Editing Aluminium (section)

== Production and refinement ==

{{See also|List of countries by primary aluminium production}}

<div style="float: right; margin: 2px; font-size:85%; margin-left:18px; margin-bottom:18px>
{| class="wikitable sortable collapsible"
|+'''World's largest producing countries of aluminium, 2024'''<ref name="usgs"/>
! Country !! data-sort-type="number"|Output<br />(thousand<br /> tons)
|-
| {{flagu|China}} || align="right"|43,000
|-
| {{flagu|India}} || align="right"|4,200
|-
| {{flagu|Russia}} || align="right"|3,800
|-
| {{flagu|Canada}} || align="right"|3,300
|-
| {{flagu|United Arab Emirates}} || align="right"|2,700
|-
| {{flagu|Bahrain}} || align="right"|1,600
|-
| {{flagu|Australia}} || align="right"|1,500
|-
| {{flagu|Norway}} || align="right"|1,300
|-
| {{flagu|Brazil}} || align="right"|1,100
|-
| {{flagu|Malaysia}} || align="right"|870
|-
| {{flagu|Iceland}} || align="right"|780
|-
| {{flagu|United States}} || align="right"|670
|-
| Other countries || align="right"|6,800
|-
| Total || align="right"|72,000
|}
</div>

The production of aluminium starts with the extraction of [[bauxite]] rock from the ground. The bauxite is processed and transformed using the [[Bayer process]] into [[alumina]], which is then processed using the [[Hall–Héroult process]], resulting in the final aluminium.

Aluminium production is highly energy-consuming, and so the producers tend to locate smelters in places where electric power is both plentiful and inexpensive.<ref name="WMP">{{cite book|url=http://www.bgs.ac.uk/downloads/start.cfm?id=1388|title=World Mineral Production 2003–2007|last1=Brown|first1=T.J.|date=2009|publisher=[[British Geological Survey]]|access-date=1 December 2014|archive-date=13 July 2019|archive-url=https://web.archive.org/web/20190713005219/http://www.bgs.ac.uk/downloads/start.cfm%3Fid%3D1388|url-status=live}}</ref> Production of one&nbsp;kilogram of aluminium requires 7&nbsp;kilograms of oil energy equivalent, as compared to 1.5&nbsp;kilograms for steel and 2&nbsp;kilograms for plastic.<ref>{{Cite book |last=Lama |first=F. |title=Why the West Can't Win: From Bretton Woods to a Multipolar World |publisher=Clarity Press, Inc. |year=2023 |isbn=978-1-949762-74-7 |pages=19}}</ref> As of 2024, the world's largest producers of aluminium were China, [[Russia]], India, Canada, and the [[United Arab Emirates]],<ref name="usgs">{{Cite journal |date=2025 |title=USGS Minerals Information: Mineral Commodity Summaries |url=https://pubs.usgs.gov/periodicals/mcs2025/mcs2025.pdf |language=en |doi=10.3133/mcs2025 |archive-url= |archive-date= |access-date=2 April 2025 |website=minerals.usgs.gov |author1=National Minerals Information Center }}</ref> while China is by far the top producer of aluminium with a world share of over 55%.

According to the [[International Resource Panel]]'s [[Metal Stocks in Society report]], the global [[per capita]] stock of aluminium in use in society (i.e. in cars, buildings, electronics, etc.) is {{convert|80|kg|abbr=on}}. Much of this is in more-developed countries ({{convert|350|–|500|kg|abbr=on}} per capita) rather than less-developed countries ({{convert|35|kg|abbr=on}} per capita).<ref>{{cite report
|last1=Graedel|first1=T.E.|title=Metal stocks in Society&nbsp;– Scientific Synthesis|year=2010
|url=http://www.unep.fr/shared/publications/pdf/DTIx1264xPA-Metal%20stocks%20in%20society.pdf
|isbn=978-92-807-3082-1|publisher=International Resource Panel|page=17|display-authors=etal<!--only mentions the lead author; others are not named-->|access-date=18 April 2017|archive-date=26 April 2018|archive-url=https://web.archive.org/web/20180426184751/http://www.unep.fr/shared/publications/pdf/DTIx1264xPA-Metal%20stocks%20in%20society.pdf|url-status=live}}</ref>

=== Bayer process ===

{{Main|Bayer process}}
{{See also|List of countries by bauxite production}}

[[Bauxite]] is converted to alumina by the Bayer process. Bauxite is blended for uniform composition and then is ground fine. The resulting [[slurry]] is mixed with a hot solution of [[sodium hydroxide]]; the mixture is then treated in a digester vessel at a pressure well above atmospheric, dissolving the aluminium hydroxide in bauxite while converting impurities into relatively insoluble compounds:<ref name="UllmannOxide" />

