Electrohydrodynamics

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Introduction

Electrohydrodynamics (like electroaerodynamics and electroaetherdynamics; are a special case of electrosolvumdynamics) is water moving due to an electric charge. It can be used for water pumping and all the typical uses of water pumping including propulsion, well pumps, creating passive oases, water filtration and passive filtration like reverse osmosis, etc. Triboelectricity can be used to create this potential difference (voltage). This is likely the principle in which the pyramids of egypt worked on. The pyramids pumped water up from the nile water table, and was used for irrigation then back into the nile. [1] This phenomenon tends to produce alkaline water (since OH- is reformed) and could have curative benefits [2] also can possibly help promote antibacterial producing streptomyces bacteria in the water.

Basics

This video is a good example of how to set up such a device [3]. Here are the references of the video [4], [5], [6], [7]. Also see Pollack paper that talks about EZ water (OH- water is structured) [8]

In essence you have a porous dielectric, and porous electrodes in a tube in a line.

How it works

Thanks to Johan Nygren's help

Basically what is happening is water is broken down on the left (primarily by the high voltage) into H+ and OH-. Next the OH- is collapsed into oxygen, water, and releases electrons. These electrons go through a circuit and they are deposited on the right side which uses up water and oxygen to create OH- using these electrons. Since it is using water up, water is sucked through the membrane from left to right. This is how the water moves.

Catalysts

As we can see in the above, producing H2 is a loss for our system and this is why Ammonium hydroxide (added to one or both sides) helps increase the pumping more. Water is attracted to the right side to complete the creation of OH-. Also oxygen outgassing is a loss as well. So if there are a lot of bubbles forming, we probably won't get much water movement. Adding oxygen to the mix (potentially as peroxide) might help as well, just like the hydroxide. Ammonium hydroxide would likely be best so you have no permanent cations in the solution. Of course preventing this from diffusing through the membrane will help, but making the membrane too restrictive to flow would obviously restrict flow. A balance is needed. Hydroxide looks like it will help mostly the left side of the reaction, in the left side it pushes the reaction to create the products, and on the right it pushes the balance back to the reactants which we don't want. Also hydroxide will remove H+ from the left side of the system, improving efficiency.

Oxygen apparently will only help the right side, as on the left side it would push the reaction back to the reactants, but on the right side it pushes the reaction to the products. Removing oxygen from the left, perhaps with degassing, and pumping it to the right via an external mechanism, would probably be best.

Of course returning the hydroxide formed on the right, back to the left would also be ideal, but that would be difficult to do. Of course we could acidify the right which would pull the reaction forward, however electrons would be wasted converting these H+ into H2 gas. So if we did acidify it, we would also need to add H2 to push that hydrogen reaction backwards. Any other cation that can remove OH- from the system, while not bieng easily reduced by the electrons, can improve efficiency if added to the right side. In practice these cations might be insoluble so they can't be reduced by the electrons. For example filling the right side with crushed shells (calcium carbonate) might be a great way to remove some OH from solution, producing CO2 and calcium hydroxide. Along that same vein, packing the left side with sand would also be good to help remove H+, since it has a negative charge.

Of course removing water from the right side will also help pull the reaction forward, improving efficiency. This includes using an absorbant or adsorbant of the water of some sort, which can be chemical, physical, electrical, or anything else. Heat might also be used.

Calcium Chloride [9] might be a "best of both worlds" additive to the right side. It is hydroscopic which would mean it would reduce free water on the right side which we want causing more water to be pulled from the left causing movement. But also it would neutralize the OH- produced on the right side creating insoluble CaOH which can be removed (settled out) as it builds up since it would suck up oxygen gas from the H2O2 added instead of it bieng used in the reaction.

For practicality an easy way to improve efficiency would to be to add something like ammonium hydroxide, or ammonium silicate, or a combo of ammonium hydroxide and a silica source, to the left side of the cell (and prevent it from moving across the dielectric if possible) and degass the oxygen from the solution. Adding water to this side (condense) helps.

On the right side best to add hydrogen peroxide or sparge air or oxygen into the along with adding calcium chloride which removes OH- and absorbs water. Heat can also be added to the right side to improve efficiency by removing water (evaporate) or any other method to remove water.

Membrane

A packed bed of dielectric, perhaps barium titanate crystals or another super dielectric, would likely be best. It doesn't have to be sintered, but can be.

Sand would also be an easy dielectric membrane. Chemically modifying the sand or adding other ingredients can also be done, to make it more polarizable (increasing dielectric constant) or any other purpose.

Comparison with electrolysis

This is very similar to how electrolysis works [10] but in that case there are too many solutes and the water is destroyed rather than moving.

Electrical considerations

There is no net gain of electricity, all the power goes into movement. You liberate 4e- on the positive side, and the 4e- gets used up on the negative side, in an ideal system. Any O2 or H2 being produced (more specifically;leaving the system) means some of the energy is not going into movement.

Use as a generator

This process also has some potential as a generator. But simply pushing water and expecting to gain electricity is far fetched since only one part of the reactions, H2O, is moving. However pressure effects can create favoring of OH- since it is closer packed, which can push H+ to the other side [11]. Combined with a "wire" connecting the two sides, electrons can flow from left to right (creating electricity) and produce H2 gas on the right.

But to generate usable power you will likely want the extra catalysts from the catalyst section which basically might create a tribocharging effect of each electrode, for example the crushed shells on one side and sand on the other.

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