Reverse osmosis (RO)
is a water purification method that uses a semipermeable membrane to remove ions, molecules, and sediments
from water to make it drinkable. In reverse osmosis process, pressure applied
with pump to overcome osmotic pressure.
Reverse osmosis can remove many types of dissolved and suspended particles or
species from water, including bacteria, sediments etc. and is used in both
industrial processes and the production of potable water. The
result is that the solute is
retained on the pressurised side of the membrane and the pure solvent is
allowed to pass to the other side of the membrane. To be selective, this
membrane should not allow large molecules or ions through the pores or
holes, but should allow smaller components of the solution such as solvent
molecules to pass freely.
In the normal osmosis
process, the solvent naturally moves from an area of low solute concentration
or high water potential through a membrane, to an area of high solute
concentration or low water potential. The driving force for the movement of the
solvent is the reduction in the free energy of the system when the difference
in solvent concentration on either side of a membrane is reduced, generating
osmotic pressure due to the solvent moving into the more concentrated solution.
Applying an external pressure to reverse the natural flow of pure solvent,
thus, is reverse osmosis. The process is similar to other membrane technology
applications. However, key differences are found between reverse osmosis and
filtration. Reverse osmosis also involves diffusion,
making the process dependent on pressure, flow rate, and other conditions.
Reverse osmosis is most commonly known for its use in drinking water purification from seawater,
removing the salt and
other effluent
materials from the water molecules.
