Carbon Nanorods Created That Can Harvest Water From Dry Air

Trevor English

Play-doh was actually invented to become a wallpaper cleaner, but now we know it as a fun children's toy. Just like Play-doh's invention, scientists have just accidentally created small nanorods that are capable of harvesting water from the air. So, why are these carbon nanorods specia? After all, a lot of things can extract water from the air. Well, these rods extract more water at low humidity and expel water at high humidity, completely different from every other extraction method currently known.

"Here, we show that carbon-based rods can adsorb water at low humidity and spontaneously expel about half of the adsorbed water when the relative humidity exceeds a 50–80% threshold. The water expulsion is reversible, and is attributed to the interfacial forces between the confined rod surfaces." ~ Nature

carbon nanorods[Image Source: PNNL]

The discovery first came as Chemist Satish Nune from Pacific Northwest National Laboratories (PNNL) was taking a closer look at the nanorods with a vapor analysis tool. The rods performed contrary to other water receptors, as the entire assembly lost mass as the external humidity increased. The mechanism behind this unique behavior lies in the variable spacing of the rods, according to PNNL. When humidity is low, the rods maintain wide spacing which allows for water collection. However, as humidity increases, the capillary action of the water draws the rods closer together, in turn, expelling the absorbed water.

"At wide rod spacings, a monolayer of water can form on the surface of the carbon-based rods, which subsequently leads to condensation in the confined space between adjacent rods. As the relative humidity increases, adjacent rods (confining surfaces) in the bundles are drawn closer together via capillary forces." ~ Nature

This process had been proposed back in the 1990s, according to Science Alert, but nothing had been proven to indicate it was possible. Researchers were able to record the phenomena under microscopic video, but it is quite blurry. You can take a look at the process below, and watch with a close eye.

Uses for these nanorods are speculated to involve large scale water harvesting in dry desert environments. However, currently the accidental material is only effective at this task in around 10-20% of the entire mass. Now that scientists are beginning to understand how the material works, they believe they can refine it and increase efficiency. After efficiency is increased in the carbon nanorod structures, practical implementation can begin occurring.

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