Method for leaching valuable metals from waste lithium ion batteries by using rice hulls

Abstract

The invention belongs to the technical field of waste lithium ion battery recovery, and particularly relates to a method for leaching valuable metals from waste lithium ion batteries by using rice hulls. The method comprises the following steps: 1) pretreatment: sequentially discharging, disassembling and crushing the retired ternary lithium ion battery, and sorting to obtain black powder containing a ternary positive electrode material; 2) grinding: putting the black powder obtained in the step 1) and rice hull powder into a ball mill according to a certain feeding ratio for ball milling and mixing to obtain mixed powder; 3) roasting: roasting the mixed powder at high temperature under protective gas to obtain roasted powder; and (4) acid leaching is conducted, specifically, the roasted powder is added into citric acid, leaching is conducted under the microwave heating condition, and a leaching solution is obtained. According to the method, the valuable metal is leached from the waste ternary lithium ion battery by using the rice husk as an auxiliary agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling waste lithium-ion batteries, and in particular relates to a method for leaching valuable metals from waste lithium-ion batteries using rice husks. Background Art

[0002] Traditional fossil energy is a non-renewable energy source. With the excessive use of fossil energy, energy security issues have become increasingly prominent. In addition, the use of traditional fossil energy is often accompanied by the emission of a large amount of air pollutants such as dust, sulfur dioxide, nitrogen oxides and carbon dioxide. Lithium-ion batteries are considered to be a substitute for traditional fossil energy due to their high energy density and rechargeability. The current mainstream lithium-ion battery positive electrode materials mainly include lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, etc. However, the capacity of lithium-ion batteries will gradually decay during use, and when their capacity decays to a certain extent, they need to be recycled.

[0003] At present, the mainstream methods for recycling waste lithium-ion batteries are pyrometallurgy and hydrometallurgy. Pyrometallurgy refers to placing waste batteries directly in a high-temperature smelting furnace and recycling them in the form of alloys at high temperatures. The process of pyrometallurgy is relatively simple, but the purity of the recycled metal materials is low, and further processing is required to meet the reuse standards; the generation of high-temperature conditions often requires huge energy consumption; and at high temperatures, organic matter such as electrolytes and binders in the battery will produce toxic gases. Therefore, pyrometallurgy is not suitable for the clean recycling of waste lithium-ion batteries. Hydrometallurgical process refers to the use of acid, alkali or biological solution to transfer valuable metals into the solution, and then separate different metal elements to obtain corresponding metal compounds. The positive electrode material has good stability, so it is often necessary to add additional reducing agents to assist the leaching of valuable metals during the leaching process. Traditional reducing additives include sulfites, hydrogen peroxide, etc. The introduction of reducing additives will not only increase the recycling cost, but also cause certain safety risks.

[0004] The main method for leaching valuable metals from positive electrode materials is acid leaching. However, the key to leaching valuable metals safely, efficiently and economically lies in the development of a green and inexpensive leaching reducing agent. Therefore, it is necessary to propose a method that can efficiently and greenly leach valuable metals from waste lithium-ion batteries. Summary of the invention

[0005] In order to solve the shortcomings of the prior art, the present invention provides a method for leaching valuable metals from waste lithium-ion batteries using rice husks. The present invention uses rice husks as an auxiliary agent to leach valuable metals from waste ternary lithium-ion batteries. The present invention is based on a safe, cheap and sustainable leaching auxiliary agent for valuable metals, thereby overcoming the disadvantages of high risk and high cost of traditional leaching reducing agents.

[0006] The technical solution provided by the present invention is as follows:

[0007] A method for leaching valuable metals from waste lithium-ion batteries using rice husks comprises the following steps:

[0008] 1) Pretreatment: Discharge, disassemble and crush retired ternary lithium-ion batteries in sequence to obtain black powder containing ternary positive electrode materials;

[0009] 2) Grinding: The black powder and rice husk powder obtained in step 1) are placed in a ball mill according to a certain feed ratio and mixed to obtain a mixed powder;

[0010] 3) Calcination: calcining the mixed powder at high temperature under protective gas to obtain calcined powder;

[0011] 4) Acid leaching: adding the roasted powder into citric acid, leaching under microwave heating conditions to obtain a leachate.

