Organic acid leaching regeneration method of waste nickel-zinc battery negative electrode material

Abstract

The invention provides an organic acid leaching regeneration method of a waste nickel-zinc battery negative electrode material, and belongs to the technical field of resource recycling and reutilization, and the method comprises the following steps: disassembling a waste nickel-zinc battery, separating to obtain a negative electrode sheet, and calcining to obtain negative electrode powder; placing the negative electrode powder in an organic acid solution, ultrasonically stirring to dissolve zinc, and filtering to obtain a leaching solution; adding sodium hydroxide particles into the leachate until white precipitates are generated, standing, filtering and drying to obtain a precursor, and calcining the precursor to obtain zinc oxide powder. According to the method, inorganic acid leaching is adopted, the regenerated product can be used for the nickel-zinc battery, and no waste liquid discharge can be realized. Compared with the prior art, the method has the advantages that organic acid which is small in environmental harm is used, almost no liquid is discharged, zinc can be effectively recycled, and the method is short in process and low in cost. The method has the characteristics of greenness, high efficiency and simple process, and is beneficial to further realization of commercialized development.

Description

Technical Field

[0001] The invention provides a method for organic acid leaching and regeneration of waste nickel-zinc battery negative electrode materials, belonging to the technical field of resource recovery and reuse. Background Art

[0002] Nickel-zinc batteries are expected to become a strong competitor to other secondary batteries such as lithium batteries due to their high operating voltage, high energy density, high power density, high cycle life, green and pollution-free, and high safety performance. They also show good application prospects in electronic products and the highly anticipated electric vehicle fields. The positive electrode of nickel-zinc batteries is nickel hydroxide, the negative electrode is zinc oxide, and the electrolyte is an alkaline aqueous solution. The abundance of zinc in the earth's crust is 70ppm. It is abundant and cheap, highly safe, non-toxic and pollution-free. As the use of nickel-zinc batteries increases, a large number of retired batteries will also be generated. If the waste batteries are not properly disposed of, it will cause a series of problems such as serious pollution and waste of resources. Therefore, the recycling and reuse of waste nickel-zinc batteries is particularly important.

[0003] At present, the research on the recycling of waste batteries mainly includes three categories: pyrometallurgy, hydrometallurgy and regeneration. Pyrometallurgy uses the different boiling points of various metals in waste batteries to separate and recycle them. It has problems such as high energy consumption and difficulty in obtaining high-value products, so it is insufficient in both economic and environmental benefits. Hydrometallurgy uses the different solubility of metals and their compounds in waste batteries in acidic, alkaline and other solvents to recycle and reuse the valuable metals through various treatment methods. Compared with pyrometallurgy, hydrometallurgy does not require high temperature and has low energy consumption, but it consumes a large amount of acid and alkali solutions, which is harmful to the environment. Summary of the invention

[0004] The purpose of the present invention is to provide a method for organic acid leaching and regeneration of waste nickel-zinc battery negative electrode materials, which is green, efficient, and simple in process, and is conducive to further commercial development. Organic acid is used in the leaching process, which not only has little harm to the environment, but also has excellent leaching effect on zinc. In the precipitation process, sodium hydroxide particles are added to effectively reduce the generation of waste liquid, and the precipitated liquid is sodium citrate after concentration.

[0005] The technical solution of the present invention is as follows: a method for organic acid leaching and regeneration of anode materials of waste nickel-zinc batteries, comprising the following steps: After disassembling the waste nickel-zinc battery, the negative electrode sheet is separated and calcined to obtain the negative electrode powder. The negative electrode powder is placed in an organic acid solution and ultrasonically stirred to dissolve the zinc, and then filtered to obtain a leachate. Sodium hydroxide particles are added to the leachate until a white precipitate is produced. After standing, filtering and drying, a precursor is obtained, and the precursor is calcined to obtain zinc oxide powder.

[0006] The specific steps include: (1) Disassemble the waste nickel-zinc battery to obtain the negative electrode sheet, dry it, and then calcine it at 500°C for 2 hours in an air atmosphere at a heating rate of 10°C / min to remove the binder and the conductive agent, and separate the negative electrode powder.

[0007] (2) Leaching the separated negative electrode powder with organic acid.

