Process for biolixiviating copper sulfides by indirect contact with separation of effects

DETAILED DESCRIPTION The bacterial oxidation of the ferrous ion can be carried out with two different devices: the model of bacterial suspension or the carried bacterial film.
As their names indicate, in the first device the bacteria are dispersed in a liquid medium which can be mixed or not mixed.
In the second device, the bacteria are fixed on a film formed by the bacteria and a binding cement consisting of basic iron sulfates.
Said film is carried, in general, on an inert solid in fixed beds or on revolving biological contactors.
Numerous studies comparing the advantages of the suspension and the film devices indicate that the carried film model is much more effective than the bacterial suspension for the following reasons.
When the bacteria are dispersed in a liquid medium, they consume a certain amount of energy in carrying out locomotion work.
On the other hand, when the bacteria form part of the film, their energy is completely spent in bacterial growth, which causes the coefficient of performance to be considerably greater.
In addition, the supply of O.
sub.
2 and CO.
sub.
2 contained in the air is much more direct and therefore more available to the carried bacterial film model.
The ferric sulfate operates according to the following reactions: SCu+2Fe.
sup.
3+ .
fwdarw.
S.
sup.
2 +2Fe.
sup.
++ +Cu.
sup.
++ SCu.
sub.
2 +4Fe.
sup.
3+ .
fwdarw.
S.
sup.
o +2Cu.
sup.
++ +4Fe.
sup.
++ S.
sub.
2 CuFe+4Fe.
sup.
3+ .
fwdarw.
2S.
sup.
o +Cu.
sup.
++ +5Fe.
sup.
++ However, its direct use according to the stoichiometry of the above reactions would imply that the lixiviating liquor obtained has a ferrous ion concentration between two and five times greater than Cu, which would considerably complicate the subsequent treatment stages.
This problem can be solved by using amounts of ferric sulfate which are much less than the stoichiometry requires.
Once the ferric ion has been depleted and has been converted into ferrous ion, it is sent to a reoxidation stage and is recirculated to the reactor.
In this manner, the same lixiviating liquor leaves the reactor, is reoxidized and recirculated continuously before leaving the circuit