Evaporation of NaCl solution from porous media with mixed wettability

Abstract

Evaporation of saline water from porous media is ubiquitous in many processes including soil salinization, crop production, and CO2 sequestration in deep saline acquirer. It is controlled by the transport properties of porous media, atmospheric conditions, and properties of the evaporating saline solution. In the present study, the effects of mixed wettability conditions on the general dynamics of water evaporation from porous media saturated with NaCl solution were investigated. To do so, we conducted a comprehensive series of evaporation experiments using sand mixtures containing different fractions of hydrophobic grains saturated with NaCl solutions. Our results showed that increasing fraction of hydrophobic grains in the mixed wettability sand pack had minor impact on the evaporative mass losses due to the presence of salt whose precipitation patterns were significantly influenced by the mixed wettability condition. Through macroscale and microscale investigations, we found formation of patchy efflorescence in the case of mixed wettability sand pack as opposed to crusty efflorescence in the case of completely hydrophilic porous media. Furthermore, the presence of salty water and hydrophobic grains in the sand pack significantly influenced the general dynamics and morphology of the receding drying front. Our results extend the understanding of the saline water evaporation from porous media with direct applications to various hydrological and engineering processes.

New insights into saline water evaporation from porous media: Complex interaction between evaporation rates, precipitation, and surface temperature

“…This explains why the measured rates in the early stages of the evaporation process from the sand columns saturated with 0.5, 1.0, 1.5, and 2.5 M are almost the same (because in all cases crust forms at the surface that controls the drying process). This conclusion is in line with the results presented recently by Bergstad and Shokri [2016]. They showed that the evaporative mass losses from porous media saturated with salty solutions with varying wettability conditions were nearly the same regardless of the wettability condition due to the effect of the presence of precipitated salt at the surface.…”

“…Evaporation of saline water from porous media is important in many environmental, engineering, and hydrological processes including vegetation and plant growth, soil salinization, land-atmosphere interaction, functioning of the ecosystem, and crop production [Rodriguez-Navarro and Doehne, 1999;Suweis et al, 2010;Ott et al, 2015;Bergstad and Shokri, 2016]. This has motivated many researchers to investigate various aspects of this process including the effects of grain size, wettability, heterogeneity, and external conditions [Huinink et al, 2002;Guglielmini et al, 2008;Nachshon et al, 2011aNachshon et al, , 2011bEloukabi et al, 2013;Norouzi Rad et al, 2015;Jambhekar et al, 2015;Börnhorst et al, 2016;Dai et al, 2016;Shokri-Kuehni et al, 2017].…”

Drying and percolation in correlated porous media

“…For flows in real systems, such local correlations in material properties can be introduced in many ways. For example, by the roughness typical of a fracture surface [39,40], or by a soil containing grains with a mixture of wettabilities [20,41], or by pore-scale correlations that are present in even relatively uniform sedimentary rock like Berea sandstone [38]. One may expect, therefore, that the types of effects discussed here will apply to just as wide a range of situations.…”

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

“…ambient temperature and relative humidity, wind, solar radiation). This has motivated many researchers to look into the effects of various parameters such as wettability [Sghaier and Prat, 2009;Bergstad and Shokri, 2016], particle size distribution [Eloukabi et al, 2013;Noruzirad et al, 2015], relative humidity [Gupta et al, 2014] and mixture of salt [Jambhekar et al, 2016] on the general dynamics of saline water evaporation from porous media.…”