LITHIUM EXTRACTION AGENT FOR LITHIUM PRECIPITATION MOTHER LIQUOR AND EXTRACTION METHOD THEREOF

[0001] This application claims priority to Chinese Patent Application No. 202411587036.4, filed on Nov. 8, 2024, the content of which is incorporated herein by reference in its entirety.

[0002] The present application relates to the field of extraction and separation technology, and in particular, to a lithium extraction agent for lithium precipitation mother liquor and an extraction method thereof.

[0003] Lithium occupies a pivotal position in the fields of new energy and modern industry. Currently, most secondary resources, such as lithium ore or waste lithium batteries, adopt hydrometallurgical recovery processes. The lithium precipitation mother liquor is an alkaline solution with high sodium and low lithium content produced after carbonate precipitation, which still contains about 2 g/L of lithium, and is a typical low-concentration lithium-containing solution, and still has a certain economic value. Currently, the main methods for recovering residual lithium from lithium precipitation mother liquor include crystallization, electrodialysis, resin adsorption, etc. However, these methods have drawbacks such as long separation processes and high costs.

[0004] The extraction method has the advantages of high separation efficiency and strong continuity, and has been extensively reported in fields such as lithium extraction from salt lakes and lithium recovery from lithium precipitation mother liquor. Most of them use traditional extraction agents such as tributyl phosphate and β-diketones, which have disadvantages of strong water solubility and high price, and require multiple-stage processes such as extraction, washing, and stripping, resulting in large equipment investment and high operating costs.

[0005] Embodiments of the present application provide a lithium extraction agent for lithium precipitation mother liquor and an extraction method thereof, which can solve the problem of the complex extraction process for separating lithium from the lithium precipitation mother liquor by an extraction method.

[0006] In a first aspect, the present application provides a lithium extraction agent for lithium precipitation mother liquor, for use in extracting lithium from the lithium precipitation mother liquor, the lithium extraction agent comprising a solute and an organic solvent, the solute comprising at least one of 2,3,7,8-tetraaminophenazine-1,4,6,9-tetrone and terpyridine, and the organic solvent comprising at least one of dichloromethane, chloroform, carbon tetrachloride, bromobenzene, and carbon disulfide.

[0007] In a second aspect, the present application provides a lithium extraction method for lithium precipitation mother liquor, comprising:

• • [0008] providing the lithium extraction agent as described above, and providing the lithium precipitation mother liquor, mixing the lithium extraction agent with the lithium precipitation mother liquor, and performing an extraction treatment to obtain mixture A;
  • [0009] leaving the mixture A to stand for phase separation, and taking the lower oil phase to obtain an extracted organic phase containing lithium-containing insoluble substances;
  • [0010] filtering the extracted organic phase to obtain a lithium-containing solid complex.

[0011] In some embodiments, the extraction temperature for the extraction treatment is Tm, and 20° C.≤Tm≤50° C.; preferably, 30° C.≤Tm≤50° C.

[0012] In some embodiments, the time for the extraction treatment is tm, and 10 min≤tm≤30 min; preferably, 20 min≤tm≤30 min.

[0013] In some embodiments, the concentration of lithium ions in the lithium precipitation mother liquor is A, and 2.13 g/L≤A≤2.65 g/L; the concentration of sodium ions in the lithium precipitation mother liquor is B, 48.25 g/L≤B≤51.32 g/L.

[0014] In some embodiments, the pH of the lithium precipitation mother liquor satisfies: 9≤pH≤14.

[0015] In some embodiments, providing the lithium extraction agent comprises: dissolving the solute as a solid in the organic solvent until saturation to form the homogeneous lithium extraction agent;

[0016] wherein the dissolution temperature for dissolving the solute in the organic solvent is TO, the extraction temperature for the extraction treatment is Tm, and T0=Tm.

[0017] In some embodiments, filtering the extracted organic phase further comprises: obtaining an organic phase;

[0018] providing the lithium extraction agent comprises: recycling the organic phase as the organic solvent for dissolving the solute to prepare a new lithium extraction agent.

[0019] In some embodiments, the extraction treatment comprises: the volume ratio of the lithium extraction agent to the lithium precipitation mother liquor is C, and C ranges from 1:3 to 3:1.

