Process and mechanism for synergistic treatment of spent carbon cathode and red mud by hydrothermal acid-leaching

Abstract

Spent carbon cathode (SCC) and red mud (RM) are two kinds of solid wastes that are harmful to the environment and rich in valuable components from the aluminum industry. In this study, the valuable components of SCC and RM are co-treated by the hydrothermal acid-leaching. The synergistic treatment process is analyzed by phase characterization, thermodynamic calculation, single factor experiment, orthogonal experiment and kinetic study. The results show that the leaching of impurities by the synergistic treatment is better than that of hydrothermal acid-leaching alone. Under the optimal leaching conditions (liquid–solid ratio of 25 mL/g, temperature of 453 K, time of 270 min and acid concentration of 4 mol/L), the leaching efficiency of aluminum and iron reaches 89.70 % and 87.91 %, respectively. For aluminum, the time is the key factor affecting its leaching, the activation energy is 21.52 kJ/mol, and the leaching process is controlled by chemical reaction and solid product layer diffusion. For iron, the acid concentration is the key factor affecting its leaching, the activation energy is 2.82 kJ/mol, and the leaching process is controlled by the solid product layer diffusion. The leaching residue obtain by synergistic hydrothermal acid-leaching is C and SiO2. This process provides a new solution for the treatment and recovery of SCC and RM.