Microbial immobilisation and adaptation to Cu2+ enhances microbial Fe2+ oxidation for bioleaching of printed circuit boards in the presence of mixed metal ions

Bacterial acidic agents-assisted multi-elemental (Ni, Co, and Li) leaching of used lithium-ion batteries at high pulp densities

Accumulating used lithium-ion battery cathodes and associated environmental concerns necessitate efficient recycling strategies. Biohydrometallurgical processes often face challenges at high pulp densities due to microbial inhibition and substrate limitations, particularly sulfur availability, which is crucial for bacterial acidic agent production. This study introduces a breakthrough spent-medium bioleaching approach optimized for high-pulp-density conditions. We systematically addressed key challenges, including bacterial inhibition, sulfuric acid optimization, and its impact on critical metal dissolution. Using response surface methodology, we optimized sulfur dosage, inoculum size, and initial pH to enhance bacterial acidic agent production by Acidithiobacillus thiooxidans, achieving a sulfate concentration of 40.3 g/l and a ΔpH of 1.87. Metal removal efficiency was assessed at pulp densities of 10-50 g/l, demonstrating high extraction rates of Li (92%), Ni (88%), and Co (78%) at 50 g/l after 7 days. Comparative analysis with chemical leaching confirmed the effectiveness of this green strategy. Furthermore, a kinetic study using the Avrami equation and shrinking core model revealed that both models yield comparable results, and diffusion through the product layer controlled the leaching rate. This study presents a comprehensive and sustainable strategy for waste recycling at high pulp densities by integrating process optimization, spent-medium bioleaching, and kinetic modeling for critical metal extraction from lithium-ion battery cathodes.

Innovative Approaches to Tin Recovery from Low-Grade Secondary Resources: A Focus on (Bio)hydrometallurgical and Solvometallurgical Methods

Tin, although not considered a critical material in all world regions, is a key material for modern technologies. The projected scarcity of tin in the coming decades emphasizes the need for efficient recycling methods to maintain uninterrupted supply chains. This review article focuses on the recovery of tin from low-grade secondary sources, specifically obsolete printed circuit boards (PCBs) and liquid crystal displays (LCDs). In both types of waste, tin occurs in various concentrations and in different chemical forms-a few percent as metal or alloy in PCBs and several hundred ppm as tin(IV) oxide in LCDs. This article presents pretreatment methods to preconcentrate tin and enhance subsequent leaching. It discusses not only conventional acid and alkaline leaching techniques but also the use of complexing agents and the challenges associated with bioleaching. Due to the dilution of the resulting leachates, advanced methods for tin ion separation and preconcentration before final product recovery are shown. Solvometallurgical methods employing deep eutectic solvents or ionic liquids, are also discussed; although promising, they still remain under development.