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Phase Inversion (chemistry)
Phase inversion or phase separation is a chemical phenomenon exploited in the fabrication of artificial membranes. It is performed by removing the solvent from a liquid-polymer solution, leaving a porous, solid membrane. Process Phase inversion is a common method to form filtration membranes, which are typically formed using artificial polymers. The method of phase inversion is highly dependent on the type of polymer used and the solvent used to dissolve the polymer. Phase inversion can be carried out through one of four typical methods: *Reducing the temperature of the solution *Immersing the polymer solution into anti-solvent *Exposing the polymer solution to a vapor of anti-solvent *Evaporating the solvent in atmospheric air or at high temperature The rate at which phase inversion occurs and the characteristics of the resulting membrane are dependent on several factors, including: *Solubility of solvent in the anti-solvent *Insolubility of the polymer in the anti-solvent *Te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthetic Membrane
An artificial membrane, or synthetic membrane, is a synthetically created membrane which is usually intended for separation purposes in laboratory or in industry. Synthetic membranes have been successfully used for small and large-scale industrial processes since the middle of twentieth century.Pinnau, I., Freeman, B.D., ''Membrane Formation and Modification'', ACS, 1999. A wide variety of synthetic membranes is known.Osada, Y., Nakagawa, T., ''Membrane Science and Technology'', New York: Marcel Dekker, Inc,1992. They can be produced from organic materials such as polymers and liquids, as well as inorganic materials. The most of commercially utilized synthetic membranes in separation industry are made of polymeric structures. They can be classified based on their surface chemistry, bulk structure, morphology, and production method. The chemical and physical properties of synthetic membranes and separated particles as well as a choice of driving force define a particular membrane se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cream
Cream is a dairy product composed of the higher-fat layer skimmed from the top of milk before homogenization. In un-homogenized milk, the fat, which is less dense, eventually rises to the top. In the industrial production of cream, this process is accelerated by using centrifuges called " separators". In many countries, it is sold in several grades depending on the total butterfat content. It can be dried to a powder for shipment to distant markets, and contains high levels of saturated fat. Cream skimmed from milk may be called "sweet cream" to distinguish it from cream skimmed from whey, a by-product of cheese-making. Whey cream has a lower fat content and tastes more salty, tangy and "cheesy". In many countries partially fermented cream is also sold: sour cream, crème fraîche, and so on. Both forms have many culinary uses in both sweet and savoury dishes. Cream produced by cattle (particularly Jersey cattle) grazing on natural pasture often contains some carotenoid pig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanofiltration
Nanofiltration is a membrane filtration process used most often to soften and disinfect water. Overview Nanofiltration is a Membrane technology, membrane filtration-based method that uses nanometer sized pores through which particles smaller than 10 nanometers pass through the membrane. Nanofiltration membranes have pore sizes from 1-10 nanometers, smaller than that used in microfiltration and ultrafiltration, but a little bit bigger than that in reverse osmosis. Membranes used are predominantly created from polymer thin films. Materials that are commonly used include polyethylene terephthalate or metals such as aluminum. Pore dimensions are controlled by pH, temperature and time during development with pore densities ranging from 1 to 106 pores per cm2. Membranes made from polyethylene terephthalate and other similar materials, are referred to as "track-etch" membranes, named after the way the pores on the membranes are made. "Tracking" involves bombarding the polymer thin fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultrafiltration
Ultrafiltration (UF) is a variety of membrane filtration in which forces such as pressure or concentration gradients lead to a separation through a semipermeable membrane. Suspended solids and solutes of high molecular weight are retained in the so-called retentate, while water and low molecular weight solutes pass through the membrane in the permeate (filtrate). This separation process is used in industry and research for purifying and concentrating macromolecular (103–106 Da) solutions, especially protein solutions. Ultrafiltration is not fundamentally different from microfiltration. Both of these separate based on size exclusion or particle capture. It is fundamentally different from membrane gas separation, which separate based on different amounts of absorption and different rates of diffusion. Ultrafiltration membranes are defined by the molecular weight cut-off (MWCO) of the membrane used. Ultrafiltration is applied in cross-flow or dead-end mode. Applications Ind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microfiltration
Microfiltration is a type of physical filtration process where a contaminated fluid is passed through a special pore-sized membrane filter to separate microorganisms and suspended particles from process liquid. It is commonly used in conjunction with various other separation processes such as ultrafiltration and reverse osmosis to provide a product stream which is free of undesired contaminants. General principles Microfiltration usually serves as a pre-treatment for other separation processes such as ultrafiltration, and a post-treatment for granular media filtration. The typical particle size used for microfiltration ranges from about 0.1 to 10 μm.Baker, R 2012, ''Microfiltration, in Membrane Technology and Applications'', 3rd edn, John Wiley & Sons Ltd, California. p. 303 In terms of approximate molecular weight these membranes can separate macromolecules of molecular weights generally less than 100,000 g/mol.Microfiltration/Ultrafiltration, 2008, Hyflux Membranes, accesse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Synthetic Polymers
