What are the types of membrane separation technologies in commonly used water treatment technologies

Common membrane separation methods mainly include microfiltration, ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, pervaporation and other methods.

1. Microfiltration: Compared with conventional filtration, microfiltration belongs to precision filtration, which is a separation process that intercepts grit, silt, clay and other particles in the solution and Giardia, Cryptosporidium, algae and some bacteria, etc., and a large number of solvents, small molecules and a small amount of macromolecular solutes can pass through the membrane. There are two types of microfiltration operations: dead-end filtration and cross-flow (also known as tangential flow) filtration.

2. Ultrafiltration: Ultrafiltration is a sieve pore separation process under the action of differential pressure, which is between nanofiltration and microfiltration, and the membrane pore size range is between 1nm. The earliest ultrafiltration membranes used were natural animal organ membranes.

3. Nanofiltration: Nanofiltration membrane separation is carried out at room temperature, no phase change, no chemical reaction, no destruction of biological activity, can effectively intercept divalent and ** ions and organic small molecules with a relative molecular weight higher than 200, and make most of the monovalent inorganic salts permeable, can separate similar amino acids and proteins, and realize the separation of high molecular weight and low molecular weight organic matter, and the cost is lower than the traditional process, so it is widely used in the preparation of ultrapure water, food, chemical industry, medicine, biochemistry, environmental protection, Various concentration and separation processes in metallurgy and other fields.

In membrane separation technology, related products include membrane modules, hollow fiber membranes, sodium filter membranes, etc., among which RO membranes.

The module is divided into freshwater membrane (purified water production) and saltwater membrane (seawater desalination).... Yijie water quality.

The types of membrane separation technologies include: microfiltration (MF), ultrafiltration (UF), nanofiltration (UF), reverse osmosis (RO), membrane bioreactor (MBR), membrane integration technology, etc.

Membrane separation technology is widely used in textile, electric power, machinery, fermentation, food, pharmaceutical and chemical industry, biology, environmental protection, pesticide chemical industry, metallurgy, energy, petroleum, water treatment, electronics, bionic and other fields, while improving separation efficiency, energy consumption is greatly reduced.

Membrane separation technologies mainly include the following: pervaporation, microfiltration, ultrafiltration, nanofiltration, and reverse osmosis.

1. Pervaporation - Pervaporation - Pervaporation is also known as pervaporation evaporation, which refers to a membrane separation method in which the components pass through the membrane and evaporate at different rates under the action of the vapor partial pressure difference of the components on both sides of the membrane, so as to achieve the purpose of separation. The organic pervaporation membrane uses the adsorption-dissolution mechanism of the membrane layer to the components, and the molecular sieve pervaporation membrane uses the adsorption-diffusion and molecular sieve mechanism of the membrane layer on the components. Applications include dehydration of organic solvents, removal of organic matter from aqueous solutions, and separation of organic matter from organic matter.

2. Microfiltration - often used in food and medicine disinfection, purification of liquids in semiconductor production industry, biotechnology, wastewater treatment, etc.

3. Ultrafiltration - commonly used in milk skimming, protein pre-concentration, juice clarification, fermentation broth treatment, discharge liquid treatment, etc.

4. Nanofiltration - can be used to remove oligosaccharides, dyes, multivalent ions, etc.

5. Reverse osmosis - it can be used to treat municipal wastewater, industrial wastewater, seawater and brackish water desalination, groundwater and surface water treatment.

Membrane separation technology: Mixtures of molecules of different particle sizes are selectively separated through semi-permeable membranes.

The application prospects of membrane separation technology in wastewater treatment are discussed as follows:

After more than 30 years of lagging development in the current membrane separation technology, great achievements have been made in pollution control, structural adjustment and technological progress, and microfiltration, ultrafiltration, electrodialysis, gas separation, inorganic membrane and other technologies in membrane separation technology have been widely used.

It has been effectively used in the fields of energy, electronics, petroleum and chemical filial piety. However, in the process of practical application, we have also noticed that there are still many problems that limit the application of these technologies.

The improvement of membrane products, membrane fouling, and membrane separation performance are the most typical problems. In the future, we should focus on strengthening the study of these issues.

However, we need to pay attention to the fact that since membrane technology itself is an emerging technology, in order to achieve long-term development of this technology, three problems must be solved in the future development: selectivity problem, output value problem, and flux stability problem.

The so-called selectivity problem refers to the fact that in the actual production process, the development of polymer membrane materials and inorganic membrane materials should be further strengthened, and the research on high-efficiency electrolyte membranes, biomimetic membranes and molecular recognition membranes should achieve the goals of specialization, intelligence and efficiency.

