of sulfonated kerosene, cyclohexane, and n-octanol.

[0023] Preferably, in step (2), the first saponifying agent includes any one or a combination of at least two of ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, or potassium hydroxide. Typical but non-limiting combinations include a combination of ammonia and sodium hydroxide, a combination of sodium carbonate and sodium bicarbonate, a combination of sodium acetate and potassium hydroxide, a combination of ammonia, sodium hydroxide, and sodium carbonate, or a combination of sodium bicarbonate, sodium acetate, and potassium hydroxide, preferably ammonia.

[0024] Preferably, the volume concentration of the ammonia water is 15-25%, for example, it can be 15%, 16%, 18%, 20%, 22%, 24% or 25%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, in step (2), the molar ratio of the first saponifying agent to the first extractant is (1-10):10, for example, it can be 1:10, 2:10, 4:10, 5:10, 6:10, 8:10 or 10:10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the temperature of the first saponification in step (2) is 25-50°C, for example, it can be 25°C, 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the saponification time in step (2) is 10-30 min, for example, it can be 10 min, 12 min, 14 min, 15 min, 16 min, 18 min, 20 min, 22 min, 25 min, 28 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, in step (2), the volume ratio of the first saponified organic phase to the pretreated brine is (1-30):(1-30), for example, it can be 1:1, 10:1, 20:1, 30:1, 1:10, 1:20 or 1:30, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the temperature of the first extraction in step (2) is 20-50°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the extraction time in step (2) is 6-30 min, for example, it can be 6 min, 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the first extraction method in step (2) includes countercurrent extraction and / or cross-current extraction.

[0032] Preferably, in step (2), the first extraction stage is 2-5 stages, for example, it can be 2 stages, 3 stages, 4 stages or 5 stages.

[0033] Preferably, in step (3), the second extractant comprises a diketone extractant.

[0034] Preferably, the second extractant in step (3) includes any one or a combination of at least two of HTTA (bis(trifluoroacetylacetone)), HDBM (2-benzoylmethane), LIX54 (1-phenyldecyl-1,3-dione), HBTA (benzoyltrifluoroacetone) or HPMBP (1-phenyl-3-methyl-4-benzoyl-5-pyrazolone). Typical but non-limiting combinations include combinations of HTTA and HDBM, combinations of LIX54 and HBTA, combinations of HTTA, HDBM and LIX54, combinations of LIX54, HBTA and HPMBP, or combinations of HTTA, HDBM, LIX54, HBTA and HPMBP.

[0035] Preferably, in step (3), the concentration of the second extractant in the second organic phase is 1-1.5 mol / L, for example, it can be 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, in step (3), the second solvent includes any one or a combination of at least two of sulfonated kerosene, cyclohexane, or n-octanol. Typical but non-limiting combinations include a combination of sulfonated kerosene and cyclohexane, a combination of cyclohexane and n-octanol, a combination of sulfonated kerosene and n-octanol, or a combination of sulfonated kerosene, cyclohexane, and n-octanol.

[0037] Preferably, the co-extractant in step (3) includes any one or a combination of at least two of TBP (tributyl phosphate), TOPO (trioctylphosphine oxide) or C923 (trialkylphosphine oxide). Typical but non-limiting combinations include combinations of TBP and TOPO, combinations of TBP and C923, combinations of TOPO and C923, or combinations of TBP, TOPO and C923.

[0038] Preferably, the second saponifying agent in step (3) includes any one or a combination of at least two of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, potassium hydroxide, or ammonia. Typical but non-limiting combinations include a combination of sodium hydroxide and sodium carbonate, a combination of sodium bicarbonate and sodium acetate, a combination of potassium hydroxide and ammonia, a combination of sodium hydroxide, sodium carbonate, and sodium bicarbonate, or a combination of sodium acetate, potassium hydroxide, and ammonia, preferably sodium hydroxide.

[0039] Preferably, the concentration of sodium hydroxide is 1-5 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, in step (3), the molar ratio of the second saponifying agent to the second extractant is (1-10):10, for example, it can be 1:10, 2:10, 4:10, 5:10, 6:10, 8:10 or 10:10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the temperature of the second saponification in step (3) is 20-60°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Preferably, the second saponification time in step (3) is 1-20 min, for example, it can be 1 min, 2 min, 4 min, 5 min, 6 min, 8 min, 10 min, 12 min, 15 min, 18 min or 20 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, in step (3), the volume ratio of the second saponified organic phase to the lithium chloride solution is (1-30):(1-30), for example, it can be 1:1, 10:1, 20:1, 30:1, 1:10, 1:20 or 1:30, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the temperature of the second extraction in step (3) is 25-50°C, for example, it can be 25°C, 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] Preferably, the extraction time in step (3) is 1-20 min, for example, it can be 1 min, 5 min, 10 min, 15 min or 20 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] Preferably, the method of the second extraction in step (3) includes countercurrent extraction and / or cross-current extraction.

[0047] Preferably, in step (3), the second extraction stage is 1-5 stages, for example, it can be stage 1, stage 2, stage 3, stage 4 or stage 5.

[0048] Preferably, the detergent used in step (3) includes water.

[0049] Preferably, the volume ratio of the detergent to the extracted organic phase is (1-20):(1-5), for example, it can be 1:1, 10:1, 20:1, 1:3 or 1:5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] Preferably, the washing temperature in step (3) is 5-10℃, for example, it can be 5℃, 6℃, 7℃, 8℃, 9℃ or 10℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Preferably, the washing method in step (3) includes countercurrent washing and / or crosscurrent washing.

[0052] Preferably, the washing process in step (3) has 2-5 stages, for example, it can be 2 stages, 3 stages, 4 stages or 5 stages.

