Collect information about extraction of metals of low reactivity silver, platinum and gold and prepare a report.

Extraction of silver

1) Silver occurs in both combined state as well as in the free state. The important ores of silver are Argentite (Ag₂S) copper, Silver glance, Horn silver, Ruby silver etc.

2) Silver is extracted from the ore-Argentite (Ag₂S)

3) The ore is crushed, concentrated and then treated with sodium cyanide solution.

4) The reaction forms sodium argento cyanide [Na[Ag(CN)₂]].

Ag₂S + 4 NaCN → 2 Na [Ag(CN)₂] + 2 Ag.

5) This solution of sodium argento cyanide combined with zinc dust forms tetra ayano zincate and principle silver. This precipitated silver is called spongy silver.

Zn + 2 Na [Ag(CN)₂] → Na₂ [Zn(CN)₄] + 2 Ag.

6) The spongy silver is fused with potassium nitrate to obtain pure silver. Then the silver obtained is purified by the electrolytic process.

Extraction of Platinum

1) Platinum is rarely found on its own, but in combination with other base & precious metals.

2) The extraction process of platinum is quite complex, which includes milling the ore and smelting it at high temperatures. This removes base metals notably the concentrate PGM (platinum Group Metals) – gold, platinum & palladium.

3) The PGM matter is further processed by electrolysis to remove nickel, cobalt & copper.

4) The high grade concentrate is treated by solvent extraction distilling, ion- exchange treatments to separate the PGM’s into its separate metals.

Extraction of Gold

1) Gold is usually found alone or alloyed with mercury or silver.

2) In all methods of gold ore refining, the ore is usually washed and filtered at the mine, then sent to the mill. At the mill, the ore is ground into smaller particles with water, then ground again in a ball mill to further pulverize the ore.

3) Several processes can be used to separate the gold from its ore, They are-

a. Carbon-in-pulp Method:

i. In this method, the ground ore is mixed with water before cyanide is added. Then carbon is added to bond with the gold.

ii. The carbon-gold particles are put into a caustic carbon solution, separating out in the gold.

b. Cyanide process

i) The ground ore is put in a tank containing a weak cyanide solution, and then zinc is added.

ii) The zinc causes a chemical reaction which separates the gold from the ore.

iii) The gold is then removed from the solution with a filter press.