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Reverse Osmosis

Reverse osmosis (RO) is a separation process that uses pressure to force a solvent through a membrane. Impurities in the solvent are excluded, whilst pure solvent passes through the membrane. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. This is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low solute concentration to an area of high solute concentration through a membrane, without the application of external pressure. The membrane is semipermeable, meaning that it allows the passage of solvent but not of solute.

The membranes used for RO have a dense barrier layer in the polymer matrix where most of the separation occurs. In most cases the membrane is designed to allow only water to pass through this dense layer while preventing the passage of solutes such as ions. This process requires that a high pressure be exerted on the high concentration side of the membrane, usually 2-17 bar (30-250 psi) for fresh and brackish water, and 40-70 bar (600-1000 psi) for seawater, which has around 24 bar (350 psi) natural osmotic pressure that must be overcome in order to achieve the RO.

The best known applications for the RO process is in desalination, where fresh water is generated from seawater by removing the salt. However, there are numerous other applications in the chemical, pharmaceutical and food industry, as well as in effluent and waste treatment applications.

Please click here to contact Esmil for Reverse Osmosis Services.