Reverse osmosis (RO) is a membrane- technology filtration method that removes many types of large molecules and icon from solutions by applying to the solutions when it is on one side of a selective membrane. The result is that the solute is that the is retrained on the pressurized side of the membrane and the pure solvent is allowed to pass to other side. To be “selective” this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solutions (Such as the solvent) to pass freely.