Pollution-free recycling of lead and sulfur from spent lead-acid batteries via a facile vacuum roasting route
Mengmeng Wang, Quanyin Tan, Jiadong Yu, Dong Xia, Wei Zhang, Congcong Zhang, Zhiyuan Zhang, Junxiong Wang, Kang Liu, Jinhui Li
Abstract
Traditional pyrometallurgical recovery of spent lead-acid batteries (LABs) requires a temperature higher than 1000 °C, with accompanying hard-to-collect wastes such as lead dust and sulfur oxides. Against this background, sodium carbonate (Na2CO3) was proposed as a low-cost, safe, and non-toxic reagent for recycling the high-risk environmental elements lead (Pb) and sulfur (S), in spent LAB lead paste, enabling the one-step conservation of multi-component Pb species, including lead sulfate (PbSO4), metallic lead (Pb), and lead dioxide (PbO2), to lead oxide (PbO) and sodium sulfate (Na2SO4). The possible reaction pathways of Pb and S species in vacuum roasting was confirmed by Gibbs free energy reaction with an estimated average activation energy of 272.5 kJ/mol. The insoluble PbO in the reaction product (PbO/Na2SO4/Na2CO3) can be recycled by vacuum filtration, while Na2CO3 and Na2SO4 were separated using a carbonation method. Life cycle assessment revealed that for recycling 1.0 t of spent LABs, the vacuum roasting can reduce the carbon footprint −2.1 × 103 kg CO2 eq, promoting global decarbonization. The designed route is highlighted with waste-free production and is outlined by the twelve principles of green chemistry, showing its great engineering application potential for spent LAB recycling.