Closing the Loop: A Sustainable Resource Management Strategy for Valorizing Steel Slag into Nanosorbents for Water Remediation

Steel slag, a major industrial waste, was converted into iron oxide nanoparticles (IONPs) via a plant-extract-mediated synthesis using Ginkgo biloba leaf extract. The resulting nanomaterial demonstrated high effectiveness as an adsorbent for the model cationic dye methylene blue, with a capacity of 294.97 mg/g and removal efficiency >98%. Adsorption followed pseudo-second-order kinetics and the Freundlich isotherm, with DFT simulations indicating charge-transfer-enhanced electrostatic interactions as the key mechanism. The process adopts a circular economy perspective by recovering iron as a nano-adsorbent, concentrating co-leached Mn/Mg into a manageable residue, and directing the primary CaSO4/SiO2-rich residue toward construction applications. While the nanoparticle synthesis step incorporates green chemistry principles, the study highlights the integration of hydrometallurgical waste processing with bio-inspired nanomaterial fabrication as a sustainable resource management strategy.