Resource utilization method and device for lithium-containing mother liquor

Abstract

The present application provides a resource utilization method and device for a lithium-containing mother liquor. The resource utilization method for a lithium-containing mother liquor comprises the following steps: providing a lithium-containing mother liquor containing lithium ions and sulfate ions; mixing the lithium-containing mother liquor with a phosphate solution and then carrying out lithium precipitation treatment to obtain a lithium-containing slurry; carrying out solid-liquid separation treatment on the lithium-containing slurry to obtain a adsorption-feed liquor and a first solid material; using a titanium-based adsorbent to adsorb lithium ions from the adsorption-feed liquor to obtain an adsorption tail liquor; and carrying out concentration and crystallization treatment on the adsorption tail liquor, wherein a molar ratio of lithium ions in the lithium-containing mother liquor to phosphate ions in the phosphate solution is 3:(0.7-0.8). The resource utilization method for a lithium-containing mother liquor can improve the lithium recovery rate and the purity of the recovered product.

Description

Resource utilization methods and devices for lithium-containing mother liquor Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and specifically to a method and system for the resource utilization of lithium-containing mother liquor. Background Technology

[0002] Lithium precipitate mother liquor is a lithium-containing mother liquor formed after lithium salt extraction from lithium ore or derived from spent lithium iron phosphate batteries. It contains not only a certain amount of lithium ions but also a large number of impurities, such as carbonate ions, sulfate ions, aluminum ions, calcium ions, and sodium ions. The lithium content in the lithium precipitate mother liquor accounts for more than 20% of the total lithium extraction material flow, therefore, it is necessary to recover lithium ions from the lithium precipitate mother liquor.

[0003] Some traditional technologies propose using adsorbents to recover lithium ions from lithium precipitation mother liquor. However, the lithium adsorption rate of this extraction method is typically only 85%–90%. Furthermore, the adsorbent gradually depletes during use, resulting in high costs and requiring large adsorption equipment. Other traditional technologies propose adding solid phosphate to the lithium precipitation mother liquor to generate lithium phosphate precipitate for lithium ion recovery. This extraction method requires adding excessive amounts of phosphate to recover a significant amount of lithium, and the lithium element recovery rate is only 70%–80%. The resulting lithium phosphate precipitate contains a high impurity content, and the low concentration of lithium in the remaining liquid is difficult to further recover.

[0004] Based on the above, further research is still needed to provide a method and apparatus for the resource utilization of lithium-containing mother liquor. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a method and device for resource utilization of lithium-containing mother liquor, which is beneficial to improve the lithium element recovery rate and the purity of the recovered product.

[0006] The embodiments of this application provide a method for the resource utilization of lithium-containing mother liquor, which includes the following steps:

[0007] Provide lithium-containing mother liquor containing lithium ions and sulfate ions;

[0008] The lithium-containing mother liquor was mixed with a phosphate solution and then subjected to lithium precipitation treatment to obtain a lithium-containing slurry.

[0009] The lithium-containing slurry is subjected to solid-liquid separation treatment to obtain pre-adsorption liquid and first solid material;

[0010] Lithium ions in the pre-adsorption liquid are adsorbed using an adsorbent to obtain an adsorption tail liquid; and,

[0011] The adsorption tail liquid is concentrated and crystallized to obtain a second solid material;

[0012] The molar ratio of lithium ions in the lithium-containing mother liquor to phosphate ions in the phosphate solution is 3:(0.7-0.8).

[0013] In this method for the resource utilization of lithium-containing mother liquor, the lithium-containing mother liquor is first mixed with a phosphate solution. During mixing, the feeding ratio of lithium ions to phosphate ions is controlled at 3:(0.7-0.8). This feeding ratio results in a lower amount of phosphate ions, which is beneficial for improving peritectic effects and increasing the purity of lithium phosphate in the first solid material while precipitating a large amount of lithium ions. Furthermore, the lithium precipitation process consumes most of the lithium ions in the lithium-containing mother liquor, thereby effectively alleviating the problem of alkalinity reduction during subsequent adsorption processes and significantly improving the adsorption capacity of the adsorbent for lithium ions. After the above-mentioned lithium precipitation process and lithium ion adsorption, more than 99% of the lithium ions in the lithium-containing mother liquor are recovered, and there are few impurities remaining in the adsorption tail liquid. The sulfate material obtained by the concentration and crystallization treatment of the adsorption tail liquid has high purity.

[0014] In some embodiments of this application, the lithium-containing mother liquor is added to the phosphate solution during the mixing process of the lithium-containing mother liquor and the phosphate solution.

[0015] In this embodiment, the reverse feeding method of adding lithium-containing mother liquor to phosphate solution helps to effectively avoid peritectic problems and promotes more complete precipitation of lithium ions, thereby further improving the purity of lithium phosphate and the recovery rate of lithium ions in the first solid material.

[0016] In some embodiments of this application, the lithium-containing mother liquor is added to the phosphate solution within 0.5h to 4h.

[0017] In this embodiment, the lithium-containing mother liquor is added to the phosphate solution within 0.5h to 4h, which is beneficial for the full crystallization and growth of lithium phosphate and improves the purity of lithium phosphate in the obtained first solid material.

[0018] In some embodiments of this application, the phosphate in the phosphate solution includes one or more of sodium dihydrogen phosphate and disodium hydrogen phosphate.

[0019] In this embodiment, sodium dihydrogen phosphate and disodium hydrogen phosphate have high solubility. Using sodium dihydrogen phosphate and disodium hydrogen phosphate as solutes in the phosphate solution helps to reduce the required volume of the phosphate solution, reduce the dilution of lithium ions during the feeding process, and facilitate the full precipitation of lithium ions. In addition, sodium dihydrogen phosphate and disodium hydrogen phosphate can also generate hydrogen ions, which helps to adjust the pH value after the lithium precipitation reaction to a suitable range, reducing or avoiding the use of additional acid-base regulators.

[0020] In some embodiments of this application, the phosphate solution is a saturated solution of phosphate ions.

[0021] In this embodiment, compared to an unsaturated solution, using a saturated solution of phosphate ions as the phosphate salt allows lithium ions to combine and precipitate more quickly and fully with phosphate ions, which is beneficial for obtaining a higher lithium ion recovery rate and resource utilization efficiency.

[0022] In some embodiments of this application, after the solid-liquid separation process, the first solid material is further washed with a washing liquid.

[0023] In some embodiments of this application, the lithium-containing mother liquor is heated to 80°C to 100°C before mixing with the phosphate solution; and / or,

[0024] The temperature for lithium deposition treatment is 80℃~100℃, and the holding time for lithium deposition treatment is 2h~4h.

