A review and perspective on micro and nanobubbles: What They Are and Why They Matter

Over the past two decades, there has been a rapid growth in the research and extraordinary applications of micro and nanobubbles due to their unique physicochemical properties beyond conventional bubbles including large specific surface area, slow rising velocity, high interface potential, high mass transfer efficiency, and so on. Although there were considerable excellent results and findings reported, a remarkable lag is still recorded concerning the detailed explanation of their formation principle, generating methods and special physicochemical properties. Simultaneously, limited efforts have been made on collecting and preparing a well-organized, comprehensive report of their potential applications in the areas of flotation science and technology. This review is dedicated to a systematic description on their generating principle, fabricating methods, special physicochemical properties and state-of-the-art characterization technologies based on up-to-date research progresses. Subsequently, the main applications of micro and nanobubbles in typical flotation processes with a special emphasis on mineral & secondary resource processing, environment & water treatment, separation & purification for metals were comprehensively reviewed and thoroughly discussed. Ultimately, the challenges and limitations of the current research field including the opportunities for future work of micro and nanobubbles were prospected. Oily-bubble floating-extraction, as the 3th generation foam extraction technology, were also proposed to enhance mass transfer. In summary, this review may be helpful to improve the overall understanding on Micro and Nanobubbles: What They Are and Why They matter.