Reverse Osmosis: Definition, Process, Uses, Working of Reverse Osmosis

What is Reverse Osmosis?

Reverse osmosis (RO) is somewhat of an up-to-date separation technique majorly applied to water purification. RO primarily involves forcing water through a semipermeable membrane to remove dissolved solutes. It is particularly very effective in seawater desalination and drinking water purification. This process became more effective with the development of membrane technology and the science of polymers, thus turning it into one of the important tools for residential and industrial applications. The working principle or the mechanism, advantages, and some limitations of reverse osmosis are overviewed here to understand this important technology in some detail.

Principle of Reverse Osmosis

The reverse osmosis process relies on a semipermeable membrane, where significantly only the solvent molecules are easily allowed to pass through while blocking larger solute molecules. During the process, the pressure applied to the solution side of the membrane ensures that the solvent molecules move through to the side with a lower concentration of the solutes. This finally leads to the separation of solutes from the solvent, hence purification.

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Process of Reverse Osmosis

The process of reverse osmosis has the following distinct steps associated with it:

• Pressure Application: Pressure applied on the solution side is increased to a value above the osmotic pressure, which is the minimum pressure required to halt the flow of the solvent across the membrane.

• Solvent Movement: Due to this elevated pressure, the solvent molecules move through the semipermeable membrane to the lower concentration side of the solute particles.

• Separation and Purification: What happens is that the solute particles get separated from the solvent, which becomes purified.

This process works effectively when pressure is applied that is greater than the osmotic pressure and on flow in the proper direction of the solvent.

Reverse Osmosis Experiment

An illustrative experiment would do well to explain reverse osmosis:

• Assembly: Take two containers, with a semipermeable membrane in between, one containing fresh water, and another containing a solution of high concentration.

• Application of Pressure: Apply pressure to the concentrated solution side.

• Result: Due to this, water molecules diffuse through the membrane into the freshwater side, thereby explaining the concept of reverse osmosis.

This simple experiment is a good example of how reverse osmosis works in a closed environment.

Advantages of Reverse Osmosis

Some of the advantages associated with reverse osmosis are enumerated below:

• Thorough decontamination: Efficiently removes different dissolved and suspended particles, including salts, chemicals, and microorganisms.

• Wide applications: The technology ranges from desalination of seawater and industrial liquid wastes to drinking water purification.

• Health benefits: This technology provides clean water and hence saves customers from waterborne diseases.

These advantages combine to make reverse osmosis an extremely useful technology both in the home and industrially.

Disadvantages of Reverse Osmosis

Despite all of the advantages, there are some reverse osmosis limitations:

• Membrane Sensitivity: The various types of membranes used have varying tolerances to pH and temperature. For example, cellulose acetate membranes can not withstand high temperatures above 35°C, while polyamide membranes do not have good resistance to chlorine.

• Maintenance Requirements: Membranes need periodic replacement. Sterilization of the system has to be done regularly to ensure efficiency.

• Wastewater: In this process, a lot of wastewater is generated. This can create certain misgivings about the use of reverse osmosis in places where there are limited sources of water.

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