258
J. Kim et al.
Fig. 5 Effect of pulp density
on the leaching of metals
from ZPR using 2.0 M at
25 °C for 30 min
0
20
40
60
80
100
0%
5%
10%
15%
20%
25%
Leaching efficiency (%)
Pulp density (%)
Pb
Zn
Ag
of Pb decreased drastically, that is from 82.6 to 11.3% with the increase in the
pulp density (PD) from 5 to 20%. The increase in pulp density from 5 to 20% has
affected the leaching efficiency of Zn to a lesser extent, which dropped from 57.3
to 49.5%. With the purpose of further investigating the extraction of ZPR in the
second step leaching, 10% pulp density was selected as the optimum value in the
first step leaching, since Zn dissolution remained the same as that of 5% PD, with
some compromise in the leaching of Pb.
Second Step Leaching
After the optimum conditions in the first step leaching, further experiments were
performed under the conditions such as 2.0 M NaOH concentration, 25 °C temperature, and 10% of pulp density for 30 min of leaching time. In these conditions, the
extraction of metals was found to be 41.1% Pb, 58% Zn, and 0.0% Ag. The purpose
of the second step leaching was to increase the overall lead recovery as well as the
enrichment of Ag in the leach residue. Table 2 shows the leaching efficiency of Pb,
Zn, and other metals with 2.0 M NaOH solution in the first step and variation of
NaOH concentrations in the second step.
When the residue from the first leaching step (under the stipulated conditions)
was subjected to the second step of leaching using different concentrations of NaOH,
the leaching efficiency of Pb improved significantly. Thus, lead dissolution increased
from 28.1 to 60.6% with increase in the NaOH concentration from 1.0 to 4.0 M. Total
leaching efficiency of Pb could reach ~100% after the leaching with 2.0 M NaOH
in the first step (39.5%) and 3.0 M NaOH in the second step (60.6%). Moreover,
two-step leaching with 3.0 and 4.0 M NaOH concentration in the first step followed
by the second step leaching with 3.0 and 2.0 M NaOH was also carried out.
Notwithstanding the leaching behavior of lead, NaOH leaching in the second step
did not have a strong effect on the extraction of Zn. With the increase in the NaOH
concentration from 1.0 to 4.0 M, leaching efficiency of Zn just increased in the range
J. Kim et al.
Fig. 5 Effect of pulp density
on the leaching of metals
from ZPR using 2.0 M at
25 °C for 30 min
0
20
40
60
80
100
0%
5%
10%
15%
20%
25%
Leaching efficiency (%)
Pulp density (%)
Pb
Zn
Ag
of Pb decreased drastically, that is from 82.6 to 11.3% with the increase in the
pulp density (PD) from 5 to 20%. The increase in pulp density from 5 to 20% has
affected the leaching efficiency of Zn to a lesser extent, which dropped from 57.3
to 49.5%. With the purpose of further investigating the extraction of ZPR in the
second step leaching, 10% pulp density was selected as the optimum value in the
first step leaching, since Zn dissolution remained the same as that of 5% PD, with
some compromise in the leaching of Pb.
Second Step Leaching
After the optimum conditions in the first step leaching, further experiments were
performed under the conditions such as 2.0 M NaOH concentration, 25 °C temperature, and 10% of pulp density for 30 min of leaching time. In these conditions, the
extraction of metals was found to be 41.1% Pb, 58% Zn, and 0.0% Ag. The purpose
of the second step leaching was to increase the overall lead recovery as well as the
enrichment of Ag in the leach residue. Table 2 shows the leaching efficiency of Pb,
Zn, and other metals with 2.0 M NaOH solution in the first step and variation of
NaOH concentrations in the second step.
When the residue from the first leaching step (under the stipulated conditions)
was subjected to the second step of leaching using different concentrations of NaOH,
the leaching efficiency of Pb improved significantly. Thus, lead dissolution increased
from 28.1 to 60.6% with increase in the NaOH concentration from 1.0 to 4.0 M. Total
leaching efficiency of Pb could reach ~100% after the leaching with 2.0 M NaOH
in the first step (39.5%) and 3.0 M NaOH in the second step (60.6%). Moreover,
two-step leaching with 3.0 and 4.0 M NaOH concentration in the first step followed
by the second step leaching with 3.0 and 2.0 M NaOH was also carried out.
Notwithstanding the leaching behavior of lead, NaOH leaching in the second step
did not have a strong effect on the extraction of Zn. With the increase in the NaOH
concentration from 1.0 to 4.0 M, leaching efficiency of Zn just increased in the range