Rohit Jha

Lithium-ion batteries (LIBs) have become indispensable in present-day energy storage applications, containing portable electronics, electric vehicles, and renewable energy systems. However, rapid growth in LIBs usage has caused a parallel surge in end-of-life batteries, presenting environmental and resource recovery challenges. Among the various components, such as cathode, anode, electrolyte, separators, of LIBs, electrolyte has received minimal attention in recycling efforts. Electrolytes, characterized by their flammable, toxic, and volatile nature, pose significant environmental hazards, including the release of harmful gases and pollutants during disposal. This review focuses on the critical need for efficient recovery and reutilization of electrolytes from spent LIBs. Various recovery methods, including solvent extraction, supercritical fluid extraction, pyrolysis, and freezing, are studied for their effectiveness, efficiency, and environmental impact. Additionally, methods for recycling and regenerating recovered electrolytes into high-purity components for direct reuse are explored, addressing economic and sustainability considerations. Finally, major challenges and research gaps have been discussed. Key research gaps include the degradation of electrolytes during battery operation, complex composition of spent electrolytes, and economic feasibility of large-scale recovery technologies.

Waste printed circuit boards (WPCBs) encompass abundant metals (gold, silver, and copper), along with other harmful materials including brominated epoxy resins, plastics, and heavy metals (lead, mercury, and cadmium). Direct burning and landfilling of WPCBs may cause severe health issues and impair the environment. Therefore, sustainable treatment of WPCBs is necessary to recover valuable metals and remove hazardous materials before disposal. The present work investigates the separation of copper-rich metallic fractions from the WPCBs by the combination of hammer milling and ultrasonic irradiation. Initially, discarded mobile phone PCBs are pre-processed and shortened into 1 × 1 cm². Downscaled WPCBs are fed into the hammer mill to obtain the fine ground powder. The Powdered WPCBs are further processed through ultrasonic treatment to acquire metal-rich fraction. XRD, SEM–EDS, and ICP/AAS analysis revealed that the current technique can efficiently separate the metal-rich fraction without using toxic solvents. Results show the enhancement of copper fraction from 42.73 to 87 wt. % after ultrasonic treatment of WPCBs ground powder. Further, nitric acid leaching has been implemented to metal-rich fractions, and the parameters have been optimized for copper leaching with the assistance of response surface methodology (RSM) of the design of experiments (DOE). Quantitative dissolution (98.96%) of copper occurred using 3.5 M nitric acid within 3 h at 30 °C with 50 GPL pulp density and 500 rpm agitation speed. Finally, the kinetics of the leaching process were studied to conform the kinetics model. Moreover, the activation energy for diffusion (19.075 kJ/mole) and reaction kinetics model (13.29 kJ/mole) has also been calculated. The low energy consumption due to room temperature pre-treatment and effective leaching ensures the industrial feasibility of the proposed process.