Waste-to-waste strategy for lithium-ion battery recycling: Biosorption of Ni, Co and Mn using bergamot pomace

The growing demand for lithium-ion batteries (LIBs) in electric mobility and energy storage systems necessitates sustainable recycling solutions. This study presents a proof-of-concept for the recovery of critical metals, i.e. Nickel (Ni), Manganese (Mn), and Cobalt (Co), from spent LIBs cathodes using an agri-food waste biomass - bergamot pomace (BP) - as a biosorbent. Due to the complexity of the real cathode matrix, a solid experimental strategy with three levels of increasing complexity was designed: starting with single-metal adsorption experiments, moving to a multicomponent synthetic solution reproducing the cationic composition of the cathode, and finally testing a solution obtained through acid leaching of an actual spent cathode. The experimental data were interpreted through a thermodynamic approach, focusing on adsorption isotherm parameters such as affinity constants and maximum adsorption capacities. BP exhibited a total sorption capacity of approximately 0.7 mmol g -1 on real leachates, with a high affinity for Ni, Mn, and Co in diluted solutions (< 30 mg dm -3 ), indicating strong potential for use in secondary recovery steps. This approach improves metal recovery efficiency, potentially compensating for cation losses in conventional methods, and aligns with circular economy principles by valorizing organic waste. The environmental and economic implications of BP production were also evaluated, focusing on energy consumption, global warming potential (GWP), and production costs under laboratory and projected industrial conditions to assess its sustainability as a complementary step in LIBs recycling workflows. These results demonstrate the viability of BP as a low-cost and bio-based material for greener recycling strategies. • Bergamot pomace acts as biosorbent for Ni, Mn, and Co recovery. • Proof-of-concept using real LIB cathode leachates. • High metal affinity enables secondary recovery from dilute solutions. • Sustainable and low-cost complement to hydrometallurgical recycling. • Biomass valorization aligns with circular economy goals.