Hydrometallurgical valorization of strontium ferrite magnet sludge for the selective production of high-purity hematite (α-Fe2O3) and strontium carbonate (SrCO3)

This study presents an integrated hydrometallurgical approach for valorizing strontium ferrite sludge generated from the magnet manufacturing industry by selectively recovering iron (Fe) and strontium (Sr) into high-purity products. The process employed sulfuric acid leaching under optimized conditions (4.0 mol L -1 H 2 SO 4 , 90°C, solid-to-liquid ratio of 40 g L -1 ), achieving near-complete Fe dissolution while simultaneously precipitating Sr as strontium sulfate (SrSO 4 ). The Fe-rich leachate underwent pH-controlled precipitation followed by thermal treatment to yield phase-pure hematite (α-Fe 2 O 3 ). In parallel, the SrSO 4 precipitate was converted to strontium carbonate (SrCO 3 ) via a double-ion replacement reaction with aqueous Na 2 CO 3 , which proceeded to completion within 1.5 h and yielded a high-purity product with platelet-like morphology. This integrated process offers a sustainable, economically viable pathway to transform industrial waste into two valuable materials, thereby advancing circular-economy principles and sustainable waste-management strategies in the magnet manufacturing sector. • Nearly-complete iron recovery under optimized leaching conditions (4.0 mol L -1 H 2 SO 4 , 90 °C, S/L 40 g L -1 ). • Selective precipitation of strontium as SrSO 4 , enabling effective separation of Fe and Sr. • Production of phase-pure α-Fe 2 O 3 with morphology suitable for pigment and corrosion-resistant coating applications. • Efficient conversion of SrSO 4 into high-purity SrCO 3 with platelet-like morphology, relevant to ceramics, pyrotechnics, and electronic components.