Reverse Osmosis Process Explained
Reverse osmosis refers to the process of separating dissolved solutes from the water. The semipermeable membrane is used for the reverse osmosis process. It is because water molecules can pass from this membrane, but the majority of bacteria, dissolved salts, pyrogens, and organics are not allowable. The reverse osmosis process is widely used in the purification of drinking water due to its property of removing salt and other waste materials.
What do Students Mean by Reverse Osmosis?
The water found in the oceans comprises salt, bacteria, and large particles. It makes water unsuitable for the human to use. However, with reverse osmosis technology, removing all the contaminants from the water makes it fit for use.
According to reverse osmosis definition class 12, reverse osmosis is a type of filtration technique. The process is useful for the removal of unwanted ions or molecules from a specific solution. The pressure more than the osmotic pressure is practised to the solution present on one side of the intact membrane. It causes the passage of pure solvent through the membrane.
Principle of Reverse Osmosis Process
The reverse osmosis process includes the application of pressure on one side of the solution. The semipermeable membrane used in the process is placed in between the solutions. Due to the presence of this membrane, large molecules present in the solute cannot pass through it. As a result, unwanted contaminants remain on the pressed side. On the other hand, the pure solvent can cross the membrane.
Consequently, the molecules of the solute start concentrating on one side of the membrane, and the other hand becomes dilute. During the reverse osmosis process, the solution levels also change to some extent.
It can be identified from the reverse osmosis definition class 12 that during reverse osmosis, the solvent moves from a lower concentration to a higher one.
Reverse Osmosis Process - Working
The process of reverse osmosis can be explained by conducting a small experiment. Two solutions are taken, freshwater, and a concentrated aqueous solution. The semipermeable membrane is placed between the two solutions taken, which separate the solutions. The pressure is applied to the end of the membrane, that is, on the concentrated solution. As a result, water molecules will start moving through the membrane. However, contaminants will remain on the aqueous solution side, and water molecules pass to the freshwater side.
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The diagram outlines the reverse osmosis process. When higher pressure is applied to the concentrated solution, the water molecules start moving through a semipermeable membrane. However, the contaminants are not able to pass through the membrane.
Benefits of Reverse Osmosis
In the treatment of liquid wastes and discharge, the process of reverse osmosis is useful.
The reverse osmosis process is useful in removing different types of suspended particles from the water. The particles can be chemical, dissolved entities, or any biological units such as bacteria.
The semi-permeable membrane blocks viruses, pyrogen, and many other substances. That is why; it is widely used as RO that purifies water by preventing the entry of bacteria.
It is beneficial in the process of desalination of seawater.
It is extensively used in medical applications like home dialysis. It is because accessible units are not only compact but require less space.
How the Process of Reverse Osmosis is Used in Everyday Applications?
Drinking Water: The reverse osmosis process requires a relatively small amount of energy. That is why; it is widely used in the desalting sea for filtered use.
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The above diagram shows that the reverse osmosis process blocks the passage of large particles and allows water molecules to pass through the membrane.
Electronics: According to reverse osmosis definition class 12, the process is useful to remove impurities in the water supply. It encompasses the life of the ion exchange ways. Additionally, the process lowers down the cost of manufacturing huge volumes of high purity water.
Chemicals: Generally, the manufacturers of chemicals need different qualities of water. The reverse osmosis process will help in manufacturing suitable water products depending on the nature of the involved production process.
Is There any Disadvantage of the Process of Reverse Osmosis?
The major drawback of the reverse osmosis process includes the reduction of good minerals also. The intact membrane does not allow the passage of large molecules. As a result, contaminants remain in the aqueous solution in which some good minerals are present. Hence, people drinking water purified by reverse osmosis can suffer from general weakness, muscle cramps, and tiredness.
FAQs on Reverse Osmosis Process Explained
1. What is the simple explanation of the reverse osmosis (RO) process?
Reverse Osmosis (RO) is a water purification process where pressure is used to force a solvent, typically water, through a semipermeable membrane from a region of high solute concentration to a region of low solute concentration. This is the opposite of natural osmosis, effectively filtering out dissolved salts, minerals, and other impurities to produce purified water.
2. What is the fundamental principle of reverse osmosis as per the CBSE syllabus?
The fundamental principle of reverse osmosis is to overcome the natural osmotic pressure of a solution. In osmosis, a solvent naturally moves from a dilute solution to a concentrated one. In reverse osmosis, an external pressure greater than the solution's osmotic pressure is applied. This forces the solvent to flow in the reverse direction—from the concentrated solution to the pure solvent side—leaving the solutes behind.
3. How does reverse osmosis fundamentally differ from standard osmosis?
The key difference lies in the direction of solvent flow and the role of pressure.
- Osmosis: A spontaneous, natural process where solvent moves from a low solute concentration to a high solute concentration across a semipermeable membrane without any external pressure.
- Reverse Osmosis: A non-spontaneous process that requires an external pressure greater than the osmotic pressure to force the solvent to move from a high solute concentration to a low solute concentration.
4. Why is a high external pressure a critical requirement for the reverse osmosis process?
A high external pressure is critical because it must counteract and exceed the natural osmotic pressure. Osmotic pressure is the minimum pressure needed to prevent the inward flow of pure solvent across a membrane. To reverse this natural flow and push solvent molecules out of the concentrated solution, the applied pressure must be sufficiently high to overcome this inherent force, enabling the separation and purification process.
5. What are the key steps involved in a typical reverse osmosis system for water treatment?
A typical reverse osmosis system involves several key steps:
- Pre-filtration: Raw water is first passed through pre-filters to remove larger suspended particles like sand, silt, and rust, which could damage the RO membrane.
- Pressurisation: A high-pressure pump increases the pressure of the feed water to a level that exceeds the osmotic pressure of the solution.
- Membrane Separation: The pressurised water is forced against the semipermeable membrane. Water molecules pass through, but dissolved salts and other impurities are blocked and flushed away as reject water or brine.
- Post-treatment: The purified water (permeate) may undergo a final treatment stage, such as UV sterilisation or re-mineralisation, to ensure it is safe and palatable for consumption.
6. What is the role of a semipermeable membrane in reverse osmosis, and what are its properties?
The semipermeable membrane is the heart of the reverse osmosis process. Its primary role is to act as a highly selective barrier. It contains microscopic pores that are large enough to allow water molecules (solvent) to pass through but small enough to block the passage of larger molecules, ions, and dissolved substances (solutes). Its key property is this selective permeability, which is what enables the separation of pure water from contaminants.
7. What are some important real-world applications of the reverse osmosis process?
Reverse osmosis has several vital applications in various fields:
- Desalination: Its most significant application is the purification of seawater or brackish water to produce fresh, potable drinking water.
- Water Purification: Used in homes and industries to produce highly purified water for drinking, laboratory use, and manufacturing processes.
- Wastewater Treatment: Helps in recycling and treating industrial and municipal wastewater by removing contaminants.
- Food and Beverage Industry: Used to concentrate fruit juices and milk (whey protein) without using heat, which preserves flavour and nutrients.
8. What are the main limitations of using reverse osmosis for water purification?
While highly effective, reverse osmosis has some limitations. The process removes both harmful contaminants and beneficial minerals like calcium and magnesium, potentially making the water demineralised. It also generates a significant amount of reject water (brine) for every litre of purified water produced. Furthermore, RO membranes are susceptible to damage from chlorine and can be clogged by bacteria or hard water minerals if the water is not properly pre-treated.
