Cationic Effect of Ferrous Ions on Sulfide Capacity of CaO-FetO-Al2O3-SiO2 Slag System

The cationic effect of ferrous ions on the sulfide capacity of CaO-FetO-Al2O3-SiO2 slags was studied from the viewpoint of the ionic structure in the slag using micro-Raman spectroscopy. In the cation-excess region (M2+/2(Fe3+ + Al3+) > 1.0), the sulfide capacity was directly proportional to the basicity of the slags, owing to the S2- stabilizing effect of excess cations. However, in the cation-deficient region (M2+/2(Fe3+ + Al3+) < 1.0), the sulfide capacity was independent of the basicity of the slags owing to the deficiency of cations required for charge compensation with Al3+ and Fe3+. The cation-substitution effect on the sulfide capacity of the CaO-rich slags (FetO/(FetO + CaO < 0.5) exhibited a linear relationship with the Fe2+ content because Fe2+ had a stronger affinity with S2- compared to that with Ca2+. However, in the FetO-rich slags (FetO/(FetO + CaO > 0.5), the sulfide capacity decreased with the increase of the Fe2+ content owing to the Q(n) unit affinity of the Fe2+ ion. The sulfide capacity was determined by the competition between the Q(n) unit affinity and stability of the S2- ion, depending on the type of cation. Therefore, the partial covalent bonding between the M2+ cations (M: Ca, Fe) and aluminosilicate affected the ionic interactions with the S2- ions. (C) The Minerals, Metals & Materials Society and ASM International 2019.