Nanoporous Graphene Could Outperform Best Desalination Techniques | Hacker News Reader

Nanoporous Graphene Could Outperform Best Desalination Techniques

wateronline.com

73 pointspwg24 comments

Impressive find. However, given that the toxicity of graphene is not well understood[1], shouldn't there be significant concern for now about using graphene in processes which involve contact with food products? It's easy to envision a scenario in which a microscopic chunk of the stuff breaks off and ends up in the air or your stomach. The article only hints at this, where it mentions "mechanical stability."

[1] http://en.wikipedia.org/wiki/Carbon_nanotube#Toxicity

"In their simulations, the scientists strengthened the nanopores by passivating, or shielding, each carbon atom at the pore edge with either hydrogen atoms or hydroxyl groups."

Filed under the heading, "If someone knew how to build this stuff in volume, boy would it be useful."

This is good follow on work to other micropore work with graphene but as far as I can tell its just a simulation which points to areas that might lead to useful products.

Another cheap new desalination idea was recently presented at Google's Solve for X: http://www.youtube.com/watch?v=R63zYZZuRvQ#!

Instead of a fancy membrane it uses some nifty chemistry. Doesn't take much energy and the chemicals are in a closed loop.

Thank you for the link. The McGinnis's talk was very interesting, but there are some other more just as good.

I wonder if that flow rate would be high enough to build this membrane into a drinking straw, so you could take a safe drink right out of the ocean with a cheap, compact device. This seems like it has the potential to revolutionize camping and survival in the near-term, and eventually the availability of clean water everywhere.

I am far from an expert here, but http://en.wikipedia.org/wiki/Reverse_osmosis#High_pressure_p... and http://urila.tripod.com/desalination.htm/ both claim one needs Over 20 bar of pressure for reverse osmosis. I doubt anyone can suck that hard (apologies for the pun)

The whole point of the article is that this membrane has about 1000x higher flow rate than RO filters.

I still am not an expert, but the way I understand this is that, at say 30 bar, this membrane would produce 1000 times the amount of desalinated water as a conventional system, not that it would produce 100 times more at 3 bar or 10 times more at 0.3 bar than conventional ones at 30 bar.

Actually, we already have that:

http://en.wikipedia.org/wiki/LifeStraw

Interesting, but the linked device doesn't seem to desalinate water. It claims to filter out disease-causing organisms.

Ah, it seems you're right. My mistake.

Wouldn't the water have to be sanitized first? It sounds as if it only filters sodium, not other dangerous particles.

The pore size is very slightly bigger than a single water molecule, and smaller than a single sodium ion. Heavy metal atoms are much larger than sodium atoms, and would not go through the membrane. Any kind of virus or bacteria is much, much larger than this molecular scale, and have no hope of traversing. I am not aware of any harmful water-soluble substances as small as a water molecule.

Hydrogen fluoride comes to mind, but it's probably not an important pollutant in most of the water sources we care about.

I can't think of anything else that small that would be a problem.

Wouldn't hydrogen fluoride just be fluoride ions in solution? Water molecules tend to clump around charged ions, which might impede traversal of the membrane.

Not much is both water soluble and smaller than sodium. For the most part your basically left things like individual molecules of lead or other heavy metals which you would need to drink a lot of water from vary contaminated sources before you had a problem.

Ed: Individual sodium atoms are smaller than individual lead atoms. However, under the assumption that there is some variation in filtering capability's that will let a low % of things in that are sodium sized and slightly larger through you may have to deal with some larger atoms like lead.

It would have to pass through a fairly hydrophobic (the pore) layer. The water can barely get through since it's polar but uncharged; most metals in solution are charged ions and wouldn't be able to pass through the barrier.

It sounds like it pretty much just lets H2O through, but it's possible that other small molecules could as well. It certainly wouldn't allow for any sort of organism, but harmful elements could get in.

There are already technologies beyond reverse osmosis in large scale industrial use (and I'm not referring to brine or similar high energy approaches)

Siemens has built a desalination plant in Singapore that works similar to dialysis (mimicking kidneys) and is using a fraction of the energy required for a comparable RO solutions (http://www.desalination.biz/news/print.asp?id=6008).

The key issue with all membrane / filter based desalination solutions still is the lifetime / service requirements of the filters.

I thought Reverse Osmosis was already close to its thermodynamic limit (in terms of efficiency)?

Estimated time to product?

Why not sooner?

This is an honest question. Millions would like such a product yesterday. I'd like to know how long it might take to market, and understand why it could not be done sooner.

Didn't expect such questions be downvoted on a business/product startup site.

Considering that this is a molecular dynamics simulation that anyone could produce at home on their computer, with some patience, I assume it will be ready in a few years after their get their grant money.

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