Sublimation rate of solid NaCl powders and evaporation rate of liquid NaCl upon heating in vacuum and air

•The volatilization of NaCl has great potential for separation and purification.•The sublimation of NaCl is much faster than the evaporation after melting.•The NaCl powder hardly sublimates upon heating in the air before melting.•Only a part of the NaCl powder bed participates in sublimation.•The Hertz-Knudsen relation reflects the volatilization kinetics of NaCl powders. The volatilization of sodium chloride (NaCl) is important for multiple applications, such as energy storage, manufacturing porous parts, and purification and recycling of composites. Until now, only limited information on this feature has been published. To expand the knowledge in this field, we investigated the sublimation and evaporation of two NaCl powders by thermal gravimetry in vacuum and air. The study has shown that the volatilization kinetics of powders with different shapes and sizes are identical. The volatilization of NaCl powders in vacuum occurs mainly by sublimation before melting. In contrast, the volatilization of NaCl in the air is preferentially caused by the evaporation of the melt. In a vacuum, the evaporation of NaCl powder after melting is significantly slower than the sublimation before melting, because of a drastic decrease in the volatilization area. The Hertz-Knudsen relation with an appropriate fitting coefficient satisfactorily describes the mass loss by volatilization in vacuum and air. [Display omitted]