[0025] In this embodiment, heating the lithium-containing mother liquor to 80℃~100℃ and controlling the lithium precipitation treatment temperature at 80℃~100℃ is beneficial for the rapid and sufficient formation of precipitates between lithium ions and phosphate ions in the lithium-containing mother liquor, which improves the efficiency of resource utilization and the recovery rate of lithium ions. Controlling the holding time to within 2h~4h is beneficial for the full crystallization and crystal growth of lithium phosphate, which further improves the purity of lithium phosphate in the resulting first solid material.

[0026] In some embodiments of this application, the pH value of the pre-adsorption liquid is 9.5 to 10.5.

[0027] In this embodiment, an adsorption pre-liquid with a pH of 9.5–10.5 is used to provide sufficient alkalinity for the adsorbent to adsorb lithium ions, so that lithium ions are fully adsorbed. At the same time, this helps to avoid the problem of adsorbent loss during the adsorption process and improve the service life of the adsorbent.

[0028] In some embodiments of this application, the lithium ion concentration in the pre-adsorption liquid is 200ppm to 500ppm, and the lithium ion concentration in the post-adsorption liquid is <20ppm.

[0029] In this embodiment, controlling the lithium ion concentration in the pre-adsorption liquid to be 200ppm to 500ppm and the lithium ion concentration in the adsorption tail liquid to be <20ppm is beneficial for the adsorbent to fully adsorb lithium ions and control the loss of the adsorbent, thereby reducing the cost of using the adsorbent.

[0030] In some embodiments of this application, the adsorbent includes a titanium-based adsorbent, and after the adsorbent adsorbs lithium ions in the pre-adsorption liquid, the adsorbent is further subjected to desorption treatment with an acid solution.

[0031] In this embodiment, the adsorbent is desorbed by acid to form a lithium solution enriched with lithium ions, which is beneficial for the further recovery and utilization of lithium.

[0032] In some embodiments of this application, the phosphate solution contains sodium ions, and before concentrating and crystallizing the adsorption tail liquid, the method further includes: adjusting the pH value of the adsorption tail liquid to 5.0-6.0; the step of concentrating and crystallizing the adsorption tail liquid includes: sequentially performing evaporation and concentration treatment and freeze crystallization treatment on the adsorption tail liquid to obtain the second solid material and the remaining crystallization liquid; the second solid material is dried to obtain sodium sulfate.

[0033] In this embodiment, adjusting the pH value of the adsorption tail liquid is beneficial to improving the purity of sodium sulfate in the second solid material; the sequential evaporation and concentration treatment and freeze crystallization treatment are beneficial to improving the recovery rate of sodium sulfate.

[0034] In some embodiments of this application, the method further includes: preparing the remaining crystallization liquid into a phosphate solution and reusing it to mix the lithium-containing mother liquor with the phosphate solution.

[0035] In this embodiment, lithium ions and sulfate ions in the crystallization residue have been largely removed. Therefore, a small amount of phosphate ions remain in the crystallization residue. Reusing it in the phosphate solution will not only not affect the recovery rate of lithium ions and sulfate ions, but also help to make full use of phosphate ions and save the cost of resource utilization.

[0036] In some embodiments of this application, the lithium ion concentration in the lithium-containing mother liquor is 1450 ppm to 2700 ppm; and / or,

[0037] The lithium-containing mother liquor is selected from the lithium precipitation mother liquor of waste lithium iron phosphate batteries or the lithium precipitation mother liquor produced by lithium extraction from lithium ore.

[0038] In this embodiment, the resource utilization method is designed to recover specific lithium-containing mother liquor. The required raw material cost is relatively low, the recovery efficiency is relatively high, and the residual lithium ions can be recovered relatively fully, resulting in high economic benefits.

[0039] This application also provides a resource utilization device for lithium-containing mother liquor, comprising: a lithium precipitation reactor, a solid-liquid separator, an adsorber, an evaporator, and a cooling crystallizer; wherein the outlet of the lithium precipitation reactor is connected to the inlet of the solid-liquid separator, the outlet of the solid-liquid separator is connected to the inlet of the adsorber, the adsorber is provided with an adsorbent, the outlet of the adsorber is connected to the inlet of the evaporator, and the outlet of the evaporator is connected to the inlet of the cooling crystallizer.

[0040] The lithium-containing mother liquor resource utilization device is used to realize the lithium-containing mother liquor resource utilization method as described in the above embodiments.

[0041] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0043] Figure 1 is a schematic diagram of the steps of a method for resource utilization of lithium-containing mother liquor according to this application;

[0044] Figure 2 is a process flow diagram of a method for resource utilization of lithium-containing mother liquor according to this application. Detailed Implementation

[0045] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0047] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0049] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0050] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0051] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0052] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0053] In the embodiments of this application, ppm represents the mass of the solute as a percentage of the mass of the solution in parts per million.

[0054] In the embodiments of this application, unless otherwise specified, the solvents for “mother liquor”, “solution”, “tail liquid”, “pre-adsorption liquid”, “acid liquid”, “residual liquid”, etc., are each independently selected from at least one of secondary water, deionized water, distilled water, pure water and ultrapure water.

[0055] This application provides a method for the resource utilization of lithium-containing mother liquor, which includes the following steps: providing lithium-containing mother liquor containing lithium ions and sulfate ions;

[0056] The lithium-containing mother liquor was mixed with a phosphate solution and then subjected to lithium precipitation treatment to obtain a lithium-containing slurry.

[0057] The lithium-containing slurry is subjected to solid-liquid separation treatment to obtain the pre-adsorption liquid and the first solid material;

[0058] Lithium ions in the initial adsorption solution were adsorbed using a titanium-based adsorbent to obtain the final adsorption solution; and,

[0059] The adsorption tail liquid is concentrated and crystallized.

[0060] The molar ratio of lithium ions in the lithium-containing mother liquor to phosphate ions in the phosphate solution is 3:(0.7-0.8).

[0061] In this method for the resource utilization of lithium-containing mother liquor, the lithium-containing mother liquor is first mixed with a phosphate solution. During mixing, the feeding ratio of lithium ions to phosphate ions is controlled at 3:(0.7-0.8). This feeding ratio results in a lower amount of phosphate ions, which is beneficial for improving peritectic effects and increasing the purity of lithium phosphate in the first solid material while precipitating a large amount of lithium ions. When the amount of phosphate ions exceeds 0.8, it not only increases the cost of resource utilization but also introduces excessive phosphate ions into the pre-adsorption liquid, which is detrimental to subsequent adsorption and concentration crystallization. Furthermore, the lithium precipitation process consumes most of the lithium ions in the lithium-containing mother liquor, effectively alleviating the problem of alkalinity reduction during subsequent adsorption and significantly improving the adsorption capacity of the adsorbent for lithium ions. After the above-mentioned lithium precipitation process and lithium ion adsorption, more than 99% of the lithium ions in the lithium-containing mother liquor are recovered, and the residual impurities in the adsorption tail liquid are minimal. The sulfate material obtained from the adsorption tail liquid through concentration and crystallization has high purity.

