Tag Archive for: industrial readiness

Secondary aluminum dross and salt slag are heterogeneous secondary resources whose entrained metal, alumina-bearing phases, aluminum nitride (AlN), chlorides, fluorides, and fine particles create coupled recovery and safety constraints. This structured critical narrative review maps 106 publications from 2020 to 2026 and evaluates physical, thermal, aqueous, and product-oriented routes without claiming systematic review or PRISMA compliance. Conservative evidence coding identified one industrial campaign (Class A), one pilot study (Class B), no continuous integrated Class C study, 86 laboratory studies on real dross (Class D), five modeling or proof-of-concept studies (Class E), and 13 supporting reviews or contextual sources. Selected studies reported metallic aluminum recovery above 92% and up to approximately 98%, chloride removal above 92%, and AlN conversion of 92.45–99.03%; these results are not directly comparable because of differences in feed assays, particle size, residence time, and system boundaries. A metal-first sequence is therefore conditionally preferred when the net value of recovered metal justifies the operation and when removal reduces the hydrogen inventory of the wet circuit. Stoichiometrically, 1 kg AlN can generate 0.415 kg NH₃ (0.597 m³ at 25 °C and 1 atm), while 1 kg metallic Al can generate 0.112 kg H₂ (1.360 m³) under complete reaction. Washing, controlled hydrolysis, salt crystallization, gas capture, and mineral conversion must consequently be designed as one integrated system. Laboratory production of alumina, spinel, refractories, adsorbents, or cementitious materials demonstrates conversion, not circularity, unless product specifications, durability, leaching stability, multi-cycle recycle, controlled purges, and harmonized life-cycle and techno-economic boundaries are verified. The review provides route-specific readiness ratings, quantitative design bases, and objective go/no-go gates for industrial development.