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This sun-powered sponge pulls drinking water straight from the ocean

Date:
July 3, 2025
Source:
American Chemical Society
Summary:
In a leap toward sustainable desalination, researchers have created a solar-powered sponge-like aerogel that turns seawater into drinkable water using just sunlight and a plastic cover. Unlike previous materials, this new 3D-printed aerogel maintains its efficiency at larger sizes, solving a key scalability issue. In outdoor tests, it produced clean water directly from the ocean without any electricity, pointing to a future of low-cost, energy-free freshwater production.
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Most of Earth's water is in the oceans and too salty to drink. Desalination plants can make seawater drinkable, but they require large amounts of energy. Now, researchers reporting in ACS Energy Letters have developed a sponge-like material with long, microscopic air pockets that uses sunlight and a simple plastic cover to turn saltwater into freshwater. A proof-of-concept test outdoors successfully produced potable water in natural sunlight in a step toward low-energy, sustainable desalination.

This isn't the first time scientists have created spongy materials that use sunlight as a sustainable energy source for cleaning or desalinating water. For example, a loofah-inspired hydrogel with polymers inside its pores was tested on chromium-contaminated water and, when heated by the sun, the hydrogel quickly released a collectible, clean water vapor through evaporation. But while hydrogels are squishy and liquid-filled, aerogels are more rigid, containing solid pores that can transport liquid water or water vapor. Aerogels have been tested as a means of desalination, but they are limited by their evaporation performance, which declines as the size of the material increases. So, Xi Shen and colleagues wanted to design a porous desalination aerogel that maintained its efficiency at different sizes.

The researchers made a paste containing carbon nanotubes and cellulose nanofibers and then 3D-printed it onto a frozen surface, allowing each layer to solidify before the next was added. This process formed a sponge-like material with evenly distributed tiny vertical holes, each around 20 micrometers wide. They tested square pieces of the material, ranging in size from 0.4 inches wide (1 centimeter) to about 3 inches wide (8 centimeters), and found that the larger pieces released water through evaporation at rates as efficient as the smaller ones.

In an outdoor test, the researchers placed the material in a cup containing seawater, and it was covered by a curved, transparent plastic cover. Sunlight heated the top of the spongy material, evaporating just the water, not the salt, into water vapor. The vapor collected on the plastic cover as liquid, moving the now clean water to the edges, where it dripped into a funnel and container below the cup. After 6 hours in natural sunlight, the system generated about 3 tablespoons of potable water.

"Our aerogel allows full-capacity desalination at any size," Shen says, "which provides a simple, scalable solution for energy-free desalination to produce clean water."

The authors acknowledge funding from the National Natural Science Foundation of China, the Research Grants Council of Hong Kong SAR, the Environment and Conservation Fund of Hong Kong SAR, and the Hong Kong Polytechnic University.


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Materials provided by American Chemical Society. Note: Content may be edited for style and length.


Journal Reference:

  1. Xiaomeng Zhao, Yunfei Yang, Xuemin Yin, Zhuo Luo, Kit-Ying Chan, Xi Shen. Size-Insensitive Vapor Diffusion Enabled by Additive Freeze-Printed Aerogels for Scalable Desalination. ACS Energy Letters, 2025; 3419 DOI: 10.1021/acsenergylett.5c01233

Cite This Page:

American Chemical Society. "This sun-powered sponge pulls drinking water straight from the ocean." ScienceDaily. ScienceDaily, 3 July 2025. <www.sciencedaily.com/releases/2025/07/250702214145.htm>.
American Chemical Society. (2025, July 3). This sun-powered sponge pulls drinking water straight from the ocean. ScienceDaily. Retrieved July 3, 2025 from www.sciencedaily.com/releases/2025/07/250702214145.htm
American Chemical Society. "This sun-powered sponge pulls drinking water straight from the ocean." ScienceDaily. www.sciencedaily.com/releases/2025/07/250702214145.htm (accessed July 3, 2025).

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