Characterization of shredded fractions from end of life photovoltaic panels to optimize glass and metal recovery

To date, the recycling of end-of-life photovoltaic panels (PVs) is a topic of great interest due to the increasing use of this technology and the disposal of PVs is expected to become a relevant environmental issue in the coming decades. This requires proper management of the PVs in order to maximize the recovery of raw materials such as glass, aluminium, copper, silicon, stannous and silver. The European Union considers some of these materials as Critical Raw Materials (CRM), given their high economic importance. PVs are mainly composed of high quality tempered glass and aluminium, while the most precious components are metals (Cu, Sn, Ag) which represent the lowest weight fraction[1]. In 2018, about 1,000 tons of photovoltaic panels were recycled in Italy and it is estimated that over 2 million tons will be reached by 2050. In this work, the optimization of a mechanical treatment process is reported starting from the characterization of the shredded fractions obtained from the treatment plant (mainly dismantling, shredding and sieving) operating at the Nike s.r.l. company. In particular, the particle size analysis was started by sieving sample fractions having diameters lower than 10 mm, 10-30 mm and >50 mm, respectively. The first part of the characterization concerned the particle size fraction <10mm which was further sieved to obtain 4 new fractions (Ø> 5.6 mm; Ø> 2 mm; Ø> 1 mm and Ø <1mm), subsequently analysed. After a manual separation, 11 different types of fractions were obtained and analysed (pure glass, polymer materials, silica, metallic items, etc) to identify the fraction containing the most glass, polymers and metals. Leaching of the fractions with toluene at different temperature (50-90°C) and treatment time (30-400 minutes) was performed to determine the distribution of polymer materials within the fractions while the metals were leached by using HNO3 (7M) solutions. The metal analysis was carried out by ICP [3]. Preliminary data showed that the polymer materials (EVA, PET and Tedlar) represent 15% of the largest fraction (Ø >5.6 mm) while the metals are much more present in the smallest one (Ø <1 mm). These results demonstrate that it is already possible to modify the industrial mechanical process to obtain a high quality glass and the recovery of Ag, Cu and Sn metal ions by selective separation [4]. Project PON research and innovation: Raw material recovery from photovoltaic panels at the end of life and environmental economic evaluation [1] B. Seo, J. Y. Kim, and J. Chung, Waste Management, ‘Overview of global status and challenges for end-of-life crystalline silicon photovoltaic panels: A focus on environmental impacts’, vol. 128, pp. 45–54, Jun. 2021, doi: 10.1016/j.wasman.2021.04.045. [3] F. Pagnanelli et al., Journal Environmental Management, ‘Solvent versus thermal treatment for glass recovery from end of life photovoltaic panels: Environmental and economic assessment’, vol. 248, p. 1-13, Oct. 2019, doi: 10.1016/j.jenvman.2019.109313. [4] L.Pietrelli, M. Pietrantonio, A. Ruberti, A. Modica. Il recupero di materie prime da pannelli fotovoltaici Proc. of Ecomondo Conf., Rimini 2014