Combined lithium extraction process

Abstract

The invention relates to a combined lithium extraction process which comprises the following steps: extracting an alkaline lithium-containing solution containing carbonate by adopting a first extraction solution, then carrying out reverse extraction on an obtained first loaded oil phase, preparing lithium carbonate from a first reverse extraction solution, and simultaneously extracting a first raffinate by adopting a second extraction solution, then, the obtained second loaded oil phase is subjected to reverse extraction, and lithium carbonate is prepared from second reverse extraction liquid; wherein a main extraction agent used in the first extraction liquid is selected from beta-diketone without a halogenated functional group and / or an amino functional group, a main extraction agent used in the second extraction liquid is selected from beta-diketone containing a halogenated functional group and / or an amino functional group, and an acid with the acidity higher than that of carbonic acid is used when the second load oil phase is subjected to reverse extraction. According to the combined lithium extraction process, efficient extraction can be achieved on the basis that the alkaline lithium-containing solution containing carbonate does not need to be pretreated, the solution loss rate of the extraction agent is low, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction, and particularly to a combined lithium extraction process. Background Art

[0002] Solvent extraction method has gradually become one of the core methods for lithium extraction due to its advantages such as high selectivity and easy scale-up. However, for alkaline lithium-containing solutions containing carbonate such as carbonate-type salt lake brine and mother liquor of lithium precipitation, the current mainstream extraction methods still have the following deficiencies: (1) In order to improve the extraction rate, it is necessary to pretreat the alkaline lithium-containing solution containing carbonate. For example, adding strong acid to remove carbonate, then adding liquid alkali to adjust the pH to neutral or alkaline, or adding oxides or hydroxides of calcium, barium, strontium, lanthanum, cerium to remove carbonate, or directly adding a large amount of liquid alkali to increase the hydroxide content. These pretreatment methods will greatly increase the production cost; (2) The dissolution loss rate of the extractant is relatively high under alkaline extraction conditions, and the stronger the alkalinity, the higher the dissolution loss rate, resulting in the inability of the production process to operate stably for a long time. Summary of the Invention

[0003] Based on this, in view of the above problems, it is necessary to provide a combined lithium extraction process that does not require pretreatment of the alkaline lithium-containing solution containing carbonate, has a high extraction rate, a low dissolution loss rate of the extractant, and a low production cost.

[0004] A combined lithium extraction process includes the following steps:

[0005] Using a first extractant to extract an alkaline lithium-containing solution containing carbonate to obtain a first loaded oil phase and a first raffinate. Among them, the main extractant used in the first extractant is selected from β-diketones without halogenated functional groups and / or amino functional groups;

[0006] Back-extracting the first loaded oil phase to obtain a first back-extract solution, and then preparing lithium carbonate from the first back-extract solution;

[0007] Using a second extractant to extract the first raffinate to obtain a second loaded oil phase, then back-extracting the second loaded oil phase to obtain a second back-extract solution, and then preparing lithium carbonate from the second back-extract solution. Among them, the main extractant used in the second extractant is selected from β-diketones containing halogenated functional groups and / or amino functional groups, and an acid stronger than carbonic acid is used for back-extracting the second loaded oil phase.

[0008] In one embodiment, the main extractant used in the first extractant is selected from at least one of heptanoyl benzoyl methane, hexanoyl benzoyl methane, dibenzoyl methane, palmitoyl benzoyl methane, dihexanoyl methane, dioctanoyl methane, 1-phenyl-1,3-butanedione, 1-benzoyl-2-nonanone, dibenzoyl methane, stearoyl benzoyl methane;

[0009] And / or, the main extractant used in the second extractant is selected from at least one of 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, 1,1,1,2,2-pentafluoro-6,6-dimethyl-3,5-heptanedione, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione, benzoyltrifluoroacetone, benzoyltrichloroacetone, benzoyl-tribromoacetone, 5-fluoroindoline-2,3-dione, 5-fluoropyrimidine-2,4(1H,3H)-dione, 4,4,4-trifluoro-1-(4-tolyl)-1,3-butanedione, 1,3-dimethylpyrimidine-2,4(1H,3H)-dione, indole-2,3-dione, 5,5-dimethylimidazolidine-2,4-dione.

[0010] In one embodiment, a synergistic extractant is further included in both the first extractant and the second extractant. The volume ratio of the main extractant to the synergistic extractant is independently selected from 1:2 - 2:1, and the synergistic extractant is independently selected from at least one of trialkyl phosphate, trialkyl phosphine oxide, trioctyl phosphine oxide, trihexyl phosphine oxide, dialkyl phosphate, methyl isobutyl ketone, 1-phenylazo-2-naphthol, n-octanol, isooctanol, 2-ethylhexanol, 14-crown-4 ether dibutyl butylphosphonate, dibutyl butylphosphate, methylene tetrabutyl bisphosphonate, trioctylamine oxide, 1,10-phenanthroline, quaternary ammonium salt N 263 , dimethyldi(N-octadecyl)ammonium chloride, methyl dioctyl sulfonium chloride, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0011] In one embodiment, in the step of extracting the lithium-containing alkaline solution containing carbonate with the first extractant, the temperature is 20°C - 30°C;

[0012] And / or, in the step of extracting the first raffinate with the second extractant, the temperature is 20°C - 30°C.

[0013] In one embodiment, the step of stripping the first loaded oil phase includes:

[0014] Mixing the first loaded oil phase with an acidic solution for stripping;

[0015] Or, mixing the first loaded oil phase with an acidic gas and water for stripping.

[0016] In one embodiment, in the step of mixing the first loaded oil phase with an acidic solution for stripping, the acidic solution is selected from at least one of formic acid, acetic acid, nitric acid, hydrochloric acid, sulfuric acid, and phosphoric acid;

[0017] In the step of subjecting the first loaded oil phase to back-extraction by mixing it with an acidic gas and water, the acidic gas is selected from at least one of carbon dioxide, sulfur dioxide, chlorine gas, hydrogen chloride gas, and hydrogen sulfide gas.

[0018] In one embodiment, the step of subjecting the first loaded oil phase to back-extraction includes: subjecting the first loaded oil phase to back-extraction by mixing it with carbon dioxide gas and water.

[0019] In one embodiment, carbon dioxide is also obtained in the step of heat-treating the first back-extract, and the carbon dioxide is recycled for subjecting the first loaded oil phase to back-extraction;

[0020] And / or, carbon dioxide is also obtained in the step of extracting the first raffinate with a second extractant, and the carbon dioxide is recycled for subjecting the first loaded oil phase to back-extraction.

[0021] In one embodiment, the step of subjecting the second loaded oil phase to back-extraction includes:

[0022] Subjecting the second loaded oil phase to back-extraction by mixing it with an acidic solution, wherein the acidic solution is selected from at least one of sulfuric acid, hydrochloric acid, and phosphoric acid;

[0023] Or, subjecting the second loaded oil phase to back-extraction by mixing an acidic gas, water, and the second loaded oil phase, wherein the acidic gas is selected from at least one of sulfur dioxide, chlorine gas, hydrogen chloride gas, and hydrogen sulfide gas.

