Osmostic Perpetuation: Why does it not work?

[Zygy]

I have two questions:

 

(1) One way to go about water purification is through reverse osmosis. Some sort of pump is used to apply a pressure on the reverse osmosis membrane. Is it possible to use osmotic pressure to act like the pump? An example is a system that has distilled water and the solution that needs to be purified in a tube separated by a semi-permeable membrane that only lets water pass through. There is a second membrane that closes off the solution (The solution is contained between the two membranes). There is an empty tube on the other side of this membrane. Will the distilled water create enough pressure build up in the space contained between the two membranes as it passes through the first membrane to act like a pump and force pure water out of the second membrane?

 

If this can happen . . .

 

(2) This is the perpetual loop scenario. Basically it is the same as the previous scenario except take the tube and loop it around so that it forms a closed loop. The system will have to be tilted up or modified in other ways so that distilled water does not touch both membranes. The easiest scenario to visualize, at least for me, is a U-tube with one of the sides being longer; so closer to a "J" shape. The long side slants back down to the short side. There is a membrane at the bottom of the tube and at the top of the long side. Distilled water is on the short side and the solution is on the long side. There is air in the the slant back down. If the osmotic pressure can cause reverse osmosis in the top membrane, then pure water would trickle back down to the distilled water side perpetuating the process. This should not happen. If anyone can explain to me what causes the system to equilibrate and why, I will be grateful.

 

Thank you.

If need be I can insert an image of the system.