New Inexpensive Hydrogel-Based Material Capture Its Own Weight In Water

As the race to create sustainable water, countries around the world are looking closely on how to capture water. Saudi Arabia has become the latest country to create a device that can capture its own weight in water from fresh air.

King Abdullah University Of Science & Technology (Kaust) researchers have create an inexpensive hydrogel-based material that efficiently captures moisture even from low-humidity air that released it on demand. This simple device can capture its own weight in water from fresh air, when warmed by sunlight. This stunning discovery could provide secure new resource of drinking water in remote arid regions.

Earth’s air contains almost 13 trillion tons of water, it is a vast untapped reservoir of clean drinking water. Researchers around the worlds have tried to develop devices using different materials to tap into that water resource. The results of the previous researches have proven to be too inefficient, expensive or complex for practical use. A prototype developed by Peng Wang from the Water Desalination and Reuse Center and his team could finally changed that.

At the center of that device is the cheap but stable nontoxic calcium chloride salt. This deliquescent salt has such a great affinity for water that it will absorb much vapor from the surrounding air that eventually forms a pool of liquid, says Renyuan Li, a Ph.D. student in Wang’s team. “The deliquescent salt can dissolve itself by absorbing moisture from air”.

Calcium chloride has great water-harvesting potential, but the fact it turns from a solid to a salty liquid after absorbing water has been a major hurdle for its use as water capture device, says Li. Systems that use liquid sorbents are very complicated. To overcome the problem, the researchers incorporated the salt into a polymer called a hydrogel, that can hold a large volume of water while remaining as solid. They also added a small amount of carbon nanotubes, 0.42/% by weight, to ensure the captured water could be released. Carbon nanotubes very efficiently absorb sunlight and convert the capture energy into heat.

The team incorporated 35 grams of this material into a simple prototype device. Left outside overnight, it captured 37 grams of while the humidity level was 60%. The following day after 2.5 hours of natural sunlight irradiation, most of the water was released and collected inside the device.

“The hydrogel’s most notable aspects are its high-performance ad low-cost” per Li. If the prototype scaled up to produce 3 liter of water per day, the cost of the hydrogel would be as low as half a cent per day.

The next step for the researchers Is to fine tune the hydrogel so that it released the water continuously rather than in batches.

As climate change is affecting everyone at the global stage, we are looking at what countries are doing to remedy the lack of water. With this latest finding, we could see the potential could benefit.