The effect of mass diffusion on the rate of chemical ice melting using aqueous solutions

Abstract

In wintertime, deicing chemicals are an important tool for keeping roads and runways free from snow and ice. The most common deicing chemical is sodium chloride. However, sodium chloride has a negative impact on the environment, and it is corrosive to vehicles and roadside structures. In addition, sodium chloride has been found to be ineffective at low temperatures. To overcome these issues, there is an ongoing effort to find better deicing chemicals. A part of this effort includes tests of, for example, ice melting performance, such as melting capacity and rate. Although the ice melting capacity is fairly well understood, the melting rate is not. Therefore, an experiment was designed to melt ice using aqueous solutions of nine different chemicals. The purpose was to better understand the underlying mechanisms controlling the ice melting rate. Specifically, we examined the role of diffusive flux on the melting rate of ice. Our results show that for a given chemical, a lower solution freezing point provides a larger driving force for diffusion and results in faster melting. However, the differences between different chemical solutions of the same freezing point were large, and they appeared to be related to the chemical diffusivity in water. The diffusive flux, a combination of driving force and diffusivity, correlated well with the ice melting rate. This indicates that the chemical melting rate of ice was rate-limited by mass diffusion. However, the correlation between diffusive flux and ice melting rate was only present when using notations designed for non-ideal systems. The classic Fick's law could not be related to the ice melting rate. This implied that thermodynamic properties such as chemical potential and activity were better descriptors of concentrated deicing solutions than concentration.