What are the Sources of Vanadium?

Vanadium is the 20th most abundant element in the Earth's crust; metallic vanadium is rare in nature. At the start of the 20th century, a large deposit of vanadium ore was discovered. For several years this patro´nite (VS4) deposit was an economically important source for vanadium ore. With the production of radium in the 1910s and 1920s from carnotite (K2(UO2)2(VO4)2·3H2O) in which it is present in trace amounts, vanadium became available as a by-product of radium and uranium production. Vanadinite (Pb5(VO4)3Cl) and other vanadium containing minerals are only mined in exceptional cases.

With the increasing demand, now most of the world's vanadium metal is coming from vanadium-bearing magnetite found in ultramafic gabbro bodies. When this titanomagnetite is utilized to produce iron, most of the vanadium ends in the slag and is extracted from there. Vanadium is mined mostly in South Africa, north-western China, and eastern Russia. In addition, vanadium is present in bauxite and in deposits of crude oil, coal, oil shale, and tar sands. In crude oil, concentrations up to 1200 ppm have been recorded.

Vanadium metal is produced via a multistep process that starts with the roasting of crushed ore with NaCl or Na2CO3 at ~850℃ to produce sodium metavanadate (NaVO3). An aqueous extract of this solid is acidified to give “red cake,” a polyvanadate salt, which is reduced with calcium metal. As an alternative for small-scale production, vanadium pentoxide is reduced with hydrogen or magnesium. Numerous other processes are also being used, in all of which vanadium is separated as a by-product of other processes. Purification of vanadium is possible utilizing the crystal bar process developed by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925, which comprises the formation of the metal iodide, here vanadium(III) iodide, followed by decomposition to obtain the pure metal.

2V+3I₂⇌2VI₃

Most vanadium is utilized in a steel alloy called ferrovanadium. Ferrovanadium is manufactured directly by reducing a combination of vanadium oxide, iron oxides, and iron in an electric furnace. The vanadium ends up in pig iron obtained from vanadium-bearing magnetite. Depending on the ore used, the slag can have up to 25% vanadium.