[0020] Based on the lithium extraction agent for lithium precipitation mother liquor and the extraction method thereof according to the embodiments of the present application, the lithium extraction agent can be used to extract lithium from the lithium precipitation mother liquor with a wide pH range. After entering the lithium extraction agent, lithium ions quickly complex with the solute in the lithium extraction agent to form a solid phase. It only requires leaving the extracted mixture A to stand for phase separation, allowing lithium to exist in a lithium-containing solid complex in the lower oil phase, and filtering the lower oil phase to obtain the lithium-containing solid complex, and the lithium-containing solid complex has a low sodium residue content. The extraction method of the present application can omit post-processes such as washing and stripping in traditional extraction processes, greatly shortening the extraction process flow and saving production costs.

[0024] In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not intended to limit the present application.

[0025] An embodiment of the present application provides a lithium extraction agent for lithium precipitation mother liquor, the lithium extraction agent comprising a solute and an organic solvent, the solute comprising at least one of 2,3,7,8-tetraaminophenazine-1,4,6,9-tetrone (TAPT) and terpyridine, and the organic solvent comprising at least one of dichloromethane, chloroform, carbon tetrachloride, bromobenzene, and carbon disulfide.

[0026] When used to extract lithium from the lithium precipitation mother liquor, the lithium extraction agent according to the embodiment of the present application can be used to extract lithium from the lithium precipitation mother liquor with a wide pH range. After entering the lithium extraction agent, lithium ions quickly complex with the solute in the lithium extraction agent to form a solid phase (i.e., a lithium-containing solid complex). In addition, the organic solvent selected in the present application not only can dissolve the solute well, but also has a relatively high specific gravity. It only requires leaving the extracted mixture A to stand for phase separation to separate an oil phase (i.e., an extracted organic phase) and an aqueous phase. The aqueous phase is in the upper layer, and the oil phase is in the lower layer. Lithium exists in the lithium-containing solid complex in the lower oil phase, and sodium exists in the upper aqueous phase. The lithium-containing solid complex can be obtained by taking the lower oil phase and filtering it, and the lithium-containing solid complex has a low sodium residue content. The extraction method of the present application can omit post-processes such as washing and stripping in traditional extraction processes, greatly shortening the extraction process flow and saving production costs. Here, the organic phase obtained by filtering the lower oil phase can be recycled as the organic solvent for dissolving the solute again to prepare a new lithium extraction agent.

[0027] As shown in FIG. 1 and FIG. 2, an embodiment of the present application further provides a lithium extraction method for lithium precipitation mother liquor, comprising:

• • [0028] Step S100: providing the lithium extraction agent as described above, and providing the lithium precipitation mother liquor, mixing the lithium extraction agent with the lithium precipitation mother liquor, and performing an extraction treatment to obtain mixture A;
  • [0029] Step S200: leaving the mixture A to stand for phase separation, and taking the lower oil phase to obtain an extracted organic phase containing lithium-containing insoluble substances; and
  • [0030] Step S300: filtering the extracted organic phase to obtain a lithium-containing solid complex.

[0031] By using the lithium extraction agent as described above, the lithium extraction method for lithium precipitation mother liquor according to the embodiment of the present application can extract lithium from the lithium precipitation mother liquor with a wide pH range. The extracted lithium exists in the lithium-containing solid complex in a solid form, realizing lithium-sodium separation. After the extraction is completed, there is no need for traditional extraction processes such as washing and stripping. Only filtration of the extracted organic phase is required to obtain the lithium-containing solid complex and an organic phase. The organic phase can be regenerated for preparing a new lithium extraction agent. The lithium extraction process is simple, greatly shortens the extraction process flow, and saves production costs.

[0032] In some embodiments, providing the organic phase comprises: dissolving the solute as a solid in the organic solvent until saturation to form the homogeneous organic phase. The solute in a saturated state can enable more sufficient contact between lithium and the solute, thereby improving the lithium extraction rate.

[0033] Here, the dissolution temperature for dissolving the solute in the organic solvent is TO, the extraction temperature for the extraction treatment is Tm, and T0=Tm. Thus, during the extraction process, the stability of the solute and the organic solvent in the lithium extraction agent can be maintained.

[0034] In some embodiments, filtering the mixture A further comprises: obtaining an organic phase. Providing the lithium extraction agent comprises: using the organic phase as the organic solvent for dissolving the solute, so that all substances obtained after the extraction treatment can be utilized, with no waste discharge, thereby saving resources.

