Investigation of surfactant effect on ozone bubble motion and mass transfer characteristics

The low solubility and low mass transfer efficiency of ozone (O3) in water are important reasons for limiting the application of ozone oxidation technology and advanced ozone oxidation technology. Low-dose surfactants were introduced to affect the behavior of ozone bubbles, influencing the ozone mass transfer efficiency. The motion of ozone bubbles in three different types of surfactant solutions (polyoxyethylene lauryl ether (Brij35), sodium dodecylsulfate (SDS), and cetyltrimethylammonium bromide (CTAB)) was observed. The decrease in surface tension led to a decrease in bubble size, a tendency to spherical shape, an increase in gas content and residence time, a decrease in lateral displacement of a single bubble, and a more stable trajectory. The effect of surfactants on ozone mass transfer was further investigated. The addition of surfactant was found to increase the gas-liquid interface area but decrease the liquid phase mass transfer coefficient, and the extent of the two opposite effects varied for different surfactants. The analysis combined with the removal of pollutant p-Nitrophenol (PNP) showed that the addition of the nonionic surfactant Brij35 and the anionic surfactant SDS inhibited ozone mass transfer, while low concentrations of the cationic surfactant CTAB enhanced ozone mass transfer. When the CTAB concentration was 3 mg L−1, the ozone volume mass transfer coefficient reached a maximum of 0.2902 min−1.