Unraveling the mystery of ultrafine bubbles: Establishment of thermodynamic equilibrium for sub-micron bubbles and its implications

• DOI: 10.1016/j.jcis.2020.02.101
• Publication Date: 2020-02-26T17:01:23Z
• Authors: Euna Kim; Jong Kwon Choe; Byung Hyo Kim; Joodeok Kim; Jungwon Park; Yongju Choi
• Keywords: Suspension

We test the validity of the Young-Laplace equation and Henry's law for sub-micron bubble suspensions, which has long been a questionable issue. Application of the two theories allows characterization of bubble diameter and gas molecule partitioning between gaseous and dissolved phases using two easily measurable variables: total gas content (CT) and bubble volume concentration (BVC).We measure CT and BVC for sub-micron bubble suspensions generated from three pure gases, which allows calculation of bubble diameter for each suspension using the Young-Laplace equation and Henry's law. Uncertainties involved in the experimental measurements are assessed. Bubble size for each suspension is also directly measured using a dynamic light scattering (DLS) technique for comparison.Applying the two theories we calculate that the bubble diameters are in the range of 304-518 nm, which correspond very well with the DLS-measured diameters. Sensitivity analyses demonstrate that the correspondence of the calculated and DLS-measured bubble diameters should take place only if the two theories are valid. The gas molecule partitioning analysis shows that >96% of gas molecules in the suspension exist as dissolved phase, which suggests the significance of the dissolved phase for applications of the bubble suspensions.