Researchers at the University of Texas at Austin have developed a low-cost polymer film made of renewable biomass and hygroscopic salt that can extract atmospheric water in arid environments; these materials cost a mere $2 per kilogram, and a single kilogram can produce more than 6 liters of water per day in areas with less than 15% relative humidity and 13 liters in areas with up to 30% relative humidity.
Atmospheric water harvesting (AWH) technology and design principle of super hygroscopic polymer films (SHPFs): (a) key steps of AWH technology; (b) geographic distribution of world average annual relative humidity; regions with less than 40% relative humidity are indicated from brown to red (warm color) regions; (c) material design of SHPFs for AWH at low relative humidity; (d) qualitative comparison of different materials in terms of core requirements for practical application of AWH. Image credit: Guo et al., doi: 10.1038/s41467-022-30505-2.
“This new work is about practical solutions that people can use to get water in the hottest, driest places on Earth,” said senior author Professor Guihua Yu, a researcher in the Materials Science and Engineering Program and the Walker Department of Mechanical Engineering at the University of Texas at Austin.
“This could allow millions of people without consistent access to drinking water to have simple, water generating devices at home that they can easily operate.”
Professor Yu and colleagues used renewable cellulose and a common kitchen ingredient, konjac gum, as a main hydrophilic skeleton. The open-pore structure of gum speeds the moisture-capturing process.
Another designed component, thermo-responsive cellulose with hydrophobic interaction when heated, helps release the collected water immediately so that overall energy input to produce water is minimized.
Other attempts at pulling water from desert air are typically energy-intensive and do not produce much.
“And although 6 liters does not sound like much, creating thicker films or absorbent beds or arrays with optimization could drastically increase the amount of water they yield,” the researchers said.
“The reaction itself is a simple one, which reduces the challenges of scaling it up and achieving mass usage.”
“This is not something you need an advanced degree to use,” said first author Dr. Youhong ‘Nancy’ Guo, a former doctoral student at the University of Texas at Austin and a postdoctoral researcher at MIT.
“It’s straightforward enough that anyone can make it at home if they have the materials.”
The hygroscopic film is flexible and can be molded into a variety of shapes and sizes, depending on the need of the user.
Making the film requires only the gel precursor, which includes all the relevant ingredients poured into a mold.
“The gel takes 2 minutes to set simply,” said co-author Weixin Guan, a doctoral student in the Materials Science and Engineering Program and the Walker Department of Mechanical Engineering at the University of Texas at Austin.
“Then, it just needs to be freeze-dried, and it can be peeled off the mold and used immediately after that.”
The team’s work was published in the journal Nature Communications.
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Y. Guo et al. 2022. Scalable super hygroscopic polymer films for sustainable moisture harvesting in arid environments. Nat Commun 13, 2761; doi: 10.1038/s41467-022-30505-2