[0053] Preferably, the stripping agent in step (3) includes any one or a combination of at least two of hydrochloric acid, sulfuric acid, nitric acid, CO2 or citric acid. Typical but non-limiting combinations include a combination of hydrochloric acid and sulfuric acid, a combination of nitric acid and CO2, a combination of hydrochloric acid, sulfuric acid and nitric acid, or a combination of nitric acid, CO2 and citric acid.

[0054] Preferably, the volume ratio of the back-extraction agent to the washed organic phase is (1-5):(1-30), for example, it can be 1:1, 1:10, 1:20, 1:30, 3:1 or 5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] Preferably, the temperature of the back-extraction in step (3) is 30-50°C, for example, it can be 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] Preferably, the back-extraction time in step (3) is 8-30 min, for example, it can be 8 min, 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] Preferably, the back-extraction method in step (3) includes countercurrent back-extraction and / or crosscurrent back-extraction.

[0058] Preferably, the number of stages of back-extraction in step (3) is 3-10, for example, it can be 3, 4, 5, 6, 7, 8, 9 or 10 stages.

[0059] Preferably, the ionic liquid membrane electrodialysis in step (4) is performed using an ionic liquid membrane electrodialysis device, which includes an anode plate, a first anion exchange membrane, an ionic liquid membrane, a second anion exchange membrane, and a cathode plate arranged in sequence. The anode plate and the first anion exchange membrane form an anode chamber, the first anion exchange membrane and the ionic liquid membrane form a feed chamber, the ionic liquid membrane and the second anion exchange membrane form a concentration chamber, and the second anion exchange membrane and the cathode plate form a cathode chamber.

[0060] Preferably, the ionic liquid membrane electrodialysis process in step (4) includes: injecting electrode liquid into the anode and cathode chambers, injecting a primary purified lithium chloride solution into the feed chamber, and under the action of an electric field, the Li in the feed chamber... + The lithium concentrate, obtained by passing through the ionic liquid membrane into the concentration chamber, is a secondary refined lithium concentrate. Anions in the feed chamber pass through the first anion exchange membrane into the anode chamber, where they react with H+ generated by water electrolysis in the anode chamber. +The pH is adjusted using an alkaline solution in the feed chamber and an acidic solution in the concentration chamber.

[0061] Preferably, the ionic liquid membrane includes any one or a combination of at least two of the [A336][TTA] type ionic liquid membrane, [N4441][BTA] type ionic liquid membrane, or [Omim][PMBP] type ionic liquid membrane. Typical but non-limiting combinations include the combination of [A336][TTA] type ionic liquid membrane and [N4441][BTA] type ionic liquid membrane, the combination of [N4441][BTA] type ionic liquid membrane and [Omim][PMBP] type ionic liquid membrane, the combination of [A336][TTA] type ionic liquid membrane and [Omim][PMBP] type ionic liquid membrane, or the combination of [A336][TTA] type ionic liquid membrane, [N4441][BTA] type ionic liquid membrane, and [Omim][PMBP] type ionic liquid membrane.

[0062] Preferably, the thickness of the ionic liquid film is 100-300 μm, for example, it can be 100 μm, 150 μm, 200 μm, 250 μm or 300 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0063] Preferably, the electrode solution comprises any one or a combination of at least two of hydrochloric acid solution, nitric acid solution, sulfuric acid solution or carbonic acid solution. Typical but non-limiting combinations include a combination of hydrochloric acid solution and nitric acid solution, a combination of sulfuric acid solution and carbonic acid solution, a combination of hydrochloric acid solution, nitric acid solution and sulfuric acid solution, a combination of nitric acid solution, sulfuric acid solution and carbonic acid solution, or a combination of hydrochloric acid solution, nitric acid solution, sulfuric acid solution and carbonic acid solution.

[0064] Preferably, the concentration of the electrode solution is 0.1-2 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] Preferably, the alkaline solution comprises any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or ammonia. Typical but non-limiting combinations include a combination of sodium hydroxide and potassium hydroxide, a combination of potassium hydroxide and ammonia, a combination of sodium hydroxide and ammonia, or a combination of sodium hydroxide, potassium hydroxide, and ammonia.

[0066] Preferably, the concentration of the alkaline solution is 0.2-3 mol / L, for example, it can be 0.2 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] Preferably, the acid solution includes any one or a combination of at least two of hydrochloric acid solution, nitric acid solution, sulfuric acid solution, carbonic acid solution or sodium carbonate solution. Typical but non-limiting combinations include a combination of hydrochloric acid solution and nitric acid solution, a combination of sulfuric acid solution and carbonic acid solution, a combination of hydrochloric acid solution, nitric acid solution and sulfuric acid solution, a combination of nitric acid solution, sulfuric acid solution and carbonic acid solution, or a combination of hydrochloric acid solution, nitric acid solution, sulfuric acid solution and carbonic acid solution.

[0068] Preferably, the concentration of the acid solution is 0.1-1 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L or 1 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] The method provided by this invention first treats oilfield brine using precipitation and extraction, ensuring the efficiency of subsequent lithium extraction processes and enabling the regeneration of the extracted phase. It employs a solvent extraction-electrodialysis coupling technology to directly prepare battery-grade lithium carbonate from oilfield brine, achieving deep separation of lithium from the high concentrations of sodium, potassium, calcium, and magnesium in the brine. Furthermore, compared with traditional lithium extraction processes, it avoids the problem of long growth cycles caused by natural evaporation processes. Attached Figure Description

[0071] Figure 1 This is a process flow diagram of the method provided in Example 1.

