Editing Magnesium (section)

== Production ==
{{See also|Magnesium production by country}}
[[File:Mg sheets and ingots.jpg|thumb|Magnesium sheets and ingots]]

=== Occurrence ===
{{Category see also|Magnesium minerals}}
{{See also|Boninite}}
Magnesium is the eighth-most-abundant element in the Earth's crust by mass and tied in seventh place with [[iron]] in [[molarity]].<ref name="Abundance">{{cite web|title=Abundance and form of the most abundant elements in Earth's continental crust|access-date=15 February 2008|url=http://www.gly.uga.edu/railsback/Fundamentals/ElementalAbundanceTableP.pdf|last=Railsback|first=L. Bruce|website=Some Fundamentals of Mineralogy and Geochemistry|archive-date=27 September 2011|archive-url=https://web.archive.org/web/20110927064201/http://www.gly.uga.edu/railsback/Fundamentals/ElementalAbundanceTableP.pdf|url-status=dead}}</ref> It is found in large deposits of [[magnesite]], [[Dolomite (mineral)|dolomite]], and other [[mineral]]s, and in mineral waters, where magnesium ion is soluble.<ref>{{Cite web |date=2013-04-30 |title=Magnesium EA65RS-T4 Alloy |url=https://www.azom.com/article.aspx?ArticleID=8683 |access-date=2024-05-04 |website=AZoM |language=en}}</ref>

Although magnesium is found in more than 60 [[mineral]]s, only [[Dolomite (mineral)|dolomite]], [[magnesite]], [[brucite]], [[carnallite]], [[talc]], and [[olivine]] are of commercial importance.<ref>{{Cite web |title=Magnesium Statistics and Information {{!}} U.S. Geological Survey |url=https://www.usgs.gov/centers/national-minerals-information-center/magnesium-statistics-and-information |access-date=2024-05-04 |website=www.usgs.gov}}</ref>

The {{chem|Mg|2+}} [[cation]] is the second-most-abundant cation in seawater (about {{frac|1|8}} the mass of sodium ions in a given sample), which makes seawater and sea salt attractive commercial sources for Mg.

===Production quantities===
World production was approximately 1,100 kt in 2017, with the bulk being produced in China (930 kt) and Russia (60 kt).<ref>Bray, E. Lee (February 2019) [https://minerals.usgs.gov/minerals/pubs/commodity/magnesium/mcs-2019-mgmet.pdf Magnesium Metal]. Mineral Commodity Summaries, U.S. Geological Survey</ref> The United States was in the 20th century the major world supplier of this metal, supplying 45% of world production even as recently as 1995. Since the Chinese mastery of the Pidgeon process the US market share is at 7%, with a single US producer left as of 2013: US Magnesium, a [[Renco Group]] company located on the shores of the [[Great Salt Lake#Oil and minerals|Great Salt Lake]].<ref name="vardi">{{Cite web|last=Vardi|first=Nathan|title=Man With Many Enemies |url=https://www.forbes.com/forbes/2002/0722/044.html |date=6 June 2013 |website=Forbes|language=en}}</ref>

In September 2021, China took steps to reduce production of magnesium as a result of a government initiative to reduce energy availability for manufacturing industries, leading to a significant price increase.<ref>{{cite magazine |url=https://www.cips.org/supply-management/analysis/2022/february/what-to-do-about-the-magnesium-shortage/ |title=What to do about the magnesium shortage |magazine=Supply Management|date=17 February 2022 |archive-url=https://web.archive.org/web/20220217211243/https://www.cips.org/supply-management/analysis/2022/february/what-to-do-about-the-magnesium-shortage/ |archive-date=17 February 2022}}</ref>

