Water is the lifeblood of our planet, the engine that fuels the lives of billions of human beings, food production, energy generation, and sustains ecosystems. But its scarcity is an increasingly pressing problem, and with climate change underway, the difficulties in guaranteeing water resources for everyone risk getting worse.
According to UNICEF, almost two-thirds of the world's population faces severe water shortages for at least one month a year. What if there was a way to draw water from nowhere, even in the driest places?
The super-absorbent hydrogel
MIT researchers may have found a nice solution: a super-absorbent hydrogel capable of extracting moisture from the air, even under the most adverse conditions. The secret of the absorbent power of this material is a particular salt, lithium chloride.
"It's the best of both worlds," she says Gustav Graeber, lead author of the study. "Hydrogel can hold a lot of water, and salt can hold a lot of vapor. So it's intuitive that you want to combine the two."
After testing various combinations, the researchers determined that the highly hygroscopic lithium chloride was the best salt to use, being able to absorb more than 10 times its mass in moisture.
The tea(st) desert
The real litmus test for the "salt-charged" hydrogel came when it was tested in various humidity conditions. Under 30%, 50% and 70% RH, the hydrogel absorbed moisture without loss.
Even at 30% relative humidity, lower than humidity in the desert overnight, the hydrogel was able to capture 1,79 grams of water per gram of material, 15% more than previously tested hydrogels. . The collected water can then be heated, condensed and collected as ultrapure water.
The future of the hydrogel
The next challenge for the researchers will be to speed up the water absorption process. “The unexpected big surprise was that, with such a simple approach, we were able to achieve the highest vapor absorption ever recorded,” Graeber said. "Now, the main focus will be on kinetics and how fast we can make the material absorb water."
Due to its rapid production and the possibility of being made on a large scale, as well as an effective water harvesting tool, the hydrogel could have other applications.
"We looked at the material without worrying too much about specific applications, focusing mostly on its fundamental properties," he said Carlos Diaz-Marin, one of the co-authors of the study. 'But now we're exploring very different problems, how to make air conditioning more efficient and how water can be harvested. This material, due to its low cost and high performance, has enormous potential.'
The study was published in the journal Advanced Materials, and I link it here.
