Method for extracting lithium from liquid after lithium precipitation and extraction system thereof

Abstract

The invention provides a method and an extraction system for extracting lithium from lithium-precipitated liquid, the method comprises the following steps: S1, providing an extraction water phase and an extraction organic phase, the extraction water phase is the lithium-precipitated liquid, the extraction organic phase comprises an extraction agent, a synergistic extraction agent, a phase stabilizer and a diluent, the extraction agent comprises a component A and a component B, the component B comprises a component C and a component D, and the component C comprises a component C and a component D; the component A is selected from one or a combination of two of dibenzoylmethane and calcium dibenzoylmethane, and the component B is selected from one or a combination of two of di (2-ethylhexyl) phosphate and 2-ethylhexyl phosphoric acid; s2, mixing the extracted water phase and the extracted organic phase, and extracting to obtain a loaded organic phase and raffinate; s3, washing the loaded organic phase to wash out sodium ions in the solution so as to obtain sodium washing water and the loaded organic phase after sodium washing; and S4, carrying out back extraction on the loaded organic phase after sodium washing to obtain a lithium-containing back extraction solution. According to the method, the lithium can be efficiently and stably extracted in the alkaline liquid after lithium precipitation at low cost.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion extraction, and in particular to a method for extracting lithium from a post-lithium precipitation liquid and an extraction system thereof. Background Art

[0002] After disassembly, crushing, leaching, and extraction of Co, Ni, and Mn, waste power batteries can obtain lithium-containing raffinate. The lithium-containing extract can be concentrated and precipitated to obtain crude lithium carbonate, which can be further processed to obtain battery-grade lithium carbonate. In the above process, a lithium-containing and alkaline solution is produced: the lithium precipitation solution.

[0003] Since the post-lithium precipitation liquid also contains lithium, it is also necessary to extract lithium from the post-lithium precipitation liquid. Currently, the most commonly used method is to extract lithium through a β-diketone-organic phosphine synergistic extraction system. In the prior art, the extractants used, such as LIX54, benzoyltrifluoroacetone, and synergistic extractants such as trioctylphosphine oxide and trialkylphosphine oxide, are actually very expensive and are not suitable for large-scale industrial applications. Summary of the invention

[0004] In view of this, the present invention provides a method for extracting lithium from a post-lithium precipitation solution and an extraction system thereof, wherein the method can extract lithium from an alkaline post-lithium precipitation solution efficiently, at low cost and stably.

[0005] The present invention provides a method for extracting lithium from a solution after lithium precipitation, the method comprising the following steps:

[0006] S1: providing an aqueous extraction phase and an organic extraction phase, wherein the aqueous extraction phase is a post-lithium precipitation solution, and the organic extraction phase comprises an extractant, a co-extractant, a phase stabilizer and a diluent, wherein the extractant is composed of a component A and a component B, wherein the component A is selected from one or a combination of dibenzoylmethane and calcium dibenzoylmethane, and the component B is selected from one or a combination of di(2-ethylhexyl) phosphate and 2-ethylhexyl phosphoric acid;

[0007] S2: mixing the extracted aqueous phase and the extracted organic phase, and extracting to obtain a loaded organic phase and a raffinate;

[0008] S3: washing the loaded organic phase to wash away the sodium ions in the solution to obtain sodium washing water and a sodium-washed loaded organic phase;

[0009] S4: stripping the loaded organic phase after sodium washing to obtain a stripping solution containing lithium.

[0010] Furthermore, in the extractant, the concentration of the component A is less than 0.8 mol / L, the concentration of the component B is less than 0.3 mol / L, and the total concentration of the component A and the component B is 0.4-0.8 mol / L.

[0011] Furthermore, the co-extractant is selected from one or a combination of trioctyl phosphate and tributyl phosphate.

[0012] Furthermore, the concentration of each component of the synergistic extractant is less than 1.2 mol / L.

[0013] Furthermore, the phase stabilizer is selected from one or a combination of n-octanol, n-hexanol and n-pentanol, and the diluent is selected from 260# or 200# solvent oil.

[0014] Furthermore, in step S1, the method further comprises activating the extractant using dilute sulfuric acid.

[0015] Furthermore, when performing step S2, extraction is performed by countercurrent extraction;

[0016] Before countercurrent extraction, the pH of the mixed solution of the aqueous extraction phase and the organic extraction phase is adjusted to 11.5-13.5 using sodium hydroxide, and then the countercurrent extraction is performed;

[0017] Alternatively, before countercurrent extraction, the pH of the mixed solution of the aqueous extraction phase and the organic extraction phase is adjusted to 11.5-12.5, and then during the countercurrent extraction, the pH of the mixed solution of the aqueous extraction phase and the organic extraction phase is controlled to be 10-12.

[0018] Furthermore, when performing step S2, the extracted aqueous phase and the extracted organic phase are mixed in a volume ratio of 2:1-1:5; when performing countercurrent extraction, multi-stage countercurrent extraction is performed until the phase separation reaches equilibrium, and the time for single-stage countercurrent extraction is 2-10 minutes.

