Sollubility Product of the
Metallic Sulphurs

Tributsch proved that generally the parameter of more importance for the bacterial oxidation of metallic sulphurs is the product of corresponding sollubility.

This aspect over the mechanism of the bacterial lixiviation with Thiobacillus Ferrooxidans coincides with the publications of other authors such as Torma, Bosecker and Murr.

It is reasonable to suppose that an individual chemical equilibrium for each metallic sulphur exists according to the constance of the product of sollubility.

The bacterias are not necessarily obliged to have direct contact with the surface of the mineral; instead, it must be close enough to find with its enizmatic system the interesting ions for its metabolism and the supply of the necessary energy for its life.

The tests of bacterial lixiviation in airlift-bioreactors indicate these aspects:

- The bacterial activity is notably high, even though there exists a rapid circulation of the suspention and the contact of the bacteria with the surface of the grains of the minerals or concentrate is not performed under aspects of resting. If the direct contact between the bacteria and the crystals of the metallic sulphurs were necessary, a diminishing of the bacterial lixiviation in the airlift-bioreactors would be done.

A chemical equilibrium of the metallic sulphurs is thermodynamically formed according to the individual constance of the product of sollubility, which is trespassed by means of the bacterial metabolism which oxidates to the dissolved molecules; the metallic sulphurs are dissolved.

The chemical cynetic of the disolution of sulphured minerals can mainly be controlled:

• - By the chemical equilibrium of the dissolution of the metallic sulphur;
• - By the difusion of ions of the corresponding metallic sulphurs (corelation with the agitation and a little with the coefficiency of the temperature); or,
• - By the oxidations which follow the dissolution according to the postulated mechanism.