A method for resource utilization of lithium precipitation mother liquor

Abstract

The present application provides a method for resource utilization of lithium precipitate mother liquor, which belongs to the field of waste resource utilization, wherein the method comprises the following steps: adjusting the pH of the lithium precipitate mother liquor to acidic, adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source, mixing uniformly to obtain a first slurry, and thereafter, drying, calcining and washing to obtain a sodium ferrous sulfate cathode material; wherein, the waste gas generated by the calcination is subjected to dust collection treatment to obtain a dust collection material, the dust collection material is mixed with water to obtain a second slurry, and the pH of the second slurry is adjusted to alkaline to obtain a filtrate through solid-liquid separation, and thereafter, carbonate is added to the filtrate to obtain lithium carbonate precipitation. The present application successively obtains sodium ferrous sulfate cathode material and lithium carbonate through the resource utilization method, efficiently recovers all available components in the lithium precipitate mother liquor, avoids the enrichment of sodium ions, has a high lithium-sodium separation rate, a high lithium recovery rate, a short process, and a high cost performance.

Description

Technical Field

[0001] The present application relates to the technical field of waste resource utilization, and specifically to a method for resource utilization of lithium precipitation mother liquor. Background Art

[0002] After calcination and transformation, spodumene reacts with sulfuric acid at high temperature (250°C) to leach lithium sulfate solution. The lithium sulfate reacts with excess soda ash to form lithium carbonate, which is filtered to obtain lithium carbonate and lithium precipitation mother liquor. The resulting lithium carbonate can be post-processed to produce battery-grade lithium carbonate. However, because lithium carbonate is slightly soluble, it can easily cause incomplete lithium precipitation, resulting in a certain amount of lithium ions in the precipitation mother liquor. The composition of the precipitation mother liquor is generally: pH 10-11, sodium content 40-60g / L, sulfate content 80-100g / L, lithium content 1-2g / L, and carbonate content 15-20g / L. If the lithium is not recovered, the lithium recovery rate will be reduced by about 8%. At the current price of 100,000 yuan / ton of lithium carbonate, the recovery of each ton of lithium carbonate will result in a loss of about 8,000 yuan. At an annual production of 10,000 tons, the loss is 80 million yuan.

[0003] Currently, the conventional treatment method for lithium precipitation mother liquor is: freeze crystallization, first heating and concentrating the lithium precipitation mother liquor to further increase the sodium content and reduce the volume, then cooling and crystallizing to obtain sodium sulfate decahydrate crystals, and returning the remaining mother liquor to leaching or precipitating lithium. However, this process is long, and there is also the problem of some sodium returning to the system, resulting in the continuous enrichment of sodium ions and the high sodium content in lithium carbonate. There are also some treatment methods, such as using ion exchange resins, adsorbents, and extractants to recover the lithium. These treatment methods have defects such as low lithium-sodium selectivity and low lithium adsorption / extraction rates, which can easily lead to problems such as low lithium recovery rate and excessive sodium adsorption rate. Summary of the Invention

[0004] In view of the technical problems existing in the background technology, the present application provides a method for resource utilization of lithium precipitation mother liquor, which aims to reduce the enrichment of sodium ions in the recovery treatment of lithium precipitation mother liquor and improve the lithium recovery rate.

[0005] In the first aspect, an embodiment of the present application provides a method for resource utilization of lithium precipitation mother liquor, comprising the following steps: adjusting the pH of the lithium precipitation mother liquor to acidic, adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source, and mixing them evenly to obtain a first slurry, and then drying, calcining and washing to obtain a sodium ferrous sulfate positive electrode material; wherein, the waste gas generated by the calcination is subjected to dust collection treatment to obtain a dust collection material, the dust collection material is mixed with water to obtain a second slurry, and the pH of the second slurry is adjusted to alkaline to obtain a filtrate through solid-liquid separation, and then, carbonate is added to the filtrate to obtain a lithium carbonate precipitate.

[0006] In the present application, sodium ferrous sulfate positive electrode material and lithium carbonate are obtained successively through the above-mentioned resource utilization method. On the one hand, all available components in the lithium precipitation mother liquor can be efficiently recovered. On the other hand, sodium is separated from the lithium precipitation mother liquor in the form of sodium ferrous sulfate, effectively avoiding the enrichment of sodium ions. At the same time, due to the presence of aluminum ions and chloride ions, low-boiling-point lithium aluminum chloride is generated, thereby volatilizing lithium, thereby realizing the recycling of lithium ions. Compared with other processes, the lithium-sodium separation rate is high, the lithium recovery rate is high, and the process is short.

[0007] In some embodiments, before the step of adjusting the pH of the lithium precipitation mother solution to acidic, the step further includes: detecting the concentration of each component in the lithium precipitation mother solution, the components including lithium, iron, sodium and sulfate.

[0008] In this embodiment, by detecting the concentration of the components, it is convenient to control the amount of the subsequently added sodium source, chloride ion source, ferrous source, aluminum source, reducing agent and carbon source to avoid waste of raw materials and increase process costs.

[0009] In some embodiments, in the first slurry, the molar ratio of sodium element, sulfate element, iron element, reducing agent and carbon element is (2.01~2.05): (2.01~2.05): 1: (0.05~0.1): (0.5~1); and / or, the molar ratio of aluminum element in the aluminum source to lithium element in the lithium precipitation mother liquor is (1.2~1.5): 1.

[0010] In this embodiment, the amount of each raw material is controlled so that the components contained in the lithium precipitation mother liquor are fully recycled and utilized. Among them, the sodium element and sulfate ion are slightly excessive relative to the iron element to ensure complete recovery of iron and effectively control costs. It is understandable that if the amount of reducing agent is too much, the purity of the obtained product will be affected. If the amount of reducing agent is too little, it cannot be guaranteed that all the iron elements are present in the form of ferrous ions. It is understandable that if the amount of carbon element is too little, an effective carbon coating layer cannot be formed. If the amount of carbon element is too much, the performance of the obtained sodium ferrous sulfate positive electrode material will be affected. Furthermore, by controlling the molar ratio of aluminum element in the aluminum source to lithium element in the lithium precipitation mother liquor to (1.2-1.5):1, the lithium is fully involved in the reaction, thereby improving the recovery rate.

