Where Found (Encyclopedia of Global Resources)
Cadmium, a rare element, does not occur in nature in its elemental form. Its ore deposits are of insufficient concentration to permit direct mining. Cadmium is found in sulfides of zinc, lead, and copper and is typically obtained as a by-product of zinc. Main producers are China, South Korea, Canada, Kazakhstan, and Japan.
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Primary Uses (Encyclopedia of Global Resources)
Technical Definition (Encyclopedia of Global Resources)
Cadmium (abbreviated Cd), atomic number 48, belongs to Group IIB of the periodic table of the elements and resembles zinc in its chemical and physical properties. It has eight stable isotopes and an average molecular weight of 112.40. Pure cadmium is a lustrous, silver-white, malleable metal. Its specific gravity is 8.65, its melting point is 321° Celsius, and its boiling point is 765° Celsius.
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Description, Distribution, and Forms (Encyclopedia of Global Resources)
Cadmium is a rare element that is chemically and physically similar to zinc. Its concentration in the lithosphere is 0.1 to 0.2 gram per metric ton, making it the sixty-seventh most abundant element. The few known cadmium minerals include greenockite, hawleyite, cadmoselite, monteponite, otavite, and saukovite, none of which occurs in commercial deposits. Cadmium is concentrated principally in sulfide deposits. It frequently substitutes for zinc in zinc minerals, where it occurs as an impurity or a surface coating; it is found to a much lesser extent with lead and copper.
Cadmium is softer than zinc, is capable of taking a high polish, and alloys readily with other metals. Its characteristics make it particularly useful to the alloy, plating, and coating industries, some of its chief consumers. The United States produced approximately 750 metric tons of cadmium in 2008, and total world refinery production was about 21,000 metric tons. Cadmium is a toxic element; its toxicity has led to a search for alternative industrial materials and has heightened efforts to recycle cadmium-containing products.
Cadmium-containing zinc deposits occur in many diverse geological settings. Commercially, strata-bound deposits are the most important source of cadmium. Internationally, chief producers of cadmium are China, South Korea, Canada, Kazakhstan, and Mexico.
The most common cadmium minerals are the...
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History (Encyclopedia of Global Resources)
Cadmium was isolated and identified in 1817 by Friedrich Stromeyer. One of the earliest uses of cadmium sulfides was as a paint pigment. Commercial production of cadmium as a by-product of zinc smelting began in the nineteenth century. Cadmium was first produced in the United States on a pilot-plant scale; during World War I, production increased rapidly, and it continued to rise in the following decades.
Cadmium is toxic to almost all human body systems and plays no known part as a trace element in human metabolism. Cadmium elimination proceeds slowly enough that the element can accumulate in the body over time, with storage primarily in the kidneys and liver. Chronic exposure can lead to irreversible kidney disease and fluid in the lungs as well as to osteomalacia, an extremely painful softening of the bones. Cadmium can also induce hypertension and can cross the placenta to cause fetal damage. Victims of acute exposure may exhibit symptoms similar to those of food poisoning.
Industrial pollution has introduced cadmium into surface water, groundwater, and the air. Zinc mine tailings can be a source of environmental cadmium in regions where transporting waters are acidic. In Western Europe, where landfilling is less common than in the United States, incineration of plastics is a potential source of cadmium release to the atmosphere.
In the late 1960’s, itai-itai (literally “ouch-ouch”) disease was...
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Obtaining Cadmium (Encyclopedia of Global Resources)
Cadmium is entirely a by-product metal. It is obtained principally from the smelting and refining of sulfide ores of zinc, lead, and copper. Cadmium can be volatilized from the ores, recovered from the dust and fumes produced during ore roasting and sintering, or precipitated from electrolytic refining slimes.
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Uses of Cadmium (Encyclopedia of Global Resources)
Cadmium is a key component of alkaline nickel-cadmium batteries, accounting for 83 percent of world consumption. Although its use in consumer electronics has been declining as a result of the more popular lithium ion technologies, nickel-cadmium batteries are seeing new industrial applications, including electric vehicles and photovoltaic (solar-energy) systems.
Cadmium is also an important element in alloys. When alloyed with nickel or with silver and copper, it forms a high-pressure antifriction metal for automobile bearings. It hardens copper and makes silver resistant to tarnish. Cadmium plating forms a thin, rustless surface alloy, especially on iron and steel; it is electroplated onto vehicle and aircraft parts such as bolts, nuts, and locks to make them corrosion-resistant. It also provides an adhering bond between iron and other plating metals. Cadmium compounds are used in chemicals, photographic materials, television picture tubes, rubber, soaps, textile printing, and fireworks. Cadmium serves as a stabilizer for plastics and similar synthetic products. Cadmium sulfide forms a durable yellow pigment used in paints, glass, and enamels.
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Further Reading (Encyclopedia of Global Resources)
Adriano, Domy C. “Cadmium.” In Trace Elements in Terrestrial Environments: Biogeochemistry, Bioavailability, and Risks of Metals. 2d ed. New York: Springer, 2001.
Bhattacharyya, M. H., et al. “Biochemical Pathways in Cadmium Toxicity.” In Molecular Biology and Toxicology of Metals, edited by Rudolfs K. Zalups and James Koropatnick. New York: Taylor & Francis, 2000.
Dobson, S. Cadmium: Environmental Aspects. Geneva, Switzerland: World Health Organization, 1992.
Greenwood, N. N., and A. Earnshaw. “Zinc, Cadmium, and Mercury.” In Chemistry of the Elements. 2d ed. Boston: Butterworth-Heinemann, 1997.
Khan, Nafees A., and Samiullah, eds. Cadmium Toxicity and Tolerance in Plants. Oxford, England: Alpha Science, 2006.
Massey, A. G. “Group 12: Zinc, Cadmium, and Mercury.” In Main Group Chemistry. 2d ed. New York: Wiley, 2000.
Nordberg, G. F., R. F. M. Herber, and L. Alessio, eds. Cadmium in the Human Environment: Toxicity and Carcinogenicity. New York: Oxford University Press, 1992.
Scoullos, Michael J., ed. Mercury, Cadmium, Lead: Handbook for Sustainable Heavy Metals Policy and Regulation. Boston: Kluwer Academic, 2001.
Natural Resources Canada. Canadian Minerals Yearbook, Mineral and Metal Commodity Reviews....
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Cadmium (Chemical Elements)
Cadmium is a transition metal. The transition metals are the elements found in Rows 4 through 7 between Groups 2 and 13 in the periodic table, a chart that shows how elements are related. Cadmium was discovered by German chemist Friedrich Stromeyer (1776-1835) in 1817. It is found most commonly in ores of zinc.
Cadmium is a soft metal that is easily cut with a knife. It resembles zinc in many of its physical and chemical properties. However, it is much less abundant in the Earth's crust than zinc.
By far the most important use of cadmium in the United States is in the production of nicad (nickel-cadmium), or rechargeable, batteries. It is also used in pigments, coatings and plating, manufacture of plastic products, and alloys. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals.
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