Kinetics of the leaching of TiO2 from Ti-bearing blast furnace slag

Ti-bearing blast furnace slag is a valuable secondary resource containing about 24 percent of TiO₂. In this paper a process of leaching Ti-bearing blast furnace slag with sulfuric acid to recover TiO₂, and the kinetics of that reaction, are described. Under laboratory conditions the rate is controlled by a chemical reaction. The leaching reaction is in accord with a shrinking unreacted-core model. The apparent reaction order of the leaching reaction was 1.222 and the apparent activation energy was 87.01 kJ/mol. The model fits the observed data well until 90% of the TiO₂ has be leached from the particles. The model disagrees with observations during later periods of the reaction because the solution becomes supersaturated with Ti ions, which precipitate as H₂TiO₄. The assumptions of constant reactant concentration and that there is no effect from the product layer on diffusion, also cause the model to deviate from the actual values.