1912 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
that the increase in the presence of deprotonated alanine
ions during dissolution results in an increase in the gold
dissolution rate. Brown’s (1982) results, to some degree,
align with the outcomes of this study, revealing that depro-
tonated alanine improves gold dissolution compared to a
solution with isoelectric ions.
Proposed Relationship Between Fourier Transform
Infrared, Density Function Theory and Gold
Dissolution
In this investigation of gold-alanine interactions, prelimi-
nary analyses using FTIR and DFT, as well as an assessment
of gold dissolution, were conducted. Notably, in FTIR,
remarkable peak shifts were observed at deprotonation pH
compared to isoelectric pH. Additionally, the complexation
energy between gold and deprotonated alanine exhibited
a more negative value compared to isoelectric pH. Lastly,
gold dissolution at deprotonated pH demonstrated a sig-
nificant increase compared to isoelectric pH.
These findings highlight the potential influence of ala-
nine’s structural form in the gold-alanine complexation
process, particularly in affecting the extent to which alanine
can effectively dissolve gold. Consequently, the deproton-
ated form of alanine was further examined for its efficiency
in leaching gold from gold tailings, as detailed in the fol-
lowing section.
Feasibility Study
Figure 7 shows the 24-hour extraction of leaching gold
from the Witwatersrand tailing (average grade 0.84 g/t)
to assess the feasibility of deprotonated alanine in leaching
gold. The experiments were conducted at room tempera-
ture, maintaining a pH of 12, with a 2 g/L permanganate
oxidant. Various factors were investigated, including pulp
density, deprotonated alanine concentration, copper con-
centration, and tailing pre-treatment with permanganate.
The results revealed gold extractions above 20% across
all tested conditions. Notably, lower pulp densities demon-
strated high gold extractions compared to the correspond-
ing high density. For instance, under conditions of 0.5 M
alanine, 50 g/L pulp density, and 2 g/L permanganate on
pretreated tailings (depicted in Figure 7 as 0.5 M-50 g/L-
24 hr-2 g/L), a significant gold extraction of 92.6% was
achieved.
Furthermore, tailing pre-treatment exhibited a posi-
tive impact, enhancing gold extraction compared to runs
without pre-treatment. Conversely, the influence of glycine
and copper ions within the investigated range appeared
negligible in this study. In summary, the findings revealed
that deprotonated alanine has the potential to dissolve gold
from gold secondary sources, similar to deprotonated gly-
cine, which has demonstrated gold extraction from tailings
(Li et al., 2023). This shows that alanine is a promising
lixiviant for gold leaching.
CONCLUSION
This paper looked at a threefold approach of using FTIR,
DFT and dissolution studies to investigate the use of
alanine (in neutral and deprotonated form) in gold dis-
solution. The investigation on complexation using FTIR
0
0.5
1
1.5
2
0 5 10 15 20 25
Time (h)
deprotonation pH
isoelectric pH
Figure 6. The dissolution profile of gold in alanine at deprotonation and isoelectric pH
Gold
dissolution
(mg/L)
that the increase in the presence of deprotonated alanine
ions during dissolution results in an increase in the gold
dissolution rate. Brown’s (1982) results, to some degree,
align with the outcomes of this study, revealing that depro-
tonated alanine improves gold dissolution compared to a
solution with isoelectric ions.
Proposed Relationship Between Fourier Transform
Infrared, Density Function Theory and Gold
Dissolution
In this investigation of gold-alanine interactions, prelimi-
nary analyses using FTIR and DFT, as well as an assessment
of gold dissolution, were conducted. Notably, in FTIR,
remarkable peak shifts were observed at deprotonation pH
compared to isoelectric pH. Additionally, the complexation
energy between gold and deprotonated alanine exhibited
a more negative value compared to isoelectric pH. Lastly,
gold dissolution at deprotonated pH demonstrated a sig-
nificant increase compared to isoelectric pH.
These findings highlight the potential influence of ala-
nine’s structural form in the gold-alanine complexation
process, particularly in affecting the extent to which alanine
can effectively dissolve gold. Consequently, the deproton-
ated form of alanine was further examined for its efficiency
in leaching gold from gold tailings, as detailed in the fol-
lowing section.
Feasibility Study
Figure 7 shows the 24-hour extraction of leaching gold
from the Witwatersrand tailing (average grade 0.84 g/t)
to assess the feasibility of deprotonated alanine in leaching
gold. The experiments were conducted at room tempera-
ture, maintaining a pH of 12, with a 2 g/L permanganate
oxidant. Various factors were investigated, including pulp
density, deprotonated alanine concentration, copper con-
centration, and tailing pre-treatment with permanganate.
The results revealed gold extractions above 20% across
all tested conditions. Notably, lower pulp densities demon-
strated high gold extractions compared to the correspond-
ing high density. For instance, under conditions of 0.5 M
alanine, 50 g/L pulp density, and 2 g/L permanganate on
pretreated tailings (depicted in Figure 7 as 0.5 M-50 g/L-
24 hr-2 g/L), a significant gold extraction of 92.6% was
achieved.
Furthermore, tailing pre-treatment exhibited a posi-
tive impact, enhancing gold extraction compared to runs
without pre-treatment. Conversely, the influence of glycine
and copper ions within the investigated range appeared
negligible in this study. In summary, the findings revealed
that deprotonated alanine has the potential to dissolve gold
from gold secondary sources, similar to deprotonated gly-
cine, which has demonstrated gold extraction from tailings
(Li et al., 2023). This shows that alanine is a promising
lixiviant for gold leaching.
CONCLUSION
This paper looked at a threefold approach of using FTIR,
DFT and dissolution studies to investigate the use of
alanine (in neutral and deprotonated form) in gold dis-
solution. The investigation on complexation using FTIR
0
0.5
1
1.5
2
0 5 10 15 20 25
Time (h)
deprotonation pH
isoelectric pH
Figure 6. The dissolution profile of gold in alanine at deprotonation and isoelectric pH
Gold
dissolution
(mg/L)