Cationic Effect of Ferrous Ions on Sulfide Capacity of CaO-Fe t O-Al 2 O 3 -SiO 2 Slag System

The cationic effect of ferrous ions on the sulfide capacity of CaO-Fe t O-Al 2 O 3 -SiO 2 slags was studied from the viewpoint of the ionic structure in the slag using micro-Raman spectroscopy. In the cation-excess region (M 2+ /2(Fe 3+ + Al 3+ ) > 1.0), the sulfide capacity was directly proportional to the basicity of the slags, owing to the S 2− stabilizing effect of excess cations. However, in the cation-deficient region (M 2+ /2(Fe 3+ + Al 3+ ) < 1.0), the sulfide capacity was independent of the basicity of the slags owing to the deficiency of cations required for charge compensation with Al 3+ and Fe 3+ . The cation-substitution effect on the sulfide capacity of the CaO-rich slags (Fe t O/(Fe t O + CaO < 0.5) exhibited a linear relationship with the Fe 2+ content because Fe 2+ had a stronger affinity with S 2− compared to that with Ca 2+ . However, in the Fe t O-rich slags (Fe t O/(Fe t O + CaO > 0.5), the sulfide capacity decreased with the increase of the Fe 2+ content owing to the Q n unit affinity of the Fe 2+ ion. The sulfide capacity was determined by the competition between the Q n unit affinity and stability of the S 2− ion, depending on the type of cation. Therefore, the partial covalent bonding between the M 2+ cations (M: Ca, Fe) and aluminosilicate affected the ionic interactions with the S 2− ions.