Green sonochemical recovery of technology-critical elements from the end-of-life photovoltaic module using aqueous organic-acid solutions

End-of-life photovoltaic (PV) modules represent an increasingly important secondary resource for valuable metals and technology-critical elements. However, the combined influence of pretreatment strategy and leaching chemistry on metal recovery under ultrasonic-assisted conditions remains poorly understood. This study systematically evaluates multiple pretreatment approaches and chemically distinct lixiviants to identify factors governing selective metal extraction from polycrystalline silicon PV waste. Samples were subjected to mechanical milling (T1), pyrolysis at 500 °C (T2), or acetone washing (T3), followed by sonication-assisted leaching in an ultrasonic bath (ambient temperature, 10–60 min, S/L = 1:20 g mL −1 ). Citric acid, oxalic acid, EDTA, and HNO 3 were investigated as lixiviants, and elemental concentrations were determined by microwave digestion and ICP-MS. The PV waste was dominated by Cu, Sn, Pb, Sb, Cr, Ag, and Ni, with lower concentrations of Co, Ga, Ge, In, Mo, and Te. The finest particle fraction (< 0.05 mm), representing only 13.4–14.4% of the total mass, contained the highest concentrations of most elements, indicating disproportionate recovery potential and environmental risk. Metal recovery strongly depended on both pretreatment and leaching chemistry. Pyrolysis with HNO 3 provided the highest recoveries of Ag, Cu, Ga, Pb, and Zn, while oxalic acid improved Sb extraction. Co, Cr, and Ge showed high recoveries through mechanical treatment with EDTA, HNO 3 , and citric acid, respectively. Acetone treatment effectively recovered In and Sn with oxalic acid and Te with citric acid. Kinetic analysis revealed three distinct leaching stages, with optimum extraction times of approximately 10, 30, and 60 min for different element groups, while shrinking-core models described only Ga and Ge dissolution. By directly comparing multiple pretreatment–leaching combinations within a unified sonochemical framework, this study provides new insights into the roles of material accessibility, oxidation, and complexation in controlling selective recovery from PV waste, supporting more efficient and environmentally sustainable recycling strategies. From Photovoltaic Waste to Critical Elements: A Green Sonochemical Approach