[0035] In some embodiments, the extraction temperature for the extraction treatment is Tm, and 20° C.≤Tm≤50° C. For example, Tm may be 20° C., 25° C., 30° C., 40° C., 45° C., 50° C., or any range between any two of the above. In the above temperature range, the stability of the solute and the organic solvent in the lithium extraction agent can be maintained, and the solute can more sufficiently complex with lithium to form a complex.

[0036] In some embodiments, the time for the extraction treatment is tm, and 10 min≤tm≤30 min. For example, tm may be 10 min, 15 min, 20 min, 25 min, 30 min, or any range between any two of the above. In this temperature range, lithium can make more sufficient contact with the solute, thereby improving the lithium extraction rate.

[0037] In some embodiments, during the extraction treatment process, stirring can be used to accelerate lithium into the solute and increase the efficiency of complex formation between the solute and lithium. Here, stirring can be carried out in a magnetic stirrer. The stirring speed for the extraction treatment is P, and 80 rpm≤P≤120 rpm. For example, P may be 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm, or any range between any two of the above.

[0038] In some embodiments, the concentration of lithium ions in the lithium precipitation mother liquor is A, and 2.13 g/L≤A≤2.65 g/L. For example, A may be 2.13 g/L, 2.25 g/L, 2.38 g/L, 2.46 g/L, 2.55 g/L, 2.65 g/L, or any range between any two of the above.

[0039] In some embodiments, the concentration of sodium ions in the lithium precipitation mother liquor is B, and 48.25 g/L≤B≤51.32 g/L. For example, B may be 48.25 g/L, 49.30 g/L, 49.88 g/L, 50.21 g/L, 50.80 g/L, 51.32 g/L, or any range between any two of the above.

[0040] In some embodiments, the pH of the lithium precipitation mother liquor satisfies: 9≤pH≤14. For example, the pH may be 9, 10, 11, 12, 13, 14, or any range between any two of the above. In the above pH range, the solute and the organic solvent in the lithium extraction agent can still maintain a relatively stable state, enabling the solute to sufficiently complex with lithium.

[0041] In some embodiments, the extraction treatment comprises: the volume ratio of the lithium extraction agent to the lithium precipitation mother liquor is C, and C ranges from 1:3 to 3:1. For example, C may be 1:3, 2:3, 3:3, 3:2, 3:1, or any range between any two of the above. By selecting the volume ratio C of the lithium extraction agent to the lithium precipitation mother liquor within the above range, the lithium extraction agent can more fully extract lithium from the lithium precipitation mother liquor.

[0042] In order to more intuitively understand the lithium extraction effect of the lithium extraction method for lithium precipitation mother liquor according to the embodiment of the present application, the lithium extraction method for lithium precipitation mother liquor of the present application will be further described below through examples.

[0043] For the lithium precipitation mother liquor selected in each of the following examples, the concentration A of lithium ions in the lithium precipitation mother liquor was measured to be 2.65 g/L, and the concentration B of sodium ions was measured to be 51.32 g/L, using ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer).

[0044] TAPT was selected as the solute and dichloromethane as the organic solvent. TAPT was dissolved in dichloromethane at a temperature of 35° C. until saturation to obtain the lithium extraction agent.

[0045] The lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 1:1. The pH of the lithium precipitation mother liquor was adjusted to 11 using a sodium hydroxide solution. The lithium precipitation mother liquor was added to the lithium extraction agent and extracted at a stirring speed of 120 rpm and a temperature of 35° C. for 20 min to obtain mixture A.

[0046] (3) The mixture A was left to stand for phase separation to separate the upper aqueous phase and the lower oil phase. The lower oil phase was taken to obtain an extracted organic phase containing lithium-containing insoluble substances.

[0047] (4) The extracted organic phase containing lithium-containing insoluble substances was filtered to separate the insoluble substances and an organic phase. The insoluble substances were taken to obtain a lithium-containing solid complex.

[0048] Here, the concentration of lithium ions in the upper aqueous phase was measured as m1, and the concentration of sodium ions was measured as m2.

[0049] Lithium extraction rate=m1/A*100%; Sodium extraction rate=m2/B*100%.

[0050] The difference from Example 1 is: chloroform was selected as the organic solvent.