[0008] The organic acid can be one or more of oxalic acid, acetic acid, citric acid, and malic acid; the concentration of the organic acid is 0.01M~5M; the reaction temperature is 0℃~105℃; the reaction time is 30 minutes~3 hours; the solid-liquid ratio is 10g / L~100g / L; and the rotation speed is 100~1000r / min.

[0009] (3) The zinc content in the leaching solution was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES), and the zinc leaching rate was calculated according to the following formula.

[0010] , Where η% is the leaching rate of zinc; M is the mass of the raw material; m is the volume of the leachate; W% is the content of zinc in the raw material; and N is the content of zinc in the leachate.

[0011] (4) Add sodium hydroxide to the leaching solution until precipitation occurs, stir for 2 to 12 hours, filter, wash until neutral, and dry to obtain a precursor. The reaction temperature is 25°C to 85°C; the sodium hydroxide is in the form of granules / flakes or a solution (0.1 to 5 mol / L).

[0012] (5) The precursor is calcined in an air atmosphere to obtain zinc oxide. The calcination temperature is 200°C to 700°C, the calcination time is 1 to 5 hours, and the heating rate is 5 to 10°C / min.

[0013] (6) Add an organic acid to the filtrate obtained in step (4) to adjust the pH to 8-9, heat, concentrate and crystallize to obtain the corresponding sodium salt.

[0014] The present invention uses organic acid to leach the negative electrode material in waste nickel-zinc batteries for the first time without using a reducing agent. In the preparation method of zinc oxide and the conversion and recovery of waste liquid, the method of directly adding a precipitant can not only efficiently obtain a zinc oxide precursor, but also reduce the generation of waste liquid. And subsequently, sodium citrate with high purity can be obtained by adjusting the pH, heating, concentrating and crystallizing.

[0015] The present invention adopts inorganic acid leaching, and the regenerated product can be used for nickel-zinc batteries, and no waste liquid discharge can be achieved. The present invention is an improvement over the prior art in that an organic acid with little harm to the environment is used, and there is almost no liquid discharge. Not only can zinc be effectively recovered, but also the process is short and the cost is low. The present invention is green, efficient, and has a simple process, which is conducive to further commercial development. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a process flow chart of the present invention.

[0017] Figure 2 The XRD patterns of the products of the examples and comparative examples are shown in FIG.

[0018] Figure 3 This is the SEM image of zinc oxide in Example 1.

[0019] Figure 4 This is the XRD diagram of the concentrated crystal product in Example 1. DETAILED DESCRIPTION

[0020] The specific technical solution of the present invention is described in conjunction with the embodiments. The process of the present invention is as follows Figure 1 shown.

[0021] Example 1 After disassembling the waste nickel-zinc battery, the negative electrode sheet was separated. The binder and conductive agent were removed by heating at 500°C for 2 hours at a heating rate of 10°C / min in an air atmosphere, and the negative electrode powder was separated. Under the condition of a solid-liquid ratio of 10g / L, the negative electrode powder was ultrasonically dispersed in a 3 mol / L citric acid solution and then heated to 95°C. The mixture was stirred at 500r / min for 1 hour and filtered to obtain a leachate. At 25°C, sodium hydroxide particles were added to the leachate until a white precipitate appeared. The mixture was stirred for 8 hours, allowed to stand for 6 hours, filtered, and washed to obtain a precursor. The precursor was heated to 550°C in an air atmosphere at a heating rate of 10°C / min and calcined for 3 hours to obtain zinc oxide powder. Citric acid was added to the filtrate after precipitation, the pH was adjusted to 8.5, and sodium citrate was obtained by heating and concentrating. The leachate was tested by ICP-OES and calculated by formula (1) to obtain a zinc leaching rate of 99.6%.

[0022] Example 2 After disassembling the waste nickel-zinc battery, the negative electrode sheet was separated. The binder and conductive agent were removed by heating at 500°C for 2 hours at a heating rate of 10°C / min in an air atmosphere, and the negative electrode powder was separated. Under the condition of a solid-liquid ratio of 20g / L, the negative electrode powder was ultrasonically dispersed in a 2 mol / L citric acid solution and then heated to 65°C. The mixture was stirred at 500r / min for 1 hour and filtered to obtain a leachate. At 25°C, sodium hydroxide particles were added to the leachate until a white precipitate appeared. The mixture was stirred for 8 hours, allowed to stand for 6 hours, filtered, and washed to obtain a precursor. The precursor was heated to 550°C in an air atmosphere at a heating rate of 10°C / min and calcined for 1 hour to obtain zinc oxide powder. Citric acid was added to the filtrate after precipitation, the pH was adjusted to 8.5, and sodium citrate was obtained by heating and concentrating. The leachate was tested by ICP-OES and calculated by formula (1) to obtain a zinc leaching rate of 99.4%.

