Effect of surface property of main minerals in red mud on their sedimentation ability

The contact angles of glycerol,benzene and diiodomethane on the main minerals in red mud from alumina production were measured,and the corresponding surface free energy values were estimated by Owens two liquids method.And then,the relationship between the sedimentation ability of the minerals and their surfacial properties was discussed.Further,the reason for the sedimentation ability of goethite getting worse after high-pressure treatment was also discussed.The results show that the solvent tendency reduces in the following order: hydration garnet,dicalcium silicate,sodium alumino-silicate hydrate(DSP),calcium titanate,goethite,hematite and limestone,while the sedimentation ability tendency is reverse.Less solvent tendency improves their sedimentation.In addition,the sedimentation ability of fresh hematite deteriorates due to the thinning in grain size and the decrease in solvent tendency when goethite changes into hematite in aluminate solution at high pressure.