Adsorption isotherm and kinetics of water vapors on novel superporous hydrogel composites

A promising and highly efficient new solid desiccant material composted of superporous hydrogel (SPHs) of polyacrylamide (PAM) and AQSOA-Z02 zeolite was fabricated to capture water vapor from moist air. The synthesis method of PAM-SPHs involved the gas blowing and foaming technique which insured a uniform distribution of zeolite particles throughout the polymer matrix. The presence of three dimensional porous structure, interconnected macropores in SPHs and the highly hydrophilic functional groups of AQSOA-Z02 particles enabled the synthesized SPHs composite to exhibit excellent water vapor adsorption capacity. The introduction of AQSOA-Z02 zeolite in the polymer matrix increased the water vapor adsorption capacity from 0.77 g_w/g_ads to 0.89 g_w/g_ads. Both materials exhibited type-III isotherm and followed Frenkel-Halsey-Hill and Guggenheim, Anderson and Boer (GAB) adsorption isotherm models. The high adsorption capacity was attributed to the combined effects of capillary condensation in interconnected macropores and the attachment of water molecules to the hydrophilic functional groups present in the zeolite structure. The water vapor adsorption capacity was found to decrease with increasing temperature. Adsorption kinetics studies suggested that the water vapor adsorption followed first-order kinetics models and the mechanism of water molecules diffusion into the internal structure of SPHs was case-II type of diffusion mechanism.