The role of hydrophobic interaction in the heterocoagulation between coal and quartz particles

The heterocoagulation between the valuable and gangue minerals is an important contamination mechanism of flotation concentrate, which is ubiquitous and undesired in flotation. The classical DLVO theory considering the van der Waals and electrostatic double layer interactions is a valid tool for understanding the mechanism of mineral heterocoagulation in aqueous solution. The hydrophobic interaction is also proved to play a role in the heterocoagulation between hydrophobic particles. However, the effect of hydrophobic interaction on mineral heterocoagulation is short of quantitative characterization. This study investigates the heterocoagulation between coal and quartz particles of different hydrophobicity by a quantitative tool named mineral heterocoagulation quantifying system. The results indicated that the heterocoagulation degree steadily increased with the increase of quartz hydrophobicity. The coal of high hydrophobicity (contact angle 90°) possessed a higher heterocoagulation degree with quartz than the coal of moderate hydrophobicity (contact angle 65°). The extended-DLVO theory was applied to calculate the interaction energy between coal and quartz particles. The calculation results indicated that the hydrophobic interaction dominated the heterocoagulation between coal and quartz particles.