766 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Tests Conducted at Low Current Density and Low
Linear Velocity
Figure 3 (a) and (b) show the gradual decline in thiocyanate
concentration, corresponding increase in free cyanide and
concentration, respectively, observed during the EO test.
As can be seen from Figure 3 (b), the increase in cyanide
concentration in both the actual leach solution and syn-
thetic solution A followed a linear trend with a very similar
slope. The similarity in the rate of free cyanide production
by the EO process between synthetic and actual leach solu-
tion indicates that the parasitic reactions that destroy free
CN and/or reduce anodic current efficiency are proceeding
at the same rate regardless of the initial free cyanide con-
centration. Moreover, the comparisons shown in Figure 3
show that at low current density the rate of SCN oxidation,
CN production and current efficiency were similar with the
synthetic (no initial ammonia) and actual site solutions.
This indicates that ammonia would not affect the overall
process in this case. Figure 3 (a) depicts the measured grad-
ual decline in SCN concentration during the EO tests. It
should be noted that the magnitude of the SCN concentra-
tion drop achieved during the EO tests was only slightly
larger than the absolute error of SCN assays performed on
solutions with high initial levels of SCN of 10 to 15 g/L.
Tests Conducted at High Current Density and High
Linear Velocity
Figure 4 (a) and (b) show the corresponding values observed
for the high current density testing. There are several notice-
able differences between the values and trends captured in
these figures compared to those observed at low current
density (Figure 3 (a), and (b), namely:
Table 1. Feed water chemistry for solutions tested
Constituent Units
CN Recovery Thickener
OF /SART Feed
SART Copper Circuit
Overflow (EO Feed)
Synthetic Solution A
(Vancouver Tap Water, with Salts)
Thiocyanate (d) mg/L 15,500 10,675 ~10,700
Chloride (d) mg/L 947 718 ~720
Sulfate (d) mg/L 5,840 7,638 ~7,650
Ammonia (d) mg/L 256 299 0
Arsenic (d) mg/L 2.16 0.0419 0
Calcium (d) mg/L 1,320 816 0
Iron (d) mg/L 872 913 0
Copper (d) mg/L 400 0.185 0
Sodium (d) mg/L 8,770 9,210 In balance w/ anions
Cyanide free mg/L 487 588 0
pH — 10.59 4.52 4.5
Figure 3. Low Current Density Testing (283 A/m2). Variation of (a) thiocyanate concentration (b) cyanide concentration
Tests Conducted at Low Current Density and Low
Linear Velocity
Figure 3 (a) and (b) show the gradual decline in thiocyanate
concentration, corresponding increase in free cyanide and
concentration, respectively, observed during the EO test.
As can be seen from Figure 3 (b), the increase in cyanide
concentration in both the actual leach solution and syn-
thetic solution A followed a linear trend with a very similar
slope. The similarity in the rate of free cyanide production
by the EO process between synthetic and actual leach solu-
tion indicates that the parasitic reactions that destroy free
CN and/or reduce anodic current efficiency are proceeding
at the same rate regardless of the initial free cyanide con-
centration. Moreover, the comparisons shown in Figure 3
show that at low current density the rate of SCN oxidation,
CN production and current efficiency were similar with the
synthetic (no initial ammonia) and actual site solutions.
This indicates that ammonia would not affect the overall
process in this case. Figure 3 (a) depicts the measured grad-
ual decline in SCN concentration during the EO tests. It
should be noted that the magnitude of the SCN concentra-
tion drop achieved during the EO tests was only slightly
larger than the absolute error of SCN assays performed on
solutions with high initial levels of SCN of 10 to 15 g/L.
Tests Conducted at High Current Density and High
Linear Velocity
Figure 4 (a) and (b) show the corresponding values observed
for the high current density testing. There are several notice-
able differences between the values and trends captured in
these figures compared to those observed at low current
density (Figure 3 (a), and (b), namely:
Table 1. Feed water chemistry for solutions tested
Constituent Units
CN Recovery Thickener
OF /SART Feed
SART Copper Circuit
Overflow (EO Feed)
Synthetic Solution A
(Vancouver Tap Water, with Salts)
Thiocyanate (d) mg/L 15,500 10,675 ~10,700
Chloride (d) mg/L 947 718 ~720
Sulfate (d) mg/L 5,840 7,638 ~7,650
Ammonia (d) mg/L 256 299 0
Arsenic (d) mg/L 2.16 0.0419 0
Calcium (d) mg/L 1,320 816 0
Iron (d) mg/L 872 913 0
Copper (d) mg/L 400 0.185 0
Sodium (d) mg/L 8,770 9,210 In balance w/ anions
Cyanide free mg/L 487 588 0
pH — 10.59 4.52 4.5
Figure 3. Low Current Density Testing (283 A/m2). Variation of (a) thiocyanate concentration (b) cyanide concentration