Thermodynamic and Electrolytic Behavior of Lead for Spent Lead Paste Recycling by Different Acidic Slurry Electrolysis Systems

Recovering spent lead paste (SLP) is vital for lead resource sustainability and pollution control. Slurry electrolysis enables simultaneous leaching and electrowinning, yet the influence of ligand chemistry on recovery efficiency remains unclear. This study investigates four acidic systems (chloride, acetate, fluorosilicic, and methanesulfonic) through thermodynamic calculations, species simulations, and experiments, and the results show that acidic media facilitate PbO 2 and PbO conversion to Pb 2+ , while PbSO 4 dissolution specifically requires Cl − complexation. A trade-off between recovery rate and current efficiency was observed. The chloride system achieved the highest recovery rate (92.99%) but lower current efficiency (72.07%) with spongy lead products. Conversely, methanesulfonic and fluorosilicic systems showed higher efficiencies but insufficient recovery rates. The key mechanism involves Cl − competitive adsorption at the anode inhibiting PbO 2 passivation; other systems suffered from passivation, increasing energy consumption. Considering thermodynamics, kinetics, and sustainability, the chloride system demonstrated optimal lead solubility, electrode stability, and recycling potential. This work provides a theoretical basis for selecting electrolyte systems for green and efficient lead recovery.