Method for preparing lithium salt by recycling ternary black powder

Abstract

The invention provides a method for recovering ternary black powder to prepare lithium salt, which comprises the following steps: S1, adding a reducing agent into the ternary black powder for roasting treatment to obtain roasted black powder; s2, adding water into the roasted black powder for water leaching treatment, and filtering to obtain a saturated lithium carbonate aqueous solution and an insoluble solid; s3, inorganic acid is added into the saturated lithium carbonate aqueous solution until the pH is 6.5-7, and a lithium salt aqueous solution is obtained; s4, the lithium elution rate n of the step S2 is obtained, and according to the lithium elution rate n, it is determined that insoluble solids are subjected to washing treatment, or it is determined that the insoluble solids are continuously subjected to water immersion treatment; and S5, the saturation S of the lithium salt in the lithium salt aqueous solution in the step S3 is obtained, and according to the saturation S and the lithium elution rate n, the lithium salt aqueous solution is determined to be subjected to purification treatment, or the lithium salt aqueous solution is determined to serve as water in the step S2 to be used for water immersion treatment. According to the method, a lithium salt product with relatively high purity can be obtained.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium battery material recycling, and specifically relates to a method for recycling ternary black powder to prepare lithium salt. Background Art

[0002] As a key link in energy transformation, the new energy vehicle industry has experienced rapid development in recent years. In order to resolve the contradiction between insufficient resource endowment and the rapid development of the new energy industry, the green and efficient recycling of lithium, cobalt, nickel, manganese and other resources in retired batteries of new energy vehicles has become a matter of great concern in the new energy industry in my country and even the world.

[0003] At present, the industrial large-scale recycling of lithium, cobalt, nickel, manganese and other elements in ternary power batteries usually adopts the wet method. The wet process is to discharge, crush, heat treat and sort the retired batteries into battery black powder, then add a reducing agent and high-concentration sulfuric acid to the battery black powder to dissolve it into a leachate, and add a reducing agent and alkali to the leachate to adjust the pH to remove impurities such as copper, iron and aluminum in the leachate to obtain a decontamination liquid. Then, different organic solvents are used to extract the nickel, cobalt and manganese elements in the decontamination liquid to achieve the recovery of nickel, cobalt and manganese elements. Finally, at the end of the process, sodium carbonate is added to recover the lithium element in the form of lithium carbonate precipitation. In the wet recovery process, the recovery of lithium elements is at the end of the entire process. In the process of removing iron, aluminum and copper and extracting nickel, cobalt and manganese, lithium elements are mechanically included, resulting in a large loss. Usually, the lithium yield is only about 80%. On the other hand, mechanical inclusions reduce the purity of the obtained nickel, cobalt and manganese, affecting product quality.

[0004] In order to increase the lithium yield and purity of nickel, cobalt and manganese products, some companies use a combination of pyrometallurgy and hydrometallurgy to pre-extract the lithium element of ternary materials. The pyrometallurgy and hydrometallurgy combined process is to reduce and roast the black powder of the ternary battery to obtain roasted powder, and then add acid to the roasted powder to pre-wash out the lithium element in the roasted powder to obtain lithium-containing washing liquid and lithium-depleted roasted powder. The lithium-depleted roasted powder is then acid-dissolved, impurity-removed, organic solvent-extracted and other processes to recover nickel, cobalt and manganese elements. The lithium recovery rate is increased to about 90% through pre-extraction of lithium.

[0005] However, in the process of adding acid to elute lithium in the wet + pyrometallurgical process, nickel, cobalt and manganese will partially dissolve, and the solubility of manganese accounts for nearly half of the total manganese, resulting in a large amount of nickel, cobalt and manganese in the lithium-containing washing solution. It is necessary to remove the nickel, cobalt and manganese elements in the lithium-containing washing solution through a cumbersome process, and the final lithium compound obtained is of low purity. For this reason, the industry is in urgent need of finding a new process method to solve the problem of nickel, cobalt and manganese dissolution in the pre-extraction lithium acid elution process. Summary of the invention

[0006] In view of this, the present application provides a method for recovering ternary black powder to prepare lithium salt, which aims to solve the problem of nickel, cobalt and manganese dissolution in the process of pre-extraction lithium acid elution in the prior art solution.

[0007] In a first aspect, the present application provides a method for recovering ternary black powder to prepare lithium salt, comprising the following steps:

[0008] Step S1: adding a reducing agent to the ternary black powder for roasting, so that the high-valent non-lithium active metal elements in the ternary black powder are reduced to low-valent non-lithium active metal elements to obtain roasted black powder, wherein the roasted black powder also includes lithium carbonate; wherein the non-lithium active metal elements include nickel, cobalt and manganese;

[0009] Step S2: adding water to the roasted black powder for water immersion treatment, so that the lithium carbonate in the roasted black powder is dissolved in the water to saturation, and filtering to obtain a saturated lithium carbonate aqueous solution and insoluble solids;

[0010] Step S3: adding an inorganic acid to the saturated lithium carbonate aqueous solution until the pH is 6.5 to 7, so as to convert the lithium carbonate into a lithium salt corresponding to the inorganic acid, and obtain a lithium salt aqueous solution;