[0011] In some embodiments, the step of adjusting the pH of the lithium precipitation mother liquor to acidic, adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source, and mixing them evenly to obtain a first slurry includes: adjusting the pH of the lithium precipitation mother liquor to 3-5; adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source to the lithium precipitation mother liquor to obtain a mixed slurry, and then adding a dispersant to the mixed slurry, and grinding and dispersing the mixed slurry until the particle size of the mixed slurry is 0.3-0.6 μm to obtain a first slurry.

[0012] In this embodiment, if the acidity of the lithium precipitation mother solution is too strong, it is not conducive to the reaction and is highly dangerous. If the acidity of the lithium precipitation mother solution is insufficient, Fe 2+ Unstable, therefore, this application adjusts the pH of the lithium precipitation mother liquor to 3-5, which is conducive to the stable existence of ferrous ions and the reaction, thereby improving the purity of the obtained sodium ferrous sulfate positive electrode material. At the same time, in the presence of a dispersant, the mixed slurry is ground and dispersed to uniformly disperse the raw materials. The particle size of the mixed slurry after grinding and dispersion is 0.3-0.6 μm. The mixed slurry in this particle size range is conducive to drying and is convenient for controlling the particle size of the dried material in the subsequent drying process.

[0013] In some embodiments, the sodium source includes at least one of sodium chloride or sodium sulfate; and / or, the aluminum source includes at least one of aluminum chloride or aluminum sulfate; and / or, the ferrous source includes at least one of ferrous chloride or ferrous sulfate; and / or, the reducing agent is at least one of hydrazine hydrate, sodium borohydride, and sodium sulfite; and / or, the carbon source includes an inorganic carbon source and an organic carbon source, wherein the inorganic carbon source is at least one of acetylene black and Ketjen black, and the organic carbon source includes glucose.

[0014] In this embodiment, a chloride ion source and a sulfate ion source are provided at the same time as a sodium source, a ferrous source and an aluminum source, so that no other impurity ions are introduced while generating the sodium ferrous sulfate positive electrode material and lithium aluminum chloride, which is beneficial to improving the purity of the recovered product.

[0015] In some embodiments, the drying is performed by spray drying, and the particle size of the spray material obtained by spray drying is 3 to 8 μm; and / or the calcining step comprises: under a protective atmosphere, heating the temperature to 350 to 450° C. at a heating rate of 1 to 2.5° C. / min and maintaining the temperature for 10 to 20 hours to obtain a calcined material; and / or the washing step comprises: cooling the calcined material, and then, under a protective atmosphere, crushing the calcined material to obtain a crushed material, and washing the crushed material multiple times with an organic solvent to obtain a sodium ferrous sulfate positive electrode material.

[0016] In this embodiment, by controlling the particle size of the spray material to 3 to 8 μm, it is beneficial to increase the specific surface area of ​​the prepared sodium ferrous sulfate positive electrode material, thereby increasing the tap density of the sodium ferrous sulfate positive electrode material after calcination. During the calcination process, if the calcination temperature is too high and the time is too long, the energy consumption is high and the structure of the sodium ferrous sulfate positive electrode material is affected. If the calcination temperature is too low and the time is too short, the binding force and density of the carbon coating layer and the sodium ferrous sulfate are reduced, which will affect the electrical properties of the sodium ferrous sulfate positive electrode material, and lithium cannot be fully volatilized. Therefore, this application controls the heating rate of calcination to 1 to 2.5 ° C / min and reacts at 350 to 450 ° C for 10 to 20 hours to ensure the generation of a sodium ferrous sulfate positive electrode material with a high compaction density, while completely volatilizing lithium in the form of lithium aluminum chloride to improve the lithium recovery rate. Thereafter, by using an organic solvent to wash the sodium ferrous sulfate positive electrode material, other impurities attached to the surface can be washed, while avoiding the high moisture content caused by the sodium ferrous sulfate positive electrode material absorbing water.

[0017] In some embodiments, the particle size of the pulverized material is 1-5 μm; and / or the organic solvent includes glycerol.

[0018] In this embodiment, if the particle size of the crushed material is too large, the specific surface area of ​​the obtained sodium ferrous sulfate positive electrode material is small, thereby reducing the battery capacity of the secondary battery prepared using the sodium ferrous sulfate positive electrode material. If the particle size of the crushed material is too small, hot spots are easily formed, resulting in high temperatures and thermal runaway inside the secondary battery prepared using the sodium ferrous sulfate positive electrode material. Therefore, the particle size of the crushed material is controlled to be 1-5 μm in this application to improve battery performance and life.

[0019] Furthermore, the use of organic solvent glycerol for washing can not only ensure that the moisture content of the sodium ferrous sulfate positive electrode material is low, but also facilitate the recovery and reuse of glycerol.

[0020] In some embodiments, the pH of the second slurry is adjusted to 10-12; and / or the mass ratio of the dust collecting material to water is 1:(5-8); and / or the molar ratio of carbonate to lithium in the filtrate is 1:(0.7-0.8).

[0021] In this embodiment, if the alkalinity of the second slurry is too strong, lithium hydroxide will be generated, and then a supersaturated solution of lithium hydroxide will be formed. The supersaturated lithium hydroxide will precipitate, resulting in lithium loss. If the alkalinity of the second slurry is insufficient, the aluminum will not be completely precipitated, reducing the purity of the lithium carbonate. Therefore, the present application adjusts the pH of the second slurry to 10-12 to ensure that the aluminum is completely precipitated and recovered while avoiding lithium loss. Furthermore, by controlling the mass ratio of the dust collecting material to water to 1: (5-8), the lithium leaching rate is increased and its concentration is guaranteed, which is conducive to the subsequent generation and recovery of lithium carbonate.

[0022] Furthermore, by adjusting the molar ratio of carbonate to lithium in the filtrate to 1:(0.7-0.8), the lithium can be completely precipitated as much as possible while controlling the cost, and the lithium can be fully recovered.

