As the world gets warmer, fresh, clean water is a increasingly sought-after commodity. Agricultural demand, climate change, pollution and other factors are converging to make water scarcity a problem today, and it is likely that get worse in the future.
So how do we handle it? A group of scientists has a suggestion: extract water from the air.
Researchers have developed a super-absorbent gel, made from affordable materials, that can draw moisture from low-humidity air. When heated, the gel releases this moisture as soft water. One kilogram of gel can theoretically produce almost 6 liters of water at 15% relative humidity and more than 13 liters of water at 30% humidity, according to a study published in the journal Nature Communications. For reference, the Southwest Mojave Desert generally spans between 10% and 30% humidity.
“This new work is about practical solutions people can use to get water in the hottest, driest places on earth,” said Guihua Yuone of the researchers, in a Press release. Yu is a materials engineer at the University of Texas at Austin. “It could enable millions of people without constant access to clean water to have simple water-generating devices at home that they can easily operate,” he added in the statement.
The researchers made the gel from a derivative of the compound cellulose (found in all plant cells), a specific fiber extracted from an edible tuber called konjac, and an absorbent lithium chloride salt. The liquid materials were mixed, poured into a mold, left to stand for 2 minutes, and then freeze-dried into a thin sheet. All the materials needed to make 1 kilogram of dried gel would cost less than $2, according to the study.
“The synthesis of this gel is very simple”, Youhong Guoa chemical engineer at MIT and co-author of the study, told Gizmodo. “Which means anyone can do it [easily],” she added.
Once set and dried, the thin sheets of gel became saturated with moisture in about 20 minutes. To extract this water as a drinkable liquid, the researchers then heated the gel in a closed chamber. and collect the condensation. They found that about 70% of the captured water was released within 10 minutes of heating tit freezes at 140 degrees Fahrenheit.
The team tested the gel’s absorbency and water release at different ingredient ratios and different humidities. They also compared the water absorption and water release capacity of the gel with other absorbent materials.
There are a lot of other things out there that pull water from the air. For example, you’ve probably come across these silica packets in snack bags and electronics enclosures.. If you have lived in a humid place, you know that regular table salt absorbs water quite well, too. Heck, fries lose their crispness over time due to absorption of atmospheric water. But this new material is different in several ways.
On the one hand, it absorbs water very efficiently and gets rid of it relatively easily. These same silica packets must be heated to 180 degrees Fahrenheit before they release water, and other desiccants require even higher temperatures. It is also non-toxic and does not add harmful chemicals to collected water. Finally, unlike some other materials, the gel does not appear to degrade with repeated use, the scientists report.
However, as nifty as the gel is (and as useful as it may be in the future), we are a long way from a world where the material magically solves the water crisis.
The researchers ran their tests with mere milligrams of gel and water, then extrapolated those results to kilograms, which might not be a direct translation of reality. It is possible that the ability to absorb and release water will change when the gel is used in larger quantities, explained Ruzhu Wang in an email to Gizmodo. Wang is an engineer at Shanghai Jiao Tong University in China and has worked on similar water harvesting technologies before and was not involved in the new research.
In addition, the scientists worked with very thin films (about 00.01 centimeter thick) of gel in the laboratory. Thin sheets are better for surface exposure, quickly absorbing water and heat quickly to release the water. “But if this water harvesting technology is to be used on a large scale, using such a thin material remarkably increases the overall volume of the device, making it less compact and portable,” Wang said. The researchers propose that their gel could be used in larger blocks. Yet so far they have not tested thadesign.
Even so, Wang still thinks the new results are “encouraging.” He pointed out that the studied gel material is remarkable because of how little energy it takes to produce and use. It is “important to achieve water harvesting in a sustainable and low-carbon way, in terms of material synthesis and energy demand”.
And ultimately, Wang said the new study “brought near-impossible freshwater generation [in] the ultra-dry climate closer to reality. Here it is: science, making the impossible no more possible.