Razi University

  AbstractThe development of Atmospheric Water Harvesting (AWH) technologies is crucial for arid and semi-arid regions. Composite sorbents combining a porous host matrix with a hygroscopic salt offer high efficiency at low relative humidity and low energy consumption. This study aimed to design and synthesize an affordable and high-capacity activated carbon/calcium chloride ($CaCl_2$) composite for industrial applications.First, three activated carbon samples (coarse granular, powdered, and medium granular) were evaluated using structural and thermal analyses. The medium granular sample (Sample 18) was selected as the optimal host matrix due to its high specific surface area ($454.13\\text{ m}^2/\\text{g}$) and superior adsorption performance. Second, fifteen composite samples were synthesized via the impregnation method using varying $CaCl_2$ concentrations (30–50%) and residence times (24–72 hours).Comprehensive characterization identified Sample 13 (prepared with a 40% $CaCl_2$ concentration and a 72-hour impregnation time) as the optimal sorbent, achieving an ideal balance between high moisture adsorption capacity and physical stability (avoiding deliquescence). Kinetic evaluations revealed that Sample 13 exhibited a significantly enhanced adsorption capacity—increasing from 0.214 to $GFN2252_LABSTRACT_XMLENCODE#.286\\text{ g/g}$ over three successive cycles—with a 95% desorption recovery rate, vastly outperforming raw activated carbon. Given its low-cost materials and excellent performance at low relative humidity, the Sample 13 composite is a highly efficient and economical solution for AWH in arid regions.Keywords: Atmospheric Water Harvesting, Activated Carbon, Calcium Chloride, Composite Sorbent, Impregnation, Moisture Adsorption