[0019] Furthermore, when performing step S3, the loaded organic phase is mixed with an acid having a concentration of 0.1-0.8N, the volume ratio of the loaded organic phase to the acid is 20:1-10:1, and then subjected to multi-stage washing until equilibrium is reached to complete the washing;

[0020] Alternatively, when performing step S3, the loaded organic phase is dissolved in water and subjected to multi-stage washing until equilibrium is reached.

[0021] Further, when performing step S4, the organic phase loaded after sodium washing is mixed with 2-6N acid, the volume ratio of the organic phase loaded after sodium washing to the acid solution is 20:1-1:1, and then multi-stage stripping is performed until equilibrium is reached to obtain the lithium-containing stripping solution;

[0022] Alternatively, when performing step S4, the loaded organic phase after sodium washing is mixed with water, the volume ratio of the loaded organic phase after sodium washing to water is 20:1-1:1, and then carbon dioxide is introduced, and multi-stage stripping is performed until equilibrium is reached to obtain the lithium-containing stripping solution, wherein the specific rate of carbon dioxide is (30-100) L carbon dioxide / (h·L loaded organic phase).

[0023] Furthermore, in step S4, while obtaining the lithium-containing stripping solution, a stripping organic phase is also obtained, and the stripping organic phase is used as an extraction organic phase in the extraction of step S2.

[0024] Furthermore, the amount of lithium in the lithium-containing stripping solution obtained in step S4 accounts for more than 90% of the amount of lithium in the solution after lithium precipitation in step S1.

[0025] The present invention also provides an extraction system for extracting lithium from a post-lithium precipitation liquid, comprising an extractant, a co-extractant, a phase stabilizer and a diluent, wherein the extractant is composed of a component A and a component B, wherein the component A is selected from one or a combination of dibenzoylmethane and calcium dibenzoylmethane, and the component B is selected from one or a combination of di(2-ethylhexyl) phosphate and 2-ethylhexyl phosphoric acid.

[0026] Furthermore, the co-extractant is selected from one or a combination of trioctyl phosphate and tributyl phosphate. The phase stabilizer is selected from one or a combination of n-octanol, n-hexanol and n-pentanol. The diluent is 260# or 200# solvent oil.

[0027] In summary, in the present invention, the extractant is selected as component A and component B, and the component A and component B are composed of the component A, the component A is selected from one or a combination of dibenzoylmethane and calcium dibenzoylmethane, and the component B is selected from one or a combination of di(2-ethylhexyl) phosphate and 2-ethylhexyl phosphoric acid. Since component A is an extractant containing β-diketones, it can extract lithium in the liquid after lithium precipitation better during extraction, but when dibenzoylmethane and calcium dibenzoylmethane are used as extractants, when there is excessive alkali or the lithium loading is too high, the extraction system is prone to the problem of three-phase slag. In order to strengthen the β-diketone to achieve the enol conversion and prevent the appearance of three-phase slag, the present invention introduces extractant B components P204 and P507 on the basis of component A. On the one hand, it can provide the proton conditions required for the enol conversion, and on the other hand, it can achieve the extraction of lithium to a certain extent and alleviate the appearance of three-phase slag.

[0028] Furthermore, in the present invention, the co-extractants trioctyl phosphate and tributyl phosphate (TBP) used are neutral phosphine ester co-extractants or neutral phosphine oxide co-extractants. Since the extractant composed of component A and component B is lower in cost than LIX54 and benzoyltrifluoroacetone, and the co-extractant is lower in cost than trioctylphosphine oxide and trialkylphosphine oxide, the cost of the entire extraction system will be significantly reduced.

[0029] Therefore, this method can extract lithium efficiently, at low cost and stably in alkaline post-lithium precipitation solution.

[0030] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites a preferred embodiment and describes it in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The figure shows a schematic flow chart of each step of the method for extracting lithium from a post-lithium precipitation solution in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in conjunction with the accompanying drawings and preferred embodiments.

[0033] The invention provides a method for extracting lithium from a post-lithium precipitation solution and an extraction system thereof. The method can extract lithium from an alkaline post-lithium precipitation solution efficiently, at low cost and stably.

[0034] Figure 1 The figure shows a schematic flow chart of each step of the method for extracting lithium from a post-lithium precipitation solution in an embodiment of the present invention. In an embodiment of the present invention, the method for extracting lithium from a post-lithium precipitation solution comprises the following steps:

[0035] S1: providing an aqueous extraction phase and an organic extraction phase, wherein the aqueous extraction phase is a post-lithium precipitation liquid, and the organic extraction phase comprises an extractant, a co-extractant, a phase stabilizer and a diluent, wherein the extractant is composed of a component A and a component B, wherein the component A is selected from one or a combination of dibenzoylmethane and calcium dibenzoylmethane, and the component B is selected from one or a combination of di(2-ethylhexyl) phosphate (P204) and 2-ethylhexyl phosphoric acid (P507).

