Enhanced flotation selectivity of fine coal from kaolinite by anionic polyacrylamide pre-conditioning

Abstract

The flotation process of fine non-coking coal from kaolinite was enhanced by anionic polyacrylamide. The influence of anionic polyacrylamide on the surface properties of kaolinite and coal was analyzed by Fourier transform infrared spectrometer and contact angle tests. The Derjagin–Landau–Verwey–Overbeek theory was used to analyzed the effect of anionic polyacrylamide on the interaction between various particles. Flocculation behavior of kaolinite and coal particles were visualized through focused beam reflectance measurement and particle video microscope. Field emission scanning electron microscopy was employed to observe the effect of anionic polyacrylamide on the amount of kaolinite coating on clean coal surface. These results demonstrated that anionic polyacrylamide could interact with kaolinite and coal particles by hydrogen bonding. Anionic polyacrylamide could selectively flocculate kaolinite particles rather than coal particles because the repulsion energy between coal particles treated by anionic polyacrylamide was much larger than that between kaolinite particles treated by anionic polyacrylamide. The flotation separation index increased from 182 to 270 when the dosage of anionic polyacrylamide increased from 0 to 66 g/t. In addition, many kaolinite particles were coated on coal surface when anionic polyacrylamide was not added, while there were few kaolinite particles were coated on coal surface when anionic polyacrylamide was added. These results demonstrated that anionic polyacrylamide could not only reduce the kaolinite pollution for froth by selectively flocculation but also decrease the amount of kaolinite particles coating on clean coal surface. Ultimately, the flotation selectivity of fine non-coking coal from kaolinite was enhanced by anionic polyacrylamide pre-conditioning.