Reverse osmosis membrane technology has become the most important and effective technology in drinking water treatment today. It can effectively remove most pollutants in water, including bacteria, viruses, heavy metals, organic and inorganic substances, etc., to provide safe and healthy drinking water.

First of all, in order to understand the working principle of reverse osmosis membrane, we need to first understand what "osmosis" and "reverse osmosis" are.

Osmosis means that under natural conditions, when two solutions are separated by a semipermeable membrane (a membrane that only allows the solvent to pass), the solvent (such as water) will automatically move from a low concentration to a high concentration through the membrane in order to achieve concentration equilibrium on both sides. . This process will continue until the concentrations on both sides are the same. This is what we call the osmosis phenomenon.

However, reverse osmosis is the reverse process of osmosis. In the reverse osmosis process, we artificially apply a pressure on the side of the high-concentration solution. Once this pressure exceeds the osmotic pressure, the water molecules will pass through the membrane in the reverse direction, moving from the high-concentration solution to the low-concentration solution. This is reverse osmosis. Basic principles of osmosis.

Now that we understand the basic concept of reverse osmosis, the reverse osmosis membrane is a crucial part of the process. The reverse osmosis membrane is a semipermeable membrane with a very small pore size, about 0.0001 micron. This fine pore size allows water molecules to pass through, but most pollutants, including dissolved salts, organic matter, bacteria, viruses, heavy metal ions, etc., cannot pass through the membrane. In this way, when we apply pressure, the water will be filtered by the parts from the water to be treated and directed to the water outlet, while the excluded impurities will flow to the wastewater end and be effectively separated.

During actual operation, pressure is generally applied to the incoming water, causing the water quality to pass through the reverse osmosis membrane. Other ions, salts, microorganisms, etc. are mainly maintained at one end of the raw water. Only a few very small substances can pass through the reverse osmosis membrane. Clean water is then directed through a series of pipes into the home or industrial facility, while wastewater is piped out of the system.

In general, the working principle of a reverse osmosis membrane is to apply high pressure to raw water, causing water molecules to pass through the membrane and separate from pollutants, thereby purifying water quality. And all of this is accomplished by utilizing natural penetration phenomena and human control of them, which is why it can play a huge role in so many fields.

Application of reverse osmosis membrane in drinking water treatment.

Seawater Desalination: Reverse osmosis membranes are widely used in seawater desalination to convert seawater into fresh water to meet drinking needs. This is very important for islands and coastal cities that lack natural fresh water resources but are surrounded by sea water.

Wastewater treatment and reuse: Under today's severe environmental protection situation, reverse osmosis membranes are also widely used in the further treatment and purification of industrial and domestic wastewater, converting wastewater into water that can be safely drank or reused for farmland irrigation, park greening and other occasions. water source.

Bottled water and drinking water stations: Many bottled water manufacturers and drinking water stations use reverse osmosis systems to filter and purify water to meet or exceed drinking water standards set by the World Health Organization and countries, providing consumers with safe, pure of drinking water.

Household drinking water purification: Many modern households are equipped with household reverse osmosis water purifiers, which purify fresh drinking water directly from the tap water to provide healthier and more delicious fresh water.

Food and beverage industry: Many food and beverage companies that require large amounts of water in the production process, such as brewing, juice production, and soft drinks, will use reverse osmosis systems to treat and purify water to ensure the taste and purity of their products.

These are some applications of reverse osmosis membranes in drinking water treatment. Due to its excellent filtration and purification capabilities, reverse osmosis membranes are widely used, covering almost every corner of our lives.

Advantages and characteristics of reverse osmosis membrane.

Efficiently shield pollutants: The pore size of the reverse osmosis membrane is extremely small, about 0.0001 micron, which allows only water molecules and some small ions to pass smoothly. Therefore, most impurities in the water, such as heavy metal ions, bacteria, viruses, organic pollutants, and 85-99% of dissolved salts, will be intercepted by the reverse osmosis membrane, and only clean water molecules can pass through, which fundamentally guarantees The purity of the effluent water.

Wide range of applications: Reverse osmosis technology can handle all types of water resources, including fresh water, salt water, sea water, etc. As long as the size of the impurities contained in the water is outside the pore size range of the reverse osmosis membrane, it can theoretically be treated by reverse osmosis technology. Therefore, reverse osmosis technology has a very wide range of applications, whether in household water purification, industrial fields, seawater desalination, or even air humidity recovery.

