Enhanced extraction of aluminum from secondary aluminum dross: Synergistic effects of two-step roasting with (NH4)2SO4 and Na2CO3 on the activation of inert aluminum species

Secondary aluminum dross (SAD), a major solid waste in the aluminum industry, possesses a complex composition representing both a valuable resource and a significant environmental challenge. Approximately 30%–40% of its aluminum content consists of inert species (α-Al 2 O 3 and MgAl 2 O 4 ). In this study, a method for the comprehensive extraction of Al from SAD was developed, which achieved 96% extraction efficiency. The process involved a two-step roasting sequence (first with (NH 4 ) 2 SO 4 at 350°C, then with Na 2 CO 3 at 800°C) and subsequent aqueous leaching. Key parameters, including additive dosage, roasting conditions, and leaching variables, were systematically investigated to optimize aluminum recovery. Mechanistic analysis revealed that (NH 4 ) 2 SO 4 destabilizes the Mg–Al bonds within the MgAl 2 O 4 structure, converting Al into the labile Al 2 (SO 4 ) 3 form. Subsequently, Na 2 CO 3 promotes the structural degradation of α-Al 2 O 3 . Consequently, most inert aluminum species in SAD are converted into soluble aluminum salts. This work provides a targeted activation strategy to overcome technical barriers in extracting inert aluminum, thus establishing a feasible route for total Al recovery from SAD.