Editing Copper extraction (section)

==Concentration (beneficiation)==
{{Further|topic=copper ore body formation|Ore genesis#Copper}}
{{See also|List of copper ores}}
[[file:Evolution minerai cuivre.svg|thumb|lang=en|upright=1.35|The decreasing concentration of copper in ores now requires pre-treatment of ores.|link=File:Evolution_minerai_cuivre.svg]]

The average grade of copper ores in the 21st century is below 0.6% copper, with a proportion of economic ore minerals being less than 2% of the total volume of the ore rock. Thus, all mining operations, the [[ore]] must usually be [[beneficiation|beneficiated]] (concentrated). The concentrate is typically sold to distant [[Smelting|smelters]], although some large mines have smelters located nearby. Such colocation of mines and smelters was more typical in the 19th and early 20th centuries, when smaller smelters could be economic. The subsequent processing techniques depend on the nature of the ore.

In the usual case when it is primarily sulfide copper minerals (such as [[chalcopyrite]], FeCuS<sub>2</sub>), the ore is treated by ''[[comminution]]'', where the rock is crushed to produce small particles (<100 μm) consisting of individual mineral phases. These particles are then ready to be separated to remove [[gangue]] (silicate rocks residues) using froth flotation.<ref name=Ullm>{{cite book|doi=10.1002/14356007.a07_471|chapter=Copper |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2001 |last1=Lossin |first1=Adalbert |isbn=3-527-30673-0 }}</ref>

===Froth flotation===
{{main|Froth floatation}} 
[[File:FlotationFalconbridgeOnt.jpg|thumb|Froth flotation cells to concentrate copper and nickel sulfide minerals, Falconbridge, Ontario.]]
[[File:Prominenthill-flotation.jpg|thumb|Copper sulfide loaded air bubbles on a [[Jameson Cell]] at the flotation plant of the [[Prominent Hill]] mine in [[South Australia]]]]

In froth flotation, the crushed ore is wetted, suspended in a slurry, and mixed with reagents that render the sulfide particles [[hydrophobic]]. Typical reagents ("collectors") include [[potassium ethylxanthate]] and [[sodium ethylxanthate]], but [[dithiophosphate]]s and dithiocarbamates are also used. The slurry is introduced to a water-filled aeration tank containing a [[surfactant]] such as [[4-Methyl-2-pentanol|methylisobutyl carbinol]] (MIBC). Air is constantly forced through the slurry. The air bubbles attach to the hydrophobic copper sulfide particles, which are conveyed to the surface where the froth is skimmed off. These skimmings are generally subjected to a cleaner-scavenger cell to remove excess silicates and to remove other sulfide minerals that can deleteriously impact the concentrate quality (typically, [[galena]]), and the final concentrate is sent for smelting. The rock that has not floated off in the flotation cell is either discarded as [[tailings]] or further processed to extract other metals such as lead (from galena) and zinc (from [[sphalerite]]), should they exist. A variety of measures are taken to improve the efficiency of the froth flotation. [[Lime (material)|Lime]] is used to raise the [[pH]] of the water bath, causing the collector to bond more efficiently to the copper sulfides. The process can produce concentrates with 27–29% and 37–40% copper contents from [[chalcopyrite]] and [[chalcocite]], respectively.

===Hydrometallurgy===
[[File:Cu(Salox)2.png|thumb|left|upright=0.5|In some hydrometallurgical schemes, copper(II) is extracted from aqueous solution as by complexation to [[salicylaldoxime]].]]

Oxidised copper ores include carbonates such as [[azurite]] and [[malachite]], the silicate [[chrysocolla]], and sulfates such as [[atacamite]]. In some cases, sulfide ores are allowed to degrade to oxides. Such ores are amenable to hydrometallurgy. Specifically, such oxide ores are usually extracted into aqueous [[sulfuric acid]], usually in a [[heap leaching]] or [[dump leaching]]. The resulting pregnant leach solution is purified by solvent extraction (SX). It is treated with an organic solvent and an organic chelators. The chelators bind the copper ions (and no other ions, ideally), the resulting complexes dissolve in the organic phase. This organic solvent is evaporated, leaving a residue of the copper complexes. The copper ions are liberated from the residue with sulfuric acid. The barred (denuded) sulfuric acid recycled back on to the heaps. The organic ligands are recovered and recycled as well. Alternatively, the copper can be precipitated out of the pregnant solution by contacting it with scrap iron; a process called [[Cementation (metallurgy)|cementation]]. Cement copper is normally less pure than SX-EW copper.<ref>{{cite journal |title=Co-extraction of Cations and Anions in Base Metal Recovery |year=2007 |last1=Tasker |first1=Peter A. |last2=Tong |first2=Christine C. |last3=Westra |first3=Arjan N. |journal=Coordination Chemistry Reviews |volume=251 |issue=13–14 |pages=1868–1877 |doi=10.1016/j.ccr.2007.03.014}}</ref>

