Ammonia leaching recovery process using ammonium sulfite and hydrazine hydrate as reducing agent

Abstract

The invention provides an ammonia leaching recovery process taking ammonium sulfite and hydrazine hydrate as reducing agents, and belongs to the technical field of lithium ion battery recovery. The process provided by the invention comprises the following steps: mixing ammonia water, a reducing agent and a buffering agent to obtain an ammonia leaching solution; mixing the ammonia leaching solution with the waste ternary lithium ion battery positive electrode powder to carry out reduction reaction, and filtering to obtain a leaching solution and manganese-containing leaching residues; the reducing agent is ammonium sulfite and hydrazine hydrate. According to the method, efficient leaching of lithium, nickel and cobalt is selectively completed through an ammonium sulfite and buffering agent system, manganese is almost not leached and left in leaching residues, meanwhile, through cooperation with strengthened reduction leaching of hydrazine hydrate, sufficient leaching of lithium, nickel and cobalt is completed, reaction proceeding is accelerated, and the leaching efficiency is improved. The problem that the leaching efficiency is not high when a single reducing agent is used in the reduction ammonia leaching stage is solved, and subsequent separation steps are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery recovery, and in particular to an ammonia leaching recovery process using ammonium sulfite and hydrazine hydrate as reducing agents. Background Art

[0002] With the rapid development of lithium-ion battery technology in recent years, the recycling of cathode materials from used lithium-ion batteries, due to their high concentrations of valuable metals, has seen a surge in activity. Among these, batteries such as lithium nickel cobalt manganese oxide, lithium manganese oxide, and lithium cobalt oxide, due to their superior electrical performance, account for over half of the lithium-ion battery market. Therefore, the recovery and processing of valuable metals from the cathode materials of used ternary lithium-ion batteries not only has high economic value but also alleviates the national shortage of valuable metal resources such as nickel, cobalt, manganese, and lithium.

[0003] Currently, the recovery methods for valuable metals from scrapped ternary cathode materials are primarily divided into hydrometallurgical and pyrometallurgical processes. Taking the typical chemical method as an example, these are primarily categorized into pyrometallurgical and hydrometallurgical processes. Pyrometallurgical recovery offers simpler operation and a shorter process compared to the other two methods, but the roasting process is energy-intensive, and high-temperature roasting produces waste gas and waste residue, which can easily pollute the environment. The hydrometallurgical process, currently widely used in research both domestically and internationally, offers advantages such as high metal recovery rates, simple operation steps, and minimal pollution.

[0004] The principle of inorganic acid or organic acid leaching and biological leaching in wet process is based on the reaction between hydrogen ions and positive electrode active powder in acidic medium. Acid leaching is divided into inorganic acid leaching and organic acid leaching. In the process of inorganic acid leaching, strong acid is generally used, which is highly corrosive and will also produce Cl2, SO2, NO x and other harmful gases; organic acids can be naturally degraded, and their leaching has the advantage of being green and environmentally friendly, but there is a problem with low leaching rate. The biological leaching method is low in cost, but has the disadvantages of being difficult to cultivate bacteria, a long leaching cycle and a low leaching rate of valuable metals, so it is difficult to promote in industrial applications. Unlike the above leaching methods, ammonia leaching has the advantage of selectively separating valuable metals. By adjusting the composition of the leaching agent, efficient leaching of Co, Ni, and Li can be achieved, while Mn, Al, and Fe are basically not leached, making it possible to recover valuable metals from waste lithium-ion batteries in a short process.

[0005] The Chinese patent (CN201811045199.4) adds a mixture of waste ternary cathode powder, ammonium salt, and ammonia water, as well as a reducing agent, to an autoclave and performs a leaching reaction under a predetermined pressure, obtaining solutions with leaching rates of 98.3%, 92.1%, 95.8%, and 1.2% for nickel, cobalt, lithium, and manganese, respectively. The reducing agent and ammonium salt used are relatively expensive and require high operating equipment. The Chinese patent (CN202211028929.6) uses ammonia water, ferrous chloride, and ammonium chloride as the leaching system, with leaching rates of 99.7%, 90.1%, 95.6%, and 48.7% for nickel, cobalt, lithium, and manganese, respectively. Due to the presence of chloride ions in the system, soluble manganese chloride is generated, but there is a problem with the high manganese leaching rate. The Chinese patent (202310292981.0) uses ammonia water, sodium sulfite and ammonium sulfate as the leaching system. The first-stage leaching rates of lithium, nickel, cobalt and manganese are 96.9%, 98.1%, 93.6% and 37.7% respectively. The large amount of manganese leaching makes the subsequent separation of valuable metals more complicated.

