768 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
of the overall cell operating voltage caused by the electric
resistance of electrolyte (i.e., IR drop) was calculated from
the solution conductivity, distance between electrodes in
the EMEW cell, and applied current. The solid horizontal
lines shown in Figure 5 (c) represent the calculated IR drop,
where the IR drop for solution E was approximately 2V for
Solution E versus 5 V for Solution B. This demonstrates
the importance of optimizing the electrode gap on capital
and operating cost of the full scale EO circuit based on
the solution chemistry. Further, when the IR drop is sub-
tracted from the total cell operating voltage, the remainder
which represents the difference between electrode operat-
ing potentials, while Solution E starts out comparatively
higher, after 20 minutes both solutions are similar. This
indicates that reactions taking place on the cell electrodes
and the associated overpotentials are the same.
Initial Cyanide Concentration. Figure 6 shows simi-
lar kinetics of thiocyanate consumption and associated pro-
duction of NaCN. This indicates that the presence of CN
has no effect on the overall kinetics of SCN oxidation.
Initial Chloride Concentration. Figure 7 (a) shows
that thiocyanate consumption is independent of chloride
presence. For cyanide production (Figure 7 (b)), during
the first 13 minutes of operation, the rise in free cyanide
concentration seems unaffected by the chloride presence,
however, as the test proceeded the rate of cyanide produc-
tion decreased. To assess OCN formation, the test in the
presence of chloride was extended to 60 minutes and cya-
nate concentration was checked to determine if the rate of
free cyanide production continued to decrease further. The
results indicate a reduction in cyanide production as well as
a reversal in cyanide concentration. Specifically, between 35
to 60 minutes, cyanide concentration in solution dropped
by half to 100 mg/L, and the cyanate analysis at 60 min
showed that 58% of CN produced since the start of the
test was lost to OCN. The comparison of results shown in
Figure 1 (b) and Figure 7 (b) shows that the formation of
chlorine was likely due to the high current density paired
with low initial thiocyanate concentration. This leads to
the conclusion that, in the presence of chloride and at low
Figure 5. Variation of (a) thiocyanate concentration (b) cyanide concentration and (c) cell voltage over the test course under
different initial thiocyanate concentration. Conditions: 943 A/m2, 663 m/h
of the overall cell operating voltage caused by the electric
resistance of electrolyte (i.e., IR drop) was calculated from
the solution conductivity, distance between electrodes in
the EMEW cell, and applied current. The solid horizontal
lines shown in Figure 5 (c) represent the calculated IR drop,
where the IR drop for solution E was approximately 2V for
Solution E versus 5 V for Solution B. This demonstrates
the importance of optimizing the electrode gap on capital
and operating cost of the full scale EO circuit based on
the solution chemistry. Further, when the IR drop is sub-
tracted from the total cell operating voltage, the remainder
which represents the difference between electrode operat-
ing potentials, while Solution E starts out comparatively
higher, after 20 minutes both solutions are similar. This
indicates that reactions taking place on the cell electrodes
and the associated overpotentials are the same.
Initial Cyanide Concentration. Figure 6 shows simi-
lar kinetics of thiocyanate consumption and associated pro-
duction of NaCN. This indicates that the presence of CN
has no effect on the overall kinetics of SCN oxidation.
Initial Chloride Concentration. Figure 7 (a) shows
that thiocyanate consumption is independent of chloride
presence. For cyanide production (Figure 7 (b)), during
the first 13 minutes of operation, the rise in free cyanide
concentration seems unaffected by the chloride presence,
however, as the test proceeded the rate of cyanide produc-
tion decreased. To assess OCN formation, the test in the
presence of chloride was extended to 60 minutes and cya-
nate concentration was checked to determine if the rate of
free cyanide production continued to decrease further. The
results indicate a reduction in cyanide production as well as
a reversal in cyanide concentration. Specifically, between 35
to 60 minutes, cyanide concentration in solution dropped
by half to 100 mg/L, and the cyanate analysis at 60 min
showed that 58% of CN produced since the start of the
test was lost to OCN. The comparison of results shown in
Figure 1 (b) and Figure 7 (b) shows that the formation of
chlorine was likely due to the high current density paired
with low initial thiocyanate concentration. This leads to
the conclusion that, in the presence of chloride and at low
Figure 5. Variation of (a) thiocyanate concentration (b) cyanide concentration and (c) cell voltage over the test course under
different initial thiocyanate concentration. Conditions: 943 A/m2, 663 m/h