=== Pidgeon and Bolzano processes===
[[File:محتویات درون ریتورت.jpg|thumb|right|An Iranian worker tends to the Pidgeon process]]
The [[Pidgeon process]] and the [[Bolzano process]] are similar.  In both, magnesium oxide is the precursor to magnesium metal.  The magnesium oxide is produced as a solid solution with calcium oxide by calcining the mineral [[dolomite (mineral)|dolomite]], which is a solid solution of calcium and magnesium carbonates:
:{{chem2|CaCO3*MgCO3 -> MgO*CaO  + 2 CO2}}
Reduction occurs at high temperatures with silicon. A ferrosilicon alloy is used rather than pure silicon as it is more economical. The iron component has no bearing on the reaction, having the simplified equation:{{citation needed|date=July 2024}}
:{{chem2|MgO*CaO +Si -> 2 Mg  + Ca2SiO4}}
The calcium oxide combines with silicon as the oxygen scavenger, yielding the very stable calcium silicate.  The Mg/Ca ratio of the precursors can be adjusted by the addition of MgO or CaO.<ref>{{cite book |doi=10.1002/14356007.a15_559 |chapter=Magnesium |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2003|publisher=Wiley|location=Weinheim, Germany|display-authors=3 |last1=Amundsen |first1=Ketil |last2=Aune |first2=Terje Kr. |last3=Bakke |first3=Per |last4=Eklund |first4=Hans R. |last5=Haagensen |first5=Johanna Ö. |last6=Nicolas |first6=Carlos |last7=Rosenkilde |first7=Christian |last8=Van Den Bremt |first8=Sia |last9=Wallevik |first9=Oddmund |isbn=978-3-527-30385-4 }}</ref>

The Pidgeon and the Bolzano process differ in the details of the heating and the configuration of the reactor.  Both generate gaseous Mg that is condensed and collected. The Pidgeon process dominates the worldwide production.<ref name=":1" /><ref name=":2">{{Cite web |title=Magnesium Processing {{!}} Techniques & Methods {{!}} Britannica |url=https://www.britannica.com/technology/magnesium-processing |access-date=2023-04-16 |website=www.britannica.com |language=en}}</ref> The Pidgeon method is less technologically complex and because of distillation/vapour deposition conditions, a high purity product is easily achievable.<ref name=":1">{{Cite book |url=https://www.worldcat.org/oclc/1111577710 |title=Magnesium and its alloys : technology and applications |date=2020 |vauthors=Bamberger M, Dobrzański LA, Totten GE|isbn=978-1-351-04547-6 |edition=First |location=Boca Raton, FL|publisher=CRC Press, Inc. |oclc=1111577710}}</ref> China is almost completely reliant on the [[Silicothermic reaction|silicothermic]] [[Pidgeon process]].

=== Dow process ===
{{anchor|Dow process}}
{{Redirect|Dow process (magnesium)|other Dow processes|Dow process (disambiguation)}}
Besides the Pidgeon process, the second most used process for magnesium production is [[electrolysis]]. This is a two step process. The first step is to prepare feedstock containing magnesium chloride and the second step is to dissociate the compound in [[electrolytic cell]]s as magnesium metal and [[Chlorine|chlorine gas]].<ref name=":2" />

To extract the magnesium, [[calcium hydroxide]] is added to the [[seawater]] to  [[precipitate]] [[magnesium hydroxide]].<ref>{{cite journal |last1=Battaglia |first1=Giuseppe |last2=Domina |first2=Maria Alda |last3=Lo Brutto |first3=Rita |last4=Lopez Rodriguez |first4=Julio |last5=Fernandez de Labastida |first5=Marc |last6=Cortina |first6=Jose Luis |last7=Pettignano |first7=Alberto |last8=Cipollina |first8=Andrea |last9=Tamburini |first9=Alessandro |last10=Micale |first10=Giorgio |title=Evaluation of the Purity of Magnesium Hydroxide Recovered from Saltwork Bitterns |journal=Water |date=21 December 2022 |volume=15 |issue=1 |pages=29 |doi=10.3390/w15010029 |doi-access=free |bibcode=2022Water..15...29B |hdl=2117/384847 |hdl-access=free }}</ref>
: {{chem|MgCl|2}} + {{chem|Ca(OH)|2}} → {{chem|Mg(OH)|2}} + {{chem|CaCl|2}}

