Reverse osmosis is among the procedures driven by pressure.

Reverse osmosis (RO) is used for separation of salts or ions from principally hydrous solutions. RO is used for the increased concentration of solutions as well as for the separation of aqueous components.

For this process, a semi-permeable membrane is used. It has the characteristic that the aqueous components pass through the membrane, while most of the ionic components are retained to a high extent.

The semi-permeable membrane is a solution diffusion membrane. In contrast to a pore membrane used in microfiltration or ultrafiltration, the solution diffusion membrane has no pores. The separation effect results rather from the charge carriers of the membrane and the resulting attraction and repulsion by the electrical charge. As a result, the permeating components basically pass through the membrane in three steps:

  • Absorption at the membrane
  • Diffusion through the membrane
  • Desorption from the membrane