Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

The surface microbubbles (SMBs) induced by air nucleation on mineral surfaces exert a powerful influence over enhancing the adhesion of air bubbles or oil droplets on mineral surfaces in flotation. The contact angles and TPLs were characterized by captive-bubble/oil droplet on the graphite surfaces. They were combined with dynamic bubble/oil droplet-graphite surface attachment and detachment visualization and force measurements using a microbalance system equipped with a camera to demonstrate the role of SMBs in bubble/oil dropletgraphite surface adhesion. The results show that after depressurization, the dissolved air in water nucleates on both hydrophobic and oxidized graphite surfaces, resulting in SMBs formation, which can enhance the adhesion of bubbles/oil droplets with the different graphite surfaces. For bubble-solid adhesion, these enhancements are attributed to the bridging effect of the SMBs coalescing with the large bubble increasing threephrase contact lines (TPLs) and with this the adhesion forces. For oil-solid interactions, SMBs induce the attachment and spreading of the oil droplet on the graphite surfaces, as the TPLs and spreading forces are increased. SMBs also result in a more stable oil droplet-graphite interface, as the adhesion forces are improved. Therefore, SMBs are efficient for improving graphite flotation by increasing the stability of the mineralized bubble and promoting the spreading and adhesion of dodecane oil. Hence, SMBs coupled with the modification of the surface hydrophobicity may be more beneficial for flotation separation.