[0072] Figure 2 This is a schematic diagram of the ion liquid membrane electrodialysis apparatus according to the method provided in Example 1;

[0073] Wherein, 1 is the anode plate; 2 is the first anion exchange membrane; 3 is the ionic liquid membrane; 4 is the second anion exchange membrane; and 5 is the cathode plate. Detailed Implementation

[0074] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0075] To clearly illustrate the technical solution of the present invention, the oilfield brine used in the specific embodiment originates from the Nanyishan structural zone oilfield, wherein the concentration of lithium ions is 0.20 g / L, the concentration of magnesium ions is 2.15 g / L, the concentration of potassium ions is 7.98 g / L, the concentration of calcium ions is 22.34 g / L, and the concentration of sodium ions is 94.34 g / L.

[0076] Example 1

[0077] This embodiment provides a method such as Figure 1 The method shown is for the direct preparation of lithium carbonate from oilfield brine, and the method includes the following steps:

[0078] (1) The oilfield brine is filtered through a plate and frame filter to remove a small amount of mud and sand, and a lithium-containing brine with stable composition is obtained. The lithium-containing brine and 1 mol / L sodium sulfate solution are fed into a high-efficiency reactor at a volume ratio of 1:1. The mixture is fully reacted in the high-efficiency reactor for 2 hours. After aging for 12 hours, the mixture is fed into a plate and frame filter for phase separation to obtain pretreated brine.

[0079] (2) The pretreated brine was mixed with the first saponified organic phase at a volume ratio of 1:1 and subjected to three-stage countercurrent extraction at 40°C for 10 min to obtain a lithium chloride solution.

[0080] The first saponified organic phase is obtained by saponifying the first organic phase with 20% ammonia water at a volume ratio of 5:1. The saponification process is carried out at a temperature of 25°C for 20 minutes. The components of the first organic phase include the first extractant C272 and the first solvent sulfonated kerosene. In the first organic phase, the concentration of C272 is 1 mol / L, and the molar ratio of C272 to ammonia water is 1:0.5.

[0081] The extracted first saponified organic phase was mixed with 0.1 mol / L hydrochloric acid solution at a volume ratio of 1:1 and subjected to two-stage countercurrent washing at 40°C to obtain the regenerated first organic phase.

[0082] (3) The lithium chloride solution and the second saponified organic phase were mixed at a volume ratio of 1:2 and subjected to two-stage countercurrent extraction at 30°C for 15 min. The extracted second saponified organic phase was then mixed with deionized water at a volume ratio of 1:1 and separated to wash away residual sodium and potassium. Then, it was mixed with 0.2 mol / L hydrochloric acid solution at a volume ratio of 20:1 and subjected to three-stage countercurrent back-extraction at 40°C in a mixing and clarifying tank for 8 min to obtain a first-stage purified lithium chloride solution.

[0083] The second saponified organic phase is obtained by saponifying the second organic phase with a 5 mol / L sodium hydroxide solution at a volume ratio of 20:1. The saponification process is carried out at a temperature of 30°C for 10 min. The components of the second organic phase include the second extractant LIX54, the co-extractant TRPO, and the second solvent cyclohexane. The concentration of LIX54 in the second organic phase is 1.3 mol / L, and the molar ratio of LIX54 to sodium hydroxide is 1:0.7.

[0084] The second saponified organic phase after back-extraction was mixed with 0.1 mol / L hydrochloric acid solution at a volume ratio of 1:1 and subjected to two-stage countercurrent washing at 40 °C to obtain the regenerated second organic phase.

[0085] (4) Electrodialysis of the primary purified lithium chloride solution was performed using an ionic liquid membrane electrodialysis apparatus, such as... Figure 2 As shown, the ion liquid membrane electrodialysis unit includes an anode plate 1, a first anion exchange membrane 2, an ion liquid membrane 3, a second anion exchange membrane 4, and a cathode plate 5 arranged in sequence. The anode plate and the first anion exchange membrane form an anode chamber, the first anion exchange membrane and the ion liquid membrane form a feed chamber, the ion liquid membrane and the second anion exchange membrane form a concentration chamber, and the second anion exchange membrane and the cathode plate form a cathode chamber. The ion liquid membrane is a [A336][TTA] type ion liquid membrane with a thickness of 200 μm.

[0086] The electrodialysis process is as follows: electrode solution (0.5 mol / L hydrochloric acid solution) is injected into the anode and cathode chambers; a primary purified lithium chloride solution is injected into the feed chamber; and the electrodialysis is performed at 5 mA / cm². 2 Electrodialysis was performed at a current density of [insert current density here]. The pH of the feed chamber was maintained at 10 using 1.0 mol / L sodium hydroxide, and the pH of the anode, cathode, and concentration chambers was adjusted to 1 using 0.2 mol / L sulfuric acid solution. The Li [insert concentration here] in the feed chamber was [insert concentration here]. + The lithium concentrate, obtained by passing through the ionic liquid membrane into the concentration chamber, is a secondary refined lithium concentrate. Anions in the feed chamber pass through the first anion exchange membrane into the anode chamber, where they react with H+ generated by water electrolysis in the anode chamber. + pair;

[0087] (5) Pass the secondary refined lithium concentrate and 1 mol / L sodium carbonate solution into a high-efficiency reactor. After reacting fully in the high-efficiency reactor for 4 hours, a lithium carbonate precipitate with uniform particle size is formed. Pass the mixture into a plate and frame filter press to filter the lithium carbonate precipitate. After washing and drying, battery-grade lithium carbonate product is obtained.

[0088] Example 2

[0089] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine, the method comprising the following steps:

[0090] (1) The oilfield brine was filtered through a plate and frame filter to remove a small amount of mud and sand, and a stable lithium brine was obtained. The lithium brine and 1.5 mol / L sodium sulfate solution were fed into a high-efficiency reactor at a volume ratio of 1:0.7. The reaction was carried out in the high-efficiency reactor for 2 hours. The resulting mixture was aged for 24 hours and then passed into a plate and frame filter for phase separation to obtain pretreated brine.

