According to some people, future wars will be fought over water, and a billion individuals throughout the world are already grappling to find sufficient water to survive.
Scientists from the National University of Singapore (NUS) have now addressed this problem. The team has developed a substance that removes water from the atmosphere without using any external power source.
Water in the Earth’s atmosphere can fill nearly half a trillion Olympic swimming pools; however, scientists have historically overlooked it as a source of drinkable water.
To remove water from this under-used source, a research team, under the guidance of Professor Ho Ghim Wei from the NUS Department of Electrical and Computer Engineering, has produced a new kind of aerogel, a solid material that is almost weightless.
When this aerogel is viewed under the microscope, it appears like a sponge but it does not need to be squeezed to extract the water it absorbs from the atmosphere. Moreover, it does not require a battery. In humid environments, 1 kg of aerogel will produce 17 L of water per day.
The trick lies in the long, snake-like molecules—called polymers—that build up the aerogel. The unique, long-chain polymer has an advanced chemical structure that can constantly alternate between water-repelling and water-attracting properties.
The “smart” aerogel autonomously collects molecules of water from the atmosphere, then condenses them into a liquid, and finally discharges the water. When there is sunlight, the smart structure can additionally increase the discharge of water by switching to a complete water-hating state efficiently. As much as 95% of the water vapor that goes into the aerogel exits as water. In lab tests, the aerogel released water continuously for months.
The team tested the water and observed that it fulfilled the standards set by the World Health Organization for drinking water.
Earlier, other scientists developed ways to remove water from the atmosphere, but their designs had to be fuelled by electricity or sunlight, and included moving parts that had to be closed and opened.
Currently, the team is seeking industry partners to upgrade the aerogel for industrial or domestic use. Perhaps, it could even be used in survival kits or endurance sports, for instance.
Given that atmospheric water is continuously replenished by the global hydrological cycle, our invention offers a promising solution for achieving sustainable freshwater production in a variety of climatic conditions, at minimal energy cost.
Ho Ghim Wei, Professor, Department of Electrical and Computer Engineering, National University of Singapore
Yilmaz, G., et al. (2020) Autonomous atmospheric water seeping MOF matrix. Science Advances. doi.org/10.1126/sciadv.abc8605.