Question

Sulphide ores of metals are usually concentrated by Froth Flotation process. Which one of the following sulphide ores offers and exception and is concentrated by chemical leaching ?

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> AIPMT 2007

• A. Galena
• B. Copper pyrite
• C. Sphalerite
• D. Argentite

Answer 1

The correct option is D Argentite

Froth Floatation Process: This process is best suitable for sulphide(Sphalerite, galena) ores. The process is based on different wetting characteristic of the ore and gangue particles with water and pine oil. The ore is wetted by oil and impurities are wetted by water. Ore particles are adsorbed on potassium or sodium ethyl xanthate (as a collector) and come at the surface along with the froth. Froth stabilizer (cresols, aniline) stabilize the froth.

But Argentite is not concentrated by this method. The following method is used to concentration Argentite:
$A{g}_{2}S+4NaCN\to 2Na\left[Ag\right(CN{)}_2]+N{a}_{2}S$

Silver is obtained by reaction with $Zn$:

$2Na\left[Ag\right(CN{)}_2]+Zn\to N{a}_2[Zn\left(CN{)}_4\right]+2Ag$