1 Cent Per Litre: Stanford Develops Durable Hydrogel That Harvests Drinking Water From Air

 

Atmospheric water generators use hydrogels, made of salt and absorbent polymers, to draw moisture from the atmosphere and convert it into drinking water. However, these materials degrade too quickly, reducing their cost-effectiveness. Now, researchers from Stanford University have developed a way to harvest water from air using solar power and a new hydrogel that lasts for eight months or more. Carlos Diaz-Marin, an assistant professor of energy science and engineering in the Stanford Doerr School of Sustainability and co-lead author of the research, believes that their work could potentially provide a way to access additional water resources to help people who don't have access to water or have to walk hundreds of hours per year to procure water.

 

The professor also highlights the increased importance of atmospheric water generation technology as industries like semiconductor manufacturing and data centres continue to put more pressure on water systems. Published in Nature Communications, the research claims that the new hydrogels can produce potable water in really extreme conditions as well. Building upon their earlier work, the researchers investigated how the hydrogel breaks down and found that problems arise from the gel's contact with a metal surface, which releases ions that form radicals in the hydrogel and attack the polymer's long chains, even though the metal casing is key to powering the water-harvesting process with heat from the sun. The gel's contact with the metal turned it into goo as bits of polymer leached into the water. Researchers are developing low-cost hydrogels that can harvest drinking water from the air. Here, energy science and engineering Assistant Professor Carlos Diaz-Marin (left) and graduate student Garin Gross (right) use a machine to measure how well various salts capture water, a key step in the process “The radicals are very efficient at eating the polymer away,” said Diaz-Marin.

 

“To our knowledge, nobody had thought of durability and degradation of these materials, despite it being a critical parameter for water production.” The researchers tested interventions to block the metal ions, and an anti-corrosion coating on the metal solved the problem, extending the hydrogel’s lifespan dramatically. In one test, the hydrogel remained stable for more than eight months while kept at 167 degrees Fahrenheit, a temperature meant to stress-test the material under extreme conditions. The researchers also found the hydrogel on coated metal remained stable for more than 190 water-harvesting cycles. Diaz-Marin said that this level of durability advanced the hydrogel toward producing water at a competitive cost and could lead to a point where water is produced at around one cent per litre. "This would be about 1 per cent of the cost of bottled water and about 10 times the rate US households pay for tap water. We see a path to this technology to perhaps even being competitive with tap water," he said.