Bulk Nanobubbles from Acoustically Cavitated Aqueous Organic Solvent Mixtures

Area of Science:

• Colloid and Surface Science
• Physical Chemistry
• Nanotechnology

Background:

• Bulk nanobubbles are nanoscale gas bubbles in liquids.
• Their stability is crucial for applications in various fields.
• Understanding their behavior in mixed solvents is essential.

Purpose of the Study:

• To investigate the existence and stability of bulk nanobubbles in aqueous organic solvent mixtures.
• To characterize nanobubble properties like size distribution, number density, and zeta potential.
• To elucidate the mechanisms governing nanobubble stability in different solvent compositions.

Main Methods:

• Generation of bulk nanobubbles using acoustic cavitation.
• Characterization of nanobubble suspensions (size, number density, zeta potential).
• Long-term monitoring of nanobubble stability over months.

Main Results:

• Bulk nanobubbles exist in pure water but not in pure organic solvents.
• Nanobubbles disappear at certain organic solvent-water ratios.
• Stability in aqueous mixtures is influenced by solvent adsorption and hydrogen bonding.
• Mean bubble size increases and surface tension decreases with solvent content.

Conclusions:

• Nanobubble stability in pure water is attributed to surface charge from hydroxyl ions.
• Lack of autoionization in organic solvents prevents nanobubble existence.
• Preferential adsorption of solvent molecules and hydrogen bonding stabilize nanobubbles in mixtures.
• Observed behavior contrasts with macro/microbubbles in surfactant solutions.