Batch Production of Lead Sulfate from Spent Lead–Acid Batteries via an Oxygen-Free Roasting Route: A Negative-Carbon Strategy

Abstract

Multicomponent lead compounds, including lead (Pb), lead oxide (PbO), lead dioxide (PbO 2 ), and lead sulfate (PbSO 4 ), in spent lead−acid batteries (LABs), if not properly disposed of and recycled, will cause serious pollution and damage to the ecological environment. Pyrometallurgical smelting performed above 1000 °C often incurs high energy consumption and lead pollution. In this study, a low-temperature (300 °C), oxygen-free roasting process was proposed. With potassium bisulfate (KHSO 4 ) as the roasting reagent, the uniform conversion of multicomponent lead compounds from spent lead paste (SLP) to PbSO 4 was successfully realized in one step. We observed that PbO 2 species were relatively chemically stable, during the oxygen-free roasting. However, the decomposition of PbO 2 into PbO can be achieved by heating to 300 °C, resulting in an effective conversion to PbSO 4 . The optimal conditions for PbSO 4 production were a heating temperature of 300 °C, an SLP/KHSO 4 mass ratio of 1:1, and a holding time of 10.0 min. Life cycle assessment results show that the recycling of 1.0 t spent LABs can reduce carbon emissions of 2.45 t CO 2 and smog of 0.13 t. Our research provides an emission-free, low-temperature, and negative-carbon strategy for facile and cost-effective recycling of spent LABs, as an alternative to traditional pyrometallurgical smelting.