Reverse osmosis is a filtration process that is often used for water. It works by using
pressure to force a solution through a membrane, retaining the solute on one side and
allowing the pure solvent to pass to the other side. This is the reverse of the normal
osmosis process, which is the natural movement of solvent from an area of low solute
concentration, through a membrane, to an area of high solute concentration when no
external pressure is applied.