[0011] Step S4: obtaining the lithium elution rate n of step S2, and determining, according to the lithium elution rate n, whether the insoluble solid is to be washed or whether the insoluble solid is to be further immersed in water;

[0012] Among them, the lithium elution rate

[0013] m 1 is the lithium content in the insoluble solid, m 2 is the lithium content in the calcined black powder;

[0014] Step S5: Obtain the saturation S of lithium salt in the lithium salt aqueous solution in step S3, and determine whether the lithium salt aqueous solution is to be purified according to the saturation S and the lithium elution rate n, or determine whether the lithium salt aqueous solution is to be used as the water in step S2 for water immersion treatment; wherein the saturation S of lithium salt in the lithium salt aqueous solution = C / C 0 ; C is the concentration of lithium salt in the lithium salt aqueous solution, in g / L, C 0 It is the saturated solubility of lithium salt in water, in g / L.

[0015] According to the present application, by utilizing the fact that Ni, Co, MnO and some metal impurities (such as Fe, Cu and Al, etc.) in the roasted black powder are insoluble in water, the solubility of lithium carbonate in water is about 13.3 g / L, the solubility of lithium sulfate in water is about 348 g / L, and the solubility of lithium chloride in water is about 840 g / L; saturated lithium carbonate is first leached out by water leaching, and then an inorganic acid (such as sulfuric acid) is added, and the lithium carbonate becomes a lithium salt corresponding to the inorganic acid (such as lithium sulfate). Since the saturation of lithium carbonate and the lithium salt corresponding to the inorganic acid in water is quite different, the lithium salt aqueous solution corresponding to the inorganic acid can continue to be used for water leaching, that is, using a process of repeated water leaching, filtration, acid adjustment and neutralization, the content of impurity elements in the obtained lithium salt aqueous solution is small, and a high-purity lithium salt can be obtained; at the same time, repeated water leaching can fully elute the lithium element in the roasted black powder and improve the recovery rate of the lithium element.

[0016] Specifically, the method obtains roasted black powder by subjecting ternary black powder to reduction roasting treatment, wherein the roasted black powder mainly includes Ni, Co, MnO, lithium carbonate and some metal impurities (such as Fe, Cu and Al, etc.), and the lithium carbonate in the roasted black powder is dissolved in water by water immersion to obtain a saturated lithium carbonate aqueous solution and an insoluble solid. It can be understood that the solubility of the insoluble solid in water is extremely low, so that the impurity content in the saturated lithium carbonate aqueous solution is low. Therefore, in the present application, the saturated lithium carbonate aqueous solution is further neutralized with an inorganic acid, and the pH is adjusted to 6.5-7 so that the lithium carbonate can be fully converted into a lithium salt corresponding to the inorganic acid (for example, when the inorganic acid is hydrochloric acid or sulfuric acid, the corresponding lithium salt is lithium chloride and lithium sulfate), and the insoluble solid is further treated with water immersion using the lithium salt aqueous solution. Of course, the impurity content in the obtained lithium salt aqueous solution is also low.

[0017] Then, according to the content of lithium in the insoluble solid m 1 and the lithium content in the roasted black powder m 2 The lithium elution rate n of the last water leaching treatment is calculated, and the insoluble solid is repeatedly subjected to water leaching treatment according to the lithium elution rate n, or the insoluble solid is washed and used to extract other non-lithium metal elements; repeated water leaching treatment can improve the recovery rate of lithium elements; in addition, according to the concentration C of lithium salt in the lithium salt aqueous solution obtained by acid adjustment and neutralization and the saturated solubility C of lithium salt in water, the recovery rate of lithium element can be increased; 0 The saturation S of the lithium salt in the lithium salt aqueous solution is calculated, and the lithium salt aqueous solution is purified according to n and S, or the lithium salt aqueous solution is used as water in step S2 for water immersion treatment. Using the lithium salt aqueous solution for water immersion treatment can reduce water consumption, thereby reducing the cost of subsequent evaporation and crystallization to prepare lithium salt products, improving evaporation efficiency, and saving energy and protecting the environment.

[0018] It can be understood that the present method can fully separate lithium carbonate from other water-insoluble components (Ni, Co, MnO, Fe, Cu and Al, etc.) in the roasted black powder by repeated water immersion treatment, so that the lithium salt aqueous solution obtained by acid adjustment and neutralization has fewer impurities, and a lithium salt product with higher purity can be obtained; in addition, by acid adjustment and neutralization and repeated water immersion, the recovery rate of lithium elements can be improved while saving water and subsequent evaporation and crystallization costs.

[0019] It should be noted that the saturated solubility C of lithium salt in water is 0 has a well-known meaning in the art, and its value is related to temperature. When calculating the saturation S of lithium salt in lithium salt aqueous solution, C 0 That is, the saturated solubility of lithium salt in water at the detection temperature.