[0062] Figure 1 is a schematic diagram of the steps of a method for resource utilization of lithium-containing mother liquor according to this application. Referring to Figure 1, the method for resource utilization of lithium-containing mother liquor includes the following steps S1 to S5, as detailed below.

[0063] Step S1: Provide a lithium-containing mother liquor containing lithium ions and sulfate ions.

[0064] As an example of this embodiment, the lithium ion concentration in the lithium-containing mother liquor is between 1450 ppm and 2700 ppm. For example, the lithium ion concentration in the lithium-containing mother liquor can be 1450 ppm, 1500 ppm, 1600 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2400 ppm, 2500 ppm, 2600 ppm, or 2700 ppm, or the lithium ion concentration in the lithium-containing mother liquor can be between any two of the above concentrations.

[0065] As an example of this embodiment, the sulfate ion concentration in the lithium-containing mother liquor is 80 g / L to 105 g / L. For example, the sulfate ion concentration in the lithium-containing mother liquor can be 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, or 105 g / L, or the sulfate ion concentration in the lithium-containing mother liquor can be between any two of the above concentrations.

[0066] In this example, the resource utilization method is designed to recover specific lithium-containing mother liquor. It requires relatively low raw material costs, has relatively high recovery efficiency, and can recover the residual lithium ions relatively fully, resulting in high economic benefits.

[0067] As an example of this embodiment, the lithium-containing mother liquor is selected from the lithium precipitation mother liquor of waste lithium iron phosphate batteries or the lithium precipitation mother liquor produced by lithium extraction from lithium ore. As a further example, the lithium precipitation mother liquor of waste lithium iron phosphate batteries refers to the solution obtained after lithium ions are precipitated and solid-liquid separated during the recycling process of waste lithium iron phosphate batteries. The lithium precipitation mother liquor produced by lithium extraction from lithium ore refers to the solution obtained after lithium ions are precipitated and solid-liquid separated during the lithium extraction process of lithium ore. The product of the above-mentioned lithium ion precipitation is usually lithium carbonate. The precipitation of lithium ions in the above-mentioned precipitation process is not complete; therefore, a certain amount of lithium ions still exists in the lithium precipitation mother liquor. At the same time, the above-mentioned lithium precipitation mother liquor usually also contains a relatively large amount of sulfate ions. The resource utilization method of the lithium-containing mother liquor of this application is applicable to the recovery and utilization of lithium ions in these two types of lithium precipitation mother liquors. In some other embodiments, the resource utilization method of the lithium-containing mother liquor of this application can also be applied to the recovery and utilization of lithium ions from other lithium-containing mother liquors containing similar components as raw materials.

[0068] Step S2: The lithium-containing mother liquor is mixed with the phosphate solution and then subjected to lithium precipitation treatment to obtain a lithium-containing slurry.

[0069] In this embodiment, the molar ratio of lithium ions in the lithium-containing mother liquor to phosphate ions in the phosphate solution is 3:(0.7-0.8). Optionally, the molar ratio of lithium ions in the lithium-containing mother liquor to phosphate ions in the phosphate solution can be 3:0.7, 3:0.72, 3:0.74, 3:0.76, 3:0.78, or 3:0.8. This feeding ratio uses a lower amount of phosphate ions, which is beneficial for improving the peritectic problem and increasing the purity of lithium phosphate in the first solid material while precipitating a large amount of lithium ions. When the amount of phosphate ions is higher (e.g., the molar ratio of lithium ions in the lithium-containing mother liquor to phosphate ions in the phosphate solution is 3:0.9, 3:1, 3:2, etc.), the improvement in lithium ion recovery rate is extremely limited. This not only increases material costs but also introduces excessive phosphate ions into the solution, which is detrimental to the purity of the material obtained in the subsequent concentration and crystallization steps. When the amount of phosphate ions used is less (e.g., the molar ratio of lithium ions in lithium mother liquor to phosphate ions in phosphate solution is 3:0.4, 3:0.5, 3:0.6, etc.), the yield of lithium phosphate solid material is low, and the concentration of lithium ions in lithium slurry is still high, which is not conducive to adsorption in subsequent steps.

[0070] As an example of this embodiment, the step of mixing the lithium-containing mother liquor with the phosphate solution can be carried out in a reaction vessel.

[0071] As an example of this embodiment, in the step of mixing the lithium-containing mother liquor with the phosphate solution, the lithium-containing mother liquor is added to the phosphate solution.

[0072] Traditional techniques typically involve directly adding solid phosphate or phosphate solution to lithium-containing mother liquor. This forward feeding method easily leads to peritectic formation of lithium phosphate, increasing phosphate consumption and resulting in a low lithium-ion yield. In this embodiment, a reverse feeding method is used, where lithium-containing mother liquor is added to the phosphate solution. This effectively avoids the peritectic problem and promotes more complete precipitation of lithium ions, further improving the purity of lithium phosphate in the first solid material and the lithium-ion recovery rate.

[0073] As a further example of this embodiment, the lithium-containing mother liquor is added to the phosphate solution over a period of 0.5 h to 4 h. It is understood that the lithium-containing mother liquor can be added to the phosphate solution in batches or continuously.

[0074] In this embodiment, the lithium-containing mother liquor is added to the phosphate solution within 0.5h to 4h, which is beneficial for the full crystallization and growth of lithium phosphate and improves the purity of lithium phosphate in the obtained first solid material.

[0075] As an example of this embodiment, the phosphate in the phosphate solution includes one or more of sodium dihydrogen phosphate and disodium hydrogen phosphate. It will be understood that in other embodiments, the phosphate in the phosphate solution may also be other soluble phosphates, such as sodium phosphate.

[0076] In this embodiment, sodium dihydrogen phosphate and disodium hydrogen phosphate have high solubility. Using sodium dihydrogen phosphate and disodium hydrogen phosphate as solutes in the phosphate solution helps to reduce the required volume of the phosphate solution, reduce the dilution of lithium ions during the feeding process, and facilitate the full precipitation of lithium ions. In addition, sodium dihydrogen phosphate and disodium hydrogen phosphate can also generate hydrogen ions, which helps to adjust the pH value after the lithium precipitation reaction to a suitable range, reducing or avoiding the use of additional acid-base regulators.

[0077] As an example of this embodiment, the phosphate solution is a saturated solution of phosphate ions.

[0078] In this embodiment, compared to an unsaturated solution, using a saturated solution of phosphate ions as the phosphate salt allows lithium ions to combine and precipitate more quickly and fully with phosphate ions, which is beneficial for obtaining a higher lithium ion recovery rate and resource utilization efficiency.

