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A Clever New Approach To Desalination
jbeaupre writes "The Economist reports on progress by a company called Saltworks on using saline gradients to do the heavy lifting of desalination. In essence, Saltworks uses solar energy or waste heat to concentrate sea water. They then use the ionic gradient between the concentrated brine and two sea-water streams to pull ions from from a 3rd sea-water stream. It appears to work with entropy by trading the reduced entropy of the desalinated water against the increased entropy of 'mixing' the brine and the other sea-water streams. The article only discusses Na and Cl, but even just removing these ions is a step in the right direction."
Yeah, pretty much, for all practical purposes, but not quite, because sooner or later the fucking sun will in fact burn out.
You didn't need to read TFA. It's in the summary. Second sentence.
# cat
Damn, my RAM is full of llamas.
what if they collected the fresh water vapour that is evaporating off the salt water as well?
I'm guessing this would require active refrigeration unless they're in a colder climate?
TFA is a bit light on details: why do Na+ ions go to one stream and CL- to the other? Have they got membranes that are impervious to CL- and NA+?
Yes. From TFA:
Be that as it may, atoms are not ions, which is what the attempt at an article states.
The article doesn't state that atoms are ions. Rather, it states that ions are electrically charged atoms, which is totally correct. Here is the exact quote, in context:
I don't find any incorrect statement in the above quote regarding ions.
The key piece of the work is an ion bridge.
No, the key piece of work is the idea. Ion bridges have been around forever.
This has to permit the travel of one kind of ion but not the other, i.e. Na+ or Cl-. Looks like this material could be expensive.
So you use, for instance, a polymer electrolyte (ionomer) with negatively charged side-chains for one bridge and a polymer with positively charged side-chains on the other. Only the counterions are mobile. The article says they're using modified polystyrene. This is not new, or terribly expensive. Similar things are already being used in industrial desalination technology for ion exchange columns.
It might plug up need to be periodically replaced.
Plug up with what? You naturally would have a mechanical filter to keep the crap out. It's not a major problem.
How expensive these are? How non toxic these are? What is needed to manufacture them? These are the questions we need to ask.
No, they're the questions asked by someone who doesn't know s--t about chemistry/chemical engineering. I happen to have a degree in the subject, but damnit, I learned about (used, even) polymer ion exchange columns in high school. If you want answers to your questions, go get Coulson & Richardson or some other chemical engineering textbook, and find the relevant section.
This technology is certainly very clever, but it does not make use of any new technology. The only question I think is worth asking here is whether or not it turns out to be more efficient or not.
The attitude of the GP was the problem. "These are the questions we need to ask", as if they were non-obvious and revolutionary. Whenever there is a post about an invention on /. the easiest way to get "+5 (Group-Wank)" is to write that it will never work because the inventors overlooked an issue a drunk chimpanzee could come up with. Then a thread ensues where everyone congratulates themselves on saving the world yet again.
You are right, the GP's questions were interesting and should have been answered in the article (which is for laypersons) and because they weren't it's good that someone answered them here on /.
The problem is that the GP posed the question in a way that implied he knew what he was talking about and was making a statement about the invention, instead of admitting that he had no idea and was asking for clarification. jm2c
Don't think of it as a flame---it's more like an argument that does 3d6 fire damage