XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1907
HIGHLIGHTS
• FTIR predicts the bonding of alanine and gold using
an experimental technique.
• DFT calculations provide insights into the compu-
tational quantum mechanical modelling of gold and
alanine.
• FTIR and DFT were conducted at isoelectric and
deprotonation pH of alanine.
• High dissolution of gold was observed with deprot-
onated alanine compared to neutral alanine.
• Alanine demonstrates the potential for leaching gold
from tailings.
INTRODUCTION
Over the past century, the cyanide system has been the
most investigated and utilized in processing gold ores and
concentrates. Its enduring popularity in gold processing has
been attributed to its unique complexation properties with
gold (Fleming 1992 Pradhan et al.,2020 Aylmore 2005
Hilson &Monhemius 2006 Stange 1999). However,
development in environmentally sustainable processing of
gold has led to an alternative investigation into other prom-
ising lixiviants. Different lixiviants have been proposed and
tested, revealing both advantages and disadvantages of gold
leaching (Aylmore 2005, 2016 Hilson &Monhemius
2006). One promising lixiviant that has been patented in
2014 (Eksteen &Oraby 2014) is the amino acid due to its
unique advantages. These advantages include being envi-
ronmentally benign, easy to recover and reuse, high ther-
mal stability, non-volatility, being able to be biologically
destroyed, onsite producibility, and low cost of operations
(Eksteen &Oraby 2015 Eksteen &Oraby, 2014 Oraby &
Eksteen 2015a 2015b)
Amino acids are building blocks of all living organisms
characterized by an amine end, a carboxylic end, and an R
end. The R group in these molecules determines its chemi-
cal reactivity due to its stability and its nature to accept
or donate electrons (Damodaran 2017 Hughes 2012). The
most common amino acids are the first 20 amino acids
containing an alpha carbon, a carbon atom connected to
the amine group and carboxylic group (Asif et al., 2011
Damodaran 2017 Hughes, 2012 Violi et al., 2020), as
shown in Figure 1. The amine group and carboxylic part
can lose and gain the H+ ion to form either a cation, zwit-
terion or anion depending on the pH, as shown in Figure 2
(Damodaran 2017). Furthermore, apart from being the
building blocks of all living organisms, amino acids have
found application in the extractive metallurgy of gold
(Altinkaya et al., 2020 Eksteen et al., 2018 Eksteen &
Oraby, 2014 Jamett, 2023 Oraby et al., 2020).
Figure 1. Typical amino acid structure showing the alpha
drawn carbon and modified using ChemCraft (Zhurko
2005)
Figure 2. pH dependency of amino acids re-drawn using Chemcraft (Damodaran 2017)
HIGHLIGHTS
• FTIR predicts the bonding of alanine and gold using
an experimental technique.
• DFT calculations provide insights into the compu-
tational quantum mechanical modelling of gold and
alanine.
• FTIR and DFT were conducted at isoelectric and
deprotonation pH of alanine.
• High dissolution of gold was observed with deprot-
onated alanine compared to neutral alanine.
• Alanine demonstrates the potential for leaching gold
from tailings.
INTRODUCTION
Over the past century, the cyanide system has been the
most investigated and utilized in processing gold ores and
concentrates. Its enduring popularity in gold processing has
been attributed to its unique complexation properties with
gold (Fleming 1992 Pradhan et al.,2020 Aylmore 2005
Hilson &Monhemius 2006 Stange 1999). However,
development in environmentally sustainable processing of
gold has led to an alternative investigation into other prom-
ising lixiviants. Different lixiviants have been proposed and
tested, revealing both advantages and disadvantages of gold
leaching (Aylmore 2005, 2016 Hilson &Monhemius
2006). One promising lixiviant that has been patented in
2014 (Eksteen &Oraby 2014) is the amino acid due to its
unique advantages. These advantages include being envi-
ronmentally benign, easy to recover and reuse, high ther-
mal stability, non-volatility, being able to be biologically
destroyed, onsite producibility, and low cost of operations
(Eksteen &Oraby 2015 Eksteen &Oraby, 2014 Oraby &
Eksteen 2015a 2015b)
Amino acids are building blocks of all living organisms
characterized by an amine end, a carboxylic end, and an R
end. The R group in these molecules determines its chemi-
cal reactivity due to its stability and its nature to accept
or donate electrons (Damodaran 2017 Hughes 2012). The
most common amino acids are the first 20 amino acids
containing an alpha carbon, a carbon atom connected to
the amine group and carboxylic group (Asif et al., 2011
Damodaran 2017 Hughes, 2012 Violi et al., 2020), as
shown in Figure 1. The amine group and carboxylic part
can lose and gain the H+ ion to form either a cation, zwit-
terion or anion depending on the pH, as shown in Figure 2
(Damodaran 2017). Furthermore, apart from being the
building blocks of all living organisms, amino acids have
found application in the extractive metallurgy of gold
(Altinkaya et al., 2020 Eksteen et al., 2018 Eksteen &
Oraby, 2014 Jamett, 2023 Oraby et al., 2020).
Figure 1. Typical amino acid structure showing the alpha
drawn carbon and modified using ChemCraft (Zhurko
2005)
Figure 2. pH dependency of amino acids re-drawn using Chemcraft (Damodaran 2017)