  Understanding the behavior of nanobubbles (NBs) in various aqueous solutions
is a challenging task. The present work investigates the effects of various
surfactants (i.e., anionic, cationic, and nonionic) and pH medium on bulk NBs
formation, size, concentration, bubble size distribution (BSD), zeta potential,
and stability. The effect of surfactant was investigated at various
concentrations above and below critical micelle concentrations. NBs were
created in DI water using a piezoelectric transducer. The stability of NBs was
assessed by tracking the change in size and concentration over time. NBs size
is small in the neutral medium compared to the other surfactant or pH mediums.
The size, concentration, BSD, and stability of NBs are strongly influenced by
the zeta potential rather than the solution medium. BSD curve shifts to lower
bubble sizes when the magnitude of zeta potential is high in any solution. NBs
were observed to exist for a long time, either in pure water, surfactant, or pH
solutions. The longevity of NBs is shortened in environments with pH less than
3. Surfactant adsorption on the NBs surface increases with surfactant
concentration up to a certain limit, beyond which it declines considerably. The
Derjaguin-LandauVerwey-Overbeek (DLVO) theory was used to interpret the NBs
stability, which resulted in a total potential energy barrier that is positive
and greater than 43.90kBT for pH ranging from 6.0 to 11.0, whereas, for pH
below 6, the potential energy barrier essentially vanishes. Moreover, an effort
has also been made to elucidate the plausible prospect of ion distribution and
its alignment surrounding NBs in cationic and anionic surfactants. The present
research will extend the in-depth investigation of NBs for industrial
applications involving NBs.