[0036] Furthermore, in this embodiment, the co-extractant can be selected from one or a combination of trioctyl phosphate and tributyl phosphate (TBP).

[0037] The phase stabilizer can be selected from one or a combination of n-octanol, n-hexanol and n-pentanol.

[0038] The diluent can be 260# or 200# solvent oil.

[0039] Further, in the extractant, the concentration of component A is less than 0.8 mol / L, the concentration of component B is less than 0.3 mol / L, and the total concentration of component A and component B is 0.4-0.8 mol / L. For example, it can be 0.5 mol / L dibenzoylmethane + 0.1 mol / L P204, 0.4 mol / L dibenzoylmethane + 0.2 mol / L dibenzoylmethane calcium + 0.2 mol / L P507, etc.

[0040] The concentration of each component of the synergistic extractant is less than 1.2 mol / L. That is, when the synergistic extractant is composed of a single component, its concentration is less than 1.2 mol / L; when the synergistic extractant is composed of two components, the concentration of each component is less than 1.2 mol / L, but when the synergistic extractant is composed of multiple components, its total concentration is 0.6-1.2 mol / L. For example, it can be 1.2 mol / L tributyl phosphate, 0.1 mol / L trioctyl phosphate and 0.8 mol / L tributyl phosphate.

[0041] The concentration of each component of the phase stabilizer is less than 0.1 mol / L. That is, when the phase stabilizer is composed of a single component, its concentration is less than 0.1 mol / L; when the phase stabilizer is composed of multiple components, the concentration of each component is less than 0.1 mol / L. For example, it can be 0 mol / L n-octanol and 0.05 mol / L n-hexanol, 0.05 mol / L n-hexanol and 0.05 mol / L n-pentanol, 0.06 mol / L n-octanol and 0.02 mol / L n-pentanol.

[0042] Furthermore, in order to improve the extraction effect of the extractant, in step S1, the extractant can be activated with dilute sulfuric acid before the subsequent steps are performed.

[0043] During activation, the original extracted organic phase can be fully mixed with 3-5N sulfuric acid at a volume ratio of 6:1 to 12:1. The activation time is 6 to 10 minutes. After phase separation, the organic phase is taken for extraction.

[0044] S2: mixing the extracted aqueous phase and the extracted organic phase, and extracting to obtain a loaded organic phase and a raffinate;

[0045] Furthermore, the extraction can be performed by countercurrent extraction. When performing the countercurrent extraction, the pH of the aqueous phase can be adjusted to 11.5-13.5 using sodium hydroxide, and then the countercurrent extraction can be performed to increase the extraction rate of lithium.

[0046] In another embodiment, the pH of the aqueous extraction phase may be adjusted to 11.5-12.5, and then the pH of the mixed solution of the aqueous extraction phase and the organic extraction phase may be controlled to be 10-12 during 2-10 levels of countercurrent extraction to improve the extraction rate of lithium.

[0047] In this step, the aqueous extraction phase and the organic extraction phase may be mixed at a volume ratio of 2:1-1:5. When performing countercurrent extraction, multiple stages, such as 1-10 stages of countercurrent extraction, may be performed until the phase separation reaches equilibrium.

[0048] More specifically, the single-stage extraction time of the countercurrent extraction is 2-10 minutes, for example, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes. The single-stage extraction temperature is 20-60°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C.

[0049] S3: washing the loaded organic phase to wash away the sodium ions in the solution, so as to obtain sodium washing water and the loaded organic phase after sodium washing.

[0050] In this embodiment, the loaded organic phase can be mixed with an acid having a concentration of 0.1-0.8N (1N=0.5 mol / L hydrogen ion equivalent), wherein the volume ratio of the loaded organic phase to the acid is 20:1-10:1, and then washed in multiple stages, such as 1-4 stages, until equilibrium is reached to obtain sodium washing water and a loaded organic phase after sodium washing. The acid can be dilute sulfuric acid, dilute hydrochloric acid or dilute nitric acid.

[0051] In other embodiments, the loaded organic phase may be dissolved in water and subjected to multiple stages, such as 1-4 stages of washing, until equilibrium is reached to obtain sodium washing water and the loaded organic phase after sodium washing.

[0052] Furthermore, during washing, the single-stage washing time is 2-10 minutes, and the single-stage washing temperature is 20-60°C.

[0053] S4: stripping the loaded organic phase after sodium washing to obtain a lithium-containing stripping solution to complete lithium recovery.

[0054] In this embodiment, the organic phase loaded after sodium washing can be mixed with 2-6N acid, and the volume ratio of the organic phase loaded after sodium washing to the acid solution is 20:1-1:1, preferably 20:1-10:1. Then, multiple stages, such as 1-4 stages of stripping, are performed until equilibrium is reached to obtain a lithium-containing stripping solution. The type of acid can be dilute sulfuric acid, dilute hydrochloric acid or dilute nitric acid.

