Surface nanobubble characterization and its enhancement mechanisms for fine-particle flotation: A review

Froth flotation is often used for fine-particle separation, but its process efficiency rapidly decreases with decreasing particle size. The efficient separation of ultrafine particles (UFPs) has been a major challenge in the mineral processing field for many years. In recent years, the use of surface nanobubbles in the flotation process has been recognized as an effective approach for enhancing the recovery of UFPs. Compared with traditional macrobubbles, nanobubbles possess unique surface and bulk characteristics, and their effects on the UFP flotation behavior have been a topic of intensive research. This review article is focused on the studies on various unique characteristics of nanobubbles and their mechanisms of enhancing the UFP flotation. The purpose of this article is to summarize the major achievements on the two topics and pinpoint future research needs for a better understanding of the fundamentals of surface nanobubble flotation and developing more feasible and efficient processes for fine and UFPs.