Effects of salinity and temperature on the icing of sessile saltwater droplets on solid surfaces

The icing of sessile seawater droplets on solid surfaces holds significant importance in scientific research and freeze desalination technology. Nevertheless, the statistical characteristics and underlying mechanisms of this phenomenon remain insufficiently understood. In this study, we experimentally investigate the statistical characteristics of the icing of seawater droplets on solid surfaces, and couple with the molecular dynamics method to reveal the influence of salinity and substrate temperature on the icing. It is found that the nucleation time of seawater droplets on solid surfaces exhibits stochasticity, while it follows a normal distribution. With increasing salinity or surface temperature, the distribution range of the nucleation time becomes broader and more dispersed. Both the average nucleation time and the average freezing time of seawater droplets increase with increasing salinity or temperature; the former is due to an elevating nucleation energy barrier, and the latter stems from an increasing ice-salt solution interfacial free energy (the energy required to freeze the salt solution into a unit area of ice). Our findings enhance the comprehension of the characteristics and fundamental mechanisms of the icing of seawater droplets on solid surfaces, offering valuable insights for the development of freeze desalination technology.