In this article, you will learn the definitions of osmosis and reverse osmosis, how they work, and the differences between them.
What is Infiltration?
Osmosis is a physical phenomenon. When two waters containing different salt concentrations are separated by a semi-permeable membrane, it will be found that the side with less salt will penetrate the membrane into the water with higher salt content, while the salt contained in it will not penetrate, thus gradually bringing the salt concentration on both sides to an equal level. This process is called natural osmosis, or osmosis for short.
Osmosis refers to the phenomenon that water molecules or other solvent molecules pass through a semipermeable membrane from a low-concentration solution into a high-concentration solution when two solutions of different concentrations are separated by a semipermeable membrane (a membrane that allows solvent molecules to pass through but does not allow solute molecules to pass through). Or the phenomenon that water molecules move from the side with high water potential to the side with low water potential through a semipermeable membrane.
How Infiltration Works
The phenomenon of water molecules moving from a system with high water potential to a system with low water potential through a semipermeable membrane is called osmosis. The specific process of osmosis is as follows:
- Water molecule diffusion: Water molecules move from places with high free energy (usually places with low solute concentration) to places with low free energy (places with high solute concentration). This diffusion is from places with high vapor pressure to places with low vapor pressure.
- Osmotic pressure: The pressure generated by osmosis is called osmotic pressure. When the solvent enters the solution through a semipermeable membrane until equilibrium is reached, the pressure difference on both sides is called the osmotic pressure of the solution.
- Dynamic equilibrium: When the water molecules enter and exit to reach dynamic equilibrium, the concentration of the solution in the long-necked funnel is still higher than the concentration of the liquid in the beaker.
What is Reverse Osmosis?
Reverse osmosis is a membrane separation technology that purifies water by filtering out ions, molecules, and particles in water through a specially made semi-permeable membrane. In reverse osmosis filters, water is passed through an impermeable membrane to remove impurities and inorganic salts, resulting in purer water.
How Reverse Osmosis Works
A membrane that is selective for the substances that pass through is called a semipermeable membrane. Generally, a membrane that can only pass through solvents but not solutes is called an ideal semipermeable membrane.
When the same volume of dilute solution and concentrated solution are placed on both sides of the semipermeable membrane, the solvent in the dilute solution will naturally pass through the semipermeable membrane and spontaneously flow to the concentrated solution side. This phenomenon is called osmosis.
When the osmosis reaches equilibrium, the liquid level on the concentrated solution side will be higher than the liquid level of the dilute solution by a certain height, that is, a pressure difference is formed, which is the osmotic pressure. The magnitude of the osmotic pressure depends on the inherent properties of the solution, that is, it is related to the type, concentration, and temperature of the solution but has nothing to do with the properties of the semipermeable membrane.
If a pressure greater than the osmotic pressure is applied to one side of the solution, the flow direction of the solvent will be opposite to the original osmotic direction, and it will begin to flow from the concentrated solution to the dilute solution side. This process is called reverse osmosis.
Reverse osmosis is a reverse migration movement of osmosis. It is a separation method that separates the solute in the solvent from the solvent under pressure without the help of the selective interception of a semipermeable membrane. It has been widely used in the purification and dissolution of various solutions. The most common application example is in the water treatment process, using reverse osmosis technology to remove impurities such as ions, bacteria, viruses, organic matter and colloids in water to obtain high-quality pure water.
Advantages of Reverse Osmosis
- Removal of pollutants: Reverse osmosis technology can remove harmful substances such as dissolved substances, colloids, microorganisms, etc. in water, thereby improving the quality and purity of water and achieving the purpose of safe drinking water.
- Save water: Reverse osmosis technology utilizes wastewater from traditional tap water treatment and realizes the reuse of water resources, thereby reducing water consumption and having the advantage of saving water.
- Easy to operate: The operation of reverse osmosis technology is very simple. If you choose the ITEHIL UK reverse osmosis water filter, you only need to follow the installation instructions and a few steps to complete it.
