1894 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Since arsenic and its oxides are highly volatile, roasting is
the conventional process for arsenic removal. However, due
to the required facilities and toxic emissions, such method
is uneconomical, non-environmental and non-health
friendly.
Hydrometallurgical methods have been investigated
recently and considered as a viable alternative means for
selective removal of arsenic. Among current technolo-
gies, alkaline leaching processes demonstrated successful
results in the removal of arsenic from copper concentrates.
Furthermore, these methods are generally more environ-
mentally benign and less capital intensive (Kobylyanski et
al., 2020).
Selective leaching of arsenic under alkaline leaching has
shown to be an effective method to treat arsenic. Enargite is
considered as a refractory mineral since this cannot be easily
digested in aqueous media (Nazari, et al., 2017). Different
authors have studied the sulfidic leaching of arsenic from
copper concentrates (Parada, et al. 2014 Mitovski et al.
2015 Curreli et al., 2005). Alkaline media currently being
studied are Na2S NaHS and NaClO.
Both Na2S and NaHS have similar leaching behavior
which can be summarized in Eq 1 and Eq 2. As shown in
the reactions, arsenic is leached in the form of AsS43– while
copper will remain in residue as Cu2S.
3 2Cu 2AsS Cu AsS S S
3 4
2-
2 4
3-
s )++
^^aq ^sh h h
(1
S H O HS OH 2-
2 )++--(2)
NaClO leaching is described in Eq 3. Arsenic is
reported to be released from enargite forming sodium arse-
nate, AsO43–, while copper will be oxidized and form teno-
rite (CuO). Hypochlorite forms at pH 8 and above and
would be the dominant species in the system.
2 22 35NaClO
6 11H
Cu3 AsS NaOH
CuO O
4
2 s
)++
++
^sh
^^aqh
^aqh
h
2Na 8 35NaCl AsO Na SO
3 4 2 4 aqh ++
^^aqh ^aqh (3)
This study aims to investigate the selective removal of
arsenic from an enargite-scorodite ore using sodium hypo-
chlorite under alkaline conditions.
METHODOLOGY
Materials
High-As ore samples were collected to carry out the experi-
mental work. The ore underwent crushing and grinding to
obtain samples with 80% passing (P80 )of 37 and 75 µm.
Reagents for leaching were prepared from technical-grade
reagents (NaClO and NaOH) using deionized water for
mixing and dilution.
Ore Characterization
Determination of element composition was done using the
Inductively Coupled Plasma (ICP). Mineralogical and par-
ticle size analysis was obtained using the Mineral Liberation
Analyzer from the Julius Kruttschnitt Mineral Research
Centre (JKMRC) of the University of Queensland.
NaClO-NaOH Leaching
Leaching of the ore was performed under alkaline condi-
tions using NaClO. To maintain the alkalinity of the sys-
tem, NaOH was added. Furthermore, as reference, a blank
setup was also conducted -without the addition of any sol-
vent at the same alkalinity.
Leaching media was prepared by initially creating an
alkaline solution through the addition of NaOH followed
by the addition of the solvent. Once desired temperature
was reached, the ore sample was then added to the solution.
Leaching conditions such as pH, NaOH concentration,
time, percent solids and agitation rate were set constant.
Leaching tests were carried out in a 500 mL two-necked
flasks with Liebig condenser in a temperature-controlled
oil bath. The leaching solution was filtered to separate the
leached residue and pregnant solution. The arsenic concen-
tration of the pregnant solution was determined.
Kinetic Study
Leaching tests were carried out in a 400 mL leaching solu-
tion at 0.60M NaClO, 37µm P80 and at three different
temperatures. Aliquot solution was collected for character-
ization at predetermined time interval.
RESULTS AND DISCUSSION
Ore Characterization
The elemental composition of the ore is shown in Table 1
which indicate significant amounts of copper, as well as
arsenic. Based on the Mineral Liberation Analyzer data,
arsenic occurs as 4% enargite (Cu3AsS4) and 1% scorodite
(FeAsO4.2H2O). Furthermore, the ore is also comprised of
9% pyrite, 0.12% copper minerals and dominated by
quartz as the gangue mineral at 83% SiO2.
