The pore size of the reverse osmosis membrane is mostly 1 nanometer (1nm=10^-9m), and its separation object is the dissolved ions and molecular weight of several hundred or more organic matter.
Membranes that can only transmit solvents but not solutes are generally called ideal semi-permeable membranes.
When the solvent and solution (or two different concentrations of solution) are placed on both sides of the membrane, the pure solvent will naturally pass through the semi-permeable membrane and spontaneously flow to the solution (or from the low solution to the high concentration of solution) side, this phenomenon is called osmosis (Osmosis).
When the process of osmosis proceeds to the point where a pressure is generated at the level of the solution to counteract the tendency of the solvent to flow in the direction of the solution, equilibrium is reached, and this pressure is called the osmotic pressure of the solution.
The magnitude of the osmotic pressure depends on the type, concentration, and temperature of the solution and is independent of the membrane itself.
In this case, if the liquid surface of the solution and then apply a greater than the osmotic pressure of the applied pressure, the solvent will be with the original direction of osmosis is reversed, began from the solution to the solvent side of the flow, which is known as the reverse osmosis (Reverse Osmosis), based on the principle of concentration or purification of the separation of the solution is generally referred to as reverse osmosis process.
Reverse Osmosis is a reverse migration movement of osmosis, which is mainly driven by pressure, with the help of semi-permeable membrane retention, forcing the solvent and solute in solution to separate.
The higher the concentration of the solution, the greater the osmotic pressure value.
The pressure to be applied in the reverse osmosis process, in the system and the membrane strength within the scope of the allowable, must be much larger than the osmotic pressure of the solution value, generally for the osmotic pressure value of several times to nearly dozens of times.
When the salt of the aqueous solution and the porous semi-permeable membrane surface contact, then the solution interface in the membrane to choose to adsorb a layer of water molecules, under the action of reverse osmosis pressure, through the membrane of the capillary effect of the outflow of pure water. And continuously outflow form interface pure water layer.
As for the removal of organic matter, is a sieving mechanism. Therefore, it is related to the molecular weight size and shape of the organic matter.
Membranes with larger pore sizes are generally used in the ultrafiltration range and are called ultrafiltration membranes. The pore of ultrafiltration membrane is 2nm-10nm, while the pore size of reverse osmosis membrane is 0.3nm-2nm.
So, reverse osmosis membrane filtration can better remove all kinds of bacteria, such as the smallest bacterium "Pseudomonas aeruginosa" (3000×10m): it can also filter out all kinds of viruses, such as influenza virus (800×10m). Can also filter out various viruses, such as influenza virus (800 × 10m), can also filter out pyrogens (10-500 × 10m). In 1950, the American scientist DR.S.Sourirajan found that seagulls sip up a large mouthful of seawater from the surface of the sea when flying in the sea, and spit out a small mouthful of seawater after a few seconds, and had a doubt, because the animals on the land by the lungs to breathe is absolutely not able to drink seawater with high salt content. After dissection found that the seagulls have a layer of film in the body, the film is very precise, seawater by the seagulls into the body after pressurization, and then by the pressure of water molecules through the penetration of the film into fresh water, while containing impurities and highly concentrated salt seawater will be spit out of the mouth, which is the basic theoretical structure of the reverse osmosis method;
In 1953, by the United States of America University of Florida (University of Florida) applied to the desalination of sea water.
In 1953 by the United States of America University of Florida (University of Florida) applied to the desalination of sea water to remove salt equipment,
In 1960 by the United States of America federal government special projects to support the United States of America U.C.L.A. University of Medicine Professor Dr. S. Sidney Loeb with Dr. S. Sourirajan to start the study of reverse osmosis membranes, according to the priority of the capillary adsorption model, invented the sea water used for desalination of the Cellulose acetate membrane, creating a new era of research and development of membrane science and technology; a year of about $ 400 million investment in research, to be used in the use of astronauts, so that the spacecraft do not have to carry a large number of drinking water into space, until 1960 into the research work of scholars, experts more and more, so that the quality and quantity of the more refined, thus solving the problem of human Chin Chin with water.
Since then, reverse osmosis membrane development has had a major breakthrough. Membrane materials from the initial single cellulose acetate asymmetric membrane development to the surface polymerization technology made of cross-linked aromatic polyamide composite membrane. Operating pressure is also extended to high-pressure (desalination) membrane, medium-pressure (cellulose acetate) membrane, low-pressure (composite) membrane and ultra-low-pressure (composite) membrane. 80's, and the development of a variety of materials of nanofiltration membrane.
Who first coined the term reverse osmosis (RO)? There are two accounts, one by Gerald Hassler's research group at California State University, Los Angeles (UCLA) and first appeared in the UCLA Engineering Report of August 1956, and the other by Charles Reid's research group at the University of Florida and appeared in the Brackish Water Research Institute's April 1957 Research and Development Progress report. Because the research conducted by these two groups was completely independent, it is impossible to define who first coined the term reverse osmosis. However, the precise definition of "reverse osmosis" in terms of the reversibility of the process can be attributed to the fact that both Hassler and Reid were renowned physical chemists specializing in chemical engineering thermodynamics. Pharmaceutical, pharmaceutical industry sterile, no heat source purified water production;
Electronics, electric power industry with ultrapure water;
Biomedical water;
Chemical, cosmetic ingredients water;
Brackish water, seawater desalination;
Electroplating and coating industry used in the solution rationing, parts rinsing;
Precision machinery, special materials, optical materials, quartz products industry, and so on, and so on. Precision machinery, special materials, optoelectronic materials, quartz products industry with the cleaning, rationing, cooling water;
Drinking pure water, food and beverage water.
Humidifier, chemical experiment water. The upper layer of reverse osmosis and nanofiltration membranes is a thin, dense membrane that covers a thicker porous mesh on the lower layer.
There are two main basic types of membranes: cellulose acetate (CA) and composite (TFC).
Composite membranes outperform cellulose acetate in a number of ways, with cellulose acetate being used only in specific environments. Most reverse osmosis systems in operation today use composite membranes. At present, the composite membrane to the United States of America's Dow membrane (FILMTEC) for the best, is made in the USA, not technic in the USA
Filtration accuracy of 0.0001um ultra-tiny pore size
It is recommended to use the first rinse, there is something similar to the oil inside
Dow Chemical Co. is the world's only one at the same time with the two major types of separation technologies, namely, membrane and ion exchange resin two categories of separation technology and products, membrane products registered trademark for FILMTEC.
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