[0023] In some embodiments, a drying step is further included after washing, and the drying step is oven drying. The drying step specifically includes: introducing nitrogen into the oven at a drying temperature of 200-300°C until the oxygen content in the oven is less than 500ppm, and drying the sodium ferrous sulfate positive electrode material until the mass fraction of the detergent contained in the sodium ferrous sulfate positive electrode material is ≤0.2%.

[0024] In this embodiment, the sodium ferrous sulfate positive electrode material is dried to ensure its moisture content, thereby preventing excessive moisture content from affecting the performance of the positive electrode material.

[0025] In some embodiments, residual waste gas is also included after the dust collection process, and the residual waste gas is discharged after being sprayed and absorbed.

[0026] In this embodiment, the remaining waste gas is sprayed and absorbed so that it meets the emission standards, which is beneficial to environmental protection.

[0027] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0029] Figure 1 This is a SEM image of the spray-dried material obtained in Example 1 of the present application;

[0030] Figure 2 This is an SEM image of the sodium ferrous sulfate positive electrode material obtained in Example 1 of the present application;

[0031] Figure 3 This is a charge and discharge curve diagram of a button-type battery assembled with the sodium ferrous sulfate positive electrode material obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0032] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0034] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0035] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0036] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0037] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0038] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0039] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0040] At present, the conventional treatment method for lithium precipitate mother liquor is freeze crystallization, that is, the lithium precipitate mother liquor is first heated and concentrated, and then cooled and crystallized; however, the conventional process has the defects of high energy consumption and long process, and there is also the problem that some sodium is returned to the system, resulting in continuous enrichment of sodium ions and a high sodium content in lithium carbonate. Other processes such as using ion exchange resins, adsorbents, extractants, etc. to recover lithium therein have defects such as low lithium-sodium selectivity and low lithium adsorption / extraction rate, resulting in low lithium recovery rate and too high sodium adsorption rate. Therefore, conventional treatment methods have the problem of being unable to achieve the recycling and reuse of all components in the above-mentioned lithium precipitate mother liquor, or the existence of the generated material added value is very low, resulting in low cost-effectiveness of the recycling and treatment of the lithium precipitate mother liquor.

[0041] In order to solve the technical problem of high sodium content and low lithium recovery rate caused by continuous enrichment of sodium in the recovery and treatment of lithium precipitation mother liquor, the present application provides a method for resource utilization of lithium precipitation mother liquor, wherein the present application adopts an aqueous solution method-calcination process to prepare a sodium ferrous sulfate positive electrode material. The calcination process can be used to synthesize the sodium ferrous sulfate positive electrode material and the lithium can be volatilized by a low volatility method; the present application obtains sodium ferrous sulfate positive electrode material and lithium carbonate in succession through the above-mentioned resource utilization method, and can efficiently and cost-effectively recover all available components in the lithium precipitation mother liquor, and the sodium therein is separated from the lithium precipitation mother liquor in the form of sodium ferrous sulfate, effectively avoiding the enrichment of sodium ions. Compared with other processes, the lithium-sodium separation rate is high, the lithium recovery rate is high, and the process is short.

[0042] In the first aspect, an embodiment of the present application provides a method for resource utilization of lithium precipitation mother liquor, comprising the following steps: adjusting the pH of the lithium precipitation mother liquor to acidic, adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source, and mixing them evenly to obtain a first slurry, and then drying, calcining and washing to obtain a sodium ferrous sulfate positive electrode material; wherein, the waste gas generated by the calcination is subjected to dust collection treatment to obtain a dust collection material, the dust collection material is mixed with water to obtain a second slurry, and the pH of the second slurry is adjusted to alkaline to obtain a filtrate through solid-liquid separation, and then, carbonate is added to the filtrate to obtain lithium carbonate precipitate.

[0043] In this application, a sodium ferrous sulfate positive electrode material is first prepared. Sodium ferrous sulfate positive electrode material is a sodium battery positive electrode material. It has the advantages of high voltage (3.8V) and high capacity. The market price can reach more than 30,000 yuan, which is more than ten times higher than the price of sodium sulfate. It can effectively increase the added value of resource utilization. In the sintering process, the sodium ferrous sulfate positive electrode material is sintered. At the same time, due to the coexistence of aluminum ions and chloride ions, low-boiling-point lithium aluminum chloride will be volatilized, and the lithium in it can be recovered, thereby effectively reducing costs.

[0044] The sodium ferrous sulfate positive electrode material prepared in the present application is prepared by using an aqueous solution, and ferrous ions, sulfate ions, and sodium ions are mixed and dissolved, and then spray-dried. This allows the different elements of the synthesized sodium ferrous sulfate positive electrode material to be evenly mixed at the ionic level, thereby making the ion diffusion distance of the sodium ferrous sulfate positive electrode material shorter and the reaction activity higher during high-temperature calcination. The density and compaction density of the prepared sodium ferrous sulfate positive electrode material are higher than those of other processes. At the same time, a carbon source is introduced for carbon coating, and the carbon has high conductivity, so that the electrochemical performance of the prepared sodium ferrous sulfate positive electrode material is also relatively excellent.

[0045] Furthermore, in some embodiments, before the step of adjusting the pH of the lithium precipitation mother solution to acidity, the step further includes: detecting the concentration of each component in the lithium precipitation mother solution, the components including lithium, iron, sodium and sulfate.

[0046] In the technical solution of the embodiment of the present application, the amount of other raw materials added can be controlled by detecting the concentration of the components.

[0047] Furthermore, in some embodiments, in the first slurry, the molar ratio of sodium, sulfate, iron, reducing agent and carbon is (2.01-2.05): (2.01-2.05): 1: (0.05-0.1): (0.5-1); and / or the molar ratio of aluminum in the aluminum source to lithium in the lithium precipitation mother solution is (1.2-1.5): 1.

