Reverse Osmosis

Reverse osmosis is a filtration method removes many types of large molecules and ions from the solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective," this membrane should not allow large molecules or ions through the holes, but should allow smaller components such as the solvent to pass freely.
Reverse osmosis is most commonly known for its use in purify seawater into drinkable water.