Reverse or reverse osmosis is a process of separating substances through a membrane that retains the solute.
In this case, the solvent flows from the most concentrated medium to the least concentrated and is isolated from the solute by a membrane that allows it to pass.
It is, therefore, a process opposite to what occurs naturally during osmosis, where water flows from a less concentrated (hypotonic) medium to another more concentrated (hypertonic) medium.
In reverse osmosis, the solute is forced to pass to the less concentrated medium. This is only possible thanks to the pressure exerted, making the semipermeable membrane allow only the passage of water, retaining the solute.
However, for this to happen it is necessary to apply a pressure higher than the natural osmotic pressure.
During reverse osmosis, up to 99% of low molecular weight solutes such as salts or simple organic molecules are retained. Bacteria, viruses and other types of dissolved solids can also be isolated, purifying the water.
applications
The greatest use of reverse osmosis is for the desalination of sea water. This is an important procedure to solve the problem of lack of drinking water in some parts of the world.
To carry out desalination, a pressure higher than the natural osmotic pressure is applied, this is achieved through motors. Thus, the semipermeable membrane retains the solute, separating the salt from the water.
It is worth mentioning that microorganisms are also eliminated from the water, making the water pure.
Reverse osmosis is also widely used in industries. Among other applications are:
- Irrigation: the salts present in the water are retained, preventing the accumulation of these substances in the soil;
- Hemodialysis machines: the process filters the blood and retains impurities.
- Manufacture of beverages, such as some types of mineral water.