(225r) Influence of Hydroscopic Salt Species on the Performance of Hierarchical Silica-Salt Composites for Atmospheric Water Harvesting

Freshwater water scarcity is one of the greatest humanitarian challenges and continues to be a growing issue due to population growth, climate shifts and socio-economic changes. Atmospheric water harvesting, especially in remote, arid or underdeveloped areas, is a potential solution to provide a renewable source of water that can meet the current and future water consumption demands. Hierarchical silica absorbents has recently received significant interest as a promising technology for water harvesting. The water-stability and pore characteristics of these silica compounds result in improved water uptake compared to strictly-microporous sorbents as well as at higher % relative humidity (%RH) compared to pure hygroscopic salts. Incorporating hygroscopic salts into hierarchical mesoporous silica have been shown to enhance low %RH water adsorption while maintaining its absorbent properties at high %RH. Previous works were focused on impregnating the silica with LiCl at various salt solution concentrations. In this work, the synthesis, characterization and water adsorption results of different silica-salt sorbents are presented. Four different hydroscopic salt compounds (lithium chloride, calcium chloride, magnesium chloride and sodium carbonate) were selected and incorporated into the hierarchical silica using the incipient wetness impregnation method. The water uptake performance of the tested silica-salt composites were compared to determine the optimal salt loading and salt species choice.