Deliquescent salts have high water vapor adsorption capacity, but they dissolve in water by forming crystalline hydrates which restricts their use in different applications. However, this limitation can be overcome by incorporating deliquescent salts within a polymer matrix, which will keep the salt solution in place without allowing them to come out of the matrix. Furthermore, if the polymer matrix used its-self is capable of adsorbing water vapor that will further improve the overall performance of the desiccant. Therefore, in this work, we are proposing the synthesis and use of a highly effective new solid polymer desiccant material, i.e. superporous hydrogel (SPHs) of poly(sodium acrylate-co-acrylic acid (poly(SA-co-AA)), and subsequently its composite with deliquescent salt, i.e. calcium chloride (CaCl~2~), to adsorb water vapor from humid air without the dissolution of CaCl~2~ salt in adsorbed water. Parental PAA-SPHs matrix alone exhibited an adsorption capacity of 1.02 g~w~/g~ads~ which increased to 3.35 g~w~/g~ads~ after incorporating CaCl~2~ salt in the polymer matrix. Both materials exhibited type-III adsorption isotherm and the experimental isotherm data was fitted to the Guggenheim, Anderson and Boer (GAB) isotherm model. However, the adsorption kinetics followed linear driving force model which suggested that this extremely high adsorption capacity was due to the diffusion of water molecules into the interconnected pores of SPHs via capillary channels followed by the attachment of adsorbed water molecules to the CaCl~2~ salt present in the polymer matrix. Furthermore, the adsorbents were used successively for six cycles of adsorption with a very little loss in adsorption capacity. Therefore, the polymer desiccant material reported here overcomes the problem of dissolution of deliquescent salts and purposes a new class of highly effective solid desiccant material to be use in different water vapor adsorption applications.    


Adsorption Isotherm and Kinetics of Water Vapor Adsorption Using Novel Super-Porous Hydrogel Composites

Division / Sponsor:
Advanced Energy Systems Division (AESD) & Solar Energy Division (SED)

Paper Proceedings: https://asmedigitalcollection.asme.org/ES/ES2020/volume/83631

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