User:Geghk8/Leaching (metallurgy)

Existing Article (not my work)
For other uses, see Leaching.

Leaching is a process widely used in extractive metallurgy where ore is treated with chemicals to convert the valuable metals within the ore, into soluble salts while the impurity remains insoluble. These can then be washed out and processed to give the pure metal; the materials left over are commonly known as tailings. Compared to pyrometallurgy, leaching is easier to perform, requires less energy and is potentially less harmful as no gaseous pollution occurs. Drawbacks of leaching include its lower efficiency and the often significant quantities of waste effluent and tailings produced, which are usually either highly acidic or alkali as well as toxic (e.g. bauxite tailings).

There are four types of leaching:


 * 1) Cyanide leaching (e.g. gold ore)
 * 2) Ammonia leaching (e.g. crushed ore)
 * 3) Alkali leaching (e.g. bauxite ore)
 * 4) Acid leaching (e.g. sulfide ore)
 * 5) ****There might be a 5th one I'm not 100% I think there is Uranium Leaching

Leaching is also notable in the extraction of rare earth elements, which consists of lanthanides, yttrium and scandium.

Origins of Leaching in Metallurgy
Much of metallurgy, (or hydrometallurgy) origins are contributed to early alchemy, this is still true in specifically leaching. Early examples of leaching performed by alchemists resembled mixing iron with copper sulfate, yielding a layer of metallic copper. A notable development (discovery??) in leaching can be traced to Jabir Ibn Hayyan (720-813 AD), who is credited for the discovery of aqua regia. More specifically, heap leaching dates further back to the second century BC in China, where iron was combined with copper sulfate. By the time of the Northern Song Dynasty, a copper alloy was able to be recovered by leaching.

(Eastern history of leaching...)**Better title name??
The science of leaching started in the Middle Ages as a way to extract saltpeter, from organic matter. By the 16th century, Germany and Spain were also utilizing heap leaching much like the Northern Song Dynasty. They use it to dissolve and oxidate copper by exposing a pile of pyrite to air and rain and collecting a copper solution in a basin. Heap leaching, in this natural chemical-free form, was further developed to obtain different, more economically viable, types of ore.

The science was further refined by incorporating chemical lixiviation, which is a more applies more chemical manipulation and technique. In 1858 Adolf von Patera, a metallurgist in Austria utilized lixiviation separate soluble and insoluble compounds from silver in an aqueous solution. The technique of Patera's lixiviation was further developed by American E.H Russell around 1884, creating the "Russell Process". In 1887, when the cyanidation process was patented in England, it began to be incorporated into the existing leaching process, creating the more specific cyanide leaching, as mentioned previously.

Chemistry
Leaching is done in long pressure vessels which are cylindrical (horizontal or vertical) or of horizontal tube form known as autoclaves. A good example of the autoclave leach process can also be found in the metallurgy of zinc. It is best described by the following chemical reaction:


 * 2 ZnS + O2 + 2 H2SO4 → 2 ZnSO4 + 2 H2O + 2 S

This reaction proceeds at temperatures above the boiling point of water, thus creating a vapour pressure inside the vessel. Oxygen is injected under pressure, making the total pressure in the autoclave more than 0.6 MPa and temperature at 473-523 K.

The leaching of precious metals such as gold can be carried out with cyanide or ozone under mild conditions.

(Eastern history of leaching...)**Better title name??
The science of leaching started in the Middle Ages as a way to extract saltpeter, from organic matter. By the 16th century, Germany and Spain were also utilizing heap leaching much like the Northern Song Dynasty. They use it to dissolve and oxidate copper by exposing a pile of pyrite to air and rain and collecting a copper solution in a basin. Heap leaching, in this natural chemical-free form, was further developed to obtain different, more economically viable, types of ore.

The science was further refined by incorporating chemical lixiviation, which is a more applies more chemical manipulation and technique. In 1858 Adolf Von Patera, a metallurgist in Austria utilized lixiviation separate soluble and insoluble compounds from silver in an aqueous solution. Von Patera's process, though successful, did not generate much use due partly to the price of hyposulphite. Additionally, with Patera's process, if the sodium hyposulphite failed to dissolve perfectly, silver would often be caught in the extra solution and not properly extracted. The technique of Patera's lixiviation was further developed by American E.H Russell around 1884, creating the "Russell Process". Prior leaching processes often could not concentrate ores with too much base metal, something thing the Russel Process was able to solve, making it more lucrative. In 1887, when the cyanidation process was patented in England, it began to be incorporated into the existing leaching process, creating the more specific cyanide leaching, as mentioned previously.

Uranium Leaching?

Peer Review Response
Regarding the order of the article, I have not followed the training properly in editing the article, specifically in order that the existing article is in. I do intend to integrate my article with the existing article better by adjusting the headers/ sub-headings to make the overall article more cohesive. Regarding the comment on the jokes on the titles, I understand those of course do not belong in the article and this draft is suppose to appear as a finished product. I understand they may be better suited for the notes section, but they mainly act as a reminder to edit the header title to best describe the paragraph below. Truth be told, I am continuing to research as I am writing, and if the content find and I want to add seems relevant, it might shift the direction of the paragraph, maybe making the header title not as accurate anymore if I get more off topic. That being said, I intend to keep "the jokes" until the bulk of the writing is complete, and rename the headers when it comes time to.

Finally regarding the last comment paragraph. Yes, finding sources on this has been tricky, I think the biggest hurdle is that this process has been called so many different things throughout history (leaching, lixiviation, hydrometallurgy extraction etc.), so finding sources on an idea rather than just one word has been tricky. On the comment "science doesn't particularly change much but how things are done change pretty drastically", I don't know if I agree with that. I do agree, it would be great to find more sources throughout history, but again, it has been called different things and evolved form very simple beginnings to the complex chemical-industrial science of today.

In terms of rearranging the article so that the "chemistry" section is after the "origins of leaching" section, I believe that will be something I will have to discuss more with my partner to determine.