Bulk Nanobubbles through Gas Supersaturation Originated by Hot and Cold Solvent Mixing

Area of Science:

• Physical Chemistry
• Colloid and Surface Science

Background:

• The nucleation mechanism of bulk nanobubbles is not well understood.
• Existing research has not definitively identified the primary drivers of nanobubble formation.

Purpose of the Study:

• To investigate the role of gas supersaturation in bulk nanobubble nucleation.
• To test the hypothesis that mixing solvents with different gas solubilities induces nanobubble formation.
• To experimentally demonstrate nanobubble nucleation via mixing hot and cold solvents.

Main Methods:

• Extensive experiments on nanobubble nucleation in water and various organic solvents (methanol, ethanol, propanol, butanol).
• Mixing equal proportions of pure solvents with temperature differences ranging from 10 to 80 °C.
• Utilizing Mie scattering theory and refractive index calculations to confirm nanobubble existence.

Main Results:

• Successfully induced bulk nanobubble nucleation by mixing hot and cold solvents, a novel approach.
• Confirmed nanobubble formation through refractive index calculations via Mie scattering.
• Observed experimental verification of the theoretical dependency of critical work for nanobubble formation on gas supersaturation (ΔF_c ∝ 1/ξ² or ΔF_c ∝ ξ¹/⁴).

Conclusions:

• Gas supersaturation is the primary factor in bulk nanobubble nucleation.
• Mixing solvents at different temperatures is a viable method for inducing nanobubble formation.
• The critical work for nanobubble formation is dependent on the interplay between surface tension and surface charge, as influenced by gas supersaturation.