Abstract: The weathering of kimberlite ores leads to the weakening of the kimberlite structure,
which allows the use of less intensive comminution procedures during the liberation of diamonds
from the ore, resulting in a decrease in potential damage to the diamonds. The possibility to use
iron- and sulphur-oxidising chemolithotrophic microorganisms as a way to accelerate the
weathering of kimberlite ores was evaluated. It was demonstrated that the presence of sulphuric
acid as well as ferric iron could result in changes in the clay component of these ores. The results
provided promising evidence that weathering can be successfully accelerated, but showed that the
degree of transformation varies between different kimberlite types with different mineralogical
Abstract: Bioleaching of a sulfide ore was investigated using a consortium of thermophilic bacteria
and archaea. The consortium was obtained through successive enrichment procedures (using M88
with tetrathionate) after isolating from two different places into the geothermal area (Baño 9 and
Las Maquinitas) of the Copahue volcano (in the north of Neuquén province in Argentina).
Bioleaching experiments were carried out in 250-ml shake flasks with 100 ml of media and 1 g of
the sulfide ore. Flasks were incubated at 150 rpm and 70 oC. The major constituents of the ore (La
Resbalosa, Argentina) were sphalerite, pyrite, chalcopyrite and galena. The sample used throughout
bioleaching experiments contained 22.5 % Zn. Two different media (0K and M88) were evaluated
with and without the addition of elemental sulfur. Genetic diversity analysis of the microbial
community was performed by PCR amplification of bacterial 16S rDNA fragments and analyzed by
DGGE (denaturing gradient gel electrophoresis). The 16S rDNA was amplified by using eubacteria
and archaea primers. Metal concentration, Eh and pH were periodically analyzed. Solid residues
were filtered, washed, dried and finally analyzed by XRD and XRF. After 45 days, more than 50 %
of zinc and about 100 % of the copper were solubilized. Galena and jarosite were detected in the
solid residues. The data indicated that the dominant acidophiles were bacteria or archaea according
to the media. M88 media allowed an important decrease of pH and higher zinc extractions while the
presence of sulfur did not show significant influence on the zinc recovery.
Abstract: The electrochemical response of chalcopyrite was studied using electrochemical noise
analysis (ENA). The assay was carried out under constant aeration using 30 mL in two
electrochemical cells containing iron-free mineral salts solution. These cells were initially
monitored for 56 hours. After 72 hours, 7.25×1010 cells mL-1 of A. ferrooxidans strain LR were
added in both cells and monitored until 128 h. Subsequent to this period, 0.927 mmol L-1 of silver
ions and 400 mmol L-1 of chloride ions were added each one separately. Both conditions were
monitored until 168 hours. According to results obtained, it was observed that Cl- ions addition
induced an accelerated corrosion process. However, there is a tendency of the system to reach the
stationary state due to repassivation of the electrodic surface. In the other side, the Ag+ addition
contributed for the maintenance of the oxidant atmosphere, in spite of controversial effect caused by
considerable variations in the Rn values, resulting in a instability in the chalcopyrite reactivity.
Abstract: Ultra-fine iron particles are difficult to treat by conventional mineral processing methods.
Thus bioleaching is an attractive alternative for effective removal of iron minerals. The removal of
oxidic Fe-phases from industrial silicates via bioleaching needs to be optimized with regard to the
rate of iron reduction and dissolution. A new role for chelators as the low addition of AQDS or
NTA during bacterial quality improvement of non-metallics, resulted in stimulating of Fe
dissolution under non-controlled anaerobic conditions. AQDS stimulated bacterial iron reduction
and Fe2+ concentration in solution was higher than Fe3+. However, NTA non-stimulated iron
reduction, but increased bacterial iron dissolution in form of Fe3+. Changes in iron removal from
samples were used to assess the chelator effectiveness of the heterotrophic bioleaching process.
Chelators might be added to iron-contaminated non-metallics during bioleaching processes for
stimulation of rate of iron removal.
Abstract: The acid mine drainage (AMD) generating sulfidic tailings have a total mass of
1,639,130 t containing 1.65 g/t Au, 34.5 g/t Ag, 7.74 % Fe, 5.91 % S, 3.2 % As, 0.75 % Zn and 0.05
% Cu. The precious metals Au and Ag are enriched in the fine fractions. Approximately 35 % of the
material is below 25 /m in size and 53 % below 63 /m. Electron microprobe analysis of a sulfide
concentrate of the tailings, produced by gravity separation, proved the occurrence of pyrite and
arsenopyrite with appreciable sphalerite and galena. Refractory gold (up to 316 g/t) is hosted in Asrich
zones of some arsenopyrites. Approximately 200 g of the sulfide concentrate of the tailings was
biooxidized in laboratory shake flasks using an adapted mixed culture of Acidithiobacillus
ferrooxidans (Ram 6F), Acidithiobacillus thiooxidans (Ram 8T) and Leptospirillum ferrooxidans
(R3). During biooxidation, arsenopyrite was preferentially dissolved and the secondary mineral
tooeleite (Fe8(AsO4)6(OH)5·H2O) precipitated. The following cyanidation of the biooxidized sulfide
concentrate showed a recovery of 97 % and 50 % for Au and Ag, respectively. The values were 56
% and 18 % for the untreated concentrate. The recovery of Au and Ag from the tailings
significantly reduces the costs for the tailings remediation to mitigate AMD release.