[0024] In one embodiment, an empty first extractant is also obtained in the step of subjecting the first loaded oil phase to back-extraction, and the empty first extractant is recycled for extracting a lithium-containing alkaline solution containing carbonate;

[0025] And / or, an empty second extractant is also obtained in the step of subjecting the second loaded oil phase to back-extraction, and the empty second extractant is recycled for extracting the first raffinate.

[0026] In the process of the present invention, first, a β-diketone without a halogenated functional group and / or an amino functional group is used as the main extractant for extraction, and then a β-diketone with a halogenated functional group and / or an amino functional group is used as the main extractant for extracting the first raffinate. By combining the segmented extraction-back-extraction processes of the two extractants, high-efficiency extraction can be achieved without pre-treating the lithium-containing alkaline solution containing carbonate, and the dissolution loss rate of the extractant is low, reducing the production cost. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0028] Figure 1 It is a schematic flow diagram of the combined lithium extraction process of the present invention. Detailed implementation manners

[0029] To facilitate the understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention in this specification are only for the purpose of describing specific embodiments or examples, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The said any and all combinations include any two related listed items, any more related listed items, or all related listed items.

[0031] In the present invention, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0032] As Figure 1 shown, the combined lithium extraction process provided by the present invention includes the following steps:

[0033] Use a first extraction liquid to extract an alkaline lithium-containing solution containing carbonate to obtain a first loaded oil phase and a first raffinate. Among them, the main extractant used in the first extraction liquid is selected from β-diketones without halogenated functional groups and / or amino functional groups;

[0034] Perform back-extraction on the first loaded organic phase to obtain a first back-extracted solution, and then prepare lithium carbonate from the first back-extracted solution;

[0035] Extract the first raffinate with a second extractant to obtain a second loaded organic phase, then perform back-extraction on the second loaded organic phase to obtain a second back-extracted solution, and then prepare lithium carbonate from the second back-extracted solution. Among them, the main extractant used in the second extractant is selected from β-diketones containing halogenated functional groups and / or amino functional groups, and an acid stronger than carbonic acid is used for back-extraction of the second loaded organic phase.

[0036] It can be understood that the alkaline lithium-containing solution containing carbonate can be carbonate-type salt lake brine, lithium precipitation mother liquor, etc., and the present invention does not make special requirements for this.

[0037] In the alkaline lithium-containing solution containing carbonate, carbonate will undergo hydrolysis reaction to generate bicarbonate and hydroxide, but this reaction is a reversible reaction, the rate of generating hydroxide is slow and the generated amount is small, so it restricts the lithium extraction reaction. In the process of the present invention, when using β-diketones without halogenated functional groups and / or amino functional groups as the main extractant, hydroxide can be utilized to promote the participation of hydroxide in the displacement reaction between the extractant and lithium ions, so that hydroxide reacts with the displaced hydrogen ions to generate water, thereby enabling the reaction to continuously proceed in the positive direction and improving the extraction rate.

[0038] It can be understood that this step can first extract part of the lithium ions, and in the obtained first raffinate, carbonate and bicarbonate coexist. The specific reaction process is as follows:

[0039]

[0040]

[0041] Furthermore, when using β-diketones containing halogenated functional groups and / or amino functional groups as the main extractant to extract the first raffinate, the β-diketones containing halogenated functional groups and / or amino functional groups can utilize the residual carbonate, hydroxide generated by carbonate hydrolysis, and bicarbonate to further extract lithium ions. The specific reaction process is as follows:

[0042]

[0043]

[0044]

[0045] Therefore, through the combined segmented extraction and stripping process using two β-diketones as the main extractants, the present invention can achieve efficient extraction without pre-treating the alkaline lithium-containing solution with carbonate, and the dissolution loss rate of the extractant is low, reducing the production cost.

[0046] Further, the main extractant used in the first extraction solution is selected from at least one of heptanoylbenzoylmethane, hexanoylbenzoylmethane, dibenzoylmethane, palmitoylbenzoylmethane, dihexanoylmethane, dioctanoylmethane, 1-phenyl-1,3-butanedione, 1-benzoyl-2-nonanone, dibenzoylmethane, stearoylbenzoylmethane.

[0047] Further, the first extraction solution further includes a synergistic extractant, and the volume ratio of the main extractant to the synergistic extractant is 1:2 - 2:1. The synergistic extractant is selected from at least one of trialkyl phosphate, trialkyl phosphine oxide, trioctyl phosphine oxide, trihexyl phosphine oxide, dialkyl phosphate, methyl isobutyl ketone, 1-phenylazo-2-naphthol, n-octanol, isooctanol, 2-ethylhexanol, 14-crown-4 ether, dibutyl butylphosphonate, dibutyl butylphosphate, methylene tetrabutyl bisphosphonate, trioctylamine oxide, 1,10-phenanthroline, quaternary ammonium salt N 263 , at least one of dimethyldi(N-octadecyl)ammonium chloride, methyl dioctyl sulfonium chloride, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0048] Optionally, the diluent of the first extraction solution is selected from at least one of n-hexane, n-dodecane, cyclohexane, D70 special solvent oil, D80 special solvent oil, No. 120 solvent oil, No. 160 solvent oil, No. 200 solvent oil, ordinary kerosene, aviation kerosene, sulfonated kerosene. Further, the volume fraction of the diluent in the first extraction solution is preferably 50% - 70%.

[0049] Further, in the step of extracting the alkaline lithium-containing solution with carbonate using the first extraction solution, the volume ratio of the first extraction solution to the alkaline lithium-containing solution with carbonate is preferably 1:0.05 - 1:5, more preferably 1:0.1 - 1:2, and is specifically adjusted according to the lithium concentration.

[0050] Further, in the step of extracting the alkaline lithium-containing solution with carbonate using the first extraction solution, the temperature is preferably 0°C - 60°C, more preferably 20°C - 30°C.

[0051] Further, the main extractant used in the second extractant is selected from at least one of 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, 1,1,1,2,2-pentafluoro-6,6-dimethyl-3,5-heptanedione, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione, benzoyltrifluoroacetone, benzoyltrichloroacetone, benzoyl-tribromoacetone, 5-fluoroindoline-2,3-dione, 5-fluoropyrimidine-2,4(1H,3H)-dione, 4,4,4-trifluoro-1-(4-tolyl)-1,3-butanedione, 1,3-dimethylpyrimidine-2,4(1H,3H)-dione, indole-2,3-dione, 5,5-dimethylimidazolidine-2,4-dione.

