Lead-acid batteries (LABs) and the thermogravimetric analysis of Pb metal reduction from PbO2 via microwave heating at 2.45 GHz

The lead (Pb) in lead-acid batteries (LABs) accounts for up to 60% of their total weight and 80% of the metallic Pb produced worldwide. As a toxic substance but sought-after resource, developing a method to reclaim Pb from spent batteries, both safely and efficiently, is highly desirable. To this end, this paper explores the application of microwave heating to reduce Pb from PbO2, a component of LAB pastes, using a carbon (C) reductant. Various experiments were conducted between 200 and 1000 W to determine mass loss kinetics using a homemade thermogravimetric apparatus. The mechanisms and kinetics of the reactions, and their resultant phases, are discussed in comparison to differential thermal analyses (TG-DTA) of the same samples. Microwave heating was found to be highly effective, resulting in up to a 97% recovery of Pb metal at < 300 °C; however, complete reduction was unrealized due to crucible interference, microwave penetration depth, and the reflection of microwaves as Pb metal formed. The reduction and decomposition reactions were evaluated using X-ray diffraction (XRD).