Description
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Molybdenum is a transition metal that has a grey metallic color in its natural solid state. This element has an extremely high melting point and the lowest heating expansion out of all the metals that are used commercially. Molybdenum has an atomic weight of 95.94, a melting point of 4753 °F, and a boiling point of 8382 °F. Some common uses of molybdenum include: as a component in alloys for its strengthening characteristics, as a trace element for plant nutrition, as a component in electrodes for glass furnaces that are heated through electricity, and as a catalyst in petroleum refining.
Isolation
Molybdenum is isolated from minerals that it occurs in for commercial purposes. It is also obtained as a byproduct of tungsten and copper mining.
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Molybdenum occurs in minerals such as wulfenite, powellite, and molybdenite. Molybdenite is the ore that is used most frequently for commercial isolation purposes. Molybdenite is a mineral which is composed of molybdenum disulfide. In order to extract molybdenum from its disulfide form, it is converted to its single sulfide form. The next isolation step involves “roasting” the sulfide to form the molybdenum oxide. The molybdenum oxide is usually then used for steel alloys.
Further isolation of the molybdenum oxide uses ammonium hydroxide and hydrogen. The molybdenum oxide is first dissolved in ammonium hydroxide to create ammonium molybdate. The ammonium molybdate is then reacted with hydrogen in a reduction reaction. The end result is pure molybdenum metal. Isolation of molybdenum is not normally carried out in a laboratory setting as the pure form is available for commercial uses; isolated molybdenum in large quantities can be toxic to some animals and needs to be handled with caution.