Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
The mutter of invention.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.

user:
pass:
register,


                                                                                     

Harmonic desalination

Use sound waves to cause sweetwater to separate from brine
  (+4, -1)
(+4, -1)
  [vote for,
against]

Use sound waves to cause sweetwater to separate from brine, by causing the heavier parts to slowly move towards a certain region where either the brine, or the sweetwater, can be easily be extracted.

----- [ edit following remarks from my friends and foes ] ----

If centrifuges and cyclonic separation work, why wouldn't directional standing waves do the same?

As a matter of fact, even gravity slowly does this. At sea the top water is much less salty than the lower layers, and sweetwater, entering the sea from rivers, FLOATS above the salty water.

When I say brine I mean seawater with all the diverse types of salts dissolved in it.

The water is constantly shaking back and forth with the heavier molecules moving slower than the lighter ones, which would presumably create regions with different grades of solubility.

pashute, Jan 05 2017

Lithium Exploration Group http://altadisposal...rasonic-technology/
"can desalinate sea water at a rate of 25-35 cubic meters per hour. The two discharge streams are distilled water and chemical grade salt." [8th of 7, Jan 05 2017]

What's in seawater ? http://www.utdallas...TS-IN-SEA-WATER.htm
A bunch of stuff. [popbottle, Jan 05 2017]

Mixtures vs. Solutions k-12 http://k12opened.co...ndex.html#mbp_toc_4
Didn't remember any diff from this during my university years, in the advanced biochemistry lessons... [pashute, Jan 10 2017]

wikipedia on the hilsch vortex tube https://en.wikipedia.org/wiki/Vortex_tube
[beanangel, Jan 10 2017]

Multiple liquid phases in water https://www.researc...5472432a7000000.pdf
Supercooled, simulated water, that is. Maybe the real stuff does this too, or maybe not. [Wrongfellow, Jan 12 2017]

More on multiple liquid phases http://phys.org/new...ow-temperature.html
[Wrongfellow, Jan 12 2017]

[link]






       Somebody's going to "that'd be good for a barbershop", so it might as well be me.
not_morrison_rm, Jan 05 2017
  

       More detail on the actual method of action would be nice. Come on, [pash], you're better than this. ...
8th of 7, Jan 05 2017
  

       This will fail, but only for fundamental reasons.   

       The linked technology is for separating solids from water - I don't know how it works, but it's plausible.   

       However, sound waves will do nothing to salt water, except possibly to annoy it. Bad science.
MaxwellBuchanan, Jan 05 2017
  

       Sea water does not just contain salt (NaCl).
popbottle, Jan 05 2017
  

       That is undoubtedly true, and it is conceivable that sound waves might help with the removal of things like sand, silt, whales, islands or other particulates.   

       Howevertheless, no amount of shouting at seawater will help to remove dissolved salt, which is what the idea was about.   

       I must, therefore, vote 'non'.
MaxwellBuchanan, Jan 05 2017
  

       actually if you use comically large amounts of energy, and lasers this might work.   

       propellers produce cavitation (bubbles) the inner surfaces of these bubbles could be evaporated with lasers forming a salt crust on the interior of the bubble. then since there is solid particulate matter acoustic vibrations can move it.   

       this is wildly impractical, yet it might be possible to make salt crystals in a cavitation bubble. If you can figure out how to make large bubbles, say from bubbling air it is cheaper.
beanangel, Jan 06 2017
  

       //comically large amounts of energy, and lasers   

       Sounds good to me.
not_morrison_rm, Jan 06 2017
  

       what [beanangel] said... which worries me, a little.
FlyingToaster, Jan 06 2017
  

       If centrifuges and cyclonic separation work, why wouldn't directional standing waves do the same?   

       As a matter of fact, even gravity slowly does this. At sea the top water is much less salty than the lower layers, and sweetwater, entering the sea from rivers FLOATS above the salty water. When I say brine I mean seawater with all the diverse salts melted in it.   

       The water is constantly shaking back and forth with the heavier molecules moving slower than the lighter ones, which would presumably create regions with different grades of solubility.   

       And then there's [8th]'s link which answer's his own question. Drat. Does this mean the idea's baked?   

       But then again, this is Halfbakery and we are always halfppy to see it halfpen.   

