h a l f b a k e r yChewable.
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* Distilled water is circulated through a pipe/tank circuit.
* At a point in the cycle, the water is exposed to a low voltage electrical current which will attract the naturally present hydroxide and hydronium ions to opposite sides of the pipe.
* A semipermeable membrane allows these ions to
pass out of the pipe, where they are stored /accumulated in a (far more concentrated) solution.
*The water re-enters the tank where the water has time to re-establish equilibrium, and the cycle continues.
*The tank is periodically topped up with distilled water to account for the water removed as ions.
*After a very long wait, you will have a solution of concentrated hydroxide ions, and hydronium ions.
* The following electrolysis can now be performed:
4H+ + 4OH- ----> 2H2 + O2 + 2H20.
*This will only take slightly more than 0.4 volts, as opposed to the more than 1.23 V electrolysis more commonly employed.
*Better still, the Hydrogen can be used to generate (slightly less than) 1.23 Volts in a fuel cell.
*Ok, it's a stretch; quantities will be small, and all that is occurring is that I'm taking advantage of atmospheric energy which causes the dissociation... but still.
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I don't think this will work. |
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Wait, at the end, I also get peroxide? Tell me more. I am building a rocket. Is this a reverse fuel cell? I had heard that some one created a reverse fuel cell and ended up with peroxide. |
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So, the ideal fuel source for itinerant hairdressers? |
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It would be tricky to make a membrane permeable only to ions. |
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If you are already throwing about low voltage currents why not just electrolyze the water with that? |
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You have sails with that? |
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No, the whole point of this idea is to remove and concentrate the hydroxide and hydronium ions already present in water ... therby allowing Hydrogen to be produced with a much lower voltage. |
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hey MaxwellBuchanan, why "no" ? |
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Because I am pretty sure it's not going to work. You're
trying to pull out the naturally occurring ions in water, and
then electrolyse these (which is easier than electrolysing
water itself) - do I understand correctly? If so then I see
two flaws: |
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1) You're using energy to pull the ions out of the water in
the first place. Is this accounted for? |
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2) Ultimately, however you're doing it, you're converting
water into hydrogen and oxygen, and this requires a finite
energy whichever cycle you use. So, your only hope is to
increase efficiency. I'm not sure what the efficiency of
conventional electrolysis is; are you claiming this is more
efficient, or that it requires less energy even if efficiency
considerations are ignored? |
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Well to electrolyze water producing hydrogen and oxygen requires 1.23 Volts. (or more due to inefficiencies) |
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To Electrolyze Hydronium and Hydroxide, producing Hydrogen and water and oxygen requires 0.4 V (or more due to inefficiencies) |
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Would the energy required to pull these ions out and concentrate them surpass this saving ? |
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So this latter pathway is not converting water into hydrogen and oxygen, it's the oxidation of hydroxide into water and Oxygen and the reduction of H+ into H2. |
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The main problem I foresee is that the temperature of the water would decrease every time it re establishes equilibrium. However, this could be remedied if some form of waste heat or solar heat was applied to the water (just enough to keep the temperature stable, but the hotter the better obviously.) |
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Hey, would it work if a permanent magnet was positioned with the field running perpendicular to water flow; then the Hydronium and Hydroxide ions would be forced in opposite directions allowing for their separation. This may save more energy. |
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Alternatively: If (slightly more than) 0.4V was applied directly to pure water, would the electrolysis of Hydronium and Hydroxide take place ? The electrolysis of water certainly wouldn't. |
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The inefficiencies would serve to maintain temperature and there would be no energy required to separate the ions. |
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No again, alas. If you're not getting an efficiency
advantage, then you can't win. Thermodynamics is
unforgiving. |
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If you want to go from H20 to hydrogen and water, you
need to put in a finite and very precisely known amount of
energy, and it doesn't matter what route you use (aside
from efficiency issues). If there were a "shortcut" to do
the same reaction for less energy input, then you'd have a
free cycle which would generate net energy - also known
as perpetual motion. |
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One thing: don't forget the fact that voltage is not the
same as energy. Also, don't forget that if you do things
like flowing the water past a magnet, any energetic
advantage you get as a result will be exactly balanced by
the force on the flow, and therefore by the extra energy
needed to pump the water past the magnet. |
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This isn't an example of perpetual motion. The dissociation of water into hydroxide and Hydronium occurs because of the heat energy in the water. These ions, which have been given a higher energy can be electrolyzed with less voltage than pure water as they have gained enough energy (from the atmosphere or otherwise) to dissociate. Therefore, Hydroxide is a stronger reductant than water and Hydronium is a better oxidant than water. |
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If you want proof, take a glance at an electrochemical series. |
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Hmmm - OK, fair point. I still have a feeling that this won't
work, in that you're going to use as much energy pulling the
ions out as you would to electrolyse water. However, I can
see that you're not claiming perpetual motion, so that's
better. Still no, but no bone from me. |
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How about my alternate suggestion in which the small voltage was applied directly to water? Even impure/salty water- what other reactions could occur with 0.4V ? |
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Wouldn't you just be adding free electrons .
How many 'free electrons' are there in water anyway ? |
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No, that's not what would be happening at all... electrons are being pulled from Hydroxide (oxidation), and being pumped into H+ (reduction). |
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they're ions naturally present in any sample of water ... at 25oC it's 10^-7 mol per litre, and this amount increases with tempreature. |
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