Reverse Osmosis & Water Purification Notes | Study Additional Documents and Tests for JEE - JEE

REVERSE OSMOSIS AND WATER PURIFICATION
The direction of osmosis can be reversed if a pressure larger than the osmotic pressure is applied to the solution side.
That is, now the pure solvent flows out of the solution through the semipermeable membrane. This phenomenon is called reverse osmosis and is of great practical utility.

• Reverse osmosis is used in desalination of seawater.
  
• When pressure more than osmotic pressure is applied, pure water is squeezed out of the sea water through the membrane.
• A variety of polymer membranes are available for this purpose. A schematic set up for the process. 
• Reverse osmosis occurs when a pressure larger than the osmotic pressure is applied to the solution.
• The pressure required for the reverse osmosis is quite high. 
• A workable porous membrane is a film of cellulose acetate placed over a suitable support. 
• Cellulose acetate is permeable to water but impermeable to impurities and ions present in sea water. These days many countries use desalination plants to meet their potable water requirements.