Reverse osmosis belongs to the processes which are driven by differential pressure.
Reverse osmosis is normally used to separate salts respectively ions out of aqueous solutions. So, it can be used to concentrate the contents or to separate the aqueous component.
For the reverse osmosis, a semipermeable membrane is used. Through this membrane, aqueous components can pass, but the most ionic components are retained.
The semipermeable membrane is a solution diffusion membrane. Compared with a pore membrane, which is used for micro or ultra filtration, the solution diffusion membrane has no pores. The separation effects base on charge carrier and the resulting attraction and rejection because of the electrical charges. Components which are able to pass the membrane, will do it in three steps: absorption at the membrane, diffusion through the membrane and desorption of the membrane. Ions will be retained because of the equal charge of ion and membrane.
So, polar components like water or other polar solvents obtain a high flow rate through the membrane; bigger charged ions will be retained.
For example, the rejection of table salt is 97% - 99,5%. The rejection varies depending on the type of membrane but also on the medium. For a lot of mixtures, previous laboratory examinations and sometimes pilot plants are indispensable for a technical realization. Hereby, OSMO Membrane Systems is a reliable partner for all steps of the project, so that a suitable membrane can be found for nearly all applications.