[0055] In other embodiments, the sodium-washed loaded organic phase can be mixed with water, and the volume ratio of the sodium-washed loaded organic phase to water is 20:1-1:1, preferably 5:1-1:1. Then, carbon dioxide is introduced, and multiple stages, such as 1-4 stages of stripping, are performed until equilibrium is reached to obtain a lithium-containing stripping solution. The specific rate of carbon dioxide is: (30-100) L carbon dioxide / (h·L loaded organic phase), that is, 30-100 L of carbon dioxide is introduced per liter of loaded organic phase per hour.

[0056] When carrying out multi-stage stripping, the time of single-stage stripping is 2-10min, for example, it can be 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min; the temperature of single-stage stripping is (20-60)℃, for example, it can be 20℃, 30℃, 40℃, 50℃, 60℃.

[0057] The lithium-containing stripping solution obtained above can be used to prepare lithium carbonate. The preparation of lithium carbonate from the lithium-containing stripping solution can be based on the existing technology and will not be described in detail here.

[0058] Furthermore, while obtaining the lithium-containing stripping solution, a stripping organic phase can also be obtained, and the stripping organic phase can be directly used as an extraction organic phase, that is, it can be directly combined with the extraction aqueous phase in step S2 to save costs.

[0059] Furthermore, when the method for extracting lithium from the post-lithium precipitation liquid provided by the present invention is used to extract lithium from the post-lithium precipitation liquid, the lithium extraction rate is greater than 90%. That is, the amount of lithium in the lithium-containing stripping solution obtained in step S4 accounts for more than 90% of the amount of lithium in the post-lithium precipitation liquid in step S1.

[0060] In this embodiment, when performing the extraction in step S2, since component A of the extractant is an extractant containing β-diketones, during the extraction, lithium and the co-extractant form a complex, which is extracted by the extractant containing component A, thereby selectively extracting lithium from the aqueous phase into the organic phase, and the reaction is shown in formula (1):

[0061] Li + +H(En)+T+OH-→Li·En·T+H2O (1)

[0062] Among them, En is the extractant and T is the synergistic extractant.

[0063] In the subsequent stripping process, H + Replace the Li in the complex, so that Li migrates from the organic phase to the aqueous phase. The reaction is shown in (2)

[0064] H ++Li·En·T→Li + +H(En)+T (2)

[0065] During the extraction process of β-diketone extractants, the diketone structure will first undergo an enol form change. During the extraction process, the hydroxyl group in the enol form coordinates with the metal ion to form a stable complex, that is, a six-membered chelate structure - H(En). According to Pearson's hard and soft acid-base theory, β-diketone extractants are generally hard bases and preferentially combine with hard acids. In contrast, Li + The Pearson hardness (35.1eV) is higher than that of Na + (21.1eV), so this type of extractant can form a more stable chelate with Li. Therefore, in the extraction system, lithium can be effectively separated from impurity elements such as sodium and potassium.

[0066] However, when dibenzoylmethane and calcium dibenzoylmethane are used as extractants, when there is excessive alkalinity or the lithium loading is too high, the extraction system is prone to the problem of three-phase slag, mainly because the solubility of the formed chelate Li·En·T is limited, the structure is destroyed and precipitation occurs (Formula (3)).

[0067] Li·En·T(aq)→Li·En(s)+T(aq) (3)

[0068] In order to strengthen the enol conversion of β-diketone and prevent the appearance of three-phase slag, the present invention introduces extractant B components P204 and P507 on the basis of component A. On the one hand, it can provide the proton conditions required for the enol conversion, and on the other hand, it can achieve the extraction of lithium to a certain extent and alleviate the appearance of three-phase slag. Possible reaction mechanisms are shown in formulas (4) and (5).

[0069] Li·En(s)+P(aq)→Li·En·P(aq) (4)

[0070] Li·En(s)+P(aq)→Li·P(aq)+En(q) (5)

[0071] Wherein, P represents P204 or P507.

[0072] Furthermore, in the present invention, the co-extractants trioctyl phosphate and tributyl phosphate (TBP) used are neutral phosphine ester co-extractants or neutral phosphine oxide co-extractants. Since the extractant composed of component A and component B is lower in cost than LIX54 and benzoyltrifluoroacetone, and the co-extractant is lower in cost than trioctylphosphine oxide and trialkylphosphine oxide, the cost of the entire extraction system will be significantly reduced.

[0073] Therefore, this method can extract lithium efficiently, at low cost and stably in alkaline post-lithium precipitation solution.

[0074] The present invention also provides an extraction system for extracting lithium from a post-lithium precipitation liquid. The extraction system comprises an extractant, a co-extractant, a phase stabilizer and a diluent. The extractant consists of a component A and a component B. The component A is selected from one or a combination of dibenzoylmethane and calcium dibenzoylmethane, and the component B is selected from one or a combination of two of di(2-ethylhexyl) phosphate (P204) and 2-ethylhexyl phosphoric acid (P507).

[0075] Further, the co-extractant can be selected from one or a combination of trioctyl phosphate and tributyl phosphate (TBP). The phase stabilizer can be selected from one or a combination of n-octanol, n-hexanol and n-pentanol. The diluent can be 260# or 200# solvent oil.

