Synergistic recovery of silver from end-of-life crystalline silicon photovoltaic cells via direct current-cyanide coupling: performance and mechanism study

Abstract The rapid expansion of the photovoltaic industry has precipitated an imminent waste crisis, creating an urgent need to recover high-value silver from end-of-life modules. While bioleaching is a green process, it is constrained by slow kinetic reactions and low efficiency. Although external electric fields show potential for enhancing the process, their mechanisms of action, particularly at the metabolic and molecular levels remain unclear. This study reveals how milliampere-level direct current overcomes inherent rate-limiting steps in silver bioleaching through a dual mechanism. Under 10 mA stimulation, cyanide yield and silver leaching efficiency increased significantly by 58% and 788% respectively, compared to the control group. The electric field not only accelerated reaction kinetics but also strengthened Ag-C bonds, enhanced [Ag(CN)₂]⁻ stability and reactivity, and increased electron density around silver atoms, thereby promoting leaching. Furthermore, the electric field induced profound metabolic reprogramming within the microbial community. By upregulating key metabolic pathways including those involving glycine and other precursors, it accelerated cyanide synthesis. The electric field selectively enriched genera, such as Pseudomonas with potent amino acid metabolism genes, thereby coordinating the upregulation of core metabolic pathways. The synergistic mechanism of electric field-induced metabolic reprogramming coupled with interfacial reaction activation overcomes the inherent bottlenecks in conventional bioleaching. Preliminary techno-economic assessments confirm the economic viability of this electro-stimulation process, offering an innovative and sustainable strategy for recovering precious metals in urban mining. Graphical Abstract