[0012] In the above technical solution:

[0013] The rice husk is an agricultural waste, and its main components are crude fiber, pentose polymers, pentosan, fat, protein and other organic substances and silicon dioxide;

[0014] Organic substances such as crude fiber, pentose polymer, pentosan, fat, protein, etc. in rice husk adjuvant are cracked into reducing gases such as carbon monoxide, hydrogen, and methane at high temperature. The reducing gases react with the positive electrode material to destroy the structure of the positive electrode material.

[0015] The silicon dioxide in the rice husk adjuvant reacts with oxygen and water under the action of microwaves to generate superoxide radicals and hydroxyl radicals, which promote the reduction of the nickel positive electrode material.

[0016] Specifically, in step 1): the ternary lithium-ion battery is a nickel-cobalt-manganese ternary lithium-ion battery.

[0017] Specifically, in step 1), the discharge time in saturated sodium chloride is more than 48 hours.

[0018] Specifically, in step 2): the rice husk is agricultural waste, and its main components include crude fiber, pentose polymer, pentosan, fat, protein and silicon dioxide.

[0019] Specifically, the mass ratio of rice husk to black powder for grinding is (0.5-2):1, and the grinding time is 6-10 hours.

[0020] Specifically, in step 3), the roasting protective gas is one of nitrogen and argon, the roasting temperature is 300-650° C., and the roasting time is 15-75 min.

[0021] Specifically, in step 4), the concentration of citric acid is 0.25-2 mol / L.

[0022] In the above technical solution, citric acid provides an acidic environment for the leaching reaction, and citric acid can chelate with valuable metal elements to promote the leaching of valuable metals.

[0023] Specifically, in step 4), the leaching temperature is 20-100° C., the solid-liquid ratio is 0-30 ml / g, and the leaching time is 5-100 min.

[0024] Specifically, the leaching reaction in step 4) is carried out under stirring conditions at a stirring speed of 200 to 400 r / min.

[0025] Specifically, in step 3), crude fiber, pentose polymers, pentosans, fats and proteins in rice husks are cracked into carbon monoxide, hydrogen or methane under high temperature roasting, and carbon monoxide, hydrogen or methane react with the positive electrode material to reduce the structure of the positive electrode material.

[0026] Specifically, in step 4), silicon dioxide in rice husk reacts with oxygen and water under the action of microwaves to generate superoxide radicals and hydroxyl radicals, and the superoxide radicals and hydroxyl radicals promote the reduction of nickel positive electrode materials.

[0027] Specifically, in step 4), the obtained leaching solution contains Li, Ni, Co and Mn elements.

[0028] Furthermore, the method comprises step 5), using an organic filter membrane to separate the leaching liquid and the leaching residue.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention uses rice husks as an auxiliary agent to leach valuable metals from waste lithium-ion batteries. The high-valent metals in the positive electrode material are reduced to low-valent metal oxides or metal elements by using reducing gases such as carbon monoxide, hydrogen, and methane generated by the cracking of organic matter such as crude fiber, pentose polymers, pentosans, fats, and proteins in the rice husks at high temperatures, thereby destroying the structure of the positive electrode material and promoting the leaching of valuable metals. In addition, the silicon dioxide contained in the rice husks can react with oxygen and water under microwave conditions to generate superoxide radicals and hydroxyl radicals, which is beneficial to the reduction and leaching of organic metals. The advantage of this system is that the biomass waste rice husk is selected as a leaching auxiliary agent. Compared with traditional reducing agents, rice husks are widely available and inexpensive, which not only ensures a higher leaching rate of valuable metals, but also reduces the recycling cost, and makes the recycling process green, safe and sustainable. DETAILED DESCRIPTION

[0031] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0032] Unless otherwise specified, the test methods used in the embodiments of the present invention are conventional methods; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0033] Obtaining raw materials

[0034] The waste nickel-cobalt-manganese ternary lithium-ion battery was placed in a saturated sodium chloride solution for discharge for hours, and the discharged battery was manually disassembled to obtain the positive electrode sheet, which was placed in a planetary ball mill for 6 hours. After the ball milling was completed, the powder was sorted to remove large pieces of aluminum foil, and passed through a 200-mesh sieve and sieved to obtain black powder containing nickel-cobalt-manganese oxide. The valuable metal components (W / %) in the obtained black powder are shown in Table 1.