[0079] As an example of this embodiment, before mixing the lithium-containing mother liquor with the phosphate solution, the lithium-containing mother liquor is heated to 80°C to 100°C, preferably 90°C to 95°C. For example, the lithium-containing mother liquor can be heated to 85°C, 90°C, 91°C, 92°C, 93°C, 94°C, or 95°C, or it can be heated to any two of the above temperatures. Heating the lithium-containing mother liquor to 80°C to 100°C, preferably 90°C to 95°C, is more conducive to promoting the formation of lithium phosphate precipitation. Heating the lithium-containing mother liquor to 80°C to 100°C, preferably 90°C to 95°C, is beneficial for lithium ions in the lithium-containing mother liquor to combine more rapidly with phosphate ions to form precipitation during the lithium precipitation process, which is beneficial to improving production efficiency and lithium ion recovery rate.

[0080] As a further example of this embodiment, in order to fully precipitate lithium ions, lithium precipitation treatment is typically performed at a temperature of 80°C to 100°C, preferably 90°C to 95°C. Therefore, heating the lithium-containing mother liquor to 90°C to 95°C before mixing it with the phosphate solution helps to save heating time during the lithium precipitation process, thereby improving production efficiency.

[0081] As an example of this embodiment, during the lithium deposition process, the lithium deposition temperature is 80℃~100℃, preferably 90℃~95℃, and the holding time is 2h~4h. For example, the lithium deposition temperature is 85℃, 90℃, 91℃, 92℃, 93℃, 94℃, or 95℃, or the lithium deposition temperature can be between any two of the above temperatures. Similarly, the lithium deposition holding time is 2h, 2.5h, 3h, 3.5h, or 4h, or the lithium deposition holding time can be between any two of the above temperatures.

[0082] In this embodiment, heating the lithium-containing mother liquor to 80℃~100℃, preferably 90℃~95℃, and controlling the lithium precipitation temperature to 80℃~100℃, preferably 90℃~95℃, is beneficial for the rapid and sufficient formation of precipitates between lithium ions and phosphate ions in the lithium-containing mother liquor, thereby improving the efficiency of resource utilization and the recovery rate of lithium ions. Controlling the holding time to within 2h~4h is beneficial for the full crystallization and crystal growth of lithium phosphate, further improving the purity of lithium phosphate in the resulting first solid material.

[0083] After the reaction process as described in step S2, the main component of the solid phase in the lithium-containing slurry is lithium phosphate precipitate, while the liquid phase contains residual lithium ions and sulfate ions.

[0084] Step S3: The lithium-containing slurry undergoes solid-liquid separation treatment to obtain the pre-adsorption liquid and the first solid material.

[0085] As an example of this embodiment, the solid-liquid separation process can be performed in a solid-liquid separator. Further, depending on the actual separation method, the solid-liquid separator may include a filter press, centrifuge, vacuum filter, or sedimentation tank. In this embodiment, a plate and frame filter press can be used to achieve the separation between the pre-adsorption liquid and the first solid material.

[0086] As an example of this embodiment, the solid-liquid separation process is filtration, such as pressure filtration or vacuum filtration. In other embodiments, the solid-liquid separation process may also be centrifugation or settling. The solid phase material obtained after the solid-liquid separation process is used as the first solid material, and the obtained liquid phase material is used as the pre-adsorption liquid, which contains residual lithium ions and sulfate ions.

[0087] As an example of this embodiment, the lithium ion concentration in the pre-adsorption solution is 200 ppm to 500 ppm. For example, the lithium ion concentration in the pre-adsorption solution can be 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, or 500 ppm, or the lithium ion concentration in the pre-adsorption solution can be between any two of the above concentrations.

[0088] In this embodiment, controlling the lithium ion concentration in the pre-adsorption liquid to be 200ppm to 500ppm and the lithium ion concentration in the adsorption tail liquid to be <20ppm is beneficial for the adsorbent to fully adsorb lithium ions and control the loss of the adsorbent, thereby reducing the cost of using the adsorbent.

[0089] As an example of this embodiment, the pH value of the pre-adsorption solution is 9.5 to 10.5.

[0090] Titanium-based adsorbents suffer from solubility issues when exposed to solutions with a pH greater than 11.5. In this embodiment, an adsorption pre-solution with a pH of 9.5–10.5 is used. This provides sufficient alkalinity for the adsorbent to adsorb lithium ions, ensuring their full adsorption while also helping to avoid solubility issues during adsorption and extending the adsorbent's lifespan.

[0091] It is understandable that using sodium dihydrogen phosphate or disodium hydrogen phosphate as the phosphate salt can introduce a small amount of hydrogen ions into the lithium-containing slurry, thereby maintaining the pH of the pre-adsorption liquid after solid-liquid separation at 9.5–10.5. This eliminates the need for additional pH adjusters and avoids dilution of the lithium ion concentration in the slurry. If other phosphate neutral salts (such as sodium phosphate) are used, the pH of the lithium-containing slurry will be too high, requiring additional pH adjustment processes, such as adding pH adjusters (e.g., phosphoric acid, sulfuric acid), which will also lead to a decrease in the lithium ion concentration.

[0092] As an example of this embodiment, after the solid-liquid separation process, the method further includes washing the first solid material with a washing solution. The washing solution can be at least one of pure water, distilled water, ultrapure water, and deionized water. Furthermore, in the step of washing the first solid material with the washing solution, the first solid material can be washed once or multiple times (e.g., twice, three times, four times, five times, etc.), and the volume of the washing solution used in each wash is more than twice the volume of the first solid material, in order to remove soluble impurity ions from the first solid material.

[0093] As an example of this embodiment, after washing the first solid material with a washing liquid, a step of drying the washed first solid material (e.g., baking) is further included to remove moisture from the washed first solid material.

[0094] In this example, the first solid material obtained by washing with a washing solution removes residual impurity ions from the surface of lithium phosphate, further improving the purity of lithium phosphate in the first solid material. Experimental verification shows that the purity (by mass fraction) of the lithium phosphate material obtained from the lithium precipitation treatment of this application, after washing with a washing solution and drying, reaches over 95%, meeting the industrial-grade lithium phosphate standard. That is, after washing and drying, the first solid material can be directly sold or returned to the production line to increase the lithium concentration in the leachate. For example, in a battery black powder lithium extraction production line, lithium phosphate can be returned to the lithium leaching process section of the battery powder recycling production line to increase the lithium concentration in the leachate. In a lithium ore lithium extraction production line, lithium phosphate can be returned to the phosphoric acid roasting process section to increase the lithium concentration in the leachate.

[0095] As a further example of this embodiment, after the first solid material is washed with pure water and dried, the purity (by mass fraction) of lithium phosphate is above 95%. For example, the purity of lithium phosphate can be 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, or 99%, or the purity of lithium phosphate can be between any two of the above purities.

[0096] Step S4: Use an adsorbent to adsorb lithium ions in the pre-adsorption liquid to obtain the adsorption tail liquid.

[0097] It is understood that the adsorbent should be selected from those capable of adsorbing lithium ions from the solution. As an example of this embodiment, the adsorbent includes a titanium-based adsorbent. Compared to aluminum-based adsorbents, which are unsuitable for alkaline solutions, and manganese-based adsorbents, which are unsuitable for solutions containing sulfate ions, titanium-based adsorbents have a relatively long service life and can ensure sufficient adsorption of lithium ions.

