* 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.-- Domser, Nov 19 2008 I don't think this will work.-- Spacecoyote, Nov 19 2008 How come ?-- Domser, Nov 19 2008 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.-- MisterQED, Nov 19 2008 So, the ideal fuel source for itinerant hairdressers?-- coprocephalous, Nov 19 2008 It would be tricky to make a membrane permeable only to ions.
If you are already throwing about low voltage currents why not just electrolyze the water with that?-- bungston, Nov 19 2008 No.-- MaxwellBuchanan, Nov 19 2008 //atmospheric energy//
You have sails with that?-- neelandan, Nov 20 2008 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.-- Domser, Nov 21 2008 hey MaxwellBuchanan, why "no" ?-- Domser, Nov 27 2008 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:
1) You're using energy to pull the ions out of the water in the first place. Is this accounted for?
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?-- MaxwellBuchanan, Nov 27 2008 Well to electrolyze water producing hydrogen and oxygen requires 1.23 Volts. (or more due to inefficiencies)
To Electrolyze Hydronium and Hydroxide, producing Hydrogen and water and oxygen requires 0.4 V (or more due to inefficiencies)
Would the energy required to pull these ions out and concentrate them surpass this saving ?
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.
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.)
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.-- Domser, Nov 27 2008 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.
The inefficiencies would serve to maintain temperature and there would be no energy required to separate the ions.-- Domser, Nov 27 2008 No again, alas. If you're not getting an efficiency advantage, then you can't win. Thermodynamics is unforgiving.
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.
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.
Sorry.-- MaxwellBuchanan, Nov 28 2008 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.
If you want proof, take a glance at an electrochemical series.-- Domser, Nov 29 2008 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.-- MaxwellBuchanan, Nov 29 2008 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 ?-- Domser, Dec 02 2008 Wouldn't you just be adding free electrons . How many 'free electrons' are there in water anyway ?-- wjt, Dec 02 2008 No, that's not what would be happening at all... electrons are being pulled from Hydroxide (oxidation), and being pumped into H+ (reduction).
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.-- Domser, Dec 02 2008 random, halfbakery