Nanorods: water-oozing material could help quench thirst | Hacker News Reader

Nanorods: water-oozing material could help quench thirst

pnnl.gov

43 pointswallflower15 comments

That is a really fascinating result. It would also explain the mechanism of graphene sieves. One of the really amazing behaviors of graphene is that you can pour water on top of it, and pure water pops out of the bottom[1].

[1] http://phys.org/news/2016-03-revolutionary-graphene-filter-c...

So it deionizes the water too? Wow. If this technology does the same, doesn't that imply we'd need to supply people using this as a source of water with electrolytes and minerals for the water?

How is it different from desalination where you add some of the salt back in because the water is too pure?

Mineralizing water is pretty straight forward, treating it to safe drinking levels is much more complex. So if you simplfy 80% of the water treatment facility's job, you can often process significantly more water through it at the same cost.

I often wonder if this matters anymore, since food has a high amount of salt, and minerals.

The food in developing countries doesn't necessarily.

Until, of course, it becomes completely clogged.

Ultra-fine filters are going to get locked up by debris quickly.

Fortunately, you can probably replace a graphene filter quickly with plenty more freely available/easily producible graphene (quality and practicality of diy graphene might be dubiuous), but, considering the clean-room level of filtration, I'd figure you might need LOTS of graphene, and several layers of coarse filtration, before filtering at the nano-scale.

I don't think we need to drink water THAT pure though. Although, I guess I'm only thinking about the practical application as a water filter, but I imagine it could be useful in purifying water for science.

Is there no way to work a cleaning mechanism into the material? Dry it and static charge?

This is pretty exciting, and the applications are almost unlimited, and many of them highly marketable. Athletics clothing alone is billions of dollars around the world, but this a key too:

""But before we can put these nanorods to good use, we need to be able to control and perfect their size and shape," added Nune, the paper's other corresponding author."

It seems to me that could be a long process, along with the challenges of scaling up manufacturing. Still, at some point, this is going to be a very useful material.

These papers also noted the process was theorized as early as the 1990s by scientists examining crystallized proteins. Back then, scientists noticed they only saw water vapor surrounding hydrophobic sections of protein, while liquid water would surround other areas. The researchers proposed that there was some sort of process that enabled the water caught between hydrophobic protein sections to suddenly vaporize.

This seems reasonably obvious, at least in retrospect. Trap a very small number of water molecules in a region where they can't combine with others to form a liquid, and it's reasonable to expect those molecules to simply waft away. A molecule made from two hydrogen atoms and an oxygen atom weighs much less than the diatomic oxygen molecules in the air, so why wouldn't they displace those molecules?

Could someone with appropriate background explain where does the energy to evaporate the water come from?

Can they work the other way - could you build a solid state dehumidifier with these?

They mentioned harvesting water from the air in the article, so yes.

Activated charcoal is already a pretty good dehumidifier; this just seems to take the adsorptive properties of high-surface-area carbon one step further by giving the water an easy path "out" once it's adhered and amassed, keeping the carbon from getting "used up."

I wonder if a similar thing could be done with silicon nanorods, given the similarity between activated charcoal and silica gel. "Silicon nano rods" sounds a lot like asbestos—and apparently asbestos is adsorptive, just not of water—but asbestos is micro-scale at best. Meanwhile, SiO2 nanotubes apparently exist[1], but don't show any particular adsorptive properties.

[1] https://en.wikipedia.org/wiki/Silicon_nanotube

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