[0076] Further, in the extractant, the concentration of component A is less than 0.8 mol / L, the concentration of component B is less than 0.3 mol / L, and the total concentration of component A and component B is 0.4-0.8 mol / L. For example, it can be 0.5 mol / L dibenzoylmethane + 0.1 mol / L P204, 0.4 mol / L dibenzoylmethane + 0.2 mol / L dibenzoylmethane calcium + 0.2 mol / L P507, etc.

[0077] The concentration of each component of the synergistic extractant is less than 1.2 mol / L. That is, when the synergistic extractant is composed of a single component, its concentration is less than 1.2 mol / L; when the synergistic extractant is composed of two components, the concentration of each component is less than 1.2 mol / L, but when the synergistic extractant is composed of multiple components, its total concentration is 0.6-1.2 mol / L. For example, it can be 1.2 mol / L tributyl phosphate, 0.1 mol / L trioctyl phosphate and 0.8 mol / L tributyl phosphate.

[0078] The concentration of each component of the phase stabilizer is less than 0.1 mol / L. That is, when the phase stabilizer is composed of a single component, its concentration is less than 0.1 mol / L; when the phase stabilizer is composed of multiple components, the concentration of each component is less than 0.1 mol / L. For example, it can be 0 mol / L n-octanol and 0.05 mol / L n-hexanol, 0.05 mol / L n-hexanol and 0.05 mol / L n-pentanol, 0.06 mol / L n-octanol and 0.02 mol / L n-pentanol.

[0079] The following is a detailed description of the method for extracting lithium from a post-lithium precipitation solution provided by the present invention using a specific embodiment:

[0080] Example 1

[0081] (1) Tributyl phosphate, dibenzoylmethane, P204, and n-octanol were mixed to form a composite extractant, and 260# solvent oil was used as a diluent to form an extraction organic phase. The concentrations of tributyl phosphate, dibenzoylmethane, and P204 were controlled to be 1.0 mol / L, 0.40 mol / L, and 0.20 mol / L, respectively. The amount of n-octanol added was 0.05 mol / L. The organic phase was first activated with 4N dilute sulfuric acid, and the organic phase and sulfuric acid were fully mixed at a volume ratio of 10:1 and stirred for 8 minutes. After phase separation, the activated organic phase was obtained for the subsequent extraction process.

[0082] (2) Provide a lithium battery waste solution with a lithium concentration of 2.66 g / L and a sodium concentration of 85 g / L as the aqueous phase, and adjust the aqueous phase to pH = 13.5. At a temperature of 20°C, mix the organic phase and the aqueous phase and extract. The extraction time for each stage is 6 minutes, and the volume ratio of the organic phase to the aqueous phase is controlled to be 1.0:1. After three-stage countercurrent extraction by shaking the flask, separation is performed to obtain a loaded organic phase with a lithium concentration of 2.45 g / L and a sodium concentration of 2.50 g / L. The lithium extraction rate in this process is 99.9%;

[0083] (3) washing the loaded organic phase obtained in step (1) once with 0.8N sulfuric acid at room temperature and a phase ratio of 10:1 to obtain a sodium-washed loaded organic phase with a lithium concentration of 2.26 g / L and a sodium concentration of 0.13 g / L;

[0084] (4) The sodium-washed organic phase obtained in step (2) was stripped with 4N sulfuric acid at room temperature and a ratio of 10:1 for stripping for level 1. The Li concentration in the stripping solution was 20.64 g / L, the sodium concentration was 1.359 g / L, and except for Ca and Mg reaching (30-50) mg / L, the concentrations of other metal elements such as K, Co, Ni, Mn, Fe, etc. were all lower than 5 mg / L. In this process, the lithium stripping rate reached 95.5%.

[0085] Example 2

[0086] (1) Tributyl phosphate, dibenzoylmethane, dibenzoylmethane calcium, P507, and n-octanol were mixed to form a composite extractant, and 200# solvent oil was used as a diluent to form an extraction organic phase. The concentrations of tributyl phosphate, dibenzoylmethane, and dibenzoylmethane calcium were controlled to be 1.1 mol / L, 0.30 mol / L, and 0.15 mol / L, respectively. The amount of P507 added was 0.3 mol / L, and the amounts of n-octanol and n-pentanol added were 0.075 mol / L and 0.025 mol / L, respectively. The organic phase was first activated with 4N dilute sulfuric acid, and the organic phase and sulfuric acid were fully mixed at a volume ratio of 8:1 and stirred for 10 minutes. After phase separation, the activated organic phase was obtained for the subsequent extraction process.