       [Adding the explanation above to the idea itself]
pashute, Jan 08 2017
  

       So just brine Chladni patterns with draw off tubes. I wonder if a super computer could compute the changing interference waves to crystalise out the different salts? - Orchestral Alchemy.
wjt, Jan 08 2017
  

       //If centrifuges and cyclonic separation work, why wouldn't directional standing waves do the same? //   

       They don't. They are not used to separate salt from water. Seriously, they just arent.   

       Freshwater floats on salt, until they mix, after which they don't separate again under gravity. The reason the top layers are less salty is that they recieve the influx of fresh water from rivers and from rain, and mixing takes a long time.   

       Under several hundreds of thousands of G (in an ultracentrifuge), you can just about create a concentration gradient of caesium chloride.
MaxwellBuchanan, Jan 08 2017
  

       //Under several hundreds of thousands of G (in an ultracentrifuge), you can just about create a concentration gradient of caesium chloride.//   

       ...What about at very low temperatures, ie just above freezing? Reason I'm asking is that the brownian motion would be slowed down significantly. Can you get any gravitational separation at very low temperatures?
Custardguts, Jan 08 2017
  

       Probably. But the difference between 293K and 260K isn't going to be very helpful.   

       I think [pashute]'s misunderstanding is something like "Sand will settle out of water. Salt is not much less dense than sand. Therefore salt will settle out of solution."   

       It's very impressive misunderstanding, because it goes so deep. Most people never think things through enough to really fail to grasp the fundamentals in the way that [pashute] has.
MaxwellBuchanan, Jan 08 2017
  

       Ion exchange membranes have a higher affinity for molecules than water, thus they concentrate brine.   

       It is possible that eentsy particles, like slurry of ion exchange resin grains, vibrated with sound, could concentrate salt faster, basically because they had more rapid fluid flow., although as their mass changes they might be steerable with vibrations into a pile.   

       the thing though is that this differs from the idea, and it would be expen$ive, although i think there are ion exchange resin tubes (yet perhaps just PTFE-like membranes) that desalinate water.
beanangel, Jan 09 2017
  

       So, overall, the verdict is that this idea would definitely work, as long as you ignore its fundamental flaws and use a functional technology instead.
MaxwellBuchanan, Jan 09 2017
  

       Don't dismiss the discovery of the eentsy particle either.
normzone, Jan 09 2017
  

       Or that water isn't made of molecules.
notexactly, Jan 09 2017
  

       Hmm. Around two years ago I was told by a friend Prof from the local Sea Research institute that the layers of salinity were true throughout the oceans.   

       I then assumed that dissolved salt - not being a chemical COMPOUND but rather a MIXTURE, would have some "free" water molecules while others were connected to the Na and to the Cl.   

       I also remembered that chromatography separation works mainly by gravity separating the heavier solutions and that it is used with dissolved mixtures.   

       I don't think this is a FUNDAMENTAL misunderstanding of mine, but rather a lack of a very specific piece of knowledge, not usually studied in school. Looking at the link I just posted, you'll see what we all learned. And not changed in university classes, namely that solutions are inseparable by filtering or sifting because the mixture is now at a molecular-size level.   

       Did you all know that you cannot separate a solution into layers of density if it is well mixed even when not in a high concentration?   

       And I still cannot find a source offhand showing that a solution cannot be separated into higher and lower density fluids by using a centrifuge.   

       And, of course, I never mentioned getting solid salt through this. I was talking about Lowering the salt(s) density in some of the water. I'm not such a fundamentalist.
pashute, Jan 10 2017
  

       <bad taste pun>   

       Ahh, not looking for some sort of "Final Solution" then ...   

       </bad taste pun>
8th of 7, Jan 10 2017
  

       Where to begin, [pashute]...where to begin.   

       //dissolved salt - not being a chemical COMPOUND but rather a MIXTURE// Completely not. Dissolved salt is a solution, which is completely different from a mixture.   

       //chromatography separation works mainly by gravity separating the heavier solutions// Again, completely not. There are many forms of chromotography, and not one of them separates compounds on the basis of their molecular, atomic or ionic weights.   

       //Did you all know that you cannot separate a solution into layers of density if it is well mixed even when not in a high concentration?// I guess most people with a scientific background know; the general public probably not so much. And you *can* create a concentration gradient (though not absolute sepration) if the solute is a heavy ion or molecule, and if the G-forces are absolutely huge.   

       //And I still cannot find a source offhand showing that a solution cannot be separated into higher and lower density fluids by using a centrifuge. // The reason you can't find is that (a) in most cases (typical lab centrifuges) you can't achieve any significant enrichment/depletion; and (b) in extreme cases (ultracentrifuge; dense solute like caesium chloride) you can achieve a slight enrichment/depletion.   

