PFAS released from the metals recovery process of the lithium-ion battery black mass

Recycling of Li-ion batteries (LiBs) for metal recovery has gained increasing attention in recent years. Batteries contain per- and polyfluoroalkyl substances (PFAS), however, their behaviour during battery recycling is still not well understood. This study aims to (i) characterise the presence of PFAS in LiBs black mass collected from various recycling factories in Australia, and (ii) investigate the fate of PFAS during the metal recovery process. The concentration of bis-perfluoromethanesulfonimide (bis-FMeSI) (C₂) in the black mass was up to 51,000 µg kg^-1. Other emerging and legacy PFAS were present, with concentrations varying from 0.1 to100 µg kg^-1. The complementary analysis results of extractable organically bound fluorine and Fluorine K-edge X-ray adsorption near-edge structure indicates that the LiBs black mass mainly consists of bis-FMeSI (C₂) and LiPF₆ as the main PFAS analytes (40 - 80% fluorine equivalent), however other unknown PFAS may also be present. The long-chain PFAS are more difficult to leach compared to the short-chain PFAS. H₂SO₄ leaches 58% bis-FMeSI which is the highest compared to HNO₃ (51%) and HCl (40.4%). During the precipitation stage, adding H₂O₂ to the H₂SO₄ (5% v/v) leaching agent increased bis-FMeSI adsorption onto metal precipitates by 40%. Using PiFM analysis, PFAS are found predominantly present as surface-associated species within binder- and carbon-rich domains, and the leaching mechanism is strongly attributable to the disruption of these surface-accessible phases. This work constructs the first baseline for the relevant research about the trade-off between metal recovery and PFAS pollutants in the LiBs recycling process.