Humic acid-mediated mechanism for efficient biodissolution of used lithium batteries

Resource recovery of valuable metals from spent lithium batteries is an inevitable trend for sustainable development. In this study, external regulation was used to enhance the tolerance and stability of strains in the leaching of spent lithium batteries to radically improve the bioleaching efficiency. The leaching of Li, Ni, Co and Mn increased to 100 %, 85.06 %, 74.25 % and 69.44 % respectively after targeted cultivation with HA as compared to the undomesticated strain. In the process of microbial leaching of spent lithium batteries, the metabolites in the Ⅰ, Ⅳ, and Ⅴ regions of the metabolism of the undomesticated bacterial colony had a positive correlation to the dissolution of spent lithium batteries. The metabolites of Ⅰ, Ⅱ, and Ⅴ regions were directly affected by the HA domesticated flora on the dissolution of spent lithium batteries. The excess metabolism of protein substances can significantly promote the reduction of Ni, Co, Mn leaching, and at the same time in the role of a large number of humic substances complexed the toxic metal ions in the system, to ensure the activity of the bacterial colony. It can be seen that the bacteria were domesticated by humic acid, which promoted the bacteria's own metabolism, and the super-metabolised EPS promoted the solubilisation of spent lithium batteries.