Efficient extraction of metals from industrially produced pyrolytic black powder using citric acid: Process optimization and leaching mechanism

Abstract

Full-component pyrolysis can process organic components and reduce cathode materials, making it a key focus in green recycling of lithium-ion batteries (LIBs). However, the leaching mechanism and kinetics of pyrolyzed black powder in organic acid systems remain unclear, with most research still at the laboratory stage. This study pioneers the exploration of the leaching behavior and reaction mechanism of valuable metal extraction from industrial-scale pyrolyzed black powder using citric acid. The effects of various leaching conditions on the extraction of metals were investigated by single factor experiments and response surface method. Under optimal conditions, the leaching efficiencies of Li, Ni, Co, and Mn all exceeded 97%. Kinetic analysis revealed that the leaching process was controlled by internal diffusion, with the apparent activation energies for Li, Ni, Co, and Mn being 17.89, 23.14, 20.27, and 15.21 kJ/mol, respectively. Additionally, residue characterization identified FePO₄ formation as the primary inhibitor of iron dissolution.

Keywords

spent lithium-ion battery / pyrolysis / leaching kinetics / response surface methodology / citric acid

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