Ammonium hydroxide decomposition of ilmenite slag

Ammonium hydroxide decomposition of ilmenite slag was studied as part of an improved process to obtain high purity titanium oxide. The kinetics of the decomposition reaction was investigated in terms of the slag particle size, NH4OH concentration, NH4OH/slag mass ratio and reaction temperature. It was found that digestion of the ground ilmenite slag in 4 M NH4OH at a temperature of 150 °C decomposed the slag with the formation of ammonium titanate ((NH4)2TiO3) which was readily hydrolyzed in hot water to high purity anatase (≥ 99.8% TiO2). Analysis of the decomposition reaction kinetics found that the reaction was chemically controlled with an apparent activation energy of 27.8 ± 1.6 kJ mol− 1. Based on the experimental results, a flow sheet was developed and tested.