{{block indent|Al(OH)<sub>3</sub> + Na<sup>+</sup> + OH<sup>−</sup> → Na<sup>+</sup> + [Al(OH)<sub>4</sub>]<sup>−</sup>}}

After this reaction, the slurry is at a temperature above its atmospheric boiling point. It is cooled by removing steam as pressure is reduced. The bauxite residue is separated from the solution and discarded. The solution, free of solids, is seeded with small crystals of aluminium hydroxide; this causes decomposition of the [Al(OH)<sub>4</sub>]<sup>−</sup> ions to aluminium hydroxide. After about half of aluminium has precipitated, the mixture is sent to classifiers. Small crystals of aluminium hydroxide are collected to serve as seeding agents; coarse particles are converted to alumina by heating; the excess solution is removed by evaporation, (if needed) purified, and recycled.<ref name="UllmannOxide">{{Ullmann
|last1=Hudson|first1=L. Keith|last2=Misra|first2=Chanakya|last3=Perrotta|first3=Anthony J.|last4=Wefers|first4=Karl|last5=Williams|first5=F.S.|date=2005
|publisher=Wiley-VCH|title=Aluminum Oxide|display-authors=3|doi=10.1002/14356007.a01_557}}</ref>

=== Hall–Héroult process ===

[[File:Tovarna glinice in aluminija Kidričevo - kupi aluminija 1968.jpg|thumb|upright=0.75|right|[[Extrusion]] billets of aluminium]]

{{Main|Hall–Héroult process|Aluminium smelting}}
{{See also|List of countries by aluminium oxide production}}

The conversion of [[alumina]] to aluminium is achieved by the [[Hall–Héroult process]]. In this energy-intensive process, a solution of alumina in a molten ({{convert|940|and|970|C|F}}) mixture of [[cryolite]] (Na<sub>3</sub>AlF<sub>6</sub>) with [[calcium fluoride]] is [[electrolysis|electrolyzed]] to produce metallic aluminium. The liquid aluminium sinks to the bottom of the solution and is tapped off, and usually cast into large blocks called [[Bar stock|aluminium billets]] for further processing.<ref name="Ullmann" />

Anodes of the electrolysis cell are made of carbon—the most resistant material against fluoride corrosion—and either bake at the process or are prebaked. The former, also called Söderberg anodes, are less power-efficient and fumes released during baking are costly to collect, which is why they are being replaced by prebaked anodes even though they save the power, energy, and labor to prebake the cathodes. Carbon for anodes should be preferably pure so that neither aluminium nor the electrolyte is contaminated with ash. Despite carbon's resistivity against corrosion, it is still consumed at a rate of 0.4–0.5&nbsp;kg per each kilogram of produced aluminium. Cathodes are made of [[anthracite]]; high purity for them is not required because impurities [[Leaching (chemistry)|leach]] only very slowly. The cathode is consumed at a rate of 0.02–0.04&nbsp;kg per each kilogram of produced aluminium. A cell is usually terminated after 2–6 years following a failure of the cathode.<ref name="Ullmann" />

The Hall–Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the [[Hoopes process]]. This process involves the electrolysis of molten aluminium with a sodium, barium, and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%.<ref name="Ullmann" /><ref>{{cite book
|url=https://books.google.com/books?id=KpgTrFloOq0C&pg=PA40|title=Handbook of Aluminum|last1=Totten|first1=G.E.|last2=Mackenzie|first2=D.S.|date=2003
|publisher=[[Marcel Dekker]]|isbn=978-0-8247-4843-2|page=40
|archive-url=https://web.archive.org/web/20160615132126/https://books.google.com/books?id=KpgTrFloOq0C&pg=PA40|archive-date=15 June 2016|url-status=live}}</ref>

Electric power represents about 20 to 40% of the cost of producing aluminium, depending on the location of the smelter. Aluminium production consumes roughly 5% of electricity generated in the United States.<ref name="Emsley2011" /> Because of this, alternatives to the Hall–Héroult process have been researched, but none has turned out to be economically feasible.<ref name="Ullmann" />

===Recycling===

[[File:Waste bins recyclable.jpg|thumb|Common bins for recyclable waste along with a bin for unrecyclable waste. The bin with a yellow top is labeled "aluminum"<!--PLEASE DON'T CHANGE THE SPELLING HERE. IF YOU INSPECT THE PICTURE, YOU'LL SEE THE BIN SAYS "ALUMINUM" (ALONG WITH THE GREEK EQUIVALENT)-->. Rhodes, Greece.]]