[0020] In some embodiments, step S4 includes: if the lithium elution rate n of step S2 satisfies n>n 0 , washing the insoluble solid to obtain a lithium-free solid product; if the lithium elution rate n of step S2 satisfies n≤n 0 The insoluble solid is used as the roasted black powder in step S2, and step S2 is repeated to continue the water immersion treatment until the lithium elution rate n>n 0 ; where n 0 is the target lithium elution rate, n 0 The value range is: 97% ≤ n 0 ≤99%.

[0021] In some of the above embodiments, it is specifically defined how to treat the insoluble solids according to the lithium elution rate after water leaching treatment, and the target lithium elution rate n 0 The recovery rate of lithium can be further improved by setting the lithium elution rate n to 97% to 99%. Specifically, if the lithium elution rate n after the last water leaching treatment is less than or equal to n 0 , indicating that the undissolved solids still contain a lot of lithium carbonate, and the undissolved solids can be repeatedly immersed in water until n is greater than n 0 , in order to improve the recovery rate of lithium; when n is greater than n 0 In the case of , it indicates that the lithium content in the insoluble solid is low, and the de-lithiation solid product can be used to recover other non-lithium metal elements. As an example, the de-lithiation solid product can be subjected to acid dissolution, impurity removal, and organic solvent extraction to recover the Ni, Co, and Mn elements therein.

[0022] In some embodiments, step S5 includes: if the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S>S 0 , the lithium salt aqueous solution is treated as a lithium-containing solution for purification to obtain a lithium salt product; if the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S≤S 0, and the lithium elution rate n≤n 0 , determine that the lithium salt aqueous solution is to be processed A, wherein the processing A comprises: using the lithium salt aqueous solution as the water in step S2 and repeating steps S2 and S3 until the saturation S is greater than S 0 If the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S≤S 0 , and the lithium elution rate n>n 0 , determining that the lithium salt aqueous solution is to be subjected to treatment B, wherein treatment B comprises: purifying the lithium salt aqueous solution as a lithium-containing solution to obtain a lithium salt product, or using the lithium salt aqueous solution to perform water immersion treatment on roasted black powder that has not been subjected to water immersion treatment; wherein S 0 is the target saturation, S 0 The value range is: 1% ≤ S 0 ≤99%.

[0023] In some of the above embodiments, it is specifically defined how to process the lithium salt aqueous solution according to the saturation S of the lithium salt in the lithium salt aqueous solution and the lithium elution rate n, and the target saturation S is set to 0 Set to 1% to 99%, when S is greater than S 0 In the case of S≤S, it means that the saturation of the lithium salt aqueous solution has reached the requirement, and the next step of purification can be carried out to prepare lithium salt products; 0 And n≤n 0 In the case of S≤S, it means that the saturation of the lithium salt aqueous solution has not reached the requirement, and the content of lithium carbonate in the insoluble solid is relatively high, that is, the lithium salt aqueous solution can be used as water in the water leaching treatment to repeat steps S2 and S3 to leach the lithium carbonate in the insoluble solid until the saturation reaches the requirement; when S≤S 0 And n>n 0 In the case of , it means that the lithium content in the undissolved solid is low and no further water immersion treatment is required. At this time, although the saturation of the lithium salt aqueous solution has not reached the requirement, there is not enough lithium carbonate in the undissolved solid to further increase its saturation. Therefore, the lithium salt aqueous solution at this time can also be purified for the preparation of lithium salt products, or the lithium salt aqueous solution can be used for water immersion treatment of the roasted black powder that has not been water-immersed, that is, the next round of roasted black powder is water-immersed.

[0024] In some embodiments, the S 0 The value range is: 40% ≤ S 0 ≤75%.

[0025] In the above embodiment, S is further defined. 0The range is 40% to 75%. If the target saturation is set to be less than 40%, the water content in the obtained lithium salt aqueous solution is high (i.e., the corresponding lithium content is low), that is, the cost of subsequent preparation of lithium salt products will increase, and the economic efficiency is poor; if the target saturation is set to be greater than 75%, the lithium ion content in the obtained lithium salt aqueous solution is high. Due to the common ion effect, the solubility of the lithium salt aqueous solution in lithium carbonate is reduced, thereby reducing the lithium elution rate of a single water immersion treatment and affecting the recovery efficiency; therefore, S 0 Setting it between 40% and 75% can more effectively balance the economy and efficiency of the recovery process.

[0026] In some embodiments, in step S1, the calcination conditions include: calcination at 500-800° C. for 2-4 hours; and the mass of the reducing agent is 20%-30% of the mass of the ternary black powder.

[0027] In some of the above embodiments, under this condition, the ternary black powder can be fully reduced so that the main components of the roasted black powder are Ni, Co, MnO, lithium carbonate and some metal impurities, which is more conducive to separating and recovering lithium and other non-lithium metal elements, improving the recovery rate of lithium elements and improving the purity of the product.

[0028] In some embodiments, the reducing agent includes at least one of carbon, natural gas, carbon monoxide, and hydrogen.

[0029] In some embodiments, in step S2, the conditions of the water immersion treatment include: water immersion at 0-40° C. for 0.5-1.5 hours. Under this condition, the solubility of lithium carbonate is relatively high, and water immersion treatment at a lower temperature is conducive to improving the water immersion efficiency.

