Reverse osmosis

Reverse osmosis (RO) is a water purification technology that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential differences of the solvent, a thermodynamic parameter.

Process

Reverse osmosis can remove many types of dissolved and suspended chemical species as well as biological ones (principally bacteria) from water, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective", this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as solvent molecules, i.e., water, H2O) to pass freely.

Applications

In the production of drinking water, reverse osmosis is most commonly used to purify seawater into potable water. However, it is also used in industrial processes to purify and recycle water, and to concentrate and separate dissolved substances. Reverse osmosis is also becoming increasingly important in the food and beverage industry, in the dairy industry for the production of whey protein concentrates and isolates, and in the production of maple syrup.

See also

• Desalination
• Osmosis
• Water treatment