Method for regenerating negative electrode materials of waste nickel-zinc batteries by organic acid leaching

Abstract

The present invention provides a method for organic acid leaching and regeneration of negative electrode materials of waste nickel-zinc batteries, belonging to the field of resource recovery and reuse technology, and comprising the following steps: disassembling the waste nickel-zinc batteries to separate the negative electrode sheets, calcining to obtain negative electrode powder; placing the negative electrode powder in an organic acid solution and ultrasonically stirring to dissolve the zinc, filtering to obtain a leachate; adding sodium hydroxide particles to the leachate until a white precipitate is produced, standing, filtering, and drying to obtain a precursor, and calcining the precursor to obtain zinc oxide powder. The present invention uses inorganic acid leaching, and the regenerated product can be used in nickel-zinc batteries, and no waste liquid is discharged. The present invention improves upon the prior art in that it uses an organic acid with little environmental harm and almost no liquid discharge, effectively recovering zinc while also having the advantages of a short process and low cost. The present invention is green, efficient, and has a simple process, which is conducive to further commercial 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 (NZN) are expected to become a strong competitor to lithium batteries and other secondary batteries due to their high operating voltage, high energy density, high power density, long cycle life, environmental friendliness, and safety. They also show promising application prospects in electronics and the highly anticipated electric vehicle sector. NiZN batteries use nickel hydroxide as the positive electrode, zinc oxide as the negative electrode, and an alkaline aqueous electrolyte. Zinc, abundant in the Earth's crust at 70 ppm, is a highly safe, non-toxic, and low-cost resource. As the use of NZN batteries increases, a large number of retired batteries will be generated. If these batteries are not properly disposed of, they will cause serious pollution and resource waste. Therefore, the recycling and reuse of used NZN batteries is extremely important.

[0003] At present, the research on the recycling of waste batteries mainly falls into three categories: pyrometallurgy, hydrometallurgy, and regeneration. Pyrometallurgy uses the different boiling points of the metals in waste batteries to separate and recover them. However, it has problems such as high energy consumption and difficulty in obtaining high-value products. Therefore, 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 lower energy consumption, but it consumes large amounts of acid and alkali solutions, which is harmful to the environment. Summary of the Invention

[0004] The present invention aims to provide a method for regenerating spent nickel-zinc battery negative electrode materials through organic acid leaching. This method is environmentally friendly, efficient, and simple to manufacture, facilitating further commercialization. The use of organic acids in the leaching process not only minimizes environmental damage but also significantly improves zinc leaching efficiency. The addition of sodium hydroxide granules during the precipitation process effectively reduces waste liquid generation, and the precipitated liquid, upon concentration, becomes sodium citrate.

[0005] The technical solution of the present invention is as follows: a method for organic acid leaching and regeneration of waste nickel-zinc battery negative electrode materials, comprising the following steps:

[0006] After disassembling used nickel-zinc batteries, the negative electrode sheets are separated and calcined to obtain negative electrode powder. The negative electrode powder is placed in an organic acid solution and ultrasonically stirred to dissolve the zinc. The leaching solution is filtered to obtain a leachate. Sodium hydroxide particles are added to the leachate until a white precipitate forms. The solution is allowed to stand, filtered, and dried to obtain a precursor, which is then calcined to obtain zinc oxide powder.

[0007] The specific steps include:

[0008] (1) Disassemble the waste nickel-zinc battery to obtain the negative electrode sheet, dry it, and calcine it at 500℃ for 2 hours at a heating rate of 10℃ / min in air atmosphere to remove the binder and conductive agent, and separate the negative electrode powder.

[0009] (2) Leaching the separated negative electrode powder with organic acid.

[0010] 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.

[0011] (3) The zinc content in the leachate was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES), and the zinc leaching rate was calculated according to the following formula.

[0012] ,

[0013] Where η% is the zinc leaching rate; M is the mass of the raw material; m is the volume of the leachate; W% is the zinc content in the raw material; and N is the zinc content in the leachate.

