Editing Terbium (section)

== Production ==
Crushed terbium-containing minerals are treated with hot concentrated [[sulfuric acid]] to produce water-soluble sulfates of rare earths. The acidic filtrates are partially neutralized with caustic soda to pH 3–4. [[Thorium]] precipitates out of solution as hydroxide and is removed. The solution is treated with [[ammonium oxalate]] to convert rare earths into their insoluble [[oxalate]]s. The oxalates are decomposed to oxides by heating. The oxides are dissolved in [[nitric acid]] that excludes one of the main components, cerium, whose oxide is insoluble in {{chem2|HNO3}}. Terbium is separated as a [[double salt]] with [[ammonium nitrate]] by crystallization.<ref name="patnaik" />

The most efficient separation routine for terbium salt from the rare-earth salt solution is [[ion exchange]]. In this process, rare-earth ions are [[adsorption|sorbed]] onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin. The rare earth ions are then selectively washed out by suitable [[Complexing agent|complexing agents]]. As with other rare earths, terbium metal is produced by reducing the anhydrous chloride or fluoride with calcium metal. Calcium and [[tantalum]] impurities can be removed by vacuum remelting, distillation, amalgam formation or [[zone melting]].<ref name="patnaik" /><ref name="history" />

In 2020, the annual demand for terbium was estimated at {{Convert|340|t|lb}}.<ref name=":2">{{Cite journal |last1=Gao |first1=Cuixia |last2=Xu |first2=Yufei |last3=Geng |first3=Yong |last4=Xiao |first4=Shijiang |date=2022-12-01 |title=Uncovering terbium metabolism in China: A dynamic material flow analysis |url=https://linkinghub.elsevier.com/retrieve/pii/S0301420722004603 |journal=Resources Policy |volume=79 |pages=103017 |doi=10.1016/j.resourpol.2022.103017 |bibcode=2022RePol..7903017G |issn=0301-4207}}</ref> Terbium is not distinguished from other rare earths in the [[United States Geological Survey]]'s Mineral Commodity Summaries, which in 2024 estimated the global reserves of rare earth minerals at {{Convert|110000000|t|lb}}.<ref>{{Cite journal |date=January 2024 |title=Rare Earths |url=https://pubs.usgs.gov/periodicals/mcs2024/mcs2024-rare-earths.pdf |journal=Mineral Commodity Summaries |pages=144–145 |via=U. S. Geological Survey}}</ref>