Study on Kinetics of Vacuum Heat Treatment Process of the Spent Cathode Carbon Blocks from Aluminum Smelters

The spent cathode carbon block (SCCB) produced from the overhaul aluminum reduction cell is regarded as hazardous solid waste because it contains a large amount of soluble fluoride and small amount of cyanide. Coupling vacuum-heating method is considered an effective way to address the issues of such hazardous waste. Herein, SCCB is processed under the conditions of 3000 Pa and 1673–1973 K. The correlation between soluble fluoride content and treatment time was analyzed. The apparent activation energy of the detoxification reaction was calculated based on the Arrhenius equation. The rate-determining step of the detoxification process has also been analyzed in detail. The results show that the detoxification process is a first-order reaction. The apparent activation energy was k = 15.08 kJ mol−1, and gas diffusion was the rate-determining step of the detoxification reaction.