Optimization of Spent Cathode Carbon Purification Process under Ultrasonic Action Using Taguchi Method

Optimum condition in caustic leaching test of spent cathode carbon (SCC) from aluminum electrolysis was investigated. The primary and secondary relationship of experimental factors was determined by Taguchi method, under traditional mechanical agitation and ultrasonic, respectively. Initial alkali concentration had significant influence both in ultrasonic-assisted and mechanical agitation leaching processes, and the effect was second only to that of ultrasonic power. Optimal parameters were temperature of 60 °C, leaching time of 50 min, liquid–solid ratio of 10 mL/g, initial alkali concentration of 1 mol/L, particle size of −100 mesh, and ultrasonic power of 400 W. Purity of carbon powder obtained from treatment of spent cathode carbon at optimum conditions was 94.39%. Wastewater was reused after treated. It can be concluded that SCC purification conditions were optimized by synergistic effect of orthogonal and single-factor trails. Ultrasonic plays a notable effect in SCC caustic leaching process.