Theoretical model for micro-nano-bubbles mass transfer during contaminant treatment

Micro-nano-bubbles (MNBs), in particular ozone and oxygen MNBs, represent an innovative method for wastewater treatment and groundwater remediation. Although several models have been developed to describe the fate of MNBs in water, a theoretical model describing the mass transfer processes of MNBs during treatment of contaminants has not been adequately developed. In this study, a theoretical model considering the decomposition and reaction of dissolved gas is proposed based on the Epstein and Plesset theory, aiming to describe mass transfer processes of oxygen and ozone MNBs during treatment of contaminants. The life of MNBs, volume-weighted average dissolved gas concentration and utilisation efficiency of gas, which are of significant importance in MNB applications, are further studied. The life of MNBs increases with the half-life of dissolved gas, but the impact diminishes. For gases which present a slow consumption rate and a long half-life, the effect of half-life on the life of MNBs is negligible. With controlled total mass of gas, smaller-sized bubbles result in a significantly higher dissolved gas concentration and more efficient treatment of contaminants. The newly developed model can describe the fate of MNBs during treatment of contaminated water and theoretically proves the advantages of MNBs over large-sized bubbles.