Riciclo di batterie esauste e rifiuti elettronici del settore automobilistico con un approccio di economia circolare mediante processi idrometallurgici integrati

Lithium-ion batteries are widely used worldwide in daily energy storage applications and electronics as they show high energy efficiency, high charge density, and long lifespan. Additionally, alkaline spent batteries are a type of portable battery used in household applications and electronic devices. Due to their high usage, a significant amount of spent batteries is also generated every year as waste. The recycling of these spent batteries is crucial not only for environmental sustainability but also for implementing a circular economy framework. These batteries contain harmful substances, such as electrolytes containing toxic organic solvents like ethylene carbonate (EC), Ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and fluorinated salts like lithium hexafluorophosphate (LiPF6) in lithium spent batteries and other compounds like Hg, Cd and Pb in alkaline spent batteries, that can cause health and environmental issues. The leakage of these electrolytes can contaminate soil and water through metal leaching, cause air pollution by releasing toxic gases such as carbon dioxide and hydrogen fluoride, and create health issues, including skin burns and respiratory problems, for humans. The lithium spent batteries also contain valuable materials such as Cu, Fe, Al, Mn, Co, Ni, Li, and graphite, in contrast, alkaline spent batteries contain potassium (K), manganese (Mn), zinc (Zn), and graphite, which can be recycled from battery waste to minimize raw material dependency in battery manufacturing, making it economically beneficial. There are various methods for recycling this type of waste, including pyrometallurgy, hydrometallurgy, and direct recycling. This study focuses on the development of integrated hydrometallurgical processes compared to conventional methods, which require high energy consumption, making them costly and resulting in increased carbon emissions. The elements from alkaline spent batteries (K, Mn, Zn) were recovered using two different recovery routes, in the form of nitrates and sulfates, via leaching with nitric acid (HNO3) and sulfuric acid (H2SO4), respectively. Each recovery route has its own advantages, depending on the targeted product and its further use in different applications. The elements from spent lithium batteries (NMC-type and LFP-type) were recovered through hydrometallurgical methods using an acid-reductive leaching process (with acid and reducing agents such as H2O2), cementation, precipitation, and solvent extraction under mild conditions, thereby eliminating the high thermal energy demand associated with the roast-leaching route. A good recovery was achieved from NMC-type, with 85% of Cu, 83% of Fe-Al, 92% of Mn, 91% of cobalt, and 94% of nickel, while Li remained in the solution. From the LFP-type, 90.8% of Li and 98% of Fe recovered. Another work was also investigated in this study based on the recovery of graphite from both lithium and alkaline spent batteries. The initial impurities in alkaline batteries were titanium (Ti), iron (Fe), barium (Ba), strontium (Sr), lead (Pb), and silica, which were removed through a two-step leaching process using acid and inorganic salts, yielding high-purity graphite with a purity of more than 94%. Graphite from lithium spent batteries was purified through counter-current leaching, yielding a graphite of good purity of >98%. This recovered graphite can be used for the remanufacturing of graphite anodes for batteries by mixing with the mined graphite. The overall study aimed to facilitate the transition to a circular economy by transforming battery waste into valuable secondary resources, thereby reducing reliance on virgin mining and mitigating environmental risks associated with the clean energy transition.