[0023] Example 3 After disassembling the waste nickel-zinc battery, the negative electrode sheet was separated. The binder and conductive agent were removed by heating at 500°C for 2 hours at a heating rate of 10°C / min in an air atmosphere, and the negative electrode powder was separated. Under the condition of a solid-liquid ratio of 30g / L, the negative electrode powder was ultrasonically dispersed in a 1 mol / L citric acid solution and then heated to 35°C. The mixture was stirred at 500r / min for 1 hour and filtered to obtain a leachate. At 25°C, sodium hydroxide particles were added to the leachate until a white precipitate appeared. The mixture was stirred for 8 hours, allowed to stand for 6 hours, filtered, and washed to obtain a precursor. The precursor was heated to 350°C in an air atmosphere at a heating rate of 10°C / min and calcined for 3 hours to obtain zinc oxide powder. Citric acid was added to the filtrate after precipitation, the pH was adjusted to 8.5, and the mixture was concentrated and crystallized by heating to obtain sodium citrate. The leachate was tested by ICP-OES and calculated by formula (1) to obtain a zinc leaching rate of 99.7%.

[0024] Example 4 After disassembling the waste nickel-zinc battery, the negative electrode sheet was separated. The binder and conductive agent were removed by heating at 500°C for 2 hours at a heating rate of 10°C / min in an air atmosphere, and the negative electrode powder was separated. Under the condition of a solid-liquid ratio of 50g / L, the negative electrode powder was ultrasonically dispersed in a 0.5 mol / L citric acid solution, and the reaction temperature was controlled to 5°C. The reaction was stirred at 500r / min for 1 hour, and the leaching solution was obtained after filtration. At 65°C, sodium hydroxide particles were added to the leaching solution until a white precipitate appeared. The mixture was stirred for 8 hours, allowed to stand for 6 hours, filtered, and washed to obtain a precursor. The precursor was heated to 550°C in an air atmosphere at a heating rate of 10°C / min and calcined for 3 hours to obtain zinc oxide powder. Citric acid was added to the filtrate after precipitation, the pH was adjusted to 8.5, and sodium citrate was obtained by heating and concentrating. The leaching rate of zinc was 99.6% as determined by ICP-OES test and formula (1).

[0025] Comparative Example 1 After disassembling the waste nickel-zinc battery, the negative electrode sheet was separated. The binder and conductive agent were removed at 500°C for 2 hours at a heating rate of 10°C / min in an air atmosphere, and the negative electrode powder was separated. Under the condition of a solid-liquid ratio of 30g / L, the negative electrode powder was ultrasonically dispersed in a 1 mol / L citric acid solution and then heated to 35°C. The reaction was stirred at 500r / min for 1 hour, and the leaching solution was obtained after filtration. At 25°C, 2 mol / L sodium hydroxide solution was added to the leaching solution until a white precipitate appeared. Stirring was continued for 8 hours, and the mixture was allowed to stand for 6 hours. The precursor was filtered and washed to obtain the precursor. The precursor was heated to 550°C at a heating rate of 10°C / min in an air atmosphere and calcined for 3 hours to obtain zinc oxide powder. Citric acid was added to the filtrate after precipitation, the pH was adjusted to 8.5, and sodium citrate was obtained by heating and concentrating.

[0026] Comparative Example 2 Disassemble the waste nickel-zinc battery and separate the negative electrode sheet. Keep the temperature at 500℃ for 2 hours at a heating rate of 10℃ / min in an air atmosphere to remove the binder and conductive agent, and separate the negative electrode powder. Under the condition of a solid-liquid ratio of 30g / L, the negative electrode powder is ultrasonically dispersed in a 1 mol / L citric acid solution and then heated to 35℃. React for 1 hour under stirring at 500r / min, and filter to obtain a leachate. At 25℃, add sodium hydroxide particles to the leachate until a white precipitate appears, continue stirring for 8 hours, let stand for 6 hours, filter and wash to obtain a precursor.

