XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 693
via sulfur (Gould et al., 2012). It, a hydrophilic species, can
form compounds with metal sulfides such as Fe, Cu etc.
and suppress their flotation (Wang and Forssberg 1996).
Thiocyanate in gold mine effluents up to 1,000 mg/L has
been shown to adversely affect the flotation of gold-bearing
sulfide minerals (Cho et al., 2018).
Managing cyanide tailings in mineral processing is
extremely important given their negative impact on pro-
cess efficiency and environmental concerns. Several physi-
cochemical and biological treatment techniques have been
suggested to remove thiocyanate (Gould et al., 2012).
The most common chemical methods are precipitation,
wet oxidation, and ozone oxidation, and physical meth-
ods involve adsorption, ion exchange, photodegradation,
and membrane extraction (Wang et al., 2022). Chemical
methods are more effective than physical methods, but are
expensive to implement and may require a large amount
of reagents, expensive equipment and specialized materi-
als, and can produce by-products (Watts and Moreau 2016
Wang et al., 2020).
In recent years, electrochemical technologies have been
emerging as new treatment techniques to remove organic
pollutants from water. Within these methods, electrochem-
ical advanced oxidation processes (EAOPs) based on the
electrogeneration of hydroxyl radicals (·OH) to degrade
organic compounds have received great attention (Brillas
and Martínez-Huitle 2015). In this technology, only elec-
trical energy is used for the oxidation of organic pollutants
on high oxidation power anodes, and no chemicals are used
(Comninellis et al., 2008). Xanthate was removed from
flotation process water by EAOPs using an electrochemi-
cal cell containing carbon electrodes as anode and cathode
with a removal efficiency of 95% (Ozturk 2023).
In this study, electrochemical advanced oxidation pro-
cesses were applied to remove thiocyanate from gold mine
process water. An electrochemical cell containing a pair of
carbon electrodes as the anode and cathode was prepared
based on the “flow-by type” CDI cell (Porada et al., 2013).
Carbon electrodes were selected for their advantages of
good stability, high conductivity and porosity (Oren 2008).
They were characterized by scanning electron microscopy
(SEM). The impact of operational parameters, such as
applied voltage and influent concentration, on process
efficiency was investigated to achieve effective thiocyanate
removal. Removal efficiency was evaluated primarily by
salt removal efficiency (SRE%) and total salt removal (SR).
The impact of real mine water constituents on thiocyanate
removal was determined using process water from a gold
mine in Turkey.
MATERIALS AND METHODS
Materials
Powdered activated carbon CEP21K, (PAC, surface area:
2040 m2/g) was obtained from Power Carbon Technology
Co. N,N-Dimethylformamide and Poly (vinylidene fluo-
ride) (PVDF, mw ~534,000 by GPC) were obtained from
Sigma Aldrich. Graphite sheets (0.2 mm thick) were pur-
chased from Mineral Seal Corporation. Ammonium thio-
cyanate (NH4SCN) was obtained from Carlo Erba.
Preparation and Characterization of Electrodes
To fabricate a carbon electrode, activated carbon powder
was added to a 4 wt% PVDF solution dissolved in N,N-
Dimethyl formamide at a total weight ratio of 90:10 (acti-
vated carbon: PVDF). The mixture was stirred for 12 h to
ensure homogeneity. The slurry was then deposited on a
graphite sheet using flow coater (Newport, USA) with a
gap height of 300 μm. After casting, the electrodes were
dried at room temperature.
The surface and cross-sectional morphologies of the
electrodes were characterized by scanning electron micros-
copy (SEM, FEI, Nova NanoSEM). Electrode samples
were coated with a gold layer. The electrodes were frozen in
liquid nitrogen to image cross sections.
Desalination Experiments
An electrochemical cell based on the design of a “flow-by
type” CDI unit cell was used in the experiments (Figure 1a).
The setup contains a feed water container, a peristaltic
pump (Cole Parmer Masterflex LS Easy Load 7518–00,
USA), an electrochemical cell, a potentiostat (Gamry PCI-
4750, Warminster, PA, USA), and ion chromatography
(ICS-3000, Dionex, Sunnyvale, CA, USA). The electro-
chemical cell consisted of a pair of titanium current collec-
tors and a pair of carbon electrodes (Figure 1b). The sizes
of the current collectors and electrodes were 10×50 mm2.
The two sides of the cell were separated by a 1-mm-thick
woven nonconductive nylon spacer. These components are
screwed between a pair of acrylic plates with rubber gaskets.
The effluent samples were collected at various time inter-
vals and thiocyanate concentration was measured using ion
chromatography.
Removal performance was evaluated by total salt
removal (SR, mg/m2) and salt removal efficiency (SRE %).
