Ambient pressure drying preparation strategy of biomimetic bagasse cellulose aerogel for atmospheric water harvesting

Abstract

Freshwater scarcity has become an urgent global crisis, prompting people to explore atmospheric water as a sustainable resource. Adsorption-based atmospheric water harvesting (SAWH) technology offers a viable solution, but existing adsorbents have limitations such as low efficiency, high energy consumption, and complex preparation processes. Here, we report a cellulose aerogel derived from sugarcane bagasse (LBC/CS-CNT), prepared using an economical and efficient method: ambient pressure drying. The aerogel uses cellulose from sugarcane bagasse and chitosan (CS) from biomass as the skeleton, and glutaraldehyde (GA) as the crosslinking agent, carbon nanotubes (CNTs) as photothermal converters, and lithium chloride (LiCl) as a hygroscopic salt. The LBC/CS-CNT aerogel features an interconnected microporous structure, enabling efficient water vapor transport and storage. It exhibits excellent moisture absorption properties, with a water uptake of 0.90 gwater・g⁻¹sorbent at a relative humidity (RH) of 20% and as high as 5.02 gwater・g⁻¹ sorbent at a 90% RH, outperforming most reported atmospheric water adsorbents. The incorporation of CNTs confers the aerogel with outstanding photothermal conversion efficiency, facilitating rapid desorption under sunlight. Notably, the atmospheric pressure drying process avoids the use of high-energy-consuming equipment, significantly reducing production costs and carbon footprint. The aerogel also exhibits good cycling stability, maintaining high adsorption-desorption performance after 20 cycles. Outdoor tests confirmed its practical applicability: the water uptake rate of aerogel sorbent can reach 1.75 gwater g⁻¹ sorbent.at night, with a water collection efficiency of about 60% during the desorption process during the day. This environmentally friendly, low-cost, and high-performance aerogel offers a sustainable solution for atmospheric water collection, particularly suitable for arid and water-scarce regions.