User:Sustainavaleity/Leaching (metallurgy)

Lead (UNEDITED FROM ORIGINAL)
Leaching is a process widely used in extractive metallurgy where ore is treated with chemicals to convert the valuable metals within 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)

Ancient History
The origins of leaching can be traced all the way back to alchemy. Jabir Ibn Hayyan, an Arab alchemist in the 8th and 9th centuries, discovered a substance he coined "aqua regia" ("royal water" in Latin). Aqua regia was a combination of hydrochloric acid and nitric acid, and was found to be effective in dissolving gold, which was previously thought to be insoluble.

In the 16th century, heap leaching became commonly used to extract copper. Primarily used in the Germany and Spain, pyrite would be brought to the surface and left out in the open. The pyrite would be set outside for months at a time, where rain and air exposure would lead to chemical weathering. Through this process, a solution containing copper sulfate would be collected from the heap of pyrite. By using a process called cementation, metallic copper would be derived from the solution.

From 1767-1867, the production of potash in Quebec became an important industry to supply France's glass and soap manufacturers. Potash was most frequently made from the ash remains of wood-burning stoves and fireplaces, which were agitated with water and filtered. Once evaporated, the remains would be potash. 400 tons of hardwood would be required to burn to yield one ton of potash.

Pre-World War II
Cyanidization


 * 1) Scheele?
 * 2) Elsner?
 * 3) MacArthur and Cyanidization
 * 4) Bodlander and peroxide?
 * 5) Dorr agitators and filtration plants
 * 6) cementation -> gold
 * 7) explosion in industry

Bayer?


 * 1) Louis Le Chatelier?
 * 2) Bayer
 * 3) Bauxite leaching
 * 4) seeding
 * 5) crystallinity

20th century

In 1858, Adolf von Patera, an Austrian metallurgist, utilized lixiviation to 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 replace the existing Russell Process. Cyanidation was much more efficient and had a recovery rate of up to 90%. '''

'''Leading up to World War I, many new ideas for leaching processes were proposed. This included using ammonia solutions for copper sulfides, and nitric acid for leaching sulfide ores. Most of these ideas fizzled out into obscurity due to the high cost of the leaching agents required. '''

Modern Leaching
'''As a result of the Manhattan Project in the 1940s, the United States government needed ready access to uranium. Many different techniques in leaching were quickly employed at a large scale. Both synthetic resins and organic solvents were used early on to extract uranium. Ultimately, the use of organic solvents was less tedious compared to ion exchange through synthetic resins, and further production of uranium and other rare earth metals moved towards solvent extraction. '''

In the 1950s, pressure hydrometallurgy was developed for the leaching of multiple different metals, such as sulfide concentrates and laterites. Particularly at the Mines Branch in Ottawa (now known as CANMET), it was demonstrated that pyrrhotite-penthandite concentrate could be treated in autoclaves, with the resulting nickel in a solution while iron oxide and sulfur remain in the residue. This process was later used in other nickel recovery operations across the globe.

In the 1960s, heap and in situ leaching became widely practiced, particularly for copper. In situ leaching was later used for the extraction of uranium as well.

Pressure leaching was further refined in the 1970s and 80s.

Peer Review Response
04/05/2024 - Alohr77

Citing the sources was going to be done at the end, but it would definitely be smarter to do it during writing, so I don't forget where I found something. At this point, it's easy because we only really have one good source, but in the future if we expand our bibliography, it may become a mess.

I'd love to add more modern examples of leaching, but for right now I need to focus solely on the prior history of leaching due to how obscure the information can be. Leaching later on in history is pretty simple to find, so I won't have too much trouble adding it in towards the end of the project.

I think a lot of things that have been suggested are things that should be applied to the entire article. Unfortunately, the original lead section and even the definition of leaching in metallurgy is pretty inaccurate, but considering how much work we need to do to find information on the history of leaching, it's unreasonable to update the whole entire article. It's absolutely something I'd like to do, but not something I want to put on my or my partner's shoulders.

I'd also like to look for more sources, as was suggested. After I've exhausted this main source that I have right now, I want to fill in the blanks with anything else I can find. Again, for some reason this is a fairly obscure topic so I'm trying to temper my own expectations.