Extraction of valuable metals from waste lithium iron phosphate batteries by subcritical water leaching method with synergistic waste polyvinyl chloride

In this paper, the effect of leaching valuable metals from waste lithium iron phosphate (LiFePO4) using waste polyvinyl chloride (PVC) as a source of hydrochloric acid under subcritical water treatment conditions was investigated. The effects of various parameters including temperature, reaction time, PVC/LiFePO4 mass ratio, and solid-to-liquid ratio on metal leaching were investigated. The results showed that the leaching of metals and dechlorination of PVC could be achieved simultaneously under subcritical hydrothermal conditions. The solid residues were analyzed using XRD, XPS and SEM-EDS elemental mapping to identify the compounds in the leached solids. ICP-OES analysis showed that optimal reaction conditions, including a temperature of 275 °C, a reaction time of 120 min, a PVC/ LiFePO4 mass ratio of 3:2, and a solid/liquid ratio of 1:10 (g/mL), could effectively leach 99.10 % of Li and 83.12 % Fe. Finally, the Li in the leachate was recovered in the form of Li3PO4 by precipitation. These findings suggest that subcritical water synergistic waste PVC technology is a promising and eco-friendly method to recover Li and Fe from waste lithium iron phosphate.