===Specialized ores===
[[File:Chalcocite-271692.jpg|thumb|A specimen of the mineral chalcocite from the Geevor Mine, Cornwall.]]
Secondary sulfides—those formed by [[Supergene (geology)|supergene]] secondary enrichment—are resistant (''[[refractory]]'') to sulfuric leaching.<ref>{{Cite journal |last=Petersen |first=Jochen |date=October 2016 |title=Heap leaching as a key technology for recovery of values from low-grade ores – A brief overview |journal=Hydrometallurgy |volume=165 |pages=206–212 |doi=10.1016/j.hydromet.2015.09.001|bibcode=2016HydMe.165..206P }}</ref> Secondary copper sulfides are dominated by the mineral chalcocite; a mineral formed from primary sulfides, like [[chalcopyrite]], that undergo chemical processes such as oxidation or reduction.<ref>{{Cite journal |last1=Wu |first1=Biao |last2=Yang |first2=Xinlong |last3=Wen |first3=Jiankang |last4=Wang |first4=Dianzuo |date=2019-11-05 |title=Semiconductor-Microbial Mechanism of Selective Dissolution of Chalcocite in Bioleaching |journal=ACS Omega |volume=4 |issue=19 |pages=18279–18288 |pmc=6844112 |pmid=31720528 |doi=10.1021/acsomega.9b02294 |doi-access=free |issn=2470-1343}}</ref> Typically, secondary sulfide ores are concentrated using froth flotation.<ref>{{Cite journal |last1=Rahman |first1=Reza M. |last2=Ata |first2=Seher |last3=Jameson |first3=Graeme J. |date=November 2013 |title=Froth recovery measurements in an industrial flotation cell |journal=Minerals Engineering |volume=53 |pages=193–202 |doi=10.1016/j.mineng.2013.08.003 |bibcode=2013MiEng..53..193R |issn=0892-6875}}</ref> Other extraction processes like leaching are effectively used for the extraction of secondary copper sulfides, but as demand for copper rises, extraction processes tailored for low-grade ores are required, due to the depletion of copper resources.<ref>{{Cite journal |last1=Yu |first1=Shichao |last2=Liao |first2=Rui |last3=Yang |first3=Baojun |last4=Fang |first4=Chaojun |last5=Wang |first5=Zhentang |last6=Liu |first6=Yuling |last7=Wu |first7=Baiqiang |last8=Wang |first8=Jun |last9=Qiu |first9=Guanzhou |date=January 2022 |title=Chalcocite (bio)hydrometallurgy—current state, mechanism, and future directions: A review |journal=Chinese Journal of Chemical Engineering |volume=41 |pages=109–120 |doi=10.1016/j.cjche.2021.12.014 |s2cid=245562646 |issn=1004-9541}}</ref> Processes including in situ, dump, and heap leaching are cost-effective methods that are suitable for extracting copper from low-grade ores.<ref>{{Cite journal |last=Watling |first=H. R. |date=October 2006 |title=The bioleaching of sulphide minerals with emphasis on copper sulphides — A review |journal=Hydrometallurgy |volume=84 |issue=1 |pages=81–108 |doi=10.1016/j.hydromet.2006.05.001 |bibcode=2006HydMe..84...81W |issn=0304-386X}}</ref>

Extraction processes for secondary copper sulfides and low-grade ores includes the process of heap bioleaching. Heap bioleaching presents a cost efficient extraction method that requires a less intensive energy input resulting in a higher profit.<ref name="Panda-2015">{{Cite journal |last1=Panda |first1=Sandeep |last2=Akcil |first2=Ata |last3=Pradhan |first3=Nilotpala |last4=Deveci |first4=Haci |date=November 2015 |title=Current scenario of chalcopyrite bioleaching: A review on the recent advances to its heap-leach technology |journal=Bioresource Technology |volume=196 |pages=694–706 |doi=10.1016/j.biortech.2015.08.064 |pmid=26318845 |bibcode=2015BiTec.196..694P |s2cid=2254790 |issn=0960-8524}}</ref> This extraction process can be applied to large quantities of low-grade ores, at a lower capital cost with minimal environmental impact.<ref name="Panda-2015"/><ref>{{Cite journal |last=Brierley |first=C. L. |date=December 2008 |title=How will biomining be applied in future? |journal=Transactions of Nonferrous Metals Society of China |volume=18 |issue=6 |pages=1302–1310 |doi=10.1016/S1003-6326(09)60002-9 |issn=1003-6326}}</ref>