{{Main|Aluminium recycling}}

Recovery of the metal through [[recycling]] has become an important task of the aluminium industry. Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium [[beverage can]]s brought it to public awareness.<ref>{{cite book|url=https://books.google.com/books?id=DtX1nbel49kC|title=Aluminum Recycling|last=Schlesinger|first=Mark|publisher=CRC Press|year=2006|isbn=978-0-8493-9662-5|page=248|access-date=25 June 2018|archive-date=15 February 2017|archive-url=https://web.archive.org/web/20170215051211/https://books.google.com/books?id=DtX1nbel49kC|url-status=live}}</ref> Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore, though a significant part (up to 15% of the input material) is lost as [[dross]] (ash-like oxide).<ref>{{cite web|url=http://www.dnr.state.oh.us/recycling/awareness/facts/benefits.htm|title=Benefits of Recycling|publisher=[[Ohio Department of Natural Resources]]|archive-url=https://web.archive.org/web/20030624162738/http://www.dnr.state.oh.us/recycling/awareness/facts/benefits.htm|archive-date=24 June 2003|url-status=dead}}</ref> An aluminium stack melter produces significantly less dross, with values reported below 1%.<ref>{{cite web|url=http://www.afsinc.org/files/best%20practice%20energy-schifo-radia-may%202004.pdf|title=Theoretical/Best Practice Energy Use in Metalcasting Operations|archive-url=https://web.archive.org/web/20131031072356/http://www.afsinc.org/files/best%20practice%20energy-schifo-radia-may%202004.pdf|archive-date=31 October 2013|url-status=dead|access-date=28 October 2013}}</ref>

White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium that can be [[Aluminium dross recycling|extracted industrially]]. The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manage. It reacts with water, releasing a mixture of gases including, among others, [[acetylene]],<ref>{{Cite journal |last1=Manfredi |first1=O. |last2=Wuth |first2=W. |last3=Bohlinger |first3=I. |date=November 1997 |title=Characterizing the physical and chemical properties of aluminum dross |url=https://link.springer.com/10.1007/s11837-997-0012-9 |journal=JOM |language=en |volume=49 |issue=11 |page=51 |doi=10.1007/s11837-997-0012-9 |bibcode=1997JOM....49k..48M |issn=1047-4838}}</ref> [[hydrogen sulfide]] and significant amounts of [[ammonia]].<ref name = drossgas>{{Cite journal |last1=Mahinroosta |first1=Mostafa |last2=Allahverdi |first2=Ali |date=October 2018 |title=Hazardous aluminum dross characterization and recycling strategies: A critical review |url=https://linkinghub.elsevier.com/retrieve/pii/S0301479718307205 |journal=Journal of Environmental Management |language=en |volume=223 |pages=457–458 |doi=10.1016/j.jenvman.2018.06.068|pmid=29957419 |bibcode=2018JEnvM.223..452M }}</ref> Despite these difficulties, the waste is used as a filler in [[Asphalt concrete|asphalt]] and [[concrete]].<ref>{{cite web|url=http://aggregain.wrap.org.uk/document.rm?id=1753|archive-url=http://webarchive.nationalarchives.gov.uk/20100402111522/http://www.wrap.org.uk/downloads/BRE_Added_value_study_report.4ca28919.1753.pdf|url-status=dead|archive-date=2 April 2010|title=Added value of using new industrial waste streams as secondary aggregates in both concrete and asphalt|last1=Dunster|first1=A.M.|date=2005|publisher=[[Waste & Resources Action Programme]]|display-authors=etal}}</ref> Its potential for hydrogen production has also been considered and researched.<ref>{{Cite journal |last1=David |first1=E. |last2=Kopac |first2=J. |date=March 2012 |title=Hydrolysis of aluminum dross material to achieve zero hazardous waste |url=https://linkinghub.elsevier.com/retrieve/pii/S0304389412000957 |journal=Journal of Hazardous Materials |language=en |volume=209-210 |pages=501–509 |doi=10.1016/j.jhazmat.2012.01.064|pmid=22326245 |bibcode=2012JHzM..209..501D }}</ref><ref>{{Cite journal |last1=Meshram |first1=Arunabh |last2=Jain |first2=Anant |last3=Rao |first3=Mudila Dhanunjaya |last4=Singh |first4=Kamalesh Kumar |date=July 2019 |title=From industrial waste to valuable products: preparation of hydrogen gas and alumina from aluminium dross |url=http://link.springer.com/10.1007/s10163-019-00856-y |journal=Journal of Material Cycles and Waste Management |language=en |volume=21 |issue=4 |pages=984–993 |doi=10.1007/s10163-019-00856-y |bibcode=2019JMCWM..21..984M |issn=1438-4957}}</ref>

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