Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

A way to make water potable using carbon dioxide

economist.com

Post reply on HN
Print view View original

31–40 of 40 posts

Re: A way to make water potable using carbon dioxide

#31

Post by URSpider94 »

sintaxi wrote: post #22

You can make virtually any water source potable by boiling it. It so happens hot water has other useful purposes as well so why are we not showing those 1.8B people how to efficiently boil water? What am I not getting?

I would wager everyone out there knows, either explicitly or implicitly, that boiling water is a great way to clean it. People are looking for something better that can scale to give everyone clean drinking water. Boiling water for the length of time needed to render it safe to drink is terribly energy-inefficient, which is why it's not done in water treatment plants anywhere in the developed world.

Re: A way to make water potable using carbon dioxide

#32

Post by xyzzyz »

amelius wrote: post #20
mchannon wrote: post #16

Is this a breakthrough? Sure. But it's probably not a panacea. * Getting actual salt particles out of flows of water is not what their experiment accomplished. They got larger particulates out of the water. The latter is quite easy to do, and the former quite difficult. * Ionic charge is a very powerful driving force when what you're trying to move has a directionality to it, like a magnet picking up iron filings. Th…

> When salts are dissolved, their constituent parts form ionic dipoles that will work far harder to stay together in solution. A little bit of ionic charge bias presents no challenge to a sodium chloride pair. An electric field of a few volts over a small channel seems to split this dipole just fine, [1]. [1] https://cleantechnica.com/2013/06/30/desalination-with-small...

As of now, the best that the researchers have achieved is 25% desalination

25% is quite far from "just fine". Has there been any progress on the method in last 4 years?

Re: A way to make water potable using carbon dioxide

#33

Post by microcolonel »

PhantomGremlin wrote: post #27
doorley wrote: post #23

Sounds like a promising piece of technology. What I'm more impressed with, though, is the scientific journalism. It's balanced, accurate, accessible, representative, and leaves out the hyperbole. I would pay for science journalism that read like this. Even better if it came with some biased, inflammatory, hyperbolic editorials on the side.

What I'm more impressed with, though, is the scientific journalism. Actually I was disappointed with the article. The image at top shows two output streams: waste, and filtered water. I was expecting an explanation of this while reading the article. But as I read the words, the build-up wasn't matching the image. Finally we come to: In a working system it would simply be a question of splitting the water stream into…

The sentence before the one you mention explains it; the only problem with the top diagram in the header image is that it doesn't make it clear that opposite the CO₂ side of the stream, there is an air side. Seems like the diagram represents their experimental model (two exit streams), not the practical application (three exit streams).

> As the team hoped, this arrangement caused suspended particles with positive surface charges to concentrate towards the CO₂ side of the water stream, and those with negative surface charges to concentrate towards the air side, leaving the centre of the stream more or less particle-free.

Re: A way to make water potable using carbon dioxide

#34

Post by amelius »

xyzzyz wrote: post #32
amelius wrote: post #20

Earlier quoted context omitted.

> When salts are dissolved, their constituent parts form ionic dipoles that will work far harder to stay together in solution. A little bit of ionic charge bias presents no challenge to a sodium chloride pair. An electric field of a few volts over a small channel seems to split this dipole just fine, [1]. [1] https://cleantechnica.com/2013/06/30/desalination-with-small...

As of now, the best that the researchers have achieved is 25% desalination 25% is quite far from "just fine". Has there been any progress on the method in last 4 years?

Repeat the process 10 times, and you're at 95% desalination.

Re: A way to make water potable using carbon dioxide

#35

Post by jerf »

PhantomGremlin wrote: post #27
doorley wrote: post #23

Sounds like a promising piece of technology. What I'm more impressed with, though, is the scientific journalism. It's balanced, accurate, accessible, representative, and leaves out the hyperbole. I would pay for science journalism that read like this. Even better if it came with some biased, inflammatory, hyperbolic editorials on the side.

What I'm more impressed with, though, is the scientific journalism. Actually I was disappointed with the article. The image at top shows two output streams: waste, and filtered water. I was expecting an explanation of this while reading the article. But as I read the words, the build-up wasn't matching the image. Finally we come to: In a working system it would simply be a question of splitting the water stream into…

I just checked this after reading the article, and that diagram appears as-is in the original paper, per jesseaustin's link to https://www.nature.com/articles/ncomms15181 . So I'm actually going to have to give the journalist a pass; I hardly expect them to produce more accurate diagrams than what is in the original paper.

Re: A way to make water potable using carbon dioxide

#36

Post by xyzzyz »

amelius wrote: post #34
xyzzyz wrote: post #32

Earlier quoted context omitted.

As of now, the best that the researchers have achieved is 25% desalination 25% is quite far from "just fine". Has there been any progress on the method in last 4 years?

Repeat the process 10 times, and you're at 95% desalination.

It may or may not work, depending on the details of the process. For instance, the process might only be able to separate the ions if the concentration is high enough. If it's the case, repeating the process on the result will not make any difference.

Re: A way to make water potable using carbon dioxide

#37

Post by orthecreedence »

sintaxi wrote: post #22

You can make virtually any water source potable by boiling it. It so happens hot water has other useful purposes as well so why are we not showing those 1.8B people how to efficiently boil water? What am I not getting?

I did not know you could boil lead out of water.

Re: A way to make water potable using carbon dioxide

#38

Post by yuhong »

ChuckMcM wrote: post #15
mhb wrote: post #14

Earlier quoted context omitted.

As to the necessary CO2, he imagines this would come from power stations and other industrial processes, such as cement-making, that produce the gas in large quantities as exhaust. This would restrict diffusiophoretic water plants to industrial cities—but, since such cities are huge sources of demand, that is hardly a problem.

I read that, but noted it suffers from 'scientist' blindness. These industrial processes, that are producing CO2 in large quantities, don't have an economical way to capture and cleanse that CO2 to allow for then shipping and selling it (or giving it) to this guy to clean water with it. If they could capture the CO2 they could already resell it economically as there are lots of uses for it. There was some work in 201…

The fun thing is that burning hydrocarbons also itself produce water too!

Re: A way to make water potable using carbon dioxide

#39

Post by sintaxi »

orthecreedence wrote: post #37
sintaxi wrote: post #22

You can make virtually any water source potable by boiling it. It so happens hot water has other useful purposes as well so why are we not showing those 1.8B people how to efficiently boil water? What am I not getting?

I did not know you could boil lead out of water.

1.8B people drink untreated water with feces in it.

Re: A way to make water potable using carbon dioxide

#40

Post by dx034 »

doorley wrote: post #23

Sounds like a promising piece of technology. What I'm more impressed with, though, is the scientific journalism. It's balanced, accurate, accessible, representative, and leaves out the hyperbole. I would pay for science journalism that read like this. Even better if it came with some biased, inflammatory, hyperbolic editorials on the side.

Was that supposed to be a joke? If not, you can easily pay for journalism like this by subscribing to the Economist.
Post reply on HN