Membrane technology, also known as membrane separation technology, is based on polymer separation membrane as a new type of fluid separation unit operation technology, which is characterized by the separation does not exist to the change, only through the pressure effect to achieve the separation effect, is the current energy-saving and efficient separation technology. Membrane technology can use semi-permeable membranes to separate solvents or solutes out of wastewater, common membrane technology including microfiltration, ultrafiltration, nanofiltration and reverse osmosis.
Microfiltration is a precision filtration method, the use of fluid pressure difference, the large molecules of solutes or particles will be retained, while small molecules of solutes or particles can be passed through the membrane, generally can be retained in the solution of clay, silt and gravel and other particles, but also can be retained algae, Cryptosporidium, Giardia and so on. Microfiltration mainly has a wrong flow filtration and dead-end filtration two ways, of which, wrong flow filtration for large-scale applications, for the concentration of suspended particles, the size of the change is not sensitive, but the membrane should be cleaned frequently, dead-end filtration is suitable for a small range of treatment, the membrane is usually made into a disposable cartridge.
Ultrafiltration is the use of differential pressure to promote the realization of the sieve pore separation, membrane pore size range in the range of 1nm ~ 0.055m, the initial use of ultrafiltration membranes for animal organs membrane, after the development of industrial applications, can now use asymmetric membrane, the epidermal layer is thinner, so the operating pressure is smaller, generally in the range of 0.1 ~ 0.5MPa, the membrane of the water permeability of about 0.5 ~ 5.0m (m.m). Practical wastewater treatment, ultrafiltration membrane performance to achieve and not only for the sieving theory, the surface chemical properties of its materials also play an important role, so it can be considered that the ultrafiltration membrane separation characteristics of the chemical properties and the membrane pore size is jointly determined.
Nanofiltration membrane separation does not cause damage to biological activity, there is no chemical reaction and phase change, can effectively retain the relative molecular mass of more than 200 organic small molecules and high-valent ions, and separation of proteins and similar amino acids, to achieve separation of low molecular weight and high molecular weight, the cost is relatively low, and can be widely used in metallurgy, biochemistry, environmental protection, pharmaceuticals, chemical industry and other fields.
4. Reverse osmosis membrane
Reverse osmosis membrane separation process can effectively remove organic small molecule impurities and inorganic salts, convenient operation, simple equipment, easier to realize automation, due to its separation process is out of the high-pressure state, so it should be configured with high-pressure pipeline and high-pressure pump, at the same time, reverse osmosis separation membrane device has a high water intake indicators, should be pre-treatment of raw water, followed by separation, in order to avoid membrane contamination, membrane cleaning can be carried out on a regular basis.
In the electric power, textile, chemical industry, electronics, metallurgy, petroleum, food, drinking water purification, industrial water treatment, biopharmaceuticals, fermentation and other fields, membrane technology is widely used as a new and efficient separation technology. Including textile, dyeing and finishing, printing and dyeing wastewater treatment and reuse, electroplating industrial wastewater zero discharge and resource recovery, mining and metallurgical wastewater treatment and recycling, starch wastewater treatment, biological fermentation filtration and sterilization and downstream separation and purification refining, resin resolution solution concentration and resolution agent recovery, pesticide production of aqueous and powder applications, Chinese medicine extract filtration and concentration of impurity removal and traditional Chinese medicine, Chinese medicine extract production and application of synthetic drugs, raw materials and drugs, intermediates, etc., desalination and concentration, crystallization mother liquor recovery, whey wastewater treatment, dairy production and processing applications, fruit juice clarification and decolorization, food additives purification and concentration, tea beverage clarification and concentration, beer, wine, yellow wine refining and processing, natural pigment extracts of impurities and concentration, amino acid filtration and clarification of fermentation broth and refining, and so on.
