A green and efficient method for separating waste aluminum plastic film

Abstract

This invention relates to a green and efficient method for separating waste aluminum-plastic film, belonging to the field of solid waste resource utilization and secondary resource recycling technology. The method involves preparing a dissociation solution: first, a 0.02-0.05 mol / L citric acid aqueous solution is prepared, then 0.5-2.0 g / L fatty alcohol polyoxyethylene ether is added and mixed thoroughly to obtain the dissociation solution; the waste aluminum-plastic film is crushed to obtain square fragments; the dissociation solution is poured onto the square fragments to wet them, and after air drying, they are pretreated to obtain square fragments of aluminum-plastic film waste; the pretreated square fragments are added to the dissociation solution and stirred for leaching, causing interfacial dissociation between the plastic film and aluminum foil, resulting in a mixture of aluminum foil and plastic film; after washing the mixture, the film and aluminum foil are separated by hydraulic flotation. This invention requires only a low-concentration citric acid aqueous solution and a small amount of fatty alcohol polyoxyethylene ether (AEO-9) to achieve green and efficient separation of waste aluminum-plastic film.

Description

Technical Field

[0001] This invention relates to a green and efficient method for separating waste aluminum-plastic film, belonging to the field of solid waste resource utilization and secondary resource recycling technology. Background Technology

[0002] Aluminum-plastic film is an important barrier and encapsulation material for energy storage lithium batteries. With the rapid and substantial increase in the number of retired energy storage lithium batteries, the resource recycling of aluminum-plastic film waste has become a crucial link in the secondary resource recycling process. However, existing recycling processes generally employ pyrolysis, which has the following prominent problems: 1. High energy consumption and cost: It needs to operate continuously at high temperatures of 400℃~600℃, and inert gases such as nitrogen are often introduced for protection against oxidation, which consumes a lot of energy and has high operating costs.

[0003] 2. Incomplete plastic removal: The pyrolysis process relies on the vaporization and volatilization of plastic to achieve separation, requiring extremely precise temperature control. Too low a temperature will cause the plastic to carbonize and coke, remaining on the aluminum foil surface, resulting in incomplete separation and reduced purity of the recycled aluminum; too high a temperature will easily cause the aluminum foil to curl and deform or partially melt, affecting the quality of metal recycling.

[0004] 3. Heavy pollution and high investment: High-temperature pyrolysis of plastics produces harmful gases such as hydrogen chloride, requiring expensive and complex exhaust gas purification systems, resulting in significant environmental pressure.

[0005] Wet processing methods for aluminum-plastic film are gradually attracting attention. In wet processing, sulfuric acid or phosphoric acid is used as an inorganic leaching agent, while organic leaching agents, such as acetic acid, are also used. Patent application number 2024115924256 describes an aluminum-plastic film delamination stripping agent and its preparation and application methods. This invention uses a mixed solution of 75-85% acetic acid, 2-5% sodium dodecylbenzenesulfonate, and 12-20% anhydrous ethanol and petroleum ether as the aluminum-plastic film delamination stripping agent. The invention also discloses citric acid as a stripping agent, with the following raw material composition and weight percentage: 75% citric acid, 5% sodium dodecylbenzenesulfonate, and 20% a mixed solution of anhydrous ethanol and petroleum ether in a volume ratio of 1:2.5. The above-mentioned aluminum-plastic film delamination stripping agents are organic solvents composed of anhydrous ethanol and petroleum ether. The high amount of citric acid and high concentration of organic acid require high equipment corrosion resistance, and acidic substances easily remain on the surface of the peeled plastic film, affecting subsequent resource utilization.

[0006] Therefore, there is an urgent need for a low-consumption, clog-proof, green method for the dissociation and recycling of aluminum-plastic films that can achieve aluminum-plastic separation. Summary of the Invention

[0007] To address the problems and shortcomings of the existing technologies, this invention provides a green and efficient method for separating waste aluminum-plastic film. This invention uses only a 0.02-0.05 mol / L citric acid aqueous solution combined with a small amount of fatty alcohol polyoxyethylene ether (AEO-9) as a composite dissociation agent to achieve efficient separation of waste aluminum-plastic film. This method utilizes the dissolving effect of citric acid on the oxide layer on the surface of the aluminum foil in the intermediate layer of the aluminum-plastic film, combined with the low surface tension penetration, hydrogen bonding, and solubilizing and emulsifying properties of (AEO-9), to achieve green and efficient separation of waste aluminum-plastic film. This invention is achieved through the following technical solutions.

