https://orcid.org/0000-0003-2278-3395
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ABSTRACT
Thermal treatment is a mainstream technique to separate plastic components from waste crystalline silicon (c-Si) photovoltaic (PV) modules. In this study, the thermogravimetric analysis (TGA) was conducted for a better understanding of the characteristics of plastic components mainly poly(ethylene-co-vinyl) acetate (EVA) binder and polyfluoroethylene composite membrane (TPT) backsheet in waste c-Si PV panels through thermal treatment at four different heating rates (5–20°C·min−1) under nitrogen and air conditions, respectively. The thermal process of the EVA binder whether in a nitrogen or air atmosphere could be divided into two phases, which were 300–400°C and 400–515°C in nitrogen with the total weight loss reached 99.64%; the two phases in the air were 270–405°C and 405–570°C with the total weight loss was 99.68%. The thermal weight loss of TPT in nitrogen has only one phase occured between 380°C and 520°C, and the weight loss rate is about 83%. There are two weight loss phases in the air atmosphere, which the first phase starts from 265°C to 485°C and the second phase ends at 635°C with a final weight loss reaching 97%. Furthermore, the Kissinger–Akahira–Sunose (KAS) method was chosen to calculate the pyrolysis kinetic parameters. The activation energy for EVA in nitrogen (261.16 kJ·mol−1) was higher than in air (209.04 kJ·mol−1), also the TPT in nitrogen (188.28 kJ·mol−1) higher than in air (172.21 kJ·mol−1). That indicated that the thermal decomposition of EVA binder was accelerated at first phase in nitrogen, but there is little difference in air atmosphere. Moreover, the activation energy of PVF of the TPT backsheet in the first phase was lower than that in the second phase. This study provides the fundamental basis to develop efficient thermal separation for the plastic components EVA and TPT in waste PV panels.
Implications: This study mainly aims to explore the thermal separation of plastic components of waste c-Si panels for heating treatment, so that developing an accurate heat treatment approach that is efficient to implement for the separation of secondary raw material i.e., glass and silicon wafer from end-of-life PV panels. Therefore, this research findings have significant implications for providing the basic data support for waste PV panels management recycling standards, specifications, or policy documents
Nomenclature
| A | = | Pre-exponential factor, 1/min |
| a | = | Compensation parameter, mol · kJ−1 |
| E | = | Activation energy, kJ·mol−1 |
| f(α) | = | Conversion function model, dimensionless |
| k | = | Specific rate constant, 1/s |
| n | = | Reaction order, dimensionless |
| R | = | Universal gas constant, = 8.314 J·(mol−1·K−1) |
| R2 | = | Coefficient of determination, dimensionless |
| T | = | Temperature, °C |
| t | = | Time, s |
Greek letters
| α | = | Degree of conversion, dimensionless |
| β | = | Heating rate, K/min or K/s |
Acknowledgment
The authors are grateful for the financial support from Shanghai Shuguang Program (21SG55), Local capacity construction (22010500800), and Pudong Minsheng Program (PKJ2022-C02). Special thanks to Difei Yang to participate in the experimental data compilation. The authors sincerely acknowledge Dr John C. Crittenden and Dr Chao He for the constructive comments and editing for improving the quality of this manuscript.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The authors confirm that the data supporting the findings of this study are available within the article or its supplementary materials.
Additional information
Funding
Notes on contributors
Qing Huang
Qing Huang, currently a PhD candidate in Shanghai Normal University, works at Shanghai Polytechnic University as a engineer who engaged in e-waste recycling and waste management.
Wenyi Yuan
Wenyi Yuan, Professor, graduated with a PhD in Environmental Engineering from Tsinghua University in 2012. Since Sept. 2013, he has been working in teaching and research at Shanghai Polytechnic University, focusing on the recycling of e-waste and soil pollution remediation technology.
Yaping Guo
Yaping Guo, Professor/Doctoral Supervisor, and Director of the Special Ceramics Branch of the Chinese Silicate Society.
Qinfei Ke
Qinfei Ke, PhD in Engineering, National Second Class Professor, Doctoral Supervisor. She received a PhD in Engineering from Donghua University in March 2000. From January 1986 to November 2011, she worked at Donghua University and served as a lecturer, associate professor, professor, and doctoral supervisor.