The stability of membrane flux and the value-to-value ratio are mainly focused on the anti-fouling and intensification of membrane processes during permeation. In the actual application process, no matter what kind of membrane is used, there will be problems such as the formation of adhesive layers on the surface of the film and the blockage of membrane pores.

It is precisely because of the existence of these problems that the stability of copper beams and the output value ratio will be affected. In the future research process, it is necessary to strengthen the research in this area, comprehensively consider all factors, select appropriate membrane materials, and reasonably design membrane modules, in addition to a thorough technological process.

Membrane separation technology is an advanced water pollution treatment technology, and the research and application of membrane separation technology should be vigorously strengthened in the context of accelerating urbanization.

At present, this technology is widely used in various fields of urban sewage, and in order to effectively improve the efficiency of sewage treatment, it is necessary to strengthen the research on selectivity, flux stability and yield ratio.

Commonly used several copy of the membrane separation method sewage treatment method:

1. Ultrafiltration membrane separation method. According to the shape and different properties of molecules, the effect of atmospheric pressure is used to effectively screen and separate them. Through years of research and use in China, this technology has a remarkable decontamination effect and can effectively treat Bing protoplasma in sewage.

Therefore, ultrafiltration membrane separation technology has been widely used in various sewage treatment in China.

2. Nanofiltration membrane separation method. In the mid-to-late 70s of the 20th century, the nanofiltration membrane separation technology was formed to ensure that the inorganic salts were not affected by the electric potential and chemical gradient, and the molecules with a diameter of about 1 nanometer were effectively screened and separated through the effect of (the actual pressure is less than or equal to the actual pressure, so as to achieve the effect of sewage treatment.

3. Liquid film separation method. In the 60s of the 20th century, it was proposed until the mid-to-late 80s that the liquid film separation technology was widely used, which is divided into emulsion film and support liquid film, of which the emulsion liquid film is widely used in sewage treatment technology. Clause.

4. Membrane bioreactor. It is a new type of decontamination technology formed by combining the membrane with the bioreactor after the raw water enters the bioreactor and fully reacts with the organisms, using a circulating pump to make the water flow through the membrane module, and the water is discharged and the biological phase flows back into the bioreactor.

1.Advanced treatment of microfiltration effluent (MF).

Membrane pore size", the working pressure is about 300kpa. It can be used to separate fine particulate matter (<15 m) and coarse dispersed phase oil beads in sewage or as a pretreatment for other treatment processes;

2.Ultrafiltration Membrane Separator (UF).

The membrane pore size is 150 700kpaThe ultrafilter can separate fine particulate matter (10 m) and emulsified oil in sewage. Useful substances (e.g. from electroplating paint waste, polyvinyl alcohol in the chemical fiber industry); When used in advanced sewage treatment, it can remove macromolecules and colloidal organic substances, viruses and bacteria; Or as a pretreatment for reverse osmosis equipment, remove suspended matter, BOD and COD components, reduce the load of reverse osmosis, and make its operation stable.

3.Nanofiltration Membrane Separation Equipment (NF).

Membrane pore size, operating pressure of 500 1000kpaThe nanofilter can intercept organic compounds with a relative molecular mass of 200-500, which is mainly used for the separation of multivalent ions and color particles in sewage, and can remove 2 3 salinity, 4 5 hardness and more than 90% of dissolved organic carbon and THM precursors in secondary effluent. Nanofiltration inlet water is required to be virtually turbidity-free, so it is only suitable for water quality that has undergone sand filtration, microfiltration, and even ultrafiltration as pretreatment.

4.Reverse osmosis membrane separation equipment (RO).

Membrane pore size <, operating pressure》Reverse osmosis can remove not only salts and other substances in the ionic state, but also organic matter, colloids, bacteria and viruses.

5.Electrodialysis (ED).

It is suitable for the treatment of high salt concentration water with a salt content of 500-4000mg l, which can remove ionized inorganic salts in the water.

Membrane separation technology refers to the mixture of molecules of different particle sizes at the molecular level when passing through the semi-permeable membrane, to achieve selective separation technology, semi-permeable membrane is also known as separation membrane or filter membrane, the membrane wall is covered with small pores, according to the pore size can be divided into: microfiltration membrane (MF), ultrafiltration membrane (UF), nanofiltration membrane (NF), reverse osmosis membrane (RO), etc., membrane separation adopts cross-flow filtration.