[0098] As an example of this embodiment, the titanium-based adsorbent is selected from at least one of the following products: Anhui Yuxiang UL-6, Tefeng New Materials G-100, Tefeng New Materials G-200, Jiuwu High-Tech JW-LTOS, Haipu HP180, and Haipu HPL900.

[0099] As an example of this embodiment, the adsorbent can be placed in a fixed bed or a continuous moving bed adsorption device, so that the liquid before adsorption flows through the adsorbent, which facilitates the adsorbent to adsorb lithium ions in the liquid before adsorption.

[0100] As a further example of this embodiment, in the step of adsorbing lithium ions in the pre-adsorption liquid, the adsorption time can be controlled to be 3h to 10h. For example, the adsorption time can be controlled to be 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h, or the adsorption time can be controlled to be between any two of the above times.

[0101] In this example, by controlling the adsorption time, it is beneficial to ensure that the adsorbent fully adsorbs the lithium ions in the pre-adsorption liquid.

[0102] It is understandable that, during the process of using an adsorbent to adsorb lithium ions in the pre-adsorption liquid, the flow rate of the pre-adsorption liquid can be adjusted according to the lithium ion concentration in the pre-adsorption liquid in order to balance the lithium ion recovery rate and adsorption efficiency.

[0103] In this embodiment, by sequentially employing lithium precipitation treatment and adsorbent adsorption, most of the lithium ions in the lithium-containing mother liquor were recovered. This not only facilitates the full recovery of lithium ions but also helps to obtain byproducts with high purity.

[0104] As an example of this embodiment, the lithium ion concentration in the adsorption tail liquid is <20ppm.

[0105] As an example of this embodiment, after using an adsorbent to adsorb lithium ions in the pre-adsorption liquid, the method further includes: using an acid solution to desorb the adsorbent.

[0106] In this embodiment, the adsorbent is desorbed using acid to form a lithium solution enriched with lithium ions, which is beneficial for further recovery and utilization of lithium. This lithium solution can be fed into a lithium carbonate production line, or it can be concentrated in an evaporator to obtain lithium-containing solids.

[0107] As a further example of this embodiment, in the process of desorbing the adsorbent with an acid solution, a strong acid is used. Preferably, the acid solution is selected from one or more of dilute sulfuric acid and dilute hydrochloric acid. Dilute sulfuric acid and dilute hydrochloric acid are strong acids but not strong oxidizing acids, which is beneficial for maintaining the service life of the adsorbent.

[0108] As a further example of this embodiment, the pH value of the acid solution used is 1.5 to 1.8. For example, the pH value of the acid solution used is 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, or 1.8, or the pH value of the acid solution used can be between any two of the above pH values. Using an acid solution within this pH range can ensure sufficient desorption of lithium ions.

[0109] As a further example of this embodiment, the temperature of the acid solution used in the desorption process is 40°C to 50°C. For example, the temperature of the acid solution used is 40°C, 42°C, 44°C, 45°C, 46°C, 48°C, or 50°C, or the temperature of the acid solution used may be between any two of the above temperatures.

[0110] Step S5: The adsorption tail liquid is concentrated and crystallized to obtain the second solid material.

[0111] It is understood that after the pre-adsorption liquid is adsorbed by the adsorbent, an adsorption tail liquid is formed. The lithium ions in the adsorption tail liquid are essentially removed, and the main components of the adsorption tail liquid are cations and sulfate ions from the phosphate solution. Therefore, the main component of the second solid material formed after the adsorption tail liquid is concentrated and crystallized is sulfate. In this embodiment, the main components of the adsorption tail liquid are sodium ions and sulfate ions. When the adsorption tail liquid is concentrated and crystallized, the main component of the second solid material formed is sodium sulfate, i.e., sodium sulfate (sodium sulfate).

[0112] As an example of this embodiment, before concentrating and crystallizing the adsorption tail liquid, the method further includes: adjusting the pH value of the adsorption tail liquid to 5.0 to 6.0.

[0113] In this embodiment, adjusting the pH value of the adsorption tail liquid is beneficial to improving the purity of sodium sulfate in the second solid material.

[0114] As a further example of this embodiment, sulfuric acid can be used to adjust the pH value of the adsorption tail liquid. Adjusting the pH value of the adsorption tail liquid with sulfuric acid can avoid the introduction of other impurity ions and also helps to improve the purity of sodium sulfate in the second solid material.

[0115] As an example of this embodiment, the steps of concentrating and crystallizing the adsorption tail liquid include: sequentially performing evaporation concentration and freeze crystallization on the adsorption tail liquid to obtain a second solid material and a remaining crystallization liquid; the second solid material is then dried (e.g., thermal drying) to obtain sodium sulfate. Specifically, during the evaporation concentration process, the adsorption tail liquid can be evaporated until crystals are about to precipitate, and then the adsorption tail liquid is subjected to freeze crystallization.

[0116] The sequential evaporation and concentration process, followed by freeze crystallization, helps to improve the recovery rate of sodium sulfate. During the evaporation and concentration process, the adsorption tail liquid can be evaporated until crystals are about to precipitate, and then the adsorption tail liquid is subjected to freeze crystallization.

[0117] As an example of this embodiment, the step of evaporating and concentrating the adsorbed tail liquid can be carried out in an evaporator, and the step of cooling and crystallizing the adsorbed tail liquid can be carried out in a cooling crystallizer.

[0118] As an example of this embodiment, the purity (by mass fraction) of sodium sulfate in the obtained sodium sulfate is above 99%.

[0119] As an example of this embodiment, the lithium ion content (by mass concentration) in the obtained sodium sulfate is less than 50 ppm.

[0120] As a further example of this embodiment, it also includes the step of preparing the remaining crystallization liquid into a phosphate solution and reusing it to mix the lithium-containing mother liquor with the phosphate solution.

[0121] In this embodiment, lithium ions and sulfate ions in the crystallization residue have been largely removed. Therefore, a small amount of phosphate ions remain in the crystallization residue. Reusing it in the phosphate solution will not only not affect the recovery rate of lithium ions and sulfate ions, but also help to make full use of phosphate ions and save the cost of resource utilization.

[0122] As a further example of this embodiment, in the process of preparing the crystallization residue into a phosphate solution, phosphate can be added to the crystallization residue to prepare a saturated solution that forms phosphate ions.

[0123] As a further example of this embodiment, in the process of preparing the crystallization residue into a phosphate solution, phosphate and phosphoric acid can be added to the crystallization residue to prepare a saturated solution forming sodium dihydrogen phosphate and / or disodium hydrogen phosphate.

[0124] It is understood that the resource utilization method of lithium-containing mother liquor of this application can be completed through the above steps S1 to S5.

