A Bacillus mucilaginosus - ascorbic acid synergistic leaching system for selective lithium recovery from lithium iron phosphate.

Microbial leaching of spent lithium-ion batteries is currently limited by restricted strain selection and low efficiency. Therefore, this study established a synergistic bioleaching system (BM-AAS) driven by Bacillus mucilaginosus (BM) and ascorbic acid (AA), aiming to achieve selective and efficient leaching of lithium from lithium iron phosphate (LiFePO4, LFP) cathode materials. Results indicate that under initial pH 7.3, LFP dosage of 5.0 g·L-1, and inoculation rate of 5 %, the leaching rates of Li and Fe were 48.72 % and 1.96 % respectively. Following the introduction of 1.5 g·L-1 AA, the leaching rates of Li and Fe significantly increased to 98.66 % and 12.55 %. Within this synergistic leaching system, extracellular polymeric substances (EPS) and organic acids metabolized by BM, together with exogenous AA, form a dynamic reaction system exhibiting acid leaching and complexation effects. Concurrently, AA further enhances the electron transfer efficiency of microbially mediated Li leaching. Through reduction and complexation interactions, this dual mechanism drives the reaction equilibrium towards Li+ dissolution, thereby achieving selective and highly efficient Li leaching.