Directional Conversion of Valuable Components from Spent Carbon Cathode via High-Temperature Roasting

Spent carbon cathode (SCC), a hazardous solid waste discharged from aluminum electrolysis, exhibits significant fluoride and cyanide leaching toxicities. Existing high-temperature disposal strategies are constrained by high investment costs for specialized equipment, low product added value, and unclear application scenarios, hindering their large-scale implementation. Consequently, substantial quantities of SCC remain underutilized, resulting in the waste of valuable carbon and fluoride components. This study focuses on the targeted conversion of valuable components in SCC through the innovative integration of simple processes, including atmospheric high-temperature roasting, deep purification, Al-based inducer addition, and pH regulation. Volatilization kinetics and solution equilibrium chemistry were used to investigate impurity removal mechanisms and to guide cryolite synthesis, respectively. The results demonstrate the successful recovery of high-purity regenerated graphite with a high carbon content, low sulfur content, and a high degree of graphitization. Simultaneously, cryolite with a high NaF/AlF3 molecular ratio was synthesized from the roasting flue gas absorption liquor by controlling ionic composition and pH. Guided by the principles of cleaner production and resource recycling, the entire recovery process generates negligible waste gas, wastewater, or solid residue emissions. In conclusion, the proposed disposal strategy achieved the targeted conversion of SCC into high-value products while mitigating environmental pollution risks, offering both environmental and economic benefits. This innovative design provides a feasible pathway for the large-scale disposal and utilization of SCC.