What materials are needed for reverse osmosis membranes?

Reverse osmosis membranes are classified by material.

Cellulose acetate membrane.

Cellulose acetate membranes have a high desalination rate, and the water yield can meet the general filtration needs.

However, the hydrolysis of cellulose acetate reverse osmosis membrane will inevitably occur, and the pH value range allowed for continuous operation of cellulose acetate reverse osmosis membrane is 4-6, and the pH value range is 3-7 during cleaning, and the hydrolysis speed is the slowest when the pH value is the same, which leads to a large amount of acid added during pretreatment, and the range of chemicals that can be used during cleaning is narrow, and it is not easy to obtain satisfactory cleaning results.

Aromatic polyhydrazide film.

The aromatic polyhydrazide membrane has the highest desalination rate among the three membranes, with a wide range of pH value, 2-11, and acid and alkali resistance.

It is used in the sewage treatment of the following large-scale chemical plants and coating plants, and is more suitable for brackish water desalination, high-purity water preparation, metal wastewater treatment, heavy metal salts** and separation of alkaloids, hormones and bacterial diseases.

Aromatic polyamide membrane.

Polyamide, commonly known as nylon, is a general term for heterochain polymers containing repeating structural unit amide groups in the polymer macromolecular chain, which is mainly obtained by polycondensation or self-polymerization of dibasic acids and dibasic amines or amino acid lactams, and is the earliest developed and most widely used thermoplastic engineering plastics.

Introduced in the polyamide backbone as semi-aromatic or fully aromatic polyamides, heat resistance and stiffness can be further improved. Similar to aliphatic polyamides, aromatic polyamides can be formed by polycondensation of diacids and diamines. Semi-aromatic polyamides can be formed by polycondensation of aromatic diacids and aliphatic diacids, and the simplest fully aromatic polyamide is poly, which can be synthesized by self-condensation of aminobenzoic acid.

However, the benzene ring and amide group in the main bond are dense, and the structure is symmetrical, the melting point is high, it is not easy to process, the cost is high, and it is not easy to industrialize. The most successful fully aromatic polyamide is polyterephthalyl p-phenylenediamine, which is a lysotropic liquid crystal polymer that can be processed into fibers.

Aromatic polyamide membranes are widely used, and many composite membranes have been developed according to aromatic polyamide materials, which have high desalination rate, large flux, pollution resistance, and oxidation resistance.

Generally, a reverse osmosis membrane element is composed of the following materials.

1. a center rod.

2. Diaphragm (the most important part).

3. Water supply net.

4. Sealant.

5. FRP winding shell.

The reverse osmosis membrane is generally four layers, the non-woven fabric is the base layer, the polysulfone support layer is on it, which is actually a layer of ultrafiltration membrane, and then the desalination layer is made of aromatic polyamide. The top layer is the functional layer, such as anti-pollution, anti-oxidant materials, etc.

Cellulose acetate reverse osmosis membranes. Generally, cellulose is esterified to form triacetate fiber, and then hydrolyzed into a mixture by secondary hydrolysis.

One, two, and three acetate. The most important factor affecting the desalination rate and water yield of the membrane is that the high acetyl content is the high desalination rate, but the water yield is low. Composite reverse osmosis membranes.

The main supporting structure of the composite film is a polyester non-woven fabric after calendering machine, which has no loose fibers on the surface and is hard and smooth.

Summary. The differences between permeable membrane and reverse osmosis membrane are as follows:

Reverse osmosis technology is a separation technology developed in the 60s of the last century, which mainly relies on the pressure of the reverse osmosis membrane to separate solutes and solvents. Later, this application technology was widely used and is more common in all major fields such as medicine and food and beverage. However, when it comes to reverse osmosis membrane and permeable membrane, many people do not understand the difference between the permeable membrane and the permeable membrane.

1. The purpose of water supply is different.

Nowadays, reverse osmosis technology is becoming more and more advanced, and after continuous extension and development, in addition to being widely used in industry, it is also the application of sorted water sources in household drinking water to meet the needs of kitchen water. The permeable membrane is mostly used for washing.

2. The production standards are also different.

Compared with the permeable membrane, the production standard of reverse osmosis membrane is higher, and the general permeable membrane production qualification standard is 100 colonies per milliliter, while the reverse osmosis membrane has 20 colonies per milliliter, with a 4-fold gap.

