A New Pyrometallurgical Recycling Technique for Lead Battery Paste Without SO₂ Generation—A Thermodynamic and Experimental Investigation

An innovative lead recycling process from scrap lead-acid battery paste is presented. The novelty in the process is avoiding SO₂ generation and emission by using reductive sulfur-fixing technique. Iron-bearing secondary wastes produced from metallurgical industry were utilized as sulfur-fixing agent to capture sulfur in the form of FeS (s) instead of generation of SO₂ (g). Na₂CO₃ molten salt was added to the smelting system to speed the reactions and improve valuable metals’ recovery and sulfur-fixation efficiency. Furthermore, this process can simultaneously co-treat various lead and iron-bearing wastes. At the same time, some precious metals, such as Au and Ag, contained in iron-bearing wastes can be recovered. The feasibility and reliability of this process was investigated thermodynamically and experimentally with the help of HSC 9.0 database and XRD and SEM-EDS analysis. A possible reaction mechanism and path in PbSO₄–Fe₂O₃–Na₂CO₃–C smelting system was also clarified.