The solid-liquid separation behaviors of the typical leach slurries in the alkaline processes for alumina

The filtration kinetics and the cake properties of the alumina leach slurry were investigated. Four kinds of alumina leach slurry were prepared by the hydro-chemical process to treat the bauxite, the Bayer process, the Bayer process with less lime, and the hydro-chemical process to treat the Bayer red mud. The filtration kinetics was regressed by filtration test method at constant pressure. The diversity of the solid-liquid separation behaviors indicates that the digestion conditions play an important role in the filtration process. The composition and phase, the size distribution, the shape and the surface properties of the solid particles as well as the viscosity of filtrate were measured, and their effects on the filtration resistance and the cake compressibility were confirmed. Results indicate that the fine size and the broad size distribution of the particles lead to a high cake resistance. And the substances containing Fe or Ti exhibit a noticeable influence on the cake characteristics. Methods of filtration optimization through changing digestion conditions were recommended.