Membrane separation technology is highly valued by the technologically advanced countries of the world , the past 30 years , the United States , Canada, Japan and Europe technologically advanced countries , has been positioned as a high-tech membrane technology , invest a lot of money and manpower , and promote the rapid development of membrane technology , the use of growing range . Development and application of membrane separation technology for many industries , such as water production , desalination, brackish water desalination , electronics, pharmaceutical and biological engineering , environmental protection, food, chemical, textile and other industries , high-quality solution to the separation , concentrated and purified problems for the recycling economy, clean production technologies provide the basis .
1 Introduction Membrane Separation Technology
Definition film 1.1
A film is separated from the molecular level the role of the filter medium , when the solution in contact with the membrane , or a gas mixture , under pressure , or electric field, or the difference in temperature under the action of certain substances through the membrane can be , and the other of these substances to selectively intercept , so that different components of the solution or mixture of different gas components are separated , this separation is the separation at the molecular level .
Definition 1.2 membrane separation technology
The film made suitable for the above configuration, and driven equipment for industrial use ( pressure pump, or an electric field , or a heater , or vacuum pumps ) , valves, instrumentation and associated piping into the device. Under certain operating conditions , since the separation can be an aqueous solution or a gas mixture . Is called by the component through the membrane fraction . This separation technique is called a membrane separation technology.
. Kind of film 1.3
Membranes include : reverse osmosis membranes (.. 0 0001 ~ 0 005μm), nanofiltration (0 001 ~ 0 005μm..) Ultrafiltration membrane microfiltration (0 1 ~ 1μm (0 001 ~ 0 1μm..). ) , electrodialysis membranes , pervaporation membranes , liquid membranes , gas separation membrane , an electrode film. They correspond to different separation mechanisms , different devices have different application objects. Film itself can be made from a polymer or a liquid , or an inorganic material , its structure may be homogeneous or heterogeneous , porous or non-porous , solid or liquid , charged or neutral . The film thickness can be as thin as 100μm, to a thickness of a few millimeters . Different films having different microstructures and function, prepared by different methods. Film method has been the core research areas of the film , but also the strict confidentiality of each company 's core technology.
2 reverse osmosis ( NF ) technology
2.1 Introduction to Reverse Osmosis
Reverse osmosis , English as Reverse Osmosis, is spending hundreds of millions of dollars , and after years of well-developed high-tech water treatment technology . Such membrane separation techniques rely on the membrane under pressure so that the solution of solvent and solute separation process . Osmosis is a physical phenomenon . Reverse osmosis is in salty water ( such as raw water ) than the natural osmotic pressure exerted greater pressure , the water penetration by a high concentration to low concentration of one party , the water molecules in the raw water pressure to the other side of the membrane becomes into pure water, and minor impurities , colloids, organics , heavy metals , bacteria, viruses and other harmful substances in the raw water are all trapped down and discharged through the sewage outlet . Since the aperture is only 0.0001 micron reverse osmosis membrane , a bacteria 4,000 times to narrow , viruses have reduced more than 200 times to pass , so the effective removal of up to 96%.
Water quality of reverse osmosis 2.2
Reverse osmosis water system uses a different process depending on the quality of water sources. Usually after a reverse osmosis water treatment system , water conductivity <10μS/cm, after the reverse osmosis system product water conductivity <5μS/cm even lower after the reverse osmosis system is supplemented by ion exchange equipment or EDI devices may be prepared in ultra-pure water , the resistance rate of 18
2.3 Reverse Osmosis Applications
Electronic industrial water ........ integrated circuits, silicon wafers , display tubes and other electronic components rinse water
Pharmaceutical industry water ........ infusion, injection , tablets , biochemical products , equipment cleaning , etc.