[0091] (2) The pretreated brine was mixed with the first saponified organic phase at a volume ratio of 1.5:1 and subjected to five-stage countercurrent extraction at 35°C for 6 min to obtain a lithium chloride solution.

[0092] The first saponified organic phase is obtained by saponifying the first organic phase with 5 mol / L sodium hydroxide at a volume ratio of 10:1. The saponification process is carried out at a temperature of 30°C for 10 min. The components of the first organic phase include the first extractant P507 and the first solvent n-octanol. In the first organic phase, the concentration of P507 is 1.2 mol / L, and the molar ratio of P507 to sodium hydroxide is 1:0.4.

[0093] The extracted first saponified organic phase was mixed with 0.3 mol / L hydrochloric acid solution at a volume ratio of 2:1 and subjected to three-stage countercurrent washing at 35°C to obtain the regenerated first organic phase.

[0094] (3) The lithium chloride solution and the second saponified organic phase were mixed at a volume ratio of 1:3 and subjected to three-stage countercurrent extraction at 40°C for 15 min. The extracted second saponified organic phase was mixed with deionized water at a volume ratio of 1:1.5 and the phases were separated to wash away the residual sodium and potassium. Then it was mixed with 0.5 mol / L hydrochloric acid solution at a volume ratio of 40:1 and subjected to three-stage countercurrent back-extraction at 40°C in a mixing and clarifying tank for 15 min to obtain a first-stage purified lithium chloride solution.

[0095] The second saponified organic phase is obtained by saponifying the second organic phase with a 7 mol / L sodium hydroxide solution at a volume ratio of 30:1. The saponification process is carried out at a temperature of 40℃ for 20 min. The components of the second organic phase include the second extractant HTTA, the co-extractant TBP, and the second solvent cyclohexane. In the second organic phase, the concentration of HTTA is 1.5 mol / L, and the molar ratio of HTTA to sodium hydroxide is 1:0.8.

[0096] The second saponified organic phase after back-extraction was mixed with 0.3 mol / L hydrochloric acid solution at a volume ratio of 5:1 and subjected to three-stage countercurrent washing at 30°C to obtain the regenerated second organic phase.

[0097] (4) Electrodialysis of a primary purified lithium chloride solution is performed using an ionic liquid membrane electrodialysis apparatus. The ionic liquid membrane electrodialysis apparatus includes an anode plate, a first anion exchange membrane, an ionic liquid membrane, a second anion exchange membrane, and a cathode plate arranged in sequence. The anode plate and the first anion exchange membrane form an anode chamber, the first anion exchange membrane and the ionic liquid membrane form a feed chamber, the ionic liquid membrane and the second anion exchange membrane form a concentration chamber, and the second anion exchange membrane and the cathode plate form a cathode chamber. The ionic liquid membrane is a [N4441][BTA] type ionic liquid membrane with a thickness of 300 μm.

[0098] The electrodialysis process is as follows: electrode solutions (0.3 mol / L hydrochloric acid solution) are injected into the anode and cathode chambers. A primary purified lithium chloride solution is then injected into the feed chamber at a current of 3 mA / cm². 2 Electrodialysis was performed at a current density of [insert current density here]. The pH of the feed chamber was maintained at 10.5 using 0.5 mol / L sodium hydroxide solution, and the pH of the anode, cathode, and concentration chambers was adjusted to 1 using 0.5 mol / L sulfuric acid solution. The Li [insert concentration here] in the feed chamber was [insert concentration here]. + The lithium concentrate, obtained by passing through the ionic liquid membrane into the concentration chamber, is a secondary refined lithium concentrate. Anions in the feed chamber pass through the first anion exchange membrane into the anode chamber, where they react with H+ generated by water electrolysis in the anode chamber. + pair;

[0099] (5) Pass the secondary refined lithium concentrate and 2 mol / L sodium carbonate solution into a high-efficiency reactor. After reacting fully in the high-efficiency reactor for 4 hours, a lithium carbonate precipitate with uniform particle size is formed. Pass the mixture into a plate and frame filter press to filter the lithium carbonate precipitate. After washing and drying, battery-grade lithium carbonate product is obtained.

[0100] Example 3

[0101] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine, the method comprising the following steps:

[0102] (1) The oilfield brine is filtered through a plate and frame filter to remove a small amount of mud and sand, and a lithium-containing brine with stable composition is obtained. The lithium-containing brine and 2 mol / L sodium sulfate solution are fed into a high-efficiency reactor at a volume ratio of 1:0.5. The mixture is fully reacted in the high-efficiency reactor for 2 hours. After aging for 24 hours, the mixture is fed into a plate and frame filter for phase separation to obtain pretreated brine.

[0103] (2) The pretreated brine was mixed with the first saponified organic phase at a volume ratio of 2:1 and subjected to three-stage countercurrent extraction at 30°C for 9 min to obtain a lithium chloride solution.

[0104] The first saponified organic phase is obtained by saponifying the first organic phase with 25% ammonia water at a volume ratio of 8:1. The saponification process is carried out at a temperature of 25°C for 30 minutes. The components of the first organic phase include the first extractant P204 and the first solvent n-octanol. In the first organic phase, the concentration of P204 is 1.5 mol / L, and the molar ratio of P204 to ammonia water is 1:0.7.

[0105] The extracted first saponified organic phase was mixed with 0.3 mol / L hydrochloric acid solution at a volume ratio of 2:1 and subjected to three-stage countercurrent washing at 35°C to obtain the regenerated first organic phase.

[0106] (3) The lithium chloride solution and the second saponified organic phase were mixed at a volume ratio of 1:2 and subjected to 5-stage countercurrent extraction at 25°C for 20 min. The extracted second saponified organic phase was mixed with deionized water at a volume ratio of 1:3 and the phases were separated to wash away the residual sodium and potassium. Then it was mixed with 0.2 mol / L hydrochloric acid solution at a volume ratio of 30:1 and subjected to 5-stage countercurrent back-extraction at 40°C in a mixing and clarifying tank for 10 min to obtain a first-stage purified lithium chloride solution.