[0051] The difference from Example 1 is: tetrachloromethane was selected as the organic solvent.

[0052] The difference from Example 1 is: bromobenzene was selected as the organic solvent.

[0053] The difference from Example 1 is: carbon disulfide was selected as the organic solvent.

[0054] The difference from Example 1 is: terpyridine was selected as the solute.

[0055] The difference from Example 6 is: chloroform was selected as the organic solvent.

[0056] The difference from Example 6 is: tetrachloromethane was selected as the organic solvent.

[0057] The difference from Example 6 is: bromobenzene was selected as the organic solvent.

[0058] The difference from Example 6 is: carbon disulfide was selected as the organic solvent.

[0059] The difference from Example 2 is:

[0060] (1) In the preparation of the lithium extraction agent, TAPT was dissolved in chloroform at a temperature of 20° C. until saturation.

[0061] (2) In the extraction treatment, the lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 3:1, the pH of the lithium precipitation mother liquor was adjusted to 9, and the extraction was carried out at a temperature of 20° C. for 20 min to obtain the mixture.

[0062] The difference from Example 11 is:

[0063] (2) In the extraction treatment, the lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 1:3, the pH of the lithium precipitation mother liquor was adjusted to 13, and the extraction was carried out at a temperature of 20° C. for 30 min to obtain the mixture.

[0064] The difference from Example 11 is:

[0065] (2) In the extraction treatment, the pH of the lithium precipitation mother liquor was adjusted to 14, and the extraction was carried out at a temperature of 20° C. for 30 min to obtain the mixture.

[0066] The difference from Example 2 is:

[0067] (1) In the preparation of the lithium extraction agent, TAPT was dissolved in chloroform at a temperature of 50° C. until saturation.

[0068] (2) In the extraction treatment, the lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 3:1, the pH of the lithium precipitation mother liquor was adjusted to 9, and the extraction was carried out at a temperature of 50° C. for 20 min to obtain the mixture.

[0069] The difference from Example 14 is:

[0070] (2) In the extraction treatment, the lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 1:3, the pH of the lithium precipitation mother liquor was adjusted to 13, and the extraction was carried out at a temperature of 50° C. for 30 min to obtain the mixture.

[0071] The difference from Example 14 is:

[0072] (2) In the extraction treatment, the pH of the lithium precipitation mother liquor was adjusted to 14, and the extraction was carried out at a temperature of 50° C. for 30 min to obtain the mixture.

[0073] The difference from Example 8 is:

[0074] (1) In the preparation of the lithium extraction agent, terpyridine was dissolved in carbon tetrachloride at a temperature of 20° C. until saturation.

[0075] (2) In the extraction treatment, the lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 3:1, the pH of the lithium precipitation mother liquor was adjusted to 9, and the extraction was carried out at a temperature of 20° C. for 20 min to obtain the mixture.

[0076] The difference from Example 17 is:

[0077] (2) In the extraction treatment, the lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 1:3, the pH of the lithium precipitation mother liquor was adjusted to 13, and the extraction was carried out at a temperature of 20° C. for 30 min to obtain the mixture.

[0078] The difference from Example 17 is:

[0079] (2) In the extraction treatment, the pH of the lithium precipitation mother liquor was adjusted to 14, and the extraction was carried out at a temperature of 20° C. for 30 min to obtain the mixture.

[0080] The difference from Example 8 is:

[0081] (1) In the preparation of the lithium extraction agent, terpyridine was dissolved in carbon tetrachloride at a temperature of 50° C. until saturation.

[0082] (2) In the extraction treatment, the lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 3:1, the pH of the lithium precipitation mother liquor was adjusted to 9, and the extraction was carried out at a temperature of 50° C. for 20 min to obtain the mixture.

[0083] The difference from Example 20 is:

[0084] (2) In the extraction treatment, the lithium extraction agent and lithium precipitation mother liquor were taken at a volume ratio of 3:1, the pH of the lithium precipitation mother liquor was adjusted to 13, and the extraction was carried out at a temperature of 50° C. for 30 min to obtain the mixture.

[0085] The difference from Example 20 is:

[0086] (2) In the extraction treatment, the pH of the lithium precipitation mother liquor was adjusted to 14, and the extraction was carried out at a temperature of 50° C. for 30 min to obtain the mixture.

