Mechanochemical reaction between sulfur and ilmenite

An ilmenite (FeTiO₃) concentrate has been milled with sulfur in a laboratory-scale ball mill for 100 h under a variety of conditions. X-Ray diffraction and thermal processing have shown that reaction occurs within the mill forming pyrite (FeS₂) and rutile (TiO₂). The reaction was of greatest extent in a mill run under 400 kPa of inert gas; some reaction occurred in a mill under 10^-2 Pa, whereas little reaction was observed when either water or air was present. Annealing of the product powders showed that reaction to TiO₂ and FeS₂ could be achieved in a closed system after 1 h at 400°C but with the evolution of SO₂, whereas annealing at 800°C also gave TiO₂ and FeS₂, but without formation of SO₂ which was thought to have disproportionated to form iron sulfate(VI). Closed-tube annealing of unmilled sulfur and milled ilmenite showed the same reactions as milled powders but of much greater extent.