[0048] In this application, the components contained in the lithium precipitation mother liquor are fully recycled by controlling the amount of each raw material. Among them, the iron element in the first slurry is mainly the added ferrous ion, and the lithium precipitation mother liquor itself contains a small amount of Fe 3+ , this application adds an appropriate amount of reducing agent (the amount can be based on Fe 3+The content is appropriately increased or decreased), and it is reduced to ferrous ions, which can improve the purity of the prepared sodium ferrous sulfate positive electrode material. Among them, the sodium element and sulfate ion are slightly excessive relative to the iron element, ensuring the complete recovery of iron and effectively controlling the cost. If the amount of reducing agent is too much, it will affect the purity of the obtained product. If the amount of reducing agent is too little, it cannot be guaranteed that all the iron elements exist in the form of ferrous ions. If the amount of carbon element is too little, an effective carbon coating layer cannot be formed. If the amount of carbon element is too much, it will affect the performance of the obtained sodium ferrous sulfate positive electrode material. Furthermore, in the present application, by controlling the molar ratio of the aluminum element in the aluminum source to the lithium element in the lithium precipitation mother liquor to (1.2 to 1.5): 1, the lithium is fully involved in the reaction, thereby improving the recovery rate.

[0049] Specifically, the molar ratio of sodium element, sulfate element, iron element, reducing agent and carbon element in the first slurry can be 2.01:2.01:1:0.05:0.5, 2.02:2.02:1:0.06:0.5, 2.03:2.03:1:0.08:0.5, 2.03:2.03:1:0.08:0.8, 2.05:2.05:1:0.1:1 or any value between (2.01~2.05):(2.01~2.05):1:(0.05~0.1):(0.5~1); the molar ratio of aluminum element in the aluminum source to lithium element in the lithium precipitation mother liquor is 1.2:1, 1.3:1, 1.4:1, 1.5:1 or any value between (1.2~1.5):1.

[0050] Furthermore, in some embodiments, the step of adjusting the pH of the lithium precipitation mother liquor to acidic, adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source, and mixing them evenly to obtain a first slurry includes: adjusting the pH of the lithium precipitation mother liquor to 3-5; adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source to the lithium precipitation mother liquor to obtain a mixed slurry, and then adding a dispersant to the mixed slurry, and grinding and dispersing the mixed slurry until the particle size of the mixed slurry is 0.3-0.6 μm to obtain a first slurry.

[0051] In the technical solution of the embodiment of the present application, if the acidity of the lithium precipitation mother solution is too strong, it is not conducive to the reaction and is highly dangerous. If the acidity of the lithium precipitation mother solution is insufficient, Fe 2+ It is unstable, so the present application adjusts the pH of the lithium precipitation mother liquor to 3-5, which is conducive to the stable existence of ferrous ions and the reaction, thereby improving the purity of the obtained sodium ferrous sulfate positive electrode material; at the same time, in the presence of a dispersant, the mixed slurry is ground and dispersed to make the raw materials evenly dispersed. The particle size of the mixed slurry after grinding and dispersion is 0.3-0.6μm. The mixed slurry in this particle size range is conducive to drying and facilitates the control of the particle size of the dried material in the subsequent drying process. The particle sizes mentioned in this application are all average particle sizes.

[0052] Specifically, the pH of the lithium precipitation mother solution is adjusted to 3, 3.5, 4, 4.5, 5 or any value between 3 and 5; the particle size of the mixed slurry can be 0.3 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.6 μm or any value between 0.3 and 0.6 μm.

[0053] Furthermore, in some embodiments, acetic acid is used to adjust the pH of the lithium precipitation mother solution to 3-5.

[0054] In the technical solution of the embodiment of the present application, acetic acid is used to adjust the pH value of the lithium precipitation mother liquor, which will not introduce impurity ions and is conducive to improving the purity of the recovered product.

[0055] Furthermore, in some embodiments, the dispersant is at least one of polyethylene glycol and polyacrylic acid, and the amount of the dispersant added is 0.3-0.4% of the mass of the first slurry. For example, the amount of the dispersant added can be 0.3%, 0.32%, 0.35%, 0.38%, 0.4% or any value between 0.3% and 0.4%.

[0056] Further, in some embodiments, the sodium source includes at least one of sodium chloride or sodium sulfate; and / or, the aluminum source includes at least one of aluminum chloride or aluminum sulfate; and / or, the ferrous source includes at least one of ferrous chloride or ferrous sulfate; and / or, the reducing agent is at least one of hydrazine hydrate, sodium borohydride, and sodium sulfite; and / or, the carbon source includes an inorganic carbon source and an organic carbon source, wherein the inorganic carbon source is at least one of acetylene black and Ketjen black, and the organic carbon source includes glucose.

[0057] In the technical solution of the embodiment of the present application, no other impurity ions are introduced while generating the sodium ferrous sulfate positive electrode material and lithium aluminum chloride, which is beneficial to improving the purity of the recovered product.

[0058] Furthermore, in some embodiments, the drying is performed by spray drying, and the particle size of the spray material obtained by spray drying is 3 to 8 μm; and / or the calcining step comprises: under a protective atmosphere, heating the temperature to 350 to 450° C. at a heating rate of 1 to 2.5° C. / min and maintaining the temperature for 10 to 20 hours to obtain a calcined material; and / or the washing step comprises: cooling the calcined material, and then, under a protective atmosphere, crushing the calcined material to obtain a crushed material, and washing the crushed material multiple times with an organic solvent to obtain a sodium ferrous sulfate positive electrode material.

[0059] In the technical solution of the embodiment of the present application, by controlling the particle size of the spray material to 3 to 8 μm, it is beneficial to increase the specific surface area of ​​the obtained sodium ferrous sulfate cathode material and increase the tap density. Among them, if the calcination temperature is too high and the time is too long, the energy consumption is high and the structure of the sodium ferrous sulfate cathode material is affected. If the calcination temperature is too low and the time is too short, the binding force and density of the carbon coating layer and the sodium ferrous sulfate are reduced, which will affect the electrochemical properties of the sodium ferrous sulfate cathode material, and lithium cannot be fully volatilized. Therefore, the present application controls the heating rate of calcination to 1 to 2.5 ° C / min and maintains the reaction at 350 to 450 ° C for 10 to 20 hours to ensure the generation of a sodium ferrous sulfate cathode material with a high compaction density. At the same time, the lithium is completely volatilized in the form of lithium aluminum chloride to improve the lithium recovery rate.

