What is Reverse Osmosis?

Diffusion is defined as the process where in the molecules move from a region of higher concentration towards a region of lower concentration. A special case of diffusion is nothing but the Osmosis, where in water molecules move across a semi permeable membrane due to the concentration gradient. This semi permeable membrane permits only the flow of water molecules but not the ions and the larger molecules such as bacteria, glucose etc.

Both the osmosis and diffusion processes continue until equilibrium is attained.

Osmosis process can be stopped or even can be reversed slowly by applying pressure on the membrane from the concentrated side of the semi permeable membrane.

How Reverse Osmosis Work?

In reverse Osmosis, what happens is the reverse movement of the water molecules viz… The molecules move from the region of lower concentration towards the region of higher concentration across the semi permeable membrane against the concentration gradient.

To illustrate the entire process: imagine fresh water and a concentrated solution are separated by a semi-permeable membrane being at the centre. In normal conditions, the fresh water molecules move across the membrane to enter the concentrated solution to dilute it. But when reverse osmosis is tried, that is applying a little pressure on the side with the concentrated solution to make the water molecules to cross through the membrane to reach fresh water side.

Reverse Osmosis is employed in residential water filtration and also for commercial purposes. It is used in cases where there is a need to purify the liquids in which water will be an undesirable impurity. It is also used to desalinate seawater.