Revealing the influence of porosity and temperature on transport properties of nanobubble solution with molecular dynamics simulations

Viscosity reduction and diffusivity increase of aqueous solution is of great importance in many fluid-related industrial processes. To achieve the purpose in environment-friendly and cost-effective way, nanobubbles (NBs) are introduced into solutions but the mechanism is not yet fully understandable. In this work, we investigate the viscosity and diffusivity of NB-containing aqueous solutions by using molecular dynamics (MD) simulations with SPC/E water model. We make molecular modeling of NB solutions with porosities ranging from 0 to 34.21% and perform MD simulations to determine the viscosity and self-diffusion coefficients as increasing temperature from 273 to 373 K. Our calculations reveal that the viscosity of NB solutions is significantly reduced as increasing the porosity and temperature following the Arrhenius equation. On the contrary, the self-diffusion coefficient of NB aqueous solution with different porosities is found to considerably increase with temperature according to the Arrhenius equation. However, the effect of porosity on the diffusivity is negligible and deviated from the Stokes–Einstein equation possible due to hard hydrogen bonds formed on the liquid–air interface of NBs. With these findings, this work will contribute to extending the usability of NB to the practical applications.