[0008] A green and efficient method for separating waste aluminum-plastic film includes the following steps: (1) Preparation of dissociation solution: First, prepare a citric acid aqueous solution with a concentration of 0.02~0.05mol / L, then add 0.5~2.0g / L fatty alcohol polyoxyethylene ether, and mix evenly to obtain the dissociation solution; (2) The aluminum-plastic film waste is crushed to obtain square fragments of aluminum-plastic film waste; (3) Spray dissociation liquid into the square fragment aluminum-plastic film waste, wet the square fragment aluminum-plastic film waste, and pre-treat it after air drying to obtain square fragment aluminum-plastic film waste; (4) Pre-treated square fragment aluminum-plastic film waste is added to the dissociation solution and stirred and leached to cause interfacial dissociation between the plastic film and aluminum foil, resulting in a mixture of aluminum foil and plastic film; (5) After the aluminum foil and plastic film mixture is washed with water, the film and aluminum sheet that fall off on their own are separated by hydraulic flotation.

[0009] The citric acid aqueous solution in step (1) is a monohydrated citric acid aqueous solution.

[0010] In step (2), the size of the square fragment aluminum-plastic film waste is 2×2cm. 2 .

[0011] In step (3), the dissociation liquid is sprayed once every 2-3 hours, and the ratio of the mass of the square fragment aluminum-plastic film waste to the volume of the dissociation liquid is 1-2:1 g / mL. The dissociation liquid is sprayed 3-4 times in total.

[0012] In step (4), the liquid-to-solid ratio of the pretreated square fragment aluminum-plastic film waste to the dissociation liquid is 35~45:1L / kg.

[0013] The leaching temperature in step (4) is 40~50℃, and the leaching time is 1~3h.

[0014] The stirring speed in step (4) is 50~250 r / min.

[0015] The leaching in step (4) is ultrasonic leaching, with an ultrasonic power of 100-800W and a frequency of 10-30kHz.

[0016] The film that detaches autonomously in step (5) is cleaned and dried, and then granulated to prepare recycled plastic granules for use in the production of low-end plastic products, thereby achieving high-value utilization of all components.

[0017] In step (5), the aluminum foil can be smelted and then made into aluminum ingots.

[0018] The beneficial effects of this invention are: 1. Novel formulation and strong innovation: This invention is the first to use fatty alcohol polyoxyethylene ether (AEO-9) and citric acid in the field of aluminum-plastic film separation. Only a low concentration of citric acid aqueous solution and a small amount of fatty alcohol polyoxyethylene ether (AEO-9) are needed to achieve green and efficient separation of waste aluminum-plastic film. It overcomes the technical bias of requiring high concentration of citric acid for separation in the prior art. This invention will not cause corrosion to the equipment, and the surface of the plastic film after peeling is basically free of acidic substances.

[0019] 2. Low energy consumption: This method abandons the traditional high-temperature pyrolysis process (which requires maintaining a high temperature of 400~600℃ and introducing inert gases such as nitrogen to prevent oxidation). It can achieve efficient dissociation under low temperature conditions (40℃~50℃), reducing the reaction temperature by about 350~560℃, which greatly reduces energy consumption.

[0020] 3. Green and environmentally friendly: Citric acid and AEO-9 are selected as composite dissociation reagents. The reagents themselves are non-toxic, harmless and environmentally friendly. The non-pyrolytic interface dissociation technology separates the plastics in solid form, eliminating the generation of heavy tar and the emission of highly toxic and harmful gases such as HCN and benzene compounds from the source, and eliminating the pressure of exhaust gas treatment.

[0021] 4. Low cost: The low-temperature reaction saves a lot of heating energy. The citric acid (industrial grade, about 4,000-5,000 yuan / ton) and AEO-9 (about 12,000-15,000 yuan / ton, with very small usage, only 0.5-2.0g / L) used are both cheap and readily available bulk chemical raw materials. The dissociation filtrate can be recycled after replenishing the reagents, and at the same time, the complex and expensive tail gas purification system is eliminated, which significantly reduces the overall equipment investment and operating costs.

[0022] 5. High recovery rate: The mild conditions throughout the process prevent deformation or oxidation of the aluminum foil. Interfacial synergy allows each layer to detach autonomously, avoiding damage caused by mechanical stripping and preserving the original metallic morphology. This ensures the aluminum foil maintains a good planar shape, facilitating subsequent flotation separation, resulting in an extremely high aluminum recovery rate (>99.5%). The separation process is enhanced by ultrasound, achieving even better dissociation effects and efficiency.

