CHEMISTRY AND MINERALOGY OF TITANIA-RICH SLAGS. PART 1—HEMO-ILMENITE, SULPHATE, AND UPGRADED TITANIA SLAGS

Abstract

Titania-rich slags with 80 mass percent TiO2 are produced in the electric arc furnaces of QIT-Fer & Titane, Inc., by the continuous smelting of hemo-ilmenite ore with anthracite coal. Titania slag represents an important feedstock for the manufacture of titanium dioxide pigment by the sulphate process. Moreover, part of the production of the titania-rich slag is further acid-leached under a high-pressure and moderate-temperature hydrometallurgical process to yield an upgraded titania slag with 94.5 mass percent TiO2, which is used in the chloride process. After describing in detail the beneficiation, chemistry, and mineralogy of the hemo-ilmenite ore, this article reviews the unique crystallochemistry and mineralogy of the titanate phases with pseudobrookite-karrooite structure and to a lesser extent silicates and oxides present in these titania-rich feedstocks, focusing on the chemical reactions occurring at each step of the pyro- and hydro-metallurgical processes. The behavior of major elements such as titanium, iron, magnesium, calcium, aluminum, and silicon along with that of minor elements such as vanadium, chromium, and manganese are particularly detailed. A general discussion of the methods specifically developed for the study of the synthetic minerals present in these materials is also presented.