Recycling of Spent Cathode Carbon from Aluminum Electrolysis: Detoxification Approaches, Resource Utilization, and Environmental Perspectives

During aluminum (Al) electrolysis, large amounts of spent cathode carbon (SCC) are generated, often contaminated with hazardous substances such as fluorides and cyanides. As a result, SCC is classified as a dangerous solid waste posing long-term risks to ecosystems and human health if untreated. This review comprehensively analyzes the chemical composition, formation mechanisms, and environmental hazards of SCC, and summarizes current physical and chemical remediation strategies. Unlike previous reviews, it integrates a comparative life cycle assessment (LCA) to evaluate the environmental performance of different SCC treatment routes, offering a holistic view of their sustainability. Additionally, it highlights opportunities for recovering valuable elements, particularly carbon (C), fluorine (F), and lithium (Li), and explores high-value recycling pathways such as battery anodes, graphene, and SiC semiconductors. Although many studies focus on laboratory-scale recovery efficiencies, environmental sustainability assessments remain scarce. Integrated processes including molten salt roasting, ultrasonic-assisted leaching, and cryolite regeneration show promise for detoxification and resource recovery. However, challenges such as C passivation, fluoride stabilization, and high energy demands persist. By combining technological and environmental perspectives, this review provides a framework for developing scalable, low-emission SCC recycling technologies aligned with circular economy principles.