Abstract:Aluminum electrolysis carbon slag is a dangerous solid waste continuously produced and inevitable in aluminum electrolysis industry. At present, carbon slag is mainly treated by flotation process. However, due to the low carbon content of flotation carbon slag and the risk of secondary pollution, the prospect of its resource utilization is limited. Effects of HCl concentration, acid leaching temperature, L/S, stirring rate and leaching time on treatment effect were studied by atmospheric pressure acid leaching depth purification. XRD, XRF, leaching toxicity analysis were used to explore the changes of phase composition, element content, leaching toxicity before and after treatment of carbon slag. The results show that carbon content of leached slag rises first and then slows down with the increase of hydrochloric acid concentration, acid leaching temperature, L/S, stirring rate, and acid leaching time. Carbon content of carbon slag rises from 82.67% to 98.05% and fluorine leaching concentration drops from 137.8 mg/L to 62.49 mg/L under the optimum conditions including HCl concentration of 4 mol/L, acid leaching temperature of 60 ℃, stirring rate of 1 200 r/min, L/S=25, and leaching time of 4 h. The atmospheric acid leaching process has technical feasibility to realize deep purification of flotation carbon slag.