[0023] 6. High added value of products: The obtained plastic can be sold after granulation, and the obtained aluminum foil can be sold after melting to produce aluminum ingots. Attached Figure Description

[0024] Figure 1 This is a photograph of the waste aluminum-plastic film before processing in Embodiment 1 of the present invention; Figure 2 This is a diagram of the aluminum foil and plastic film mixture after processing in Example 1 of the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] This green and efficient method for separating waste aluminum-plastic film includes the following steps: (1) Preparation of dissociation solution: First, prepare an aqueous solution of citric acid with a concentration of 0.02~0.05 mol / L. In specific embodiments, the concentration can be 0.02, 0.03, 0.04 or 0.05 mol / L. Then add 0.5~2.0 g / L of fatty alcohol polyoxyethylene ether. In specific embodiments, the concentration can be 0.5, 1.0, 1.5 or 2.0 g / L. Mix evenly to obtain the dissociation solution. (2) The aluminum-plastic film waste is crushed to obtain square fragments of aluminum-plastic film waste; (3) Spray dissociation liquid into the square fragment aluminum-plastic film waste, wet the square fragment aluminum-plastic film waste, and pre-treat it after air drying to obtain square fragment aluminum-plastic film waste; (4) Pre-treated square fragment aluminum-plastic film waste is added to the dissociation solution and stirred and leached to cause interfacial dissociation between the plastic film and aluminum foil, resulting in a mixture of aluminum foil and plastic film; (5) After the aluminum foil and plastic film mixture is washed with water, the film and aluminum sheet that fall off on their own are separated by hydraulic flotation.

[0027] The citric acid aqueous solution in step (1) is a monohydrated citric acid aqueous solution.

[0028] In step (2), the size of the square fragment aluminum-plastic film waste is 2×2cm. 2 .

[0029] In step (3), the dissociation liquid is sprayed once every 2-3 hours. In specific embodiments, it can be 2, 2.5 or 3 hours. The spraying is carried out according to the ratio of the mass of square fragment aluminum-plastic film waste to the volume of dissociation liquid of 1:1 g / mL, and a total of 3-4 sprayings are performed.

[0030] In step (4), the liquid-to-solid ratio of the pretreated square fragment aluminum-plastic film waste to the dissociation liquid is 35~45:1 L / kg. In specific embodiments, it can be 35:1, 38:1, 40:1, 42:1 or 45:1 L / kg.

[0031] The leaching temperature in step (4) is 40~50℃, which can be 40, 42, 45, 48 or 50℃ in specific embodiments; the leaching time is 1~3h, which can be 1, 1.5, 2, 2.5 or 3h in specific embodiments.

[0032] The stirring speed in step (4) is 50~250 r / min, and in specific embodiments it can be 250, 300 or 350 r / min to ensure uniform mass transfer. Step (4) requires careful control of the stirring rate. Too strong a stirring rate may cause the aluminum foil to wrinkle, which is not conducive to separation from the plastic.

[0033] The leaching in step (4) is ultrasonic leaching, with an ultrasonic power of 100-800W. In specific embodiments, the ultrasonic power can be 100, 200, 300, 400, 500, or 800W; the frequency is 10-30kHz. In specific embodiments, it can be 10kHz, 20kHz, or 30kHz.

[0034] Example 1 Taking the aluminum-plastic film treatment provided by a new energy battery factory in Shenzhen (with an aluminum content of 60.92% as determined by experiments) as an example: This green and efficient method for separating waste aluminum-plastic film includes the following steps: (1) Preparation of dissociation solution: First, prepare a 0.03 mol / L citric acid aqueous solution, then add 1.0 g / L fatty alcohol polyoxyethylene ether and mix well to obtain the dissociation solution; (2) Crush 2.5 kg of aluminum-plastic film waste to obtain 2×2 cm 2 Square-shaped scrap aluminum-plastic film, such as Figure 1 As shown; (3) Spray the dissociation liquid into the square fragment aluminum-plastic film waste to wet the square fragment aluminum-plastic film waste. Spray the dissociation liquid once every 2 hours. Spray the liquid at a ratio of 2:1 g / mL based on the mass of the square fragment aluminum-plastic film waste. Spray the liquid three times in total. After air drying, the square fragment aluminum-plastic film waste is obtained through pretreatment. (4) Pre-treated square fragment aluminum-plastic film waste was added to the dissociation solution and stirred for leaching. The liquid-to-solid ratio of the pre-treated square fragment aluminum-plastic film waste to the dissociation solution was 40:1 L / kg, the leaching temperature was 45℃, the leaching time was 2h, the stirring speed was 200r / min, the ultrasonic power was 600W, and the frequency was 30kHz, so that the plastic film and aluminum foil would undergo interfacial dissociation to obtain a mixture of aluminum foil and plastic film, such as Figure 2 As shown; (5) After the aluminum foil and plastic film mixture is washed with water, the film and aluminum sheet that fall off on their own are separated by hydraulic flotation.

[0035] The aluminum recovery rate was measured to be 99.62%. The recovered aluminum sheets had a silvery-white metallic luster and could be directly smelted into aluminum ingots for high-value utilization without secondary polishing.

[0036] This embodiment demonstrates good separation performance of waste aluminum-plastic film, as shown in the actual separation effect diagram. Figure 2 As shown, over 90% of the waste aluminum-plastic film separated from the aluminum foil.

