Molybdenum (Mo), a transition metal with atomic number 42, is found throughout our environment. It is an important trace element for life on Earth, playing a role in various natural processes and industrial applications.
Molybdenum in the Earth
Molybdenum is naturally present in the Earth’s crust, typically ranking as the 54th most abundant element with an average concentration of 1.5 parts per million. It does not occur as a pure metal in nature; instead, it is found combined with other elements in minerals. The primary ore from which molybdenum is extracted is molybdenite (MoS2), though it is also found in minerals like wulfenite (PbMoO4) and powellite (CaMoO4).
Molybdenum can leach from rocks and minerals into soils and water sources. This process is influenced by its ability to oxidize into a water-soluble form, molybdate (MoO4-). Consequently, its concentration in soil and water varies depending on the local geology.
Molybdenum in Industry
After extraction, molybdenum is processed and utilized in numerous industrial applications. Approximately 80% of global molybdenum production is used in the steel industry. Adding molybdenum to steel enhances its strength, hardness, and resistance to corrosion, making it valuable for high-strength alloys, stainless steel, tool steel, and components for automotive and aerospace industries.
Molybdenum compounds serve as catalysts, notably in petroleum refining for hydrodesulfurization, which removes sulfur from fuels. It is also used in pigments for paints and inks; non-toxic molybdenum yellow and orange pigments offer environmentally friendly alternatives to those containing lead or chromium. Molybdenum disulfide (MoS2) functions as a solid lubricant, effective under high temperature and pressure, finding use in engines and aerospace applications.
Molybdenum in Living Organisms
Molybdenum is an essential trace element required by plants, animals, and humans for various biological processes. It functions primarily as a cofactor for several enzymes, helping these proteins perform specific biochemical reactions.
In plants and bacteria, molybdenum is a component of nitrogenase, an enzyme crucial for nitrogen fixation, the process that converts atmospheric nitrogen into ammonia. In humans, molybdenum is necessary for enzymes such as xanthine oxidase, which plays a role in purine metabolism and uric acid formation. Another enzyme, sulfite oxidase, relies on molybdenum to detoxify sulfites, converting them into a less harmful sulfate form.
Humans obtain molybdenum through their diet, with rich sources including legumes, whole grains, nuts, leafy green vegetables, dairy products, and organ meats. Small amounts of molybdenum are stored in human and animal tissues, particularly in the liver and kidneys.