Sustainable Recovery of Copper and Silver from End-of-Life Photovoltaic Panels by Leaching with Aqueous Solutions of Quaternary Imidazolium Salts

The exponential increase in photovoltaic panel (PV) waste highlights the urgent need to develop efficient and sustainable recycling processes. It is estimated that by 2030, 8 million tons of PV modules will reach their end-of-life stage, posing a significant environmental challenge and requiring the development of green technologies for resource recovery. This study assessed the performance of imidazolium-based ionic liquids (ILs) as “designer solvents” for the selective leaching of copper and silver from disused PV panels. Specifically, four quaternary imidazolium salts were evaluated: [Bmim]HSO4, [Emim]HSO4, [Bmim]Cl, and [Emim]Cl. Leaching tests were conducted on silicon wafers containing 0.28% Ag and 0.19% Cu under varying temperatures (25, 50, and 80 °C), IL concentrations (20% and 60% v/v), and hydrogen peroxide (H2O2) dosages (0% and 3% v/v) as an oxidizing agent. The results identified [Bmim]HSO4 as the most effective leaching agent. The system achieved a maximum copper extraction of 96.70% at 60% v/v concentration and 80 °C. For silver, the highest extraction of 45.13% was obtained using [Bmim]HSO4 at 20% v/v and 80 °C. The addition of H2O2 was crucial, demonstrating a clear synergistic effect with the imidazolium-based ILs by promoting oxidative dissolution. These findings confirm that imidazolium-based ionic liquids represent a promising and environmentally friendly alternative for the recovery of high-value metals in the circular economy of photovoltaic recycling.