Method for removing ethylene-vinyl acetate copolymer by active oxygen in combination with ultrasonic

Abstract

The present application belongs to the technical field of solid waste resource recycling, and particularly relates to a method for jointly using active oxygen and ultrasonic waves to remove ethylene-vinyl acetate copolymer. The method uses the joint action of active oxygen and ultrasonic waves to achieve the effect of removing ethylene-vinyl acetate copolymer (EVA). The ultrasonic waves can accelerate the diffusion speed of active oxygen in the solution, so that the active oxygen can find the EVA molecules more quickly, destroy the molecular structures such as -CH2- and -CO-CH2- in the EVA molecules, and further destroy the crosslinking network structure of the EVA, so that the EVA loses its own characteristics and achieves the effect of removing the encapsulation. Moreover, through the method, the content of VA in the EVA molecules is reduced, the material can be regenerated through hot melting and reworking, and the subsequent recycling process is facilitated. The technical scheme of the present application significantly improves the processing efficiency, can realize efficient unsealing and recycling of the sample EVA, the whole process is green and efficient, no secondary pollution is generated, and the economic benefit is significant.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource recycling technology. More specifically, it relates to a method for the combined use of active oxygen and ultrasound to decompose ethylene-vinyl acetate copolymers. Background Technology

[0002] Solar cells generate electricity on a simple principle, producing no mechanical movement, consuming no fuel, and emitting no substances, including greenhouse gases, during the process. They are also noiseless and pollution-free. Compared to traditional energy sources, solar energy can be considered the cleanest and most sustainable energy type. Therefore, solar cells have been widely promoted and used since their inception.

[0003] Since 2000, the installation of solar cells worldwide has increased dramatically. In 2000, the cumulative installed photovoltaic (PV) capacity was only 1.28 GW; by 2020, it had reached 709.67 GW, and is projected to reach 4500 GW by 2050. However, solar cells have a limited lifespan of 25-30 years. Solar cells installed in the early 21st century will soon be obsolete, and it is estimated that by 2050, 60-78 million tons of waste solar cells will be generated. This massive amount of waste solar cells, if not properly managed, will pose a significant threat to the environment. Therefore, the rational and efficient disposal of waste solar cells is urgently needed.

[0004] To effectively and rationally utilize waste solar cell resources, the first step is to decapsulate and separate the solar cells. Currently, solar cell module separation methods can be categorized into physical layering, chemical reagent treatment, and a combination of physical and chemical methods. Physical layering includes manual disassembly, crushing, and heat treatment. Disassembly and crushing can achieve coarse separation of components, obtaining small particles through a simple process; however, most solar cells use ethylene-vinyl acetate copolymer (EVA) as an encapsulant, and simple physical disassembly cannot remove EVA molecules, which will still adhere to the various modules. Heat treatment can decompose the organic components in photovoltaic modules at high temperatures, but EVA molecules are completely destroyed at high temperatures and cannot be reused. Furthermore, heat treatment involves high energy consumption and the generation of toxic waste gases. Regarding chemical reagent treatment, a series of chemical reagents are generally used to dissolve or expand EVA. For example, Chinese patent application CN106883939A discloses a chemical decomposition and removal agent for EVA resin dirt, which uses a large amount of chemical substances to react and remove EVA. However, this method requires a significant amount of time and chemical substances, and also generates a large amount of organic wastewater. Moreover, the organic solvents easily evaporate, forming toxic organic vapors, making the emission of harmful gases difficult to avoid.

[0005] It is evident that there is still a lack of effective methods for recycling and processing waste solar cells. There is an urgent need to provide a green, safe, efficient method that eliminates the risk of secondary pollution and can quickly and effectively unpack waste solar cells. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defects and shortcomings of existing physical EVA removal methods, which leave residues, heat treatment methods which destroy EVA and consume a lot of energy, and chemical reagent removal methods which are time-consuming and produce a lot of waste. This invention provides a green, safe, efficient method that has no risk of secondary pollution and can quickly and efficiently unpack ethylene-vinyl acetate copolymer.

