Gold - Au

Gold — chemical properties and water context

Gold is a soft, yellow transition metal that is resistant to corrosion. In water and wastewater engineering, gold is mainly relevant to mining, refining, jewellery and electronics process streams where recovery of dissolved or particulate precious metal may be important.

Atomic number	79
Standard atomic weight	196.966570 g/mol
Density	19.3 g/cm3
Melting point	1064.18 °C
Boiling point	2836 °C
Electron configuration	[Xe] 4f14 5d10 6s1

Chemical properties

Gold is in Group 11 and Period 6. The metal is chemically unreactive in most ordinary aqueous conditions, but it dissolves in certain complexing chemical systems. Depending on process conditions, dissolved gold can be present in complexes rather than as free Au ions.

Uses and applications

Gold is used in jewellery, electrical contacts, electronics, dentistry and specialized catalysts. Gold-bearing ores and industrial residues are processed to recover the metal; the methods used depend on ore and stream chemistry.

Gold in water treatment

Gold-bearing process liquors can contain complexed gold alongside cyanide, chloride or other ligands and competing metals. Precious-metal recovery methods, including ion exchange and sorption, have been studied for specific leach and refining solutions. Characterize the complexes and manage any hazardous co-contaminants, especially cyanide-bearing streams, under applicable process-safety and environmental requirements.

Environmental and health context

Gold itself is relatively unreactive, but its compounds and process reagents can present distinct hazards. Water-quality assessment should focus on the actual dissolved complexes, particles and associated process chemicals rather than on the bulk metal alone.

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