The continuous demand for lithium-ion batteries (LIBs) in consumer products and electric vehicles (EVs) has raised concerns about their environmental impact when not disposed of properly. Among the components of a spent LIB, the recovery of heavy metals, such as nickel, manganese, and cobalt, from cathode materials is the most critical. While biohydrometallurgy is a promising method for this recovery, it relies on large quantities of chemicals such as iron sulfate (FeSO4) as the energy source, which can limit its scalability. In this work, we seek to develop a modified biohydrometallurgy process that is less dependent on external chemical fuels. For this purpose, we examined the feasibility of replacing the FeSO4 salt with metallic iron (Fe) or stainless steel (SS), which is readily available in spent batteries as protective cases. The modification of the culture growth through the utilization of abundant metallic Fe or SS is expected to lower costs and limit chemical transportation, which will likely decrease potential detrimental environmental impacts in comparison with other recycling methods. The growth profile of the autotrophic bacterium Acidithiobacillus ferrooxidans (Atf) was studied after the initial acidification with H2SO4 or HCl. The resulting culture was then used to leach model cathode materials made of NMC622 (Ni/Mn/Co = 6:2:2). Near-unity leaching efficiencies were measured on all four elements of interest, Li, Ni, Mn, and Co, when compared with those by aqua regia-based digestion. This new bioleaching process opens the door to efficiently recovering cathode metals while further simplifying the cultivation process, promising scaled-up applications.

The continuous demand for lithium-ion batteries (LIBs) in consumer products and electric vehicles (EVs) has raised concerns about their environmental impact when not disposed of properly. Among the co...

Acidithiobacillus spp. have traditionally been utilized to extract metals from mineral ores through bioleaching. This process has recently expanded to include artificial ores, such as those derived from municipal solid waste incineration (MSWI) residues. Previous studies have indicated that microbial adaptation enhances bioleaching efficiency, prompting this study to identify proteins involved in the adaptation of A. ferridurans to MSWI residues. We employed data-independent acquisition-parallel accumulation serial fragmentation to determine the proteomic response of A. ferridurans DSM 583 to three distinct materials: bottom ash (BA), kettle ash (KA), and filter ash (FA), which represent typical MSWI residues. Our findings indicate that, irrespective of the residue type, a suite of membrane transporters, porins, efflux pumps, and specific electron and cation transfer proteins was notably upregulated. The upregulation of certain proteins involved in anaerobic pathways suggested the development of a spontaneous microaerobic environment, which minimally impacted the bioleaching efficiency. Additionally, the adaptation was most efficient at half the target FA concentration, marked by a significant increase in the detoxification and efflux systems required by microorganisms to tolerate high heavy metal concentrations. Given that metal recovery peaked at lower FA concentrations for most metals of interest, further adaptation at the level of protein expression may not be warranted for improved bioleaching outcomes.

Ionic rare earth ore (IREO) has a high abundance of medium and heavy rare earth elements (REEs), making it a vital strategic resource for China. In this work, two typical microorganisms, Aspergillus niger and Acidithiobacillus ferrooxidans, were used to study the interaction mechanism during the bioleaching of IREO under acidic conditions. The results revealed some differences in the interaction and leaching effects of A. niger and A. ferrooxidans on ionic rare earth minerals. A. niger mainly forms rare earth complexes with rare earth ions in IREO by secreting metabolites such as organic acids, thereby promoting the release of REEs, and it has a strong adsorption capacity for Yb. A. ferrooxidans promotes the release of REEs from rare earth minerals, primarily through iron–sulfur oxidation. The differential expression of metabolic genes (e.g., gpmL, FabF, FASN) associated with major metabolite secretion indicates their correlation with the leaching process. The above results reveal the role of the typical acid-producing microorganisms A. niger and A. ferrooxidans and their metabolites in the leaching of IREO, which is valuable for understanding the interaction mechanisms between microorganisms and IREO under acidic conditions.

**Abstract:** This paper presents a novel approach to enhancing lithium recovery from black powder waste generated during lithium-ion battery recycling. We propose the utilization of genetically optimized *Acidithiobacillus ferrooxidans* strains within a microfluidic reactor system coupled with dynamic pH control. This integrated system leverages the inherent bioleaching capabilities of *A. ferrooxidans* while concurrently addressing limitations associated with traditional bioleaching processes. Specifically, we focus on enhancing lithium solubility and extraction efficiency through engineered metabolic pathways and precise control of environmental parameters, leading to a projected 35% improvement in lithium recovery compared to conventional methods and reduced overall process time by 20%.

**Abstract:** This paper details a novel, highly efficient method for recovering valuable trace metals (silver, palladium, indium, gallium) from end-of-life photovoltaic (PV) solar panels using a bioleaching process enhanced by magnetically separable nanoparticle catalysts. Leveraging *Acidithiobacillus ferrooxidans* bacterial strains, combined with iron oxide nanoparticles functionalized with chelating ligands, we achieve significantly improved metal extraction kinetics and selectivity compared to traditional bioleaching approaches.