Clean and Efficient Separation of Aluminum and Sodium From Acid Roasted Slag of Waste Carbon Slag

ABSTRACT Acid‐roasting slag, a by‐product generated during the acid roasting process of solid waste (carbon slag) in aluminum electrolysis, has great potential for value recovery. To recover valuable components, a novel process using carbon powder catalytic calcination was proposed to separate aluminum and sodium. Compared to traditional methods, this process catalyzed by carbon powder significantly reduces temperature (by over 200°C) and energy consumption. Experimental results identified optimal parameters for this process: a slag‐to‐carbon ratio of 0.15:1, calcination temperature of 670°C, duration of 2 h, resulting in a conversion efficiency of NaAl(SO ₄ ) ₂ of 99.8%. The subsequent water leaching step was optimized at an L/S ratio of 10, room temperature, and 2 h, achieving a leaching efficiency of 99.3% for sodium. Additionally, the resulting Na ₂ SO ₄ was converted into high‐purity sodium sulfide through carbon thermal reduction at a Na ₂ SO ₄ to carbon ratio of 0.25:1, 750°C for 2 h, with a Na ₂ S recovery rate of 97.3%. Overall, the carbonization catalytic calcination process has proven to be an effective method for the clean and efficient resource utilization of waste residue after carbon slag acidification.