An efficient and clean treatment of spent carbon cathode via fluorination roasting: Deep separation strategy for insoluble aluminosilicates

Currently, the efficient recovery of graphite from spent carbon cathode (SCC) remains challenging under conventional conditions due to the coexistence of insoluble aluminosilicates. This study aimed to explore deep separation strategies for insoluble aluminosilicates. A fluorination roasting process for efficient separation of insoluble aluminosilicates was developed based on thermodynamic calculations. The parameters of fluorination roasting and water leaching were sequentially optimized. In-situ XRD, TG-MS, and molecular dynamics simulations were used to explore the dissociation of insoluble aluminosilicates during fluorination roasting. The separation mechanism of insoluble aluminosilicate was proposed. Subsequently, the recovered graphite carbon (RGC) was deeply purified. Results showed that the purified graphite carbon with high carbon content (99.52 wt%) and low fluorine leaching toxicity (7.6 mg·L−1) was obtained. On this basis, SCC, RGC, and PGC were used to partially replace calcined petroleum coke (CPC) to prepare carbon anodes for aluminum electrolysis. The carbon anode prepared by PGC blending demonstrated comparable performance to that of the CPC-based carbon anode. Finally, ammonium fluoride was successfully regenerated through the cascade utilization of exhaust gas, water, and acid leachate. The proposed dissociation and resource utilization strategy were anticipated to achieve the simultaneous safe disposal and efficient recycling of SCC.