[0007] Therefore, the object of the present invention is to provide a method for the release of ethylene-vinyl acetate copolymer by a combination of reactive oxygen species (ROS) and ultrasound.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] A method for the combined use of reactive oxygen species and ultrasound to degrade ethylene-vinyl acetate copolymer (EVA) specifically includes the following steps:

[0010] The sample to be treated is placed in an unsealing solution, and the ethylene-vinyl acetate copolymer in the sample is released by the combined action of active oxygen and ultrasound.

[0011] In this invention, ROS combined with ultrasonic treatment is used. ROS molecules are highly reactive and can quickly find and "attack" targets in solution, releasing their own energy. The addition of ultrasonic technology in the solution accelerates the diffusion rate of ROS, enabling it to find EVA molecules more quickly, destroying the molecular structures such as -CH2- and -CO-CH2-, and disrupting the cross-linked network structure of EVA, causing it to lose its inherent properties, ultimately achieving the effect of unpacking the sample. Furthermore, after treatment by this method, the VA content in the EVA molecules is reduced, allowing for material regeneration and recycling through thermal remelting.

[0012] Further, the total amount of active oxygen generated to the mass ratio of the sample to be treated is (50-60):1. Preferably, the total amount of active oxygen generated to the mass ratio of the sample to be treated is 50:1. In practice, it has been found that under this condition, the time to completely deseal the ethylene-vinyl acetate copolymer is shorter and the efficiency is higher.

[0013] Furthermore, the mass ratio of the desealing solution to the hourly active oxygen generation is (20-25):1. Preferably, the mass ratio of the desealing solution to the hourly active oxygen generation is 20:1. In practice, it has been found that under this condition, the time to completely deseale the ethylene-vinyl acetate copolymer is shorter and the efficiency is higher.

[0014] Further, the unsealing solution is water. Preferably, the water is tap water, industrial water, or purified water. More preferably, the unsealing solution is purified water; in practice, it has been found that the unsealing effect of ethylene-vinyl acetate copolymer is better when purified water is used as the unsealing solution.

[0015] Furthermore, the mass ratio of the unsealing solution to the sample to be treated is (100-150):1. Preferably, the mass ratio of the unsealing solution to the sample to be treated is 150:1; more preferably, the unsealing solution needs to be added appropriately as its mass decreases due to evaporation and other reasons during the unsealing process.

[0016] Furthermore, the frequency of the ultrasound is (20-40) kHz. Preferably, the frequency of the ultrasound is 40 kHz; in practice, it has been found that under this condition, the ethylene-vinyl acetate copolymer achieves better and more efficient complete unsealing.

[0017] Furthermore, the power of the ultrasound is (150-250) W. Preferably, the power of the ultrasound is 200 W; in practice, it has been found that under this condition, the ethylene-vinyl acetate copolymer achieves better and more efficient complete desealing.

[0018] Furthermore, the duration of the combined action is (6-7) hours. Preferably, the duration of the combined action is 6 hours; more preferably, the duration of the combined action is 7 hours.

[0019] Preferably, the release process is carried out in a semi-open liquid container.

[0020] Furthermore, the sample to be processed is a solar cell.

[0021] Furthermore, the solar cell is a crystalline silicon solar cell, a copper indium gallium selenide (CIGS) solar cell, or a CdTe thin-film battery.

[0022] The present invention has the following beneficial effects:

[0023] This invention provides a method for decapsulating ethylene-vinyl acetate copolymer (EVA) using a combination of reactive oxygen species and ultrasound. Ultrasound accelerates the diffusion of reactive oxygen species in solution, allowing them to more quickly find EVA molecules and disrupt their molecular structures, such as -CH2- and -CO-CH2-, thereby destroying the EVA cross-linked network structure and rendering it ineffective, thus decapsulating it. Furthermore, this method reduces the VA content in the EVA molecules, enabling material regeneration through thermal remelting, facilitating subsequent recycling processes. This invention significantly improves processing efficiency, enabling efficient decapsulation and recovery of EVA samples. The entire process is green, efficient, and produces no secondary pollution, resulting in significant economic benefits. Attached Figure Description

[0024] Figure 1 This is a comparison image of the waste CIGS solar cell before and after unsealing in Example 1.

[0025] Figure 2 The images shown are electron microscope images of the unsealed waste CIGS solar cells in Example 1, where (a) is an overall morphology image (20 μm) and (b) is a detailed image (5 μm).

[0026] Figure 3 This is a partial unsealing diagram of the CIGS solar cell in Comparative Example 1.

