Effect of Organic Compounds and Alkalinity on the Stability of Bulk Nanobubbles: A Molecular Dynamics Study
Kaumbekova S. Ng S. Shah D. Amankeldiyeva A. Omirbekov S. Wang Y.
December 2025Multidisciplinary Digital Publishing Institute (MDPI)
Molecules
2025#30Issue 24
Bulk nanobubbles (NBs) are remarkably long-lived in liquids, yet the molecular mechanisms underpinning their stability remain unresolved. In this work, 50 ns all-atom molecular dynamics simulations were performed to investigate how gas identity (O2, N2, and air with N2:O2 = 4:1), initial gas loading, alkalinity (pH 7 and 13), and organic additives (acetic acid/acetate, ethanol/ethoxide, and hexane) influence the stability of 5 nm NBs in water. Stability was evaluated by the percentage of gas atoms retained in the bubble, density profiles, hydrogen-bond statistics, and radial distribution functions. Higher initial gas density markedly enhanced stability, and N2-NBs consistently outperformed O2-NBs, consistent with the lower solubility of N2. Alkaline conditions exerted only a minor stabilizing effect, most pronounced for air-NBs. Organic additives affected stability according to their hydrophobicity: hydrophobic hexane substantially increased gas retention, especially at low gas loading, by promoting gas clustering and re-adsorption at the NB interface, whereas hydrophilic solutes had negligible influence. RDF analyses revealed that this stabilization correlates with weakened gas–water hydrogen bonding and enhanced gas–gas and gas–hexane interactions. These results elucidate the molecular determinants of NB persistence and offer design guidelines for tuning bubble longevity in environmental and industrial systems.
bulk nanobubbles , gas solubility , hydrophobic effects , intermolecular interactions , molecular dynamics simulations , nanobubble stability , solvent effects
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Center for Energy and Advanced Materials Science, National Laboratory Astana, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana, 010000, Kazakhstan
Shijiazhuang Chang’An Yucai Building Materials Co., Ltd., Shijiazhuang, 051430, China
Department of Chemical and Materials Engineering, School of Engineering and Digital Sciences, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana, 010000, Kazakhstan
Center for Energy and Advanced Materials Science
Shijiazhuang Chang’An Yucai Building Materials Co.
Department of Chemical and Materials Engineering
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