[0014] (4) Add sodium hydroxide to the leachate until precipitation occurs, stir for 2-12 hours, filter, wash until neutral, and dry to obtain a precursor. The reaction temperature is 25°C-85°C; the sodium hydroxide is in the form of granules / flakes or a solution (0.1-5 mol / L).

[0015] (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.

[0016] (6) Add organic acid to the filtrate obtained by filtration in step (4) to adjust the pH to 8-9, heat, concentrate and crystallize to obtain the corresponding sodium salt.

[0017] This invention is the first to utilize organic acids to leach negative electrode materials from used nickel-zinc batteries without the use of reducing agents. In the zinc oxide preparation method and waste liquid conversion and recovery, the direct addition of a precipitant not only efficiently yields a zinc oxide precursor but also reduces waste liquid generation. Subsequent pH adjustment, followed by heating, concentration, and crystallization, yields high-purity sodium citrate.

[0018] The present invention utilizes inorganic acid leaching, and the regenerated product can be used in nickel-zinc batteries, with zero waste liquid discharge. This invention improves upon existing technologies by utilizing organic acids with minimal environmental impact and virtually no liquid discharge. This not only effectively recovers zinc, but also offers the advantages of a short process and low cost. This invention is environmentally friendly, highly efficient, and has a simple process, facilitating further commercialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the present invention.

[0020] Figure 2 The XRD patterns of the products of Examples and Comparative Examples are shown in FIG.

[0021] Figure 3 This is the SEM image of zinc oxide in Example 1.

[0022] Figure 4 This is the XRD pattern of the concentrated crystallized product in Example 1. DETAILED DESCRIPTION

[0023] The specific technical solutions of the present invention are described in conjunction with the embodiments. The process of the present invention is as follows Figure 1 shown.

[0024] Example 1

[0025] 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 in an air atmosphere at a heating rate of 10°C / min, and the negative electrode powder was separated. Under the condition of a solid-liquid ratio of 10 g / L, the negative electrode powder was ultrasonically dispersed in a 3 mol / L citric acid solution, heated to 95°C, stirred at 500 r / min for 1 hour, and filtered to obtain a leachate. Sodium hydroxide particles were added to the leachate at 25°C 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 the solution was concentrated by heating and crystallized to obtain sodium citrate. The leachate was tested by ICP-OES and calculated according to formula (1), and the zinc leaching rate was 99.6%.

[0026] Example 2

[0027] 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, heated to 65°C, stirred at 500r / min for 1 hour, and filtered to obtain a leachate. Sodium hydroxide particles were added to the leachate at 25°C 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 the solution was concentrated by heating and crystallized to obtain sodium citrate. The leachate was tested by ICP-OES and calculated according to formula (1), and the zinc leaching rate was 99.4%.

[0028] Example 3

[0029] 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 in an air atmosphere at a heating rate of 10°C / min, 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, heated to 35°C, 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 solution was concentrated by heating and crystallized to obtain sodium citrate. The leachate was tested by ICP-OES and calculated according to formula (1), and the zinc leaching rate was 99.7%.

[0030] Example 4

[0031] 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 in an air atmosphere at a heating rate of 10°C / min, 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. The reaction temperature was controlled to 5°C, and the reaction was stirred at 500r / min for 1 hour. The leachate was filtered to obtain a leachate. Sodium hydroxide particles were added to the leachate at 65°C 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 the mixture was concentrated and crystallized by heating to obtain sodium citrate. The leachate was tested by ICP-OES and calculated according to formula (1), and the zinc leaching rate was 99.6%.

[0032] Comparative Example 1

[0033] Scrap nickel-zinc batteries were disassembled and the negative electrode sheets separated. The binder and conductive agent were removed by heating the solution at 500°C in air at a rate of 10°C / min for 2 hours, resulting in the separation of the negative electrode powder. The negative electrode powder was ultrasonically dispersed in a 1 mol / L citric acid solution at a solid-to-liquid ratio of 30 g / L. The solution was then heated to 35°C and stirred at 500 rpm for 1 hour. The leachate was filtered to obtain a 2 mol / L sodium hydroxide solution at 25°C until a white precipitate formed. The solution 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 air at a rate of 10°C / min and calcined for 3 hours to obtain zinc oxide powder. Citric acid was added to the filtrate to adjust the pH to 8.5, and the solution was concentrated by heating to obtain sodium citrate.