[0027] Figure 4 This is a diagram showing only the edge of the CIGS solar cell in Comparative Example 3.

[0028] Figure 5 This is a diagram of the unsealed waste crystalline silicon solar cell in Comparative Example 4. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0030] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0031] Example 1: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using a combination of reactive oxygen species (ROS) and ultrasound.

[0032] The method specifically includes the following steps:

[0033] A semi-open container was placed in an ultrasonic generator. Desealing solution (pure water) and waste CIGS were added to the semi-open liquid container at a mass ratio of 150:1. The ROS generator was completely immersed in the desealing solution. The mass ratio of total ROS production to treated waste CIGS was set to 50:1. The hourly ROS production was calculated as the ratio of total ROS production to reaction time. The ultrasonic generator frequency was set to 40kHz and the power to 200W. After 6 hours of continuous reaction, the CIGS was completely desealed. See [link to before-and-after comparison]. Figure 1 See electron microscope image of CIGS after unsealing. Figure 2 .

[0034] Example 2: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using a combination of reactive oxygen species (ROS) and ultrasound.

[0035] The method specifically includes the following steps:

[0036] A semi-open container was placed in an ultrasonic generator. A desealing solution (pure water) and waste crystalline silicon solar cells were added to the semi-open liquid container at a mass ratio of 150:1. The ROS generator was completely immersed in the desealing solution. The mass ratio of total ROS production to the waste crystalline silicon solar cells was set to 50:1. The hourly ROS production was calculated as the ratio of total ROS production to reaction time. The ultrasonic generator frequency was set to 40kHz and the power to 200W. After 7 hours of continuous reaction, the crystalline silicon solar cells were completely desealed.

[0037] Example 3: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using a combination of reactive oxygen species (ROS) and ultrasound.

[0038] The method specifically includes the following steps:

[0039] A semi-open container was placed in an ultrasonic generator. A desealing solution (pure water) and waste CdTe thin-film solar cells were added to the semi-open liquid container at a mass ratio of 100:1. The ROS generator was completely immersed in the desealing solution, and the mass ratio of total ROS production to the waste CdTe thin-film solar cells was set to 50:1. The hourly ROS production was calculated as the ratio of total ROS production to reaction time. The ultrasonic generator frequency was set to 40kHz and the power to 200W. After 6 hours of continuous reaction, the CdTe thin-film solar cells were completely desealed.

[0040] Comparative Example 1: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using reactive oxygen species (ROS).

[0041] The method specifically includes the following steps:

[0042] Add desealing solution (pure water) and waste CIGS to a semi-open liquid container at a mass ratio of 150:1; completely immerse the ROS generator in the desealing solution, set the mass ratio of total ROS production to waste CIGS to be treated to 50:1, and calculate the hourly ROS production as the ratio of total ROS production to reaction time; after 8 hours of continuous reaction, the CIGS is partially desealed.

[0043] Compared to Example 1, this comparative example did not include ultrasound. As a result, even after 8 hours of reaction, CIGS only achieved partial deblocking. See details below. Figure 3 .

[0044] Comparative Example 2: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using reactive oxygen species (ROS).

[0045] The method specifically includes the following steps:

[0046] A desealing solution (pure water) and waste crystalline silicon solar cells were added to a semi-open liquid container at a mass ratio of 150:1. The ROS generator was completely immersed in the desealing solution, and the mass ratio of total ROS production to the waste crystalline silicon solar cells was set to 50:1. The hourly ROS production was calculated as the ratio of total ROS production to reaction time. After 9 hours of continuous reaction, the crystalline silicon solar cells were not desealed.

[0047] Compared to Example 2, this comparative example did not involve combined ultrasound, and as a result, the crystalline silicon solar cell was not unsealed even after the reaction had been carried out for 9 hours.

[0048] Comparative Example 3: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using a combination of reactive oxygen species (ROS) and ultrasound.

[0049] The method specifically includes the following steps:

[0050] A semi-open container was placed in an ultrasonic generator. Desealing solution (pure water) and waste CIGS were added to the semi-open liquid container at a mass ratio of 150:1. The ultrasonic generator was set to a frequency of 40kHz and a power of 200W. After 8 hours of continuous reaction, only the outer edge of the CIGS was desealed. (See details...) Figure 4 .

