Efficient separation of fine coal assisted by surface nanobubbles

The separation performance of fine particles by flotation is significantly sensitive to particle size, which poses a limit to application of flotation in the separation of fine particles. In the present work an effective method that employs nanobubbles was investigated for the separation of fine coal. Nanobubbles were produced with the method of temperature change. Applying a series of techniques including atomic force microscopy (AFM), rheological measurement, the visualization of particle-bubble interaction and flotation test, it was found that surface nanobubbles are present on highly oriented pyrolytic graphite (HOPG) surface. Coal agglomeration occurred in the presence of nanobubbles, which was indicated by the shear thinning of coal slurry. Furthermore in an adhesion test, more coal particles attached to a bubble in the presence of nanobubbles, which suggested a positive effect of nanobubbles on the particle-bubble interaction. Thus, it could be concluded that, nanobubbles are responsible for the improved flotation performance of coal particles.