* Corresponding author: Renato Ribeiro Siman email: renato.siman@ufes.br Detritus / Volume 10 - 2020 / pages 62-74 https://doi.org/10.31025/2611-4135/2020.13939 © 2019 Cisa Publisher. Open access article under CC BY-NC-ND license SILVER RECOVERY FROM END-OF-LIFE PHOTOVOLTAIC PANELS Larisse Suzy Silva de Oliveira 1 , Maria Tereza Weitzel Dias Carneiro Lima 2 , Luciana Harue Yamane 1 and Renato Ribeiro Siman 1, * 1 Department of Environmental Engineering, Federal University of Espírito Santo, Fernando Ferrari Avenue 514, Goiabeiras, Vitória, 29075-910, Brazil 2 Department of Chemistry, Federal University of Espírito Santo, Fernando Ferrari Avenue 514, Goiabeiras, Vitória, 29075-910, Brazil Article Info: Received: 11 November 2019 Revised: 17 February 2020 Accepted: 24 February 2020 Available online: 31 March 2020 Keywords: Photovoltaic panel Silver recovery Hydrometallurgical E-waste Recycling ABSTRACT The growth of the photovoltaic sector has stood out among renewable sources of energy, due to technological innovations that have brought about cost reductions. Thus, this paper aimed to analyze the technical feasibility of silver recovery from photovoltaic cells using acid leaching, followed by an evaluation of the chemical and electrochemical precipitation processes to analyze their effciencies. As a primary objective of this work, the gravimetric composition and the metal concentration (Ag, Al, Pb, Cu, and Fe) in the photovoltaic cells were frst determined, developing the ba- sis for future research on photovoltaic panels recycling Subsequently, the infuence of HNO 3 concentration (1-10 mol/L), temperature (25-60°C), and reaction time were evaluated. A new research application used a statistical tool, the Central Composite Rotational Design (CCRD), as well as samples of different brands and models of photovoltaic panels, in order to ensure the experimental validity. As a highlight, the analysis of the composition of the photovoltaic cells, applying the HNO 3 leaching, showed that up to 6.87 kg of silver can be recovered per ton of photovoltaic cells. It was possible to solubilize 100% of the silver contained in the photovoltaic cells using the optimal parameters. Silver precipitation by addition of HCl and Na 2 CO 3 , as well as electroprecipitation, made it possible to extract more than 99% of silver in solution, being a primary novelty of this study. Therefore, the studied pathway allowed for the recovery of 99.98% of the silver present in the photovoltaic cells. 1. INTRODUCTION The development of alternative energy sources has been explored in order to increase energy supply and to replace or reduce the exploitation of non-renewable sourc- es. Among the renewable sources of energy, solar energy from photovoltaic panels is one of the most used and ef- fcient methods (Europe, 2018). It is estimated that an in- stalled power of 26.7MW allows for saving about 560,700 t of Carbon dioxide equivalent (tCO 2 eq) during the lifetime of the photovoltaic system, as an alternate to fossil fuels. If the photovoltaic panels were recycled instead of being landflled, it can additionally save about 1600-2400 tCO 2 eq. (D’Adamo et al., 2017). Rapid development of the photovoltaic industry has presented a global challenge with respect to the recycling of valuable components from end-of-life photovoltaic pan- els, due to the approximate 30 year lifespan of these panels (Song et al., 2020). It is estimated that by the year 2050, 78 million tons of photovoltaic panels will need to be disposed of around the world, but information about their destinations (recy- cling) and fnal disposal are still scarce (Weckend, Wade, & Heath, 2016). According to Domínguez & Geyer (2019), there will be 800 thousand metric tons (Mt) of end-of-life photovoltaic panels in need of disposal between 2030 and 2060 in the United States alone. Table 1 shows some esti- matives of photovoltaic panels waste. Due to this potential generation of end-of-life photovol- taic panels in the coming years, some studies evaluating different recycling processes and routes have been con- ducted. They have especially focused on crystalline sili- con panels, representing 85-90% of the market due to low prices and mature manufacturing technology (Song et al., 2020). Silicon photovoltaic panels are composed of an alumi- num frame, tempered glass, a silicon photovoltaic cell with metal flaments that are wrapped in two layers of encap- sulating material, and a backsheet (Tammaro et al., 2016). The main metals present in photovoltaic panels are lead, copper, alluminum, and silver (Dias et al., 2016).The com- position of a silicon photovoltaic panel (a) and its cell (b) is shown in Figure 1.