Cementation (metallurgy)

Cementation is a method for obtaining metals from solutions of the metal ion. It is a type of precipitation, in which ions are reduced to zero valence at a solid metallic interface. A cementation step often follows leaching.

Cementation of copper is a common example. Copper ions in solution, often from an ore leaching process, convert to metallic copper in the presence of solid iron. The iron oxidizes, and the copper ions are reduced through the electron transfers. The reaction is spontaneous because copper is higher on the galvanic series than iron.

: Cu2+(aq) + Fe(s) → Cu(s) + Fe2+(aq)

Cementation was a historically useful process for the production of copper, where the precipitated solid copper metal was recovered as flakes or powder on the surface of scrap iron.

Cementation is used industrially to recover a variety of heavy metals including cadmium, and the cementation of gold by zinc in the Merrill–Crowe process accounts for a substantial fraction of world gold production."Zinc cementation," R. Walton, Developments in Mineral Processing, volume 15, 2005, pages 589–601 https://www.sciencedirect.com/science/article/pii/S0167452805150248