What is r.o. technology? what is it's priciple?
how it is used to purify water?
eg of osmosis& diffusion
Answer:
RO stands for reverse osmosis
Technology and Principle:
Reverse osmosis is a separation process that uses pressure to force a solvent through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. This is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration when no external pressure is applied. The membrane here is semipermeable, meaning it allows the passage of solvent but not of solute.
- diffusion?
In RO there is pure diffusive mass transfer through the membrane. But it is different from ordinary diffusion processes. In ordinary diffusion (eg. dialysis) the driving force of the mass transfer is a concentration gradient, and the mass transfer occurs to even out this gradient. To understand diffusion in RO you need a more general approach to diffusion. It says that driving force of diffusion is an gradient in chemical potential. Since the chemical potential depends on concentration, pressure, temperature etc. there are other gradients which can force diffusion. Therefore can force diffusion against concentration gradient by a sufficient high gradient. So in RO water is forced by a pretty high pressure gradient to diffuse against its concentration gradient through the membrane.
- purification of water.
Most of the applications of RO are in purification of water, either purification of process water and potable water or waste water treatment.
The principle in both cases is the same. The unwanted substances in raw water are rejected by the membrane.
Thus RO-processing of impure leads to water of high purity as permeate and a concentrated solution of impure water as retentate.
For more details see the wikipedia article below. I think it gives a good overview to the topic.
Find on :
http://en.wikipedia.org/wiki/diffusion...
and on
http://en.wikipedia.org/wiki/osmosis...
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