[0006] When treating spent ternary cathode materials, a method involves first calcining them at high temperature using a pyrometallurgical method, followed by water leaching to extract lithium, and then using ammonia leaching to recover nickel and cobalt. While this method can achieve high nickel and cobalt leaching rates, it often consumes a lot of energy, results in incomplete lithium recovery, and is accompanied by the generation of waste gas, which pollutes the environment. Directly using reduction ammonia leaching technology to treat spent ternary cathode materials suffers from low nickel and cobalt leaching rates and poor selectivity. Therefore, it is urgent to find a reducing agent combination that is more selective for the target metal during the reduction reaction, while also combining the pH buffering advantages of a buffer to ensure efficient leaching of lithium, nickel, and cobalt while avoiding the leaching of manganese and other elements. Summary of the Invention

[0007] In view of this, the object of the present invention is to provide an ammonia leaching recovery process using ammonium sulfite and hydrated hydrazine as a reducing agent. The ammonia leaching recovery process provided by the present invention completes the sufficient leaching of lithium, nickel and cobalt, accelerates the reaction, and solves the problem of low leaching efficiency using a single reducing agent in the reduction ammonia leaching stage.

[0008] In order to achieve the above object, the present invention provides the following technical solution: an ammonia leaching recovery process using ammonium sulfite and hydrazine hydrate as a reducing agent, comprising the following steps:

[0009] mixing ammonia water, a reducing agent and a buffer to obtain an ammonia leaching solution;

[0010] The ammonia leachate is mixed with the cathode powder of the waste ternary lithium ion battery to carry out a reduction reaction, and filtered to obtain a leachate and a manganese-containing leach residue;

[0011] The reducing agents are ammonium sulfite and hydrazine hydrate.

[0012] Preferably, the molar ratio of ammonium sulfite to hydrazine hydrate is (0.12-0.84): (0.016-0.08).

[0013] Preferably, the molar ratio of the ammonia water, the reducing agent and the buffer is (0.35-3.5): (0.12-0.84): (0.47-1.88).

[0014] Preferably, the buffer is at least one of ammonium carbonate, ammonium bicarbonate, ammonium sulfate and ammonium chloride.

[0015] Preferably, the pH value of the ammonia leaching solution is 8-10.

[0016] Preferably, the solid-liquid ratio of the ammonia leaching solution to the waste ternary lithium-ion battery positive electrode powder is 10 to 50 g / L.

[0017] Preferably, the general formula of the waste ternary lithium ion battery positive electrode powder is Li(Ni x Co y Mn 1-x-y )O2, where x ranges from 0 to 1, y ranges from 0 to 1, and x+y ranges from 0 to 1.

[0018] Preferably, the reduction reaction conditions are: temperature of 25-70° C., time of 240-480 min, and rotation speed of 200-450 r / min.

[0019] The present invention also provides a method for reducing the leaching of Mn elements in waste ternary lithium-ion battery positive electrode materials, using the ammonia leaching recovery process described in the above technical solution to treat the waste ternary lithium-ion battery positive electrode materials.

[0020] Beneficial technical effects:

[0021] 1. Compared with existing ammonia leaching processes: This invention utilizes ammonium sulfite in conjunction with hydrazine hydrate for ammonia leaching to achieve efficient and comprehensive leaching of valuable metals such as nickel, cobalt, and lithium. This addresses the low leaching rate and poor selectivity of valuable metals in the one-step ammonia leaching of waste ternary cathode materials. This method promotes the leaching of nickel and cobalt while efficiently separating manganese from the impurities of aluminum and iron. The ammonia leaching residue can be used to purify battery-grade manganese carbonate, significantly reducing purification costs.

