A cheap hydrogel that can suck moisture out of the air and then release it on demand might be the answer to drinking water shortages in arid regions.
Researchers from the King Abdullah University of Science and Technology (KAUST) suggest an inexpensive hydrogel-based material they have developed can suck water from the air, even in low humidity conditions and release the water back out when warmed by sunlight.
There are many areas around the globe that are affected by a lack of access to clean water. The earth’s air is a possibly untapped resource for clean water.
Cheap stable salt at the centre of a device
It is estimated that the Earth's air contains more than 13 trillion tonnes of potable water. However, research into extracting this water in the past has proved to be expensive and inefficient.
But that might be about to change, a prototype developed by Peng Wang from the Water Desalination and Reuse Center at Kaust has shown the potential to overcome this problem inexpensively and reliably.
The device is based around the cheap, stable, nontoxic salt, calcium chloride.
Hydrogel absorbs while staying solid
This salt has the ability to absorb so much vapor from its environment it will become a pool of liquid.
“The deliquescent salt can dissolve itself by absorbing moisture from air,” says Renyuan Li, a Ph.D. student in Wang’s team.
While the salt has the impressive ability to absorb water from the air, the fact it turns it into salty water is less useful. To beat the problem, the researchers incorporated the salt into a polymer known as a hydrogel.
Carbon nanotubes allow water extraction via sunlight
This material can absorb a lot of water while remaining solid. A small amount of carbon nanotubes were also added to the mix that will assist the captured water vapor to be released.
Just 0.42 percent by weight were added, but the material impressive ability to absorb sunlight and convert the captured energy into heat is essential to extracting the liquid.
A simple 35-gram prototype of the completed extraction device was left outside and managed to collect 37 g of water in weather conditions of 60 percent humidity.
Researchers work to scale up a prototype
The following day, after absorbing sunlight for just 2.5 hours almost all of the absorbed water was released and collected.
“The hydrogel’s most notable aspects are its high performance and low cost,” says Li.
The researchers say that if the prototype was scaled up to produce 3 liters of water per day, an amount considered the minimum water requirement for an adult, the cost of the gel could be as low as half a cent per day.
The research was published in the recent edition of Environmental Science and Technology.