Role of Mutual Diffusion in the Dissolution Behavior of One Primary Bulk Gas Nanobubble in Liquid: A Molecular Dynamics Study

Abstract

Dissolution of one primary bulk gas nanobubble in an undersaturated liquid constitutes one of the underlying issues of the exceptional stability of bulk gas nanobubble population. In this paper, the mutual diffusion coefficient at the gas−liquid interface of one primary bulk gas nanobubble is investigated via all-atom molecular dynamics simulation, and the applicability of the Epstein−Plesset theory is verified. The mutual diffusion coefficient, different from the self-diffusion coefficient in bulk gas or bulk liquid, is essentially determined by the chemical potential due to its driving role in the mass transfer across the interface. We could ascribe the low-rate dissolution of one primary bulk gas nanobubble in an undersaturated liquid to the slight attenuation of the mutual diffusion coefficient at the interface. The results show that the dissolution process of one primary bulk gas nanobubble in an undersaturated liquid fundamentally obeys the Epstein−Plesset theory and that the macroscopic dissolution rate is intrinsically determined by the gas mutual diffusion coefficient at the interface rather than the self-diffusion coefficient in the bulk phase. The mass transfer viewpoint from the present study might actively promote subsequent studies on the super-stability of bulk gas nanobubble population in liquid.

Micronanobubble Aeration Enhances Plant Yield and Nitrification in Aquaponic Systems

“…This observation suggests that the NBs generated in this experiment can maintain their negative charge and concentration through changes in pH, especially within the operation range of aquaponics . Moreover, as shown in other studies, the intricate diffusion process associated with MNB solutions points toward a slow and complex diffusion process. , …”

“…42 Moreover, as shown in other studies, the intricate diffusion process associated with MNB solutions points toward a slow and complex diffusion process. 43,44 Despite theories 45 suggesting rapid dissolution of NBs in solution, given their highly dense gaseous structure and high internal pressure (50-fold greater than atmospheric pressure), 46 the NB residence times contradict this expectation. Several hypotheses have proposed that the negatively charged gas−liquid interface introduces a counteracting force against the surface tension, slowing or preventing bubble dissipation.…”