A large number of iron ore tailings (IOTs) are produced in steel industry, posing threat to the environment during its storage and disposal. To effectively reutilize Fe in IOTs, we propose a comprehensive utilization scheme: (1) most Fe in IOTs is extracted by concentrated hydrochloric acid to form FeCl3 flocculants; (2) after separation from the FeCl3 flocculants, a small amount of Fe is absorbed on the residue solids, which is further washed out to synthesize micron Fe3O4 as magnetic seeds. Results show that the as-synthetic FeCl3 flocculants meet the product standard for FeCl3 flocculants in China (GB/T 4482-2018) after a series of treatments including rotary evaporation, neutralization, and dilution and have comparable performance with commercial polyaluminum chloride (PAC) and polyaluminum ferric chloride (PAFC). Moreover, the addition of synthetic superparamagnetic Fe3O4 (as magnetic seeds) doubled the flocculation rate compared with as-synthetic FeCl3 flocculants alone. Finally, the reutilization of Fe in IOTs can create a direct economic value of ¥ 1.27/kg IOTs, and produce 745 g high-silicon residues for further reutilization, which indicates that our comprehensive utilization scheme is of great application potential.
Keywords: Acid extraction; IOTs; Magnetic flocculation; Magnetic seeds; Reutilization.