Editing Selenium (section)

==Production==
Selenium is most commonly produced from [[selenide]] in many [[sulfide]] [[ore]]s, such as those of [[copper]], [[nickel]], or [[lead]]. Electrolytic metal refining is particularly productive of selenium as a byproduct, obtained from the [[anode]] mud of copper refineries. Another source was the mud from the [[Lead chamber process|lead chambers]] of [[sulfuric acid]] plants, a process that is no longer used. Selenium can be refined from these muds by a number of methods. However, most elemental selenium comes as a byproduct of [[Refining (metallurgy)|refining]] copper or producing [[sulfuric acid]].<ref>{{cite web |url=http://www.atsdr.cdc.gov/toxprofiles/tp92-c5.pdf |publisher=Agency for Toxic Substances and Disease Registry |title=Public Health Statement: Selenium – Production, Import/Export, Use, and Disposal |access-date=2009-01-05 |df=dmy-all}}</ref><ref>{{cite web |url=http://www.webelements.com/webelements/elements/text/Se/key.html |title=Chemistry: Periodic Table: selenium: key information |access-date= 2009-01-06 |publisher= webelements}}</ref> Since its invention, [[solvent extraction and electrowinning]] (SX/EW) production of copper produces an increasing share of the worldwide copper supply.<ref>{{cite journal |doi=10.1016/S0301-4207(03)00025-4 |title=SX-EW copper and the technology cycle |year=2002 |last1=Bartos |first1=P.J. |journal=Resources Policy |volume=28 |issue=3–4 |pages=85–94|bibcode=2002RePol..28...85B }}</ref> This changes the availability of selenium because only a comparably small part of the selenium in the ore is leached with the copper.<ref name="Naumov">{{cite journal |last1=Naumov |first1=A. V. |date=2010 |title=Selenium and tellurium: State of the markets, the crisis, and its consequences |journal=Metallurgist |volume=54 |issue=3–4 |pages=197–200 |doi=10.1007/s11015-010-9280-7 |s2cid=137066827}}</ref>

Industrial production of selenium usually involves the extraction of [[selenium dioxide]] from residues obtained during the purification of copper. Common production from the residue then begins by oxidation with [[sodium carbonate]] to produce selenium dioxide, which is mixed with water and [[acid]]ified to form [[selenous acid]] ([[oxidation]] step). Selenous acid is bubbled with [[sulfur dioxide]] ([[Redox|reduction]] step) to give elemental selenium.<ref>{{cite journal |doi=10.1007/BF03220269 |title=Recovering selenium and tellurium from copper refinery slimes |year=1989 |last1=Hoffmann |first1=James E. |journal=JOM |volume=41 |issue=7 |pages=33–38 |bibcode=1989JOM....41g..33H|s2cid=138253358 }}</ref><ref>{{cite journal |doi=10.1007/BF03220271|title= Recovering selenium from copper refinery slimes |date=1989 |last1=Hyvärinen |first1=Olli |last2=Lindroos |first2=Leo |last3=Yllö |first3=Erkki |journal=JOM |volume=41 |issue=7 |pages=42–43 |bibcode=1989JOM....41g..42H|s2cid= 138555797 }}</ref><!-- http://eprints.nmlindia.org/2071/-->

About 2,000&nbsp;tonnes of selenium were produced in 2011 worldwide, mostly in Germany (650&nbsp;t), Japan (630&nbsp;t), Belgium (200&nbsp;t), and Russia (140&nbsp;t), and the total reserves were estimated at 93,000&nbsp;tonnes. These data exclude two major producers: the United States and China. A previous sharp increase was observed in 2004 from $4–$5 to $27/lb. The price was relatively stable during 2004–2010 at about US$30&nbsp;per pound (in 100&nbsp;pound lots) but increased to $65/lb in 2011. The consumption in 2010 was divided as follows: metallurgy – 30%, glass manufacturing – 30%, agriculture – 10%, chemicals and pigments – 10%, and electronics – 10%. China is the dominant consumer of selenium at 1,500–2,000&nbsp;tonnes/year.<ref name="usgs" />