Significance of particle aggregation in the reverse flotation of kaolinite from bauxite ore

• Gibbsite and pyrophyllite face surfaces represent kaolinite basal plane surfaces.
• The wettability of kaolinite surfaces was estimated by contact angle measurements.
• Significant particle aggregation from kaolinite suspension was observed at low pH.
• Cluster formation accounts for the effective flotation of kaolinite from bauxite.

Significant interest has been demonstrated for the removal of kaolinite from bauxite ore by flotation. The reverse flotation of kaolinite from bauxite ore at low pH with dodecylamine hydrochloride collector has been reported. However, resolving the mechanism of the reverse flotation process is largely limited by the misunderstanding of the anisotropic surface properties of kaolinite particles. Based on recent fundamental study of the surface properties of kaolinite particles and their interaction, the significance of particle aggregation in the reverse flotation of kaolinite from bauxite ore has been revealed. The wetting characteristics of the basal plane surfaces of kaolinite with dodecylamine hydrochloride collector have been estimated by contact angle measurements at model surfaces. The improved hydrophobicity of the kaolinite nano-particles is not enough to account for the significant increase in the flotation recovery at low pH when compared to the flotation performance at high pH. Instead, particle aggregation is expected to be the major factor which contributes to the improved flotation response at low pH. Both simulation results and X-ray CT results have demonstrated aggregation and formation of kaolinite clusters at low pH. It appears that these kaolinite clusters have sufficient mass and hydrophobicity to account for the successful reverse flotation of kaolinite from bauxite ore at low pH.