Difference Between Permeable Membrane and Reverse Osmosis Membrane.

The difference between permeable membrane and reverse osmosis membrane is as follows: reverse osmosis technology is a separation technology developed in the 60s of the last century, mainly relying on the pressure of reverse osmosis membrane to separate solutes and solvents. Later, this application technology was widely used and is more common in all major fields such as medicine and food and beverage.

However, when it comes to reverse osmosis membrane and permeable membrane, many people do not understand the difference between the permeable membrane and the permeable membrane. 1. The use of water supply is not the same, and now the reverse osmosis technology is becoming more and more advanced, after continuous extension and development, in addition to being widely used in the industry, it is also the water source that has been sorted out is applied to the household drinking water to meet the needs of kitchen water. The permeable membrane is mostly used for washing.

2. The production standards are also different compared with the permeable membrane, the production standard of the reverse osmosis membrane is higher, the general permeable membrane production qualification standard is 100 colonies per milliliter, and the colonies per milliliter of reverse osmosis membrane are 20, with a 4-fold gap.

3. The pore size of the reverse osmosis membrane is only 1 100 of the pore size of the permeable membrane, and it can also remove some very small pollutants of organic molecules in the water, such as organic pesticide pollution and organic chemical pollution, while ordinary permeable membranes cannot achieve such an effect.

Reverse osmosis membrane is an artificial semipermeable membrane made of simulated biological semi-permeable membrane with certain characteristics, which is the core component of reverse osmosis technology. The principle of reverse osmosis technology is that under the action of higher than the osmotic pressure of the solution, other substances cannot penetrate the semi-permeable membrane.

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Advantages: high filtration accuracy, reverse osmosis membrane filtration accuracy up to microns, filtered water can be directly drinkable.

It is easy to operate, compact in structure and low in maintenance cost.

Disadvantages: Wastewater will be generated.

It needs to be replaced regularly.

What is a reverse osmosis membrane

Reverse osmosis membrane is an artificial semi-permeable membrane made of simulated biological semi-permeable membrane with certain characteristics, which is the core element to achieve reverse osmosis, generally made of polymer materials, and is widely used in large, medium and small water treatment systems. The diameter of the micropores on the surface of the reverse osmosis membrane is generally between, and the size of the permeability is related to the chemical structure of the membrane itself. Some polymer materials have good repulsion to salt, but the permeability of water is not good.

Some polymer materials have more hydrophilic groups in their chemical structures, so the permeability of water is relatively fast. In the development of modern industry, reverse osmosis membrane is recognized by the industry as the most economical and effective core component of membrane water treatment due to its excellent desalination performance, higher water yield, lower operating pressure and longer service life in the treatment of brackish water and seawater.

Reverse osmosis membrane features

1.Due to the large KW of the composite membrane, its working pressure is low, and the electricity consumption of the reverse osmosis feed pump is reduced by more than half compared with the cellulose acetate membrane.

2.The reverse osmosis membrane uses a new self-locking link technology that eliminates the risk of degradation of permeate water quality due to O-ring leakage.

3.The reverse osmosis membrane adopts fully automatic membrane rolling technology. Ensure that the filtration area of all membrane modules and the thickness of the inlet flow channel are the same, and the elements with accurate membrane area ensure the effective filtration area.

4.In the manufacturing process of reverse osmosis membranes, the membrane elements are not treated with any oxidizing chlorine. It reduces the occurrence of membrane performance degradation caused by oxidation on the membrane surface, and ensures the filtration effect.

4.The wider the inlet flow channel of the reverse osmosis membrane, the lower the operating cost, and the more relaxed the requirements of the system for the influent water quality and the abnormal working conditions of the pretreatment equipment.

Due to the different water sources used in the production of reverse osmosis systems, different raw water treatment methods, and different production methods, the reverse osmosis membrane is polluted to different degrees, and a large number of suspended solids, colloidal sticks, organic matter, inorganic salts, residual chlorine, microorganisms, etc. are blocked, which greatly affects the water output and water quality, and the manufacturer must be cleaned regularly.

GE reverse osmosis membrane cleaning requirements.

The first step is to confirm the material of the GE reverse osmosis membrane element to consult and select a disinfectant to avoid damage to the RO membrane.