[0051] Compared to Example 1, this comparative example did not involve the incorporation of reactive oxygen species. As a result, even after 8 hours of ultrasonic reaction, CIGS only achieved partial deblocking. See details below. Figure 4 .

[0052] Comparative Example 4: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using a combination of reactive oxygen species (ROS) and ultrasound.

[0053] The method specifically includes the following steps:

[0054] A semi-open container was placed in an ultrasonic generator. A desealing solution (pure water) and waste crystalline silicon solar cells were added to the semi-open liquid container at a mass ratio of 150:1. The ultrasonic generator was set to a frequency of 40kHz and a power of 200W. After 9 hours of continuous reaction, the crystalline silicon solar cells remained unsealed. (See details...) Figure 5 .

[0055] Compared to Example 2, this comparative example did not contain any reactive oxygen species, and as a result, the crystalline silicon solar cell was not desealed even after 9 hours of sonication.

[0056] Comparative Example 5: A method for ultrasonically removing ethylene-vinyl acetate copolymer (EVA)

[0057] The method specifically includes the following steps:

[0058] A semi-open container was placed in an ultrasonic generator. Desealing solution (pure water) and waste CIGS were added to the semi-open liquid container at a mass ratio of 150:1. The ultrasonic generator was set to a frequency of 40kHz and a power of 200W. After 6 hours of continuous reaction, the CIGS was not desealed.

[0059] Comparative Example 6: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using reactive oxygen species (ROS).

[0060] The method specifically includes the following steps:

[0061] A desealing solution (pure water) and waste CdTe thin-film solar cells were added to a semi-open liquid container at a mass ratio of 150:1. The ROS generator was completely immersed in the desealing solution, and the mass ratio of total ROS production to the waste CdTe thin-film solar cells was set to 50:1. The hourly ROS production was calculated as the ratio of total ROS production to reaction time. After 8 hours of continuous reaction, the CdTe thin-film solar cells were partially desealed.

[0062] Compared to Example 3, this comparative example did not involve combined ultrasound, and as a result, even after the reaction lasted for 8 hours, the CdTe thin-film solar cell could only achieve partial unsealing.

[0063] Comparative Example 7: A method for removing ethylene-vinyl acetate copolymer (EVA) from solar cells using reactive oxygen species (ROS).

[0064] The method specifically includes the following steps:

[0065] A desealing solution (pure water) and waste CdTe thin-film solar cells were added to a semi-open liquid container at a mass ratio of 150:1. The ROS generator was completely immersed in the desealing solution, and the mass ratio of total ROS production to the waste CdTe thin-film solar cells was set to 50:1. The hourly ROS production was calculated as the ratio of total ROS production to reaction time. After 9 hours of continuous reaction, only the edges of the CdTe thin-film solar cells were desealed.

[0066] Compared to Example 3, this comparative example did not involve combined ultrasound, and as a result, even after 9 hours of reaction, the CdTe thin-film solar cell only showed minimal damage at the edges.

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for the combined use of reactive oxygen species and ultrasound to degrade ethylene-vinyl acetate copolymers, characterized in that, Specifically, the following steps are included: The sample to be treated was placed in the unsealing solution, and the ethylene-vinyl acetate copolymer in the sample was released by the combined action of active oxygen and ultrasound. The unsealing solution is water.

2. The method according to claim 1, characterized in that, The total amount of reactive oxygen species generated is in a mass ratio of (50~60):1 to the mass of the sample to be treated.

3. The method according to claim 1, characterized in that, The mass ratio of the unsealing solution to the hourly active oxygen generation is (20~25):

1.

4. The method according to claim 1, characterized in that, The mass ratio of the unsealing solution to the sample to be treated is (100~150):

1.

5. The method according to claim 1, characterized in that, The frequency of the ultrasound is (20~40) kHz.

6. The method according to claim 1, characterized in that, The power of the ultrasound is 150~250 W.

7. The method according to claim 1, characterized in that, The duration of the combined effect is (6~7) h.

8. The method according to claim 1, characterized in that, The sample to be processed is a solar cell.

9. The method according to claim 8, characterized in that, The solar cells are crystalline silicon solar cells, copper indium gallium selenide solar cells, and CdTe thin-film solar cells.

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