[0035] Table 1 Raw material composition (W / %)

[0036]

[0037] Example 1

[0038] This embodiment provides a method for leaching valuable metals from waste lithium-ion batteries using rice husks as an auxiliary agent, comprising the following steps:

[0039] (1) Take 0.5 g of the black powder obtained above and 0.5 g of rice husk powder, blend them and place them in a planetary ball mill for 8 h.

[0040] (2) The ball-milled mixed powder was placed in a tube furnace and calcined at 550° C. for 75 min in a nitrogen atmosphere.

[0041] (3) Prepare 1 mol / L citric acid, take 20 ml of 1 mol / L citric acid and mix it with the powder calcined in step 2, add it into a round-bottom flask, and react at 80° C., rotation speed 200 r / min, and microwave conditions for 60 min.

[0042] (4) The leaching solution of step (3) is filtered to obtain a filtrate, and the contents of Li, Ni, Co, and Mn elements in the filtrate are measured to obtain a leaching rate, as shown in Table 2 below.

[0043] Table 2 Example 1 Leaching rate (%)

[0044]

[0045] Example 2

[0046] In contrast, this embodiment provides a method for leaching valuable metals from waste lithium-ion batteries, comprising the following steps:

[0047] (1) 0.5 g of the black powder obtained above was placed in a tube furnace and calcined at 550° C. for 75 min in a nitrogen atmosphere.

[0048] (2) Prepare 1 mol / L citric acid, take 10 ml of 1 mol / L citric acid and mix it with the powder calcined in step 2, add it into a round-bottom flask, and react it at 80° C., rotation speed 200 r / min, and microwave conditions for 60 min.

[0049] (3) The leaching solution of step (2) is filtered to obtain a filtrate, and the contents of Li, Ni, Co, and Mn elements in the filtrate are measured to obtain a leaching rate, as shown in Table 3 below.

[0050] Table 3 Example 2 Leaching rate (%)

[0051]

[0052] Example 3

[0053] For comparison, the present embodiment provides a method for leaching valuable metals from waste lithium-ion batteries using rice husks as an auxiliary agent, comprising the following steps:

[0054] (1) Take 0.5 g of the black powder obtained above and 0.5 g of rice husk powder, blend them and place them in a planetary ball mill for 8 h.

[0055] (2) Prepare 1 mol / L citric acid. Take 20 ml of 1 mol / L citric acid and mix it with the powder after ball milling in step 2. Add it into a round-bottom flask and react it at 80° C., rotation speed 200 r / min, and microwave conditions for 60 min.

[0056] (3) The leaching solution of step (2) is filtered to obtain a filtrate, and the contents of Li, Ni, Co, and Mn elements in the filtrate are measured to obtain a leaching rate, as shown in Table 4 below.

[0057] Table 4 Example 3 Leaching rate (%)

[0058]

[0059] Example 4

[0060] In contrast, this embodiment provides a method for leaching valuable metals from waste lithium-ion batteries using rice husks as an auxiliary agent, comprising the following steps:

[0061] (1) Take 0.5 g of the black powder obtained above and 0.5 g of rice husk powder, blend them and place them in a planetary ball mill for 8 h.

[0062] (2) The ball-milled mixed powder was placed in a tube furnace and calcined at 550° C. for 75 min in a nitrogen atmosphere.

[0063] (3) Prepare 1 mol / L citric acid. Take 20 ml of 1 mol / L citric acid and mix it with the powder calcined in step 2 and add it into a round-bottom flask. React at 25° C., 200 r / min, and microwave conditions for 60 min.