[0022] 2. The present invention uses ammonium sulfite as the main reducing agent, which can fully react with the target ions in the solution, greatly reducing energy consumption compared to traditional roasting reduction. In addition, ammonium sulfite also has a certain buffering effect on the solution and can also provide an additional ammonia source.

[0023] 3. The use of a buffer solution in the present invention not only ensures a higher leaching rate of valuable metals, but also effectively inhibits the leaching of aluminum ions in combination with the effect of ammonium sulfite, thereby improving the purity of the leachate and reducing the influence of impurity ions on the separation of valuable metals in the leachate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is the SEM image of the leached residue prepared in Example 1;

[0026] Figure 2 Graph showing the effect of different hydrazine hydrate concentrations on the leaching rate of valuable metals in Example 1;

[0027] Figure 3 1 is the XRD pattern of the leached residue at different hydrazine hydrate concentrations in Example 1. DETAILED DESCRIPTION

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0030] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0031] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0032] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0033] The present invention provides an ammonia leaching recovery process using ammonium sulfite in conjunction with hydrazine hydrate as a reducing agent. The process selectively completes efficient leaching of lithium, nickel and cobalt through the ammonium sulfite and buffer system, while manganese is hardly leached and remains in the leaching residue. At the same time, the process cooperates with the enhanced reduction leaching of hydrazine hydrate to complete sufficient leaching of lithium, nickel and cobalt, accelerates the reaction, solves the problem of low leaching efficiency when using a single reducing agent in the reduction ammonia leaching stage, and reduces subsequent separation steps.

[0034] The ammonia leaching recovery process provided by the present invention specifically comprises the following steps:

[0035] mixing ammonia water, a reducing agent and a buffer to obtain an ammonia leaching solution;

[0036] The ammonia leachate is mixed with the cathode powder of the waste ternary lithium ion battery to carry out a reduction reaction, and the leachate and manganese-containing leach residue are obtained by filtration; the reducing agent is ammonium sulfite and hydrazine hydrate.

[0037] The present invention utilizes the strong reducing property of sulfite ions to treat waste ternary lithium-ion battery positive electrode materials in an ammonia solution, reducing the high-valent target metal to a low-valent state, and combining the buffering advantage of the buffer to pH; at the same time, the introduction of hydrazine hydrate reduces the potential value of the system, making the cobalt ammonia complex ions and nickel ammonia complex ions more stable in the solution, reducing the tendency of ion precipitation, thereby achieving the purpose of strengthening reduction leaching and fully leaching the target metal; finally, solid-liquid separation is performed to obtain leachate and leaching residue, and through the selective leaching of the target metal, the subsequent separation and purification steps are greatly reduced, the experimental process is simplified, and the steps are simple. By using ammonium sulfite in conjunction with hydrazine hydrate as a reducing agent, the problem of low leaching rate of valuable metals and poor selectivity in the one-step reduction ammonia leaching method of waste ternary positive electrode materials can be solved.

[0038] In some embodiments, the molar ratio of ammonium sulfite to hydrazine hydrate is preferably (0.12-0.84): (0.016-0.08), more preferably 0.31: (0.016-0.048). The present invention mainly uses ammonium sulfite as the main reducing agent, because ammonium sulfite can provide SO3 2-Reducing high-valent nickel and cobalt can provide an ammonia source, reduce the addition of other ammonium salts, and reduce costs. If the amount of hydrated ammonia used as the main reducing agent is too high, on the one hand, the leaching rate of impurity elements such as iron and aluminum will increase, which is not conducive to the subsequent purification of the leachate. On the other hand, the cost of hydrated ammonia reagent is relatively high.

[0039] In some embodiments, the molar ratio of ammonia water, reducing agent and buffer is preferably (0.35-3.5): (0.12-0.84): (0.47-1.88). The pH of the solution is determined by the amount of NH4 + The ratio of ammonia to NH3 is determined, so the key to improving the leaching rate of valuable metals is to reasonably control the addition amount of the three to maintain the solution within the preferred pH range of the present invention. Therefore, too high or too low ammonia and ammonium salt concentrations are not conducive to the sufficient leaching of valuable metals.

