Estimation of Metallic Aluminum Content in Aluminum Dross and Dust by Selective Dilute-Acid Leaching with Slow Dissolution of AlN

Aluminum production is energy-intensive and generates large quantities of dross. Aluminum dross, which forms on the melt surface during the melting and refining stages, consists primarily of aluminum oxides and nitrides. Meanwhile, aluminum dust captured in emission control systems contains additional phases, including carbides. Dross containing <20 wt% metallic aluminum is mostly landfilled, releasing ammonia and flammable gases upon contact with water. The oxidation reaction of metallic aluminum contained in aluminum by-products recovered during the recycling process generates a significant amount of heat, thereby lowering the need for external energy. In addition, recycling these by-products lessens the burden on landfills. Quantifying the metallic aluminum content is therefore essential for assessing the true recycling value of the by-products. In this study, the metallic aluminum content of aluminum dross and dust was estimated using selective dilute-acid leaching. Synthetic oxide reference samples were prepared, and the Al, Si, and Mg concentrations in dilute hydrochloric acid (1.16 mol·kg−1) were compared between the references and by-products. The dissolved Al concentration reached ≈29 wt% for the dross within 6 h, with an additional AlN-derived contribution of ≤4 wt% upon prolonged leaching and ≈25 wt% for the dust, independent of the leaching time; the oxide references showed negligible dissolution. Hence, single-step dilute-acid leaching can serve as a rapid method for classifying aluminum by-products between landfill and remelting routes.