       Please note also: it doesn't work if you use a lower G-force for a longer time. That's because diffusion (entropy, basically) is working against you all the time. In an ultracentrifuge, you can create a modest concentration gradient of CsCl; but that gradient will be stable (ie, will not get steeper) after a time. By the same token, a few thousand G will not achieve any significant redistrubition of NaCl, however long you leave it.   

       More important, though: we never did find out why you have a million litres of surplus wine.
MaxwellBuchanan, Jan 10 2017
  

       I have seen nifty slomo videos where ultrasound produces cavitation. Inside these cavities, I presume, the substrate has become a gas. Sometimes these cavities flash with light as they collapse, because they are so awesome. Sonoluminescence!   

       Salt cannot be dissolved in gas phase water. Turning water to gas causes resident salt to seek asylum in neighboring liquid water. Under circumstances of water rapidly turned to gas by sound that is ultra, or plus ultra, desperate ions might seek each other in fright, clasping each other in crystalline form as their solvent disappears. Before they realize what has happened, these crystals might be quickly sucked away by a cunning apparatus.   

       As regards the million liters of surplus wine I presume perhaps pashute meant the roman numberal use of M, which would be a mere thousand liters, and "wine" to be inclusive of other substances besides wine.
bungston, Jan 10 2017
  

       Yet another solution use microwave induced magnetohydrodynamics to swirl the water into tremendous pressure, then send it through a MHD version of a hilsch vortex tube [link], which is capable of sorting cool water from warm water (really actually, the navy published a thing on using water)   

       If you do this with really huge amounts of energy, the cold water would dissolve less salt, becoming fresher.
beanangel, Jan 10 2017
  

       //capable of sorting cool water from warm water (really actually, the navy published a thing on using water) //   

       Wait - hold on - hang on there just one cotton-picking second. The Hilsch vortex works for air by compressing and expanding the air differentially, and is very clever indeed.   

       For liquids, my understanding is that you can generate a hot output, plus another output which is no cooler than the input. In other words, there is no partitioning of heat if the medium is a liquid: you just selectively heat one of the output streams (using the work that goes in to pushing the water through the system).   

       If you have a link that shows that part of the water coming out is actually cooler than the water going in, then (a) I would like to see it and (b) I may not believe it even then.
MaxwellBuchanan, Jan 10 2017
  

       [mb] I think you are right. The wikipedia reference says that at a noncompressible fluid you can get warm and warmer water rather than warmer and cooler water.   

       now that that one is out, there might be another approach. Le chateliers principle has to do with the amount of dissolves materials in a solute. It is possible to get materials to crystallize out if you add salt. so does le chatelier's principle respond to hydroxyl and hydrogens ions?   

       basically, you put a couple carbon electrodes in some salt water, then collect the acidified and baseified water from next to the electrodes. If you add that H or OH enriched water to salt water, does the equilibrium shift as a result of lechateliers principle. I think it would shift. Any shift would represent concentrating or diluting of the saltwater, using only the electrolysis products of the same water.   

       if a person is easily amused (kind of like me) then   

       This might be more efficient than just turning the electricity into heat to evaporate away the water, because noting that saltwater has electrical resistance, you could boil water with DC electrodes, while also concentrating the H as well as OH from near the electrodes to change the concentration of ions at the material you boil   

       Or since you could already just boil it to purify the water, if you add hydrogen ions or hydroxyl ions to it, is it more efficient than just boiling away the water?
beanangel, Jan 10 2017
  

       [Max] So there is no imaginable motion that can be applied to a mixture of molecules, that form a liquid environment, that will bump them against each other into some sort of gradient? A line dance, if you will.   

       If there is other dimensions at work, then they too would have to be manipulated. I am thinking the EM field space between molecules.
wjt, Jan 10 2017
  

       //So there is no imaginable motion that can be applied to a mixture of molecules, that form a liquid environment, that will bump them against each other into some sort of gradient? //   

       Yes there is. You could use electrolysis or electrophoresis, for instance.   

       One point to bear in mind. Dissolved substances are usually surrounded by a shell of solvating water molecules, and and in some cases the formation of that shell releases energy (as heat) when the substance dissolves. There is also the entropy change that comes from changing a highly ordered crystalline solid into a mass of wandering solute ions (or molecules). The end result is that you have to put energy into the system in order to remove the solute from solution. Heat energy is generally not helpful (except for a few substances whose solubility is lower as the temperature increases). So, you need a mechanism to deliver the energy needed for de-solvation.   

