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leach

  (lēch) pronunciation

v., leached, leach·ing, leach·es.

v.tr.
  1. To remove soluble or other constituents from by the action of a percolating liquid.
  2. To empty; drain: “a world leached of pleasure, voided of meaning” (Marilynne Robinson).
v.intr.

To be dissolved or passed out by a percolating liquid.

n.
  1. The act or process of leaching.
  2. A porous, perforated, or sievelike vessel that holds material to be leached.
  3. The substance through which a liquid is leached.

[From Middle English leche, leachate, from Old English *lece, muddy stream; akin to leccan, to moisten.]

leachability leach'a·bil'i·ty n.
leachable leach'a·ble adj.
leacher leach'er n.
 
 
Sci-Tech Encyclopedia: Leaching

The removal of a soluble fraction, in the form of a solution, from an insoluble, permeable solid with which it is associated. The separation usually involves selective dissolving, with or without diffusion, but in the extreme case of simple washing it consists merely of the displacement (with some mixing) of one interstitial liquid by another with which it is miscible. The soluble constituent may be solid (as the metal leached from ore) or liquid (as the oil leached from soybeans).

Leaching is closely related to solvent extraction, in which a soluble substance is dissolved from one liquid by a second liquid immiscible with the first. Both leaching and solvent extraction are often called extraction. Because of its variety of applications and its importance to several ancient industries, leaching is known by a number of other names: solid-liquid extraction, lixiviation, percolation, infusion, washing, and decantation-settling. The liquid used to leach away the soluble material (the solute) is termed the solvent. The resulting solution is called the extract or sometimes the miscella.

Leaching processes fall into two principal classes: those in which the leaching is accomplished by percolation (seeping of solvent through a bed of solids), and those in which particulate solids are dispersed into the extracting liquid and subsequently separated from it. In either case, the operation may be a batch process or continuous. See also Extraction; Filtration; Solvent extraction.

 
Thesaurus: leach

verb

    To flow or leak out or emit something slowly: bleed, exude, ooze, percolate, seep, transpire, transude, weep. See move/halt, solid/liquid/consistency.

 
Geography Dictionary: leaching

The movement of water down the soil profile. This results in the movement of cations, sesquioxides, clay colloids, and humus to the lower soil horizons. Specific types of leaching include: lixiviation—the removal of the soluble salts containing metallic cations; the removal of chelates; lessivage; and, in tropical soils, desilication.

 
Britannica Concise Encyclopedia: leaching

Loss of soluble substances and colloids from the top layer of soil by percolating precipitation. The materials are carried downward and are generally redeposited in a lower layer. This transport results in a porous and open top layer and a dense, compact lower layer. In areas of extensive leaching, the remaining quartz and hydroxides of iron, manganese, and aluminum form laterite. In such areas rapid bacterial action results in the absence of humus in the soil, because fallen plant material is oxidized and the products are leached away.

For more information on leaching, visit Britannica.com.

 
Architecture: leaching


1. The process of separating a liquid from a solid (as in waste liquid) by percolation into the surrounding soil.
2. The process of allowing soluble nutrients to move downward and percolate through the surrounding soil.

 
Columbia Encyclopedia: leaching,
method of extraction in which a solvent is passed through a mixture to remove some desired substance from it. A simple example is the passage of boiling water through ground coffee to dissolve and carry out the chemicals necessary for producing the beverage. Another example is the removal of sugar from sugar beets using water as the solvent. Leaching is also used to remove metals from their ores. In one procedure certain crushed ores of copper are placed into a series of tanks. As a solvent, such as sulfuric acid, is pumped into the first tank, it dissolves the copper from the ore. Eventually overflowing the first tank, the solution passes into the second, where more copper is dissolved. When this tank overflows, the process is repeated in the third tank and so on. The copper is ultimately removed from the solution by chemical or other treatment.

 
Gardener's Dictionary: leaching

The loss of nutrients when rain or irrigation carries them down through the soil and out of the root zone.

 
Wikipedia: leaching

Leaching is the process of extracting a substance from a solid by dissolving it in a liquid.

Agriculture

In agriculture, leaching may refer to the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planning, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss. Leaching may also refer to the practice of applying a small amount of excess irrigation where the water has a high salt content to avoid salts from building up in the soil (salinity control). Where this is practiced, drainage must also usually be employed, to carry away the excess water.

Leaching is an environmental concern when it contributes to groundwater contamination. As water, from rain, flooding or other sources, seeps into the ground, it can dissolve chemicals and carry them into the underground water supply. Of particular concern are hazardous waste dumps and landfills, and, in agriculture, excess fertilizer and improperly stored animal manure.

Cooking

In cooking, leaching is the same as parboiling and used on removing toxic or foul-tasting substances off the foodstuffs. The best known example is removal of toxic gyromitrin off the false morel mushrooms. Brewing of tea and coffee can similarly be considered as leaching process.

Pedogenesis

In pedology, leaching is the loss of mineral and organic solutes due to percolation. It is a mechanism of soil formation. It is distinct from the soil forming process of eluviation, which is the loss of mineral and organic colloids. Leached and elluviated materials tend to be lost from top soil and deposited in subsoil. A soil horizon accumulating leached and eluviated materials is referred to as a zone of illuviation.