Generally, direct [[froth flotation]] is not used to concentrate copper oxide ores, as a result of the largely ionic and hydrophilic structure of the copper oxide mineral surface.<ref name="Feng-2022">{{Cite journal |last1=Feng |first1=Qicheng |last2=Yang |first2=Wenhang |last3=Wen |first3=Shuming |last4=Wang |first4=Han |last5=Zhao |first5=Wenjuan |last6=Han |first6=Guang |date=November 2022 |title=Flotation of copper oxide minerals: A review |journal=International Journal of Mining Science and Technology |volume=32 |issue=6 |pages=1351–1364 |doi=10.1016/j.ijmst.2022.09.011 |s2cid=253788625 |issn=2095-2686|doi-access=free |bibcode=2022IJMST..32.1351F }}</ref> Copper oxide ores are typically treated via chelating-reagent flotation and fatty-acid flotation, which use organic reagents to ensure adsorption onto the mineral surface through the formation of hydrophobic compounds on the mineral surface.<ref name="Feng-2022"/><ref>{{Cite journal |last1=Fuerstenau |first1=D. W. |last2=Herrera-Urbina |first2=R. |last3=McGlashan |first3=D. W. |date=February 2000 |title=Studies on the applicability of chelating agents as universal collectors for copper minerals |journal=International Journal of Mineral Processing |volume=58 |issue=1 |pages=15–33 |doi=10.1016/S0301-7516(99)00058-7 |bibcode=2000IJMP...58...15F |issn=0301-7516}}</ref>

Some supergene sulfide deposits can be leached using a [[bacterial oxidation]] heap leach process to oxidize the sulfides to sulfuric acid, which also allows for simultaneous leaching with sulfuric acid to produce a [[copper sulfate]] solution.<ref>{{Cite journal |last1=Kariuki |first1=Stephen |last2=Moore |first2=Cory |last3=McDonald |first3=Andrew M. |date=March 2009 |title=Chlorate-based oxidative hydrometallurgical extraction of copper and zinc from copper concentrate sulfide ores using mild acidic conditions |journal=Hydrometallurgy |volume=96 |issue=1 |pages=72–76 |doi=10.1016/j.hydromet.2008.08.008 |bibcode=2009HydMe..96...72K |issn=0304-386X}}</ref><ref>{{Cite journal |last1=Robertson |first1=S.W. |last2=Van Staden |first2=P.J. |last3=Seyedbagheri |first3=A. |date=December 2012 |title=Advances in high-temperature heap leaching of refractory copper sulphide ores |url=http://www.saimm.co.za/Journal/v112n12p1045.pdf |journal=Journal of the Southern African Institute of Mining and Metallurgy |volume=112 |issue=12 |pages=1045–1050 |via=ResearchGate}}</ref> For oxide ores, [[solvent extraction and electrowinning]] technologies are used to recover the copper from the [[pregnant leach solution]].<ref name="Ochromowicz-2008">{{Cite journal |last1=Ochromowicz |first1=Katarzyna |last2=Chmielewski |first2=Tomasz |date=January 2008 |title=Growing Role of Solvent Extraction in Copper Ores Processing |pages=29–36 |url=https://www.researchgate.net/publication/228679628 |journal=Fizykochemiczne Problemy Mineralurgii |volume=42}}</ref> To ensure the best recovery of copper, it is important to acknowledge the effect copper dissolution, acid consumption, and gangue mineral composition has on the efficacy of extraction.<ref name="Ochromowicz-2008" />

Supergene sulfide ores rich in native copper are refractory to treatment with sulfuric acid leaching on all practicable time scales, and the dense metal particles do not react with froth flotation media. Typically, if native copper is a minor part of a supergene profile it will not be recovered and will report to the [[tailings]]. When rich enough, native copper ore bodies may be treated to recover the contained copper by [[gravity separation]]. Often, the nature of the gangue is important, as clay-rich native copper ores prove difficult to liberate. This is because clay minerals interact with flotation reagents used in extraction processes, that are then consumed, which results in minimal recovery of a high grade copper concentrate.<ref>{{Cite journal |last1=Han |first1=Baisui |last2=Altansukh |first2=Batnasan |last3=Haga |first3=Kazutoshi |last4=Stevanović |first4=Zoran |last5=Jonović |first5=Radojka |last6=Avramović |first6=Ljiljana |last7=Urosević |first7=Daniela |last8=Takasaki |first8=Yasushi |last9=Masuda |first9=Nobuyuki |last10=Ishiyama |first10=Daizo |last11=Shibayama |first11=Atsushi |date=2018-06-15 |title=Development of copper recovery process from flotation tailings by a combined method of high‒pressure leaching‒solvent extraction |journal=Journal of Hazardous Materials |volume=352 |pages=192–203 |doi=10.1016/j.jhazmat.2018.03.014 |pmid=29609151 |s2cid=4879400 |issn=0304-3894|doi-access=free |bibcode=2018JHzM..352..192H }}</ref>