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.