Energy saving and environmental protection: Reverse osmosis is a physical filtration process that does not require the use of any chemical cassia seeds and does not require the consumption of additional fuel or electricity. Since only a little initial pump pressure is required, energy consumption during the entire filtration process is relatively low. Reflection not only reduces secondary pollution problems, but is also an energy-saving and environmentally friendly water treatment method.

The equipment is small in size and occupies less area: Compared with traditional water treatment equipment, reverse osmosis equipment has a simple structure and small size, so it requires a relatively small area. This advantage makes it particularly suitable for use in large cities, or anywhere where optimal use of space is required.

Easy to operate and easy to automate management: Another important advantage is that the reverse osmosis system is easy to operate and easy to automate management. This can greatly reduce the operator's workload while also greatly improving water treatment efficiency.

The quality of the produced water is extremely high and stable: The quality of water treated with reverse osmosis membranes is stable and can reach an extremely high level of purity, meeting the needs of a large number of industries for high-purity water.

In general, reverse osmosis membranes have many advantages such as lower pressure, lower energy consumption, small equipment size, easy operation, and high quality water production, making them widely used in all walks of life, especially in the field of water treatment. . Whether it is the purification of drinking water, the treatment of industrial water, or desalination of seawater, reverse osmosis membranes can play a great role.

Reverse osmosis membranes have strict requirements in material selection. Generally, reverse osmosis membranes are mainly made of polymer materials such as polyamide and polysulfone. Polyamide materials have the characteristics of stable performance, corrosion resistance and good filtration effect, and are suitable for various water treatment needs. Due to its excellent chemical stability, polysulfone materials can maintain a low shedding rate in environments such as acids, alkalis, and oxidants, so they are also widely used in the manufacture of reverse osmosis membranes.

Specific to the structure of the reverse osmosis membrane, it generally consists of the following three parts:

Substrate Layer: This is the bottom of the reverse osmosis membrane. It is usually made of a stable, uniform pore expansion surface, and high-strength material, such as polyimide. This layer is mainly to establish a stable structural framework for the entire membrane body, to withstand operating pressure, and to prevent the membrane body from collapsing under the impact of water flow.

Micro-porous Layer: Located between the support layer and the outermost film layer, it is a layer of porous polymer membrane. The main function of this layer is to screen macromolecular impurities, bacteria, etc. and protect the transformation layer.

Separative Layer: This is the most external and visible part of the material and the most functionally important layer. It is mainly composed of polymer materials, and its thickness is usually only tens to hundreds of nanometers. The main function of this membrane is to use the separation and filtration mechanism to allow water molecules to pass through as much as possible, and to filter out ions and harmful substances in the water.

These three layers each perform their own duties and together form a high-efficiency, high-value-added reverse osmosis membrane. It should be noted that the bonding force between the layers is also very critical, which directly determines the overall stability and durability of the membrane. Membranes that are not strong enough will separate during long-term use and lose their separation properties.

Generally speaking, the material and structural design of reverse osmosis membranes make it widely used in many fields, such as water production, wastewater treatment, seawater desalination, etc. The characteristics of this material and structure also enable the reverse osmosis membrane to maintain its excellent filtration performance in a high-pressure environment, filter out a variety of harmful substances, and provide safer and healthier water resources.

In the reverse osmosis membrane, the first or bottom layer, the support layer, is a very critical part. Generally, this layer is made of polyester non-woven fabric. Polyester non-woven fabric is a new type of non-woven fabric made from polyester as the main raw material through a series of processes such as melting, spinning, spinning, thermal bonding or chemical flocculation.

Characteristics of polyester non-woven fabrics:

Excellent mechanical properties: Polyester non-woven fabric has excellent mechanical properties and can provide good physical support for the reverse osmosis membrane to prevent deformation and damage under long-term operation and high pressure.

Uniform structure: The structure of polyester non-woven fabric is very uniform, and its fiber strength is uniform. The smoothness and uniformity of the non-woven surface have a very important impact on the coverage of the active layer and microporous layer of the support layer.

Proper control of average pore size: The size of the average pore size is not only related to the removal of impurities, but also affects the flux of water, which further affects the overall performance and use effect of the reverse osmosis membrane.