[0052] Further, the second extractant further includes a synergistic extractant, and the volume ratio of the main extractant to the synergistic extractant is 1:2 - 2:1. The synergistic extractant is selected from trialkyl phosphate, trialkyl phosphine oxide, trioctyl phosphine oxide, trihexyl phosphine oxide, dialkyl phosphate, methyl isobutyl ketone, 1-phenylazo-2-naphthol, n-octanol, isooctanol, 2-ethylhexanol, 14-crown-4 ether dibutyl butylphosphonate, dibutyl butyl phosphate, methylene tetrabutyl bisphosphonate, trioctylamine oxide, 1,10-phenanthroline, quaternary ammonium salt N 263 , at least one of dimethyldi(N-octadecyl)ammonium chloride, methyl dioctyl sulfonium chloride, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0053] Optionally, the diluent of the second extractant is selected from at least one of n-hexane, n-dodecane, cyclohexane, D70 special solvent oil, D80 special solvent oil, No. 120 solvent oil, No. 160 solvent oil, No. 200 solvent oil, ordinary kerosene, aviation kerosene, sulfonated kerosene. Further, the volume fraction of the diluent in the second extractant is preferably 50% - 70%.

[0054] Further, in the step of extracting the first raffinate with the second extractant, the volume ratio of the second extractant to the first raffinate is 1:0.02 - 1:4, and more preferably 1:0.1 - 1:1.5, which is specifically adjusted according to the lithium concentration.

[0055] Further, in the step of extracting the first raffinate with the second extractant, the temperature is preferably 0°C - 60°C, and more preferably 20°C - 30°C.

[0056] Since the dissolution loss rate of the extractant in the process of the present invention is low, therefore, the second raffinate obtained when the first raffinate is extracted with the second extractant of the present invention can be discharged after simple treatment, or the second raffinate can be recycled.

[0057] In the process of the present invention, in the step of back-extracting the first loaded oil phase, there is no special requirement for the acid used. Specifically, it may include: mixing the first loaded oil phase with an acidic solution for back-extraction, where the acidic solution is selected from at least one of formic acid, acetic acid, nitric acid, hydrochloric acid, sulfuric acid, and phosphoric acid; or mixing the first loaded oil phase with an acidic gas and water for back-extraction, where the acidic gas is selected from at least one of carbon dioxide, sulfur dioxide, chlorine, hydrogen chloride gas, and hydrogen sulfide gas.

[0058] It can be understood that when mixing the first loaded oil phase with an acidic gas and water for back-extraction, the acidic gas can be first introduced into water to form a mixed solution, and then mixed with the first loaded oil phase for back-extraction, or the acidic gas, water, and the first loaded oil phase can be mixed simultaneously for back-extraction. At this time, the acidic gas is continuously introduced, so that acid production and back-extraction are carried out simultaneously, and the acidic gas and acid coexist, such as carbon dioxide and carbonic acid, hydrogen chloride gas and hydrochloric acid, so that the acidic gas is continuously converted into acid to supplement the reacted acid. Therefore, the concentration of acid in the back-extraction system can be effectively increased, and the back-extraction effect can be improved.

[0059] In order to improve the solubility and dissolution efficiency of the acidic gas in water, it is preferred to introduce the acidic gas under pressure. Optionally, the pressure when introducing the acidic gas in the present invention is 0.1 MPa - 1.6 MPa, further preferably 0.1 MPa - 0.8 MPa, and more preferably 0.2 MPa - 0.6 MPa. In addition, the temperature is preferably 0°C - 40°C, and further preferably 20°C - 30°C.

[0060] Considering that carbon dioxide gas is generated during the extraction of the first raffinate with the second extraction liquid, preferably, the first loaded oil phase is mixed with carbon dioxide gas and water for back-extraction, so that the carbon dioxide gas generated during the extraction of the first raffinate with the second extraction liquid can be recycled. This can not only reduce the amount of acid used, but also obtain high-purity lithium carbonate after heat treatment of the first back-extraction liquid, without using sodium carbonate or the like for lithium precipitation, which is beneficial to cost reduction and at the same time reduces carbon emissions and is beneficial to environmental protection.

[0061] It can be understood that when using carbon dioxide gas for back-extraction, lithium carbonate can be prepared from the first back-extraction liquid by heat treatment. Among them, the temperature of the heat treatment is preferably greater than or equal to 50°C. Considering efficiency and yield, the temperature of the heat treatment is further preferably 70°C - 100°C. In addition, when lithium carbonate is obtained by heat treatment, a lithium precipitation mother liquor and CO2 are also obtained. Preferably, the CO2 is recycled for mixing with the first loaded oil phase for back-extraction, and the lithium precipitation mother liquor can be recycled for mixing with the first loaded oil phase for back-extraction, or can be recycled for mixing with an alkaline lithium-containing solution containing carbonate for extraction.

[0062] When performing back-extraction with acidic solutions such as hydrochloric acid and sulfuric acid, or acidic gases such as hydrogen chloride gas and sulfur dioxide gas, the method for preparing lithium carbonate from the first back-extraction solution can be: mixing the first back-extraction solution with sodium carbonate to obtain lithium carbonate precipitate and mother liquor for lithium precipitation, or mixing the first back-extraction solution with sodium hydroxide and carbon dioxide to obtain lithium carbonate precipitate and mother liquor for lithium precipitation.

[0063] It can be understood that in the step of back-extracting the first loaded oil phase, an empty first extraction solution is also obtained. The empty first extraction solution is preferably recycled for extracting the lithium-containing alkaline solution containing carbonate to achieve the recycling of resources and reduce costs.

[0064] In the process of the present invention, the acid used for back-extracting the second loaded oil phase can be an acid with stronger acidity than carbonic acid such as hydrochloric acid, sulfuric acid, and phosphoric acid. During back-extraction, the second loaded oil phase can be directly mixed with an acidic solution for back-extraction. At this time, the acidic solution is selected from at least one of sulfuric acid, hydrochloric acid, and phosphoric acid; or, an acidic gas, water, and the second loaded oil phase are mixed for back-extraction. At this time, the acidic gas is selected from at least one of sulfur dioxide, chlorine gas, hydrogen chloride gas, and hydrogen sulfide gas.

[0065] Similarly, when mixing the second loaded oil phase with an acidic gas and water for back-extraction, the acidic gas can be first introduced into water to form a mixed solution, and then mixed with the second loaded oil phase for back-extraction, or the acidic gas, water, and the second loaded oil phase are simultaneously mixed for back-extraction with the acidic gas continuously introduced. In addition, the pressure when the acidic gas is introduced is 0.1 MPa - 1.6 MPa, further preferably 0.1 MPa - 0.8 MPa, more preferably 0.2 MPa - 0.6 MPa, and the temperature is preferably 0°C - 40°C, further preferably 20°C - 30°C.

[0066] It can be understood that in the step of back-extracting the second loaded oil phase, an empty second extraction solution is also obtained. The empty second extraction solution is preferably recycled for extracting the first raffinate to achieve the recycling of resources and reduce costs.

