Passive Atmospheric Water Harvesting: Kinetics and Thermodynamics of Vapor Uptake in Acrylamide‐Based Composites

ABSTRACT Studies on Atmospheric Water Generators (AWGs) are significant as they address the challenge of supplying freshwater from non‐conventional resources, helping to mitigate the worldwide water stress. Acrylamide composites are among the most suitable and appealing materials for passive AWGs, utilizing natural forces to harvest and release environmental water. This work presents the kinetics of steam absorption for a sample of an acrylamide composite, prepared by radical polymerization of acrylamide and N, N'‐methylene‐bis‐acrylamide in the presence of potassium persulfate, calcium chloride, and activated carbon powder (CDAG). The thermally sensitive CDAG absorbs vapor quickly and releases water by the CDAG phase transition mechanism caused by radiation energy. Its vapor uptake properties were studied at room temperature and pressure under six partial pressures of vapor, ranging from 7 to 31 kPa. The kinetics of vapor uptake were evaluated according to the Langmuir and Michaelis–Menten laws, and the isoconversional method. Steam absorption followed a first‐order mechanism, with a heat release that varied with the extent of vapor uptake by the gel, ranging from 250 to 270 kJ/mol −1 . This variation was attributed to the stepwise hydration of CaCl 2 and the amide groups.