Abstract:The reaction mechanism of red mud residue leached by sulfuric acid was discussed in detail. With reference to grain model, the acid leaching process could be divided into three stages, i.e. chemical reaction control stage, porosity control stage and mass transfer control stage. Analysis was conducted on the above three stages by experiments. The effects of acid leaching temperature and time, vitriol concentration, and ratio of liquid to solid (L/S) on leaching rate of titanium dioxide were investigated with orthogonal test. The optimum leaching conditions including acid leaching temperature of 150 ℃, vitriol concentration of 9 mol/L, leaching time of 2 h and L/S of 6∶1. Under the above mentioned conditions, the leaching rate of titanium dioxide reaches 95.2%.