[0125] Experimental verification shows that the resource utilization method of lithium-containing mother liquor in this embodiment first uses phosphate solution to initially recover lithium from the mother liquor, recovering approximately 80% of the lithium. Then, an adsorbent is used for a secondary recovery of the remaining approximately 20% of lithium in the unadsorbed liquid. These two recovery processes achieve a lithium recovery rate of over 99% in the lithium-containing mother liquor, ensuring full recovery of lithium. The initial recovery utilizes a relatively low cost to recover most of the lithium, while the higher-cost secondary recovery ensures full recovery of the remaining lithium. Compared to methods using only phosphate solution or only adsorbent, which suffer from low recovery rates and difficulty in recovering low-concentration lithium in the remaining liquid, or methods using only adsorbents that are suitable for different systems, resulting in low lithium adsorption rates and high costs due to large adsorbent usage, this resource utilization method achieves full lithium recovery while controlling recovery costs. Furthermore, since the lithium recovery rate of the lithium-containing mother liquor resource utilization method of this application can reach more than 99%, the lithium impurity content in the adsorption tail liquid is extremely low. After further concentration and crystallization treatment, the adsorption tail liquid can form a by-product with extremely high purity, generating additional economic benefits.

[0126] Furthermore, this application also provides a resource utilization device for lithium-containing mother liquor, comprising: a lithium precipitation reactor, a solid-liquid separator, an adsorber, an evaporator, and a cooling crystallizer. The outlet of the lithium precipitation reactor is connected to the inlet of the solid-liquid separator; the solid outlet of the solid-liquid separator is connected to the inlet of the material collection container; the liquid outlet of the solid-liquid separator is connected to the inlet of the adsorber; the adsorber contains an adsorbent; the outlet of the adsorber is connected to the inlet of the evaporator; and the outlet of the evaporator is connected to the inlet of the cooling crystallizer.

[0127] The lithium-containing mother liquor resource utilization device is used to realize the lithium-containing mother liquor resource utilization method as described in the above embodiments.

[0128] The lithium precipitation reactor serves as a container for the lithium precipitation process after mixing lithium-containing mother liquor with phosphate solution. The solid-liquid separator separates the lithium-containing slurry formed after the precipitation process, yielding a pre-adsorption liquid and a first solid material. The adsorber adsorbs lithium ions from the pre-adsorption liquid obtained after solid-liquid separation and discharges the adsorption tail liquid. The evaporator concentrates the adsorption tail liquid discharged from the adsorber, and the cooling crystallizer cools and crystallizes the liquid discharged from the evaporator, thus obtaining a second solid material.

[0129] As an example of this embodiment, phosphorus and lithium are enriched and concentrated in the crystallization residue after cooling and crystallization. Mixing the crystallization residue with phosphate and water can prepare a phosphate solution for lithium precipitation treatment, which facilitates high recovery rates of lithium and phosphorus and reduces discharge losses.

[0130] As an example of this embodiment, the lithium deposition reactor may include a reaction vessel.

[0131] As an example of this embodiment, depending on the actual separation method, the solid-liquid separator may include a filter press, a centrifuge, a vacuum filter, or a sedimentation tank. In this embodiment, a plate and frame filter press may be used to achieve the separation between the pre-adsorption liquid and the first solid material.

[0132] As an example of this embodiment, the adsorber may include a fixed-bed adsorber or a moving-bed adsorber. The adsorbent in the adsorber is selected from titanium-based adsorbents.

[0133] The lithium-containing mother liquor resource utilization system can realize the lithium-containing mother liquor resource utilization method as described in the above embodiments.

[0134] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0135] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0136] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0137] Example 1

[0138] The lithium-containing mother liquor is utilized using the process flow shown in Figure 2, as detailed below.

[0139] (1) The solution after lithium carbonate precipitation of waste lithium iron phosphate batteries (i.e. lithium precipitation mother liquor) is used as lithium-containing mother liquor, with a lithium concentration of 1600ppm±150ppm and a sulfate ion concentration of 80g / L.

[0140] (2) Control the temperature of the lithium-containing mother liquor to 92℃, and gradually add the lithium-containing mother liquor to the prepared phosphate solution within 2 hours. The phosphate solution is a saturated sodium dihydrogen phosphate (NaH2PO4) solution. The ratio of the amount of lithium in the lithium-containing mother liquor to the amount of phosphate ions in the phosphate solution is 3:0.75. After the feeding is completed, continue to keep the temperature for 3 hours. During the feeding process and the heat preservation process, keep the overall temperature of the mixed solution at 92℃ to allow lithium phosphate to fully precipitate. After the reaction, a lithium-containing slurry is obtained.

[0141] (3) Filtration is used to separate the solid phase and liquid phase components in the lithium-containing slurry. The solid phase component is used as the first solid material and the liquid phase component is used as the pre-adsorption liquid. The first solid material is washed with pure water at a volume ratio of 3:1. The washing is repeated 3 times, and then the first solid material is dried to obtain the lithium phosphate product.

[0142] (4) The pre-adsorption liquid obtained in step (3) is put into a fixed bed adsorption device filled with titanium adsorbent (Anhui Yuxiang UL-6) to adsorb lithium ions. The lithium concentration of the pre-adsorption liquid is 450ppm±50ppm. The flow rate of the pre-adsorption liquid is controlled so that the adsorption time of the pre-adsorption liquid through the titanium adsorbent is 8h. The effluent liquid is collected as the adsorption tail liquid. The lithium ion concentration in the adsorption tail liquid is less than 20ppm. The titanium adsorbent is desorbed using dilute sulfuric acid with a pH of 1.6 and a temperature of 45℃ to obtain a lithium solution.

[0143] (5) After adjusting the pH of the adsorption tail liquid obtained in step (4) to 5.5, perform evaporation and concentration treatment. When the crystals are about to precipitate, perform freeze crystallization treatment, dry the obtained crystals, and obtain sodium sulfate product.

[0144] Example 2

[0145] The difference between Example 2 and Example 1 is only that in step (1), the solution after lithium carbonate precipitation (i.e., lithium precipitation mother liquor) produced by lithium extraction from lithium ore is used as lithium-containing mother liquor, in which the lithium concentration is 2200ppm±200ppm and the sulfate ion concentration is 95g / L.

[0146] Example 3

[0147] The difference between Example 3 and Example 1 is only that in step (1), the solution after lithium carbonate precipitation (i.e., lithium precipitation mother liquor) produced by lithium extraction from lithium ore is used as lithium-containing mother liquor, in which the lithium concentration is 1800ppm±150ppm and the sulfate ion concentration is 88g / L.

[0148] Example 4

[0149] The difference between Example 4 and Example 1 is only that in step (1), the solution after lithium carbonate precipitation (i.e., lithium precipitation mother liquor) produced by lithium extraction from lithium ore is used as lithium-containing mother liquor, in which the lithium concentration is 2500ppm±200ppm and the sulfate ion concentration is 105g / L.

