Renata de Barros Lima - UFRJ

ABSTRACT
LIMA. Renata de Barros. Bioleaching of Flotation Concentrate Containing Copper
Sulphides. Advisors: Profª. Dra. Selma Gomes Ferreira Leite e Prof. Dr. Luis Gonzaga
Santos Sobral. Rio de Janeiro: UFRJ/EQ, 2006. Dissertation (Master of Technology of
Chemical and Biochemical Processes)
The bio-assisted leaching of the flotation concentrate, produced in Caraíba's Mining
facilities, was initiate with the use of microorganisms present in the acid mine drainage
collected directly from the copper mine located at Caraíba Mining Company, besides the
microorganism strain of the Acidithiobacillus ferroxidans species. That strain was
originated from a primary copper ore, from Surubim mine/Bahia, belonging to the same
mining company. The concentrate under study, after being characterized technologically,
was constituted, mainly, of chalcopyrite (CuFeS2) and bornite (Cu5FeS4) with contents,
approximately, of 70 and 30%, respectively. The high chalcopyrite content in that
concentrate caused, due to its refractory characteristics, a larger difficulty of copper
extraction from this sulphide using, only, the aforementioned microorganism. That was
verified, according to the analytical results of copper, ferrous and ferric ions concentrations
and the monitoring of pH and Eh values, along the bioleaching tests, as being due to no
sulphuric acid generation, during its solubilization, which demanded a constant monitoring
of those parameters to avoid, mainly, the pH raising that would provoke the precipitation of
iron salts (hydroxides and jarosite). That phenomenon was verified, in some tests, due,
certainly, to a sudden pH raising and confirmed, through x –ray diffraction analysis, as
being a jarosite precipitate, which contains, in its composition, ferric ions decreasing, in a
detrimental way, the oxidizing power of the reaction system. Independent of the
aforementioned inconveniences, proceeding the operational adjustments, a copper
extraction around 67% was reached within 62 days.
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