[0040] In some embodiments, the buffer is preferably at least one of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, and ammonium chloride, more preferably ammonium carbonate, ammonium bicarbonate, ammonium sulfate, or ammonium chloride, and most preferably ammonium bicarbonate. In the present invention, ammonium bicarbonate has a better buffering effect, ensuring that the pH during the reduction process is under weak alkaline conditions. At the same time, it can be combined with ammonium sulfite to effectively inhibit the leaching of aluminum ions, thereby improving the purity of the leachate.

[0041] In some embodiments, the pH value of the ammoniacal leaching solution is preferably 8-10.

[0042] In some embodiments, the solid-to-liquid ratio of the ammonia leaching solution to the waste ternary lithium-ion battery positive electrode powder is preferably 10 to 50 g / L.

[0043] In some embodiments, the general formula of the waste ternary lithium ion battery positive electrode powder is Li(Ni x Co y Mn 1-x-y )O2, where x ranges from 0 to 1, y ranges from 0 to 1, and x+y ranges from 0 to 1.

[0044] In some embodiments, the reduction reaction conditions are: temperature of 25-70°C, time of 240-480 min, and rotation speed of 200-450 r / min. When ammonium sulfite and hydrazine hydrate are used as reducing agents, the present invention can ensure that the reduction leaching is efficiently achieved at a lower temperature.

[0045] The present invention also provides a method for reducing the leaching of Mn elements in waste ternary lithium-ion battery positive electrode materials. The waste ternary lithium-ion battery positive electrode materials are treated using the ammonia leaching recovery process described in the above technical solution, and the leaching rate of Mn in the obtained leachate can reach ≤0.1%.

[0046] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0047] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0048] The composition of the waste ternary positive electrode powder material in the embodiments of the present invention and the comparative examples is: NCM523.

[0049] Example 1

[0050] This embodiment is an ammonia leaching recovery process using ammonium sulfite and hydrazine hydrate as reducing agents, and the specific steps are as follows:

[0051] (1) preparing 1 L of a mixed solution of 0.7 mol / L ammonia water, 0.31 mol / L ammonium sulfite, 0.048 mol / L hydrazine hydrate, 1.41 mol / L ammonium bicarbonate and deionized water as the ammonia leachate for the reaction;

[0052] (2) The ammonia leaching solution obtained in step (1) was continuously stirred until the ammonium salt was completely dissolved, and then 20 g of waste ternary lithium-ion battery positive electrode powder material was added, mixed, and fully reacted at 60° C. The stirring speed was 400 r / min. After the reaction time of 360 min, heating and stirring were stopped, and solid-liquid separation of the system was achieved by a vacuum filtration device.

[0053] The concentration of valuable metals in the leachate was detected by ICP analysis, and the calculated leaching rates of lithium, nickel, and cobalt were 96.5%, 98.2%, and 95.1%, respectively. The leaching rate of manganese was only 0.1%, and the leaching rates of impurities iron and aluminum were 0.2% and 0.3%, respectively. It basically did not contain other impurities. The leaching residue was enriched with valuable metal manganese and existed in the form of manganese carbonate. The micromorphology of the leaching residue was analyzed by SEM, and the results are shown in Figure 1 , you can see obvious slightly flat olive-shaped manganese carbonate particles that are tightly packed together.

[0054] The concentration of hydrazine hydrate was changed (the concentration of hydrazine hydrate was set to 0, 0.016mol / L, 0.032mol / L, 0.049mol / L, 0.066mol / L, and 0.082mol / L in sequence) to explore its effect on the leaching rate of valuable metals. Figure 2 It can be seen that with the increase of hydrazine hydrate concentration, the leaching rates of lithium, nickel and cobalt first increase and then decrease, and reach the peak value when the concentration of hydrazine hydrate reaches 0.048 mol / L.

[0055] Observe the XRD patterns of leaching residues at different hydrazine hydrate concentrations ( Figure 3 ), it can be found that the peak of the waste ternary cathode material has basically disappeared, indicating that the main phase of the leached slag has changed from the original NCM523 to MnCO3, indicating that the valuable metals in the cathode material have been fully leached.

