Effect of ionic environment in aqueous solution on nucleation and stabilization of bulk nanobubbles

Abstract

Bulk nanobubbles have attracted significant interest due to their growing demand for widespread applications. A thorough comprehension of the essential factors dictating nanobubble properties holds immense significance in industrial practices. This study endeavors to examine the characteristics of bulk nanobubbles formed in a complex ionic solution containing surfactants and sodium chloride. The experimental findings demonstrate that both ionic and nonionic surfactants can effectively promote the nucleation of nanobubbles. The introduction of salts has an opposing effect as it reduces both the number concentration and the Zeta potential of nanobubbles. There is a concentration threshold for NaCl above which the nanobubble properties are significantly affected. The salt effectively promotes the adsorption of surfactant ions, which in turn leads to a decrease in interfacial tension. The Zeta potential of nanobubbles is established through the competing interactions between the surface adsorption and ion shielding effect. Subsequently, the critical stable conditions for nanobubbles generated in solutions containing surfactants and salts are calculated, while considering both the kinetic stability of nanobubble populations and the thermodynamic stability of individual nanobubbles. These findings offer valuable insights into the intricate influence of complex aqueous ionic environment on nanobubbles, thereby setting the stage for the deliberate manipulation of them.