[0037] Comparative Example 1 Compared with Example 1, this comparative example only differs in that in step (1), only a 0.03 mol / L citric acid aqueous solution is prepared, but no fatty alcohol polyoxyethylene ether is added. The remaining steps (2) to (4) are completely consistent with Example 1. It was found that when the dissociation solution in this comparative example is used for separation, only 60% of the waste aluminum-plastic film separated from the aluminum foil.

[0038] Comparative Example 2 Compared with Example 1, this comparative example only differs in that in step (1), only a 5 mol / L citric acid aqueous solution is prepared, but no fatty alcohol polyoxyethylene ether is added. The remaining steps (2) to (4) are completely consistent with Example 1. It was found that when the dissociation solution in this comparative example is used for separation, only 68% of the waste aluminum-plastic film separated from the aluminum foil.

[0039] Comparative Example 3 Compared with Example 1, the only difference in this comparative example is that in step (1), only a 5 mol / L citric acid aqueous solution is prepared, and then 1.0 g / L fatty alcohol polyoxyethylene ether is added. The remaining steps (2) to (4) are completely consistent with Example 1. It was found that when the dissociation solution in this comparative example is used for separation, only 75% of the waste plastic film separated from the aluminum foil.

[0040] Comparative Example 4 Compared with Example 1, this comparative example is the same as the steps (1), (2) and (4) in Example 1, except that the processing step (3) is not performed. It was found that when the dissociation liquid in this comparative example was used for separation, only 63% of the waste plastic film separated from the aluminum foil.

[0041] As can be seen from Example 1, the present invention achieves green and efficient separation of waste aluminum-plastic film by using a dissociation solution formed by a suitable 0.03mol / L citric acid aqueous solution and 1.0g / L fatty alcohol polyoxyethylene ether, followed by 3-4 wetting cycles and stirring leaching.

[0042] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A green and efficient method for separating waste aluminum-plastic film, characterized in that... Includes the following steps: (1) Preparation of dissociation solution: First, prepare a citric acid aqueous solution with a concentration of 0.02~0.05mol / L, then add 0.5~2.0g / L fatty alcohol polyoxyethylene ether, and mix evenly to obtain the dissociation solution; (2) The aluminum-plastic film waste is crushed to obtain square fragments of aluminum-plastic film waste; (3) Spray dissociation liquid into the square fragment aluminum-plastic film waste, wet the square fragment aluminum-plastic film waste, and pre-treat it after air drying to obtain square fragment aluminum-plastic film waste; (4) Pre-treated square fragment aluminum-plastic film waste is added to the dissociation solution and stirred and leached to cause interfacial dissociation between the plastic film and aluminum foil, resulting in a mixture of aluminum foil and plastic film; (5) After the aluminum foil and plastic film mixture is washed with water, the film and aluminum sheet that fall off on their own are separated by hydraulic flotation.

2. The green and efficient waste aluminum-plastic film separation method according to claim 1, characterized in that: The citric acid aqueous solution in step (1) is a monohydrated citric acid aqueous solution.

3. The green and efficient waste aluminum-plastic film separation method according to claim 1, characterized in that: In step (2), the size of the square fragment aluminum-plastic film waste is 2×2cm. 2 .

4. The green and efficient waste aluminum-plastic film separation method according to claim 1, characterized in that: In step (3), the dissociation liquid is sprayed once every 2-3 hours, and the ratio of the mass of the square fragment aluminum-plastic film waste to the volume of the dissociation liquid is 1~2:1g / mL. The dissociation liquid is sprayed 3-4 times in total.

5. The green and efficient waste aluminum-plastic film separation method according to claim 1, characterized in that: In step (4), the liquid-to-solid ratio of the pretreated square fragment aluminum-plastic film waste to the dissociation liquid is 35~45:1L / kg.

6. The green and efficient waste aluminum-plastic film separation method according to claim 1, characterized in that: The leaching temperature in step (4) is 40~50℃, and the leaching time is 1~3h.

7. The green and efficient waste aluminum-plastic film separation method according to claim 1, characterized in that: The stirring speed in step (4) is 50~250 r / min.

8. The green and efficient waste aluminum-plastic film separation method according to claim 1, characterized in that: The leaching in step (4) is ultrasonic leaching, with an ultrasonic power of 100-800W and a frequency of 10-30kHz.

9. The green and efficient method for separating waste aluminum-plastic film according to claim 1, characterized in that: The film that detaches autonomously in step (5) is cleaned and dried, and then granulated to prepare recycled plastic granules for use in the production of low-end plastic products, thereby achieving high-value utilization of all components.

10. The green and efficient waste aluminum-plastic film separation method according to claim 1, characterized in that: In step (5), the aluminum foil can be smelted and then made into aluminum ingots.

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