[0056] Example 2

[0057] This embodiment is an ammonia leaching recovery process using ammonium sulfite and hydrazine hydrate as reducing agents, and the specific steps are as follows:

[0058] (1) preparing 1 L of a mixed solution of 0.7 mol / L ammonia water, 0.31 mol / L ammonium sulfite, 0.048 mol / L hydrazine hydrate, 1 mol / L ammonium carbonate and deionized water as the ammonia leachate for the reaction;

[0059] (2) The ammonia leaching solution obtained in step (1) was continuously stirred until the ammonium salt was completely dissolved, and then 20 g of waste ternary lithium-ion battery positive electrode powder material was added, mixed, and fully reacted at 60° C. The stirring speed was 400 r / min. After the reaction time of 360 min, heating and stirring were stopped, and solid-liquid separation of the system was achieved by a vacuum filtration device.

[0060] The concentration of valuable metals in the leachate was detected by ICP analysis, and the calculated leaching rates of lithium, nickel, and cobalt were 92.1%, 94.3%, and 91.7%, respectively. The leaching rate of manganese was only 0.1%, and the leaching rates of impurities such as iron and aluminum were less than 1%. The leachate basically did not contain other impurities, while the leaching residue was enriched in the valuable metal manganese, which existed in the form of manganese carbonate.

[0061] This example uses similar steps to the method of Example 1, except that ammonium carbonate is used as the system buffer instead of ammonium bicarbonate. Combining Examples 1 and 2, it was found that, in an ammonium carbonate buffer system, the reduction leaching of ammonium sulfite in conjunction with hydrazine hydrate can also effectively improve the metal leaching rate; however, the effect of ammonium carbonate as a system buffer is lower than that of ammonium bicarbonate. This may be because the buffering effect of ammonium carbonate is not as good as that of ammonium bicarbonate, resulting in a higher pH in this system, which is not conducive to sufficient leaching of valuable metals.

[0062] Comparative Example 1

[0063] The ammonia leaching recovery process of this comparative example has the following specific steps:

[0064] (1) preparing 1 L of a mixed solution of 0.7 mol / L ammonia water, 0.31 mol / L ammonium sulfite, 1.41 mol / L ammonium bicarbonate and deionized water as the ammonia leachate for the reaction;

[0065] (2) The ammonia leaching solution obtained in step (1) was continuously stirred until the ammonium salt was completely dissolved, and then 20 g of waste ternary lithium-ion battery positive electrode powder material was added, mixed, and fully reacted at 70° C. The stirring speed was 400 r / min. After the reaction time of 420 min, heating and stirring were stopped, and solid-liquid separation of the system was achieved by a vacuum filtration device.

[0066] The concentration of valuable metals in the leachate was detected by ICP analysis, and the calculated leaching rates of lithium, nickel, and cobalt were 88.9%, 92.3%, and 89.5%, respectively. The leaching rate of manganese was only 0.1%, and the leaching rates of impurities iron and aluminum were less than 1%. Apart from these, there was basically no other impurities. The leaching residue was enriched in valuable metal manganese, which existed in the form of manganese carbonate.

[0067] This comparative example adopts steps similar to those of Example 1, except that a single ammonium sulfite is used as a reducing agent, and no additional hydrated hydrazine is added for reduction leaching. Combining Example 1 and Comparative Example 1, it can be found that the reduction leaching rate of a single ammonium sulfite is not high, and nickel, cobalt, and lithium can only achieve good leaching at 70°C and 420 minutes, while the synergistic hydrated hydrazine reduction can significantly improve the metal leaching rate and reduce subsequent separation steps; this is because the addition of hydrated hydrazine reduces the potential value of the system, making the cobalt ammonia complex ions and nickel ammonia complex ions more stable in the solution, reducing the tendency of ion precipitation. At the same time, the reduction effect of ammonium sulfite and hydrated hydrazine promotes the leaching kinetics of nickel and cobalt, accelerates the leaching trend of nickel and cobalt, and enables efficient leaching to be achieved after 360 minutes of reaction; and to a certain extent, the leaching activation energy of nickel and cobalt is reduced, so that leaching can be completed under mild conditions of 60°C.