[0067] Similarly, the method for preparing lithium carbonate from the second back-extraction solution can be: mixing the second back-extraction solution with sodium carbonate to obtain lithium carbonate precipitate and mother liquor for lithium precipitation, or mixing the second back-extraction solution with sodium hydroxide and carbon dioxide to obtain lithium carbonate precipitate and mother liquor for lithium precipitation.

[0068] Hereinafter, the combined lithium extraction process will be further described through the following specific examples.

[0069] Example 1

[0070] Using heptanoyl benzoyl methane as the main extractant, trialkyl phosphate as the synergistic extractant, and D70 special solvent oil as the diluent, they are mixed to obtain the first extraction solution. Control the volume fraction of heptanoyl benzoyl methane in the first extraction solution to be 10%, the volume fraction of trialkyl phosphate to be 20%, and the volume fraction of D70 special solvent oil to be 70%. Mix the lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 with the first extraction solution for extraction, control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.5:1, and the extraction temperature to be 20°C. After phase separation, obtain the first loaded oil phase with a lithium concentration of 1.5322 g / L and the first raffinate with a pH of 9.56.

[0071] Continuously introduce water and CO2 into the first loaded oil phase for back extraction, control the CO2 introduction pressure to be 0.2 MPa, and the back extraction temperature to be 20°C. After phase separation, obtain the first back extraction solution, and then heat the first back extraction solution to 85°C to obtain lithium carbonate, lithium precipitation mother liquor, and CO2, where CO2 is recycled and introduced into the first loaded oil phase for back extraction.

[0072] At the same time, use 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione as the main extractant, trialkyl phosphine oxide as the synergistic extractant, and D70 special solvent oil as the diluent, and mix them to obtain the second extraction solution. Control the volume fraction of 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione in the second extraction solution to be 10%, the volume fraction of trialkyl phosphine oxide to be 20%, and the volume fraction of D70 special solvent oil to be 70%. Then mix the second extraction solution with the first raffinate for extraction, control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.4:1, and the extraction temperature to be 20°C. After phase separation, obtain the second loaded oil phase with a lithium concentration of 2.0469 g / L and the second raffinate with a pH of 7.40. At the same time, CO2 is generated during the extraction process, and CO2 is recycled and introduced into the first loaded oil phase for back extraction.

[0073] Then mix the second loaded oil phase with sulfuric acid for back extraction, control the back extraction temperature to be 20°C. After phase separation, obtain the second back extraction solution. At a reaction temperature of 80°C, add solid sodium carbonate to the second back extraction solution while stirring. React to generate lithium carbonate precipitate and lithium precipitation mother liquor, and the lithium precipitation mother liquor is re-extracted to extract lithium.

[0074] In this example, the lithium extraction rate when using the first extraction solution for extraction is 47.88%, the lithium extraction rate when using the second extraction solution for extraction is 98.18%, and the total lithium extraction rate is 99.05%. The dissolution loss rate of the first extraction solution is 0.0045%, the dissolution loss rate of the second extraction solution is 0.0074%, and the total dissolution loss rate of the extraction solution is 0.0119%.

[0075] Example 2

[0076] Using hexanoylbenzoylmethane as the main extractant, trioctylphosphine oxide as the co-extractant, and n-dodecane as the diluent, a first extraction solution is obtained by mixing. Control the volume fraction of hexanoylbenzoylmethane in the first extraction solution to be 15%, the volume fraction of trioctylphosphine oxide as the co-extractant to be 15%, and the volume fraction of n-dodecane to be 70%. Mix the lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.5 with the first extraction solution for extraction, control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.4:1, and the extraction temperature to be 20 °C. After phase separation, a first loaded oil phase with a lithium concentration of 1.9780 g / L and a first raffinate with a pH of 9.31 are obtained.

[0077] Continuously introduce water and CO2 into the first loaded oil phase for back-extraction. Control the CO2 introduction pressure to be 0.2 MPa and the back-extraction temperature to be 20 °C. After phase separation, a first back-extraction solution is obtained. Then heat the first back-extraction solution to 85 °C to obtain lithium carbonate, lithium precipitation mother liquor, and CO2, where CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0078] Meanwhile, using 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione as the main extractant, methyl isobutyl ketone as the co-extractant, and D70 special solvent oil as the diluent, a second extraction solution is obtained by mixing. Control the volume fraction of 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione in the second extraction solution to be 15%, the volume fraction of methyl isobutyl ketone to be 15%, and the volume fraction of D70 special solvent oil to be 70%. Then mix the second extraction solution with the first raffinate for extraction. Control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.3:1 and the extraction temperature to be 20 °C. After phase separation, a second loaded oil phase with a lithium concentration of 2.6747 g / L and a second raffinate with a pH of 7.26 are obtained. At the same time, CO2 is generated during the extraction process, and CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0079] Then mix the second loaded oil phase with sulfuric acid for back-extraction. Control the back-extraction temperature to be 20 °C. After phase separation, a second back-extraction solution is obtained. At a reaction temperature of 85 °C, add solid sodium carbonate to the second back-extraction solution while stirring. Lithium carbonate precipitate and lithium precipitation mother liquor are generated by the reaction, and the lithium precipitation mother liquor is re-extracted to extract lithium.

[0080] In this example, the lithium extraction rate when using the first extraction solution for extraction is 49.45%, the lithium extraction rate when using the second extraction solution for extraction is 99.21%, and the total lithium extraction rate is 99.60%. The dissolution loss rate of the first extraction solution is 0.0049%, the dissolution loss rate of the second extraction solution is 0.008%, and the total dissolution loss rate of the extraction solution is 0.0129%.

[0081] Example 3

[0082] Using dihexanoylmethane as the main extractant, n-octanol as the co-extractant, and n-hexane as the diluent, they are mixed to obtain the first extraction solution. Control the volume fraction of dihexanoylmethane in the first extraction solution to be 20%, the volume fraction of n-octanol to be 10%, and the volume fraction of n-hexane to be 70%. Mix the lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 with the first extraction solution for extraction. Control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.45:1, and the extraction temperature to be 20°C. After phase separation, obtain the first loaded oil phase with a lithium concentration of 1.7305 g / L and the first raffinate with a pH of 9.41.