Chemical leaching

In the chemical processing industry, leaching is known as extraction. Leaching has a variety of commercial applications, including separation of metal from ore using acid, and sugar from beets using hot water. Chloride can also be leached from food.

In a typical leaching operation, the solid mixture to be separated consists of particles, inert insoluble carrier A and solute B. The solvent, C, is added to the mixture to selectively dissolve B. The overflow from the stage is free of solids and consists of only solvent C and dissolved B. The underflow consists of slurry of liquid of similar composition in the liquid overflow and solid carrier A. In an ideal leaching equilibrium stage, all the solute is dissolved by the solvent; none of the carrier is dissolved. The mass ratio of the solid to liquid in the underflow is dependent on the type of equipment used and properties of the two phases.

Metallurgical application of leaching

Leaching is widely used in extractive metallurgy since many metals can form soluble salts in aqueous media. Compared to pyrometallurgical operations, leaching is easier to perform and much less harmful, because no gaseous pollution occurs. The only drawback of leaching is its lower efficiency caused by the low temperatures of the operation, which dramatically affect chemical reaction rates.

There are a variety of leaching processes, usually classified by the types of reagents used in the operation. The reagents required depend on the ores or pretreated material to be processed. A typical feed for leaching is either oxide or sulfide.

For material in oxide form, a simple acid leaching reaction can be illustrated by the zinc oxide leaching reaction :

ZnO + H2SO4 → ZnSO4 + H2O

In this reaction solid ZnO dissolves, forming soluble zinc sulfate.

In many cases other reagents are used to leach oxides. For example, in the metallurgy of aluminium, aluminium oxide is subject to leaching by alkali solutions:

Al2O3 + 3H2O + 2NaOH → 2NaAl(OH)4

Leaching of sulfides is a more complex process due to the refractory nature of sulfide ores. It often involves the use of pressurized vessels, called autoclaves. A good example of the autoclave leach process can be found in the metallurgy of zinc. It is best described by the following chemical reaction:

2ZnS + O2 + 2H2SO4 → 2ZnSO4 + 2H2O + 2S

This reaction proceeds at temperatures above the boiling point of water, thus creating a vapor pressure inside the vessel. Oxygen is injected under pressure, making the total pressure in the autoclave more than 0.6 MPa.

See also

References


This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

 
Translations: Translations for: Leach

Dansk (Danish)
v. tr. - filtrere, udlude, udvaske
v. intr. - blive udludet
n. - filtrering

Nederlands (Dutch)
uitlogen, percoleren

Français (French)
v. tr. - lessiver
v. intr. - s'infiltrer (une substance)
n. - fosse

Deutsch (German)
v. - durchsickern lassen, auslaugen
n. - Auslaugen, Blutegel

Ελληνική (Greek)
v. - διυλίζω, φιλτράρω, απονιτρώνω ή εκπλένω (μετάλλευμα), (μτφ.) στραγγίζω
n. - απόσταξη, φιλτράρισμα, διϋλιση, απόσταγμα, φίλτρο, αποστακτήρας

Italiano (Italian)
biancheggiare

Português (Portuguese)
v. - fazer lixívia
n. - lixívia (f) (Quím.)

Русский (Russian)
щелок, раствор соли, выщелачивать

Español (Spanish)
v. tr. - lixiviar, colar la ropa
v. intr. - lixiviar, colar la ropa
n. - cenizas de lejía, colada

Svenska (Swedish)
v. - filtrera, luta ut, laka ur, vaska ur
n. - lutkärl, lutbalja, lutaska, lake, lösning

中文（简体） (Chinese (Simplified))
过滤, 水浸, 萃取, 被过滤, 被滤掉, 被溶滤, 滤灰槽, 过滤器

中文（繁體） (Chinese (Traditional))
v. tr. - 過濾, 水浸, 萃取
v. intr. - 被過濾, 被濾掉, 被溶濾
n. - 過濾, 濾灰槽, 篩檢程式

한국어 (Korean)
v. tr. - 거르다, 물에 담가 우리다
v. intr. - 여과되다, 스며 나오다, 걸러지다
n. - 거르기, 여과된 액체, 잿물, 여과기

日本語 (Japanese)
v. - こす, 水でこす, こして取る, 浸出する
n. - ろ過

العربيه (Arabic)
‏(فعل) يرشح, يصفي, يروق, يرتشح (الاسم) وعاء الترشيح, عمليه الترشيح‏

עברית (Hebrew)
v. tr. - ‮סינן‬
v. intr. - ‮שטף ע"י חלחול, סילק חומר מסיס‬
n. - ‮מסנן, מסננת, סינון, תמיסה, חומר שעבר תהליך סינון‬

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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.  Read more
Thesaurus. Roget's II: The New Thesaurus, Third Edition by the Editors of the American Heritage® Dictionary Copyright © 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.  Read more
Geography Dictionary. A Dictionary of Geography. Copyright © Susan Mayhew 1992, 1997, 2004. All rights reserved.  Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Architecture. McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/  Read more
Gardener's Dictionary. Taylor's Dictionary for Gardeners, by Frances Tenenbaum. Copyright © 1997 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Leaching".  Read more
Translations. Copyright © 2007, WizCom Technologies Ltd. All rights reserved.  Read more

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