The Role of the Hydrate Layer in Nanobubble Stability

The article considers factors determining the stability of a nanobubble with a hydrate layer having a thickness of 1 nm and a dielectric permittivity of about 3. Two stability hypotheses are compared, namely, electrostatic and mechanical (ice-effect or “electrofreezing”). In the first case, the Laplace pressure is compensated by the electrostatic pressure at the bubble boundary; in the second case, it is compensated by the effect of the electrofreezing of its Δ-layer in a high electric field. It is shown that, in salt-free water, a lower nanobubble charge is required for the formation of an ice shell than in the case of the Coulomb stabilization mechanism. In seawater, the Coulomb mechanism is, on the contrary, more efficient, because icing is counteracted by dissolved salt ions. The sizes and charges of the nanobubble are determined for both stability mechanisms.