[0107] The second saponified organic phase is obtained by saponifying the second organic phase with a 5 mol / L sodium hydroxide solution at a volume ratio of 40:1. The saponification process is carried out at a temperature of 40℃ for 20 min. The components of the second organic phase include the second extractant HDBM, the co-extractant TOPO, and the second solvent cyclohexane. In the second organic phase, the concentration of HDBM is 1.3 mol / L, and the molar ratio of HDBM to sodium hydroxide is 1:0.7.

[0108] The second saponified organic phase after back-extraction was mixed with 0.3 mol / L hydrochloric acid solution at a volume ratio of 3:1 and subjected to 5 stages of countercurrent washing at 30°C to obtain the regenerated second organic phase.

[0109] (4) Electrodialysis of a primary purified lithium chloride solution is performed using an ionic liquid membrane electrodialysis apparatus. The ionic liquid membrane electrodialysis apparatus includes an anode plate, a first anion exchange membrane, an ionic liquid membrane, a second anion exchange membrane, and a cathode plate arranged in sequence. The anode plate and the first anion exchange membrane form an anode chamber, the first anion exchange membrane and the ionic liquid membrane form a feed chamber, the ionic liquid membrane and the second anion exchange membrane form a concentration chamber, and the second anion exchange membrane and the cathode plate form a cathode chamber. The ionic liquid membrane is a [Omim][PMBP] type ionic liquid membrane with a thickness of 200 μm.

[0110] The electrodialysis process is as follows: electrode solution (0.5 mol / L hydrochloric acid solution) is injected into the anode and cathode chambers; a primary purified lithium chloride solution is injected into the feed chamber; and the electrodialysis is performed at 2 mA / cm².2 Electrodialysis was performed at a current density of [insert current density here]. The pH of the feed chamber was maintained at 10.5 using 0.2 mol / L sodium hydroxide solution, and the pH of the anode, cathode, and concentration chambers was adjusted to 1 using 0.2 mol / L sulfuric acid solution. The Li [insert concentration here] in the feed chamber was [insert concentration here]. + The lithium concentrate, obtained by passing through the ionic liquid membrane into the concentration chamber, is a secondary refined lithium concentrate. Anions in the feed chamber pass through the first anion exchange membrane into the anode chamber, where they react with H+ generated by water electrolysis in the anode chamber. + pair;

[0111] (5) Pass the secondary refined lithium concentrate and 1 mol / L sodium carbonate solution into a high-efficiency reactor. After reacting fully in the high-efficiency reactor for 4 hours, a lithium carbonate precipitate with uniform particle size is formed. Pass the mixture into a plate and frame filter press to filter the lithium carbonate precipitate. After washing and drying, battery-grade lithium carbonate product is obtained.

[0112] Example 4

[0113] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine, the method comprising the following steps:

[0114] (1) The oilfield brine is filtered through a plate and frame filter to remove a small amount of mud and sand, and a lithium-containing brine with stable composition is obtained. The lithium-containing brine and 1 mol / L sodium sulfate solution are fed into a high-efficiency reactor at a volume ratio of 1:1. The mixture is fully reacted in the high-efficiency reactor for 2 hours. After aging for 12 hours, the mixture is fed into a plate and frame filter for phase separation to obtain pretreated brine.

[0115] (2) The pretreated brine was mixed with the first saponified organic phase at a volume ratio of 1:30 and subjected to two-stage countercurrent extraction at 20°C for 30 min to obtain a lithium chloride solution.

[0116] The first saponified organic phase is obtained by saponifying the first organic phase with 20% ammonia water. The saponification process is carried out at a temperature of 25°C for 20 minutes. The components of the first organic phase include the first extractant C272 and the first solvent sulfonated kerosene. In the first organic phase, the concentration of C272 is 0.5 mol / L, and the molar ratio of C272 to ammonia water is 10:1.

[0117] The extracted first saponified organic phase was mixed with 0.1 mol / L hydrochloric acid solution at a volume ratio of 1:1 and subjected to two-stage countercurrent washing at 40°C to obtain the regenerated first organic phase.

[0118] (3) The lithium chloride solution was mixed with the second saponified organic phase at a volume ratio of 1:30 and subjected to two-stage countercurrent extraction at 25°C for 5 min. The extracted second saponified organic phase was then mixed with deionized water at a volume ratio of 5:1 and separated to wash away residual sodium and potassium. Then, it was mixed with 0.2 mol / L hydrochloric acid solution at a volume ratio of 30:1 and subjected to three-stage countercurrent back-extraction at 30°C in a mixing and clarifying tank for 30 min to obtain a first-stage purified lithium chloride solution.

[0119] The second saponified organic phase is obtained by saponifying the second organic phase with a 5 mol / L sodium hydroxide solution. The saponification process is carried out at a temperature of 20°C for 20 min. The components of the second organic phase include the second extractant LIX54, the co-extractant TRPO, and the second solvent cyclohexane. The concentration of LIX54 in the second organic phase is 1 mol / L, and the molar ratio of LIX54 to sodium hydroxide is 10:1.

[0120] The second saponified organic phase after back-extraction was mixed with 0.1 mol / L hydrochloric acid solution at a volume ratio of 1:1 and subjected to two-stage countercurrent washing at 40 °C to obtain the regenerated second organic phase.

