Preparation. The copper subgroup metals are mined predominately in native form that influences upon their industrial production.

The copper subgroup metals are mined predominately in native form that influences upon their industrial production.

Copper. The following methods of production are used:

1. Annealing of sulfides

2Cu₂S + 3О₂ = 2Cu₂О + 2SО₂

2Cu₂O + Cu₂S = 6Cu + SО₂.

2. Hydrometallurgical method. To do so the ore is processed by H₂SO₄ or Fe₂(SO₄)₃ solutions and soluble copper sulfate is formed:

(CuOH)₂CO₃ + 2H₂SO₄ = 2CuSO₄ + 3H₂O + CO₂

Cu₂S + 2Fe₂(SO₄)₃ = 2CuSO₄ + 4FeSO₄ + S

The next step is electrodeposition of copper by electrolysis or cementation by Fe powder

Fe + Cu²⁺(aq) → Cu + Fe^{2 +} (aq)

Silver

Silver is mostly produced from polymetallic lead-zinc ores that contain small amounts of silver. Metallic zinc is usually added to molten rough lead. Zinc forms intermetallic compounds with silver Ag₂Zn₃, Ag₂Zn₅ that are insoluble in molten Pb and come to the surface forming “silver foam”. This foam is removed from the surface of molten lead, zinc is distilled off (t_b (Zn) =906°С, t_b (Ag) = 2184°С). Then Ag is purified by electrorefining.

The extraction of silver depends upon the fact that it very readily forms a dicyanoargentate(I) complex, [Ag(CN)₂]^- (linear), and treatment of a silver ore with aqueous cyanide ion CN^- extracts the silver as this complex. The silver is then displaced from the complex by zinc:

2[Ag(CN)₂]^- + Zn = 4CN^- + Zn²⁺ + 2Ag

(Zinc forms only an unstable complex with the cyanide ion.)

Дата добавления: 2015-07-25