In situ phase regulation enables low-carbon electrochemical recycling of spent lead paste

Abstract

The sustainable recycling of hazardous spent lead paste (SLP) remains a critical challenge, severely bottlenecked by the electrochemical inertness and phase heterogeneity of refractory lead oxides. Here, we demonstrate that in situ phase regulation enables a step change in the environmental performance of electrochemical lead recovery. Density functional theory shows that converting PbO₂ and PbO to PbSO₄ shifts the electroreduction pathway from diffusion-limited solid-state reduction to a dissolution-electrodeposition mechanism. Ultrasound-assisted treatment accelerates this transformation, reducing the apparent activation energy by 16.5%. Machine learning optimization of 399 datasets achieves near-complete phase homogenization (97.82% PbSO₄), allowing subsequent solid-phase electrolysis to produce high-purity lead with a specific energy consumption of 565.08 kWh·t⁻¹·Pb, 35.8% lower than untreated SLP. This work establishes a low-carbon, environmentally effective pathway for sustainable recycling of lead-containing waste.