Competitive crystallization, in situ separation and solidification mechanism of Cr-spinel crystal from Cr-bearing slag

Abstract

Cr-Spinel has been reported as an outstanding phase to solidify Cr in Cr-bearing slag, while the ambiguity of the solidification mechanism for Cr-spinel crystals significantly limits the recovery and utilization of Cr in the Cr-bearing slag. In this study, the competitive crystallization, in situ separation, and solidification mechanism of Cr-spinel crystals were studied for efficient solidification and recovery of Cr in Cr-bearing slag. The competitive crystallization behavior of Cr in Cr-spinel indicated that the Fe and Mn substituted in Cr-spinel based on the mole ratio of (Cr + Al)/(Fe + Mn) ≈ 2.0 in the AB₂O₄ structure, and the crystallization tendency of Cr to Cr-spinel was enhanced with the substitution of Fe and Mn. The high-purity crystals of Cr-spinel with various Cr₂O₃ contents of 61.03–61.80 wt% were selectively separated from the molten Cr-bearing slag by supergravity. Moreover, the solidification mechanism of Cr-spinel crystals was confirmed by the characterization of molecular formula and lattice parameters, and it was found that the occupancy of Cr in the Cr-spinel lattice remained constant with the substitution of Fe and Mn, which provided some necessary basic data for the efficient solidification and recovery of Cr in Cr-bearing slag.