Novel recycling process for lead-acid battery paste without SO2 generation - Reaction mechanism and industrial pilot campaign

This study proposes an innovative and environment-friendly method for recycling spent lead-acid batteries without SO 2 generation. Iron-containing waste was employed as a sulfur-fixing agent to retain sulfur as ferrous matte, which eliminated the generation and emissions of gaseous SO 2 . This work investigated the thermodynamic and experimental feasibility and conversion mechanism of the method, and evaluated its industrial applicability. A bench-scale test showed direct recoveries of 93.5% and 97.7% in crude lead and ferrous matte for lead and sulfur, respectively. The phase transformation mechanism study indicated that metallic lead from the lead paste was extracted mainly through the sequence of PbSO 4 → C / C O $\stackrel{C/CO}{\to }$ PbS → F e 3 O 4 $\stackrel{F{e}_3{O}_4}{\to }$ PbO → C / C O $\stackrel{C/CO}{\to }$ Pb. Sulfur in PbSO 4 was thus first transferred to PbS and finally fixed as FeS. An industrial-scale pilot campaign was also conducted to confirm the feasibility and reliability of the new process.