Long-term stability of different kinds of gas nanobubbles in deionized and salt water

Yali Zhou, Zhenyao Han, Chunlin He, Qin Feng, Kaituo Wang, Youbin Wang, Nengneng Luo, Gjergj Dodbiba, Yuezhou Wei, Akira Otsuki, Toyohisa Fujita

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Nanobubbles have many potential applications depending on their types. The long-term stability of different gas nanobubbles is necessary to be studied considering their applications. In the present study, five kinds of nanobubbles (N2, O2, Ar + 8%H2, air and CO2) in deionized water and a salt aqueous solution were prepared by the hydrodynamic cavitation method. The mean size and zeta potential of the nanobubbles were measured by a light scattering system, while the pH and Eh of the nanobubble suspensions were measured as a function of time. The nanobubble stability was predicted and discussed by the total potential energies between two bubbles by the extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The nanobubbles, except CO2, in deionized water showed a long-term stability for 60 days, while they were not stable in the 1 mM (milli mol/L) salt aqueous solution. During the 60 days, the bubble size gradually increased and decreased in deionized water. This size change was discussed by the Ostwald ripening effect coupled with the bubble interaction evaluated by the extended DLVO theory. On the other hand, CO2 nanobubbles in deionized water were not stable and disappeared after 5 days, while the CO2 nanobubbles in 1 mM of NaCl and CaCl2 aqueous solution became stable for 2 weeks. The floating and disappearing phenomena of nanobubbles were estimated and discussed by calculating the relationship between the terminal velocity of the floating bubble and bubble size.

Original languageEnglish
Article number1808
JournalMaterials
Volume14
Issue number7
DOIs
StatePublished - 1 Apr 2021
Externally publishedYes

Keywords

  • Extended DLVO theory
  • Mean size
  • Ostwald ripening effect
  • Stokes equation
  • Zeta potential

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