Molybdenum
- Molybdenum is a trace element found in a wide variety of foods. Foods that grow above ground — such as peas, leafy vegetables (including Broccoli and Spinach) and Cauliflower — tend to be higher in molybdenum than meat and foods that grow below the ground, such as Potatoes.
- Foods particularly high in molybdenum include nuts, tinned vegetables, and cereals such as oats.
- You should be able to get all the molybdenum you need from your daily diet.
The metal is silvery white, very hard transition metal, but is softer and more ductile than tungsten. Scheele discovered it in 1778. It was often confused with graphite and lead ore. It has a high elastic modulus, and only tungsten and tantalum, of the more readily available metals, have higher melting points. Molybdenum has one of the highest melting points of all pure elements. Molybdenum is attacked slowly by acids.
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[edit] Applications
Molybdenum is a valuable alloying agent, as it contributes to the hardenability and toughness of quenched and tempered steels. It also improves the strength of steel at high temperatures. Molybdenum is used in alloys, electrodes and catalysts. The Second World War German artillery piece called "Big Bertha" contains molybdenum as an essential component of its steel.
It is used in certain Nickel-based alloys, such as the "Hastelloys(R)" which are heat-resistant and corrosion-resistant to chemical solutions. Molybdenum oxidizes at elevated temperatures. The metal has found recent application as electrodes for electrically heated glass furnaces and foreheaths. The metal is also used in nuclear energy applications and for missile and aircraft parts. Molybdenum is valuable as a catalyst in the refining of petroleum. It has found applications as a filament material in electronic and electrical applications. Molybdenum is an essential trace element in plant nutrition. Some lands are barren for lack of this element in the soil. Molybdenum sulfide is useful as a lubricant, especially at high temperatures where oils would decompose. Almost all ultra-high strength steels with minimum yield points up to 300,000 psi(lb/in.2) contain molybdenum in amounts from 0.25 to 8%.
Molybdenum powders are used in circuit inks for circuit boards, and in microwaves devices and heat sinks for solid-state devices.
[edit] Molybdenum in the environment
Molybdenum differs from the other micronutrients in soils in that it is less soluble in acid soils and more soluble in alkaline soils, the result being that its availability to plants is sensitive to pH and drainage conditions. Some plants can have up to 500 ppm of the metal when they grow on alkaline soils.
Molybdenite is the chief mineral ore, with wulfenite being less important. Some molybdenite is obtained as a by-product of tungsen and copper production. The main mining areas are the USA, Chile, Canada and Russia, with world production being around 90.000 tonnes per year, and reserves amounting to 12 million tonnes of which 5 million tonnes are in the USA.
[edit] Health effects of molybdenum
Based on animal experiments, molybdenum and its compounds are highly toxic. Some evidence of liver dysfunction with hyperbilirubinemia has been reported in workmen chronically exposed in a Soviet Mo-Cu plant. In addition, signs of gout have been found in factory workers and among inhabitants of Mo-rich areas of Armenia. The main features were joint pains in the knees, hands, feet, articular deformities, erythema, and edema of the joint areas
[edit] Environmental effects of molybdenum
Molybdenum is essential to all species. As with other trace metals, though, what is essential in tiny amounts can be highly toxic at larger doses. Animal experiment have shown that too much molybdenum causes fetal deformities. Fodder with more than 10 ppm of molybdenum would put most livestok at risk.
[edit] Common Uses for Molybdenum
Molybdenum is a relatively nontoxic heavy metal that is silvery-white in appearance. The element was originally discovered in 1781 by a scientist from Sweden named Peter Hjelm. Molybdenum occurs naturally in two main forms: molybdenite and wulfenite. Both forms can be mined and used in industrial processes, or refined to yield pure molybdenum for recombination into other useful compounds.
[edit] Steel
Molybdenum's extremely high melting temperature makes it a valuable additive to steel alloys. Adding molybdenum makes steel stronger and more heat resistant. Steels that utilize molybdenum occur in objects such as light bulb filaments and rifle barrels. According to the Mineral Information Institute, the steel industry uses 75 percent of the molybdenum mined from the earth.
[edit] Enzymes
Plants and animals need trace amounts molybdenum to live. Certain key enzymes, such as one in plants that enables them to utilize nitrogen, require molybdenum to function properly. Plants cannot grow in Soil that is completely devoid of molybdenum. Since all animals ultimately depend on plants for food, animals could not exist in an area with molybdenum-bare soil either.
[edit] Catalysts
Several industrial chemical processes depend on molybdenum-based catalysts to proceed. One particularly important example is the hydrodesulfurizaton of petroleum. In this process, a molybdenum compound removes sulfur from unprocessed oil after it is removed from the Earth. According to the International Molybdenum Association, this use of the metal will become increasingly important in the future when sources of oil yield more Sulfur-rich raw materials.
[edit] Lubricant
The form in which natural molybdenum occurs most frequently, molybdenum disfulfide, is a valuable industrial lubricant. When compressed, molecules of molybdenum disulfide slide easily over and past one another. When inserted into the gears or among the bearings of a machine, molybdenum disulfide reduces the friction between two adjacent moving parts. Because of its origin in the hot depths of the earth, this lubricate resists breakdown by heat very well.
[edit] Pigments
When mixed with various combinations of lead, chromium and sulfur, molybdenum can form pigment chemicals that range from red-yellow to bright red-orange. These pigments are frequently used in Plastics, rubber products, ceramics, inks and Paints. Particularly valuable are the pigment's abilities to resist temperature changes and corrosion.
[edit] Corrosion Inhibitors
Steels treated with special formulations of molybdenum can resist corrosion. This is particularly important in devices whose steel components are exposed to large amounts of moisture, such as air conditioners, car engines and the hydraulic components of machines. Lubricants, cooling fluids and antifreezes often contain molybdenum compounds to help the devices resist corrosion.
[edit] Smoke Suppressants
When burned, the insulation around wires and cable can yield smoke that is toxic to people. Firefighters are particularly vulnerable to the toxins in this type of smoke. Adding an Aluminum-molybdenum compound to the insulation reduces the amount of toxic smoke that forms when the material is burned.