[0121] (4) Electrodialysis of a primary purified lithium chloride solution is performed using an ionic liquid membrane electrodialysis apparatus. The ionic liquid membrane electrodialysis apparatus includes an anode plate, a first anion exchange membrane, an ionic liquid membrane, a second anion exchange membrane, and a cathode plate arranged in sequence. The anode plate and the first anion exchange membrane form an anode chamber, the first anion exchange membrane and the ionic liquid membrane form a feed chamber, the ionic liquid membrane and the second anion exchange membrane form a concentration chamber, and the second anion exchange membrane and the cathode plate form a cathode chamber. The ionic liquid membrane is a [A336][TTA] type ionic liquid membrane with a thickness of 100 μm.

[0122] The electrodialysis process is as follows: electrode solution (0.1 mol / L hydrochloric acid solution) is injected into the anode and cathode chambers. A primary purified lithium chloride solution is then injected into the feed chamber at a current of 5 mA / cm². 2 Electrodialysis was performed at a current density of [insert current density here]. The pH of the feed chamber was maintained at 10 using 0.5 mol / L sodium hydroxide solution, and the pH of the anode, cathode, and concentration chambers was adjusted to 1 using 0.1 mol / L sulfuric acid solution. The Li [insert concentration here] in the feed chamber was [insert concentration here]. + The lithium concentrate, obtained by passing through the ionic liquid membrane into the concentration chamber, is a secondary refined lithium concentrate. Anions in the feed chamber pass through the first anion exchange membrane into the anode chamber, where they react with H+ generated by water electrolysis in the anode chamber. + pair;

[0123] (5) Pass the secondary refined lithium concentrate and 1 mol / L sodium carbonate solution into a high-efficiency reactor. After reacting fully in the high-efficiency reactor for 4 hours, a lithium carbonate precipitate with uniform particle size is formed. Pass the mixture into a plate and frame filter press to filter the lithium carbonate precipitate. After washing and drying, battery-grade lithium carbonate product is obtained.

[0124] Example 5

[0125] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine, the method comprising the following steps:

[0126] (1) The oilfield brine is filtered through a plate and frame filter to remove a small amount of mud and sand, and a lithium-containing brine with stable composition is obtained. The lithium-containing brine and 1 mol / L sodium sulfate solution are fed into a high-efficiency reactor at a volume ratio of 1:1. The mixture is fully reacted in the high-efficiency reactor for 2 hours. After aging for 12 hours, the mixture is fed into a plate and frame filter for phase separation to obtain pretreated brine.

[0127] (2) The pretreated brine was mixed with the first saponified organic phase at a volume ratio of 30:1 and subjected to five-stage countercurrent extraction at 50°C for 10 min to obtain a lithium chloride solution.

[0128] The first saponified organic phase is obtained by saponifying the first organic phase with 20% ammonia water. The saponification process is carried out at a temperature of 50°C for 10 minutes. The components of the first organic phase include the first extractant C272 and the first solvent sulfonated kerosene. In the first organic phase, the concentration of C272 is 1 mol / L, and the molar ratio of C272 to ammonia water is 10:10.

[0129] The extracted first saponified organic phase was mixed with 0.1 mol / L hydrochloric acid solution at a volume ratio of 1:1 and subjected to two-stage countercurrent washing at 40°C to obtain the regenerated first organic phase.

[0130] (3) The lithium chloride solution and the second saponified organic phase were mixed at a volume ratio of 30:1 and subjected to a first-stage countercurrent extraction at 50°C for 1 min. The extracted second saponified organic phase was then mixed with deionized water at a volume ratio of 1:20 and the phases were separated to wash away the residual sodium and potassium. Then, it was mixed with 0.2 mol / L hydrochloric acid solution at a volume ratio of 1:5 and subjected to a 10-stage countercurrent back-extraction at 50°C in a mixing and clarifying tank for 10 min to obtain a first-stage purified lithium chloride solution.

[0131] The second saponified organic phase is obtained by saponifying the second organic phase with a 5 mol / L sodium hydroxide solution. The saponification process is carried out at a temperature of 60°C for 1 min. The components of the second organic phase include the second extractant LIX54, the co-extractant TRPO, and the second solvent cyclohexane. The concentration of LIX54 in the second organic phase is 1.5 mol / L, and the molar ratio of LIX54 to sodium hydroxide is 10:10.

[0132] The second saponified organic phase after back-extraction was mixed with 0.1 mol / L hydrochloric acid solution at a volume ratio of 1:1 and subjected to two-stage countercurrent washing at 40 °C to obtain the regenerated second organic phase.

[0133] (4) Electrodialysis of a primary purified lithium chloride solution is performed using an ionic liquid membrane electrodialysis apparatus. The ionic liquid membrane electrodialysis apparatus includes an anode plate, a first anion exchange membrane, an ionic liquid membrane, a second anion exchange membrane, and a cathode plate arranged in sequence. The anode plate and the first anion exchange membrane form an anode chamber, the first anion exchange membrane and the ionic liquid membrane form a feed chamber, the ionic liquid membrane and the second anion exchange membrane form a concentration chamber, and the second anion exchange membrane and the cathode plate form a cathode chamber. The ionic liquid membrane is a [A336][TTA] type ionic liquid membrane with a thickness of 300 μm.

[0134] The electrodialysis process is as follows: electrode solution (2 mol / L hydrochloric acid solution) is injected into the anode and cathode chambers; a primary purified lithium chloride solution is injected into the feed chamber; and the electrodialysis is performed at 5 mA / cm². 2 Electrodialysis was performed at a current density of [insert current density here]. The pH of the feed chamber was maintained at 10 using 3 mol / L sodium hydroxide, and the pH of the anode, cathode, and concentration chambers was adjusted to 1 using 1 mol / L sulfuric acid solution. The Li [insert concentration here] in the feed chamber was [insert concentration here]. + The lithium concentrate, obtained by passing through the ionic liquid membrane into the concentration chamber, is a secondary refined lithium concentrate. Anions in the feed chamber pass through the first anion exchange membrane into the anode chamber, where they react with H+ generated by water electrolysis in the anode chamber. + pair;

[0135] (5) Pass the secondary refined lithium concentrate and 1 mol / L sodium carbonate solution into a high-efficiency reactor. After reacting fully in the high-efficiency reactor for 4 hours, a lithium carbonate precipitate with uniform particle size is formed. Pass the mixture into a plate and frame filter press to filter the lithium carbonate precipitate. After washing and drying, battery-grade lithium carbonate product is obtained.

