XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 695
thiocyanate at varying time intervals for 120 minutes. Ion
chromatography (ICS3000, Dionex, Sunnyvale, CA, USA)
and ICP-OES (Iris Intrepid, Thermo Elemental, Franklin,
MA, USA) were used for the determination of anions and
cations, respectively.
RESULTS AND DISCUSSION
Characterization of Electrodes
The weight of the 10×50 mm2 electrode was 13.1 mg,
including the PVDF but not the graphite sheet. The top
view of the SEM image illustrated in Figure 2 showed that
the electrode surface was uniform and consisted of grains of
different sizes. Casting carbon slurry on the graphite paper
resulted in a layer approximately 370 μm thick.
Desalination Experiments
The objective of this research was to remove thiocyanate
from the gold mining process water by electrochemical
advanced oxidation processes. The process is based on the
oxidation of pollutants in an electrolytic cell by chemi-
cal reaction with the electro-generated hydroxyl radicals
(•OH) on the anode surface (Martinez-Huitle and Brillas
2009). The thiocyanate ion can undergo three different oxi-
dation reactions and is always oxidized to sulfate (Gauguin
1951 1949).
SCN– +4H2O ↔ SO42– +CN– +8H+ +6e–
SCN– +7H2O ↔ SO42– +CNO– +10H+ +8e–
SCN– +7H2O ↔ NH3+ +CO32– +SO42– +11H+ +8e–
Batch Experiments
Batch recirculation experiments of 160 mg/L thiocyanate
solution with a volume of 25 mL were conducted at a con-
stant flow rate of 1.5 mL/min at an operating voltages of
5.0 V for 180 minutes. According to the results shown in
Figure 3, the thiocyanate was oxidized to sulfate during the
process. Concentration of SCN– decreased from 160 mg/L
to 3 mg/L within 180 minutes, while the sulfate concentra-
tion increased to 120 mg/L.
Effect of Applied Voltage
The effect of applied voltage on thiocyanate removal from
5 mg/L thiocyanate solution at a constant flow rate of 1.5
mL/min and various operating voltages ranging from 1 to
5 V was investigated.
According to the results presented in Figure 4a, the con-
centration of thiocyanate decreased from 5 mg/L to about
3 mg/L during 180 minutes of operation at an applied
potential of 1 V. At 3 V, it was reduced to 0.07 mg/L in
15 minutes and remained relatively stable for 90 minutes,
then the removal efficiency decreased and the concentra-
tion of thiocyanate increased to 1.59 mg/L at the end of
180 minutes of operation. At 5 V, the thiocyanate concen-
tration decreased to 0.79 ppm and remained constant at
around 1 mg/L throughout the 180 minutes of treatment.
The results shown in Figure 4 b, c and d indicated that the
amount of generated sulfate increased with the increasing
potential and was more significant at 5 V.
Desalination performance was evaluated by the total
thiocyanate removal and salt removal efficiency %.
Figure 2. SEM images of the surface (a) and cross-section (b) of the carbon electrode
thiocyanate at varying time intervals for 120 minutes. Ion
chromatography (ICS3000, Dionex, Sunnyvale, CA, USA)
and ICP-OES (Iris Intrepid, Thermo Elemental, Franklin,
MA, USA) were used for the determination of anions and
cations, respectively.
RESULTS AND DISCUSSION
Characterization of Electrodes
The weight of the 10×50 mm2 electrode was 13.1 mg,
including the PVDF but not the graphite sheet. The top
view of the SEM image illustrated in Figure 2 showed that
the electrode surface was uniform and consisted of grains of
different sizes. Casting carbon slurry on the graphite paper
resulted in a layer approximately 370 μm thick.
Desalination Experiments
The objective of this research was to remove thiocyanate
from the gold mining process water by electrochemical
advanced oxidation processes. The process is based on the
oxidation of pollutants in an electrolytic cell by chemi-
cal reaction with the electro-generated hydroxyl radicals
(•OH) on the anode surface (Martinez-Huitle and Brillas
2009). The thiocyanate ion can undergo three different oxi-
dation reactions and is always oxidized to sulfate (Gauguin
1951 1949).
SCN– +4H2O ↔ SO42– +CN– +8H+ +6e–
SCN– +7H2O ↔ SO42– +CNO– +10H+ +8e–
SCN– +7H2O ↔ NH3+ +CO32– +SO42– +11H+ +8e–
Batch Experiments
Batch recirculation experiments of 160 mg/L thiocyanate
solution with a volume of 25 mL were conducted at a con-
stant flow rate of 1.5 mL/min at an operating voltages of
5.0 V for 180 minutes. According to the results shown in
Figure 3, the thiocyanate was oxidized to sulfate during the
process. Concentration of SCN– decreased from 160 mg/L
to 3 mg/L within 180 minutes, while the sulfate concentra-
tion increased to 120 mg/L.
Effect of Applied Voltage
The effect of applied voltage on thiocyanate removal from
5 mg/L thiocyanate solution at a constant flow rate of 1.5
mL/min and various operating voltages ranging from 1 to
5 V was investigated.
According to the results presented in Figure 4a, the con-
centration of thiocyanate decreased from 5 mg/L to about
3 mg/L during 180 minutes of operation at an applied
potential of 1 V. At 3 V, it was reduced to 0.07 mg/L in
15 minutes and remained relatively stable for 90 minutes,
then the removal efficiency decreased and the concentra-
tion of thiocyanate increased to 1.59 mg/L at the end of
180 minutes of operation. At 5 V, the thiocyanate concen-
tration decreased to 0.79 ppm and remained constant at
around 1 mg/L throughout the 180 minutes of treatment.
The results shown in Figure 4 b, c and d indicated that the
amount of generated sulfate increased with the increasing
potential and was more significant at 5 V.
Desalination performance was evaluated by the total
thiocyanate removal and salt removal efficiency %.
Figure 2. SEM images of the surface (a) and cross-section (b) of the carbon electrode