[0030] In some embodiments, in step S2, the mass of the water is 1 to 8 times the mass of the roasted black powder. In the initial water immersion treatment, too low a water dosage will affect the efficiency of the water immersion treatment, and too high a water dosage will increase the cost of subsequent recovery of lithium salts from the lithium salt aqueous solution. Setting the mass of water to 1 to 8 times the mass of the roasted black powder can better balance the recovery cost and recovery efficiency.

[0031] In some embodiments, in step S2, the insoluble solid includes Ni, Co, and MnO. Ni, Co, and MnO are almost insoluble in water, so by using water immersion treatment, the content of nickel, cobalt, and manganese in the saturated lithium carbonate aqueous solution can be reduced, thereby improving the purity of the lithium salt product.

[0032] In some embodiments, in step S3, the inorganic acid is sulfuric acid or hydrochloric acid. In this case, the lithium salts corresponding to the inorganic acid are lithium sulfate and lithium chloride, both of which have high solubility in water, which can reduce water consumption and thus reduce production costs. At the same time, a lithium sulfate product or a lithium chloride product can be obtained as needed.

[0033] In some embodiments, in step S4, washing the insoluble solids includes returning the washing water to the water immersion treatment for recycling.

[0034] In some of the above embodiments, although the lithium content in the undissolved solid is low at this time, some residual lithium carbonate may still be dissolved in the washing water after washing with water. Therefore, the washing water is returned to the water immersion treatment for recycling, which can reduce the overall water consumption on the one hand, and on the other hand, it is also beneficial to improve the recovery rate of lithium elements.

[0035] In some of the above embodiments, the purification process includes: using an ion exchange resin to remove impurities from the lithium salt aqueous solution to remove impurity ions, and then performing an evaporation crystallization process to obtain a lithium salt product. The ion exchange resin can remove a small amount of high-valent metal ions soluble in water, such as magnesium ions, calcium ions, etc., in the lithium salt aqueous solution, and can further improve the purity of the lithium salt product. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A process flow chart of a method for recovering ternary black powder to prepare lithium salt provided in a specific embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0038] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the implementation or examples are included in at least one implementation or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more implementations or examples in a suitable manner.

[0039] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0040] The present application provides a method for recovering ternary black powder to prepare lithium salt, which comprises the following steps:

[0041] S1, adding a reducing agent to the ternary battery black powder and roasting it to obtain roasted black powder.

[0042] S2, adding pure water to the roasted black powder obtained in S1 to perform water immersion to dissolve the lithium carbonate in the roasted black powder. After the water immersion is completed, filtering is performed. Saturated lithium carbonate solution and insoluble Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solids (recorded as insoluble solids).

[0043] S3, adding inorganic acid to the saturated lithium carbonate solution obtained in S3 until the pH of the solution is 6.5-7, and the addition of inorganic acid is completed to obtain a lithium salt aqueous solution.

[0044] S4, detection of Ni / Co / MnO / Li obtained from S2 2 CO 3 / Is the lithium elution rate n in Fe / Al / Cu solid greater than n 0 , n 0 The value range is 97% ≤ n 0 ≤99%, e.g. n 0 If the lithium elution rate is greater than 98%, the obtained insoluble solid is countercurrently washed with pure water to obtain a Ni / Co / MnO / Fe / Al / Cu solid product (de-lithiumized solid product) and washing water. The washing water is returned to the water leaching process for repeated use. The Ni / Co / MnO / Fe / Al / Cu solid product can be subsequently acid-dissolved, impurity-removed, and extracted with an organic solvent to recover the Ni / Co / Mn therein.

[0045] Among them, the lithium elution rate

[0046] m 1 is the lithium content in the insoluble solid, m 2 is the lithium content in the calcined black powder.

[0047] S5, detecting whether the saturation S of the lithium salt in the obtained lithium salt aqueous solution is greater than S 0, S 0 The value range is 1%≤S 0 ≤99%, preferably 40%≤S 0 ≤75%, e.g. S 0 If the saturation is greater than 40%, the obtained lithium salt aqueous solution is subjected to exchange resin to remove high-price metal impurities and then evaporated and crystallized to obtain a high-purity lithium salt product. If the saturation is less than 40%, the unsaturated lithium salt is returned to the water leaching process to continue to circulate and dissolve lithium carbonate. Taking lithium sulfate as an example, S 0 The reason for ≥40% is that the washed lithium sulfate needs to be evaporated and crystallized to generate lithium sulfate solid after impurities are removed. If the lithium sulfate saturation is too low, the evaporation and crystallization efficiency will be too low, which wastes energy and is not economical. In addition, in the subsequent lithium sulfate precipitation process of lithium carbonate, the concentration of lithium sulfate reacting with sodium carbonate is usually greater than or equal to 40%, so it is preferred that the saturation of the lithium salt aqueous solution is greater than or equal to 40%. 0 ≤75% The reason is that the lithium in the high concentration lithium sulfate solution will produce a common ion effect to reduce the single lithium elution rate, so S 0 ≤75%.

[0048] Among them, the saturation of lithium salt in lithium salt aqueous solution S = C / C 0 ; C is the concentration of lithium salt in the lithium salt aqueous solution, in g / L, C 0 It is the saturated solubility of lithium salt in water, in g / L.

