Ionic Effect of NaCl and KCl on the Flotation of Diaspore and Kaolinite Using Sodium Oleate as Collector

The major type of bauxite in China is low-grade diasporic bauxite, which is mainly composed of diaspore and kaolinite. Separation of silicate minerals by flotation technology can meet the requirements of Bayer process, but Na⁺, K⁺ and Cl⁻ deriving from mineral dissolution and entrainment in flotation water will inevitably mix in the flotation slurry, which will affect the flotation of bauxite. The results of flotation show that NaCl and KCl have little effect on the flotation of diaspore, but NaCl has a beneficial effect on kaolinite flotation. It may be attributed to the ion size order Na⁺ < K⁺ < Cl⁻. Na⁺ has the ability to enter the layer spacing of kaolinite due to its smaller size, which increases the zeta potential and the dipole-dipole force between kaolinite and sodium oleate, therefore improving the flotation of kaolinite. In addition, Na⁺ has “salt effect” on the anionic collector, which also promotes the flotation of kaolinite. This study may have some reference significance to the industry flotation of diasporic bauxite.