gels

Harvesting Water From The Air | Earth Wise

August 11, 2023 By EarthWise Leave a Comment

Engineers at MIT have created a superabsorbent material that can soak up significant amounts of moisture from the air, even in desert-like conditions.

The material is a transparent, rubbery substance made from hydrogel, which is a naturally absorbent material that is already widely used in disposable diapers. The MIT researchers enhanced the absorbency of hydrogel by infusing it with lithium chloride, which is a type of salt that is a powerful desiccant.

They found that they could infuse hydrogel with more salt than was possible in previous studies. Earlier studies soaked hydrogels in salty water and waited 24 to 48 hours for the salt to infuse into the gels. Not much salt ended up in the gels and the material’s ability to absorb water vapor didn’t change much. In contrast, the MIT researchers let the hydrogels soak up the salt for 30 days and found that far more salt was absorbed into the gel. The result was that the salt-laden gel could then absorb and retain unprecedented amounts of moisture, even under very dry conditions.

Under very dry conditions of 30% relative humidity, the gels captured 1.79 grams of water per gram of material. Deserts at night have those levels of relative humidity, so the material is capable of generating water in the desert.

The new material can be made quickly and at large scale. It could be used as a passive water harvester, particularly in desert and drought-prone regions. It could continuously absorb water vapor from the air which could then be condensed into drinking water. The material could also be used in air conditioners as an energy-saving, dehumidifying element.

**********

Web Links

This salty gel could harvest water from desert air

Photo, posted July 26, 2021, courtesy of Ivan Radic via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Self-Watering Soil | Earth Wise

December 9, 2020 By EarthWise Leave a Comment

Researchers at the University of Texas at Austin have created a new type of soil that can pull water from the air and distribute it to plants. Such soil has the potential to expand the map of farmable land to previously inhospitable places as well as to reduce water use in agriculture in an era of growing droughts.

The team’s atmospheric water irrigation system makes use of super-moisture-absorbent gels to capture water from the air. When they are heated to a high enough temperature, the gels release the water, making it available to plants.

The gels in the soil pull water out of the air during cooler, more humid periods at night and when the sun heats the soil during the day, the water-containing gels release their contents into the soil.

Each gram of soil can extract about 3-4 grams of water. Depending on the specific crop, somewhere between a couple of ounces and 2 pounds of the soil can provide enough water to irrigate a square yard of farmland.

Experiments on the soil found that it retains water better than the sandy soils found in dry areas and needs much less water to grow plants.

In one experiment, radish plants germinated in the soil all survived a 14-day period without any irrigation beyond the initial watering when they were planted. Radish plants in ordinary sandy soil irrigated for the first four days of the experiments lasted no more than two days further without watering.

The Austin group has been developing gel-polymer materials that work like super-sponges for two years. These materials extract large amounts of water from the ambient air, clean it, and release it when heated with solar energy.

**********

Web Links

Self-Watering Soil Could Transform Farming

Photo, posted October 21, 2020, courtesy of the U.S. Department of Agriculture via Flickr. USDA Media by Lance Cheung.

Earth Wise is a production of WAMC Northeast Public Radio.