Reverse Osmosis Membrane: A Miracle of Highly Selective Permeability

In the vast field of water treatment technology, RO membrane is undoubtedly a shining pearl. With its unique structural characteristics and excellent performance, it has become a key tool to solve the problems of water shortage and water purification. Behind the seemingly simple RO membrane, there are complex scientific principles and exquisite manufacturing technology. The core lies in its exquisite design carefully constructed by a multi-layer structure.

Synergy of Multi-layer Structure
Reverse osmosis membrane is not a simple stacking of a single material, but a complex system carefully composed of three major parts: support layer, transition layer and separation layer. Each layer has a specific function and works together to achieve efficient water purification.

Support layer: As the foundation of the RO membrane, the support layer not only provides the necessary mechanical strength for the entire membrane structure, but also ensures the stability of the membrane under high pressure. It is like a solid cornerstone, supporting the finer layers above, enabling it to resist the impact of water flow and the influence of the external environment.
Transition layer: Located between the support layer and the separation layer, the transition layer acts as a bridge. It optimizes the structural gradient inside the membrane, allowing water to flow more smoothly, and also helps to improve the membrane's anti-fouling performance. The presence of the transition layer allows the reverse osmosis membrane to have better durability and easy cleaning while maintaining efficient separation capabilities.
Separation layer: This is the core of the reverse osmosis membrane and the key to achieving water purification. The separation layer has extremely small pore sizes (usually around 0.1nm), which are much smaller than the sizes of most soluble solids and ions, but are sufficient to allow water molecules (molecular diameter is about 0.4nm) to pass freely under pressure. This unique pore structure gives the reverse osmosis membrane a high degree of selective permeability, which can accurately separate impurities in the water from pure water.
The secret of selective permeability
The selective permeability of the reverse osmosis membrane is one of its most praised characteristics. Under the action of external pressure, water molecules can overcome the natural osmotic pressure and pass through the tiny membrane pores to enter the low-pressure side, while impurities such as soluble solids, ions, bacteria, and viruses are effectively retained on the high-pressure side. This process seems simple, but it actually contains profound physical and chemical principles.

The polarity and small molecular properties of water molecules enable them to pass through the membrane pores more easily. Water molecules are connected to each other through hydrogen bonds to form a continuous network structure, which enables water molecules to migrate collectively when under pressure, thus passing through the membrane pores smoothly.

The sieving effect of the membrane pores is also an important factor in achieving selective permeability. Since the pore size of the membrane pores is much smaller than the size of most impurities, only molecules or ions smaller than the pore size can pass through. This sieving effect ensures that the reverse osmosis membrane can efficiently separate impurities from pure water.

With its unique multi-layer structure and high selective permeability, the reverse osmosis membrane has shown extraordinary potential and value in the field of water treatment. It can not only effectively remove impurities such as dissolved solids, ions, bacteria, viruses, etc. in water, improve water quality standards, but also achieve water conservation and recycling. With the continuous advancement of science and technology and the improvement of manufacturing processes, the performance of reverse osmosis membranes will be more superior and the scope of application will be wider. In the days to come, reverse osmosis membranes will continue to contribute to the protection of human water resources and sustainable development.