Nanobubbles from Ethanol‐Water Mixtures: Generation and Solute Effects via Solvent Replacement Method

Abstract

Abstract Replacement of ethanol‐water solutions (70 – 100% v/v) with deionized water was performed in a flow cell of a particle size analyzer. The resulting alcohol solutions were found to contain bulk nanoscale bubbles due to air supersaturation as can be induced by the difference in gas solubility of the solvents. The effect of charged and polar solutes (salt and sugar) that may influence the formation and surface chemistry of nanobubbles was also determined. Dispersion characteristics such as hydrodynamic diameter, particle concentration, along with the particle‘s electrokinetic property were measured all at once using light scattering techniques after solution replacement with and without the solute species. Light scattering results showed that the resulting solutions upon exchange have higher particle quantities than the starting ethanol‐water solvents with smaller diameters ranging from 80 to 160 nm due to nanobubble formation. The claim for air supersaturation forming nanobubbles that may have resulted to the increase in particle density can also be deduced from the obtained optical images in a microscope. The electrokinetic potential or zeta potential was also higher for the solvent exchange protocols entailing for a selective orientation of ethanol molecules in a bubble surface. More importantly, In terms of solute effects, it appears that while salt anions promote gaseous diffusion, sugar molecules inhibit it.