Research on synergistic disposal and high-value utilization of secondary aluminum dross and spent carbon anode

Abstract

Significant hazardous by-products emerged from the aluminum electrolysis realm, including secondary aluminum dross (SAD) and spent carbon anodes (SCA), with an anticipated annual yield surpassing 800,000 tons. These solid wastes showcase distinct complexation properties enriched with aluminum and fluoride. In this paper, aluminum or aluminum compounds will be extracted from SAD by sulfuric acid first to prepare an aluminum sulfate solution, which could be used to extract cryolite in SCA by Al-F complexation. A second-step alkaline leaching is aimed at enhancing Al and F dissolution from the first-step leaching acid-leaching residue of SAD and SCA. Under optimal conditions, the ensuing data reveals the soluble components in SAD reaching a leaching zenith of 90.3%, with the Al2O3 faction standing tall at 91.08%. Simultaneously, SCA's F leaching efficiency hits an impressive 98.20%, hence the carbon residue enriched with a purity of 75.5%. Finally, the acid-leaching solution and alkaline-leaching solution could be mixed to prepare flexibly and controllably aluminum fluoride or cryolite by adjusting the pH value and Al/F molar ratio of filtrate. This avant-garde approach illuminates a sustainable, ecologically harmonious route for synergistic disposal and high-value utilization of hazardous solid wastes from the aluminum smelting process.