Preparation of synthetic rutile via selective sulfation of ilmenite with (NH 4 ) 2 SO 4 followed by targeted removal of impurities

Abstract

Abstract This paper describes a novel, facile chemical pathway for preparing synthetic rutile from ilmenite. The pathway consists of two primary units, i.e. , selectively sulfating ilmenite, which was realized via roasting ilmenite with (NH 4 ) 2 SO 4 followed by selective thermal decomposition of the sulfated ilmenite, and targeted leaching of the impurities. The effects of the process parameters were systematically investigated. The results showed that the optimum sulfation conditions were a mass ratio of (NH 4 ) 2 SO 4 to ilmenite of 14, temperature of 360 °C, and time of 120 min with a sulfation ratio of ~ 95%. The optimum thermal decomposition conditions were 480 °C in N 2 atmosphere, and nearly all TiOSO 4 were decomposed with co-decomposition of FeSO 4 of 23%. For acid leaching, the optimum conditions were 2.5 wt% HCl, 98 °C and 120 min. Under those conditions, 94.2% iron was removed with a TiO 2 dissolution loss 2 was removed in 5 wt% NaOH at 102 °C for 1 h. A synthetic rutile with a TiO 2 content > 92 wt% and total MgO + CaO 4 mixed with TiOSO 4 under N 2 was inhibited due to its oxidation to a higher thermal stability Fe 2 (SO 4 ) 3 by oxygen emitted from the decomposition of TiOSO 4 . At the same time, TiOSO 4 decomposition was promoted due to the immediate in situ consumption of oxygen by FeSO 4 . The synergetic effect might be responsible for the enhanced selectivity of sulfated ilmenite thermal decomposition.