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Hydrometallurgy and Electrolytic Processes(Bello, Cabading, Pilapil, Tan)

Hydrometallurgy

- branch of extractive metallurgy which deals with the processes involving aqueoussolutions to extract metals from ores.  [1]

Hydrometallurgy is divided into three general areas:

●   Leaching

○ a mining technology that involves the treatment of mineral materials, mainly

oxidized containing desirable metals and which are reduced in size to be

subjected to a wet process with acidic or basic solutions to dissolve soluble

elements and concentrate in an enriched solution, so it is considered a

“hydrometallurgical” process.  [2]

●   Solution concentration and purification○ Precipitation is the selective removal of a compound of the targeted metal or

removal of a major impurity by precipitation of one of its compounds.

○ Cementation is the conversion of the metal ion to the metal by a redox reaction.

 A typical application involves addition of scrap iron to a solution of copper ions.

Iron dissolves and copper metal is deposited.

○ Solvent Extraction is a method to separate compounds based on their relative

solubilities in two different immiscible liquids. [4]

○ Ion Exchange involves a solution containing a mixture of metal ions is contacted

with a resin that is insoluble in the metal-ion solution.   [4]

○ Gas reduction. Treating a solution of nickel and ammonia with hydrogen affordsnickel metal as its powder.

○ Electrowinning is a particularly selective if expensive electrolysis process applied

to the isolation of precious metals. Gold can be electroplated from its solutions.

●   Metal or metal compound recovery

○ involves the process of refining extracted metals for commercial use

○ Involves electrolytic processes

[Process]

The most common hydrometallurgical process is leaching, which involves dissolution of the

valuable metals into the aqueous solution. After the solution is separated from the ore solids,

the solution is often subjected to various processes of purification and concentration before the

valuable metal is recovered, either in its metallic state or as a chemical compound. The solution

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purification and concentration processes may include precipitation, distillation, adsorption, and

solvent extraction. The final recovery step may involve precipitation, cementation, or an

electrometallurgical process. [4]

Electrometallurgy involves metallurgical processes that take place in some form of electrolytic

cell. The most common types of electrometallurgical processes are electrowinning andelectro-refining. Electrowinning is an electrolysis process used to recover metals in aqueous

solution, usually as the result of an ore having undergone one or more hydrometallurgical

processes. The metal of interest is plated onto a cathode, while an anode is composed of an

inert electrical conductor. Electro-refining is used to dissolve an impure metallic anode (typically

from a smelting process) and produce a high purity cathode. Fused salt electrolysis is another

electrometallurgical process whereby the valuable metal is dissolved into a molten salt, which

acts as the electrolyte, and the valuable metal collects on the cathode of the cell. [3]

Sources:

[1] Brent, H.., "Metallurgy, Survey" in Kirk-Othmer Encyclopedia of Chemical Technology, 2000,

Wiley-VCH, Weinheim. doi:10.1002/0471238961.1921182208091911.a01

[2] Estefani, Guillermo. "What Is Metallurgical Leaching?". Artinaid. N.p., 2013. Web. 29 Jan.

2016.

[3] Perry, C.B., Extraction Metallurgy., http://slideplayer.com/slide/6393311/

[4]"Extractive Metallurgy". Boundless (2015): n. pag. Web. 29 Jan. 2016.

http://slideplayer.com/slide/6393311/