Ammonium fluoride roasting and water leaching of leucoxene concentrates to produce a high grade titanium dioxide resource (of the Yaregskoye deposit, Timan, Russia)

Abstract

Ammonium hydrofluoride was used for fluorination of titanium-silica-containing raw materials (by the example of quartz-leucoxene concentrate of Yaregskoye deposit, South Timan, Russia). The optimum physical and chemical conditions for the processing of quartz-leucoxene concentrates, which allow obtaining a high‑titanium product containing >85% TiO2 in a mixture of rutile and anatase at relatively low temperatures and a short processing time (300°С for 2 h), are presented. The results of thermodynamic calculations on interaction of NH4HF2 with the components of the leucoxene concentrate were checked in experiments. The main phases formed during the interaction of NH4HF2 with the two components of the leucoxene concentrate have been determined by thermal and X-ray phase analysis methods. The rate of fluorination depending on the amount of ammonium hydrofluoride and the influence of mechanical activation of mineral raw materials was studied. Optimal ratio is SiO2:NH4HF2 = 1:4. Material grinding leads to its activation and intermediate products ((NH4)3TiF7, (NH4)2SiF6)) are formed at lower temperatures. This will reduce the consumption of fluorinating component and allow to obtain a high‑titanium product with minimal costs.