[0136] Example 6

[0137] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine. Compared with Example 1, the second extractant in step (3) is replaced with HPMBP in equal amounts, and the rest is the same as in Example 1.

[0138] Example 7

[0139] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine. Compared with Example 1, the second extractant in step (3) is replaced by an equal amount of 1-(4-chlorophenyl)-4,4,4-trifluoro-1,3-butanedione, and the rest is the same as in Example 1.

[0140] Example 8

[0141] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine. Compared with Example 1, in step (3), the concentration of the second extractant is controlled to be 0.5 mol / L, and the rest are the same as in Example 1.

[0142] Example 9

[0143] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine. Compared with Example 1, in step (3), the concentration of the second extractant is controlled to be 2 mol / L, and the rest are the same as in Example 1.

[0144] Example 10

[0145] This embodiment provides a method for directly preparing lithium carbonate from oilfield brine. Compared with Example 1, the co-extractant in step (3) is replaced with dibutyl phosphate in equal amounts, and the rest is the same as in Example 1.

[0146] Comparative Example 1

[0147] This comparative example provides a method for directly preparing lithium carbonate from oilfield brine. Compared with Example 1, step (2) is omitted, and the rest is the same as in Example 1.

[0148] Comparative Example 2

[0149] This comparative example provides a method for directly preparing lithium carbonate from oilfield brine. Compared with Example 1, step (4) is omitted, and the rest is the same as in Example 1.

[0150] Comparative Example 3

[0151] This comparative example provides a method for directly preparing lithium carbonate from oilfield brine. Compared with Example 1, step (3) is omitted, and the rest is the same as in Example 1.

[0152] Performance testing

[0153] The lithium extraction rate, lithium back-extraction rate, calcium removal rate, magnesium removal rate, potassium removal rate, sodium removal rate, and organic phase regeneration acidity were determined in the examples and comparative examples. The metal ion content was determined by ICP-OES method. The results are listed in Table 1.

[0154] Table 1

[0155]

[0156]

[0157] In the table, " / " indicates no data.

[0158] As can be seen from Table 1, the method provided by the present invention can effectively extract lithium from oilfield brine, deeply separate sodium, potassium, calcium and magnesium, prepare high-quality lithium carbonate products, and ensure the regeneration of the extraction phase.

[0159] In summary, the method provided by this invention first treats oilfield brine using precipitation and extraction, ensuring the efficiency of subsequent lithium extraction processes and enabling the regeneration of the extracted phase. It employs a solvent extraction-electrodialysis coupling technology to directly prepare battery-grade lithium carbonate from oilfield brine, achieving deep separation of lithium from the high concentrations of sodium, potassium, calcium, and magnesium in the brine. Furthermore, compared to traditional lithium extraction processes, it avoids the long growth cycle problem caused by natural evaporation.

[0160] 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 directly preparing lithium carbonate from oilfield brine, characterized in that, The method includes the following steps: (1) Pre-treat the oilfield brine to obtain pre-treated brine; (2) The pretreated brine obtained in step (1) is mixed with the first saponified organic phase for the first extraction. The first saponified organic phase is obtained by first saponification of the first organic phase using the first saponifying agent. The first organic phase includes the first extractant and the first solvent to obtain a lithium chloride solution. The first extractant includes any one or a combination of at least two of P204, P507, C272 or P227; (3) The lithium chloride solution obtained in step (2) is mixed with the second saponified organic phase for a second extraction. The second saponified organic phase is obtained by using a second saponifying agent to perform a second saponification on the second organic phase. The second organic phase includes a second extractant, a co-extractant, and a second solvent to obtain an extractable organic phase. The extractable organic phase is washed and back-extracted to obtain a first-refined lithium chloride solution. The second extractant includes any one or a combination of at least two of HTTA, HDBM, LIX54, HBTA, or HPMBP; (4) The primary purified lithium chloride solution obtained in step (3) is subjected to ion liquid membrane electrodialysis to obtain secondary purified lithium concentrate; Step (4) The ionic liquid membrane electrodialysis is performed using an ionic liquid membrane electrodialysis device, which includes an anode plate, a first anion exchange membrane, an ionic liquid membrane, a second anion exchange membrane, and a cathode plate arranged in sequence. The anode plate and the first anion exchange membrane form an anode chamber, the first anion exchange membrane and the ionic liquid membrane form a feed chamber, the ionic liquid membrane and the second anion exchange membrane form a concentration chamber, and the second anion exchange membrane and the cathode plate form a cathode chamber. Step (4) of the ionic liquid membrane electrodialysis process includes: injecting electrode liquid into the anode and cathode chambers, injecting a primary purified lithium chloride solution into the feed chamber, and under the action of an electric field, the Li in the feed chamber... + The lithium concentrate, obtained by passing through the ionic liquid membrane into the concentration chamber, is a secondary refined lithium concentrate. Anions in the feed chamber pass through the first anion exchange membrane into the anode chamber, where they react with H+ generated by water electrolysis in the anode chamber. + The pH value is adjusted by using an alkaline solution in the feed chamber and an acidic solution in the concentration chamber. The ionic liquid membrane includes any one or a combination of at least two of the [A336][TTA] type ionic liquid membrane, [N4441][BTA] type ionic liquid membrane, or [Omim][PMBP] type ionic liquid membrane; (5) The secondary refined lithium concentrate obtained in step (4) is mixed with sodium carbonate and reacted to obtain lithium carbonate.