[0060] Furthermore, in the present application, by using an organic solvent to wash the sodium ferrous sulfate positive electrode material, other impurities can be washed away, while at the same time avoiding high moisture content caused by the sodium ferrous sulfate positive electrode material absorbing water.

[0061] Specifically, in the calcination step, the heating rate can be 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min or any value between 1 and 2.5; the holding temperature can be 350°C, 360°C, 380°C, 400°C, 410°C, 420°C, 430°C or any value between 350 and 450°C; and the holding time can be 10h, 12h, 13h, 14h, 15h, 16h, 18h, 20h or any value between 10 and 20h.

[0062] Furthermore, in some embodiments, during the calcination step, nitrogen is used as a protective atmosphere, and nitrogen is introduced until the oxygen content in the calcination atmosphere is less than 2 ppm and the humidity is ≤3.5%; the calcined material is cooled to a temperature ≤100°C and then discharged.

[0063] Furthermore, in some embodiments, the particle size of the crushed material is 1-5 μm; and / or the organic solvent includes glycerol, and the washing times are multiple times.

[0064] In the technical solution of the embodiment of the present application, if the particle size of the crushed material is too large, the impurities cannot be fully washed and removed, and the specific surface area of ​​the obtained sodium ferrous sulfate positive electrode material is small, thereby reducing the battery capacity of the secondary battery prepared using the sodium ferrous sulfate positive electrode material. If the particle size of the crushed material is too small, it is difficult to separate after washing, and it is easy to form hot spots, resulting in high temperature and thermal runaway inside the secondary battery prepared using the sodium ferrous sulfate positive electrode material. Furthermore, in the present application, the organic solvent glycerol is used for washing, which can not only ensure that the moisture content of the sodium ferrous sulfate positive electrode material is low, but also facilitate the recycling and reuse of glycerol.

[0065] Specifically, the particle size of the crushed material can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 2.7 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or any value between 1 and 5 μm.

[0066] Furthermore, in some embodiments, the crushed material is washed twice with an organic solvent. During the first wash, the mass ratio of the crushed material to glycerin is 1:(3-5), the washing temperature is 50-80°C, and the washing and stirring time is 1-2 hours. The material is then filtered to obtain a primary washed material. During the second wash, the mass ratio of the primary washed material to glycerin is 1:(1-2), the washing temperature is 50-80°C, and the washing and stirring time is 1-2 hours. The material is then filtered to obtain a secondary washed material, i.e., the washed crushed material. In this application, the washed glycerin can be recovered and recycled by distillation.

[0067] Specifically, during the first washing, the mass ratio of the crushed material to the glycerol can be 1:3, 1:3.5, 1:4, 1:4.5, 1:5 or any value between 1:(3-5); during the second washing, the mass ratio of the primary washing material to the glycerol can be 1:1, 1:1.5, 1:2 or any value between 1:(1-2); the washing temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any value between 50-80°C, and the washing time can be 1h, 1.5h, 2h or any value between 1-2h.

[0068] Furthermore, in some embodiments, the pH of the second slurry is adjusted to 10-12; and / or the mass ratio of the dust collecting material to water is 1:(5-8); and / or the molar ratio of carbonate to lithium in the filtrate is 1:(0.7-0.8).

[0069] In the present application, if the alkalinity of the second slurry is too strong, lithium hydroxide will be generated, and then a supersaturated lithium hydroxide solution will be formed. The supersaturated lithium hydroxide will precipitate, resulting in lithium loss. If the alkalinity of the second slurry is insufficient, the aluminum will not be completely precipitated, reducing the purity of the lithium carbonate. Therefore, the present application adjusts the pH of the second slurry to 10-12 to ensure that the aluminum is completely precipitated and recovered while avoiding lithium loss. Furthermore, by controlling the mass ratio of the dust collection material to water to 1: (5-8), the lithium leaching rate is increased and its concentration is guaranteed, which is conducive to the subsequent generation and recovery of lithium carbonate. Furthermore, by adjusting the molar ratio of carbonate to lithium in the filtrate to 1: (0.7-0.8), while controlling costs, the lithium is completely precipitated as much as possible and the lithium is completely recovered.

[0070] Specifically, the pH of the second slurry can be 10, 11, 12 or any value between 10 and 12; the mass ratio of the dust collecting material to water can be 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8 or any value between 1:(5 and 8); the molar ratio of carbonate to lithium in the filtrate can be 1:0.7, 1:0.72, 1:0.74, 1:0.75, 1:0.76, 1:0.78, 1:0.8 or any value between 1:(0.7 and 0.8).

[0071] Furthermore, in some embodiments, the pH of the second slurry is adjusted to 10-12 using sodium hydroxide solution, the temperature of the second slurry is 50-80° C. when the sodium hydroxide solution is added, and the addition time of the sodium hydroxide solution is 15-45 minutes. After the sodium hydroxide solution is added, the reaction is stirred for 10-30 minutes, and then a filtrate and aluminum hydroxide precipitate are obtained by solid-liquid separation.

[0072] Specifically, the temperature of the second slurry when the sodium hydroxide solution is added can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any value between 50 and 80°C, and the addition time of the sodium hydroxide solution can be 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min or any value between 15 and 45 min; the stirring reaction time can be 10 min, 15 min, 20 min, 25 min, 30 min or any value between 10 and 30 min.

[0073] Furthermore, in some embodiments, carbonate is added to the filtrate, the reaction temperature is 80-90°C, and lithium carbonate can be obtained through precipitation. After the precipitation no longer increases, lithium carbonate precipitate and residual filtrate are obtained through separation, and the residual filtrate is recycled and added to the lithium precipitation mother liquor; wherein the carbonate includes sodium carbonate.

[0074] Specifically, the reaction temperature for adding carbonate to the filtrate can be 80°C, 85°C, 90°C or any value between 80 and 90°C.