Heat resistance and corrosion resistance: Polyester non-woven fabrics also have good heat resistance and corrosion resistance, and can adapt to various complex working conditions.

Excellent bonding strength: The surface roughness of polyester non-woven fabric determines its bonding strength with subsequent materials such as reverse osmosis layer and microporous layer.

Therefore, polyester non-woven fabric, as the main supporting material of the reverse osmosis membrane, not only plays a supporting role, but also ensures the efficient and stable operation of the entire system by precisely controlling its various properties. This requires precise control of each link during material selection, process setting, and production processes to produce reverse osmosis membranes with excellent performance.

The surface roughness of polyester non-woven fabric has a key influence on the performance of reverse osmosis membrane. This involves two main aspects: one is the bonding force between the film layers, and the other is the formation of the film layers.

Bonding force between film layers

The surface roughness of the polyester non-woven fabric has a direct impact on the bonding force between it and the upper layer of the reverse osmosis membrane (usually the polysulfone layer). When the surface roughness of the non-woven fabric is higher, its surface will have more contact points and uneven places, which will help increase the interaction force with the polysulfone layer, thereby making the various layers of the membrane They can form a better combination, making them more stable and durable. On the contrary, if the surface is too smooth, the contact surface between it and the polysulfone layer will be reduced, which may cause the reverse osmosis membrane to delaminate when it is operated under high pressure.

film formation

In addition to affecting the bonding force between membrane layers, the surface roughness of the polyester non-woven fabric will also affect the formation process of the reverse osmosis membrane. In the process of preparing a reverse osmosis membrane, the membrane layer to be formed is usually coated on the surface of polyester non-woven fabric. At this time, if the surface roughness of the non-woven fabric is too large, it may affect the uniformity of coating, lead to uneven film thickness, and ultimately affect the separation performance of the reverse osmosis membrane. If the surface is too smooth, the polysulfone layer may not adhere well to the surface during the coating process, which may cause the membrane layer to fall off during the reverse osmosis process.

Therefore, the surface roughness of polyester non-woven fabrics needs to be properly controlled to ensure good performance of the reverse osmosis membrane. This also means that in the process of preparing reverse osmosis membranes, the selection and processing of non-woven fabrics, coating process, and subsequent drying and curing steps need to be carried out in strict accordance with the prescribed process conditions to ensure that the membrane layer The uniformity and bonding force between membrane layers are achieved to obtain a reverse osmosis membrane with superior performance.

If the surface of a nonwoven is too smooth, it can create a series of problems that can negatively impact the performance of the nonwoven in a variety of applications.

Reduce adhesion

If the surface smoothness of the non-woven fabric is too high, it may affect the adhesion between it and other materials. For example, when preparing a reverse osmosis membrane, if the surface is too smooth, the polysulfone layer or other membrane materials may not be able to fully adhere to the surface. attached to it. Once the adhesion is insufficient, it may cause peeling or delamination of the membrane layer or material during the subsequent membrane separation process or when subjected to environmental changes and physical pressure, which will have a huge impact on the performance of the entire product, including service life, Operational intensity and even filtration performance will be threatened to varying degrees.

Affects coating and painting processes

During the coating or painting process, a nonwoven surface that is too smooth may prevent the coating from evenly laying down or adhering, negatively impacting coating formation, thickness, and consistency. If the coating does not develop into a good consistency, the film may exhibit inconsistent performance when applied.

Affects lamination applications such as wallpaper

In addition, if non-woven fabrics are used as base materials for wallpaper or other products that need to be pasted, an overly smooth surface may lead to insufficient adhesion between the base material and the wall or other materials, thus affecting its final fit and effect. service life.

Influence the performance of non-woven fabrics

Finally, in the process of processing certain properties such as hydrophilicity, the surface of the non-woven fabric is too smooth, which may affect the addition and distribution of the hydrophilic agent. Hydrophilicity is an important attribute for many applications, such as wipes and medical supplies. If the surface is too smooth, the hydrophilic agent may not be evenly distributed on the non-woven surface, affecting the overall performance of the product.

Therefore, the surface smoothness of non-woven fabrics needs to be properly controlled to ensure their application effects and performance in different fields. In the actual manufacturing process, this may be achieved by adjusting production parameters or adopting specific processing methods, such as surface roughening. This is because the ideal non-woven surface should not be too smooth, but should have a certain roughness to enhance its adhesion and ensure its performance in niche application fields.