[0068] Comparative Example 2

[0069] The ammonia leaching recovery process of this comparative example has the following specific steps:

[0070] (1) preparing 1 L of a mixed solution of 0.7 mol / L ammonia water, 0.3 mol / L hydrazine hydrate, 0.05 mol / L ammonium sulfite, 1.41 mol / L ammonium bicarbonate and deionized water as the ammonia leachate for the reaction;

[0071] (2) The ammonia leaching solution obtained in step (1) was continuously stirred until the ammonium salt was completely dissolved, and then 20 g of waste ternary lithium-ion battery positive electrode powder material was added, mixed, and fully reacted at 60° C. The stirring speed was 400 r / min. After the reaction time of 360 min, heating and stirring were stopped, and solid-liquid separation of the system was achieved by a vacuum filtration device.

[0072] The concentration of valuable metals in the leachate was detected by ICP analysis, and the calculated leaching rates of lithium, nickel, and cobalt were 83.9%, 85.6%, and 80.5%, respectively. The leaching rate of manganese was 0.1%, and the leaching rates of impurities iron and aluminum were 3.7% and 2.9%, respectively. The valuable metal manganese was enriched in the leaching residue and existed in the form of manganese carbonate.

[0073] Through Example 1 and Comparative Example 2, it can be found that when hydrazine hydrate is used as the main reducing agent and ammonium sulfite is used for reduction leaching, the leaching rates of lithium, nickel and cobalt are not high. It is possible that excessive hydrazine hydrate reacts with ammonium bicarbonate, affecting the precipitation-dissolution equilibrium of the system. At the same time, the leaching rates of impurities iron and aluminum are also increased, indicating that hydrazine hydrate cannot be used as the main reducing agent.

[0074] Comparative Example 3

[0075] The ammonia leaching recovery process of this comparative example has the following specific steps:

[0076] (1) Prepare 1 L of a mixed solution of 2.1 mol / L ammonia water, 0.31 mol / L ammonium sulfite, and deionized water as the ammonia leaching solution for the reaction;

[0077] (2) The ammonia leaching solution obtained in step (1) was continuously stirred until the ammonium salt was completely dissolved, and then 20 g of waste ternary lithium-ion battery positive electrode powder material was added, mixed, and fully reacted at 60° C. The stirring speed was 400 r / min. After the reaction time of 360 min, heating and stirring were stopped, and solid-liquid separation of the system was achieved by a vacuum filtration device.

[0078] The concentration of valuable metals in the leachate was detected by ICP analysis, and the calculated leaching rates of lithium, nickel, and cobalt were 65.7%, 71.6%, and 67.5%, respectively. The leaching rate of manganese was 1.2%, and the leaching rates of impurity iron and aluminum were 3.6% and 4.9%, respectively.

[0079] Comparative Example 4

[0080] The ammonia leaching recovery process of this comparative example has the following specific steps:

[0081] (1) Prepare 1 L of a mixed solution of 0.7 mol / L ammonia water, 0.31 mol / L sodium sulfite, 0.048 mol / L hydrazine hydrate, 1.41 mol / L ammonium bicarbonate and deionized water as the ammonia leachate for the reaction;

[0082] (2) The ammonia leaching solution obtained in step (1) was continuously stirred until the ammonium salt was completely dissolved, and then 20 g of waste ternary lithium-ion battery positive electrode powder material was added, mixed, and fully reacted at 60° C. The stirring speed was 400 r / min. After the reaction time of 360 min, heating and stirring were stopped, and solid-liquid separation of the system was achieved by a vacuum filtration device.

[0083] The concentration of valuable metals in the leachate was detected by ICP analysis, and the calculated leaching rates of lithium, nickel, and cobalt were 92.4%, 93.3%, and 91.2%, respectively. The leaching rate of manganese was 2.9%, and the leaching rates of impurities iron and aluminum were 3.7% and 7.6%, respectively. Manganese was mainly present in the leaching residue in the form of manganese carbonate.

