Desalination of seawater is done by using reverse osmosis. The pressure applied to the solution is

Reverse osmosis is a water purification process that reverses the natural flow of solvent through a semi-permeable membrane. In natural osmosis, water moves from a region of low solute concentration to high solute concentration. To reverse this process for desalination, external pressure must be applied to the concentrated solution (seawater). This applied pressure must be larger than the osmotic pressure of the solution to overcome the natural osmotic flow and force pure water molecules through the membrane, leaving salts behind. While the provided snippets discuss pressure gradients in the context of meteorology [2] and vapor pressure changes due to salinity , the chemical principle of reverse osmosis specifically dictates that the driving force must exceed the osmotic pressure to achieve desalination. This ensures that the chemical potential of the solvent in the saline solution becomes higher than that of the pure solvent, facilitating the reverse flow.

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 24: Hydrological Cycle (Water Cycle) > Factors Affecting Rate of Evaporation > p. 329