Abstract: High content of organic compounds is characteristic for black shale-type ores.
Metalloporphyrins are known as the most stable and resistant for biodestruction compounds of
organic matter. Based on results obtained in previous studies, four metalloporphyrins were
synthesised . The experiments of biodestruction of organic matter extracted from polish black
shale ore samples and of the synthetic metalloporphyrins were provided using autochthonous,
heterotrophic bacteria mixtures isolated form polish black shale samples, and two Streptomyces
species. It was found that biodestruction of black shale organic matter and copper- and vanadylporphyrins
is possible, but it is a long term process. Porphyrins of Ni and Fe were resistant to
Abstract: Electrical and electronic equipment (EEE), e.g. printed circuit boards, contain
substantial amounts of metals, e.g. Cu, Pb and Sn. The objective of this work was to
investigate the bioleaching of a material, originating from a technical waste processing
facility, as one possible way of a complete separation of the metals from the polymer carrier.
During the leaching experiments the mechanism of the leaching process was investigated, and
biofilms and precipitates were analyzed by microscopical (SEM) and spectroscopical methods
(EDX, XRF, XRD). The enhanced formation of exopolymer layers seems to promote the
precipitation of secondary mineral particles beneath and the sorption of particles from the
suspension on the layer surface.
Abstract: A rich-in- carbonates copper ore was subjected to bioleaching under alkaline pH
conditions by means of different microorganisms or their metabolites. The ore contained 1.40%
copper, 1.94% sulphur, 3.25% iron and 20.3% carbonates, and had a pH of 8.6 and a highly positive
net neutralization potential (325 kg CaCO3/t). Copper was present mainly as different sulphide
minerals (bornite, covellite, chalcopyrite). The leaching was carried out by means of the shake-flask
technique at 32 oC using finely ground (minus 100 μm) ore. The following microorganisms were
used to leach the sample: ammonifying bacteria (related to the genera Bacillus, Acinetocater and
Vibrio); heterotrophic bacteria (Acetobacter and Pseudomonas) and fungi (Asperillus niger and
Penicillium chrysogenum) producing citric acid; heterotrophic bacteria (Micrococcus, Alcaligenes
and Bacillus) producing amino acids (mainly alanine); basophilic chemolithotrophic bacteria
(Thiobacillus thioparus, Hallothiobacillus neapolitanus, Starkeya novella; ”silicate bacteria”
(Bacillus circulans) producing organic acids and exopolysaccharides; bacteria possessing urease
enzymatic activity (Corynebacterium). The best results were achieved by means of a mixed culture
of urease-possessing bacteria, which under certain conditions was able to solubilize 64.4% of the
copper within 30 days of leaching.
Abstract: Cuban serpentines are known as one of the richest deposits of Ni and Co in the world.
These ores are usually treated by pyrometallurgy or by hydrometallurgy. These processes generate
huge volumes of mining residues, which still contains high amounts of Ni (0.25 %) and Co (0.09
%). Since metals are partially oxidized, the chances to use sulfur-oxidizing bacteria
(Acidithiobacillus thiooxidans) which are able to generate sulfuric acid to leach the residues from
Caron process have been evaluated. Thus, in this work, inorganic and organic acids produced in
cultures with A. niger or A. thiooxidans respectively were used to study the extraction of Co and Ni
from laterite tailings. The results were compared with those obtained in leaching experiments with
direct inoculation of those microorganisms. 7 and 16 % of Ni and Co were leached after 3 days
using A. niger and sucrose as carbon source. In stage batch one using A. thiooxidans and elemental
sulfur as energy source higher percentages of metal solubilization were reached after 15 days. In
stage batch two experiments were carried out using inorganic and/or organic bioacids. Metal
recoveries in stage batch two using sulfuric bioacid were higher (79 % Ni and 58 % Co) than those
obtained with citric bioacid (2.4 % Ni, and 38% Co). However metal recoveries using chemical
leaching with citric acid were much higher (80.4 % Ni and 50 % Co using 0.5 M citric acid). Since
the mineralogy composition of raw material is a parameter very important to select the leaching
agent of oxide ore, the leaching of residue nickel-ferrous of the Caron process with bio-sulfuric acid
produced in A. thiooxidans cultures could be an attractive alternative in the development of a
sustainable technology in Cuban mining-metallurgy industry.
Abstract: In this work, bioleaching of iron from a kaolin sample was carried out using two different
strains of Aspergillus niger, and the effects of strain type, pulp density, and addition time of clay on
the iron removal were investigated using a full factorial design. It is concluded that strain type has
the most significant effect on the iron removal. Also, the highest removal extent was 42.8% that
was achieved by using the strain isolated from pistachio shell at the pulp density of 20 g/l, when the
clay was added at the beginning of the experiments.
The results showed that for the experiments in which the clay was added in the first day of
cultivation, the average organic acids concentration (citric acid: 5.6 g/l, and oxalic acid: 4.54 g/l)
were higher in comparison to those experiments in which the clay was added in the third day (citric
acid: 5.25 g/l, and oxalic acid: 2.87).