Kinetics of the dissolution of ilmenite in sulfuric acid solutions under reducing conditions

The kinetics of the dissolution of titanium and iron from an ilmenite sample has been studied in moderately strong sulfuric acid solutions in the absence and presence of reducing agents such as titanium(III) ions and sulfur dioxide. The effects of particle size, temperature, solid/liquid ratio, sulfuric acid concentration and titanium(III) concentration on the kinetics of dissolution have been investigated. The results have shown that both particle size and acid concentration have relatively minor effects on the rate of dissolution of titanium while temperature has a significant effect under the studied conditions.The batch leach kinetics of ilmenite in acid solutions appears to fit a shrinking particle model, while in the presence of a decreasing titanium(III) concentration, the rate of dissolution of titanium can be fitted to a shrinking core model. Mathematical expressions for the batch leaching of the ilmenite have been established. The results suggest that the rate of dissolution of ilmenite in acid solutions is controlled by a slow chemical reaction on the surface of the mineral, while in the presence of a reducing agent such as titanous ions, the dissolution rate of ilmenite is significantly enhanced. The use of SO2 as a reductant increases the dissolution of titanium only in the presence of ferrous ions. The role of Ti(III) ions and SO2 during leaching is assumed to involve reduction of the iron(III) component in the mineral by a redox reaction on the surface.