Micro-macrobubbles interactions and its application in flotation technology for the recovery of high density oil from contaminated sands

The integration of microbubbles (Sauter diameter: 80 μm) and macrobubbles (Sauter diameter: 0.9 mm) in a flotation system were proposed to enhance oil removal efficiencies. The role of the microbubbles as a secondary collector for macrobubbles was studied in the static bubble interaction studies in terms of attachment time, contact angle and visualization of contact area. Results showed that the presence of microbubbles could decrease the attachment time between macrobubbles and oil layer by 82%, and improve the contact angle and surface area of attachment by 40.3% and 54.5% respectively. Macrobubbles, on the other hand were able to improve the floatability of oil contaminant as suggested from the dynamic bubble interaction study. The presence of macrobubbles was able to increase the volumetric rate of micro-macrobubbles captured from 0.47 μL/s to 4.5 μL/s. The results demonstrated that the coalescence phenomena between bubbles could provide the necessary lifting force to further aid the oil flotation. The interaction between microbubbles and macrobubbles is particularly advantageous in an integrated bubble flotation system. Application of the integrated micro-macrobubbles demonstrated a significant increase in oil removal to 68.6% under oil-wet conditions while almost all of the oil contaminants were removed from water-wet sands. An increase of 28% was observed upon implementation of integrated micro-macrobubble flotation compared to the single bubble flotation for oil removal. Results indicated that the integration of microbubbles and macrobubbles in the flotation cell is a simple modification to a flotation system that would enhance the removal of oil contaminant from contaminated sand.