Solar-responsive biopolymer–carbon nanotubes aerogel for efficient atmospheric water harvesting

Freshwater scarcity is an escalating global challenge that necessitates innovative and sustainable water supply solutions. In this study, a novel gum Arabic-alginate-carboxylated carbon nanotubes (GAC) aerogel composite was developed for atmospheric water harvesting (AWH) across a broad range of relative humid conditions. The aerogel combines a biopolymeric double-network framework with hygroscopic CaCl₂ and LiCl salts, while carboxylated carbon nanotubes (CNTs–COOH) act as photothermal agents to enhance solar-driven desorption. The GAC aerogel achieved water sorption capacities of 7 g/g at 90 % RH and 1.2 g/g at 20 % RH (25 °C). Under simulated solar irradiation (0.8 SUN, 800 W/m²), the aerogel exhibited an equilibrium surface temperature of 65 °C and released 94.7 % of captured water within 6 h. The material achieved stable performance over ten adsorption–desorption cycles (~3 cycles/day) without degradation. Structural and physicochemical analyses (FTIR, XRD, Raman, SEM, TGA, and UV–vis-NIR) confirmed the aerogel's chemical structure, macroporous morphology and photo absorption efficiency. These results establish GAC as a highly effective and sustainable sorbent for scalable atmospheric water generation, offering significant potential for deployment in arid and water-stressed regions.