[0049] As an example, take n 0 98%, S 0 The process flow chart of the method provided by this application is as follows: Figure 1 shown.

[0050] Further, the reducing agent used in the above step S1 is C, NG, CO, H 2 , water gas or a mixture thereof. Further, the main components of the calcined black powder are Ni, Co, MnO, Li 2 CO 3 , Fe, Al, Cu. The calcination temperature is 500-800°C. The calcination time is 2-4h.

[0051] Furthermore, in the above step S2, the mass of pure water added is 1-8 times the mass of the roasted black powder, the water immersion time is 0.5-1.5h, and the water immersion temperature is 0-40°C. The reason for the low water immersion temperature is that the solubility of lithium carbonate is higher at low temperatures, and low-temperature water immersion is conducive to improving the solubility of lithium carbonate. Stirring is applied during water immersion, and the stirring speed is 200-2000r / min.

[0052] Furthermore, in the above step S5, the inorganic acid is hydrochloric acid or sulfuric acid, and the mass fraction of the inorganic acid is 5-98%. When the inorganic acid is hydrochloric acid, the obtained lithium salt product is lithium chloride, and when the inorganic acid is sulfuric acid, the obtained lithium salt product is lithium sulfate.

[0053] In the further above step S5, the exchange resin is CH-93 resin, 732 cation exchange resin, etc., further in the above step S5, the evaporation crystallization temperature is 280-350°C to remove the crystal water in the lithium salt product.

[0054] As an example, take n 0 98%, S 0 The subsequent treatment of the undissolved solid in step S2 and the lithium salt aqueous solution in step S3 is shown in Table 1.

[0055] Table 1

[0056]

[0057]

[0058] The scheme of the present application is described below in conjunction with the following specific examples. Unless otherwise specified, the raw materials used in the following examples are all from common commercial products, and the devices or equipment used are all purchased from conventional market sales channels.

[0059] Source of ternary black powder: Black powder is obtained by dismantling, crushing, roasting and screening of waste electrolysis, and the roasting temperature is 300-400℃.

[0060] Example 1 (n 0 The value is 98%, S 0 The value is 40%)

[0061] Take 200g of NCM ternary black powder, and the lithium content is 6.21% or 12.42g by inductively coupled plasma spectroscopy (ICP) test. 40g of water gas is trickled into the ternary black powder as a reducing agent, and roasted at 700℃ for 2h to obtain roasted black powder.

[0062] Add 378g of pure water to the roasted black powder, and soak the lithium carbonate in the roasted black powder. The soaking time is 0.5h, the soaking temperature is 25℃, and the stirring speed during the soaking process is 500r / min. After the soaking, filter to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0063] The lithium content in the undissolved solid was tested to be 11.64 g, and the lithium elution rate n was 6.28% (calculation method: n=1-11.64 / 12.42=6.28%), which was less than 98%, and required the subsequent lithium salt solution to continue the water immersion treatment.

[0064] 18.27 g of 30 wt% sulfuric acid was added to the saturated lithium carbonate solution to adjust the acidity to 6.8, and a lithium sulfate solution was obtained after the acid adjustment and neutralization. The concentration of lithium sulfate in the lithium sulfate solution was tested to be 15.47 g / L, and the saturated solubility of lithium sulfate was C 0 The lithium sulfate saturation S is about 348g / L after one washing, and the lithium sulfate saturation S is 4.445% (the calculation formula is S = 15.47 / 348 = 4.445%), S < 40%, so the lithium sulfate solution is returned to continue leaching Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0065] After 21 times of water immersion, filtration, acid adjustment and neutralization, and circulation (the removal efficiency of insoluble solids was less than 98% during the circulation, and the content of lithium sulfate in the lithium sulfate solution was less than 0.4 times its saturation value), the Ni / Co / MnO / Li 2 CO 3 The lithium content of the / Fe / Al / Cu solid was measured by ICP to be 0.144 g, and the lithium elution rate n was 98.84% (calculation method: n=1-0.144 / 12.42=98.84%), which is greater than 98%. The insoluble solid was countercurrently washed 4 times with pure water, and the obtained washing liquid could be added to the water immersion process for further use.

[0066] The lithium sulfate solution obtained by acid adjustment and neutralization was sampled and the concentration of lithium sulfate in the lithium sulfate solution was tested to be 144.77 g / L. The lithium sulfate saturation S was 41.6% (the calculation formula was S=144.77 / 348=41.6%) after washing. S>40%. The content of high-valent metal impurities (Mn, Ni, Co) was 89 ppm as measured by ICP. The total mass fraction consumed during the circulation process was 289 g of 30 wt% sulfuric acid. The lithium sulfate solution was then subjected to exchange resin treatment, specifically: the obtained lithium sulfate solution was subjected to After CH-93 resin was decontaminated, it was evaporated and crystallized at 300° C. for 2 h to obtain 97.05 g of lithium sulfate with a purity of 99.6%. The calculated lithium yield was 98.2% (calculated as: 97.05×99.6%×13.88 / 109.95 / 12.42=98.2%).

