Ultrasound enhances the recycling process and mechanism of lithium from spent LiFePO4 batteries by Acidithiobacillus ferrooxidans

In this study, the ability of Acidithiobacillus ferrooxidans to oxidize Fe²⁺ to Fe³⁺ and recover battery black powder was investigated, establishing a system for leaching decommissioned lithium iron phosphate battery black powder from A. ferrooxidans. Black powder reduced the consumption of reagents and subsequent pressure for treating iron-bearing minerals using the iron source in waste LiFePO₄ batteries. This study used ultrasonic waves to remove impurities on the surface and cracks in battery black powder, hindering the dissolution layer and enhancing the leaching effect through a cavitation reaction and microbial activation to promote the leaching process. A filter bag experiment was designed using the selective permeability of filter bags to investigate whether the leaching mechanism of A. ferrooxidans lithium iron phosphate is contact or non-contact. Under optimal leaching conditions, the lithium leaching rate reached 99.7%, and the leaching time was reduced from 7 to 5 days, achieving efficient leaching of lithium. The filter bag experiment concluded that A. ferrooxidans leaching of lithium iron phosphate was mainly a contact leaching mechanism.