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Chinese Journal of Chemical Engineering, Vol.25, No.6, 821-828, 2017
Preparation of synthetic rutile via selective sulfation of ilmenite with (NH4)(2)SO4 followed by targeted removal of impurities
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 (NH4)(2)SO4 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 (NH4)(2)SO4 to ilmenite of 14, temperature of 360 degrees C, and time of 120 min with a sulfation ratio of similar to 95%. The optimum thermal decomposition conditions were 480 degrees C in N-2 atmosphere, and nearly all TiOSO4 were decomposed with co-decomposition of FeSO4 of 23%. For acid leaching, the optimum conditions were 2.5 wt% HCl, 98 degrees C and 120 min. Under those conditions, 94.2% iron was removed with a TiO2 dissolution loss b1%. For alkali leaching, 67% SiO2 was removed in 5 wt% NaOH at 102 degrees C for 1 h. A synthetic rutile with a TiO2 content N92 wt% and total MgO + CaO <1.5 wt% was obtained. Based on these results, a schematic flowsheet was proposed. Additionally, it was found that the decomposition of FeSO4 mixed with TiOSO4 under N-2 was inhibited due to its oxidation to a higher thermal stability Fe-2(SO4)(3) by oxygen emitted from the decomposition of TiOSO4. At the same time, TiOSO4 decomposition was promoted due to the immediate in situ consumption of oxygen by FeSO4. The synergetic effect might be responsible for the enhanced selectivity of sulfated ilmenite thermal decomposition. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.