Harvesting environmental water by hydroscopic hydrogels embedded in delinquent salt and ‎carbon nanotube

N. Hamidi
South Carolina State University,
United States

Keywords: hygroscopic hydrogels, atmospheric water generation (AWG), ‎freshwater,, thermoresponsive polymers


Recent innovative activities such as industrial, agricultural, rural developments, and ‎defense ‎endeavors require fresh water, and its resources are depleting quickly. The proposed ‎solution for ‎this problem is harvesting water from the air. The estimated amount of renewable ‎water in ‎Earth’s atmosphere reaches 12.4 trillion tons of vapor distributed worldwide with ‎fast ‎replenishment. The vapor could be harvested as freshwater by emerging technology ‎everywhere, ‎including arid regions, land-locked areas, and remote communities. Materials that ‎absorb fast ‎vapor at room temperature and release it as a liquid at a slightly higher temperature ‎are the critical ‎components for atmospheric water harvesting. One of the promising materials is the ‎flexible ‎hybrid photothermal water sorbents composed of hygroscopic salt and hydrogel that ‎possesses ‎superior water sorption capacity even in low-humidity air. In these devices, the ‎deliquescent salt, ‎adsorbed to the hydrogel body, maintains its solid form after a significant amount of water ‎is ‎condensed in the structure. The condensed water could be released at temperatures below the ‎‎boiling point of water (70 to 90 °C), a temperature that is achievable under sunlight via the ‎‎photothermal effect. A sample of hygroscopic hydrogel with the embedded carbon nanotube was ‎‎fabricated and tested under laboratory conditions. It absorbed up to 60% of its weight ‎water and ‎its maximum rate of water release was within 70 to 90 °C, a temperature achievable ‎under direct ‎sunshine. Environmental harvesting water devices made of these materials could become a ‎complemental ‎resource to reduce freshwater stresses. ‎