[0084] This comparative example uses steps similar to those of Example 1, except that sodium sulfite is used as the main reducing agent instead of ammonium sulfite, and hydrated hydrazine is used in conjunction with reduction leaching to explore the effect of the synergistic effect of this combination on the metal leaching rate. Combining Example 1 and Comparative Example 4, it was found that although sodium sulfite and hydrated hydrazine can effectively improve the metal leaching rate, the impurities iron and aluminum are also more leached into the solution, and the leaching of manganese is greatly increased, which is not conducive to the separation and purification of the post-leaching liquid. At the same time, it is proved that the ammonia leaching system of ammonium sulfite and ammonium bicarbonate is more suitable for the leaching of the ternary positive electrode material.

[0085] Comparative Example 5

[0086] The ammonia leaching recovery process of this comparative example has the following specific steps:

[0087] (1) Prepare 1 L of a mixed solution of 0.7 mol / L ammonia water, 0.31 mol / L ammonium sulfite, 0.05 mol / L ammonium thiosulfate, 1.41 mol / L ammonium bicarbonate and deionized water as the ammonia leachate for the reaction;

[0088] (2) The ammonia leaching solution obtained in step (1) was continuously stirred until the ammonium salt was completely dissolved, and then 20 g of waste ternary lithium-ion battery positive electrode powder material was added, mixed, and fully reacted at 60° C. The stirring speed was 400 r / min. After the reaction time of 360 min, heating and stirring were stopped, and solid-liquid separation of the system was achieved by a vacuum filtration device.

[0089] The concentration of valuable metals in the leachate was detected by ICP analysis, and the calculated leaching rates of lithium, nickel, and cobalt were 90.5%, 93.6%, and 91.1%, respectively. The leaching rate of manganese was 0.4%, and the leaching rates of impurities iron and aluminum were 0.3% and 0.3%, respectively. The leachate basically did not contain other impurities, while the leaching residue was enriched in valuable metal manganese in the form of manganese carbonate.

[0090] Combining Example 1 and Comparative Example 5, it was found that the addition of ammonium thiosulfate could not effectively improve the metal leaching rate in conjunction with ammonium sulfite, and the effect was not much different from that of adding ammonium sulfite alone.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An ammonia leaching recovery process using ammonium sulfite and hydrazine hydrate as reducing agents, characterized in that: The following steps are involved: mixing ammonia water, a reducing agent and a buffer to obtain an ammonia leaching solution; The ammonia leachate is mixed with the cathode powder of the waste ternary lithium ion battery to carry out a reduction reaction, and filtered to obtain a leachate and a manganese-containing leach residue; The reducing agents are ammonium sulfite and hydrazine hydrate.

2. The ammonia leaching recovery process according to claim 1, wherein The molar ratio of the ammonium sulfite to the hydrazine hydrate is (0.12-0.84): (0.016-0.08).

3. The ammonia leaching recovery process according to claim 1 or 2, characterized in that: The molar ratio of the ammonia water, the reducing agent and the buffer is (0.35-3.5): (0.12-0.84): (0.47-1.88).

4. The ammonia leaching recovery process according to claim 1 or 3, characterized in that: The buffer is at least one of ammonium carbonate, ammonium bicarbonate, ammonium sulfate and ammonium chloride.

5. The ammonia leaching recovery process according to claim 1, characterized in that: The pH value of the ammonia leaching solution is 8-10.

6. The ammonia leaching recovery process according to claim 1, characterized in that: The solid-liquid ratio of the ammonia leaching solution to the positive electrode powder of the waste ternary lithium ion battery is 10 to 50 g / L.

7. The ammonia leaching recovery process according to claim 1 or 6, characterized in that: The general formula of the waste ternary lithium ion battery positive electrode powder is Li(Ni x Co y Mn 1-x-y )O2, where x ranges from 0 to 1, y ranges from 0 to 1, and x+y ranges from 0 to 1.

8. The ammonia leaching recovery process according to claim 1, characterized in that: The reduction reaction conditions are: temperature of 25-70° C., time of 240-480 min, and rotation speed of 200-450 r / min.

9. A method for reducing the leaching of Mn element in waste ternary lithium-ion battery positive electrode materials, characterized in that: The ammonia leaching recovery process according to any one of claims 1 to 8 is used to treat waste ternary lithium-ion battery positive electrode materials.

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