A sieve for selecting cesium.A sieve for selecting cesium cesium (sē`zēəm) [Lat.,=bluish gray], a metallic chemical element; symbol Cs; at. no. 55; at. wt. 132.9054; m.p. 28.4°C;; b.p. 669.3°C;; sp. gr. 1.873 at 20°C;; valence +1. One of the more deadly products of a nuclear reactor accident is the radioactive isotope radioactive isotope or radioisotope, natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached. cesium-137. Because this metal vaporizes easily, winds can carry it over long distances, contaminating large areas. Two researchers have now discovered a form of the mineral mica that acts as a highly selective sieve for capturing cesium ions. Such an ion trap could be useful for decontaminating the environment after accident releases of nuclear material. Sridhar Komarneni and Rustum Roy of Pennsylvania State University Pennsylvania State University, main campus at University Park, State College; land-grant and state supported; coeducational; chartered 1855, opened 1859 as Farmers' High School. in University Park report their discovery in the March 11 SCIENCE. The researchers start with samples of a naturally occurring mineral known as phlogopite phlog·o·pite n. A yellow to dark brown mica, K(Mg,Fe)3AlSi3O10(OH)2, used in insulation. [Greek phlog mica. The mineral is ground into a fine powder and then chemically treated to replace its potassium ions with sodium ions and water molecules. This process increases the spacing between the layers that make up the mica's structure. The modified material, when immersed in a cesium-containing solution, readily sodium ions while taking in cesium ions. Presently, clay minerals and zeolites, both naturally occuring and synthetic, are used extensively in the decontamination decontamination /de·con·tam·i·na·tion/ (de?kon-tam-i-na´shun) the freeing of a person or object of some contaminating substance, e.g., war gas, radioactive material, etc. de·con·tam·i·na·tion n. and disposal of radioactive wastes. For example, after the Chernobyl nuclear accident, the mineral mordenite was added to animal feed in Sweden to remove cesium-137 from the gastrointestinal tracts of contaminated contaminated, v 1. made radioactive by the addition of small quantities of radioactive material. 2. made contaminated by adding infective or radiographic materials. 3. an infective surface or object. animals. The use of modified, powdered mica offers greater selectivity for cesium and much better resistance to acidic conditions like those found in an animal's stomach. Komarneni and Roy suggest that the mica powder can be used for decontamination by dispersing it in water or soil and then filtering out the cesium-laden product or by letting cesium-contaminated humans or animals ingest in·gest tr.v. in·gest·ed, in·gest·ing, in·gests 1. To take into the body by the mouth for digestion or absorption. See Synonyms at eat. 2. the material, which would later be excreted. The newly discovered cesium ion sieve, the researchers say, "not only selectively exchanges cesium ions but also immobilizes them at room temperature through chemical bonding that. . . leads to the formation of a crystalline waste form at room temperature." |
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