[0087] (2) Under the conditions of pH = 13.0 and temperature of 30°C, a lithium battery waste lithium precipitation liquid with a lithium concentration of 2.227 g / L and a sodium concentration of 60.28 g / L is provided as the aqueous phase, and the aqueous phase is adjusted to pH = 13.0. Under the condition of a temperature of 30°C, the organic phase is mixed with the aqueous phase and extracted, wherein the volume ratio of the organic phase to the aqueous phase is controlled to be 1.0:1, the residence time in the mixing chamber is 6 minutes, and the residence time in the clarification chamber is 18 minutes. After three-stage countercurrent extraction in a multi-stage extraction tank, separation, and continuous operation, a loaded organic phase with a lithium concentration of 2.10 g / L and a sodium concentration of 0.426 g / L is obtained. The lithium extraction rate in this process is 96.7%;

[0088] (3) washing the loaded organic phase obtained in step (1) with 0.8N sulfuric acid for two times at a temperature of 30°C and a phase ratio of 15:1, and washing once in an extraction tank to obtain a sodium-washed loaded organic phase with a lithium concentration of 2.03 g / L and a sodium concentration of 0.06 g / L;

[0089] (4) The sodium-washed organic phase obtained in step (2) was stripped with 4N sulfuric acid at a temperature of 30°C and subjected to three-stage countercurrent stripping in an extraction tank at a ratio of 10:1. The Li concentration in the stripping solution was 20.08 g / L, the sodium concentration was 0.3990 g / L, and except for Ca and Mg, which reached 30 to 50 mg / L, the concentrations of other metal elements such as K, Co, Ni, Mn, Fe, etc. were all less than 5 mg / L. In this process, the lithium stripping rate reached 98.9%.

[0090] Example 3

[0091] (1) Tributyl phosphate, dibenzoylmethane, dibenzoylmethane calcium, P204, and n-octanol were mixed to form a composite extractant, and 260# solvent oil was used as a diluent to form an extraction organic phase. The concentrations of tributyl phosphate, dibenzoylmethane, and dibenzoylmethane calcium were controlled to be 1.0 mol / L, 0.10 mol / L, and 0.30 mol / L, respectively. The amount of P204 added was 0.2 mol / L, and the amounts of n-octanol and n-hexanol added were 0.05 mol / L, respectively. The organic phase was first activated with 4N dilute sulfuric acid, and the organic phase and sulfuric acid were fully mixed and stirred at a volume ratio of 8:1 for 1 hour. After phase separation, the activated organic phase was obtained for the subsequent extraction process.

[0092] (2) The initial pH of the solution after lithium precipitation is adjusted to about 11.5, the lithium concentration in the water phase is 2.267g / L and the sodium concentration is 40.05g / L, the solution after lithium precipitation of the lithium battery waste is extracted with the extracted organic phase at room temperature, the volume ratio of the organic phase to the aqueous phase is controlled to be 1.2:1, the residence time in the mixing chamber is 6min, the residence time in the clarification chamber is 18min, and the secondary countercurrent extraction is carried out in the multi-stage extraction tank and the equilibrium pH of the oil-water homogeneous phase in the secondary mixing chamber is controlled to be 11.5, and then separated and operated continuously to obtain a loaded organic phase with a lithium concentration of 1.920g / L and a sodium concentration of 0.0758g / L. The lithium extraction rate in this process is 98.3%;

[0093] (3) washing the loaded organic phase obtained in step (1) with pure water in countercurrent for 2 stages at a temperature of 30° C. and a phase ratio of 10:1 to obtain a sodium-washed loaded organic phase having a lithium concentration of 1.881 g / L and a sodium concentration of 0.0173 g / L;

[0094] (4) The sodium-washed organic phase obtained in step (2) was placed in a 50L reactor, pure water was added according to the ratio O / A=4:1 and stirred thoroughly, and carbon dioxide gas was used for stripping in the oil-water mixed homogeneous phase, the temperature was 30°C, the specific flow rate of carbon dioxide was 30L carbon dioxide / (h·L loaded organic phase), and the stripping solution was 6.284g / L in Li concentration, 0.0258g / L in sodium concentration, and the concentrations of other metal elements such as K, Ca, Mg, Co, Ni, Mn, Fe, etc. were all less than 5mg / L. In this process, the stripping rate of lithium reached 95.1%.

[0095] Example 4

[0096] (1) Tributyl phosphate, dibenzoylmethane calcium, dibenzoylmethane, and P204 were mixed to form a composite extractant, and 260# solvent oil was used as a diluent to form an extraction organic phase. The concentrations of tributyl phosphate, dibenzoylmethane, and dibenzoylmethane calcium were controlled to be 1.0 mol / L, 0.30 mol / L, and 0.1 mol / L, respectively, and the concentration of P204 was 0.3 mol / L. The organic phase was first activated with 4N dilute sulfuric acid, and the organic phase and sulfuric acid were fully mixed and stirred at a volume ratio of 8:1 for 1 hour. After phase separation, the activated organic phase was obtained for the subsequent extraction process.

