Water Harvesting From The Air

There is plenty of water on Earth (and in the Solar System as a whole), but it isn’t always in a location or form that humans can use. Separating water from other stuff (e.g., desalination) takes energy, as does moving from one place to another. Another possibility is to separate water out of the air with a dehumidifier, which also takes energy, especially if the air isn’t especially humid.

One of the things I learned in (extremely) basic undergraduate chemistry is that given the right catalyst, magic is possible. If you can find just the right molecules in the right geometry, you can tunnel through energy barriers.

If.

This is the great age of Material Science, not to mention nanotechnology. We have better and better tools for fiddling around with atoms and molecules, which means we can create new catalysts and other magical materials.

Not surprisingly, producing pure water is an important target. (A human can live for a long time without oil or gold, but only a day or two without water.)

This month Hyunho Kim and colleagues from Berkeley, MIT, and other institutions are publishing a method for harvesting water from the air. [1]  The secret is a special material, “porous metal- organic framework” which they charmingly describe as, “microcrystalline powder MOF-801, [Zr6O4(OH)4(fumarate)6]”.

For decades, these researchers have been exploring thousands of such MOF’s, each of which has unique properties. This one incorporates Zirconium, and is very efficient at grabbing water molecules. Applying low heat, which could come from solar energy, the water is released and collected.

Altounian/Science

This is kind of the same idea as a dehumidifier, only it is designed to use diurnal shifts, i.e., cool night air saturates the material, and then the hot daytime pushes the water out.

This small device can harvest over 2 liters of water per day out of the air, with relative humidity as low as 20%, using only the power from sunlight! So cool!

The paper reports the studies (theory, simulation, experiment, and demonstration), which show that this material is rugged enough and lasts for many cycles—with no need for external power! In short, this could provide a source of water for a long time, at low operational cost.

This initial version uses Zirconium, which is pretty rare and expensive. But the researchers are investigating a version that uses Aluminum instead, which would reduce the cost of materials a lot.

This is an amazing development. Making it into a product will need to work out practical details, including safety, reliability, and health checks. Using this in a home or farm will need a fool proof system, that is protected from human error (sticking your hand in, toddler sticking her head in) and from hazards such as nesting insects nesting birds. It will also have to deal with dust, fire, rain, lightning, extreme heat, spilled food, and other surprises.

It will also be important to assure that the recovered water is clean and safe to use, and remains so over long period of unattended use. There must be some way to deal with mold and other contaminants that will both foul the works and taint the water. How do you clean the parts and the chamber? For that matter, the device itself must not corrode or leach unwanted materials into the working parts or the water.

I’m sure that these challenges can be met, so I look forward to seeing this technology become wifely avaialblte

Nice work, all.

  1. Hyunho Kim, Sungwoo Yang, Sameer R. Rao, Shankar Narayanan, Eugene A. Kapustin, Hiroyasu Furukawa, Ari S. Umans, Omar M. Yaghi, and Evelyn N. Wang, Water harvesting from air with metal-organic frameworks powered by natural sunlight. Science, 2017. http://science.sciencemag.org/content/early/2017/04/12/science.aam8743.abstract
  2. Robert Service, This new solar-powered device can pull water straight from the desert air. Science – News.April 13 2017, http://www.sciencemag.org/news/2017/04/new-solar-powered-device-can-pull-water-straight-desert-air

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s