Abstract: Red mud is a tailing produced during alumina smelting of bauxite, in which the content of free alkali and structural alkali is high. Titanium white waste acid is the acid waste liquid produced during the production of titanium white powder by vanadium-titanium magnetite, which contains a large amount of sulfuric acid. According to the strong basicity of red mud and the acidity of titanium dioxide waste acid, the dealkalization from red mud by leaching with titanium white waste acid was put forward. The effect of stirring rate, liquid to solid ratio, leaching temperature and leaching time on dealkalization rate were investigated. Furthermore, the theoretical analysis and leaching kinetics of the process of red mud demineralization were studied with X-ray diffraction (XRD) and the unreacted shrinking core model (USCM). The results show that the dealkalization rate of red mud is higher than 99% and the pH value of the leaching solution is 6.2 under the conditions of leaching temperature of 70 ℃, stirring rate 400 r/min, liquid to solid ratio 5 mL/g and reaction time 60 min. The leaching process of red mud with titanium white waste acid not only achieves the high demineralization rate, but also enriches the iron grade in the demineralization residue, which is used as a secondary mineral resource for extraction and recovery of iron. The titanium white waste acid significantly destroies the crystal structure of cancrinite in the red mud, which results in complete dissolution of the alkali. The diffraction peaks of anhydrite and hematite are obvious in the demineralization residue according to the analysis of XRD. The leaching process is controlled by the internal diffusion by the analysis of leaching kinetics, and the linear correlation coefficient is more than 0.99. The rate constant increases with the increase of temperature and the apparent activation energy (E_a) is 13.12 kJ/mol.

Key words: dealkalization, kinetics, apparent activation energy, leaching, red mud, titanium dioxide waste acid