Reverse osmosis is one of the processes that removes salt from seawater. Reverse osmosis uses a membrane under pressure to separate relatively pure water (or other solvent) from a less pure solution.
What's Osmosis?
Osmosis is a natural process. Osmosis is the passage or diffusion of water or other solvents through a semipermeable membrane that blocks the passage of dissolved solutes [source:Encyclopedia Britannica].
osmosis is when a solvent of low concentrated solute solution moves through a membrane to get to the higher concentrated solution.In reverse osmosis, the filter separates out solute from solvent, just reversing the process.
How Reverse Osmosis Works
Reverse osmosis uses a membrane under pressure to separate relatively pure water (or other solvent) from a less pure solution.The largest and most important application of reverse osmosis is the separation of pure water from sea and ground water
When two aqueous solutions of different concentrations are separated by a semi-permeable membrane, water passes through the membrane in the direction of the more concentrated solution as a result of osmotic pressure. If enough counter pressure is applied to the concentrated solution to overcome the osmotic pressure, the flow of water will be reversed. (This takes about 50-60 bars of pressure [source: Lenntech].
Reverse Osmosis Membrane is Made Of
The majority of the commercially manufactured Reverse O smosis (RO) membranes are usually made from cellulose acetate, polysulfonate, and polyamide. The membrane consists of a skin about 0.25 microns and a support layer about 100 microns. The skin is the active barrier and primarily allows water to pass through.
Quality of Reverse Osmosis Product Water
The amount of dissolved solids in water produced by reverse osmosis is approximately a constant percentage of those in the feed water. For example, when the feed water contains 300 ppm total dissolved solids (TDS), the product water may have 15 to 30 ppm (95% and 90% rejection ratio respectively). A RO system design is based on a certain range of feed water TDS, the percentage of rejection and percentage of recovery desired. For a given system, the higher the percentage of recovery or the lower the percentage of rejection, the poorer the quality of product water becomes. The video below shows a Reverse Osmosis Electrolysis Demonstation.
