Improvement on combustible matter recovery in coal slime flotation with the addition of sodium silicate

The influence of an inorganic salt dispersant, sodium silicate (SS), on the removal of minerals in coal slime flotation was investigated. XRD, contact angle measurements, zeta potential measurements and EDLVO calculations were employed to reveal the interactions between SS and coal slime. The flotation experiments indicated that the combustible matter recovery of clean coal could be increased by 10.9 % with the addition of 1200 g/t SS. The reasons of SS on facilitating the separation of the combustible components from coal slime were governed by two factors, decreasing the hydrophobicity of minerals and enhancing particle dispersion, both of which are beneficial to the coal flotation. Furthermore, it was found that the effect of SS on decreasing the hydrophobicity of minerals was mainly attributed to the surface modification on kaolinite. It was concluded that SS could significantly improve the flotation recovery of coal slime especially under the condition of a high content of kaolinite in coal slime.