[0150] Example 5

[0151] The difference between Example 5 and Example 1 is only that in step (2), the ratio of the amount of lithium in the lithium-containing mother liquor to the amount of phosphate ions in the phosphate solution is 3:0.7.

[0152] Example 6

[0153] The only difference between Example 6 and Example 1 is that in step (2), the ratio of the amount of lithium in the lithium-containing mother liquor to the amount of phosphate ions in the phosphate solution is 3:0.8.

[0154] Example 7

[0155] The difference between Example 7 and Example 1 is only that: in step (2), the temperature of the lithium-containing mother liquor is controlled at 95°C, and the temperature of the mixed solution as a whole is kept at 95°C during the feeding process and the heat preservation process.

[0156] Example 8

[0157] The difference between Example 8 and Example 1 is only that: in step (2), the temperature of the lithium-containing mother liquor is controlled at 90°C, and the temperature of the mixed solution as a whole is kept at 90°C during the feeding process and the heat preservation process.

[0158] Example 9

[0159] The only difference between Example 9 and Example 1 is that in step (2), the phosphate solution is a saturated disodium hydrogen phosphate (Na2HPO4) solution.

[0160] Example 10

[0161] The only difference between Example 10 and Example 1 is that in step (2), the prepared phosphate solution is gradually added to the lithium-containing mother liquor over 2 hours.

[0162] Example 11

[0163] The only difference between Example 11 and Example 1 is that in step (2), the lithium-containing mother liquor is gradually added to the prepared phosphate solution over 0.1 hours.

[0164] Example 12

[0165] The only difference between Example 12 and Example 1 is that in step (2), the lithium-containing mother liquor is gradually added to the prepared phosphate solution over 0.5 hours.

[0166] Example 13

[0167] The only difference between Example 13 and Example 1 is that in step (2), the lithium-containing mother liquor is gradually added to the prepared phosphate solution over 4 hours.

[0168] Example 14

[0169] The only difference between Example 14 and Example 1 is that in step (2), the material is kept warm for 1.5 hours after feeding.

[0170] Example 15

[0171] The only difference between Example 15 and Example 1 is that in step (4), dilute sulfuric acid with a pH of 1.8 and a temperature of 50°C is used to desorb the titanium adsorbent.

[0172] Example 16

[0173] The only difference between Example 16 and Example 1 is that in step (4), dilute sulfuric acid with a pH of 1.5 and a temperature of 40°C is used to desorb the titanium adsorbent.

[0174] Example 17

[0175] The only difference between Example 17 and Example 1 is that in step (4), the flow rate of the pre-adsorption liquid is controlled so that the adsorption time of the pre-adsorption liquid through the titanium adsorbent is 10h.

[0176] Example 18

[0177] The only difference between Example 18 and Example 1 is that in step (4), the flow rate of the pre-adsorption liquid is controlled so that the adsorption time of the pre-adsorption liquid through the titanium adsorbent is 3 hours.

[0178] Comparative Example 1

[0179] (1) The solution after lithium carbonate precipitation of waste lithium iron phosphate batteries (i.e. lithium precipitation mother liquor) is used as lithium-containing mother liquor, and the lithium concentration is 1600ppm±200ppm.

[0180] (2) The lithium-containing mother liquor from step (1) is added to a fixed-bed adsorption device filled with titanium adsorbent to adsorb lithium ions. The flow rate of the pre-adsorption liquid is controlled so that the adsorption time of the pre-adsorption liquid through the titanium adsorbent is 8 hours. The outflow liquid is collected as the adsorption tail liquid. The pH value of the adsorption tail liquid is 6.5 and the concentration of lithium ions in the adsorption tail liquid is 160ppm±50ppm. The titanium adsorbent is desorbed using dilute sulfuric acid with a pH value of 1.6 and a temperature of 45℃ to obtain a lithium solution.

[0181] Comparative Example 2

[0182] The difference between this comparative example and Example 1 is as follows:

[0183] (2) Control the temperature of the lithium-containing mother liquor to 92℃, and gradually add sodium phosphate solid to the lithium-containing mother liquor over 2 hours. The ratio of the amount of lithium in the lithium-containing mother liquor to the amount of phosphate ions in the sodium phosphate solid is 3:0.75. After the feeding is completed, continue to keep the temperature for 3 hours. During the feeding and keeping process, maintain the overall temperature of the mixed solution at 92℃ to allow lithium phosphate to fully precipitate. After the reaction, a lithium-containing slurry is obtained.

[0184] Comparative Example 3

[0185] The only difference between Comparative Example 3 and Comparative Example 2 is that in (2), sodium dihydrogen phosphate solid was gradually added to the lithium-containing mother liquor over 2 hours.

[0186] Comparative Example 4

[0187] The difference between Comparative Example 4 and Example 1 is as follows:

[0188] In (2), the ratio of the amount of lithium in the lithium-containing mother liquor to the amount of phosphate ions in the phosphate solution is 3:1.1.

[0189] Comparative Example 5

[0190] The difference between Comparative Example 5 and Example 1 is as follows:

[0191] In (2), the ratio of the amount of lithium in the lithium-containing mother liquor to the amount of phosphate ions in the phosphate solution is 3:0.6.

[0192] Performance testing

[0193] 1. The content of lithium phosphate and the content of each impurity element in the lithium phosphate products prepared in steps (3) of Examples 1 to 18 and Comparative Examples 2 to 5 were tested by inductively coupled plasma mass spectrometry (ICP-MS). The results are shown in Table 1.

[0194] 2. The content of each element in the lithium solution obtained in step (4) of Examples 1 to 18 and the lithium solutions prepared by Comparative Examples 1, 4 to 5 were tested by inductively coupled plasma mass spectrometry. The results are shown in Table 2.

[0195] 3. The sodium sulfate content and the content of each impurity element in the sodium sulfate obtained in step (5) of Examples 1 to 18 and the sodium sulfate prepared in Comparative Examples 4 and 5 were tested by inductively coupled plasma mass spectrometry. The results are shown in Table 3.

[0196] Table 1

[0197]

[0198] As shown in Table 1, the lithium phosphate products obtained in Examples 1 to 18 have a high mass fraction of lithium phosphate, all above 95%, and also contain Ca, Mg, Cl, Si, Zn, Na, and SO4. 2- The low content of impurities indicates that the resource utilization method of lithium-containing mother liquor provided in this application involves first mixing the lithium-containing mother liquor with a phosphate solution and then performing lithium precipitation treatment. During mixing, the feeding ratio of lithium ions to phosphate ions is controlled at 3:(0.7-0.8). Then, a titanium-based adsorbent is used to adsorb the lithium ions in the pre-adsorption liquid. This achieves the recovery of more than 99% of lithium ions from the lithium-containing mother liquor.