[0075] In the present application, the remaining filtrate after separating the lithium carbonate precipitate contains sodium salt and a small amount of unprecipitated lithium salt, which are returned for reuse to improve the raw material utilization rate and lithium recovery rate.

[0076] Furthermore, in some embodiments, a drying step is included after washing, and the drying step is oven drying. The drying step specifically includes: introducing nitrogen into the oven at a drying temperature of 200-300°C until the oxygen content in the oven is less than 500ppm, and drying the sodium ferrous sulfate positive electrode material until the mass fraction of the detergent contained in the sodium ferrous sulfate positive electrode material is ≤0.2%.

[0077] Specifically, the drying temperature can be 200° C., 220° C., 240° C., 250° C., 255° C., 260° C., 280° C., 300° C., or any value between 200° C. and 300° C. In the present application, the sodium ferrous sulfate positive electrode material is dried to ensure its moisture content, thereby preventing excessive moisture content from affecting the performance of the positive electrode material.

[0078] Furthermore, in some embodiments, the sodium ferrous sulfate positive electrode material is dried and then screened, deironed, and packaged in a constant temperature and humidity room.

[0079] Furthermore, in some embodiments, residual waste gas is also included after the dust collection process, and the residual waste gas is discharged after being sprayed and absorbed.

[0080] In the technical solution of the embodiment of the present application, the remaining waste gas is sprayed and absorbed so that it meets the emission standards, which is beneficial to environmental protection.

[0081] Furthermore, in some embodiments, the step of collecting dust materials specifically includes: drawing out the exhaust gas generated during the calcination process through an induced draft fan, then using a heat exchanger to reduce the temperature of the exhaust gas to 150-200° C., and collecting dust through a bag dust collector.

[0082] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0083] 1. Resource Utilization Methods

[0084] Example 1

[0085] S1. Measure the concentrations of lithium, iron, sodium and sulfate in the lithium precipitation mother liquor; add acetic acid to the lithium precipitation mother liquor to adjust the pH to 4.3, then add 2 mol / L ferrous sulfate solution, industrial grade sodium chloride, industrial grade aluminum chloride, hydrazine hydrate solution, and then add acetylene black, stir and mix evenly to obtain a mixed slurry, then add 0.4 mm corundum grinding balls to the mixed slurry, grind and disperse the acetylene black, and add polyethylene glycol 6000 at the same time, grind until the average solid particle size in the mixed slurry is 0.45 μm to obtain a first slurry; wherein the molar ratio of sodium, sulfate, iron, hydrazine hydrate and carbon in the first slurry is 2.03:2.03:1:0.08:0.8, the molar ratio of the added aluminum chloride to the lithium in the lithium precipitation mother liquor is 1.4:1, and the added polyethylene glycol 6000 is 0.35% of the mass of the first slurry.

[0086] The first slurry was spray-dried, and the average particle size of the prepared spray-dried material was controlled to be 5.6 μm and the free water content was 0.35 wt%. Subsequently, the spray-dried material was placed in a roller furnace for calcination at a heating rate of 2 ° C / min to 420 ° C. The reaction was carried out at this temperature for 15 hours, and nitrogen was introduced at the same time to make the oxygen content in the atmosphere of the roller furnace less than 2 ppm and the humidity ≤ 3.5%. After calcination, the material was cooled to a material temperature of ≤ 100 ° C and then discharged, and then pulverized under nitrogen protection to a particle size of 2.7 μm. Glycerol was added for the first washing, the mass ratio of the crushed material to glycerol was 1:4, the mixture was stirred and mixed at a temperature of 70°C for 1.5 hours, then filtered, and glycerol 1.5 times the mass of the crushed material was added for the second washing. The washed material was placed in an oven for drying, and nitrogen protection was introduced to make the oxygen content in the oven less than 500ppm. At the same time, the drying temperature was 255°C. The drying was stopped after the mass fraction of glycerol in the material was ≤0.2%. The dried material was sieved, deironed and packaged in a constant temperature and humidity room to obtain sodium ferrous sulfate positive electrode material.

[0087] Among them, the exhaust gas generated by calcination is led out by the induced draft fan, and the exhaust gas temperature is reduced to 180°C by a heat exchanger. After the dust is collected by the bag dust collector, the remaining exhaust gas is sprayed and absorbed and then discharged to collect the dust collection material; the glycerin after slurrying and washing is distilled, and the glycerin is distilled out and recycled, and the remaining sodium chloride is returned for use.

[0088] S2. Pure water was added to the collected dust collecting material, the mass ratio of the dust collecting material to pure water was 1:7, and a second slurry was obtained by stirring. Then, 8 mol / L sodium hydroxide solution was added to adjust the pH of the second slurry to 10.5. The sodium hydroxide solution was added for 30 min. At the same time, the temperature of the second slurry was maintained at 60±2°C during the addition process. After the sodium hydroxide solution was added, the reaction was stirred for 20 min and then filtered to obtain an aluminum hydroxide precipitate and a filtrate.

[0089] Industrial-grade sodium carbonate is added to the above filtrate, with a molar ratio of the added sodium carbonate to the lithium in the filtrate being 1:0.75. The reaction temperature is 85°C, and lithium carbonate is precipitated. The remaining filtrate contains sodium salt and a small amount of unprecipitated lithium salt, which can be returned to step S1 and combined with the lithium precipitation mother liquor for reuse.

[0090] Example 2

[0091] The only difference from Example 1 is that the molar ratio of the added aluminum chloride to the lithium in the lithium precipitation mother liquor is 1.2:1, and the other steps and conditions are the same as those in Example 1.

[0092] Example 3

[0093] The only difference from Example 1 is that the molar ratio of the added aluminum chloride to the lithium in the lithium precipitation mother liquor is 1.5:1, and the other steps and conditions are the same as those in Example 1.

[0094] Example 4

[0095] The only difference from Example 1 is that acetic acid is added to the lithium precipitation mother liquor to adjust the pH to 5.0. Other steps and conditions are the same as those in Example 1.

[0096] Example 5

[0097] The only difference from Example 1 is that acetic acid is added to the lithium precipitation mother liquor to adjust the pH to 3.0. The other steps and conditions are the same as those in Example 1.