[0027] pass Figure 2From the XRD graphs in Example 1 and Example 4, zinc oxide can be obtained by calcining at 550°C for 3 hours, while the XRD graphs in Example 2 and Example 3 do not completely match the zinc oxide standard card, and there are slight differences in the crystal forms, indicating the importance of calcination temperature and calcination time. From the XRD of Example 1 and Comparative Example 1, it can be seen that the form of sodium hydroxide addition has no effect on the product. From the XRD of Example 1 and Comparative Example 2, it can be seen that the XRD curve of the uncalcined sample cannot match zinc oxide, indicating the necessity of the calcination step.

[0028] pass Figure 3 From the scanning electron microscope image in FIG. 1 , it can be seen that the zinc oxide in Example 1 is spherical particles of 5 μm to 10 μm.

[0029] Figure 4 The XRD results show that the product of the concentrated crystallization of the filtrate after precipitation in Example 1 is sodium citrate, which matches the standard card correctly and has no impurity peaks.

[0030] The present invention can achieve the leaching effect of inorganic acid by using organic acid leaching without adding a reducing agent, and has the advantages of being green and safe. Due to the stability and singleness of the raw materials, no impurity removal treatment is required after leaching, and the precursor can be directly precipitated and calcined. In addition, the filtrate after precipitation is heated, concentrated and crystallized after adjusting the pH, and this method can not only make the entire process flow without waste liquid discharge, but also produce an additional finished product.

Claims

1. A method for organic acid leaching and regeneration of waste nickel-zinc battery negative electrode materials, characterized in that: The method includes the following processes: disassembling waste nickel-zinc batteries to obtain negative electrode sheets, which are then calcined to obtain negative electrode powder; placing the negative electrode powder in an organic acid solution and ultrasonically stirring the solution to dissolve zinc, which is then filtered to obtain a leaching solution; adding sodium hydroxide particles to the leaching solution to produce a white precipitate, allowing the solution to stand, filtering, and drying to obtain a precursor, which is then calcined to obtain zinc oxide powder.

2. The method for organic acid leaching and regeneration of the negative electrode material of waste nickel-zinc batteries according to claim 1, characterized in that: The specific steps include: (1) Disassemble the waste nickel-zinc battery to obtain the negative electrode sheet, dry it, and calcine it at 500°C for 2 hours at a heating rate of 10°C / min in an air atmosphere to remove the binder and the conductive agent, and separate the negative electrode powder; (2) Leaching the separated negative electrode powder with organic acid; The concentration of organic acid is 0.01M ~ 5M; the reaction temperature is 0℃~105℃; the reaction time is 30 minutes~3 hours; the solid-liquid ratio is 10g / L~100g / L; the rotation speed is 100~1000r / min; (3) Analyze the zinc content in the leaching solution and calculate the zinc leaching rate; (4) Add sodium hydroxide to the leaching solution until precipitation occurs, stir for 2 to 12 hours, filter, wash until neutral, and dry to obtain a precursor; (5) calcining the precursor in an air atmosphere to obtain zinc oxide; (6) Add an organic acid to the filtrate obtained in step (4) to adjust the pH to 8-9, heat, concentrate and crystallize to obtain the corresponding sodium salt.

3. The method for organic acid leaching and regeneration of the negative electrode material of waste nickel-zinc batteries according to claim 2, characterized in that: The organic acid in step (2) can be one or more of oxalic acid, acetic acid, citric acid, and malic acid.

4. The method for organic acid leaching and regeneration of the negative electrode material of waste nickel-zinc batteries according to claim 2, characterized in that: In step (3), the zinc content in the leaching solution is analyzed by inductively coupled plasma emission spectrometry, and the zinc leaching rate is calculated according to the following formula; ， Where η% is the leaching rate of zinc; M is the mass of the raw material; m is the volume of the leachate; W% is the content of zinc in the raw material; and N is the content of zinc in the leachate.

5. The method for organic acid leaching and regeneration of the negative electrode material of waste nickel-zinc batteries according to claim 2, characterized in that: In step (4), the reaction temperature is 25°C to 85°C; the sodium hydroxide is in a granular / flaky state with a concentration of 0.1 to 5 mol / L.

6. The method for organic acid leaching and regeneration of the negative electrode material of waste nickel-zinc batteries according to claim 2, characterized in that: In step (5), the calcination temperature is 200°C to 700°C; the calcination time is 1 to 5 hours; and the heating rate is 5 to 10°C / min.

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