The specific fields involved in microfiltration mainly include: pharmaceutical industry, food industry (gelatin, wine, liquor, juice, milk, etc.), high-purity water, urban sewage, industrial wastewater, drinking water, biotechnology, biological fermentation, etc.

Ultrafiltration was used in the early days of industrial ultrafiltration for wastewater and wastewater treatment. Over the past 30 years, with the development of ultrafiltration technology, ultrafiltration technology has been involved in many fields such as food processing, beverage industry, pharmaceutical industry, biological preparations, traditional Chinese medicine preparations, clinical medicine, printing and dyeing wastewater, food industry wastewater treatment, resource development, environmental engineering and so on.

The main application fields of nanofiltration and nanofiltration include: food industry, plant deep processing, beverage industry, agricultural product deep processing, biomedicine, biological fermentation, fine chemicals, environmental protection industry, etc.

Due to the advanced, efficient and energy-saving characteristics of reverse osmosis separation technology, reverse osmosis has been widely used in various sectors of the national economy, mainly used in water treatment and concentration of heat-sensitive substances, the main application fields include the following: food industry, milk industry, beverage industry, plant (agricultural products) deep processing, biomedicine, biological fermentation, preparation of drinking water, pure water, ultrapure water, seawater, brackish water desalination, electricity, electronics, semiconductor industry water, pharmaceutical industry process water, preparation water, Water for injection, sterile pure water without pyrogen, process water for food and beverage industry, chemical industry and other industries, boiler water, washing water and cooling water.

In addition to the above four commonly used membrane separation processes, there are also dialysis, controlled release, membrane sensor, membrane gas separation, liquid membrane separation, etc.

The methods of membrane separation are:

1.Microfiltration: Refers to the retention of particles or solubles larger than that.

The pressure drives the process of the plate.

2.Ultrafiltration. Right: refers to the process by which particles or solubilities smaller than 2 nm are trapped in a pressure-driven membrane.

3.Nanofiltration: A pressure-driven membrane separation process (particles less than 2 nm) between reverse osmosis and ultrafiltration

4.Reverse osmosis: Using a highly permeable film as the separation medium, the solvent in the solution can penetrate the film when the osmotic pressure of the solution is exceeded, and the solute and insoluble matter are intercepted in front of the membrane.

Membrane separation technology is a new technology for separation, purification, and concentration with high efficiency and energy saving without phase change at room temperature. Its basic principle is that it can use natural or synthetic films with selective permeability to separate, classify, purify or enrich two-component or multi-component systems with external energy or chemical potential difference as the driving force, and can be used in both liquid and gas phases.

For liquid-phase separation, it can be used in aqueous solution, non-aqueous solution, aqueous sol system, and aqueous solution system containing other particles. Most of the separation membranes are solid (most of the current membrane materials are organic polymers), but they can also be liquids. What they all have in common is the ability to selectively transmit to the systems they separate.

Below, Dramayler introduces you to the characteristics of common membrane separation technologies.

According to the type of membrane, it can be divided into microfiltration, ultrafiltration, reverse osmosis, nanofiltration, dialysis, electrodialysis, osmotic gasification and gas separation.

Introduction to the characteristics of common membrane separation technologies:

1) The membrane separation process does not undergo phase change, and the energy consumption is lower than that of separation methods with phase change and other separation methods.

2) The membrane separation process is carried out at room temperature, so it is especially suitable for the separation, classification, concentration and enrichment of heat-sensitive substances, such as juices, enzymes, drugs, etc.

3) Membrane separation technology is not only suitable for the wide range of separation of organic and inorganic substances, from viruses, bacteria to particles, but also for the separation of many special solution systems, such as the separation of macromolecules and inorganic salts in the solution, the separation of some azeotropes or near-boiling point substances, etc.

4) Because only pressure is used as the driving force of membrane separation, the separation device is simple, easy to operate, easy to control and maintain.

Enzyme preparations and protein products.

Amino acids, peptides, antibiotics.

Plant raw materials (flavonoids, pigments, etc.).

Bio-fermentation preparations.

Large infusion to remove the heat source.

Bio-algae products.

Heparin sodium, chondroitin sulfate, biopolysaccharides.

Oligosaccharides, oligosaccharides, monosaccharides.

Organic acids such as citric acid, malic acid, etc.

Fruit and vegetable juices. Brewed products (alcohol, vinegar, etc.).

Dairy product. Medical sterile nonpyrogen water equipment.

Industrial separation, concentration, purification.

Industrial wastewater treatment, electrophoretic paint, electroplating oily wastewater treatment.