Interface Effects of Micro/nanobubbles Enable Selective Photooxidation of Contaminants

Micro/nanobubbles (MNBs), due to their unique interface properties, have demonstrated remarkable potential in enhancing advanced oxidation processes (AOPs) in water. These gas-liquid interfaces enhance oxidation efficiency by facilitating oxidant mass transfer and contaminants adsorption. While the role of interface reactions is well-documented, the influence of MNBs-induced effects on contaminant removal mechanisms in aqueous phase reactions remains inadequately understood. To bridge this knowledge gap, an oxygen MNBs/ultraviolet/hydrogen peroxide (O-MNBs/UV/H₂O₂) photooxidation system was developed to explore the role of interface effects in aqueous phase reactions. Model contaminants, including representative natural and synthetic organic compounds commonly found in surface waters, were selected to evaluate the removal performance. The results indicated that the removal efficiency of contaminants was significantly influenced by the electrostatic and hydrophobic properties of the contaminants. Notably, the O-MNBs enhanced activation of H₂O₂ by improving UV-light utilization and oxygen mass-transfer efficiency, leading to increased production of reactive oxygen species (ROS) in the aqueous phase. Meanwhile, surface repulsion induced by electrostatic and hydrophobic forces facilitated the migration of contaminants into the aqueous phase, thereby enhancing their contact with ROS and enabling selective oxidation. These findings reveal that MNB-mediated interface effects can drive the spatial redistribution of contaminants and modulate their oxidation pathways in photooxidation, offering a promising strategy for controlling oxidation reactions and achieving selective removal of contaminants in water treatment applications.