[0098] Comparative Example 1

[0099] The only difference from Example 1 is that the molar ratio of the added aluminum chloride to the lithium in the lithium precipitation mother liquor is 1:1, and the other steps and conditions are the same as those in Example 1.

[0100] Comparative Example 2

[0101] The only difference from Example 1 is that the molar ratio of the added aluminum chloride to the lithium in the lithium precipitation mother liquor is 2:1, and the other steps and conditions are the same as those in Example 1.

[0102] Comparative Example 3

[0103] The only difference from Example 1 is that acetic acid is added to the lithium precipitation mother liquor to adjust the pH to 6.0. The other steps and conditions are the same as those in Example 1.

[0104] 2. Test Method

[0105] 1. Performance test of sodium ferrous sulfate positive electrode material

[0106] The sodium ferrous sulfate obtained in Examples 1-5 and Comparative Examples 1-3 was subjected to performance tests, wherein: the determination of element content was carried out according to the method specified in HG / T 4701-2021; the determination of particle size was carried out according to the method specified in GB / T 19077-2016; the determination of magnetic foreign matter was carried out according to the method specified in HG / T 4701-2021; the determination of bulk density was carried out according to the method specified in GB / T 31057.1-2014; the determination of tap density was carried out according to the national standard GB / T 5162; the determination of compacted density was carried out according to the method specified in GB / T 24533-2019; the determination of specific surface area was carried out according to the method specified in GB / T 19587; the determination of moisture content was carried out according to the method specified in GB / T 6283; the determination of powder resistivity was carried out according to the method specified in GB / T 40007-2021; the determination of acid insoluble matter was carried out according to the method specified in GB / T 23834.2-2009.

[0107] Among them, the detection method of iron dissolution specifically includes: adding 1 mL of 10 mol / L hydrogen fluoride solution to 100 mL of anhydrous alcohol, mixing and stirring evenly, and then keeping the temperature constant at 25°C. Under this condition, 10 g of sodium ferrous sulfate positive electrode material is added, stirred and mixed for 30 minutes, and then filtered. The obtained filtrate is fixed to 250 mL, and the iron therein is measured using an inductively coupled plasma optical emission spectrometer (ICP-OES) to obtain the iron dissolution data.

[0108] 2. Property test of sodium ferrous sulfate positive electrode material: The sodium ferrous sulfate positive electrode material obtained in this application is assembled into a button battery. The specific assembly process includes: mixing the above-mentioned sodium ferrous sulfate positive electrode material, conductive carbon black (SP) and polyvinylidene fluoride (PVDF), coating it on aluminum foil, and drying it to obtain the positive electrode sheet of the sodium ion battery, wherein the mass ratio of the sodium ferrous sulfate positive electrode material, conductive carbon black and PVDF is 95:2.5:2.5. Subsequently, metallic sodium is used as the counter electrode, glass fiber is used as the separator, and 1 mol / L NaPF6 ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio of 1:1) solution is used as the electrolyte. The positive electrode sheet, sodium sheet, separator, gasket and spring are placed in the button battery to assemble into a CR2032 button battery.

[0109] 3. Analysis of test results of various embodiments and comparative examples

[0110] 1. The spray-dried material and the sodium ferrous sulfate cathode material obtained in Example 1 were respectively subjected to electron microscope scanning, wherein the SEM of the spray-dried material is as follows: Figure 1 As shown, from Figure 1 It can be seen that the spray-dried material includes spherical and quasi-spherical particles; the SEM of the sodium ferrous sulfate cathode material is as follows: Figure 2 As shown, from Figure 2 It can be seen that the sodium ferrous sulfate positive electrode material prepared in the present application includes large spherical particles and irregular small particles, and the particle size of the irregular small particles is between 50 and 300 nm, and they are evenly filled between the large spherical particles, thereby effectively increasing the specific surface area and tap density.

[0111] 2. In Example 1, the contents of lithium, iron, sodium and sulfate in the lithium precipitation mother liquor were tested, and the test results are shown in the following table.

[0112] Table 1 Component detection data of lithium precipitation mother liquor

[0113]

[0114] Furthermore, the test results of the sodium ferrous sulfate positive electrode material prepared in Example 1 are shown in the following table.

[0115] Table 2 Test data of sodium ferrous sulfate positive electrode material

[0116]

[0117] As shown in Table 2, the specific surface area of ​​the sodium ferrous sulfate cathode material prepared in this application is 7.48 m 2 / g; the iron dissolution amount is 157ppm, which is extremely low.

[0118] Furthermore, the test data of the aluminum hydroxide prepared in Example 1 are shown in the following table.

[0119] Table 3 Detection data of aluminum hydroxide

[0120]

[0121] Furthermore, the test data of the lithium carbonate prepared in Example 1 are shown in the following table.

[0122] Table 4 Detection data of lithium carbonate

[0123]

[0124] Combined with the component content in the lithium precipitation mother liquor and the amount of each substance recovered, comprehensive calculation shows that through the method of the present application, the comprehensive recovery rate of lithium in the lithium precipitation mother liquor can reach 95%, and the comprehensive recovery rate of sulfate and sodium ions can reach 98%. At the same time, in the process of preparing sodium ferrous sulfate positive electrode material, the present application does not require additional water to be added, which reduces water consumption and makes the process more green and environmentally friendly.

[0125] Furthermore, the recovery rates of the main substances in Examples 1-5 and Comparative Examples 1-3 were statistically analyzed, and the results are shown in Table 5 below.

