Size-dependent coalescence of nanobubbles in pure water

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 688; p. 133530
• Main Authors: Niwano, Michio, Ma, Teng, Tadaki, Daisuke, Iwata, Kazuki, Kimura, Yasuo, Hirano-Iwata, Ayumi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.05.2024
• Subjects: Nanobubble; Nanobubble lifetime; Nanoparticle trajectory analysis; Size distribution; Size-dependent coalescence; Size-dependent coalescence; Size distribution; Nanoparticle trajectory analysis; NTA; Nanobubble; NBs; Nanobubble lifetime
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2024.133530

Previously, we experimentally demonstrated that similar-sized bulk nanobubbles (NBs) preferentially coalesce when the NB size is ∼100 nm. To explain this peculiar NB coalescence phenomenon, we performed a nanoparticle trajectory analysis to determine the size distribution profile and time-dependent concentration of the bulk NBs generated by pressurizing a porous alumina thin film with ordered straight nanoholes. Furthermore, we propose a physical model based on the hypothesis that the repulsive energy increases when two NBs establish contact, and that coalescence occurs when the kinetic energy of the NBs overcomes the repulsive energy. We simulated the observed NB-size distribution by using the proposed model. The simulation results explained the observed NB-size distribution and lifetime of the NBs. They further indicated that NB coalescence was suppressed for small NBs with diameters of approximately 100 nm or less, resulting in their long lifetimes. [Display omitted] •Similar-sized bulk nanobubbles (NBs) preferentially coalesce for small NBs.•A physical model was proposed in which the repulsive energy increases when two NBs establish contact.•The simulation based on the model explained the size distribution and lifetime of the NBs.•NB coalescence was suppressed for small NBs, resulting in their long lifetimes.