Chemistry 3250 Ethics Case Study 2

Cyanide and gold mining
Cyanide is used in gold mining to extract gold from low-grade ores.
The reaction is
4Au(s) + 8CN

(aq) + O2(g) + 2H2O(l) ! 4[Au(CN)2]

(aq) + 4OH

(aq)
:
The gold is then recovered by electrodeposition.
This process is typically carried out right at the mine site.
Cyanide is extremely toxic, so cyanide contamination of water is always
a concern.
Cyanide monitoring is routinely performed near mines.
In Canada, the maximum acceptable concentration of cyanide in drink-
ing water is 200 g=L.
http://people.uleth.ca/~roussel/C3250/Spring2012/ethics2handout.pdf