       Very extreme G-forces (a la ultracentrifuge) will just about deliver enough energy (in the form of gravitational potential energy of the solute) to form a weak gradient in a solution of dense solute. Electrophoresis supplies energy to an ionic solute. It's hard to see how sound can deliver energy selectively to the solute, or indeed deliver energy in any useful way.   

       The idea as posted comes under the heading "Not Even Wrong".
MaxwellBuchanan, Jan 11 2017
  

       Admittedly, they would need to be very loud sounds.
bungston, Jan 11 2017
  

       I suppose, technically, it would be possible to desalinate water using sound. The appropriate sound would be a voice saying "Please switch on the desalinator."
MaxwellBuchanan, Jan 11 2017
  

       I think we all (is this a we all?) should think of new desalinator ideas. one thing that suggests this is possible is that Science News may have emphasized a new one sometime during 2015 or 2016. Now having said that i have to reread the gibbs equation   

       also, there is a sphere packing possibility even though water isnt sperical ( > ish). When you think of highest density sphere packing you get that hexagonal staggered thing. i once saw an image of the least dense sphere packing possible. it looked kind of like hollow octagons tesselated. It is possible, that just before steam, water might produce new tesselations, and some of those tesselations might give up their Na and Cl ions more readily.
beanangel, Jan 11 2017
  

       // It is possible, that just before steam, water might produce new tesselations, and some of those tesselations might give up their Na and Cl ions more readily. //   

       Water does have multiple liquid phases that depend on where the temperature is in the range between 0 and 100 °C. I can't find a good source for this at the moment, but I seem to remember one of the liquid–liquid phase transitions happens somewhere around 55 °C, and causes some change to the refractive index (I think) of the water. Perhaps it influences solubility as well.
notexactly, Jan 11 2017
  

       //Water does have multiple liquid phases //   

       Uh, I'm pretty sure it doesn't. And all the phase diagrams I can find show only a single liquid phase. If you know differently, I would be intrigued.
MaxwellBuchanan, Jan 11 2017
  

       Why not put the salt ater in a huge shallow lake, say 22 mm deep. Set up your oscillator/vibrator, then cover the whole lake with a clear, plastic membrane. Inflate the membrane and place troughs around the inner perimeter of the membrane and turn on your oscillator/vibrator. As soon as the sun starts shining through the membrane onto the water, it will heat up and evaporate. Clouds of water vapor will form inside the membrane water vapor entrapment area and condense on the inner surface of the membrane and start dripping down the membrane into the troughs which are connected to basins that collect the resulting fresh water. All the while the confident "hummm" of the oscillator/vibrator will be heard in the back ground. As it majestically humms along the water evaporates and turns into fresh water. Eurika! It could work! I like this oscillator/vibrator idea. I'm bunning it.
Altoidian, Jan 11 2017
  

       I see science as mostly about getting sharper. Learning how stuff works so actions can be more accurate. You can cut a tree down with a sledge hammer but trial,error and science has shown an edge pointed forced will use less energy and time.   

       I imagine future energy wroughting methods will only get more precise, intricate and mind blowingly complex. Distillation will be a piece of cake.
wjt, Jan 12 2017
  

       //Water does have multiple liquid phases //   

       A quick google finds some simulation results that suggest that this might be somewhat true, if you're a theoretician. [links]
Wrongfellow, Jan 12 2017
  

       Well, that's interesting, especially if it applies to real water.   

       Incidentally, [pashute], the content of one of your links reads: "Solutions cannot be separated by a screen or a filter. That is because the parts are mixed together in a way that they all have the same size." This is meant to be some kind of online textbook, and they should be ashamed of themselves.
MaxwellBuchanan, Jan 12 2017
  

       I am amazed that no one has brought up that electrolysis of saltwater can produce chlorine (and hydrogen) gas. so with sufficient electricity you get a bunch of NaOH water, sodium hydroxide might have a different solubility than NaCl, thus changing the energy to make crystals you filter out of the solution.   

       The other thing about this is that [pashute] wanted to use tuned EM to separate salt from water. When you think about the numeric efficiency of generating radio waves compared with electrolysis it is possible electrolysis, which also produces evaporative warmth might be fundamentally more efficient, even if the yield of chlorine gas is moderate.
beanangel, Jan 13 2017
  
      
[annotate]
  


 

back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle