Researchers in China have demonstrated a graphene nanocomposite foam-based water harvesting system to harvest water from the earth atmosphere (air.)
“The team reports their findings in ACS Applied Materials & Interfaces (“Superelastic Graphene Nanocomposite for High Cycle-Stability Water Capture-Release under Sunlight”).
Only 30% of all freshwater on the planet is not locked up in ice caps or glaciers (not for much longer, though). Of that, some 20% is in areas too remote for humans to access and of the remaining 80% about three-quarters comes at the wrong time and place – in monsoons and floods – and is not always captured for use by people. The remainder is less than 0.08 of 1% of the total water on the planet (read more: “Nanotechnology and water treatment“)
An abundance of water equivalent to about 10% of the total freshwater in lakes exists in the earth atmosphere, which can be a non-negligible freshwater resource to fight against the water shortage.That’s where the graphene nanocomposite foam comes in: The foam realises water harvesting through a capture-release cycle:
1) the capture process is composed of moisture adsorption from air by lithium chloride (LiCl) and water preservation by poly(vinyl alcohol) (PVA) and
2) the release relies on the solar-to-thermal transformer, reduced graphene oxide (rGO), to facilitate evaporation. In addition, polyimide is employed as a substrate material for the purpose of 3D porous structure formation and mechanical property enhancement.”…
“The as-fabricated foam can adsorb water up to 2.87 g per gram in 24 hours at a relative humidity of 90% and a temperature of 30°C, and release almost all the uptake water when it is exposed under a flux of 1 sun (1000 W per square meter, equal to the light intensity of natural sunlight) for 3 hours.
At the same time, the functional foam shows superelasticity, lightweight, and remarkable reusability, thus revealing its possibility to practical use.
The researchers write that, even though the rGO/PI nanocomposite foam can harvest freshwater from air, it is essential to enhance water harvesting efficiency.”
Read full article Graphene foam material harvests water from air
Image: (g) Schematic diagram of the water vapor capture-release cycle. LiCl and PVA were responsible for the water capture and water storage, respectively.