Laterite Leach Tests

ANSTO Minerals Report C1206 to Lagoon Creek Resources – Westmoreland Deposits
Residue Grade (ppm U 3O 8)
400
350
300
250
200
150
100
50
0
5 7 9 11 13 15 17 19 21 23
Acid Addition (kg/t)
Junnagunna pH 1.5 Redtree pH 1.5
FIGURE 4.2 Acid Additions for Base Case Conventional Leaches
4.2.3 Optimisation Leaching
The initial optimisation leach tests were carried out at the coarse grind size distribution, as the
base case leaches indicated that finer grinding was not likely to be necessary. Nonetheless
leach tests at other grinds (P80 of 350 µm, 150 µm 75 µm) were also undertaken as part of the
optimisation study.
The “base” leaching conditions were as defined in Section 4.2.2, but at the grind (P80 of 250
µm) identified in the preliminary leach series. Each of three parameters (temperature, pH and
ORP) as summarised in the table below was varied in turn for each ore composite, while
keeping all the other parameters at the “base” level.
Conditions for Optimisation Leach Series
Effect of pH Effect of ORP Effect of Temperature
Base case at pH 2.0 Base case at 450 mV Base case at 50°C
Base case at pH 1.7 Base case at 550 mV Base case at 30°C
Base case at pH 1.3 Base case with addition of 1.0 g Fe 3+ /L
The optimisation leaching results for the Junnagunna composite are summarised in Table 4.4.
The Garee Redtree composite leaching results are summarised in Table 4.5. A total of 43
leach tests were carried out.
Most tests were carried out without additional ferric ion, but with the addition of sodium
permanganate oxidant to achieve an oxidation potential (ORP) of 500 mV. The Junnagunna
leaching tests achieved excellent uranium extractions ranging 95-98% and the Redtree
18