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Encyclopedia > Filtration
diagram of a simple filtration
diagram of a simple filtration

Filtration is a mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium to fluid flow through which the fluid can pass, but the solids (or at least part of the solids) in the fluid are retained. It has to be emphasized that the separation is NOT complete, and it will depend on the pore size and the thickness of the medium as well as the mechanisms that occur during filtration. In mathematics, a filtration is an indexed set Si of subobjects of a given algebraic structure S, with an index set I that is a totally ordered set, subject only to the condition that if i ≤ j in I then Si is contained in Sj. ... The term filter may refer to: A device to separate mixtures. ... Image File history File links Filtration_diagram. ... Image File history File links Filtration_diagram. ...

  • Filtration is used for the purification of fluids: for instance separating dust from the atmosphere to clean ambient air.
  • Filtration, as a physical operation is very important in chemistry for the separation of materials of different chemical composition in solution (or solids which can be dissolved) by first using a reagent to precipitate one of the materials and then use a filter to separate the solid from the other material(s).
  • Filtration is also important and widely used as one of the unit operations of chemical engineering.

It is important not to confuse filtration with sieving. In sieving there is only a single layer of medium where size separation occurs purely by the fact that the fraction of the particulate solid matter which is too large to be able to pass through the holes of the sieve, scientifically called oversize (See particle size distribution) are retained. In filtration a multilayer medium is involved, where other mechanisms are included as well, for instance direct interception, diffusion and centrifugal action, where in this latter those particles, which are unable to follow the tortuous channels of the filter will also adhere to the structure of the medium and are retained.[1] The particle size distribution[1] (PSD) of a powder or granular material is a list of values or a mathematical function that defines the relative amounts of particles present, sorted according to size. ...


Depending on the application, either one or both of the components may be isolated. Examples of filtration include A) a coffee filter to keep the coffee separate from the grounds and B) the use of HEPA filters in air conditioning to remove particles from air. Used coffee filter A coffee filter is a coffee-brewing utensil, usually made of disposable paper, but recently stainless steel. ... HEPA (IPA: ) is a type of air filter. ... Note: in the broadest sense, air conditioning can refer to any form of heating, ventilation, and air-conditioning. ...


The filtration process separates particles and fluid from a suspension, and the fluid can be either a liquid or a gas (or a supercritical fluid). To separate a mixture of chemical compounds, a solvent is chosen which dissolves one component, while not dissolving the other. By dissolving the mixture in the chosen solvent, one component will go into the solution and pass through the filter, while the other will be retained. This is one of the most important techniques used by chemists to purify compounds. For other uses, see Liquid (disambiguation). ... For other uses, see Gas (disambiguation). ... A supercritical fluid is any substance at a temperature and pressure above its thermodynamic critical point. ... For other uses, see Solvent (disambiguation). ...


Filtration also cleans up water streams or other river streams. Furnaces use filtration to prevent the furnace elements from fouling with particulates. Pneumatic conveying systems often employ filtration to stop or slow the flow of material that is transported, through the use of a baghouse. To meet Wikipedias quality standards, this article or section may require cleanup. ...


The remainder of this article focuses primarily on liquid filtration.

Contents

Methods

There are many different methods of filtration; all aim to attain the separation of substances. This is achieved by some form of interaction between the substance or objects to be removed and the filter. In addition the substance that is to pass through the filter must be a fluid, i.e. a liquid or gas. In chemistry and chemical engineering, a separation process is a process that transforms a mixture of substances into two or more compositionally-distinct products. ... This box:      A fluid is defined as a substance that continually deforms (flows) under an applied shear stress regardless of how small the applied stress. ... For other uses, see Liquid (disambiguation). ... For other uses, see Gas (disambiguation). ...


The simplest method of filtration is to pass a solution of a solid and fluid through a porous interface so that the solid is trapped, while the fluid passes through. This principle relies upon the size difference between the particles making up the fluid, and the particles making up the solid. In the laboratory, a Büchner funnel is often used, with a filter paper serving as the porous barrier. A Büchner funnel connected to a flask with a tube leading to a vacuum pump Büchner funnel is a piece of laboratory equipment used in suction filtration. ... Filter paper is a semi-permeable paper barrier placed perpendicular to a liquid flow and is used to separate fine solids from liquids. ...


For example an experiment to prove the existence of microscopic organisms involves the comparison of water passed through unglazed porcelain and unfiltered water. When left in sealed containers the filtered water takes longer to go foul, showing that very small items (such as bacteria) can be removed from fluids by filtration.[citation needed] Alternate methods often take the form of electrostatic attractions. These form of filters again have the problem of either becoming clogged, or the active sites on the filter all become used by the undesirable. However, most chemical filters are designed so that the filter can be flushed with a chemical that will remove the undesirables and allow the filter to be re-used. A cluster of Escherichia coli bacteria magnified 10,000 times. ... “Fine China” redirects here. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Electrostatics is the branch of physics that deals with the force exerted by a static (i. ...