Magnesium hydroxide ([[brucite]]) is poorly soluble in water and can be collected by filtration.  It reacts with [[hydrochloric acid]] to [[magnesium chloride]].<ref>{{Cite web |title=Magnesium processing {{!}} Techniques & Methods {{!}} Britannica |url=https://www.britannica.com/technology/magnesium-processing |access-date=2024-05-04 |website=www.britannica.com |language=en}}</ref>
: {{chem|Mg(OH)|2}} + 2 HCl → {{chem|MgCl|2}} + 2 {{chem|H|2|O}}
From magnesium chloride, [[electrolysis]] produces magnesium.<ref>{{Cite web |title=Magnesium metal is produced by the electrolysis of molten magnesi... {{!}} Channels for Pearson+ |url=https://www.pearson.com/channels/general-chemistry/asset/95590f70/magnesium-metal-is-produced-by-the-electrolysis-of-molten-magnesium-chloride-usi |access-date=2024-05-04 |website=www.pearson.com |language=en}}</ref>

The basic reaction is as follows:
:{{chem2 | MgCl2 -> Mg(g) + Cl2(g) }}

The temperatures at which this reaction is operated is between 680 and 750&nbsp;°C.<ref name=":2" />

The magnesium chloride can be obtained using the [[Dow process (magnesium)|Dow process]], a process that mixes sea water and dolomite in a flocculator or by dehydration of magnesium chloride brines. The electrolytic cells are partially submerged in a molten salt electrolyte to which the produced magnesium chloride is added in concentrations between 6–18%.<ref name=":2" /> This process does have its share of disadvantages including production of harmful [[chlorine gas]] and the overall reaction being very energy intensive, creating environmental risks.<ref name=lee21>{{Cite journal |last1=Lee |first1=Tae-Hyuk |last2=Okabe |first2=Toru H. |last3=Lee |first3=Jin-Young |last4=Kim |first4=Young Min |last5=Kang |first5=Jungshin |date=September 2021 |title=Development of a novel electrolytic process for producing high-purity magnesium metal from magnesium oxide using a liquid tin cathode |journal=Journal of Magnesium and Alloys |language=en |volume=9 |issue=5 |pages=1644–1655 |doi=10.1016/j.jma.2021.01.004|s2cid=233930398 |doi-access=free }}</ref> The Pidgeon process is more advantageous regarding its simplicity, shorter construction period, low power consumption and overall good magnesium quality compared to the electrolysis method.<ref name=":0" />

In the United States, magnesium was once obtained principally with the Dow process in [[Corpus Christi TX]], by [[electrolysis]] of fused magnesium chloride from [[brine]] and [[sea water]]. A saline solution containing {{chem|Mg|2+}} ions is first treated with [[Calcium oxide|lime]] (calcium oxide) and the precipitated [[magnesium hydroxide]] is collected:
:{{chem|Mg|2+}}(aq) + {{chem|CaO}}(s) + {{chem|H|2|O}}(l) → {{chem|Ca|2+}}(aq) + {{chem|Mg(OH)|2}}(s)

The hydroxide is then converted to [[magnesium chloride]] by treatment with [[hydrochloric acid]] and heating of the product to eliminate water:
:{{chem2|Mg(OH)2 + 2 HCl → MgCl2  +  2 H2O}}

The salt is then electrolyzed in the molten state. At the [[cathode]], the {{chem|Mg|2+}} ion is reduced by two [[electron]]s to magnesium metal:
:{{chem|Mg|2+}} + 2{{Subatomic particle|electron}} → Mg

At the [[anode]], each pair of {{chem|Cl|-}} ions is oxidized to [[chlorine]] gas, releasing two electrons to complete the circuit:
:2{{chem|Cl|-}} → {{chem|Cl|2}}(g) + 2{{Subatomic particle|electron}}

===Carbothermic process===
The [[Carbothermic reaction|carbothermic]] route to magnesium has been recognized as a low energy, yet high productivity path to magnesium extraction. The chemistry is as follows:
[[File:Rotary kiln Johannsen patent US1618204.png|thumb|The rotary kiln is used for calcination]]
{{chem2|C + MgO -> CO + Mg}}