Table 1. Main elemental composition of the ore
Element %As %Cu ppm Au %Fe
Composition 1.06 1.93 3.8 4.97
Since arsenic and its oxides are highly volatile, roasting is
the conventional process for arsenic removal. However, due
to the required facilities and toxic emissions, such method
is uneconomical, non-environmental and non-health
friendly.
Hydrometallurgical methods have been investigated
recently and considered as a viable alternative means for
selective removal of arsenic. Among current technolo-
gies, alkaline leaching processes demonstrated successful
results in the removal of arsenic from copper concentrates.
Furthermore, these methods are generally more environ-
mentally benign and less capital intensive (Kobylyanski et
al., 2020).
Selective leaching of arsenic under alkaline leaching has
shown to be an effective method to treat arsenic. Enargite is
considered as a refractory mineral since this cannot be easily
digested in aqueous media (Nazari, et al., 2017). Different
authors have studied the sulfidic leaching of arsenic from
copper concentrates (Parada, et al. 2014 Mitovski et al.
2015 Curreli et al., 2005). Alkaline media currently being
studied are Na2S NaHS and NaClO.
Both Na2S and NaHS have similar leaching behavior
which can be summarized in Eq 1 and Eq 2. As shown in
the reactions, arsenic is leached in the form of AsS43– while
copper will remain in residue as Cu2S.
3 2Cu 2AsS Cu AsS S S
3 4
2-
2 4
3-
s )++
^^aq ^sh h h
(1
S H O HS OH 2-
2 )++--(2)
NaClO leaching is described in Eq 3. Arsenic is
reported to be released from enargite forming sodium arse-
nate, AsO43–, while copper will be oxidized and form teno-
rite (CuO). Hypochlorite forms at pH 8 and above and
would be the dominant species in the system.
2 22 35NaClO
6 11H
Cu3 AsS NaOH
CuO O
4
2 s
)++
++
^sh
^^aqh
^aqh
h
2Na 8 35NaCl AsO Na SO
3 4 2 4 aqh ++
^^aqh ^aqh (3)
This study aims to investigate the selective removal of
arsenic from an enargite-scorodite ore using sodium hypo-
chlorite under alkaline conditions.
METHODOLOGY
Materials
High-As ore samples were collected to carry out the experi-
mental work. The ore underwent crushing and grinding to
obtain samples with 80% passing (P80 )of 37 and 75 µm.
Reagents for leaching were prepared from technical-grade
reagents (NaClO and NaOH) using deionized water for
mixing and dilution.
Ore Characterization
Determination of element composition was done using the
Inductively Coupled Plasma (ICP). Mineralogical and par-
ticle size analysis was obtained using the Mineral Liberation
Analyzer from the Julius Kruttschnitt Mineral Research
Centre (JKMRC) of the University of Queensland.
NaClO-NaOH Leaching
Leaching of the ore was performed under alkaline condi-
tions using NaClO. To maintain the alkalinity of the sys-
tem, NaOH was added. Furthermore, as reference, a blank
setup was also conducted -without the addition of any sol-
vent at the same alkalinity.
Leaching media was prepared by initially creating an
alkaline solution through the addition of NaOH followed
by the addition of the solvent. Once desired temperature
was reached, the ore sample was then added to the solution.
Leaching conditions such as pH, NaOH concentration,
time, percent solids and agitation rate were set constant.
Leaching tests were carried out in a 500 mL two-necked
flasks with Liebig condenser in a temperature-controlled
oil bath. The leaching solution was filtered to separate the
leached residue and pregnant solution. The arsenic concen-
tration of the pregnant solution was determined.
Kinetic Study
Leaching tests were carried out in a 400 mL leaching solu-
tion at 0.60M NaClO, 37µm P80 and at three different
temperatures. Aliquot solution was collected for character-
ization at predetermined time interval.
RESULTS AND DISCUSSION
Ore Characterization
The elemental composition of the ore is shown in Table 1
which indicate significant amounts of copper, as well as
arsenic. Based on the Mineral Liberation Analyzer data,
arsenic occurs as 4% enargite (Cu3AsS4) and 1% scorodite
(FeAsO4.2H2O). Furthermore, the ore is also comprised of
9% pyrite, 0.12% copper minerals and dominated by
quartz as the gangue mineral at 83% SiO2.
Table 1. Main elemental composition of the ore
Element %As %Cu ppm Au %Fe
Composition 1.06 1.93 3.8 4.97