Fluorination of titanomagnetite concentrate with ammonium bifluoride

Abstract

Objectives. To study the technological features of a new fluoride technology for the production of titanium dioxide by the decomposition of titanomagnetite concentrate with ammonium fluorides.Methods. The chemical species of the titanium and iron components in the fluorination of titanomagnetite concentrate and sublimation separation of components were determined by means of X-ray powder diffraction analysis and inductively coupled plasma mass spectrometry. The kinetics of sublimation of the titanium component by the thermal decomposition of ammonium hexafluorotitanate was experimentally studied.Results. The products of the fluorination of titanomagnetite concentrate with ammonium bifluoride are compounds (NH4)2TiF6 and (NH4)3FeF6, as proven by chemical analysis and X-ray powder diffraction analysis. The subsequent sublimation separation of the titanium component produced the target product: a mixture of ammonium fluorotitanates. The desublimation of the titanium-containing fraction gave an NH4TiF5–(NH4)2TiF6–(NH4)3TiF7 mixture, the titanium content of which is 30.6% and the content of impurities (Fe, V, Si) is a minimum (0.45%). The activation energy of the heterogeneous reaction and the rate-limiting step of the process were also determined.Conclusions. A high-purity titanium product (a mixture of ammonium fluorotitanates) is obtained. This is a valuable commercial product for the industrial production of titanium dioxide pigment from titanomagnetite concentrate and ilmenite.