Editing Chalcopyrite (section)

=== Hydrometallurgical processes ===
Chalcopyrite is an exception to most copper bearing minerals. In contrast to the majority of copper minerals which can be leached at atmospheric conditions, such as through [[heap leaching]], chalcopyrite is a [[refractory]] mineral that requires elevated temperatures as well as oxidizing conditions to release its copper into solution.<ref name="Schlesinger-2011-2">{{Cite book |url=https://www.worldcat.org/oclc/742299078 |title=Extractive Metallurgy of Copper |date=2011 |publisher=Elsevier |first1=Mark E. |last1=Schlesinger |isbn=978-0-08-096789-9 |location=Amsterdam |pages=281–317 |oclc=742299078}}</ref> This is because of the extracting challenges which arise from the 1:1 presence of iron to copper,<ref name="Daehn-2022-2">{{Cite journal |last1=Daehn |first1=Katrin E. |last2=Stinn |first2=Caspar |last3=Rush |first3=Lucas |last4=Benderly-Kremen |first4=Ethan |last5=Wagner |first5=Mary Elizabeth |last6=Boury |first6=Charles |last7=Chmielowiec |first7=Brian |last8=Gutierrez |first8=Carolina |last9=Allanore |first9=Antoine |date=2022-08-29 |title=Liquid Copper and Iron Production from Chalcopyrite, in the Absence of Oxygen |journal=Metals |language=en |volume=12 |issue=9 |pages=1440 |doi=10.3390/met12091440 |issn=2075-4701|doi-access=free |hdl=1721.1/145313 |hdl-access=free }}</ref> resulting in slow leaching kinetics.<ref name="Schlesinger-2011-2" /> Elevated temperatures and pressures create an abundance of oxygen in solution, which facilitates faster reaction speeds in terms of breaking down chalcopyrite's crystal lattice.<ref name="Schlesinger-2011-2" /> A hydrometallurgical process which elevates temperature with oxidizing conditions required for chalcopyrite is known as '''pressure oxidation leaching'''. A typical reaction series of chalcopyrite under oxidizing, high temperature conditions is as follows:

i) 2CuFeS<sub>2</sub> + 4Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> -> 2Cu<sup>2+</sup>+ 2SO<sub>4</sub><sup>2-</sup> + 10FeSO<sub>4</sub>+4S

ii) 4FeSO<sub>4</sub> + O<sub>2</sub> + 2H<sub>2</sub>SO<sub>4</sub> -> 2Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> +2H<sub>2</sub>O

iii) 2S + 3O<sub>2</sub> +2H<sub>2</sub>O -> 2H<sub>2</sub>SO<sub>4</sub>

(overall) 4CuFeS<sub>2</sub>+ 17O<sub>2</sub> + 4H<sub>2</sub>O -> 4Cu<sup>2+</sup>+ 2Fe<sub>2</sub>O<sub>3</sub> + 4H<sub>2</sub>SO<sub>4</sub><ref name="Schlesinger-2011-2" />

Pressure oxidation leaching is particularly useful for low grade chalcopyrite. This is because it can "process concentrate product from [[Froth flotation|flotation]]"<ref name="Schlesinger-2011-2" /> rather than having to process whole ore. Additionally, it can be used as an alternative method to pyrometallurgy for variable ore.<ref name="Schlesinger-2011-2" /> Other advantages hydrometallurgical processes have in regards to copper extraction over pyrometallurgical processes ([[smelting]]) include:

* The highly variable cost of smelting
* Depending on the location, the amount of smelting availability is limited
* High cost of installing smelting infrastructure
* Ability to treat high-impurity concentrates
* Increase of recovery due to ability of treating lower-grade deposits on site
* Lower transport costs (shipping concentrate not necessary)
* Overall lower cost of copper production<ref name="Schlesinger-2011-2" />

Although hydrometallurgy has its advantages, it continues to face challenges in the commercial setting.<ref name="Daehn-2022-2" /><ref name="Schlesinger-2011-2" /> In turn, smelting continues to remain the most commercially viable method of copper extraction.<ref name="Daehn-2022-2" />