Oily-bubble and its typical applications in enhancing the separation and mass transfer processes: A review and perspectives

Oily-bubbles have significant advantages including a greater contact area, stronger selectivity and higher mass transfer rate compared to bubbles, which exhibit excellent industrial prospects in mineral processing, extraction metallurgy, wastewater treatment and other fields. In recent decades, extensive research has been conducted on the enhancement of separation and mass transfer processes by oily-bubbles. Although considerable excellent results and findings have been reported, a remarkable lag is still recorded concerning the detailed explanation of their formation principle, fabrication methods and typical applications. Hence, the overarching aim of this study is to conduct a comprehensive review and provide a perspective on oily-bubbles. The generation principle and fabrication methods of oily-bubbles were comprehensively summarized based on up-to-date research progress. Subsequently, the significant role of oily-bubbles in enhancing separation and mass transfer processes, with a special emphasis on mineral and secondary resource processing, as well as in the separation and purification of metals, was thoroughly evaluated. Most importantly, the technical challenges, existing problems, and future directions of research on oily-bubbles are highlighted. In summary, this review may be helpful for improving the overall understanding of oily-bubbles and their typical applications in enhancing separation and mass transfer processes.