[0083] Continuously introduce water and CO2 into the first loaded oil phase for back-extraction. Control the CO2 introduction pressure to be 0.3 MPa and the back-extraction temperature to be 20°C. After phase separation, obtain the first back-extraction solution. Then heat the first back-extraction solution to 85°C to obtain lithium carbonate, lithium precipitation mother liquor, and CO2, where CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0084] Meanwhile, using benzoyltrifluoroacetone as the main extractant, 2-ethylhexanol as the co-extractant, and solvent naphtha No. 120 as the diluent, they are mixed to obtain the second extraction solution. Control the volume fraction of benzoyltrifluoroacetone to be 20%, the volume fraction of 2-ethylhexanol to be 10%, and the volume fraction of solvent naphtha No. 120 to be 70%. Then mix the second extraction solution with the first raffinate for extraction. Control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.4:1, and the extraction temperature to be 20°C. After phase separation, obtain the second loaded oil phase with a lithium concentration of 2.0255 g / L and the second raffinate with a pH of 7.30. Meanwhile, CO2 is generated during the extraction process, and CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0085] Then mix the second loaded oil phase with sulfuric acid for back-extraction. Control the back-extraction temperature to be 20°C. After phase separation, obtain the second back-extraction solution. At a reaction temperature of 90°C, add solid sodium carbonate to the second back-extraction solution while stirring. React to form lithium carbonate precipitate and lithium precipitation mother liquor, and the lithium precipitation mother liquor is re-extracted to extract lithium.

[0086] In this example, the lithium extraction rate when using the first extraction solution for extraction is 48.67%, the lithium extraction rate when using the second extraction solution for extraction is 98.65%, and the total lithium extraction rate is 99.31%. The dissolution loss rate of the first extraction solution is 0.0047%, the dissolution loss rate of the second extraction solution is 0.0085%, and the total dissolution loss rate of the extraction solution is 0.0132%.

[0087] Example 4

[0088] Using 1-phenyl-1,3-butanedione as the main extractant, isooctanol as the co-extractant, and sulfonated kerosene as the diluent, they are mixed to obtain the first extraction solution. Control the volume fraction of 1-phenyl-1,3-butanedione in the first extraction solution to be 20%, the volume fraction of isooctanol to be 20%, and the volume fraction of sulfonated kerosene to be 60%. Mix the lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.5 with the first extraction solution for extraction, control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.35:1, and the extraction temperature to be 20°C. After phase separation, a first loaded oil phase with a lithium concentration of 2.2757 g / L and a first raffinate with a pH of 9.26 are obtained.

[0089] Continuously introduce water and CO2 into the first loaded oil phase for back-extraction, control the CO2 introduction pressure to be 0.4 MPa, and the back-extraction temperature to be 20°C. After phase separation, a first back-extraction solution is obtained. Then heat the first back-extraction solution to 80°C to obtain lithium carbonate, lithium precipitation mother liquor, and CO2, where CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0090] At the same time, use 5-fluoroindoline-2,3-dione as the main extractant, trioctylamine oxide as the co-extractant, and cyclohexane as the diluent, and mix them to obtain the second extraction solution. Control the volume fraction of 5-fluoroindoline-2,3-dione to be 20%, the volume fraction of trioctylamine oxide to be 15%, and the volume fraction of cyclohexane to be 65%. Then mix the second extraction solution with the first raffinate for extraction, control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.35:1, and the extraction temperature to be 20°C. After phase separation, a second loaded oil phase with a lithium concentration of 2.2797 g / L and a second raffinate with a pH of 7.11 are obtained. At the same time, CO2 is generated during the extraction process, and CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0091] Then mix the second loaded oil phase with sulfuric acid for back-extraction, control the back-extraction temperature to be 20°C. After phase separation, a second back-extraction solution is obtained. At a reaction temperature of 85°C, add solid sodium carbonate to the second back-extraction solution while stirring. Lithium carbonate precipitate and lithium precipitation mother liquor are generated by the reaction, and the lithium precipitation mother liquor is re-extracted to extract lithium.

[0092] In this example, the lithium extraction rate when using the first extraction solution for extraction is 49.78%, the lithium extraction rate when using the second extraction solution for extraction is 99.30%, and the total lithium extraction rate is 99.65%. The dissolution loss rate of the first extraction solution is 0.0052%, the dissolution loss rate of the second extraction solution is 0.0092%, and the total dissolution loss rate of the extraction solution is 0.0144%.

[0093] Example 5

[0094] Using 1-benzoyl-2-nonanone as the main extractant, dibutyl butylphosphonate as the co-extractant, and solvent oil No. 160 as the diluent, they are mixed to obtain the first extraction solution. Control the volume fraction of 1-benzoyl-2-nonanone in the first extraction solution to be 25%, the volume fraction of dibutyl butylphosphonate to be 25%, and the volume fraction of solvent oil No. 160 to be 50%. Mix the lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 with the first extraction solution for extraction, control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.45:1, and the extraction temperature to be 20°C. After phase separation, a first loaded oil phase with a lithium concentration of 1.7788 g / L and a first raffinate with a pH of 9.36 are obtained.

[0095] Continuously introduce water and CO2 into the first loaded oil phase for back-extraction. Control the CO2 introduction pressure to be 0.2 MPa and the back-extraction temperature to be 20°C. After phase separation, a first back-extraction solution is obtained. Then heat the first back-extraction solution to 85°C to obtain lithium carbonate, lithium precipitation mother liquor, and CO2, where CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0096] Meanwhile, using 5,5-dimethylimidazolidine-2,4-dione as the main extractant, quaternary ammonium salt N263 as the co-extractant, and solvent oil No. 160 as the diluent, they are mixed to obtain the second extraction solution. Control the volume fraction of 5,5-dimethylimidazolidine-2,4-dione to be 20%, the volume fraction of quaternary ammonium salt N263 to be 25%, and the volume fraction of solvent oil No. 160 to be 55%. Then mix the second extraction solution with the first raffinate for extraction. Control the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.35:1, and the extraction temperature to be 20°C. After phase separation, a second loaded oil phase with a lithium concentration of 2.2670 g / L and a second raffinate with a pH of 7.20 are obtained. At the same time, CO2 is generated during the extraction process, and CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0097] Then mix the second loaded oil phase with sulfuric acid for back-extraction. Control the back-extraction temperature to be 20°C. After phase separation, a second back-extraction solution is obtained. At a reaction temperature of 85°C, add solid sodium carbonate to the second back-extraction solution while stirring. The reaction generates lithium carbonate precipitate and lithium precipitation mother liquor, and the lithium precipitation mother liquor is re-extracted to extract lithium.

[0098] In this example, the lithium extraction rate when using the first extraction solution for extraction is 50.03%, the lithium extraction rate when using the second extraction solution for extraction is 99.24%, and the total lithium extraction rate is 99.62%. The dissolution loss rate of the first extraction solution is 0.0048%, the dissolution loss rate of the second extraction solution is 0.0084%, and the total dissolution loss rate of the extraction solution is 0.0132%.

[0099] Comparative Example 1

[0100] Using 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione as the main extractant, trialkyl phosphine oxide as the co-extractant, and D70 special solvent oil as the diluent, an extraction solution is obtained by mixing. The volume fraction of 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione in the extraction solution is controlled to be 10%, the volume fraction of trialkyl phosphine oxide is 20%, and the volume fraction of D70 special solvent oil is 70%. A lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 is mixed with the raffinate for extraction, and the volume ratio of the extraction solution to the lithium precipitation mother liquor is controlled to be 0.7:1. The extraction temperature is 20 °C. After phase separation, a loaded oil phase with a lithium concentration of 2.2374 g / L and a raffinate with a pH of 7.22 are obtained, and CO2 is generated during the extraction process.