[0097] (2) The initial pH of the solution after lithium precipitation is adjusted to about 12.0, the lithium concentration in the water phase is 1.377g / L and the sodium concentration is 33.47g / L, the solution after lithium precipitation of the lithium battery waste is extracted with the extracted organic phase at room temperature, the volume ratio of the organic phase to the aqueous phase is controlled to be 1.0:1.7, the residence time in the mixing chamber is 4min, the residence time in the clarification chamber is 22min, and the solution is subjected to secondary countercurrent extraction in a multi-stage extraction tank and the equilibrium pH of the oil-water homogeneous phase in the secondary mixing chamber is controlled to be 11.5, and then separated and operated continuously to obtain a loaded organic phase with a lithium concentration of 2.286g / L and a sodium concentration of 0.5313g / L. The lithium extraction rate in this process is 98.9%;

[0098] (3) The loaded organic phase obtained in step (1) was counter-washed with 0.2N dilute sulfuric acid for 2 stages at a temperature of 30° C. and a phase ratio of 10:1 to obtain a sodium-washed loaded organic phase having a lithium concentration of 2.312 g / L and a sodium concentration of 0.040 g / L;

[0099] (4) The sodium-washed organic phase obtained in step (2) was placed in a 50L reactor, pure water was added according to the ratio O / A=4:1 and stirred thoroughly, and carbon dioxide gas was used for stripping in the oil-water mixed homogeneous phase, the temperature was 30°C, the specific flow rate of carbon dioxide was 40L carbon dioxide / (h·L loaded organic phase), and the gas was ventilated for 40min. The Li concentration in the stripping solution was 8.598g / L, the sodium concentration was 0.1232g / L, and except for the Ca concentration reaching 0.0183g / L, the concentrations of other metal elements such as K, Mg, Co, Ni, Mn, Fe, etc. were all less than 5mg / L. In this process, the lithium stripping rate reached 96.9%.

[0100] Example 5

[0101] Compared with Example 1, in this case, the tributyl phosphate in step (1) is replaced by a mixture of tributyl phosphate and trioctyl phosphate, the concentrations of which are 0.9 mol / L and 0.1 mol / L, respectively. After the organic phase and the aqueous phase are shaken and mixed, the extraction rate is 90.3%.

[0102] Example 6

[0103] Compared with Example 1, in this case, the lithium concentration of the solution after lithium precipitation in step (1) is increased to 5.025 g / L, and the sodium concentration is 51.28 g / L, and the ratio is adjusted to 2.5:1. The equilibrium pH of the oil-water mixed phase is controlled to 11.3, and the extraction rate is 93.0%.

[0104] Example 7

[0105] Compared with Example (1), in this case, the extraction, washing and stripping time of the post-lithium precipitation liquid are adjusted to 2 minutes, the original solution concentration is 2.80 g / L, and after the organic phase and the aqueous phase are shaken and mixed, the extraction rate is 77.40%, and the stripping rate is 99.1%.

[0106] Example 8

[0107] Compared with Example (1), in this case, the extraction, washing and stripping time of the post-lithium precipitation liquid are adjusted to 10 minutes, the original solution concentration is 2.80 g / L, and after the organic phase and the aqueous phase are shaken and mixed, the extraction rate is 78.30%, and the stripping rate is 99.6%.

[0108] Example 9

[0109] Compared with Example (1), in this case, the temperature of the post-lithium precipitation liquid extraction, washing and stripping is adjusted to 50°C, the original solution concentration is 2.17 g / L, and after the organic phase and the aqueous phase are shaken and mixed, the extraction rate is 96.00% and the stripping rate is 99.3%.

[0110] Comparative Example 1

[0111] Compared with Example (1), in this case, the composite extractant formed by mixing tributyl phosphate, P204, dibenzoylmethane and n-octanol in the organic phase is replaced with tributyl phosphate or dibenzoylmethane or n-octanol or P204. The lithium extraction rate is lower than 20%, and severe emulsification occurs only when dibenzoylmethane is used, indicating that the extraction between the components of the organic phase is a synergistic extraction effect.

[0112] Comparative Example 2

[0113] Compared with Example (1), in this case, tributyl phosphate in step (1) is replaced by trioctylphosphine oxide, and its concentration is 0.8 mol / L. After the organic phase and the aqueous phase are shaken and mixed, the extraction rate is 64.3%. The effect is significantly reduced, and the cost of the synergistic extractant is several times higher than that of tributyl phosphate, which is not economical for industrial implementation.

[0114] Comparative Example 3

[0115] Compared with Example (1), in this case, the pH of the solution after lithium precipitation in step (1) was adjusted to 11.0. After the organic phase and the aqueous phase were shaken and mixed, the extraction was less than 30%. This shows that if the initial pH is too low, the direct extraction effect will be significantly reduced.

[0116] Comparative Example 4

[0117] Compared with Example (1), the pH of the solution after lithium precipitation in step (1) was adjusted to 13.6 in this case. As a result, after three-stage countercurrent extraction, obvious and large amounts of three-phase slag appeared. This shows that if the equilibrium pH is too high, it will be detrimental to the stability of the organic phase.

[0118] Comparative Example 5

[0119] Compared with Example (1), the extractant component B was not added in this case. After the organic phase and the aqueous phase were shaken and mixed, the extraction could only reach 90%, and a large amount of three-phase slag appeared. This shows that the addition of the extractant component B plays a very important role in increasing the lithium extraction capacity and stability of the system, so it is necessary to add component B.