Users can determine the working volume of cleaning solution and disinfectant according to the number of membranes and the capacity of the system, and determine the amount of cleaning solution and disinfectant commodity.

According to the investigation and diagnosis of the system, the type of membrane fouling is determined, and the corresponding agent is selected for cleaning or sterilization.

Cleaning fluid. The disinfectant must pass through a security filter before entering the membrane tube.

The best cleaning temperature is 25-35, if used under low temperature conditions, the cleaning time should be appropriately extended.

If there are multiple types of contamination in the system, it can be cleaned and sterilized in the order of organic, inorganic and microbial matter, and after each process is completed, it needs to be cleaned with permeable water before proceeding to the next process. Cleaning solution and disinfection and sterilization solution are used separately and should not be mixed.

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Precautions: 1. The reverse osmosis membrane of Drammel must be stored at room temperature and cannot be stored in direct sunlight.

2. If the polyethylene bag is damaged, a new preservative solution (sodium bisulfite) must be added and sealed airtightly to prevent drying and microbial growth.

3. In the first hour of operation, the flushed out anticorrosive liquid wastewater should be discharged.

4. All membrane elements have been strictly tested before leaving the factory, and the sodium bisulfite (10% propylene glycol antifreeze should be added in winter) solution is used for storage, and the vacuum packaging is used, and the outer packaging is a cardboard box.

(1) Temperature In the process of reverse osmosis, the temperature of the feed liquid will increase with the progress of the operation. In a certain range, the increase in temperature causes the decrease of the viscosity of the feed liquid, which is conducive to the increase of reverse osmosis water production. Increase 1, the water permeability of the membrane increases approximately.

The water permeability of the membrane marked by the commercial membrane is generally the data value of the water temperature in 24 25, and the actual water permeability at the working temperature should be calculated through the correction coefficient. It should be noted that the operating temperature should not exceed the heat-resistant temperature of the membrane, otherwise the service life of the membrane will be affected.

2) PH value The reverse osmosis membrane of different materials has different pH value application range, such as the pH value of acetate fiber membrane is 3 8, and the pH value range of aromatic polyamide membrane is 4 10; The pH value of DuPont type nylon hollow fiber membrane is. When the pH value of the feed exceeds the limit of the use of the membrane, it will have harmful effects such as hydrolysis and aging on the membrane, causing a decrease in water production, and causing the continuous reduction of the performance of the membrane until the membrane is damaged. In general, the pH value of acetate membrane should be controlled between 4 7, while the pH value of aromatic polyamide membrane should be controlled at 3 11, and the pH value of composite film is about 2 11.

3) Cleaning effect of membrane moduleMembrane pollution is a phenomenon that inevitably occurs in reverse osmosis operation and affects the normal operation of the system. Even if the feed liquid is pretreated before operation, the contamination of the membrane cannot be completely eliminated, and after the membrane contamination occurs, it will cause a decrease in water yield and desalination rate, and at worst it will have a great impact on the life of the membrane, and even cause the operation of the treatment system to be paralyzed. Therefore, the membrane module needs to be cleaned regularly according to the actual situation.

4) Operating pressure In the process of reverse osmosis, maintaining and increasing the operating pressure is conducive to improving the permeability, and because the membrane is compacted, the salt permeability will be reduced. However, when the operating pressure exceeds a certain limit, due to the serious compaction and deformation of the membrane, it will lead to the decline of the water permeability of the membrane and the aging of the membrane. Therefore, the appropriate operating pressure should be selected according to the actual treatment liquid and the pressure resistance of the selected reverse osmosis membrane.

5) The pH value of the pretreatment treatment liquid, the suspended solids contained in it and the microbial mass will affect the effect of reverse osmosis, so it is necessary to take effective pretreatment measures for the raw water, such as pH value adjustment, filtration, disinfection, etc., to give full play to the efficiency of reverse osmosis.

Notes:

1. To maintain the wet state, the membrane element must be kept in the wet state all the time. Even if it is necessary to open it temporarily in order to confirm the quantity of the same package, it must be done without piercing the plastic bag, and this state should be stored until the time of use.

2. Storage temperature: The membrane element is best stored at a low temperature of 5 10. Physical damage can occur if it freezes, so take insulation measures to prevent it from freezing. When storing in an atmosphere of more than 10 years, avoid direct sunlight and choose a well-ventilated place.

At this time, do not store at a temperature of more than 35.