2. The method according to claim 1, characterized in that, In step (1), the concentration of lithium ions in the oilfield brine is ≥70 mg / L, the concentration of magnesium ions is ≥2 g / L, the concentration of calcium ions is ≥6 g / L, the concentration of potassium ions is ≥7 g / L, and the concentration of sodium ions is ≥40 g / L.

3. The method according to claim 1, characterized in that, The pretreatment in step (1) includes: filtering the oilfield brine, mixing it with a precipitant, and then aging and separating it to obtain pretreated brine.

4. The method according to claim 3, characterized in that, The precipitant includes sodium sulfate.

5. The method according to claim 1, characterized in that, In step (2), the concentration of the first extractant in the first organic phase is 0.5-1.5 mol / L.

6. The method according to claim 1, characterized in that, Step (2) The first solvent includes any one or a combination of at least two of sulfonated kerosene, cyclohexane or n-octanol.

7. The method according to claim 1, characterized in that, Step (2) The first saponifying agent includes any one or a combination of at least two of ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate or potassium hydroxide.

8. The method according to claim 1, characterized in that, Step (2) The molar ratio of the first saponifying agent to the first extractant is (1-10):

10.

9. The method according to claim 1, characterized in that, Step (2) The temperature of the first saponification is 25-50℃.

10. The method according to claim 1, characterized in that, Step (2) The first saponification time is 10-30 min.

11. The method according to claim 1, characterized in that, Step (2) The volume ratio of the first saponified organic phase to the pretreated brine is (1-30):(1-30).

12. The method according to claim 1, characterized in that, Step (2) The temperature of the first extraction is 20-50℃.

13. The method according to claim 1, characterized in that, Step (2) The first extraction time is 6-30 min.

14. The method according to claim 1, characterized in that, Step (2) The first extraction method includes countercurrent extraction and / or cross-current extraction.

15. The method according to claim 1, characterized in that, Step (2) The first extraction stage is 2-5 stages.

16. The method according to claim 1, characterized in that, In step (3), the concentration of the second extractant in the second organic phase is 1-1.5 mol / L.

17. The method according to claim 1, characterized in that, Step (3) The second solvent includes any one or a combination of at least two of sulfonated kerosene, cyclohexane or n-octanol.

18. The method according to claim 1, characterized in that, The co-extractant in step (3) includes any one or a combination of at least two of TBP, TOPO or C923.

19. The method according to claim 1, characterized in that, Step (3) The second saponifying agent includes any one or a combination of at least two of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate, potassium hydroxide or ammonia.

20. The method according to claim 1, characterized in that, In step (3), the molar ratio of the second saponifying agent to the second extractant is (1-10):

10.

21. The method according to claim 1, characterized in that, In step (3), the temperature for the second saponification is 20-60℃.

22. The method according to claim 1, characterized in that, Step (3) The second saponification time is 1-20 min.

23. The method according to claim 1, characterized in that, In step (3), the volume ratio of the second saponified organic phase to the lithium chloride solution is (1-30):(1-30).

24. The method according to claim 1, characterized in that, In step (3), the temperature of the second extraction is 25-50℃.

25. The method according to claim 1, characterized in that, Step (3) The second extraction time is 1-20 min.

26. The method according to claim 1, characterized in that, Step (3) The second extraction method includes countercurrent extraction and / or cross-current extraction.

27. The method according to claim 1, characterized in that, Step (3) The second extraction stage is 1-5 stages.

28. The method according to claim 1, characterized in that, The detergent used in step (3) includes water.

29. The method according to claim 1, characterized in that, The volume ratio of the detergent to the extracted organic phase is (1-20):(1-5).

30. The method according to claim 1, characterized in that, The washing temperature in step (3) is 5-10℃.

31. The method according to claim 1, characterized in that, The washing method described in step (3) includes countercurrent washing and / or crosscurrent washing.

32. The method according to claim 1, characterized in that, The washing process in step (3) is of grade 2-5.

33. The method according to claim 1, characterized in that, The stripping agent in step (3) includes any one or a combination of at least two of hydrochloric acid, sulfuric acid, nitric acid, CO2 or citric acid.

34. The method according to claim 1, characterized in that, The volume ratio of the back-extraction agent to the washed organic phase is (1-5):(1-30).

35. The method according to claim 1, characterized in that, The temperature for back-extraction in step (3) is 30-50℃.

36. The method according to claim 1, characterized in that, The back-extraction time in step (3) is 8-30 min.

37. The method according to claim 1, characterized in that, The back-extraction method in step (3) includes countercurrent back-extraction and / or cross-current back-extraction.

38. The method according to claim 1, characterized in that, The number of stages of back-extraction in step (3) is 3-10.

39. The method according to claim 1, characterized in that, The thickness of the ionic liquid film is 100-300 μm.

40. The method according to claim 1, characterized in that, The electrode solution includes any one or a combination of at least two of the following: hydrochloric acid solution, nitric acid solution, sulfuric acid solution, or carbonic acid solution.

41. The method according to claim 1, characterized in that, The concentration of the electrode solution is 0.1-2 mol / L.

42. The method according to claim 1, characterized in that, The alkaline solution includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or ammonia.

43. The method according to claim 1, characterized in that, The concentration of the alkaline solution is 0.2-3 mol / L.

44. The method according to claim 1, characterized in that, The acid solution includes any one or a combination of at least two of the following: hydrochloric acid solution, nitric acid solution, sulfuric acid solution, or carbonic acid solution.

45. The method according to claim 1, characterized in that, The concentration of the acid solution is 0.1-1 mol / L.

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