[0101] Then, the loaded oil phase is mixed with sulfuric acid for back-extraction. The back-extraction temperature is controlled to be 20 °C. After phase separation, a back-extraction solution is obtained. At a reaction temperature of 80 °C, solid sodium carbonate is added to the back-extraction solution while stirring. Lithium carbonate precipitate and lithium precipitation mother liquor are generated by the reaction, and the lithium precipitation mother liquor is re-extracted to extract lithium.

[0102] In this comparative example, the lithium extraction rate during extraction with the extraction solution is 97.89%, and the dissolution loss rate of the extraction solution is 0.48%.

[0103] Comparative Example 2

[0104] Using tributyl phosphate as the main extractant, trialkyl phosphate as the co-extractant, and D70 special solvent oil as the diluent, a first extraction solution is obtained by mixing. The volume fraction of tributyl phosphate in the first extraction solution is controlled to be 10%, the volume fraction of trialkyl phosphate is 20%, and the volume fraction of D70 special solvent oil is 70%. A lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 is mixed with the first extraction solution for extraction, and the volume ratio of the first extraction solution to the lithium precipitation mother liquor is controlled to be 0.6:1. The extraction temperature is 20 °C. After phase separation, a first loaded oil phase with a lithium concentration of 0.5312 g / L and a first raffinate with a pH of 9.92 are obtained.

[0105] Water and CO2 are continuously introduced into the first loaded oil phase for back-extraction. The CO2 introduction pressure is controlled to be 0.2 MPa, and the back-extraction temperature is 20 °C. After phase separation, a first back-extraction solution is obtained. Then, the first back-extraction solution is heated to 85 °C to obtain lithium carbonate, lithium precipitation mother liquor, and CO2, where the CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0106] Meanwhile, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione is used as the main extractant, trialkyl phosphine oxide as the co-extractant, and D70 special solvent oil as the diluent. They are mixed to obtain the second extraction solution, and the volume fraction of 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione in the second extraction solution is controlled to be 10%, the volume fraction of trialkyl phosphine oxide is 20%, and the volume fraction of D70 special solvent oil is 70%. Then the second extraction solution is mixed with the first raffinate for extraction. The volume ratio of the first extraction solution to the lithium precipitation mother liquor is controlled to be 0.5:1, the extraction temperature is 20 °C. After phase separation, a second loaded oil phase with a lithium concentration of 2.3882 g / L and a second raffinate with a pH of 7.62 are obtained. Meanwhile, CO2 is generated during the extraction process, and the CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0107] Then the second loaded oil phase is mixed with sulfuric acid for back-extraction. The back-extraction temperature is controlled to be 20 °C. After phase separation, a second back-extraction solution is obtained. At a reaction temperature of 80 °C, solid sodium carbonate is added to the second back-extraction solution while stirring. Lithium carbonate precipitate and the lithium precipitation mother liquor are generated by the reaction, and the lithium precipitation mother liquor is re-extracted to extract lithium.

[0108] In this comparative example, the lithium extraction rate when using the first extraction solution for extraction is 23.24%, the lithium extraction rate when using the second extraction solution for extraction is 97.23%, and the total lithium extraction rate is 97.87%. The dissolution loss rate of the first extraction solution is 0.125%, the dissolution loss rate of the second extraction solution is 0.35%, and the total dissolution loss rate of the extraction solution is 0.475%.

[0109] Comparative Example 3

[0110] 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester is used as the main extractant, trialkyl phosphate as the co-extractant, and D70 special solvent oil as the diluent. They are mixed to obtain the first extraction solution, and the volume fraction of 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester in the first extraction solution is controlled to be 10%, the volume fraction of trialkyl phosphate is 20%, and the volume fraction of D70 special solvent oil is 70%. The lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 is mixed with the first extraction solution for extraction. The volume ratio of the first extraction solution to the lithium precipitation mother liquor is controlled to be 0.7:1, the extraction temperature is 20 °C. After phase separation, a first loaded oil phase with a lithium concentration of 0.4338 g / L and a first raffinate with a pH of 10.01 are obtained.

[0111] Water and CO2 are continuously introduced into the first loaded oil phase for back-extraction. The pressure of CO2 introduction is controlled to be 0.2 MPa, the back-extraction temperature is 20 °C. After phase separation, a first back-extraction solution is obtained. Then the first back-extraction solution is heated to 85 °C to obtain lithium carbonate, the lithium precipitation mother liquor, and CO2, where the CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0112] Meanwhile, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione is used as the main extractant, trialkyl phosphine oxide is used as the co-extractant, and D70 special solvent oil is used as the diluent. They are mixed to obtain the second extraction solution. The volume fraction of 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione in the second extraction solution is controlled to be 10%, the volume fraction of trialkyl phosphine oxide is 20%, and the volume fraction of D70 special solvent oil is 70%. Then the second extraction solution is mixed with the first raffinate for extraction. The volume ratio of the first extraction solution to the lithium precipitation mother liquor is controlled to be 0.5:1, the extraction temperature is 20°C. After phase separation, a second loaded oil phase with a lithium concentration of 2.5177 g / L and a second raffinate with a pH of 7.71 are obtained. At the same time, CO2 is generated during the extraction process, and the CO2 is recycled and introduced into the first loaded oil phase for back extraction.

[0113] Then the second loaded oil phase is mixed with sulfuric acid for back extraction. The back extraction temperature is controlled to be 20°C. After phase separation, a second back extraction solution is obtained. At a reaction temperature of 80°C, solid sodium carbonate is added to the second back extraction solution while stirring. Lithium carbonate precipitate and lithium precipitation mother liquor are generated by the reaction, and the lithium precipitation mother liquor is re-extracted to extract lithium.

[0114] In this comparative example, the lithium extraction rate during extraction with the first extraction solution is 18.98%, the lithium extraction rate during extraction with the second extraction solution is 97.11%, and the total lithium extraction rate is 97.66%. The dissolution loss rate of the first extraction solution is 0.101%, the dissolution loss rate of the second extraction solution is 0.40%, and the total dissolution loss rate of the extractant is 0.501%.

[0115] Comparative Example 4

[0116] Heptanoyl benzoyl methane is used as the main extractant, trialkyl phosphate is used as the co-extractant, and D70 special solvent oil is used as the diluent. They are mixed to obtain the first extraction solution. The volume fraction of heptanoyl benzoyl methane in the first extraction solution is controlled to be 10%, the volume fraction of trialkyl phosphate is 20%, and the volume fraction of D70 special solvent oil is 70%. The lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 is mixed with the first extraction solution for extraction. The volume ratio of the first extraction solution to the lithium precipitation mother liquor is controlled to be 0.5:1, the extraction temperature is 20°C. After phase separation, a first loaded oil phase with a lithium concentration of 1.5325 g / L and a first raffinate with a pH of 9.55 are obtained.