[0199] In Comparative Example 1, titanium-based adsorbents were used to directly recover lithium-containing mother liquor. The lithium concentration in the mother liquor was high. Directly using titanium-based adsorbents involved replacing hydrogen ions in titanate molecules with lithium ions, which required alkalinity in the solution. However, the alkalinity in the lithium-containing mother liquor was limited and insufficient to provide the necessary alkalinity for lithium ion adsorption. When the alkalinity in the adsorption tail liquid was insufficient, lithium ions could not be adsorbed, and a significant amount of lithium could not be recovered. The lithium recovery rate was approximately 90%. Furthermore, titanium-based adsorbents are expensive, increasing the amount used by more than five times, and simultaneously increasing the equipment scale by five times. This resulted in high equipment investment and a high cost for the resource utilization of lithium-containing mother liquor, reaching 30,000 yuan / ton of lithium carbonate.

[0200] Comparative Example 2 uses solid sodium phosphate to recover lithium phosphate. Using solid sodium phosphate as a lithium recovery agent results in poor solubility, leading to severe peritectic effects. Lithium phosphate coats the sodium phosphate, resulting in a low purity of only 80.7% for the lithium phosphate product.

[0201] In Comparative Example 3, sodium dihydrogen phosphate solid was added to lithium-containing mother liquor. The resulting lithium phosphate solid contained sodium ions in crystals, and the peritectic phenomenon was also severe. The purity of the obtained lithium phosphate product was low, only 89.7%.

[0202] In Comparative Example 4, the ratio of the amount of lithium in the lithium-containing mother liquor to the amount of phosphate ions in the phosphate solution was 3:1.1, which had very limited effect on improving the lithium ion recovery rate. This not only increased the material cost but also introduced too many phosphate ions into the solution, which was not conducive to the purity of the material obtained in the subsequent concentration and crystallization steps.

[0203] In Comparative Example 5, the ratio of the amount of lithium in the lithium-containing mother liquor to the amount of phosphate ions in the phosphate solution was 3:0.6. The yield of lithium phosphate product was low, and the concentration of lithium ions in the lithium-containing slurry was high, which was not conducive to the full adsorption of lithium ions in subsequent steps.

[0204] Table 2

[0205]

[0206] Table 3

[0207]

[0208] As shown in Table 2, the resource utilization method of lithium-containing mother liquor provided in this application obtains a lithium solution enriched with lithium ions and low content of other metal elements by adsorbing lithium ions in the pre-adsorption liquid and desorbing the adsorbent with acid solution. The adsorption time is controlled at 3h to 10h, the pH value of the acid solution used for desorption is 1.5 to 1.8, and the temperature of the acid solution used for desorption is 40℃ to 50℃. This achieves further recovery and utilization of lithium elements.

[0209] As shown in Table 3, the resource utilization method of lithium-containing mother liquor provided in this application obtains sodium sulfate with a purity between 99.13% and 99.57% through the concentration and crystallization treatment of the adsorption tail liquid, realizing the full resource utilization of the adsorption tail liquid and generating additional economic benefits.

[0210] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for resource utilization of a lithium-containing mother liquor, characterized in that, The method comprises the following steps: providing a lithium-containing mother liquor containing lithium ions and sulfate ions; mixing the lithium-containing mother liquor with a phosphate solution to perform lithium precipitation treatment, to obtain a lithium-containing slurry; performing solid-liquid separation treatment on the lithium-containing slurry to obtain a pre-adsorption liquid and a first solid material; using an adsorbent to adsorb lithium ions in the pre-adsorption liquid to obtain an adsorption tail liquid; and, performing concentration and crystallization treatment on the adsorption tail liquid to obtain a second solid material; wherein the molar ratio of lithium ions in the lithium-containing mother liquor to phosphate ions in the phosphate solution is 3:(0.7-0.8).

2. The method for resource utilization of lithium-containing liquor according to claim 1, characterized in that, During the mixing of the lithium-containing mother liquor with the phosphate solution, the lithium-containing mother liquor is added to the phosphate solution; and / or, the lithium-containing mother liquor is added to the phosphate solution within 0.5-4 hours.

3. The method for resource utilization of lithium-containing liquor according to claim 2, characterized in that, the phosphate in the phosphate solution comprises one or more of sodium dihydrogen phosphate and disodium hydrogen phosphate; and / or, the phosphate solution is a saturated solution of phosphate ions; and / or, after the solid-liquid separation treatment, the first solid material is washed with a washing liquid.

4. The method for resource utilization of lithium-containing liquor according to claim 3, characterized in that, before the mixing of the lithium-containing mother liquor with the phosphate solution, the lithium-containing mother liquor is heated to 80-100°C; and / or, the temperature of the lithium precipitation treatment is 80-100°C, and the holding time of the lithium precipitation treatment is 2-4 hours.

5. The method for resource utilization of lithium-containing mother liquor according to any one of claims 1 to 4, characterized in that, the pH value of the pre-adsorption liquid is 9.5-10.5; and / or, the lithium ion concentration in the pre-adsorption liquid is 200-500 ppm, and the lithium ion concentration in the adsorption tail liquid is <20 ppm.

6. The method for resource utilization of lithium-containing mother liquor according to any one of claims 1 to 4, characterized in that, the adsorbent comprises a titanium-based adsorbent, and after the adsorption of lithium ions in the pre-adsorption liquid with the adsorbent, the adsorbent is desorbed with an acid liquid.

7. The method for resource utilization of lithium-containing mother liquor according to any one of claims 1 to 4, characterized in that, the phosphate solution contains sodium ions, and before the concentration and crystallization treatment on the adsorption tail liquid, the pH value of the adsorption tail liquid is adjusted to 5.0-6.0; the concentration and crystallization treatment on the adsorption tail liquid comprises sequentially performing evaporation concentration treatment and freezing crystallization treatment on the adsorption tail liquid, to obtain the second solid material and a crystallization residual liquid; the second solid material is dried to obtain sodium phosphate.

8. The method for resource utilization of lithium-containing liquor according to claim 7, characterized in that, further comprising: the crystallization residual liquid is prepared into a phosphate solution, and is used for the mixing of the lithium-containing mother liquor with the phosphate solution.

9. The method for resource utilization of lithium-containing mother liquor according to any one of claims 1 to 4, characterized in that, the lithium ion concentration in the lithium-containing mother liquor is 1450-2700 ppm; and / or, the lithium-containing mother liquor is selected from a lithium precipitation mother liquor of a waste lithium iron phosphate battery or a lithium precipitation mother liquor produced by lithium ore extraction.

10. A device for resource utilization of a lithium-containing mother liquor, characterized by comprising: a lithium precipitation reactor, a solid-liquid separator, an adsorber, an evaporator, and a cooling crystallizer; wherein the discharge outlet of the lithium precipitation reactor and the inlet of the solid-liquid separator are connected, the discharge outlet of the solid-liquid separator and the inlet of the adsorber are connected, the adsorber is provided with an adsorbent, the discharge outlet of the adsorber and the inlet of the evaporator are connected, and the discharge outlet of the evaporator and the inlet of the cooling crystallizer are connected.

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