Experimental study of recycling valuable materials from end-of-life PV panels: from thermal delamination to chemical leaching

Abstract

Photovoltaic (PV) solar cell is becoming indispensable in the clean energy supply chain. In the past decades, its repaid development and massive installation raise the concern that the massive amount of end-of-life PV panels will be produced and have to be properly treated in the foreseeable future. Therefore, there is an urgent requirement to develop a sustainable and efficient method to recycle end-of-life PV panels to ensure that both valuable and hazardous materials can be properly recovered and/or treated for safe disposal. However, the research and development of PV panel recycling is still at an early stage. In this study, a highly efficient recycling process is designed to investigate the key factors that affect the valuable components’ separation and recycling performance, which covers the thermal delamination, sieving separation, and chemical leaching process that reflect the key steps of the end-of-life PV module recycling process. In this thesis, a highly efficient physical separation method is first studied, which integrates the sieving process customised for PV recycling and a new technology of “sieving aids” (patent pending), achieving the effective separation of PV solar cells and glass fragments that are resulted from the thermal delamination. The results indicate that most of the chip-like PV cell particles (around 99%) can be separated from the debris mixture (glass and PV ribbon) with proper sieving conditions, which greatly contributes to the improvement of metal recovery performance in the chemical leaching process. Second, the chip-like PV cell particles collected by the separation process were further leached by nitric acid for silver extraction. In this part, to understand the mechanism underlying the influences of leaching parameters on the silver extraction performance, a number of experimental investigations were performed combined with a quantitative analysis using SEM-EDS, with a specific focus on the effect of solid/liquid ratio and acid concentration. The findings show that the leaching of the PV particles using nitric acid with higher concentrations generally yields a better silver extraction in a quantitative manner. The experimental results obtained in this thesis serve as a groundwork for future scaling up and optimization studies for the recycling of end-of-life photovoltaic modules.