A disadvantage of this method is that slow cooling the vapour can cause the reaction to quickly revert. To prevent this from happening, the magnesium can be dissolved directly in a suitable metal solvent before reversion starts happening. Rapid [[quenching]] of the vapour can also be performed to prevent reversion.<ref>{{Cite journal |last1=Brooks |first1=Geoffrey |last2=Trang |first2=Simon |last3=Witt |first3=Peter |last4=Khan |first4=M. N. H. |last5=Nagle |first5=Michael |date=May 2006 |title=The carbothermic route to magnesium |url=http://dx.doi.org/10.1007/s11837-006-0024-x |journal=JOM |volume=58 |issue=5 |pages=51–55 |doi=10.1007/s11837-006-0024-x |bibcode=2006JOM....58e..51B |s2cid=67763716 |issn=1047-4838}}</ref>

=== YSZ process ===
{{anchor|YSZ process}}
A newer process, solid oxide membrane technology, involves the electrolytic reduction of MgO. At the cathode, {{chem|Mg|2+}} ion is reduced by two [[electron]]s to magnesium metal. The electrolyte is [[yttria-stabilized zirconia]] (YSZ). The anode is a liquid metal. At the YSZ/liquid metal anode {{chem|O|2-}} is oxidized. A layer of graphite borders the liquid metal anode, and at this interface carbon and oxygen react to form carbon monoxide. When silver is used as the liquid metal anode, there is no reductant carbon or hydrogen needed, and only oxygen gas is evolved at the anode.<ref name="pal07">{{cite journal|last1=Pal|first1=Uday B. |last2=Powell|first2=Adam C.|title=The Use of Solid-Oxide-Membrane Technology for Electrometallurgy|date=2007|bibcode=2007JOM....59e..44P|volume=59|pages=44–49|journal=JOM|doi=10.1007/s11837-007-0064-x|issue=5|s2cid=97971162 }}</ref> It was reported in 2011 that this method provides a 40% reduction in cost per pound over the electrolytic reduction method.<ref>{{cite web| url=http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2011/lightweight_materials/lm035_derezinski_2011_o.pdf| archive-url=https://web.archive.org/web/20131113035743/http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2011/lightweight_materials/lm035_derezinski_2011_o.pdf| url-status=dead| archive-date=13 November 2013|publisher=MOxST| title=Solid Oxide Membrane (SOM) Electrolysis of Magnesium: Scale-Up Research and Engineering for Light-Weight Vehicles |first=Steve| last=Derezinski |date=12 May 2011| access-date=27 May 2013}}</ref>

=== Rieke process ===
Rieke et al. developed a "general approach for preparing highly reactive metal powders by reducing metal salts in ethereal or hydrocarbon solvents using alkali metals as reducing agents" now known as the [[Rieke process]].<ref name="rieke16">{{cite book |doi=10.1002/9781118929124.ch4 |chapter=Magnesium |title=Chemical Synthesis Using Highly Reactive Metals |date=2017 |pages=161–208 |isbn=978-1-118-92911-7 }}</ref> Rieke finalized the identification of [[Rieke metals]] in 1989,<ref name="rieke95">{{cite book |doi=10.1002/9783527615179.ch01 |chapter=Rieke Metals: Highly Reactive Metal Powders Prepared by Alkali Metal Reduction of Metal Salts |title=Active Metals |date=1995 |last1=Rieke |first1=Reuben D. |last2=Sell |first2=Matthew S. |last3=Klein |first3=Walter R. |last4=Chen |first4=Tian-An |last5=Brown |first5=Jeffrey D. |last6=Hanson |first6=Mark V. |pages=1–59 |isbn=978-3-527-29207-3 }}</ref> one of which was Rieke-magnesium, first produced in 1974.<ref name="rieke74">{{cite journal |doi=10.1002/chin.197421315 |title=ChemInform Abstract: ACTIVATED METALS PART 4, PREPARATION AND REACTIONS OF HIGHLY REACTIVE MAGNESIUM METAL |date=1974 |last1=Rieke |first1=Reuben D. |last2=Bales |first2=Stephen E. |journal=Chemischer Informationsdienst |volume=5 |issue=21 }}</ref>