Cristina Pogliani

Bioleaching of covellite using pure and mixed cultures of Thiobacillus ferrooxidans and Thiobacillus thiooxidans

Abstract A high level of covellite (CuS) dissolution was observed in systems containing Thiobacillus thiooxidans and iron. This activity was higher than with Thiobacillus ferrooxidans in the same medium and lower than that with T. ferrooxidans in the absence of iron. In mixed cultures, covellite dissolution appeared to be associated with T. ferrooxidans in the presence of iron and sulphur but with T. thiooxidans when these were absent.

Effect of iron (III) and its hydrolysis products (jarosites) onThiobacillus ferrooxidans growth and on bacterial leaching

SummaryThere is a significant inhibition of the growth ofThiobacillus ferrooxidans in the presence of iron (III), but this does not affect bacterial leaching. Moreover, the insoluble hydrolytic products (jarosites) have no influence, except from a mechanical point of view when they are generated ‘in situ’.

A need for direct contact with particle surfaces in the bacterial oxidation of covellite in the absence of a chemical lixiviant

SummaryFor bio-leaching, direct contact is needed between Thiobacillus ferrooxidans and covellite (CuS) which oxidizes by a direct mechanism.

Indirect bioleaching of covellite by Thiobacillus thiooxidans with an oxidant agent

SummaryHigh copper extraction by the action of Thiobacillus thiooxidans (T.t.) on covellite in presence of iron(III) is explained by indirect mechanism, in which T.t. only oxidizes the layer of sulphur that covers the sulphide surface allowing sulphide oxidation by iron(III). In cultures on elemental sulphur with iron(III) T.t. is not able to use iron(III) as an acceptor of electrons in sulphur oxidation; iron(III) only oxidizes those intermediates which were generated in the aerobic oxidation of sulphur.

Enhancement of Copper Dissolution from a Sulfide Ore by Using Thiobacillus thiooxidans

Copper dissolution from a sulfide ore (with covellite as the main copper phase) was investigated in cultures of Thiobacillus ferrooxidans or Thiobacillus thiooxidans and in abiotic controls. In unsupplemented media, T. ferrooxidans was more efficient than T. thiooxidans. In the presence of ferric iron, the dissolution of covellite was not significantly different in cultures inoculated with T. ferrooxidans or T. thiooxidans. However, the most extraction was found in T. thiooxidans cultures supplemented with ferrous sulfate. The first results were explained by the mechanism proposed by Schippers and Sand (Appl Envir Microbiol 65:319-321, 1999), which involves polysulfides and sulfur as intermediates. This mechanism was extended to explain the behavior of T. thiooxidans culture supplemented with ferrous iron.

Use of packed bed bioreactors application to ores bioleaching

SummaryThe behaviour of glass beads, silicagel and activated carbon particles as bacteria supports for using in backed bed bioreactor has been compared. No important difference was found. Additionally the performance of a bioreactor with glass beads was compared with that of a conventional percolating column in the bioleaching of a copper sulphide ore. Results showed higher copper extraction using the bioreactor.

[11] Development of Thiobacillus biofilms for metal recovery

Publisher Summary This chapter describes the preparation of two types of biofilms: (1) Thiobacillus ferrooxidans, immobilized by the two more widely used techniques—attachment and entrapment—for the production of sulfuric acid and (2) attached Thiobacillus ferrooxidans cells for the ferrous iron oxidation. In both cases, whole and viable cells are used. These bacteria are all gram-negative, mesophilic, autotrophic, and obligately acidophilic. T.ferrooxidans is able to use ferrous iron or reduced sulfur compounds as electron donors, whereas T. thiooxidans is only capable of using reduced sulfur compounds. Ferric iron and sulfuric acid are the final products of these oxidation processes. The ability of acidophilic bacteria to assist in the recovery of metals by the dissolution of sulfide minerals is well known, but the mechanism is not fully understood. The chapter also relates the application of these biofilms to recover metals from the leaching of a sulfide ore.