Mechanistic analysis of silver leaching from c-Si solar cells using an acetamide-based deep eutectic solvent

An efficient medium for silver (Ag) recovery from end-of-life crystalline silicon (c-Si) solar cells should combine strong Ag reactivity with limited co-extraction of non-target metals and good reusability. In this study, an acetamide-based deep eutectic solvent (DES) composed of choline chloride (ChCl) and acetamide (Ac) (ChCl:Ac = 1:2), with copper chloride (CuCl₂) as the oxidant, was developed as an Ag-leaching medium. Under identical 1 h conditions, ChCl:Ac-CuCl₂ produced an Ag-wire mass loss of 53.50 ± 4.55 mg, compared with 30.41 ± 4.29 mg for ChCl:Urea-CuCl₂, demonstrating stronger Ag-leaching performance. Using Ag wire as a model linear substrate, kinetic analysis showed that the conversion data were better described by the reaction-controlled cylindrical shrinking-core model than by the product-layer diffusion-controlled model. Within 50–80 °C, the apparent activation energy derived from the reaction-controlled model was 55.40 kJ·mol⁻¹. The apparent reaction order with respect to CuCl₂ decreased from 1.42 in the low-concentration interval to 1.30 in the higher-concentration interval, indicating weakened concentration sensitivity at higher CuCl₂ concentration. Validation using commercial c-Si solar cells showed preferential removal of the front-side Ag grid, whereas the rear-side Al electrode was less affected under the same conditions. The medium also exhibited good recyclability, retaining 97.1% of its initial Ag-wire leaching performance after 32 cycles. These results identify the ChCl:Ac-CuCl₂ system as a reusable medium for selective Ag leaching from c-Si solar cells and clarify how solvent structure, interfacial reaction, and kinetic constraints jointly govern its performance.