[0117] Water and CO2 are continuously introduced into the first loaded oil phase for back extraction. The pressure of CO2 introduction is controlled to be 0.2 MPa, the back extraction temperature is 20°C. After phase separation, a first back extraction solution is obtained. Then the first back extraction solution is heated to 85°C to obtain lithium carbonate, lithium precipitation mother liquor, and CO2, where the CO2 is recycled and introduced into the first loaded oil phase for back extraction.

[0118] Meanwhile, palmitoyl benzoyl methane is used as the main extractant, trialkyl phosphine oxide as the co-extractant, and D70 special solvent oil as the diluent. They are mixed to obtain the second extraction liquid. Control the content of palmitoyl benzoyl methane in the second extraction liquid to be 10%, the volume fraction of trialkyl phosphine oxide to be 20%, and the volume fraction of D70 special solvent oil to be 70%. Then mix the second extraction liquid with the first raffinate for extraction. Control the volume ratio of the first extraction liquid to the lithium precipitation mother liquor to be 0.4:1, and the extraction temperature to be 20°C. After phase separation, a second loaded oil phase with a lithium concentration of 0.0542 g / L and a second raffinate with a pH of 9.11 are obtained. Meanwhile, CO2 is generated during the extraction process, and the CO2 is recycled and introduced into the first loaded oil phase for back extraction.

[0119] Then mix the second loaded oil phase with sulfuric acid for back extraction. Control the back extraction temperature to be 20°C. After phase separation, a second back extraction liquid is obtained. At a reaction temperature of 80°C, add solid sodium carbonate to the second back extraction liquid while stirring. Lithium carbonate precipitate and lithium precipitation mother liquor are generated by the reaction, and the lithium precipitation mother liquor is recycled for lithium extraction by extraction.

[0120] In this comparative example, the lithium extraction rate when using the first extraction liquid for extraction is 47.88%, the lithium extraction rate when using the second extraction liquid for extraction is 2.60%, and the total lithium extraction rate is 49.24%. The dissolution loss rate of the first extraction liquid is 0.0046%, the dissolution loss rate of the second extraction liquid is 0.0041%, and the total dissolution loss rate of the extractant is 0.0087%.

[0121] Comparative Example 5

[0122] Use heptanoyl benzoyl methane as the main extractant, trialkyl phosphate as the co-extractant, and D70 special solvent oil as the diluent. Mix them to obtain the first extraction liquid. Control the volume fraction of heptanoyl benzoyl methane in the first extraction liquid to be 10%, the volume fraction of trialkyl phosphate to be 20%, and the volume fraction of D70 special solvent oil to be 70%. Mix the lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 with the first extraction liquid for extraction. Control the volume ratio of the first extraction liquid to the lithium precipitation mother liquor to be 0.5:1, and the extraction temperature to be 20°C. After phase separation, a first loaded oil phase with a lithium concentration of 1.5325 g / L and a first raffinate with a pH of 9.55 are obtained.

[0123] Continuously introduce water and CO2 into the first loaded oil phase for back extraction. Control the CO2 introduction pressure to be 0.2 MPa and the back extraction temperature to be 20°C. After phase separation, a first back extraction liquid is obtained. Then heat the first back extraction liquid to 85°C to obtain lithium carbonate, lithium precipitation mother liquor, and CO2, where the CO2 is recycled and introduced into the first loaded oil phase for back extraction.

[0124] Meanwhile, trioctyldecyl tertiary amine is used as the main extractant, trialkyl phosphine oxide as the synergistic extractant, and D70 special solvent oil as the diluent. They are mixed to obtain the second extraction liquid, with the content of trioctyldecyl tertiary amine in the second extraction liquid controlled at 10%, the volume fraction of trialkyl phosphine oxide at 20%, and the volume fraction of D70 special solvent oil at 70%. Then, the second extraction liquid is mixed with the first raffinate for extraction, with the volume ratio of the first extraction liquid to the lithium precipitation mother liquor controlled at 0.4:1 and the extraction temperature at 20°C. After phase separation, a second loaded oil phase with a lithium concentration of 0.0667 g / L and a second raffinate with a pH of 9.03 are obtained. Meanwhile, CO2 is generated during the extraction process, and the CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0125] Then, the second loaded oil phase is mixed with sulfuric acid for back-extraction, with the back-extraction temperature controlled at 20°C. After phase separation, a second back-extraction liquid is obtained. At a reaction temperature of 80°C, solid sodium carbonate is added to the second back-extraction liquid while stirring. Lithium carbonate precipitate and the lithium precipitation mother liquor are generated by the reaction, and the lithium precipitation mother liquor is recycled for lithium extraction by extraction.

[0126] In this comparative example, the lithium extraction rate during extraction with the first extraction liquid is 47.88%, the lithium extraction rate during extraction with the second extraction liquid is 3.01%, and the total lithium extraction rate is 49.55%. The dissolution loss rate of the first extraction liquid is 0.0044%, the dissolution loss rate of the second extraction liquid is 0.0102%, and the total dissolution loss rate of the extractant is 0.0146%.

[0127] Comparative Example 6

[0128] Heptanoyl benzoyl methane is used as the main extractant, trialkyl phosphate as the synergistic extractant, and D70 special solvent oil as the diluent. They are mixed to obtain the first extraction liquid, with the volume fraction of heptanoyl benzoyl methane in the first extraction liquid controlled at 10%, the volume fraction of trialkyl phosphate at 20%, and the volume fraction of D70 special solvent oil at 70%. The lithium precipitation mother liquor with a lithium concentration of 1.6 g / L, a carbonate concentration of 10.4 g / L, and a pH of 10.6 is mixed with the first extraction liquid for extraction, with the volume ratio of the first extraction liquid to the lithium precipitation mother liquor controlled at 0.5:1 and the extraction temperature at 20°C. After phase separation, a first loaded oil phase with a lithium concentration of 1.5325 g / L and a first raffinate with a pH of 9.55 are obtained.

[0129] Water and CO2 are continuously introduced into the first loaded oil phase for back-extraction, with the CO2 introduction pressure controlled at 0.2 MPa and the back-extraction temperature at 20°C. After phase separation, a first back-extraction liquid is obtained. Then, the first back-extraction liquid is heated to 85°C to obtain lithium carbonate, the lithium precipitation mother liquor, and CO2, where the CO2 is recycled and introduced into the first loaded oil phase for back-extraction.