[0067] Example 2 (n0 value is 98%, S 0 The value is 40%)

[0068] Take 200g of the same NCM ternary black powder as in Example 1, and test the lithium content of the powder by inductively coupled plasma spectroscopy (ICP) to be 6.21%, i.e., 12.42g of lithium. 40g of water gas is trickled into the ternary black powder as a reducing agent, and the powder is roasted at 700°C for 2h to obtain roasted black powder.

[0069] Add 606g of pure water to the roasted black powder, and soak the lithium carbonate in the roasted black powder. The soaking time is 0.5h, the soaking temperature is 25℃, and the stirring speed during the soaking process is 500r / min. After the soaking, filter to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0070] The lithium content in the undissolved solid was tested to be 11.18 g, and the lithium elution rate n was 10% (calculation method: n=1-11.18 / 12.42=10%), which was less than 98%, and required the subsequent lithium salt solution to be used for further water immersion treatment.

[0071] 29.23 g of 30 wt% sulfuric acid was added to the saturated lithium carbonate solution to adjust the acidity to 6.9. After the acid adjustment and neutralization, a lithium sulfate solution was obtained. The concentration of lithium sulfate in the lithium sulfate solution was tested to be 15.65 g / L. The saturated solubility of lithium sulfate was C 0 The lithium sulfate saturation S is about 348g / L after one washing, and the lithium sulfate saturation S is 4.498% (the calculation formula is S = 15.65 / 348 = 4.497%), S < 40%, so the lithium sulfate solution is returned to continue leaching Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0072] After 13 cycles of water immersion, filtration, acid adjustment and neutralization (the removal efficiency of insoluble solids was less than 98% during the cycle, and the content of lithium sulfate in the lithium sulfate solution was less than 0.4 times its saturation value), the Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid has a lithium content of 0.128 g as measured by ICP, and a lithium elution rate n of 98.97% (calculation method: n=1-0.128 / 12.42=98.97%), which is greater than 98%. The insoluble solid is countercurrently washed 4 times with pure water, and the obtained washing liquid can be added to the water immersion process for further use.

[0073] The lithium sulfate solution obtained by acid neutralization was sampled and tested, and the concentration of lithium sulfate in the lithium sulfate solution was C, which was 108.95 g / L. The lithium sulfate saturation S after washing was 31.31% (the calculation formula was S = 108.95 / 348 = 31.31%), S < 40%, and the content of high-valent metal impurities (Mn, Ni, Co) was 93 ppm as measured by ICP. The total mass fraction consumed during the circulation process was 289 g of 30 wt% sulfuric acid. The lithium sulfate solution was then subjected to exchange resin treatment, specifically: the obtained lithium sulfate solution was subjected to After CH-93 resin was decontaminated, it was evaporated and crystallized at 300° C. for 2.5 h to obtain 97.11 g of lithium sulfate with a purity of 99.63%. The calculated lithium yield was 98.3% (calculated as: 97.11×99.63%×13.88 / 109.95 / 12.42=98.3%).

[0074] Compared with Example 1, the lithium elution rate and lithium yield of Example 2 are similar. However, the amount of water required to evaporate to obtain 1g of lithium sulfate in Example 1 is 6.91mL (the calculation method is 1000 / 144.77=6.91), and the amount of water required to evaporate to obtain 1g of lithium sulfate in Example 2 is 9.18mL (the calculation method is 1000 / 108.95=9.18). The amount of water evaporated to obtain 1g of lithium sulfate in Example 2 is increased by 32.9% compared with Example 1. Therefore, it is necessary to appropriately increase the concentration of the lithium sulfate solution obtained by washing (by continuing to return to the water immersion treatment, or reducing the amount of water used in the first water immersion treatment, and increasing the number of washing times) to increase the evaporation efficiency.

[0075] Example 3 (n 0 The value is 98%, S 0 The value is 40%)

[0076] Take 200g of NCM ternary black powder, and the lithium content is 3.5% or 7g by inductively coupled plasma spectroscopy (ICP) test. 40g of water gas is trickled into the ternary black powder as a reducing agent, and roasted at 700℃ for 2h to obtain roasted black powder.

[0077] Add 383g of pure water to the roasted black powder, and soak the lithium carbonate in the roasted black powder. The soaking time is 0.5h, the soaking temperature is 25℃, and the stirring speed during the soaking process is 500r / min. After the soaking, filter to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0078] The lithium content in the undissolved solid was tested to be 6.24 g, and the lithium elution rate n was 10.86% (calculation method: n=1-6.24 / 7=10.86%), which was less than 98%, and required the subsequent lithium salt solution to continue the water immersion treatment.

