Utilization of ferrous leach liquor to synthesize gamma ferric oxide

Abstract

The production of pigment grade titanium dioxide involves leaching of ilmenite with acids that also results in the formation of ferrous sulfate/chloride. Usually the ferrous salts are spray‐roasted to regenerate the sulfuric acid/hydrochloric acid for recycling. However, the quantities of ferrous leach liquor and the capital cost of the regeneration plant dictate the viability of regeneration of acids. In the case of smaller ilmenite processing plants, the regeneration of the acid is not economical and warrants alternate methods of using the ferrous leach liquor. The present paper describes a novel method of synthesizing gamma ferric oxide from ferrous leach liquor obtained from a titanium dioxide pigment plant situated in south India. The partial precipitation technique is employed to purify the ferrous leach liquor and make it suitable for the synthesis. Sodium carbonate is used to precipitate iron as ferrous carbonate and is directly calcined to yield gamma ferric oxide. Experiments were conducted to study the effect of heating rate, condition of the precipitate, whether dry or wet, and extent of oxidation of ferrous on the magnetic properties such as coercivity and specific magnetization. Cobalt‐doped gamma ferric oxide was also prepared by the carbonate precipitation route.