Green extraction of silver from end-of-life photovoltaic modules by ultrasound-enhanced FeCl3-ChCl leaching

End-of-life crystalline silicon photovoltaic (EOL c-Si PV) modules contain a small mass fraction of silver (Ag), but Ag contributes disproportionately to their recoverable value. Ag extraction often relies on strong-acid systems such as HNO 3 , which offer high leaching efficiency but cause equipment corrosion, Si substrate damage, acidic wastewater and environmental risks. Mild systems such as organic acids can reduce the environmental impact, but their Ag oxidation-dissolution rates and interfacial mass transfer are often insufficient. Herein, air-pyrolyzed EOL double-glass PV modules were used as the feedstock, and an aqueous FeCl 3 -choline chloride (FeCl 3 -ChCl) leaching system was developed for green and efficient Ag extraction with external-field intensification. Ag leaching was governed by Fe(III)-mediated oxidation and the ChCl-regulated coordination environment. Increasing the ChCl content first promoted and then suppressed Ag leaching, indicating that excess ChCl was not beneficial to continuous Ag extraction. Raman analysis explained this behavior by showing that high ChCl content favored chloride-rich Fe-Cl coordination structures, whereas enhanced ionic association and increased solution viscosity increased mass-transfer resistance at the Ag gridline/solution interface. External-field intensification was then introduced to accelerate Ag extraction Mechanical stirring achieved an Ag leaching efficiency of 97.6%, whereas ultrasonication enhanced interfacial mass transfer, shortened the leaching time, and achieved 94.3% Ag leaching efficiency at 40 °C within 10 min. Dissolved Ag was then recovered as Ag powder with a purity of 99.5% through AgCl sedimentation, ammoniacal complexation and ascorbic acid reduction. This work offers a practical route for green and intensified Ag extraction from EOL PV modules.