[0120] Comparative Example 6

[0121] Compared with Example (1), in this case, the extractant component A is not added, and only component B, tributyl phosphate and n-octanol are used. After the organic phase and the aqueous phase are shaken and mixed, the lithium extraction can only reach 43%. This shows that the extractant component B has a certain extraction effect on lithium, but the effect is weaker than that of the extractant component A, so component A must also be added.

[0122] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for extracting lithium from a solution after lithium precipitation, characterized in that: The method comprises the following steps: S1: providing an aqueous extraction phase and an organic extraction phase, wherein the aqueous extraction phase is a post-lithium precipitation solution, and the organic extraction phase comprises an extractant, a co-extractant, a phase stabilizer and a diluent, wherein the extractant is composed of a component A and a component B, wherein the component A is selected from one or a combination of dibenzoylmethane and calcium dibenzoylmethane, and the component B is selected from one or a combination of di(2-ethylhexyl) phosphate and 2-ethylhexyl phosphoric acid; S2: mixing the extracted aqueous phase and the extracted organic phase, and extracting to obtain a loaded organic phase and a raffinate; S3: washing the loaded organic phase to wash away the sodium ions in the solution to obtain sodium washing water and a sodium-washed loaded organic phase; S4: stripping the loaded organic phase after sodium washing to obtain a lithium-containing stripping solution.

2. The method for extracting lithium from a post-lithium precipitation solution according to claim 1, characterized in that: In the extractant, the concentration of the component A is less than 0.8 mol / L, the concentration of the component B is less than 0.3 mol / L, and the total concentration of the component A and the component B is 0.4-0.8 mol / L.

3. The method for extracting lithium from a post-lithium precipitation solution according to claim 1, characterized in that: The co-extractant is selected from one or a combination of trioctyl phosphate and tributyl phosphate.

4. The method for extracting lithium from a post-lithium precipitation solution according to claim 1, characterized in that: The phase stabilizer is selected from one or a combination of n-octanol, n-hexanol and n-pentanol, and the diluent is selected from 260# or 200# solvent oil.

5. The method for extracting lithium from a post-lithium precipitation solution according to claim 1, characterized in that: When performing step S2, extraction is performed by countercurrent extraction; Before performing the countercurrent extraction, the pH of the aqueous extraction phase is adjusted to 11.5-13.5 using sodium hydroxide, and then the countercurrent extraction is performed; Alternatively, before countercurrent extraction, the pH of the aqueous extraction phase is adjusted to 11.5-12.5, and then during the countercurrent extraction, the pH of the mixed solution of the aqueous extraction phase and the organic extraction phase in the second stage and thereafter is controlled to be 10-12.

6. The method for extracting lithium from a post-lithium precipitation solution according to claim 5, characterized in that: When performing step S2, the aqueous extraction phase and the organic extraction phase are mixed at a volume ratio of 2:1-1:5; when performing countercurrent extraction, multi-stage countercurrent extraction is performed until the phase separation reaches equilibrium, and the time for single-stage countercurrent extraction is 2-10 minutes.

7. The method for extracting lithium from a post-lithium precipitation solution according to claim 1, characterized in that: When performing step S3, the loaded organic phase is mixed with an acid having a concentration of 0.1-0.8N, the volume ratio of the loaded organic phase to the acid being 20:1-10:1, and then subjected to multi-stage washing until equilibrium is reached to complete the washing; Alternatively, when performing step S3, the loaded organic phase is dissolved in water and subjected to multi-stage washing until equilibrium is reached.

8. The method for extracting lithium from a post-lithium precipitation solution according to claim 1, characterized in that: When performing step S4, the organic phase loaded after sodium washing is mixed with 2-6N acid, the volume ratio of the organic phase loaded after sodium washing to the acid solution is 20:1-1:1, and then multi-stage stripping is performed until equilibrium is reached to obtain the lithium-containing stripping solution; Alternatively, when performing step S4, the loaded organic phase after sodium washing is mixed with water, the volume ratio of the loaded organic phase after sodium washing to water is 20:1-1:1, and then carbon dioxide is introduced, and multi-stage stripping is performed until equilibrium is reached to obtain the lithium-containing stripping solution, wherein the specific rate of carbon dioxide is (30-100) L carbon dioxide / (h·L loaded organic phase).

9. The method for extracting lithium from a post-lithium precipitation solution according to claim 1, characterized in that: The amount of lithium in the lithium-containing stripping solution obtained in step S4 accounts for more than 90% of the amount of lithium in the solution after lithium precipitation in step S1.

10. An extraction system for extracting lithium from a post-lithium precipitation solution, characterized in that: The invention comprises an extractant, a co-extractant, a phase stabilizer and a diluent. The extractant consists of a component A and a component B. The component A is selected from one or a combination of dibenzoylmethane and calcium dibenzoylmethane, and the component B is selected from one or a combination of di(2-ethylhexyl) phosphate and 2-ethylhexyl phosphoric acid.

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