[0079] 17.94 g of 30 wt% sulfuric acid was added to the saturated lithium carbonate solution to adjust the acidity to 6.8, and a lithium sulfate solution was obtained after the acid adjustment and neutralization. The concentration of lithium sulfate in the lithium sulfate solution was tested to be 15.35 g / L, and the saturated solubility of lithium sulfate was C 0 About 348g / L, after one wash, the lithium sulfate saturation S is 4.41% (the calculation formula is S = 15.35 / 348 = 4.41%), S 1 <40%, so the lithium sulfate solution is returned to continue leaching Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0080] After 12 cycles of water immersion, filtration, acid adjustment and neutralization (the removal efficiency of insoluble solids was less than 98% during the cycle, and the content of lithium sulfate in the lithium sulfate solution was less than 0.4 times its saturation value), the Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid has a lithium content of 0.105 g as measured by ICP, and a lithium elution rate n of 98.5% (calculation method: n=1-0.105 / 7=98.5%), which is greater than 98%. The insoluble solid is countercurrently washed 4 times with pure water, and the obtained washing liquid can be added to the water immersion process for further use.

[0081] The lithium sulfate solution obtained by acid neutralization was sampled and tested, and the concentration C of lithium sulfate in the lithium sulfate solution was 101.22 g / L. The lithium sulfate saturation S after washing was 29.09% (the calculation formula was S=101.22 / 348=29.09%), S<40%, and the content of high-valent metal impurities (Mn, Ni, Co) was 87 ppm as measured by ICP. The total mass fraction consumed during the circulation process was 162.2 g of 30 wt% sulfuric acid. The lithium sulfate solution was then subjected to exchange resin treatment, specifically: the obtained lithium sulfate solution was subjected to After CH-93 resin was decontaminated, it was evaporated and crystallized at 300° C. for 2 h to obtain 54.49 g of lithium sulfate with a purity of 99.63%. The calculated lithium yield was 97.9% (calculated as: 54.49×99.63%×13.88 / 109.95 / 7=97.9%).

[0082] Compared with Example 1, the use of ternary black powder with low lithium content does not affect the lithium elution rate and lithium yield, indicating that this method is also suitable for processing ternary black powder with low lithium content.

[0083] Example 4

[0084] Take 200g of the same NCM ternary black powder as in Example 2, and test the lithium content of the powder by inductively coupled plasma spectroscopy (ICP) to be 6.21%, i.e., 12.42g of lithium. 40g of water gas is trickled into the ternary black powder as a reducing agent, and the powder is roasted at 700°C for 2h to obtain roasted black powder.

[0085] Add 606g of lithium sulfate solution with a concentration of 261g / L, i.e., a saturation of 75%, to the roasted black powder, and soak the lithium carbonate in the roasted black powder in water. The soaking time is 0.5h, the soaking temperature is 25°C, and the stirring speed during the soaking process is 500r / min. After the soaking, filter to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0086] The lithium content in the undissolved solid was tested to be 11.92 g, and the lithium elution rate n was 4.0% (calculation method: n=1-11.92 / 12.42=4%), which was less than 98%, and required the subsequent lithium salt solution to be used for further water immersion treatment.

[0087] It is explained that the lithium removal efficiency of a single immersion treatment using a lithium sulfate aqueous solution with a saturation of 75% is 4%.

[0088] Example 5

[0089] Take 200g of the same NCM ternary black powder as in Example 2, and test the lithium content of the powder by inductively coupled plasma spectroscopy (ICP) to be 6.21%, i.e., 12.42g of lithium. 40g of water gas is trickled into the ternary black powder as a reducing agent, and the powder is roasted at 700°C for 2h to obtain roasted black powder.

[0090] Add 606g of lithium sulfate solution with a concentration of 295g / L, i.e., a saturation of 85%, to the roasted black powder, and soak the lithium carbonate in the roasted black powder in water. The soaking time is 0.5h, the soaking temperature is 25°C, and the stirring speed during the soaking process is 500r / min. After the soaking, filter to obtain a saturated lithium carbonate solution and undissolved Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0091] The lithium content in the undissolved solid was tested to be 12.04 g, and the lithium elution rate n was 3.06% (calculation method: n=1-12.04 / 12.42=3.06%), which was less than 98%, and required the subsequent lithium salt solution to continue the water leaching treatment.

[0092] It is explained that the lithium removal efficiency of a single immersion treatment using a lithium sulfate aqueous solution with a saturation of 85% is 3.06%.

[0093] Example 2 Compared with Example 4 and Example 5, the lithium sulfate saturation in the initial washing solution of the same mass of washing solution increased from 0 to 75% and 85%, and the lithium elution rate decreased from 10% to 4% and 3.06%, respectively. The decrease in elution rate will increase the number of elutions, so an appropriate target saturation S can be selected. 0 To improve the lithium elution efficiency.

[0094] Comparative Example 1

[0095] Take 200g of the same NCM ternary black powder as in Example 1, and test the lithium content of the powder by inductively coupled plasma spectroscopy (ICP) to be 6.21%, i.e., 12.42g of lithium. 40g of water gas is trickled into the ternary black powder as a reducing agent, and the powder is roasted at 700°C for 2h to obtain roasted black powder.

[0096] 378g of pure water and 289g of 30% sulfuric acid (the same total acid amount as in Example 1) were added to the roasted black powder to extract and dissolve the lithium carbonate in the roasted black powder. The immersion time was 0.5h, the immersion temperature was 25°C, and the stirring speed during the immersion process was 500r / min. After the immersion was completed, the solution containing lithium sulfate and lithium carbonate and the insoluble Ni / Co / MnO / Li 2 CO 3 / Fe / Al / Cu solid.

