Sugarcane bagasse derived composite sorbent for sorption based atmospheric water harvesting

The escalating global concern surrounding water scarcity is significantly impacting the quality of life, particularly in arid and land-locked regions. Sorption-based atmospheric water harvesting (AWH), employing a sorbent to capture atmospheric moisture, emerges as a sustainable solution to mitigate the global water crisis. However, developing efficient, eco-friendly, easily synthesised, and cost-effective sorbents poses a challenge. Herein, an efficient composite sorbent derived from waste sugarcane bagasse-based activated carbon (SBAC), impregnated with a low-cost hygroscopic CaCl₂ salt, has been prepared. The composite SBAC/CaCl₂ showed good performance across a wide working range between 10–90 % relative humidity, with water uptake ranging from 0.24 to 2.44 g/g. At moderate temperature and humidity (25 °C, 60 % RH), SBAC/CaCl₂ exhibited a water uptake of 1.2 g/g and achieved over 80 % of its equilibrium water uptake within 90 min. Also, the sorbent showed excellent solar driven desorption with desorption efficiencies reaching over 93 % and 85 % for 1 sun and 0.5 sun illumination, respectively, within 60 min. The sorption kinetics and adsorption isotherm showed excellent fit with the linear driving force model and Dubinin Astakhov isotherm model. The practical solar-driven atmospheric water harvesting performance of the SBAC/CaCl₂ composite was also successfully demonstrated using a custom-built device under outdoor conditions and the harvested water met the quality standards of drinking water. Furthermore, the prepared sorbent exhibited cyclic stability and storage reliability with no performance degradation even after repeated cycles. This work highlights the significant potential of waste biomass derived sorbents for sustainable AWH applications.