The Mond process, sometimes known as the carbonyl process, is a technique created by Ludwig Mond in 1890, to extract and purify

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

. The process was used commercially before the end of the 19th century, and particularly by the International Nickel Company in the

Sudbury Basin The Sudbury Basin (), also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geology, geological structure in Ontario, Canada. It is among the oldest- and largest-known List of impact structures on Earth, impact structures ...

. This process converts nickel oxides into nickel metal with very high purity being attainable in just a single step.

Synopsis

This process involves the fact that

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

combines with

readily and reversibly to give

nickel carbonyl Nickel carbonyl (IUPAC name: tetracarbonylnickel) is a Organonickel chemistry, nickel(0) organometallic compound with the chemical formula, formula Ni(CO)4. This colorless liquid is the principal metal carbonyl, carbonyl of nickel. It is an React ...

. No other element forms a carbonyl compound under the mild conditions used in the process. This process has three steps: 1. Nickel oxide reacts with

syngas Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as ...

at 200 °C to give nickel, together with impurities including

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

and

cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...

. :NiO(s) + H₂(g) → Ni(s) + H₂O(g) 2. The impure nickel reacts with

at 50–60 °C to form the gas

, leaving the impurities as solids. :Ni(s) + 4 CO(g) → Ni(CO)₄(g) 3. The mixture of nickel carbonyl and syngas is heated to 220–250 °C, resulting in decomposition back to nickel and carbon monoxide: :Ni(CO)₄(g) → Ni(s) + 4 CO(g) Steps 2 and 3 illustrate a chemical transport reaction, exploiting the properties that (1)

and

readily combine to give a volatile complex and (2) this complex degrades back to nickel and carbon monoxide at higher temperatures. The decomposition may be engineered to produce powder, but more commonly an existing substrate is coated with nickel. For example, nickel pellets are made by dropping small, hot pellets through the carbonyl gas; this deposits a layer of nickel onto the pellets. This process has also been used for plating nickel onto other metals, where a complex shape or sharp corners have made precise results difficult to achieve by electroplating. Although the results are good, the toxicity makes it impractical as an industrial process. Such parts are now plated by

electroless nickel plating Electroless Deposition, Electroless nickel-phosphorus plating, also referred to as ''E-nickel'', is a chemical engineering, chemical process that deposits an even layer of nickel-phosphorus alloy on the surface of a solid substrate, like metal o ...

instead.

Synopsis

See also

References

Further reading