Modifying water sorption properties with polymer additives for atmospheric water harvesting applications

Solar-Sorbent based Atmospheric Water Harvesting (AWH) systems are supposed to be a promising key to address the growing concern over global water scarcity. However, it is hard to find a sorbent with all of the necessary characteristics such as high sorption capacity, low regeneration temperature, low corrosion risk, and low cost. Here, we fabricated composites by combining silica gel, salt, and polymers that show faster dynamic, improved regeneration properties and sorption capacity. Adding Polyvinylpyrrolidone (PVP) to silica gel-LiCl composite not only significantly decreases water hold-up in the regeneration process by 35-55%, but also it can increase the sorption capacity. These stable materials also demonstrate higher water harvesting capacities, which makes them proper sorbents in sorption-based technologies. The silica gel-LiCl-PVP capability to be used in a real AWH system is tested in a small prototype and this material could deliver about 0.43 g water per g sorbent. The quality of collected water can meet the global drinking water regulation. The findings also show a good perspective of using these materials in existing systems without any significant costs or modifications. These will reduce the regeneration temperature and consequently the energy consumption will decrease.