Chemical industry chemical recycling process water .... water , chemical products manufacturing
Power industry boiler feed water .. thermal power boiler , industrial power systems in low-pressure boiler
Food industrial water ........ clean drinking water, soft drinks, beer , wine, health products
Seawater , brackish water desalination .... islands, ships , offshore drilling platforms , brackish water areas
Drinking water .......... real estate property , communities, enterprises and other
Other process water ........ automotive, appliance paint , coated glass , cosmetics , fine chemicals , etc.
3 ultrafiltration
3.1 Introduction ultrafiltration
Ultrafiltration is a fluid tangential flow and pressure driven filtration process to separate particles according to molecular size . Ultrafiltration membrane pore size of about (MWCO of about 1,000 to 500,000 ) in the range of 0.002 to 0.1 microns . Dissolved substances is smaller than the membrane pore size and the material will be able to permeate through a membrane filter , can be gradually concentrated in the discharge of liquid through the membrane material . Thus product water ( permeate ) containing the water , ions, and small molecular weight substance , and colloidal substances , particles, bacteria , viruses and protozoa will remove the film . Ultrafiltration membrane can be used repeatedly and can ordinary cleaning agent .
3.2 Principles ultrafiltration membrane filtration
Ultrafiltration is a process of screening related to the pore size of the membrane , a pressure differential across the membrane as the driving force for membrane filter media , under a certain pressure , when the liquid flow through the membrane surface , ultrafiltration many small dense microporous membrane allows only the surface of the water and small molecules passed into the permeate , while the volume of liquid is greater than the pore size of the membrane surface material were trapped in the inlet side of the membrane to become concentrated liquid , thereby achieving purification of the liquid , the separation and concentration purposes. See the figure below .
Generally refers to liquid to be purified by ultrafiltration , the concentrated solution or isolated by means dope solution was filtered through a macromolecular membrane that part of the liquid solute concentrated liquid is separated out through the liquid due to the liquid the remaining solution of high concentration . In the water purification project , the dope is the raw water intake , through liquid water is purified water by different ways , hollow fiber membrane is divided into wastewater internal pressure and external pressure are two emissions.
3.3 Classification of ultrafiltration
A hollow fiber ultrafiltration membrane is dominated by the root of hundreds to thousands of small hollow membrane filaments and two -part housing , the inner diameter of the hollow fiber membrane generally in between 0.6-6mm called capillary ultrafiltration membrane membrane , ultrafiltration membrane by capillary inner diameter of the larger , and therefore can not easily be blocked large particulate matter, more applicable to large concentrations of liquid filtration applications. Different ways by water , hollow fiber membrane is divided into internal pressure and external pressure type two , during which introduces compression 3.4 . Internal pressure ultrafiltration hollow
I.e., first into the liquid inside the hollow fibers , driven by the pressure difference , the radial penetration through the hollow fiber from the inside outwardly through the fluid to become concentrated liquid is left in the interior of the hollow filament , the outflow from the other side , the flow shown in FIG see below : wherein the epoxy resin is the role of the end sealing of the hollow fiber membranes at the ends of the membrane to seal the gap between the filaments , so that the liquid separated by the liquid to prevent the liquid does not pass through the membrane filter wire through the liquid directly into the the .
Water from the filter into the end face of the ultrafiltration membrane , under the action of normal water pressure , water seeping from the ultrafiltration membrane wall , and sediment, rust, colloid , bacteria , suspended solids , organic molecules and other harmful substances being trapped in the ultrafiltration membrane tube and is discharged from the outlet when the user direct access to the water tap or using straight flush and filter backwash . Internal pressure characteristics of hollow fiber ultrafiltration
1 ) internal pressure capillary membrane structure, vertical cross- turbulent filter , rinse thoroughly convenience , filter clogging .
2 ) installation, simple operation , the use of clean water rinse thoroughly mutual impulse method , producing water attenuation rate, water flux recovery quickly.
3 ) the utilization of the water is high, the recovery of 95% can be achieved .
4 ) at room temperature under low pressure automatic separation, low energy consumption, low operating costs and easy maintenance. |
