This gel can draw water out of the air, even in the middle of the desert

This gel, which is able to extract water from the atmosphere, may even come on the market in the relatively near future.

In the era of global warming, the many arid regions that already exist on the planet are only becoming more desert. The pressures associated with water supply, which are already traditionally complicated in normal times, therefore tend to become more and more important over time, with all that that entails for the local population. Therefore, there is an urgent need to develop new methods, and this is what scientists have tried to do with a gel that is able to draw water out of the air, even when the humidity is extremely high.

This work discovered by Interesting Engineering was carried out by a group of researchers from the University of Texas. Initially, they sought to develop a material that could always stay wet. For this, they developed a substrate that can absorb moisture from the ambient air during the night; thus recharged, it can stay moist much longer. The goal: to grow plants without having to water them manually. An approach that significantly reduces external resource requirements, workload and logistical complexity.

The concept worked quite well; in a month-long experiment, the researchers succeeded in growing radishes for 14 days by watering them only once at the beginning of the protocol. In parallel, the same culture died in a soil and sand substrate after only two days on average.

However, these experiments were all performed under at least average or even high humidity conditions. A constraint that has frustrated researchers; so they sought to adapt their concept to the most ruthless environments on the planet.

6 liters of water a day and per kilogram in the middle of the desert

That’s how they managed to develop this high-performance gel. They were based on two main ingredients. The first is cellulose, the main component of plant walls. The researchers changed its structure so that it becomes hydrophobic when heated; that means sherepelsWater, and that it can therefore be easily extracted from the gel.

The other important element is konjac rubber. It is a thickener better known as E425, which is often used in the food industry. Its porous structure accelerates the capture of water significantly thanks to the phenomenon of capillarity.

The result is a porous gel that is capable of trapping up to 13 times its own mass of water in an atmosphere of 30% humidity. By comparison, the average relative humidity in France is generally around 75%.

Even better: it can even do so in extremely dry areas. At 15% relative humidity – about the average for the Sahara desert! -, it is still capable of extracting up to 6 times its mass in water from the atmosphere. And all this in a completely passive way, without pump or capacitor.

Once saturated, simply heat the gel. Thermoactive cellulose therefore becomes hydrophobic; this has the effect of purifying the gel of its liquid, and it can be reused over several consecutive cycles. This can then be ingested immediately. A clear advantage in areas where access to water is difficult, even critical.

Cellulose, one of the main constituents of the plant wall, which is the core of the recipe for this gel, is available in abundance. © Alexander Klepnev – Wikimedia Commons

Efficient, cheap and easy to produce

This work deals with practical solutions that people can use to get water in the hottest and driest places on Earth.“, Explains Guiha Yu, one of the authors of the study, in a press release. “It could give millions of people without stable access to clean drinking water a simple method of generating water at home“, he says.

It is also an interesting approach thanks to its versatility. The researchers explain that it is possible to cast a film of gel in any form to adapt to all scenarios. Moreover, it is also very economical. In fact, its main components are extremely abundant. Rubber and thermoreactive cellulose are therefore very simple and very economical to manufacture. This is also the case for the rest of the minority components. The total cost is thus estimated at less than € 2 per kg.

Obvious limitations, but still commercial potential

However, there is still a limit, and not least. To take correctly, the gel must be more or less freeze-dried at very low temperature. This presupposes that you have access to equipment that is certainly not at the forefront of technology, but which nevertheless requires a certain level of infrastructure. A border that unfortunately diminishes its interest in the populations that need it most.

But that does not mean that this gel has no interest, far from it. Existing methods of extracting water from the air are exceptionally energy guzzlers, too many to be profitable on a large scale. This passive and practical method therefore makes it possible to fill a certain technological void; it could be an interesting resource during expeditions in the desert.

The concept is of particular interest to DARPA, the US Defense Division, which deals with the development of new systems for the military. The agency believes that this technology can prevent soldiers operating in a desert environment from carrying large reserves of water in their equipment. But this technology can also be useful to the average citizen in many cases. According to the researchers, it is therefore not excluded to see products of this kind land on the shelves of consumer stores in a few years.

The text of the study is available here.

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