[0130] Meanwhile, perfluoro-15-crown-5 is used as the main extractant, trialkyl phosphine oxide as the co-extractant, and D70 special solvent oil as the diluent. They are mixed to obtain the second extraction solution, controlling the content of trioctyldecyl tertiary amine in the second extraction solution to be 10%, the volume fraction of trialkyl phosphine oxide to be 20%, and the volume fraction of D70 special solvent oil to be 70%. Then, the second extraction solution is mixed with the first raffinate for extraction, controlling the volume ratio of the first extraction solution to the lithium precipitation mother liquor to be 0.4:1, and the extraction temperature to be 20°C. After phase separation, a second loaded oil phase with a lithium concentration of 0.0875 g / L and a second raffinate with a pH of 8.86 are obtained. Meanwhile, CO2 is generated during the extraction process, and the CO2 is recycled and introduced into the first loaded oil phase for back extraction.

[0131] Then, the second loaded oil phase is mixed with sulfuric acid for back extraction, controlling the back extraction temperature to be 20°C. After phase separation, a second back extraction solution is obtained. At a reaction temperature of 80°C, solid sodium carbonate is added to the second back extraction solution while stirring. Lithium carbonate precipitate and the lithium precipitation mother liquor are generated by the reaction, and the lithium precipitation mother liquor is reused for lithium extraction by extraction.

[0132] In this comparative example, the lithium extraction rate when using the first extraction solution for extraction is 47.88%, the lithium extraction rate when using the second extraction solution for extraction is 4.22%, and the total lithium extraction rate is 50.07%. The dissolution loss rate of the first extraction solution is 0.0041%, the dissolution loss rate of the second extraction solution is 0.0117%, and the total dissolution loss rate of the extractant is 0.0158%.

[0133] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0134] The above-described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A combined lithium extraction process, characterized in that: The following steps are involved: The alkaline lithium-containing solution containing carbonate is extracted with a first extracting liquid to obtain a first loaded oil phase and a first raffinate, wherein the main extracting agent used in the first extracting liquid is selected from β-diketones that do not contain halogenated functional groups and / or amino functional groups; Stripping the first loaded oil phase to obtain a first stripping solution, and then preparing lithium carbonate from the first stripping solution; The first raffinate is extracted with a second extracting liquid to obtain a second loaded oil phase, and then the second loaded oil phase is stripped to obtain a second stripping liquid, and then lithium carbonate is prepared from the second stripping liquid, wherein the main extracting agent used in the second extracting liquid is selected from β-diketones containing halogenated functional groups and / or amino functional groups, and an acid with stronger acidity than carbonic acid is used when stripping the second loaded oil phase.

2. The combined lithium extraction process according to claim 1, characterized in that: The main extractant used in the first extract is selected from at least one of heptanoylbenzoylmethane, hexanoylbenzoylmethane, dibenzoylmethane, palmitoylbenzoylmethane, dihexanoylmethane, dioctanoylmethane, 1-phenyl-1,3-butanedione, 1-benzoyl-2-nonanone, dibenzoylmethane, and stearylbenzoylmethane; And / or, the main extractant used in the second extract is at least one selected from 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, 1,1,1,2,2-pentafluoro-6,6-dimethyl-3,5-heptanedione, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione, benzoyltrifluoroacetone, benzoyltrichloroacetone, benzoyltribromoacetone, 5-fluoroindoline-2,3-dione, 5-fluoropyrimidine-2,4(1H,3H)-dione, 4,4,4-trifluoro-1-(4-methylphenyl)-1,3-butanedione, 1,3-dimethylpyrimidine-2,4(1H,3H)-dione, indole-2,3-dione, and 5,5-dimethylimidazolidine-2,4-dione.

3. The combined lithium extraction process according to claim 1, characterized in that: The first extract and the second extract both further include a co-extractant, the volume ratio of the main extractant to the co-extractant is independently selected from 1:2-2:1, and the co-extractants are independently selected from trialkyl phosphates, trialkyl phosphine oxides, trioctyl phosphine oxide, trihexyl phosphine oxide, dialkyl phosphates, methyl isobutyl ketone, 1-phenylazo-2-naphthol, n-octanol, isooctyl alcohol, 2-ethylhexanol, 14-crown-4 ether butyl phosphonic acid dibutyl ester, butyl phosphate dibutyl ester, methylene tetrabutyl diphosphate, trioctylamine oxide, 1,10-phenanthroline, quaternary ammonium salt N 263 , dimethyldi(N-octadecyl)ammonium chloride, methyldioctylsulfonium chloride, and 1-hydroxyethyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide.

4. The combined lithium extraction process according to claim 1, characterized in that: In the step of extracting the carbonate-containing alkaline lithium-containing solution with the first extracting liquid, the temperature is 20° C.-30° C.; And / or, in the step of extracting the first raffinate with the second extracting liquid, the temperature is 20°C-30°C.

5. The combined lithium extraction process according to any one of claims 1 to 4, characterized in that: The step of stripping the first loaded oil phase comprises: mixing the first loaded oil phase with an acidic solution for stripping; Alternatively, the first loaded oil phase is mixed with acidic gas and water for stripping.

6. The combined lithium extraction process according to claim 5, characterized in that: In the step of mixing the first loaded oil phase with an acidic solution for stripping, the acidic solution is selected from at least one of formic acid, acetic acid, nitric acid, hydrochloric acid, sulfuric acid, and phosphoric acid; In the step of mixing the first loaded oil phase with an acidic gas and water for stripping, the acidic gas is selected from at least one of carbon dioxide, sulfur dioxide, chlorine, hydrogen chloride gas, and hydrogen sulfide gas.

7. The combined lithium extraction process according to claim 6, characterized in that: The step of stripping the first loaded oil phase includes: mixing the first loaded oil phase with carbon dioxide gas and water for stripping.

8. The combined lithium extraction process according to claim 7, characterized in that: The step of heat-treating the first stripping liquid also produces carbon dioxide, which is circulated for stripping the first loaded oil phase; And / or, carbon dioxide is obtained in the step of extracting the first raffinate with the second extracting liquid, and the carbon dioxide is recycled for stripping the first loaded oil phase.

9. The combined lithium extraction process according to any one of claims 1 to 4, characterized in that: The step of stripping the second loaded oil phase comprises: Mixing the second loaded oil phase with an acidic solution for stripping, wherein the acidic solution is selected from at least one of sulfuric acid, hydrochloric acid, and phosphoric acid; Alternatively, the acidic gas, water and the second loaded oil phase are mixed for stripping, wherein the acidic gas is selected from at least one of sulfur dioxide, chlorine, hydrogen chloride gas and hydrogen sulfide gas.

10. The combined lithium extraction process according to any one of claims 1 to 4, characterized in that: The step of stripping the first loaded oil phase also obtains an empty first extract, and the empty first extract is circulated to extract the carbonate-containing alkaline lithium-containing solution; And / or, in the step of stripping the second loaded oil phase, an empty second extract is obtained, and the empty second extract is circulated to extract the first raffinate.

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