Extractive Metallurgy of Vanadium

Vanadium never is present as native metal, but there more than 50 types of vanadium minerals on the earth being the main specimens: patronite, vanadinite, and carnotite, this element is also present in bauxite, and in carbon containing deposits such as crude oil, coal, and some types of bituminous material. There is not a unique mineral from which vanadium is recovered and extracted. Nevertheless, it is many times found as a trace element in a several number of different materials and is a by-product of other mining operations. Vanadium can be found in magnetite deposits that are also very rich in the element titanium. It is also found in bauxite (aluminium mineral), rocks with high concentrations of phosphorous-containing minerals, and some stones.

In general, if there are oxidized minerals with high grade, is possible sent then directly to the smelters that employ a roasting process with sodium chloride, the same case can be applied when there is a sulphide ore with high content of Vanadium. However, when there is low grade ores is necessary a previous roasting process. A process well known for a long time is the called Roast Quench Leach Process which involves pyrometallurgical and hydrometallurgical operations. The roasting gives vanadium pentoxide which can be treated by two routes: alkaline-acid and acid. The latter is the most common process and employs an acid solution of sulfuric acid. The final product ideally must have 56% vanadium, but this is not possible because the contaminants play an important influence in the quality of the product.

Commercially, routes that lead to metallic vanadium as main product are not usually required as enough is produced as byproduct in other processes. Vanadates are easily dissolved by alkaline fusion. In acid environment and after several steps is obtained vanadium pentoxide (V2O5) which is reduce partially with carbon and later with calcium under inert atmosphere in order to get metallic vanadium. If the ore to be treated does not have a vanadate else a Sulphide, this is oxidized to vanadate and the process is repeated as in the first case. But, if it is required vanadium of high quality of purity, the Van Arkel de Boer process has to be used. This process forms a volatile compound which is decomposed in the last step of the process.

To industrial level, heating of vanadium ore or other source from other processes with sodium chloride or sodium carbonate at approximately 900°C gives sodium vanadate which is dissolved in water and later acidified in order to get a red solid that will be melted to form vanadium pentoxide. As was said, reaction of vanadium pentoxide with calcium gives metallic vanadium. An alternative process to be used in small scale is the reaction of vanadium pentachloride with hydrogen or magnesium.

The main use of vanadium is to produce ferrovanadium, and also can be used as additive in the manufacturing of several types of steel. Other uses of vanadium are surgical instruments, tools, steels with resistance to corrosion, reaction motors. Also is used in nuclear reactors and magnets. Perhaps one of the most common uses is in the production of sulfuric acid because vanadium pentoxide acts as a catalyzer and let the transformation of SO2 to SO3.