1788 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
recovery, while 0.1 mM only resulted in 23%. It is worth
noting that the concentration of Cu affects the leaching
kinetics of Au in the system, as previously stated in bench
scale tests.
Figure 10 (b) demonstrates the Cu concentration, with
all conditions reaching 0 within a day, regardless of their
concentrations. The comparatively higher copper levels were
able to reach the initial concentration at a faster rate than
the lower copper levels. Figure 10 (c) and (d) display pH
and thiosulfate changes, respectively. All conditions showed
similar behavior, regardless of their Cu concentrations.
CONCLUSIONS
In our study, the use of unsaturated Mg(OH)2 was used to
restore pH levels in thiosulfate leaching processes following
the evaporation of ammonia. Through bench and column
scale tests, Mg(OH)2 effectively maintained stable pH levels
while improving gold recovery. In bench tests, gold concen-
tration in the solution was increased as Mg(OH)2 increased
up to 0.05 g/g. However, column scale tests showed a
decrease in gold recovery at the higher concentration of
0.05 g/g due to lower copper concentrations. Furthermore,
increasing thiosulfate concentration facilitated gold leach-
ing by promoting copper oxidation, but also resulted in
reduced copper-mediated thiosulfate decomposition and,
consequently, copper precipitation. Future research should
delve into investigating the specific mechanisms and kinet-
ics of these processes.
ACKNOWLEDGMENT
The authors would like to thank Mining3 and Mitacs for
their financial support.
REFERENCES
[1] Donato, D.B., Nichols, O., Possingham, H., Moore,
M., Ricci, P.F., &Noller, B.N. (2007). A critical
review of the effects of gold cyanide-bearing tail-
ings solutions on wildlife. Environment International,
33(7), 974–984. doi: 10.1016/j.envint.2007.04.007.
[2] Marsden, J., &House, I. (2006). The Chemistry of
Gold Extraction. SME.
[3] Yue, C., Sun, H., Liu, W.-J., Guan, B., Deng, X.,
Zhang, X., &Yang, P. (2017). Environmentally
Benign, Rapid, and Selective Extraction of Gold from
Ores and Waste Electronic Materials. Angewandte
Chemie International Edition, 56(32), 9331–9335.
doi: 10.1002/anie.201703412.
Figure 10. Kinetic plots of leaching with several Cu concentrations, a) Au recovery b) Cu concentration, c) pH, and d)
thiosulfate concentration (Test condition: 0.1 M S
2 O
3 2–, 0.5-2 mM Cu, 0.01 g
Mg(OH)2 /g
Ore Mg(OH)
2 ,pH 10.0, 20±3°C)
recovery, while 0.1 mM only resulted in 23%. It is worth
noting that the concentration of Cu affects the leaching
kinetics of Au in the system, as previously stated in bench
scale tests.
Figure 10 (b) demonstrates the Cu concentration, with
all conditions reaching 0 within a day, regardless of their
concentrations. The comparatively higher copper levels were
able to reach the initial concentration at a faster rate than
the lower copper levels. Figure 10 (c) and (d) display pH
and thiosulfate changes, respectively. All conditions showed
similar behavior, regardless of their Cu concentrations.
CONCLUSIONS
In our study, the use of unsaturated Mg(OH)2 was used to
restore pH levels in thiosulfate leaching processes following
the evaporation of ammonia. Through bench and column
scale tests, Mg(OH)2 effectively maintained stable pH levels
while improving gold recovery. In bench tests, gold concen-
tration in the solution was increased as Mg(OH)2 increased
up to 0.05 g/g. However, column scale tests showed a
decrease in gold recovery at the higher concentration of
0.05 g/g due to lower copper concentrations. Furthermore,
increasing thiosulfate concentration facilitated gold leach-
ing by promoting copper oxidation, but also resulted in
reduced copper-mediated thiosulfate decomposition and,
consequently, copper precipitation. Future research should
delve into investigating the specific mechanisms and kinet-
ics of these processes.
ACKNOWLEDGMENT
The authors would like to thank Mining3 and Mitacs for
their financial support.
REFERENCES
[1] Donato, D.B., Nichols, O., Possingham, H., Moore,
M., Ricci, P.F., &Noller, B.N. (2007). A critical
review of the effects of gold cyanide-bearing tail-
ings solutions on wildlife. Environment International,
33(7), 974–984. doi: 10.1016/j.envint.2007.04.007.
[2] Marsden, J., &House, I. (2006). The Chemistry of
Gold Extraction. SME.
[3] Yue, C., Sun, H., Liu, W.-J., Guan, B., Deng, X.,
Zhang, X., &Yang, P. (2017). Environmentally
Benign, Rapid, and Selective Extraction of Gold from
Ores and Waste Electronic Materials. Angewandte
Chemie International Edition, 56(32), 9331–9335.
doi: 10.1002/anie.201703412.
Figure 10. Kinetic plots of leaching with several Cu concentrations, a) Au recovery b) Cu concentration, c) pH, and d)
thiosulfate concentration (Test condition: 0.1 M S
2 O
3 2–, 0.5-2 mM Cu, 0.01 g
Mg(OH)2 /g
Ore Mg(OH)
2 ,pH 10.0, 20±3°C)