Appendices 5-13 - Nautilus Cares - Nautilus Minerals

Table 2: pH, redox (Eh), conductivity and dissolved oxygen of centrifuged
seawater from 1:10 ore:seawater 180 minute elutriation at 12 o C and 24 o C
Sample pH Redox mv Conductivity mS/cm Dissolved oxygen %
Sea water 8.13 223 50.1 84.9
12 C Blank 8.13 228 49.2 89.4
12C Dup 1 7.39 217 50.3 85.1
12C Dup 2 7.36 241 50.2 79.5
12C Dup 3 7.3 243 50.3 80.7
24C Blank 8.17 240 50.1 55.8
24C Dup 1 7.19 248 50.9 47.3
24C Dup 2 7.11 253 50.5 47.5
24C Dup 3 7.36 242 50.5 50.9
Sea water 8.09 268 49.9 55.4
Table 2 shows that the pH decreased further at the higher temperatures of 12 and 24 o C
compared to 6 o C. Figure 1 shows the decrease in pH of the elutriates at 6, 12 and
24 o C after 180 minutes. The 6oC data is from the Phase 1 experiment, but it is the ore
sample was used for both experiments and all other conditions were the same.
pH decrease
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
6 Deg 12 Deg 24 Deg
Temperature
Figure 1: Decrease in centrifuged seawater pH from 1:10 ore:seawater 180
minute elutriation at 6 o C, 12 o C and 24 o C. Note 6 o C data from Phase 1
experiment.
The decrease in pH with temperature shows the temperature dependence of the
oxidation of the sulfide ore under these conditions.
The Phase one experiment showed the alkalinity decreased by approximately 12%
between 0 and 60 minutes compared to the control seawater which is consistent with
the observed decrease in pH (Table 3). There was a further decrease in alkalinity at
9