Cerium
Cerium is a mineral and chemical element with symbol Ce and atomic number 58. It is one of the 14 chemical elements that follow lanthanum in the periodic table, thus called lanthanides. Cerium is located between lanthanum and praseodymium.
A metallic gray color similar to iron, ductile, it oxidizes easily on contact with air and turns reddish brown. Cerium is the most abundant of the rare earth elements, its abundance representing only 0.0046% by weight of the Earth's crust, where it appears dispersed in various minerals, such as cerite, bastnasite and monazite. There are numerous commercial applications of the cerium These uses include catalysts, fuel additives to reduce environmental pollution, and to glass and enamels to change their colors. Cerium oxide is an important component of powders used to polish glass and phosphors used in fluorescent lamps and displays. It is also used in the "stone" or "tinder" of the lighters (ferrocerium alloy).
Cerium was the first of the lanthanides to be discovered, in Bastnäs, Sweden, by Jöns Jakob Berzelius and Wilhelm Hisinger in 1803, and independently by Martin Heinrich Klaproth in Germany in the same year. In 1839 Carl Gustaf Mosander was the first to isolate the metal. Today, cerium and its compounds have a variety of uses: for example, cerium(IV) oxide is used to polish glass and is an important part of catalytic converters. The metallic cerium is used in ferrocerium igniters for its pyrophoric properties. Cerium-doped YAG phosphor is used in conjunction with blue light-emitting diodes to produce white light in most commercial white LED light sources.
History
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Cerium was discovered at Bastnäs in Sweden by Jöns Jakob Berzelius and Wilhelm Hisinger, and independently in Germany by Martin Heinrich Klaproth, both in 1803. Cerium was named by Berzelius after the asteroid Ceres, discovered two years earlier. The asteroid is named after the Roman goddess Ceres, goddess of agriculture, grain crops, fertility, and maternal relationships.
Cerium was originally isolated as its oxide, which was given the name ceria, a term that is still used today. The metal itself was too electropositive to be insulated with the foundry technology of the time, a characteristic of rare earth metals in general. Following Humphry Davy's development of electrochemistry five years later, the earths soon produced the metals they contained. Ceria, isolated in 1803, contained all the lanthanides present in the cerite ore from Bastnäs (Sweden), thus only containing 45% of what is known today as pure ceria. It was not until Carl Gustaf Mosander succeeded in extracting lantana and "didymy" in the late 1830s that pure ceria was obtained. Wilhelm Hisinger was a wealthy mine owner and amateur scientist, and a patron of Berzelius. He owned and controlled the Bastnäs mine, and had spent years trying to find out the composition of the abundant heavy gangue rock ('Bastnäs Tungsten', which despite its name did not contain tungsten), now known as cerite., which he had in his mine. Mosander and his family lived for many years in the same house as Berzelius, and Mosander was doubtless persuaded by Berzelius to do more research on ceria.
The element played a role in the Manhattan Project, where cerium compounds were investigated at the Berkeley site as crucible materials for smelting uranium and plutonium. For this reason, new methods for the preparation and smelting of cerium were developed within the scope of the Ames daughter project (now the Ames Laboratory). Production of extremely pure cerium at Ames began in mid-1944 and continued until August 1944. 1945.
It took its name from Ceres, the dwarf planet/asteroid that had been found two years earlier, specifically in 1801. It was in turn named after the Roman goddess of agriculture, Ceres.
Description
It is the most abundant and cheapest lanthanide. The metal is hard and steely gray in color, turning reddish brown. It is a good conductor of heat and electricity. Reacts with dilute acids and with water (producing hydrogen). It is unstable in dry air, covering itself with a layer of rust in moist air.
On Earth, cerium is almost as abundant as copper; especially in the form of cerium oxide, which is commonly used as abrasive powders for polishing glass. Cerium metal is pyrophoric, which means it catches fire easily. Cerium does not perform any known biological function.
The natural element is made up of the isotopes 136Ce, 138Ce, 140Ce and 142Ce. 142Ce is practically stable with a half-life of 5 x 1016 years. Cerium is found mixed with other rare earths in many minerals, particularly monazite and bastnasite, and is also found among the fission products of uranium, thorium, and plutonium.
Applications
- Catalytic converters for internal combustion engines.
- As a catalyst of the process cracking in the oil industry.
- Alloys used in lighters.
- Cerio oxide is used for lens polishing, optical and semiconductor instruments.
- In the alloys of the permanent magnets.
- As in the treatment of burns under the commercial name of flammacerium.
- It was used in meshes to increase the luminosity of gas lamps.
- Cerio's oxide fulfills the function of Opacificante in clear fries, which are used in formulation of vitreous enamel.
Pigments and phosphors
The photostability of pigments can be improved by adding cerium, as cerium provides pigments with light fastness and prevents light polymers from darkening in sunlight.
An example of a cerium compound used on its own as an inorganic pigment is bright red cerium(III) sulfide (cerium sulfide red), which remains chemically inert up to very high temperatures. The pigment is a safer alternative to lightfast but toxic cadmium selenide-based pigments.
The addition of cerium oxide to the old glass plates of cathode ray tubes for television was beneficial, since it suppressed the dimming effect by creating defects in the F-center due to the continuous bombardment of electrons during the functioning.
Cerium is also an essential component as a dopant for phosphors used in CRT television displays, fluorescent lamps, and later White Light Emitting Diodes. The most widely used example is yttrium aluminum garnet cerium(III)-doped (Ce:YAG) that emits green to yellow-green light (550-530 nm) and also behaves as a scintillator.
Other alloys and refractories
Salts of cerium, such as the sulfides Ce2S3 and Ce3S4 , were considered during the Manhattan Project as advanced refractory materials for crucible construction that could withstand the high temperatures and strongly reducing conditions when casting metallic plutonium. Despite their desirable properties, these sulfides were never widely adopted due to practical problems with their synthesis.
Cerium is used as an alloying element in aluminum to create castable eutectic aluminum alloys with 6–16 wt% Ce, to which additional Mg and/or Si can be added. These Al-Ce alloys have excellent high temperature resistance and are suitable for automotive applications for example in cylinder heads. Other cerium alloys include Pu-Ce and Pu-Ce-Co plutonium alloys, which have been used as nuclear fuel.
Minerals
The main cerium ores are cerite, bastnasite, and monazite.
Health Effects
Cerium oxide is an abrasive that can be found in some work environments, where it poses a risk when inhaled as fine particles. Prolonged exposure may cause pulmonary embolism. Cerium, like other lanthanides, can replace calcium in some metabolic processes. However, its absorption by the oral route is very low and does not constitute an immediate danger. Cerium chloride administered intravenously can induce cardiovascular and liver failure.
Effects on the environment
Cerium is dumped that when touched it oxidizes very easily in different places, mainly by oil-producing industries. It can also enter the environment when household equipment is thrown away. Cerium gradually accumulates in soils and soil water, and this eventually leads to increased concentrations in humans, animals, and soil particles. In aquatic animals it causes damage to cell membranes, which has several negative influences on reproduction and nervous system functions.
In literature
In The Periodic Table, the writer and chemist by profession Primo Levi dedicates the chapter "Cerium" to his stay in the Auschwitz concentration camp, where he survived thanks to the exchange of small ferrocerium rods for food.