Efficient Leaching Behavior of Lithium from Spent Cathode Carbon Blocks Under Three Typical Acids

With the rapid development of the aluminum industry, spent cathode carbon (SCC) blocks is inevitably generated during the aluminum electrolysis production process, which is a hazardous solid waste. This study explores the efficient recovery of valuable metal lithium from SCC blocks using hydrochloric acid, sulfuric acid, and phosphoric acid. The leaching behavior of the typical acids are examined in detail, and their leaching mechanisms are analyzed in depth. The effects of temperature, acid concentration, leaching time, and liquid-solid ratio on lithium leaching rate were studied through single factor experiments. The results showed that hydrochloric acid, sulfuric acid, and phosphoric acid exhibited certain differences in lithium leaching. Among them, sulfuric acid achieved a maximum lithium ion leaching rate of 98.31% under the conditions of leaching temperature of 80 ℃ liquid-solid ratio of 10:1, leaching time of 2 hours, and sulfuric acid concentration of 2 mol/L. The leaching effect of hydrochloric acid is second to sulfuric acid, while the leaching effect of phosphoric acid is the worst. By combining characterization techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), the reaction mechanism between acid and lithium compounds in SCC blocks was revealed.