Flowing

Liquids usually flow through the filter by gravity. This is the simplest method, and can be seen in the coffeemaker example. For chemical plants, this is usually the most economical method as well. In the laboratory, pressure in the form of compressed air may be applied to make the filtration process faster, though this may lead to clogging or the passage of fine particles. Alternatively, the liquid may flow through the filter by the force exerted by a pump. In this case, the filter need not be mounted vertically.


Filter media

There are two main types of filter media — a solid sieve which traps the solid particles, with or without the aid of filter paper, and a bed of granular material which retains the solid particles as it passes. The first type allows the solid particles, i.e. the residue, to be collected intact; the second type does not permit this. However, the second type is less prone to clogging due to the greater surface area where the particles can be trapped. Also, when the solid particles are very fine, it is often cheaper and easier to discard the contaminated granules than to clean the solid sieve.


Filter media can be cleaned by rinsing with solvents or detergents. Alternatively, in engineering applications, such as swimming pool water treatment plants, they may be cleaned by backwashing. Backwash is the backwards flow of air or water. ...


Examples of the first type include filter paper used with a Buchner, Hirsch, filter funnel or other similar funnel. A sintered-glass funnel is often used in chemistry laboratories because it is able to trap very fine particles, while permitting the particles to be removed by a spatula.


Examples of the second type include filters at municipal and swimming pool water treatment plants, where the granular material is sand. In the laboratory, Celite or diatomaceous earth is packed in a Pasteur pipette (microscale) or loaded on top of a sintered-glass funnel to serve as the filter bed. Diatomaceous earth, also known as diatomite, kieselguhr, kieselgur, and Celite, is a naturally occurring, soft, chalk-like, sedimentary rock mineral that is easily crumbled into a fine white to off-white powder. ... A sample of diatomaceous earth Diatomaceous earth (IPA: , also known as DE, diatomite, diahydro, kieselguhr, kieselgur and Celite) is a naturally occurring, soft, chalk-like sedimentary rock that is easily crumbled into a fine white to off-white powder. ... A picture is needed here. ...



The following points should be considerd while selecting the filter media:

  • ability to build the solid.
  • minimum resistance to flow the filtrate.
  • resistance to chemical attack.
  • minimum cost.
  • long life.

Filter aid

Certain filter aids may be used to aid filtration. These are often incompressible diatomaceous earth or kieselguhr, which is composed primarily of silica. Also used are wood cellulose and other inert porous solids. The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ...


These filter aids can be used in two different ways. They can be used as a precoat before the slurry is filtered. This will prevent gelatinous-type solids from plugging the filter medium and also give a clearer filtrate. They can also be added to the slurry before filtration. This increases the porosity of the cake and reduces resistance of the cake during filtration. In a rotary filter, the filter aid may be applied as a precoat; subsequently, thin slices of this layer are sliced off with the cake. A slurry is in general a thick suspension of solids in a liquid and may be: Look up slurry in Wiktionary, the free dictionary. ... A slurry is in general a thick suspension of solids in a liquid and may be: Look up slurry in Wiktionary, the free dictionary. ... Porosity is a measure of the void spaces in a material, and is measured as a fraction, between 0–1, or as a percentage between 0–100%. The term porosity is used in multiple fields including manufacturing, earth sciences and construction. ...


The use of filter aids is usually limited to cases where the cake is discarded or where the precipitate can be separated chemically from the filter. Precipitation is the condensation of a solid from a solution during a chemical reaction. ...


