Sun and a sponge: the formula that transforms salt water into drinkable water without electricity

Scientists have developed a porous, sponge-like material that, when heated by sunlight, converts seawater into freshwater without using electricity. The system was tested outdoors and was able to efficiently generate drinking water, paving the way for a sustainable form of desalination.

Most of the planet's water is found in the oceans, but their high salt content makes it unfit for human consumption. Current desalination plants can purify it, but they require complex infrastructure and high energy consumption. In response, researchers at the Hong Kong Polytechnic University proposed a more accessible and environmentally friendly approach: using the sun and a 3D-printed spongy material.

The device is made from a mixture of carbon nanotubes and cellulose fibers, printed in layers on a frozen surface. This creates a rigid, porous structure with very fine vertical channels. Unlike other materials, this one maintains its effectiveness even when enlarged.

In the outdoor test, the scientists placed the sponge in a glass of seawater, covering it with a transparent plastic dome. Sunlight heated the aerogel, which evaporated the water (leaving the salt behind). The condensed steam collected on the lid and dripped into a funnel, collecting clean water at the base. In just six hours, the system produced about 45 milliliters of drinking water.

According to the researchers, this method could offer a simple alternative for communities without access to electricity or expensive infrastructure. “Our aerogel enables full-capacity desalination at any size,” said Xi Shen, one of the authors of the study published in ACS Energy Letters .