What is the Main Difference Between Osmosis and Reverse Osmosis?
The main difference between osmosis and reverse osmosis lies in the direction of liquid flow and the action of external forces. The following are their main differences:
Different Definitions
Osmosis: Water molecules flow through a semipermeable membrane from the side with low solute concentration to the side with high solute concentration until the concentrations on both sides are balanced.
Reverse osmosis: An artificial process that reverses the direction of natural osmosis by applying pressure to make water molecules flow from the side with high solute concentration to the side with low solute concentration, used for purification or desalination.
Different Flow Directions
The flow direction of osmosis is along the natural concentration gradient (low concentration → high concentration). The flow direction of reverse osmosis is against the natural concentration gradient (high concentration → low concentration), which requires external pressure.
The Function of a Semipermeable Membrane is Different
The function of the osmotic membrane is to allow water molecules to pass through, but prevent solutes (such as salt) from passing through. The function of reverse osmosis membrane is that the semipermeable membrane forces the separation of solutes and solvents under pressure to obtain pure water.
Different External Force Requirements
Osmosis does not require external force and relies on the natural diffusion process. Reverse osmosis requires additional pressure (usually provided by a pump) to overcome the natural osmotic pressure.
Different Application Scenarios
The application scenarios of osmosis mainly include natural phenomena such as cell water absorption in biology and plant root nutrient absorption. Reverse osmosis is mainly used in water treatment systems (such as water purifiers, and industrial pure water preparation) and wastewater recycling.
Why is Reverse Osmosis Better Than Osmosis?
The reason why reverse osmosis is better than osmosis is that it can reverse the natural osmosis process to achieve deep purification and separation of liquids. The specific reasons are as follows:
Purification Ability
Reverse osmosis uses pressure to force water molecules from a highly concentrated solution through a semipermeable membrane, filtering out impurities such as dissolved solids, bacteria, viruses, and heavy metals. This filtration accuracy is much higher than ordinary osmosis or other physical purification methods, and very pure water can be obtained.
Osmosis can only occur naturally and cannot selectively remove specific impurities. Reverse osmosis has a removal rate of up to 90%-99% and is particularly effective for heavy metals and dissolved salts.
Highly Efficient Selective Filtration
When permeated water molecules pass through the membrane, they do not distinguish between solutes and water molecules, so the filtration effect cannot be achieved. The pore size of the reverse osmosis membrane is less than 0.0001 microns, which only allows water molecules to pass through, while most impurities and pollutants cannot pass through.
Adaptability to Pollution
Osmosis cannot withstand high-concentration pollution environments, and impurities will accumulate in the water. Reverse osmosis is suitable for treating highly polluted or high-salinity water sources.
Wide Range of Application Scenarios
Osmosis is only applicable to specific natural conditions, such as ecosystems such as plant water absorption. Reverse osmosis can be applied under external pressure, has a wider range of applications, and can be controlled artificially.
FAQ
Which is Better Alkaline or Reverse Osmosis?
Alkaline water is believed to help neutralize acidity in the body due to its higher pH value, but it is generally not effective in removing heavy metals and other pollutants. Reverse osmosis water, on the other hand, removes up to 99% of harmful substances (such as heavy metals, bacteria, and chemical pollutants) through precision filtration technology, providing pure drinking water.
Is Reverse Osmosis Water Good or Bad?
Reverse osmosis can remove heavy metals, bacteria, viruses, and other harmful substances from water. Therefore, reverse osmosis water is good water. However, because the reverse osmosis process removes minerals, many people worry that its low mineral content may affect their health. You can supplement the minerals needed by the human body through diet.
Is RO Water the Same as Distilled Water?
RO water and distilled water are both pure water. However, they have different characteristics. RO water retains some dissolved gases and tastes fresher. Distilled water may take away dissolved gases and taste slightly bland. In life, RO water is generally more suitable for daily drinking, while distilled water is mainly used in medical treatment, laboratories, etc.
