Ultragravity Centrifugation and Controlled-Oxygen Roasting-Leaching Method to Recover High-Purity Metallic Sodium and Calcium Resources from Spent Sodium Slag

Abstract Sodium metal is critical for indigotin production, sodium-ion batteries, pharmaceuticals, and metallurgy, yet conventional electrolytic production generates large volumes of flammable sodium slag containing 70–85% metallic sodium and 14–29% calcium. Current treatment processes consume excessive reagents and waste valuable sodium resources. Herein, we present an integrated ultragravity centrifugation and controlled oxygen roasting-leaching process for high-purity sodium recovery from sodium slag. Ultragravity centrifugation first separates molten sodium slag into 99.88% high-purity metallic sodium and calcium-rich slag. The calcium-rich slag is then processed via controlled oxygen roasting and atomized leaching to yield NaOH and Ca(OH)2. Trace carbonation of the NaOH solution removes residual Ca(OH)2, and recovered calcium products are converted to CaCl2 to replenish electrolysis feedstock, forming a closed-loop system. Techno-economic analysis confirms 98.5% sodium and 98.0% calcium recovery, avoids high slag disposal costs, and produces high-value products, highlighting industrialization prospects for sustainable sodium slag valorization.