A recyclable solvent for recovering silver in Polysilicon photovoltaics panels: BeCl-EG-CuCl2 solvents system

Abstract

A deep eutectic solvent (DES) was prepared using betaine hydrochloride (BeCl) and ethylene glycol (EG), enabling efficient leaching of silver (Ag) through the addition of cupper chloride (CuCl₂). The reaction process was environmentally friendly, avoiding the strong acids and alkalis typically required in traditional hydrometallurgical recycling. Under the optimized conditions (100°C, 45 min, solid-liquid ratio 1:500, 0.1 mol/L CuCl₂), Ag leaching efficiencies of 100 % (pure Ag) and 99.86 ± 0.12 % (PV panels) were achieved. Kinetic analysis indicated that the leaching process was governed by a chemical surface reaction model, with an apparent activation energy of 35.02 kJ·mol⁻¹. The reaction mechanism study showed that the polar environment provided by the DES, along with the strong oxidizing property of Cu²⁺, were crucial to the reaction success. Remarkably, the leaching efficiency of the DES remained high at 95.87 % even after 24 cycles of reuse. A life cycle assessment of the reaction process demonstrated that DES recycling is significantly more environmentally friendly compared to conventional hydrometallurgical recycling.