Laterite Leach Tests

ANSTO Minerals Report C1206 to Lagoon Creek Resources – Westmoreland Deposits
small addition was required to achieve 550 mV. The oxidant demand for both samples was
very similar for both samples. The optimum ORP is considered to be 550 mV.
4.5.4 Jack Ore Sample
• Under base conditions, the extraction of uranium from the Jack ore sample was 87%,
considerably less than the dilute leach result of 97%, and significantly less than the
96-97% extraction from the other two samples under base case conditions. This
result could be due to the very low ferric ion concentration (0.2 g/L) in the Jack
leach liquor;
• Addition of 1.0 g/L Fe, leaching at pH 1.2, and leaching at a finer grind of
P80 = 150 µm at pH 1.5 with addition of Fe, all increased the extraction from 87%
for base case conditions to 91-91.5%, after 24 h.
• Optimum conditions for the Jack sample would either be leaching at pH 1.2, with
other conditions at base case, or leaching at pH 1.5, with addition of 1.0 g/L Fe.
Note that the latter conditions may occur if Jack ore was blended with either
Junnagunna or Redtree because of the amount of iron dissolved from these ores.
Further work is recommended to identify conditions that could increase extraction
from the Jack ore.
• Reagent requirements for Jack ore were very low, less than half those for the
Redtree composite.
4.5.5 Leach Liquor
• For the Junnagunna and Redtree ores, iron was the dominant ion in solution. For the
Junnagunna ore the concentrations of elements in solutions generally decreased in the
order:
Fe>Al>Si>Ca>Mg≈K>P>As
• The Redtree ore contained about 6 times the level of arsenic than the Junnagunna ore,
hence the much higher arsenic levels in solutution. For the Redtree ore the concentrations
of elements in solution generally decreased in the order:
Fe>Al>Si>Ca≈As≈K≈Mg>P
The following general impacts of leach variables were evident:
• The concentrations of all elements, except K, increased with decreasing pH;
• The concentrations of all elements, except Ca and P, increased with increasing
temperature;
• Grind size had little impact on the concentrations of gangue elements in solution;
• The concentrations of all elements increased with increased leaching time;
• The concentrations of all elements, except As were marginally greater in the
Junnagunna liquor compared to Redtree, which was reflected in the acid requirement;
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