Incorporation of desulfurization wastewater to achieve ultra-low energy consumption in electrochemical lead recycling

Abstract

Cleaner and more cost-effective battery recycling techniques are still in demand for improving battery's sustainability. Herein, a novel electrochemical spent lead-acid battery recycling approach with ultra-low energy consumption is proposed in this work, which is achieved via coprocessing with desulfurization wastewater. Desulfurization wastewater (containing sulfite ion, SO32−) is used as reducing agent for lead paste leaching process and electrolyte for the subsequent solid-state electrolysis process respectively, while the wastewater can be effectively treated. Morphology and crystal structure characterizations indicate the lead paste leached by simulated desulfurization wastewater is mainly composed of lead suboxide (Pb2O). Electrochemical analyses reveal that charge demand for cathodic electro-reducing desulfurization wastewater leached lead paste into metallic lead is significantly lower than original lead paste. Furthermore, sulfite ion is oxidated on anode during the solid-state electrolysis process, thereby decreasing the anodic potential compared to the traditional oxygen evolution reaction. Thus, the introduction of desulfurization wastewater significantly reduces the overall energy consumption of the solid-state electrolysis by influencing both of the anodic and cathodic processes. The energy consumption to recycle a ton of lead is 169.8–230.5 kWh under optimized operation conditions, which is only 21.2–51.8% of the traditional electrochemical lead recycling process, while 1.6–1.8 m3 desulfurization wastewater with 50,000 mg L−1 chemical oxygen demand can be treated. Therefore, the co-processing of spent lead-acid battery and desulfurization wastewater is proven to be a win-win waste disposal strategy.