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adsorption
adsorption Dissolved constituents in groundwater are attracted to the surfaces of minerals lining the pores through which the water flows. This process is generally referred to as adsorption. The dissolved constituents can be of natural origin, e.g. derived from minerals through dissolution by the coexisting water. They can also be of anthropogenic origin, introduced into the environment by a variety of industrial processes.
Dissolved constituents are generally present as charged ions. They have a positive charge (such as the metal cation Pb2+) or a negative charge (e.g. arsenate, AsO42–). Similarly, the mineral surfaces have an electric charge because the metal ions (Me) forming the structure of the minerals are not fully coordinated with oxygen at the surface of the mineral (>Me-O−). The surface is then made neutral by a H+ ion from the water (>Me–OH). This mineral surface charge is further affected by the acidity (pH) of the groundwater. In general, minerals have a positive charge in water that has high acidity (a high concentration of H+ or low pH) and a negative charge in waters that have a low acidity (a low concentration of H+ or high pH). The mineral surface generally has a zero charge in neutral waters (intermediate pH). Taking the surface of the mineral feldspar as an example, we can represent its surface as >MeOH2+ at low pH and as >Me-O− at high pH (> denotes the mineral surface). It follows that positively charged metal cations (e.g. Pb2+) adsorb to feldspar at high pH (>Me-OPb+) and that negatively charged ions (anions), such as arsenate, adsorb to feldspars at low pH (>Me-OH2AsO4−). Understanding mineral surfaces and water pH is thus of prime importance for predicting how polluted water will evolve. Adsorbed ions form either strong direct bonds with the surface (inner sphere complex, e.g. Pb2+) or weak electrostatic bonds (e.g. Na+). Weaker electrostatic bonding is a result of Na+ being firmly coordinated with four water molecules (Na(H2O)4+) which act as a ‘shield’ to prevent direct bonding. K. Vala Ragnarsdottir |
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PAUL HANCOCK and BRIAN J. SKINNER. "adsorption." The Oxford Companion to the Earth. 2000. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. PAUL HANCOCK and BRIAN J. SKINNER. "adsorption." The Oxford Companion to the Earth. 2000. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O112-adsorption.html PAUL HANCOCK and BRIAN J. SKINNER. "adsorption." The Oxford Companion to the Earth. 2000. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O112-adsorption.html |
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adsorption
adsorption adhesion of the molecules of liquids, gases, and dissolved substances to the surfaces of solids, as opposed to absorption , in which the molecules actually enter the absorbing medium (see adhesion and cohesion ). Certain solids have the power to adsorb great quantities of gases. Charcoal, for example, which has a great surface area because of its porous nature, adsorbs large volumes of gases, including most of the poisonous ones, and is therefore used in gas masks. Certain finely divided solids have great adsorptive properties; for example, minute particles of platinum attract and hold multitudes of hydrogen molecules on their surfaces. Its ability to adsorb other gases makes platinum very useful in the production of sulfuric acid by the contact process and in the preparation of ammonia. Adsorption occurs also in solutions; colloidal particles suspended in a solution may adsorb much of the solvent (see colloid ). Bone black and charcoal are used in industry to remove colors from solutions, since they adsorb many coloring materials and carry these with them when separated from the solution. Liquid dye held to the surface of cloth by adsorption permeates the fibers so that when the liquid has evaporated the dye still remains. Adsorption is employed in the hydrogenation of oils, in gas analysis, and in chromatography, a method used in the chemical analysis of closely related substances. |
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"adsorption." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. "adsorption." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1E1-adsorpti.html "adsorption." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-adsorpti.html |
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adsorption
adsorption The physical binding of a particle of a particular substance to the surface of another by adhesion or penetration. In soils it is the attachment of an ion, molecule, or compound to the charged surface of a particle, usually of clay or humus, where it may be subsequently replaced or exchanged. Ions carrying positive charges (e.g. those of calcium, magnesium, sodium, and potassium) become attached to, or adsorbed by, negatively charged surfaces (e.g. those of clay or humus).
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MICHAEL ALLABY. "adsorption." A Dictionary of Ecology. 2004. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "adsorption." A Dictionary of Ecology. 2004. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O14-adsorption.html MICHAEL ALLABY. "adsorption." A Dictionary of Ecology. 2004. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O14-adsorption.html |
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adsorption
adsorption The physical binding of a particle of a particular substance to the surface of another by adhesion or penetration. In soils, it is the attachment of an ion, molecule, or compound to the charged surface of a particle, usually of clay or humus, where replacement or exchange may take place. Ions carrying positive charges (e.g. those of calcium, magnesium, sodium, and potassium) become attached to, or adsorbed by, negatively charged surfaces (e.g. those of clay or humus).
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MICHAEL ALLABY. "adsorption." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "adsorption." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O7-adsorption.html MICHAEL ALLABY. "adsorption." A Dictionary of Plant Sciences. 1998. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O7-adsorption.html |
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adsorption
adsorption The formation of a layer of solid, liquid, or gas on the surface of a solid or, less frequently, of a liquid. There are two types depending on the nature of the forces involved. In chemisorption a single layer of molecules, atoms, or ions is attached to the adsorbent surface by chemical bonds. In physisorption adsorbed molecules are held by the weaker physical forces. The property is utilized in adsorption chromatography.
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"adsorption." A Dictionary of Biology. 2004. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. "adsorption." A Dictionary of Biology. 2004. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O6-adsorption.html "adsorption." A Dictionary of Biology. 2004. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-adsorption.html |
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adsorption
adsorption Attraction of a gas or liquid to the surface of a solid or liquid.It involves attraction of molecules at the surface, unlike absorption which implies incorporation. The amounts adsorbed and the rate of adsorption depend on the structure exposed, the chemical identities and concentrations of the substances involved, and the temperature. Corrosion on the surface of a metal involves a chemical adsorption.
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"adsorption." World Encyclopedia. 2005. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. "adsorption." World Encyclopedia. 2005. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O142-adsorption.html "adsorption." World Encyclopedia. 2005. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-adsorption.html |
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adsorption
adsorption The attachment of an ion, molecule, or compound to the charged surface of a particle, usually of clay or humus, from where it may be subsequently replaced or exchanged. Ions carrying positive charges (e.g. those of calcium, magnesium, sodium, and potassium) become attached to, or adsorbed by, negatively charged surfaces (e.g. those of clay or humus).
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AILSA ALLABY and MICHAEL ALLABY. "adsorption." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "adsorption." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O13-adsorption.html AILSA ALLABY and MICHAEL ALLABY. "adsorption." A Dictionary of Earth Sciences. 1999. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-adsorption.html |
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adsorption
adsorption (ăd-sorp-shŏn) n. the formation of a layer of atoms or molecules of one substance on the surface of a solid or liquid of different substance. See adsorbent.
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"adsorption." A Dictionary of Nursing. 2008. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. "adsorption." A Dictionary of Nursing. 2008. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O62-adsorption.html "adsorption." A Dictionary of Nursing. 2008. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O62-adsorption.html |
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