Some familiar household synthetic polymers include: Nylons in textiles and fabrics, Teflon in non-stick pans, Bakelite for electrical switches, polyvinyl chloride (PVC) in pipes, etc. The common PET bottles are made of a synthetic polymer, polyethylene terephthalate. The plastic kits and covers are mostly made of synthetic polymers like polythene, and tires are manufactured from Buna rubbers. However, due to the environmental issues created by these synthetic polymers which are mostly non-biodegradable and often synthesized from petroleum, alternatives like bioplastics are also being considered. They are however expensive when compared to the synthetic polymers. Inorganic polymers *Polysiloxane *Polyphosphazene * Polyborazyline Organic polymers The eight most common types of synthetic organic polymers, which are commonly found in households are: *Low-density polyethylene (LDPE) *High-density polyethylene (HDPE) *Polypropylene (PP) * Polyvinyl chloride (PVC) *Polystyrene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Membrane
A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Biological membranes include cell membranes (outer coverings of cells or organelles that allow passage of certain constituents); nuclear membranes, which cover a cell nucleus; and tissue membranes, such as mucosae and serosae. Synthetic membranes are made by humans for use in laboratories and industry (such as chemical plants). This concept of a membrane has been known since the eighteenth century but was used little outside of the laboratory until the end of World War II. Drinking water supplies in Europe had been compromised by the war and membrane filters were used to test for water safety. However, due to the lack of reliability, slow operation, reduced selectivity and elevated costs, membranes were not widely exploited. The first us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Butter
Butter is a dairy product made from the fat and protein components of churned cream. It is a semi-solid emulsion at room temperature, consisting of approximately 80% butterfat. It is used at room temperature as a spread, melted as a condiment, and used as a fat in baking, sauce-making, pan frying, and other cooking procedures. Most frequently made from cow's milk, butter can also be manufactured from the milk of other mammals, including sheep, goats, buffalo, and yaks. It is made by churning milk or cream to separate the fat globules from the buttermilk. Salt has been added to butter since antiquity to help to preserve it, particularly when being transported; salt may still play a preservation role but is less important today as the entire supply chain is usually refrigerated. In modern times salt may be added for its taste. Food colorings are sometimes added to butter. Rendering butter, removing the water and milk solids, produces clarified butter or ''ghee'', which is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms ''colloid'' and ''emulsion'' are sometimes used interchangeably, ''emulsion'' should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include vinaigrettes, homogenized milk, liquid biomolecular condensates, and some cutting fluids for metal working. Two liquids can form different types of emulsions. As an example, oil and water can form, first, an oil-in-water emulsion, in which the oil is the dispersed phase, and water is the continuous phase. Second, they can form a water-in-oil emulsion, in which water is the dispersed phase and oil is the continuous phase. Multiple emulsions are also pos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Synthetic Polymers
Some familiar household synthetic polymers include: Nylons in textiles and fabrics, Teflon in non-stick pans, Bakelite for electrical switches, polyvinyl chloride (PVC) in pipes, etc. The common PET bottles are made of a synthetic polymer, polyethylene terephthalate. The plastic kits and covers are mostly made of synthetic polymers like polythene, and tires are manufactured from Buna rubbers. However, due to the environmental issues created by these synthetic polymers which are mostly non-biodegradable and often synthesized from petroleum, alternatives like bioplastics are also being considered. They are however expensive when compared to the synthetic polymers. Inorganic polymers *Polysiloxane *Polyphosphazene * Polyborazyline Organic polymers The eight most common types of synthetic organic polymers, which are commonly found in households are: *Low-density polyethylene (LDPE) *High-density polyethylene (HDPE) *Polypropylene (PP) * Polyvinyl chloride (PVC) *Polystyrene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reverse Osmosis
Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to separate ions, unwanted molecules and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by chemical potential differences of the solvent, a thermodynamic parameter. Reverse osmosis can remove many types of dissolved and suspended chemical species as well as biological ones (principally bacteria) from water, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective", this membrane should not allow large molecules or ions through the wiktionary:pore, pores (holes), but should allow smaller components of the solution (such as solvent molecules, e.g., water, H2O) to pass freely. In the normal osmosis process, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanofiltration
Nanofiltration is a membrane filtration process used most often to soften and disinfect water. Overview Nanofiltration is a Membrane technology, membrane filtration-based method that uses nanometer sized pores through which particles smaller than 10 nanometers pass through the membrane. Nanofiltration membranes have pore sizes from 1-10 nanometers, smaller than that used in microfiltration and ultrafiltration, but a little bit bigger than that in reverse osmosis. Membranes used are predominantly created from polymer thin films. Materials that are commonly used include polyethylene terephthalate or metals such as aluminum. Pore dimensions are controlled by pH, temperature and time during development with pore densities ranging from 1 to 106 pores per cm2. Membranes made from polyethylene terephthalate and other similar materials, are referred to as "track-etch" membranes, named after the way the pores on the membranes are made. "Tracking" involves bombarding the polymer thin fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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