SR
Q Ci C
A
f
t
e
0 =
-^hdt #
SRE6% C t
C C
100%
i
i f #=
-^hdt
@
#
via sulfur (Gould et al., 2012). It, a hydrophilic species, can
form compounds with metal sulfides such as Fe, Cu etc.
and suppress their flotation (Wang and Forssberg 1996).
Thiocyanate in gold mine effluents up to 1,000 mg/L has
been shown to adversely affect the flotation of gold-bearing
sulfide minerals (Cho et al., 2018).
Managing cyanide tailings in mineral processing is
extremely important given their negative impact on pro-
cess efficiency and environmental concerns. Several physi-
cochemical and biological treatment techniques have been
suggested to remove thiocyanate (Gould et al., 2012).
The most common chemical methods are precipitation,
wet oxidation, and ozone oxidation, and physical meth-
ods involve adsorption, ion exchange, photodegradation,
and membrane extraction (Wang et al., 2022). Chemical
methods are more effective than physical methods, but are
expensive to implement and may require a large amount
of reagents, expensive equipment and specialized materi-
als, and can produce by-products (Watts and Moreau 2016
Wang et al., 2020).
In recent years, electrochemical technologies have been
emerging as new treatment techniques to remove organic
pollutants from water. Within these methods, electrochem-
ical advanced oxidation processes (EAOPs) based on the
electrogeneration of hydroxyl radicals (·OH) to degrade
organic compounds have received great attention (Brillas
and Martínez-Huitle 2015). In this technology, only elec-
trical energy is used for the oxidation of organic pollutants
on high oxidation power anodes, and no chemicals are used
(Comninellis et al., 2008). Xanthate was removed from
flotation process water by EAOPs using an electrochemi-
cal cell containing carbon electrodes as anode and cathode
with a removal efficiency of 95% (Ozturk 2023).
In this study, electrochemical advanced oxidation pro-
cesses were applied to remove thiocyanate from gold mine
process water. An electrochemical cell containing a pair of
carbon electrodes as the anode and cathode was prepared
based on the “flow-by type” CDI cell (Porada et al., 2013).
Carbon electrodes were selected for their advantages of
good stability, high conductivity and porosity (Oren 2008).
They were characterized by scanning electron microscopy
(SEM). The impact of operational parameters, such as
applied voltage and influent concentration, on process
efficiency was investigated to achieve effective thiocyanate
removal. Removal efficiency was evaluated primarily by
salt removal efficiency (SRE%) and total salt removal (SR).
The impact of real mine water constituents on thiocyanate
removal was determined using process water from a gold
mine in Turkey.
MATERIALS AND METHODS
Materials
Powdered activated carbon CEP21K, (PAC, surface area:
2040 m2/g) was obtained from Power Carbon Technology
Co. N,N-Dimethylformamide and Poly (vinylidene fluo-
ride) (PVDF, mw ~534,000 by GPC) were obtained from
Sigma Aldrich. Graphite sheets (0.2 mm thick) were pur-
chased from Mineral Seal Corporation. Ammonium thio-
cyanate (NH4SCN) was obtained from Carlo Erba.
Preparation and Characterization of Electrodes
To fabricate a carbon electrode, activated carbon powder
was added to a 4 wt% PVDF solution dissolved in N,N-
Dimethyl formamide at a total weight ratio of 90:10 (acti-
vated carbon: PVDF). The mixture was stirred for 12 h to
ensure homogeneity. The slurry was then deposited on a
graphite sheet using flow coater (Newport, USA) with a
gap height of 300 μm. After casting, the electrodes were
dried at room temperature.
The surface and cross-sectional morphologies of the
electrodes were characterized by scanning electron micros-
copy (SEM, FEI, Nova NanoSEM). Electrode samples
were coated with a gold layer. The electrodes were frozen in
liquid nitrogen to image cross sections.
Desalination Experiments
An electrochemical cell based on the design of a “flow-by
type” CDI unit cell was used in the experiments (Figure 1a).
The setup contains a feed water container, a peristaltic
pump (Cole Parmer Masterflex LS Easy Load 7518–00,
USA), an electrochemical cell, a potentiostat (Gamry PCI-
4750, Warminster, PA, USA), and ion chromatography
(ICS-3000, Dionex, Sunnyvale, CA, USA). The electro-
chemical cell consisted of a pair of titanium current collec-
tors and a pair of carbon electrodes (Figure 1b). The sizes
of the current collectors and electrodes were 10×50 mm2.
The two sides of the cell were separated by a 1-mm-thick
woven nonconductive nylon spacer. These components are
screwed between a pair of acrylic plates with rubber gaskets.
The effluent samples were collected at various time inter-
vals and thiocyanate concentration was measured using ion
chromatography.
Removal performance was evaluated by total salt
removal (SR, mg/m2) and salt removal efficiency (SRE %).
SR
Q Ci C
A
f
t
e
0 =
-^hdt #
SRE6% C t
C C
100%
i
i f #=
-^hdt
@
#