1791
Thiocyanate Leaching of Gold from Refractory Sulfidic Gold Ore
Pretreated by Roasting
Weiyao Li, Jiajia Wu, Fen Jiao, Wenqing Qin
School of Minerals Processing and Bioengineering, Central South University, Changsha, China
ABSTRACT: Thiocyanate is a promising lixiviant for gold extraction as an alternative to cyanide. A refractory
sulfidic gold ore pretreated by roasting was received for a comprehensive gold extraction study, including
mineralogy analysis, gold deportment study, gold leaching and recovery test. The gold-bearing material after
roasting is highly oxidative, with the dominant mineral phase being iron oxide. Gold and silver grades were
54.03 g/t and 96.50 g/t, respectively, with over 92% of gold presented as native gold. Gold recovery of over
95% was achieved using sodium thiocyanate as a lixiviant, which is comparable to cyanidation and further
enhanced by mechanical activation. Afterward, gold was recovered by zinc precipitation from the leachate.
Detailed experimental design and test results are discussed in the paper.
Keywords: Gold Cyanide-free leaching Mechanical activation Permutation
INTRODUCTION
Gold is one of the most important metals in the social
activities of mankind, not only in the financial market
as an important role in the currency, but also an impor-
tant medium for jewellery and other industries (Zhang,
L., et al., 2023). According to a study by the World Gold
Council in 2023, global gold supply in the first three quar-
ters of 2023 was 3,692.38 t, while the price of gold has
been rising in recent years, with the price of gold reach-
ing as high as 1,928.5 US$/oz in the third quarter of 2023
(USUS, 2023). The special chemical properties of gold
make it impossible to use ordinary chemical reagents in its
extraction. Cyanidation has a long history of application
and wide applicability, and is currently the main method
of gold extraction (Sitando, O., et al., 2020). However,
the toxicity of cyanide is enormous, the lethal dose is very
low, and the continuous harm caused to human beings and
the ecological environment makes it urgent to find a new
method, therefore, the cyanide-free gold extraction is get-
ting more and more attention as never before (Dong, K.,
et al., 2021 Johnson, C. A., 2015 Xu, B., et al., 2016).
Thiourea, thiosulfate, halogen and thiocyanate are known
methods of cyanide-free gold extraction. The thiocyanate
method is more ideal and very promising because of the
high cost of thiourea method and the unstable nature of
thiourea and easy to cause cancer (Zheng, S., et al., 2006)
the thiosulfate method requires the addition of ammonia
in the process of leaching, which is detrimental to the envi-
ronment, and at the same time, the thiosulfate method has
poor applicability (Senanayake, G., 2005 Sitando, O., et
al., 2018 Wang, H., et al, 2020 Wang, J.et al., 2020) the
halogen method is very corrosive to the equipment and is
unstable in nature (Senanayake, G., 2004 Hilson, G. et
al., 2006).
The extraction of gold can reach more than 90% by
conventional leaching, but due to the special properties of
Thiocyanate Leaching of Gold from Refractory Sulfidic Gold Ore
Pretreated by Roasting
Weiyao Li, Jiajia Wu, Fen Jiao, Wenqing Qin
School of Minerals Processing and Bioengineering, Central South University, Changsha, China
ABSTRACT: Thiocyanate is a promising lixiviant for gold extraction as an alternative to cyanide. A refractory
sulfidic gold ore pretreated by roasting was received for a comprehensive gold extraction study, including
mineralogy analysis, gold deportment study, gold leaching and recovery test. The gold-bearing material after
roasting is highly oxidative, with the dominant mineral phase being iron oxide. Gold and silver grades were
54.03 g/t and 96.50 g/t, respectively, with over 92% of gold presented as native gold. Gold recovery of over
95% was achieved using sodium thiocyanate as a lixiviant, which is comparable to cyanidation and further
enhanced by mechanical activation. Afterward, gold was recovered by zinc precipitation from the leachate.
Detailed experimental design and test results are discussed in the paper.
Keywords: Gold Cyanide-free leaching Mechanical activation Permutation
INTRODUCTION
Gold is one of the most important metals in the social
activities of mankind, not only in the financial market
as an important role in the currency, but also an impor-
tant medium for jewellery and other industries (Zhang,
L., et al., 2023). According to a study by the World Gold
Council in 2023, global gold supply in the first three quar-
ters of 2023 was 3,692.38 t, while the price of gold has
been rising in recent years, with the price of gold reach-
ing as high as 1,928.5 US$/oz in the third quarter of 2023
(USUS, 2023). The special chemical properties of gold
make it impossible to use ordinary chemical reagents in its
extraction. Cyanidation has a long history of application
and wide applicability, and is currently the main method
of gold extraction (Sitando, O., et al., 2020). However,
the toxicity of cyanide is enormous, the lethal dose is very
low, and the continuous harm caused to human beings and
the ecological environment makes it urgent to find a new
method, therefore, the cyanide-free gold extraction is get-
ting more and more attention as never before (Dong, K.,
et al., 2021 Johnson, C. A., 2015 Xu, B., et al., 2016).
Thiourea, thiosulfate, halogen and thiocyanate are known
methods of cyanide-free gold extraction. The thiocyanate
method is more ideal and very promising because of the
high cost of thiourea method and the unstable nature of
thiourea and easy to cause cancer (Zheng, S., et al., 2006)
the thiosulfate method requires the addition of ammonia
in the process of leaching, which is detrimental to the envi-
ronment, and at the same time, the thiosulfate method has
poor applicability (Senanayake, G., 2005 Sitando, O., et
al., 2018 Wang, H., et al, 2020 Wang, J.et al., 2020) the
halogen method is very corrosive to the equipment and is
unstable in nature (Senanayake, G., 2004 Hilson, G. et
al., 2006).
The extraction of gold can reach more than 90% by
conventional leaching, but due to the special properties of