A Hydroxypropyl Cellulose-Enhanced Acrylamide-Based Hygroscopic Hydrogel for Efficient Atmospheric Water Harvesting

Water shortages in distant and dry areas require sustainable measures. An alternative composite hydrogel, which is extremely effective in solar-powered atmospheric water harvesting, is proposed in this research. Its synthesis was performed using radial polymerization. Based on polyacrylamide (PAM), hydroxypropyl cellulose (HPC) was incorporated to increase hydrophilicity. Lithium chloride (LiCl) was used as a humectant, and carboxylated carbon nanotubes (CNT-COOH) were used as photothermal nanofillers. The formulation of the optimized hydrogel (PAM-HPC0.3-CNT3.5-LiCl25) shows a high capacity of water absorption of 2.52 g g–1 at 90% RH and 25 °C and has the ability to achieve 90% saturation in 2 h at 40% RH. The hydrogel surface temperature under exposure to simulated sunlight (1.0 kW m–2) is 48.4 °C and allows desorbing approximately 96% of water in 10 h. It is also shown that the material has good cyclic stability after 10 adsorption–desorption cycles. Experimental testing outdoors proves its technical feasibility to collect atmospheric water on natural light. This paper offers a promising and energy-saving approach to materials to harvest water in areas with plentiful sunlight.