Impact of type of salt and ambient conditions on saline water evaporation from porous media

Abstract

Saline water evaporation from porous media is important in many processes such as soil salinization, CO2 sequestration, crop production and water management. This process is influenced by the transport properties of porous media, properties of the evaporating solution and external conditions. In this work, we investigated the effects of external conditions and type of salt on the drying behaviour of sandy media and on the dynamics of surface salt precipitation. To do so, a comprehensive series of evaporation experiments were conducted using 33 columns packed with sand saturated with salt solutions. The evaporation experiments were conducted in an environmental chamber to investigate the effects of relative humidity, ambient temperature and type of salt on the evaporation process. Sodium Chloride, Calcium Chloride and Potassium Iodide with a wide range of concentration were used to saturate the sand columns mounted on digital balances. A digital camera was fixed at the surface of the sand packs to record the dynamics of salt precipitation at the surface. The results provide further confirmation that ambient conditions are the controlling factors during stage-1 evaporation of pure water. Additionally, the minor impact of the presence of precipitated salt at the surface on the saline water evaporation during the early stages of the process is discussed. Strong correlations between the cumulative water losses and the precipitation at the surface were found under different ambient conditions. The results obtained from different types of salt highlight the significant influence of the relationship between the saturated vapour pressure and salt concentration on the general dynamics of the process.