Description
⌕ Enlarge Image
Terbium is a lanthanide that has a bright silvery white appearance in its natural solid state. It is soft enough to be cut with a knife, and it is stable in air. Terbium has an atomic weight of 158.92535, a melting point of 2473 °F, and a boiling point of 5846 °F. Some common uses of terbium include: as a component in alloys used for electrical devices, as a doper for calcium compounds, as a stabilizer in some fuel cells, and for coloring in fluorescent lamps and T.V. tubes.
Isolation
Terbium is never found in its free state in nature, rather it occurs with many other minerals and some clays. Isolation processes can be used to extract terbium from these sources.
⌕ Enlarge Image
Terbium occurs in other minerals that also contain lanthanides and rare earth elements such as cerite, gadolinite, monazite, euxenite, and bastnaesite. Extraction methods that are used to process bastnaesite from the other lanthanides that it contains are one of the largest sources of pure terbium. The complexity of the extraction and isolation process that is a result of the similar chemical characteristics between the lanthanides that occur together makes small scale isolation of terbium impossible. In addition to bastnaesite extraction, terbium can also be isolated from clays that it occurs in from ion adsorption techniques.
The bastnaesite isolation process begins with treating the mineral with sulfuric acid, hydrochloric acid, and sodium hydroxide. This process extracts the lanthanides from the mineral in their salt forms. Terbium is further isolated through repeated solvent extractions and ion exchange chromatography. The final isolation process involves reacting terbium fluoride with calcium under heated conditions. Vacuum processes remove any calcium contaminants that remain to form pure terbium.