[0034] Comparative Example 2

[0035] After disassembling used nickel-zinc batteries, the negative electrode sheets were separated. The binder and conductive agent were removed by heating the solution at 500°C in air at a rate of 10°C / min for 2 hours, resulting in the separation of the negative electrode powder. The negative electrode powder was ultrasonically dispersed in a 1 mol / L citric acid solution at a solid-to-liquid ratio of 30 g / L. The solution was then heated to 35°C and stirred at 500 rpm for 1 hour. The resulting leachate was filtered and then added with sodium hydroxide pellets at 25°C until a white precipitate formed. The solution was stirred for 8 hours, allowed to stand for 6 hours, and then filtered and washed to obtain the precursor.

[0036] pass Figure 2As can be seen from the XRD patterns in Example 1 and Example 4, zinc oxide can be obtained by calcining at 550°C for 3 hours, while the XRD patterns in Example 2 and Example 3 do not completely match the zinc oxide standard card, with slight differences in crystal form, indicating the importance of calcination temperature and time. The XRD patterns of Example 1 and Comparative Example 1 show that the form of sodium hydroxide added has no effect on the product. The XRD patterns of Example 1 and Comparative Example 2 show that the XRD curve of the uncalcined sample does not match that of zinc oxide, indicating the necessity of the calcination step.

[0037] pass Figure 3 The scanning electron microscope image in FIG shows that the zinc oxide in Example 1 is spherical particles of 5 μm to 10 μm.

[0038] 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.

[0039] The present invention utilizes organic acid leaching without the addition of a reducing agent, achieving the same leaching effect as inorganic acid leaching while also being environmentally friendly and safe. Due to the stability and homogeneity of the raw materials, precipitation and calcination of the precursor can proceed directly after leaching without requiring any impurity removal. Furthermore, sodium citrate is obtained by adjusting the pH of the filtrate after precipitation, followed by heating, concentration, and crystallization. This approach not only eliminates wastewater discharge throughout the entire process but also provides 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 comprises the following steps: disassembling waste nickel-zinc batteries to obtain negative electrode sheets, calcining the sheets to obtain negative electrode powder; placing the negative electrode powder in an organic acid solution with ultrasonic stirring to dissolve zinc, and filtering the solution to obtain a leachate; adding sodium hydroxide particles to the leachate to produce a white precipitate, allowing the solution to stand, filtering, and drying to obtain a precursor, and calcining the precursor to obtain zinc oxide powder; The specific steps include: (1) Dismantle 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 air atmosphere to remove the binder and conductive agent, and separate to obtain the negative electrode powder; (2) Leaching the separated negative electrode powder with an organic acid; the organic acid is one or more of oxalic acid, acetic acid, citric acid, and malic acid; The concentration of the organic acid is 0.01M to 5M; the reaction temperature is 0°C to 105°C; the reaction time is 30 minutes to 3 hours; the solid-liquid ratio is 10g / L to 100g / L; the rotation speed is 100 to 1000r / min; (3) Analyze the zinc content in the leachate and calculate the zinc leaching rate; (4) adding sodium hydroxide to the leachate until precipitation occurs, stirring for 2 to 12 hours, filtering, washing to neutrality, and drying to obtain a precursor; (5) calcining the precursor in an air atmosphere to obtain zinc oxide; (6) adding an organic acid to the filtrate obtained by filtration in step (4) to adjust the pH to 8-9, heating, concentrating and crystallizing to obtain the corresponding sodium salt; In step (3), the zinc content in the leachate is analyzed by inductively coupled plasma emission spectrometry, and the zinc leaching rate is calculated according to the following formula; Where η% is the zinc leaching rate; M is the weight of the raw material; m is the volume of the leachate; W% is the zinc content in the raw material; N is the zinc content in the leachate; The reaction temperature in step (4) is 25°C to 85°C; In step (5), the calcination temperature is 550° C.; the calcination time is 3 hours; and the heating rate is 10° C. / min.

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