Co-treatment of spent cathode carbon in caustic and acid leaching process under ultrasonic assisted for preparation of SiC

Spent cathode carbon (SCC) from aluminum electrolysis has been treated in ultrasonic-assisted caustic leaching and acid leaching process, and purified SCC used as carbon source to synthesize silicon carbide (SiC) was investigated. Chemical and mineralogical properties have been characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and thermogravimetry and differential scanning calorimetry (TGA-DSC). Various experimental factors temperature, time, liquid-solid ratio, ultrasonic power, and initial concentration of alkali or acid affecting on SCC leaching result were studied. After co-treatment with ultrasonic-assisted caustic leaching and acid leaching, carbon content of leaching residue was 97.53%. SiC power was synthesized by carbothermal reduction at 1600 °C, as a result of yield of 76.43%, and specific surface area of 4378 cm²/g. This is the first report of using purified SCC and gangue to prepare SiC. The two industrial wastes have been used newly as secondary sources. Furthermore, ultrasonic showed significant effect in SCC leaching process.