2018 Volume 59 Issue 10 Pages 1659-1664
High-percentage iron resources in nickel slags were recovered as magnetite via molten oxidation process, and the transfer behavior of Fe element was studied. The elemental distribution in oxidized slag samples, the influence of atmosphere, holding temperature and time on magnetite crystal growth, and Fe element distribution in magnetic materials were also investigated. It was found that magnetite could be produced from fayalite or hortonolite in nickel slags during molten oxidation with CaO as a modifier, air as an oxidizer, accompanying with the enrichment of Fe, Co, Ni and Cu. The select of atmosphere is very important during the precipitation and growth of the magnetite crystals. The magnetite crystals precipitated invisibly or slightly in argon atmosphere, while exhibited dendritic structures with crystallization content of ∼18.5% in air atmosphere. Especially, after blowing air into molten slag for 30 min, magnetite crystals develop well-distributed and complete, resulting in its crystallization content increases up to 33.5%. The Fe content in the matrix of oxidized samples remained approximately constant after holding for 20 min. Mössbauer spectra analysis indicates that the 89.6% of Fe exists in magnetite phases, while only 10.4% of Fe in hedenbergite. It was also found that Ni and Co simultaneously concentrate in the magnetite phase, indicating that Fe, Ni, and Co can be recovered effectively from nickel slag.