XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1795
the gold was hardly changed, so the optimal dosage of
MnO2 was 4.0 mmol/L. Furthermore, when pH=1.0, the
overall increase of gold extraction was more obvious. The
optimum dosage of MnO2 was 4.0 mmol/L. In addition,
the highest extraction of gold was observed at pH=1.0,
but at pH=2.0, the extraction of gold only decreased from
96.13% to 95.48%, therefore, the optimum pH for leach-
ing in this experiment was 2.0.
The liquid-solid ratio has a small effect on the gold
extraction, to improve the processing capacity as much as
possible, so, 3:1 mL/g was selected as the optimal liquid-
solid ratio condition. In the process of increasing the leach-
ing time from 3 h to 6 h, the gold extraction increased
about 3.92%, and the gold extraction did not change when
the leaching time was increased after 6 h. Therefore, the
optimal leaching time was chosen as 6 h.
According to the results of the condition test, the opti-
mal conditions for mechanical activation-enhanced leach-
ing were: 1.2 mol/L NaSCN, 4.0 mmol/L MnO2, pH=2.0,
liquid-solid ratio of 3:1 mL/g, leaching time of 6 h, ball
milling tank rotational rate of 150 rpm, and ball milling
tank autorotation rate of 300 rpm, room temperature.
Under the optimal conditions, the extraction of gold was
98.61% and that of silver was 87.74%, and the leaching
effect of gold and silver was very satisfactory. The enhanced
leaching by mechanical activation has no significant effect
on the silver extraction, but the enhancement of the gold
extraction is very significant.
Gold and Silver Recovery Test
Gold and silver in the leach solution were recovered by
the replacement precipitation method, and the condi-
tions for the recovery of gold and silver by the replacement
precipitation method were systematically investigated in
this section. zinc powder was selected as the replacement
agent, and the replacement test was carried out according
to the following conditions, unless otherwise stated: 1.0
g/L zinc powder, temperature 25 °C, 1.2 mol/L NaSCN,
replacement time of 10 min, and stirring rate of 300 rpm.
various conditions. recovery of gold and silver are shown in
Table 5.
According to the results shown in Table 5, the zinc
powder concentration and reaction temperature had the
greatest effect on gold and silver recovery, and the recovery
of gold and silver increased from 90.38% and 49.59% to
95.87% and 87.02% when the zinc powder concentration
was increased from 0.5 g/L to 1.0 g/L. Further increase in
the zinc powder concentration resulted in less change in
the recovery of gold and silver, so 1.0 g/L was selected as
the optimum zinc powder concentration. Since the higher
the reaction temperature, the easier the zinc powder was
oxidized and failed, the recoveries of gold and silver gradu-
ally decreased with the increase of the reaction tempera-
ture, and the recoveries of gold and silver had decreased to
74.71% and 63.28% at the reaction temperature of 85 °C,
therefore, 25 °C was selected as the optimum temperature
for the reaction.
The concentration of residual thiocyanate in the leach
solution, as well as the reaction time and stirring rate had
little effect on the recovery of gold and silver, and the recov-
eries of gold and silver were almost unchanged at differ-
ent concentrations of thiocyanate similarly, the recoveries
of gold and silver were basically unchanged by increasing
the reaction time and stirring rate, so, considering the
results, the optimum concentration of thiocyanate in the
leach solution and the optimum reaction time and stirring
rate in the gold and silver replacement process were cho-
sen to be 0.70 mol/L for 10 min and 300 rpm. Therefore,
0.70 mol/L, 10 min and 300 rpm were selected as the opti-
mal thiocyanate concentration, reaction time and stirring
rate for the gold and silver replacement process.
Therefore, the optimum conditions for the recovery
of gold and silver were determined based on the condi-
tion test study as 1.0 g/L zinc powder, temperature 25 °C,
1.2 mol/L NaSCN, replacement time 10 min, and stirring
rate 300 rpm. The recoveries of gold and silver under the
optimum conditions were 96.21% and 90.46%, and the
recoveries of gold and silver were high.
CONCLUSIONS
In this paper, we systematically investigated the efficient
recovery of gold and silver from gold-rich roasting slag
by thiocyanate leaching-replacement precipitation, and
Table 4. Mechanical activation enhanced leaching test results
Conditions Gold Extraction, %
NaSCN, mol/L 0.6 92.59
1.2 96.13
1.8 95.84
MnO
2 ,mmol/L 2.0 95.17
4.0 96.13
6.0 95.86
pH 1.0 96.13
2.0 95.48
3.0 91.41
Liquid-solid ratio,
mL/g
3 95.35
6 96.41
9 96.71
Leaching time, h 3 92.21
6 96.13
9 96.09
the gold was hardly changed, so the optimal dosage of
MnO2 was 4.0 mmol/L. Furthermore, when pH=1.0, the
overall increase of gold extraction was more obvious. The
optimum dosage of MnO2 was 4.0 mmol/L. In addition,
the highest extraction of gold was observed at pH=1.0,
but at pH=2.0, the extraction of gold only decreased from
96.13% to 95.48%, therefore, the optimum pH for leach-
ing in this experiment was 2.0.
