Sodium Removal from Aluminum Electrolysis Spent Anodes (Butts) Through Aluminum Sulfate Hydrothermal Acid Leaching

Spent anodes (butts) are the remaining portion of prebaked anodes after consumption, which are reintroduced into the production of prebaked anodes after treatment. Among these residues, the main harmful element, sodium, tends to accumulate with the repeated recycling of the butts. This accumulation increases the air reactivity of prebaked anodes and consequently reduces their quality. In this study, aluminum sulfate hydrothermal acid leaching was used to remove sodium from the butts. The effects of leaching temperature, Al 3+ concentration, leaching time, and liquid-to-solid ratio on the removal of sodium from the butts were investigated. The sodium removal rate reached 99.42% at a leaching temperature of 90°C, an Al 3+ concentration of 1.5 mol/L, a leaching time of 2.5 h, and a liquid-to-solid ratio of 25 mL/g. This method significantly reduced the sodium content in the butts, offering a new approach for the high-quality recovery of the butts.