Hydrometallurgical Recycling of Lithium from the Flue Dust Generated During Pyrometallurgical Processing of LIB Material: A Comparative Analysis of Carbonated and Limewater Leaching

The increasing availability of spent lithium-ion batteries (LIBs), which are rich in valuable metals such as nickel (Ni), cobalt (Co), and lithium (Li), makes them important secondary sources for metal extraction. This study focused on the recovery of Li from a flue dust generated during pyrometallurgical processing of NMC 622 battery material, where Li was present as Li2CO3 and LiF along with various impurities. To selectively extract Li, the flue dust was subjected to leaching with carbonated and limewater under varying temperature and S/L (solid/liquid) ratio. The leachates and leach residues were analyzed to determine Li recovery, co-leached impurities, and to identify possible factors limiting recovery. Leaching with carbonated water at an S/L ratio of 0.05 g/ml, 50 °C and pH of 7.5 resulted in a 70% recovery of Li over 60 min of leaching time, which reduced at higher S/L ratio and temperature. In contrast, when leaching with limewater at 75 °C and S/L ratio of 0.05 g/ml, 77% Li recovery was achieved within 10 min. During these conditions, the pH reached 10. SEM and XRD analysis revealed a CaCO3 precipitate such as calcite, aragonite, and vaterite in varying proportions, causing surface passivation and inhibition of the leaching reaction. Leaching in limewater not only yielded higher Li recovery but also resulted in lower concentration of co-leached impurities (sodium, potassium, aluminum, and zinc), as compared to carbonated water leaching. However, the impurity levels remained high, requiring further purification and separation to produce battery-grade LiOH·H2O.