[0087] The respective test parameters and experimental results of Examples 1 to 22 are shown in Table 1.

	TABLE 1
			Extraction
			temperature
			Tm and
			preparation
			temperature
			T0 of lithium	Extraction	Extraction	pH of	Lithium	Sodium
	Type of	Type of organic	extraction	oil-water	time	aqueous	extraction	extraction
	solute	solvent	agent/° C.	ratio C	tm/min	phase	rate/%	rate/%
Example 1	TAPT	dichloromethane	35	1:1	20	11	65.32	0.12
Example 2	TAPT	chloroform	35	1:1	20	11	68.24	0.08
Example 3	TAPT	carbon	35	1:1	20	11	65.78	0.14
		tetrachloride
Example 4	TAPT	bromobenzene	35	1:1	20	11	64.89	0.03
Example 5	TAPT	carbon disulfide	35	1:1	20	11	66.35	0.14
Example 6	terpyridine	dichloromethane	35	1:1	20	11	59.36	0.09
Example 7	terpyridine	chloroform	35	1:1	20	11	57.22	0.12
Example 8	terpyridine	carbon	35	1:1	20	11	61.24	0.15
		tetrachloride
Example 9	terpyridine	bromobenzene	35	1:1	20	11	60.01	0.07
Example 10	terpyridine	carbon disulfide	35	1:1	20	11	58.68	0.03
Example 11	TAPT	chloroform	20	3:1	20	9	82.14	0.18
Example 12	TAPT	chloroform	20	1:3	30	13	33.35	0.04
Example 13	TAPT	chloroform	20	3:1	30	14	86.35	0.12
Example 14	TAPT	chloroform	50	3:1	20	9	85.41	0.17
Example 15	TAPT	chloroform	50	1:3	30	13	33.32	0.11
Example 16	TAPT	chloroform	50	3:1	30	14	91.47	0.14
Example 17	terpyridine	carbon	20	3:1	20	9	77.24	0.08
		tetrachloride
Example 18	terpyridine	carbon	20	1:3	30	13	22.45	0 11
		tetrachloride
Example 19	terpyridine	carbon	20	3:1	30	14	81.24	0.07
		tetrachloride
Example 20	terpyridine	carbon	50	3:1	20	9	78.56	0.05
		tetrachloride
Example 21	terpyridine	carbon	50	1:3	30	13	24.32	0.14
		tetrachloride
Example 22	terpyridine	carbon	50	3:1	30	14	88.09	0.13
		tetrachloride

[0088] It can be seen from Examples 1 to 10 in Table 1 that when the solute in the lithium extraction agent is selected from at least one of 2,3,7,8-tetraaminophenazine-1,4,6,9-tetrone (TAPT) and terpyridine, and the organic solvent is selected from at least one of dichloromethane, chloroform, carbon tetrachloride, bromobenzene, and carbon disulfide, a good lithium extraction rate can be achieved with a low sodium extraction rate, indicating that the lithium extraction method for lithium precipitation mother liquor according to the embodiment of the present application can effectively separate lithium and sodium in the lithium precipitation mother liquor.

[0089] It can be seen from Examples 11 and 13, Examples 14 and 16, Examples 17 and 19, and Examples 20 and 22 that the higher the pH of the lithium precipitation mother liquor and the longer the extraction time, the higher the lithium extraction rate.

[0090] It can be seen from Examples 11 to 13, Examples 14 to 16, Examples 17 to 19, and Examples 20 to 22 that the higher the volume ratio of the lithium extraction agent to the lithium precipitation mother liquor, the higher the lithium extraction rate; and the higher the extraction temperature Tm for the extraction treatment, the higher the lithium extraction rate.

[0091] In the drawings of the embodiments, the same or similar reference numerals correspond to the same or similar components; in the description of the present application, it should be understood that if there are terms such as “upper”, “lower”, “left”, and “right” indicating orientation or positional relationships, which are based on the orientation or positional relationships shown in the drawings, they are only for facilitating the description of the present application and simplifying the description, rather than indicating or implying that the referred device or element must have the specific orientation, or be constructed and operated in the specific orientation. Therefore, the terms describing positional relationships in the drawings are only for exemplary illustration and should not be construed as limitations to this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0092] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc., made within the spirit and principles of the present application shall be included in the scope of the present application.