2
The copper deportment as determined by copper-
sequential assay was 2.3% acid soluble copper, 5.7% cya-
nide soluble copper and 92.0% residual copper which often
relates to the presence of refractory chalcopyrite. This is fur-
ther summarized in Table 2.
Inoculum consists of a wild culture of iron and sulfur
oxidizing acidophilic bacteria grown on MKM salts and
ferrous iron. This inoculum is considered as the ideal lix-
iviant for reactor test work. The composition is shown in
Table 3.
Mine raffinate received from the site was used for reac-
tor test work. The raffinate composition is shown in Table 4.
Table 3. Composition of ferrous medium
Species Concentration (g/L)
H
2 SO
4 1
FeSO4·7H2O 15
(NH4)2SO4 0.4
MgSO
4 0.4
K
2 HPO
4 0.1
Table 4. Chemical assays of mine raffinate (g/L)
Al Cu Fe Mg Cl
Raffinate 3.0 0.03 0.3 5.8 5.4
Experimental Procedure
A series of mechanically agitated batch reactors were oper-
ated with 76g of ground ore (P100 0.106 mm), 2.5% pulp
density, ambient temperature, and at pH 2.1. Lixiviants
used were bacterial inoculum, treated raffinate, and treated
raffinate with supplemental iron (2 g/l Fe3+). One control
and one catalyzed reactor were run for each lixiviant. The
tests were agitated at 550 rpm and operated for 76 days.
At designated sampling intervals, measurements of
the solution weight, specific gravity (s.g.), pH, and ORP
were recorded. The leachates were submitted for multi-
element analysis by ICP-AES to determine the chemical
composition.
Upon termination of the tests, the leach slurry was fil-
tered to collect the pregnant leach solution (PLS). The resi-
due was washed with adjusted DI water (pH=2), air-dried,
and submitted for chemical analysis.
RESULTS AND DISCUSSION
Bacterial Sequencing
To investigate the microbial activity in the mine site raf-
finate, a sample of the raffinate, SX treated raffinate, and
inoculum were sent to a third-party lab to conduct bacterial
cell count and 16s RNA sequencing.
The raffinate samples had approximately one order of
magnitude lower cell concentrations than the inoculum.
This is expected because of the 5.4 g/L of Cl present in the
raffinate which is known to harm bacteria. The cell counts
of each lixiviant are summarized in Table 5 and Figure 1.
Due to the limited quantity of bacteria present within
the raffinate sample, the bacterial population was enhanced
by culturing the samples before 16s sequencing.
Examination of the 16s RNA sequencing data allows
for a more thorough understanding of the bacteria consortia
Table 1. Chemical assays of ore sample (%)
Cu Fe
Head 0.08 2.4
Figure 1. Microbial cell count for as-received mine raffinate,
treated mine raffinate and inoculum
Table 5. Results of microbial monitoring
Test ID Cells/mL
Raffinate 6.5E+07
Treated raffinate 6.0E+07
Inoculum 1.3E+08
Table 2. Cu-sequential leach results of ore sample (%)
CuT CuASa CuCNb CuResc
Head
(–¼" crushed)
0.002 0.005 0.081
0.088
Normalized to
head assay
2.27% 5.68% 92.0%
CuT: Total copper measured by the sequential leach analysis
CuASa: H
2 SO
4 acid soluble
CuCNb: NaCN soluble after acid leach
‑CuResc: Residual copper
The copper deportment as determined by copper-
sequential assay was 2.3% acid soluble copper, 5.7% cya-
nide soluble copper and 92.0% residual copper which often
relates to the presence of refractory chalcopyrite. This is fur-
ther summarized in Table 2.
Inoculum consists of a wild culture of iron and sulfur
oxidizing acidophilic bacteria grown on MKM salts and
ferrous iron. This inoculum is considered as the ideal lix-
iviant for reactor test work. The composition is shown in
Table 3.
Mine raffinate received from the site was used for reac-
tor test work. The raffinate composition is shown in Table 4.
Table 3. Composition of ferrous medium
Species Concentration (g/L)
H
2 SO
4 1
FeSO4·7H2O 15
(NH4)2SO4 0.4
MgSO
4 0.4
K
2 HPO
4 0.1
Table 4. Chemical assays of mine raffinate (g/L)
Al Cu Fe Mg Cl
Raffinate 3.0 0.03 0.3 5.8 5.4
Experimental Procedure
A series of mechanically agitated batch reactors were oper-
ated with 76g of ground ore (P100 0.106 mm), 2.5% pulp
density, ambient temperature, and at pH 2.1. Lixiviants
used were bacterial inoculum, treated raffinate, and treated
raffinate with supplemental iron (2 g/l Fe3+). One control
and one catalyzed reactor were run for each lixiviant. The
tests were agitated at 550 rpm and operated for 76 days.
At designated sampling intervals, measurements of
the solution weight, specific gravity (s.g.), pH, and ORP
were recorded. The leachates were submitted for multi-
element analysis by ICP-AES to determine the chemical
composition.
Upon termination of the tests, the leach slurry was fil-
tered to collect the pregnant leach solution (PLS). The resi-
due was washed with adjusted DI water (pH=2), air-dried,
and submitted for chemical analysis.
RESULTS AND DISCUSSION
Bacterial Sequencing
To investigate the microbial activity in the mine site raf-
finate, a sample of the raffinate, SX treated raffinate, and
inoculum were sent to a third-party lab to conduct bacterial
cell count and 16s RNA sequencing.
The raffinate samples had approximately one order of
magnitude lower cell concentrations than the inoculum.
This is expected because of the 5.4 g/L of Cl present in the
raffinate which is known to harm bacteria. The cell counts
of each lixiviant are summarized in Table 5 and Figure 1.
Due to the limited quantity of bacteria present within
the raffinate sample, the bacterial population was enhanced
by culturing the samples before 16s sequencing.
Examination of the 16s RNA sequencing data allows
for a more thorough understanding of the bacteria consortia
Table 1. Chemical assays of ore sample (%)
Cu Fe
Head 0.08 2.4
Figure 1. Microbial cell count for as-received mine raffinate,
treated mine raffinate and inoculum
Table 5. Results of microbial monitoring
Test ID Cells/mL
Raffinate 6.5E+07
Treated raffinate 6.0E+07
Inoculum 1.3E+08
Table 2. Cu-sequential leach results of ore sample (%)
CuT CuASa CuCNb CuResc
Head
(–¼" crushed)
0.002 0.005 0.081
0.088
Normalized to
head assay
2.27% 5.68% 92.0%
CuT: Total copper measured by the sequential leach analysis
CuASa: H
2 SO
4 acid soluble
CuCNb: NaCN soluble after acid leach
‑CuResc: Residual copper