Principle of Osmotic pressure and Reverse Osmotic Pressure

Osmosis is a phenomenon that the solvent of the solution at the lower solute concentration moves to the solution at the higher solute concentration through a semi-permeable membrane, which separates the two solutions. The osmotic pressure means the difference in the level of solutions when the solvent movement stops or when the chemical potential of the two solutions gets equal.

The reverse osmosis is a phenomenon that if a pressure greater than the osmotic pressure is applied to the solution side at the higher solute concentration, the solvent of the solution at the higher solute concentration moves to the solution at the lower solute concentration.

The actual reverse osmotic pressure shall be twice the osmotic pressure, which is calculated by the following equation.