Alternatives

Filtration is a more efficient method for the separation of mixtures than decantation, but is much more time consuming. If very small amounts of solution are involved, most of the solution may be soaked up by the filter medium. Barring a few exceptions, almost every element or compound is found in an impure state i. ... Acid-base extraction is a procedure using sequential liquid-liquid extractions to purify acids and bases from mixtures based on their chemical properties. ... For the Second Person album, see Chromatography (album). ... Frost crystallization on a shrub. ... Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids. ... Laboratory distillation set-up: 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed control 13: Stirrer/heat plate... Drying is a mass transfer process resulting in the removal of water moisture or moisture from another solvent, by evaporation from a solid, semi-solid or liquid (hereafter product) to end in a solid state. ... Electrochromatography is a chemical separation technique in analytical chemistry, biochemistry and molecular biology used to resolve and separate mostly large biomolecules such as proteins. ... This article needs additional references or sources for verification. ... Froth Flotation is a selective process for separating minerals from gangue by using surfactants and wetting agents. ... Liquid-liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds based on their solution preferences for two different immiscible liquids, usually water and an organic solvent. ... Insulin crystals Recrystallization is an essentially physical process that has meanings in chemistry, metallurgy and geology. ... Sedimentation describes the motion of particles in solutions or suspensions in response to an external force such as gravity, centrifugal force or electric force. ... This article does not cite any references or sources. ... Image File history File links ChemSepProcDiagram. ... An API oil-water separator is a device designed to separate gross amounts of oil and suspended solids from the wastewater effluents of oil refineries, petrochemical plants, chemical plants, natural gas processing plants and other industrial sources. ... This article is about the scientific device. ... Mixer-settlers are used when there will only be one equilibrium stage in the process. ... A protein skimmer or foam fractionator is a device used mostly in saltwater aquaria to remove organic compounds from the water before they break down into nitrogenous waste. ... The term still is a contraction of the verb to distill. A still is an apparatus used to distill miscible or immiscible (eg. ... Simple sublimation apparatus. ... Aqueous biphasic systems (ABS)or aqueous two phase systems are clean alternatives for traditional organic-water solvent extraction systems. ... This article needs more context around or a better explanation of technical details to make it more accessible to general readers and technical readers outside the specialty, without removing technical details. ... A eutectic or eutectic mixture is a mixture of two or more elements which has a lower melting point than any of its constituents. ... In chemistry and chemical engineering, a separation process is a process that transforms a mixture of substances into two or more compositionally-distinct products. ... For the decanting of wine, see Decanter. ... Making a saline water solution by dissolving table salt (NaCl) in water This article is about chemical solutions. ...


An alternative to filtration is centrifugation — instead of filtering the mixture of solid and liquid particles, the mixture is centrifuged to force the (usually) denser solid to the bottom, where it often forms a firm cake. The liquid above can then be decanted. This method is especially useful for separating solids which do not filter well, such as gelatinous or fine particles. These solids can clog or pass through the filter, respectively. Centrifugation is a process that involves the use of the centrifugal force for the separation of mixtures. ...


Filter types

  • Gravity filter (open system that operates with water column pressure only)
  • Pressure filter (closed system that operates under pressure from a pump)
  • Side stream filter (filter in a closed loop, that filters part of the media per cycle only)
  • Continuous rotary filters

In kidney

Main article: Renal filtration

The kidney works by filtration of blood in the glomerulus, followed by selectively reabsorbing many substances essential for the body. The kidneys are the organs that filter wastes (such as urea) from the blood and excrete them, along with water, as urine. ... For other uses, see Blood (disambiguation). ... Glomerulus refers to two unrelated structures in the body, both named for their globular form. ...


See also

Look up filtration in
Wiktionary, the free dictionary.

Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ... In chemistry and chemical engineering, a separation process is a process that transforms a mixture of substances into two or more compositionally-distinct products. ... Microfiltration is a filtration process which removes contaminants from a fluid or gas by passage through a microporous membrane. ... Ultrafiltration (UF) is a variety of membrane filtration in which hydrostatic pressure forces a liquid against a semipermeable membrane. ... Nanofiltration is a relatively recent membrane process used most often with low TDS waters such as surface water and fresh groundwater, with the purpose of softening (polyvalent cation removal) and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter [1] [2]. Nanofiltration is also... Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. ... An industrial water filter with geared motor A water filter is a device which removes impurities from water by means of a fine physical barrier, chemical processes and/or biological process. ...

Footnotes

  1. ^ Lecture notes, Postgraduate course on Filtration and Size separation at the Department of Chemical Engineering, University of Lougborough, England

References

Air filter Engineering (M) Sdn. Bhd.


Further reading

  • www.filtsep.com
  • filtration equipment expert system and data analysis

  Results from FactBites:
 
Filtration (1026 words)
Filtration is a technique used either to remove impurities from an organic solution or to isolate an organic solid.
Hot gravity filtrations are no longer included in the routine procedures for the experiments in the organic chemistry teaching labs, they used to be used in the teaching labs to remove powdered Norite from a hot solution; since we switched to pelletized Norite, hot filtrations are not used.
Vacuum filtration is used primarily to collect a desired solid, for instance, the collection of crystals in a recrystallization procedure.
Filtration - Wikipedia, the free encyclopedia (473 words)
In chemistry, alchemy and water treatment, filtration is the process of using a filter to mechanically separate a mixture.
The simplest method of filtration is to pass a solution of a solid and fluid through a porous interface so that the solid is trapped, while the fluid passes through.
Filtration is a more efficient method for the separation of mixtures than decantation, but is much more time consuming.
  More results at FactBites »

 
 

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