[0126] Table 5 Recovery rates of major substances in the examples and comparative examples

[0127]

[0128] As can be seen from Table 5, the recovery rates of Examples 1-5 are significantly higher than those in Comparative Examples 1-3, and the recovery rate of Example 1 is better than that of the other four groups of examples. Among them, the molar ratio of aluminum chloride added to the lithium in the lithium precipitation mother liquor in Comparative Example 2 is 2:1, which is much larger than the (1.2~1.5) : 1 set in this application. Due to the excessive addition of aluminum chloride, the recovery rate of lithium in Comparative Example 2 is not significantly different from that in Examples 1-5. The molar ratio of aluminum chloride added to the lithium in the lithium precipitation mother liquor in Comparative Example 1 is 1:1, which is lower than the (1.2~1.5) : 1 set in this application. Due to the reduced amount of aluminum chloride added, the recovery rate of lithium in Comparative Example 1 is significantly reduced. Therefore, in this application, by setting the molar ratio of aluminum chloride to lithium in the lithium precipitation mother liquor to (1.2~1.5) : 1, it is possible to achieve effective recovery of lithium ions in the lithium precipitation mother liquor while saving raw materials.

[0129] Furthermore, according to the fact that the recovery rates of various substances in Comparative Example 3 are lower than the recovery rates of various substances in Example 1, it is explained that the change in the pH value of the lithium precipitation mother liquor will have a significant impact on the recovery rates of various substances.

[0130] 3. The sodium ferrous sulfate positive electrode material prepared in Example 1 of the present application was used to prepare a positive electrode sheet. Thereafter, the prepared positive electrode sheet was used to assemble a button battery, and the charge and discharge capacity of the button battery was measured under 0.1C, 0.5C, 1C and 10C conditions. The results are shown in the following table and Figure 3 shown.

[0131] Table 6 Test data of button cells assembled with sodium ferrous sulfate cathode material

[0132]

[0133] As shown in Table 6, the button cell prepared using the sodium ferrous sulfate positive electrode material in Example 1 has excellent electrochemical performance.

[0134] Specifically, the charge and discharge curves of button batteries are as follows: Figure 3 As shown, from Figure 3 It can be seen from the data that the secondary battery prepared using the sodium ferrous sulfate positive electrode material of the present application has a high capacity and excellent rate performance.

[0135] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for resource utilization of lithium precipitation mother liquor, characterized in that: The following steps are involved: Adjusting the pH of the lithium precipitation mother solution to 3-5, adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source, and mixing them uniformly to obtain a first slurry, wherein the particle size of the first slurry is 0.3-0.6 μm, and then drying, calcining and washing to obtain a sodium ferrous sulfate positive electrode material; The calcination temperature is 350-450° C., the calcination time is 10-20 hours, the waste gas generated by the calcination is subjected to dust collection treatment to obtain a dust collection material, the dust collection material is mixed with water to obtain a second slurry, and the pH of the second slurry is adjusted to 10-12 to obtain a filtrate through solid-liquid separation, and then carbonate is added to the filtrate to obtain lithium carbonate precipitate; In the first slurry, the molar ratio of sodium element, sulfate, iron element, reducing agent and carbon element is (2.01-2.05): (2.01-2.05): 1: (0.05-0.1): (0.5-1); The molar ratio of the aluminum element in the aluminum source to the lithium element in the lithium precipitation mother solution is (1.2-1.5):

1.

2. The method for resource utilization of lithium precipitation mother liquor according to claim 1, characterized in that: Before the step of adjusting the pH of the lithium precipitation mother solution to acidity, the method further comprises: The concentration of each component in the lithium precipitation mother solution is detected, and the components include lithium, iron, sodium and sulfate.

3. The method for resource utilization of lithium precipitation mother liquor according to claim 1, characterized in that: The step of adjusting the pH of the lithium precipitation mother solution to acidic, adding a sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source, and mixing them uniformly to obtain a first slurry comprises: Adjusting the pH of the lithium precipitation mother solution to 3-5; A sodium source, a chloride ion source, a ferrous source, an aluminum source, a reducing agent and a carbon source are added to the lithium precipitation mother liquor to obtain a mixed slurry. Thereafter, a dispersant is added to the mixed slurry, and the mixed slurry is ground and dispersed until the particle size of the mixed slurry is 0.3 to 0.6 μm to obtain the first slurry.

4. The method for resource utilization of lithium precipitation mother liquor according to claim 3, characterized in that: The sodium source comprises at least one of sodium chloride or sodium sulfate; and / or, The aluminum source comprises at least one of aluminum chloride or aluminum sulfate; and / or, The ferrous source includes at least one of ferrous chloride or ferrous sulfate; and / or, The reducing agent is at least one of hydrazine hydrate, sodium borohydride, and sodium sulfite; and / or, The carbon source includes an inorganic carbon source and an organic carbon source, wherein the inorganic carbon source is at least one of acetylene black and Ketjen black, and the organic carbon source includes glucose.

5. The method for resource utilization of lithium precipitation mother liquor according to claim 1, characterized in that: The drying is carried out by spray drying, and the particle size of the spray material obtained by the spray drying is 3 to 8 μm; and / or The calcining step comprises: heating to 350-450° C. at a heating rate of 1-2.5° C. / min under a protective atmosphere and maintaining the temperature for 10-20 hours to obtain a calcined material; and / or, The washing step includes: cooling the calcined material, then crushing the calcined material under a protective atmosphere to obtain a crushed material, and washing the crushed material multiple times with an organic solvent to obtain a sodium ferrous sulfate positive electrode material.

6. The method for resource utilization of lithium precipitation mother liquor according to claim 5, characterized in that: The particle size of the crushed material is 1-5 μm; and / or the organic solvent includes glycerol.

7. The method for resource utilization of lithium precipitation mother liquor according to claim 1, characterized in that: The mass ratio of the dust collecting material to water is 1:(5-8); and / or The molar ratio of the carbonate to the lithium in the filtrate is 1:(0.7-0.8).

8. The method for resource utilization of lithium precipitation mother liquor according to claim 1, characterized in that: After washing, a drying step is also included, and the drying is oven drying. The drying step specifically includes: introducing nitrogen into the oven at a drying temperature of 200-300°C until the oxygen content in the oven is less than 500ppm, and drying the sodium ferrous sulfate positive electrode material until the mass fraction of the detergent contained in the sodium ferrous sulfate positive electrode material is ≤0.2%.

9. The method for resource utilization of lithium precipitation mother liquor according to claim 1, characterized in that: After the dust collection process, there is also residual waste gas, which is discharged after being sprayed and absorbed.

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