[0064] (4) The leaching solution of step (3) is filtered to obtain a filtrate, and the contents of Li, Ni, Co, and Mn elements in the filtrate are measured to obtain a leaching rate, as shown in Table 5 below.

[0065] Table 5 Example 4 Leaching rate (%)

[0066]

[0067] Example 5

[0068] In contrast, this embodiment provides a method for leaching valuable metals from waste lithium-ion batteries using rice husks as an auxiliary agent, comprising the following steps:

[0069] (1) Take 0.5 g of the black powder obtained above and 0.5 g of rice husk powder, blend them and place them in a planetary ball mill for 8 h.

[0070] (2) The ball-milled mixed powder was placed in a tube furnace and calcined at 550° C. for 75 min in a nitrogen atmosphere.

[0071] (3) Prepare 1 mol / L citric acid. Take 20 ml of 1 mol / L citric acid and mix it with the powder calcined in step 2 and add it into a round-bottom flask. React at 80° C. and 200 r / min for 60 min.

[0072] (4) The leaching solution of step (3) is filtered to obtain a filtrate, and the contents of Li, Ni, Co, and Mn elements in the filtrate are measured to obtain a leaching rate, as shown in Table 6 below.

[0073] Table 6 Example 5 Leaching rate (%)

[0074]

[0075] Example 6

[0076] In contrast, this embodiment provides a method for leaching valuable metals from waste lithium-ion batteries using glucose as an auxiliary agent, comprising the following steps:

[0077] (1) Take 0.5 g of the black powder obtained above and 0.5 g of glucose, blend them and place them in a planetary ball mill for 8 h.

[0078] (2) The ball-milled mixed powder was placed in a tube furnace and calcined at 550° C. for 75 min in a nitrogen atmosphere.

[0079] (3) Prepare 1 mol / L citric acid, take 20 ml of 1 mol / L citric acid and mix it with the powder calcined in step 2, add it into a round-bottom flask, and react at 80° C., rotation speed 200 r / min, and microwave conditions for 60 min.

[0080] (4) The leaching solution of step (3) is filtered to obtain a filtrate, and the contents of Li, Ni, Co, and Mn elements in the filtrate are measured to obtain a leaching rate, as shown in Table 6 below.

[0081] Table 7 Example 6 Leaching rate (%)

[0082]

[0083] Example 7

[0084] In contrast, this embodiment provides a method for leaching valuable metals from waste lithium-ion batteries using glucose and silicon dioxide as auxiliary agents, comprising the following steps:

[0085] (1) Take 0.5 g of the black powder obtained above, 0.4 g of glucose and 0.1 g of silicon dioxide, blend them and place them in a planetary ball mill for 8 h.

[0086] (2) The ball-milled mixed powder was placed in a tube furnace and calcined at 550° C. for 75 min in a nitrogen atmosphere.

[0087] (3) Prepare 1 mol / L citric acid, take 20 ml of 1 mol / L citric acid and mix it with the powder calcined in step 2, add it into a round-bottom flask, and react at 80° C., rotation speed 200 r / min, and microwave conditions for 60 min.

[0088] (4) The leaching solution of step (3) is filtered to obtain a filtrate, and the contents of Li, Ni, Co, and Mn elements in the filtrate are measured to obtain a leaching rate, as shown in Table 6 below.

[0089] Table 8 Example 7 Leaching rate (%)

[0090]

[0091] Example 8

[0092] In contrast, this embodiment provides a method for leaching valuable metals from waste lithium-ion batteries using rice husks as an auxiliary agent, comprising the following steps:

[0093] (1) Take 0.5 g of the black powder obtained above and 0.5 g of rice husk powder, blend them and place them in a planetary ball mill for 8 h.

[0094] (2) The ball-milled mixed powder was placed in a tube furnace and calcined at 550° C. for 75 min in a nitrogen atmosphere.

[0095] (3) Prepare 1 mol / L phosphoric acid, take 20 ml of 1 mol / L phosphoric acid and mix it with the powder calcined in step 2, add it into a round-bottom flask, and react at 80° C., rotation speed 200 r / min, and microwave conditions for 60 min.

