TY - JOUR
TI - Bulk nanobubbles: Production and investigation of their formation/stability mechanism
AU - Michailidi, E.D.
AU - Bomis, G.
AU - Varoutoglou, A.
AU - Kyzas, G.Z.
AU - Mitrikas, G.
AU - Mitropoulos, A.C.
AU - Efthimiadou, E.K.
AU - Favvas, E.P.
JO - Journal of Colloid and Interface Science
PY - 2020
VL - 564
TODO - null
SP - 371-380
PB - Academic Press Inc.
SN - 0021-9797, 1095-7103
TODO - 10.1016/j.jcis.2019.12.093
TODO - Free radicals;  Hydrogen bonds;  Paramagnetic resonance;  Phase interfaces;  Physicochemical properties;  Sodium chloride;  Stability;  Water absorption, Bulk solutions;  Electron paramagnetic resonance spectroscopy;  Hydrogen bonding interactions;  Ions distribution;  Nanobubbles;  Narrow size distributions;  Negative surface charges;  Stable systems, Electron spin resonance spectroscopy
TODO - Nanobubbles (ΝΒs) have attracted concentrated scientific attention due to their unique physicochemical properties and large number of potential applications. In this study, a novel nanobubble generator with low energy demand, operating continuously, is presented. Air and oxygen bulk nanobubbles (NBs@air and NBs@O2) with narrow size distribution and outstanding stability were prepared in water solution. The bulk NBs’ behavior was evaluated taking into consideration the hydrodynamic diameter and ζ-potential as a function of processing time, gas type, pH value and NaCl concentration. According to the results the optimum processing time was 30 min, whereas the effect of water salinity was stronger in NBs@O2 than NBs@air. In order to investigate further the NBs properties, Electron Paramagnetic Resonance (EPR) spectroscopy was applied for quantitative analysis of free radicals following the spin trapping methodology. The mechanism of bulk NBs’ generation and their extremely long-time stability can be attributed mainly to the hydrogen bonding interactions. The formation of a diffusion layer, by absorption of OH− due to electrostatic interaction, contributing to negative surface charge, whereas the interaction of ions with the surface hydroxylic groups provide the equilibrium between the protonation and deprotonation of water and finally the formation of a stable interface layer. A remarkable highlight of this work is the long-time stability of generated bulk NBs which is up to three months. © 2019 Elsevier Inc.
ER -