The liquid-solid ratio has a small effect on the gold
extraction, to improve the processing capacity as much as
possible, so, 3:1 mL/g was selected as the optimal liquid-
solid ratio condition. In the process of increasing the leach-
ing time from 3 h to 6 h, the gold extraction increased
about 3.92%, and the gold extraction did not change when
the leaching time was increased after 6 h. Therefore, the
optimal leaching time was chosen as 6 h.
According to the results of the condition test, the opti-
mal conditions for mechanical activation-enhanced leach-
ing were: 1.2 mol/L NaSCN, 4.0 mmol/L MnO2, pH=2.0,
liquid-solid ratio of 3:1 mL/g, leaching time of 6 h, ball
milling tank rotational rate of 150 rpm, and ball milling
tank autorotation rate of 300 rpm, room temperature.
Under the optimal conditions, the extraction of gold was
98.61% and that of silver was 87.74%, and the leaching
effect of gold and silver was very satisfactory. The enhanced
leaching by mechanical activation has no significant effect
on the silver extraction, but the enhancement of the gold
extraction is very significant.
Gold and Silver Recovery Test
Gold and silver in the leach solution were recovered by
the replacement precipitation method, and the condi-
tions for the recovery of gold and silver by the replacement
precipitation method were systematically investigated in
this section. zinc powder was selected as the replacement
agent, and the replacement test was carried out according
to the following conditions, unless otherwise stated: 1.0
g/L zinc powder, temperature 25 °C, 1.2 mol/L NaSCN,
replacement time of 10 min, and stirring rate of 300 rpm.
various conditions. recovery of gold and silver are shown in
Table 5.
According to the results shown in Table 5, the zinc
powder concentration and reaction temperature had the
greatest effect on gold and silver recovery, and the recovery
of gold and silver increased from 90.38% and 49.59% to
95.87% and 87.02% when the zinc powder concentration
was increased from 0.5 g/L to 1.0 g/L. Further increase in
the zinc powder concentration resulted in less change in
the recovery of gold and silver, so 1.0 g/L was selected as
the optimum zinc powder concentration. Since the higher
the reaction temperature, the easier the zinc powder was
oxidized and failed, the recoveries of gold and silver gradu-
ally decreased with the increase of the reaction tempera-
ture, and the recoveries of gold and silver had decreased to
74.71% and 63.28% at the reaction temperature of 85 °C,
therefore, 25 °C was selected as the optimum temperature
for the reaction.
The concentration of residual thiocyanate in the leach
solution, as well as the reaction time and stirring rate had
little effect on the recovery of gold and silver, and the recov-
eries of gold and silver were almost unchanged at differ-
ent concentrations of thiocyanate similarly, the recoveries
of gold and silver were basically unchanged by increasing
the reaction time and stirring rate, so, considering the
results, the optimum concentration of thiocyanate in the
leach solution and the optimum reaction time and stirring
rate in the gold and silver replacement process were cho-
sen to be 0.70 mol/L for 10 min and 300 rpm. Therefore,
0.70 mol/L, 10 min and 300 rpm were selected as the opti-
mal thiocyanate concentration, reaction time and stirring
rate for the gold and silver replacement process.
Therefore, the optimum conditions for the recovery
of gold and silver were determined based on the condi-
tion test study as 1.0 g/L zinc powder, temperature 25 °C,
1.2 mol/L NaSCN, replacement time 10 min, and stirring
rate 300 rpm. The recoveries of gold and silver under the
optimum conditions were 96.21% and 90.46%, and the
recoveries of gold and silver were high.
CONCLUSIONS
In this paper, we systematically investigated the efficient
recovery of gold and silver from gold-rich roasting slag
by thiocyanate leaching-replacement precipitation, and
Table 4. Mechanical activation enhanced leaching test results
Conditions Gold Extraction, %
NaSCN, mol/L 0.6 92.59
1.2 96.13
1.8 95.84
MnO
2 ,mmol/L 2.0 95.17
4.0 96.13
6.0 95.86
pH 1.0 96.13
2.0 95.48
3.0 91.41
Liquid-solid ratio,
mL/g
3 95.35
6 96.41
9 96.71
Leaching time, h 3 92.21
6 96.13
9 96.09