[0096] (4) The leaching solution of step (3) is filtered to obtain a filtrate, and the contents of Li, Ni, Co, and Mn elements in the filtrate are measured to obtain a leaching rate, as shown in Table 2 below.

[0097] Table 9 Example 8 Leaching rate (%)

[0098]

[0099]

[0100] It can be seen from the above examples that the present invention provides a method for leaching valuable metals from a ternary positive electrode material using rice husks as an auxiliary agent. Examples 1-5 can all leach valuable metals from positive electrode materials. The leaching rate of using rice husks as an auxiliary agent in Example 1 is higher than that of Example 2 without adding rice husks for roasting and Example 3 without roasting. It is further explained that the use of rice husks as an auxiliary agent can effectively destroy the structure of the ternary positive electrode material, which is conducive to the leaching of valuable metals. Compared with the use of rice husks as an auxiliary agent in Example 1, the leaching in Example 4 under room temperature is low, indicating that the leaching reaction of the present invention needs to be carried out under certain temperature conditions. Compared with the use of rice husks as an auxiliary agent in Example 1, Example 5 is not leached under a microwave environment, and Example 6 uses glucose to replace rice husks, and the leaching rate is low; in Example 7, glucose and silicon dioxide are used to replace rice husks, and the leaching rate is equivalent, indicating that the silicon dioxide in the rice husks in the microwave environment in the present invention promotes the leaching of valuable metals. Compared with Example 1, in which citric acid is used as a leaching agent, Example 8 uses phosphoric acid as a leaching agent, and the leaching rate is lower, indicating that the chelating ability of citric acid can promote the leaching of valuable metals. It can be seen that the present invention uses biomass rice husks as an additive and citric acid as a leaching agent to effectively improve the leaching efficiency of valuable metals in the positive electrode material of waste ternary lithium-ion batteries.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for leaching valuable metals from waste lithium-ion batteries using rice husks, characterized in that: The following steps are involved: 1) Pretreatment: Discharge, disassemble and crush retired ternary lithium-ion batteries in sequence to obtain black powder containing ternary positive electrode materials; 2) Grinding: The black powder and rice husk powder obtained in step 1) are placed in a ball mill according to a certain feed ratio and mixed to obtain a mixed powder; 3) Calcination: calcining the mixed powder at high temperature under protective gas to obtain calcined powder; 4) Acid leaching: adding the roasted powder into citric acid, leaching under microwave heating conditions to obtain a leachate.

2. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to claim 1, characterized in that: In step 1): the ternary lithium-ion battery is a nickel-cobalt-manganese ternary lithium-ion battery.

3. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to claim 1, characterized in that: In step 2), the rice husk is agricultural waste, and its main components include crude fiber, pentose polymer, pentosan, fat, protein and silicon dioxide.

4. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to claim 3, characterized in that: The mass ratio of rice husk to black powder for grinding is (0.5-2):

1.

5. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to claim 1, characterized in that: In step 3), the roasting protective gas is one of nitrogen and argon, the roasting temperature is 300-650° C., and the roasting time is 15-75 min.

6. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to claim 1, characterized in that: In step 4), the concentration of citric acid is 0.25-2 mol / L.

7. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to claim 6, characterized in that: In step 4), the leaching temperature is 20-100° C., the solid-liquid ratio is 0-30 ml / g, and the leaching time is 5-100 min.

8. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to claim 1, characterized in that: In step 3), crude fiber, pentose polymer, pentosan, fat and protein in rice husk are cracked into carbon monoxide, hydrogen or methane under high temperature roasting, and carbon monoxide, hydrogen or methane react with positive electrode material to reduce and destroy the structure of positive electrode material.

9. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to claim 1, characterized in that: In step 4), silicon dioxide in rice husk reacts with oxygen and water under the action of microwaves to generate superoxide radicals and hydroxyl radicals, which promote the reduction of nickel positive electrode materials.

10. The method for leaching valuable metals from waste lithium-ion batteries using rice husks according to any one of claims 1 to 9, characterized in that: In step 4), the obtained leaching solution contains Li, Ni, Co and Mn elements.

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