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

N. Hamidi, I. Williams, H. Hamidi, M. McKinney, E. Smalls, P.‎D. Ferguson
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 ‎a fast refill. ‎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 critical 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 its ‎structure. The condensed water could be released at temperatures below the ‎boiling point of ‎water (35 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 ‎water release rate 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.‎