Calciothermic reaction

{{Short description|Metallothermic reduction reaction}}

Calciothermic reactions are metallothermic reduction reactions (more generally, thermic chemical reactions) which use calcium metal as the reducing agent at high temperature.

Calcium is one of the most potent reducing agents available, usually drawn as the strongest oxidic reductant in Ellingham diagrams, though the lanthanides best it in this respect in oxide processes.{{Cite journal |last=Kasimtsev |first=A. V. |last2=Yudin |first2=S. N. |last3=Levinsky |first3=Yu. V. |date=2020-12-29 |title=Calciothermic powders of rare metals and intermetallic compounds |url=http://dx.doi.org/10.17580/nfm.2020.02.05 |journal=Non-ferrous Metals |pages=31–50 |doi=10.17580/nfm.2020.02.05 |issn=2072-0807}} On the other hand, this trend does not continue to other compounds that are non-oxides, and for instance lanthanum is produced by the calciothermic reduction of the chloride, calcium being a more potent reducing agent than lanthanum involving chlorides.

Calciothermic processes are used in the extraction of metals such as uranium,{{Cite report |url=https://www.osti.gov/biblio/1159227 |title=Uranium Dioxide Conversion |last=Figueroa |first=Javier |last2=Williamson |first2=Mark A. |date=2014-09-25 |publisher=Argonne National Lab. (ANL), Argonne, IL (United States) |issue=ANL/CSE-13/25 |language=English}} zirconium,{{Cite journal |last=Abdelkader |first=Amr Mohamed |last2=El-Kashif |first2=Emad |date=2007 |title=Calciothermic Reduction of Zirconium Oxide in Molten CaCl2 |url=https://www.jstage.jst.go.jp/article/isijinternational/47/1/47_1_25/_article/-char/ja/ |journal=ISIJ International |volume=47 |issue=1 |pages=25–31 |doi=10.2355/isijinternational.47.25|doi-access=free }} and thorium{{Cite book |last=Vignes |first=Alain |date=2013-02-28 |title=Extractive Metallurgy 3 |url=http://dx.doi.org/10.1002/9781118617106 |doi=10.1002/9781118617106 |isbn=9781118617106 }} from oxide ores.

An interesting way of performing calciothermic reductions is by in-situ generated metallic calcium, dissolved in molten calcium chloride, as shown in the FFC Cambridge Process.