[0097] The lithium content in the undissolved solid was tested to be 7.32 g, and the lithium washing efficiency was 41.1% (calculation method: 1-7.32 / 12.42=41.1%).

[0098] The above washing was evaporated and crystallized at 300° C. for 3 h to obtain 105.91 g of lithium sulfate with a purity of 25.64%, of which manganese sulfate accounted for 48.3%.

[0099] Compared with the embodiments, direct addition of high-concentration sulfuric acid for washing causes a large amount of reaction between the alkaline oxide manganese oxide in the roasted powder and the sulfuric acid, that is, a portion of the sulfuric acid reacts with the manganese oxide and a portion of the sulfuric acid reacts with the lithium carbonate, which greatly reduces the lithium elution rate, increases the dissolution of manganese, and reduces the purity of the obtained lithium salt.

[0100] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for recovering ternary black powder to prepare lithium salt, characterized in that: The following steps are involved: Step S1: adding a reducing agent to the ternary black powder for roasting, so that the high-valent non-lithium active metal elements in the ternary black powder are reduced to low-valent non-lithium active metal elements to obtain roasted black powder, wherein the roasted black powder also includes lithium carbonate; Wherein, the non-lithium active metal elements include nickel, cobalt and manganese; Step S2: adding water to the roasted black powder for water immersion treatment, so that the lithium carbonate in the roasted black powder is dissolved in the water to saturation, and filtering to obtain a saturated lithium carbonate aqueous solution and insoluble solids; Step S3: adding an inorganic acid to the saturated lithium carbonate aqueous solution until the pH is 6.5 to 7, so as to convert the lithium carbonate into a lithium salt corresponding to the inorganic acid, and obtain a lithium salt aqueous solution; Step S4: obtaining the lithium elution rate n of step S2, and determining, according to the lithium elution rate n, whether the insoluble solid is to be washed or whether the insoluble solid is to be further immersed in water; Among them, the lithium elution rate m1 is the lithium content in the insoluble solid, and m2 is the lithium content in the calcined black powder; Step S5: obtaining the saturation S of lithium salt in the lithium salt aqueous solution in step S3, and determining, according to the saturation S and the lithium elution rate n, that the lithium salt aqueous solution is to be purified, or determining that the lithium salt aqueous solution is to be used as the water in step S2 for water leaching; Wherein, the saturation of lithium salt in lithium salt aqueous solution S=C / C0; C is the concentration of lithium salt in the lithium salt aqueous solution, in g / L, and C0 is the saturated solubility of lithium salt in water, in g / L.

2. The method according to claim 1, characterized in that Step S4 includes: If the lithium elution rate n of step S2 satisfies n>n0, the insoluble solid is washed to obtain a de-lithium solid product; If the lithium elution rate n of step S2 satisfies n≤n0, the insoluble solid is used as the roasted black powder in step S2 and step S2 is repeated to continue the water immersion treatment until the lithium elution rate n>n0; Wherein, n0 is the target lithium elution rate, and the value range of n0 is: 97%≤n0≤99%.

3. The method according to claim 2, characterized in that Step S5 includes: If the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S>S0, the lithium salt aqueous solution is treated as a lithium-containing solution for purification to obtain a lithium salt product; If the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S≤S0, and the lithium elution rate n≤n0, it is determined that the lithium salt aqueous solution is to be treated A, The process A comprises: using the lithium salt aqueous solution as water in step S2, repeating step S2 and step S3 until the saturation S is greater than S0; If the saturation S of the lithium salt in the lithium salt aqueous solution satisfies S≤S0, and the lithium elution rate n>n0, it is determined that the lithium salt aqueous solution is to be treated B, The process B comprises: purifying the lithium salt aqueous solution as a lithium-containing solution to obtain a lithium salt product, or using the lithium salt aqueous solution to perform water immersion treatment on roasted black powder that has not been water-immersed; Wherein, S0 is the target saturation, and the value range of S0 is: 1%≤S0≤99%.

4. The method according to claim 3, characterized in that The value range of S0 is: 40%≤S0≤75%.

5. The method according to claim 1, characterized in that In the step S1, the calcination conditions include: calcination at 500-800°C for 2-4h; the mass of the reducing agent is 20%-30% of the mass of the ternary black powder.

6. The method according to claim 1, characterized in that In the step S2, the conditions of the water immersion treatment include: immersion in water at 0-40°C for 0.5-1.5h; and / or, in the step S2, the mass of the water is 1-8 times the mass of the roasted black powder.

7. The method according to claim 1, characterized in that In the step S2, the insoluble solid includes Ni element, Co element, and MnO.

8. The method according to claim 1, characterized in that In step S3, the inorganic acid is sulfuric acid or hydrochloric acid.

9. The method according to claim 1, characterized in that: In the step S4, washing the insoluble solids includes returning the washing water to the water immersion process for recycling.

10. The method according to claim 1, characterized in that The purification process includes: using an ion exchange resin to remove impurities from the lithium salt aqueous solution to remove impurity ions, and then performing evaporation and crystallization to obtain a lithium salt product.

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