1. The leaching of brannerite:
influence of reactive gangue minerals
Rorie Gilligan and Aleks Nikoloski
AusIMM International Uranium Conference, Adelaide June 7-8 2016

2. Introduction
• Brannerite, UTi2O6 is the most common refractory
uranium mineral
• Most important uranium mineral after uraninite
and coffinite
• Brannerite leaching chemistry studied in detail
• Presented at previous AusIMM Uranium
conference (June 2015)

3. Brannerite - background
• Has a general formula of
(U,Th,REE,Ca)(Ti,Fe3+)2O6
• Thorium and light rare earth elements substitute
uranium
• Associated with titanium minerals
• Complicated by the presence of reactive gangue
• Calcite, chlorite, apatite, fluorite

4. Processing of brannerite and ores
• Requires leaching under more aggressive conditions
compared to other U minerals
• >75°C, >25 g/L H2SO4
• Brannerite-rich U ores in Ontario, Canada leached
~75°C
60-75 g/L H2SO4
36-48 h leaching time
• Pressure leaching trialled in South Africa in the 1970s-
80s

5. Brannerite in Australia
• Minor U mineral at
Olympic Dam (SA) and
Ranger (NT)
• Major U mineral in
Valhalla, Skal and others,
Mount Isa, QLD
• Major U mineral at
Curnamona province,
Crocker Well, Mount
Victoria, SA
Image from: http://www.australianminesatlas.gov.au/aimr/commodity/uranium.html
Mount Isa
(Valhalla, Skal)
Olympic Dam
Curnamona Province
(Crocker Well and others)
Ranger

6. Gangue effects
• Acid consumers like calcite react rapidly with acid
• Others like chlorite react slowly
• Phosphate minerals have a more complicated
effect
• Scarce information specific to brannerite
• Apatite identified with brannerite in Mount Isa
(QLD), Curnamona province (SA), Central
Ukrainian Uranium Province

7. Gangue chemistry
• Insoluble uranium(VI) phosphates can form > pH 1.5-2
• Not likely an issue at >25 g/L H2SO4 needed to dissolve brannerite
• Phosphate ions hinder the reaction between ferric (Fe3+ or FeSO4
+)
and U4+ by forming complexes such as FeHPO4
+
• Fluorite, CaF2 will improve the leaching through formation of HF
• Can attack other gangue, improving liberation
• Also known to form gelatinous silica however, inhibiting solid-liquid
separation, SX and IX

8. Leaching experiments
• Brannerite leached in ferric sulphate and sulphuric acid
• 2.8 g/L Fe3+
• 10-200 g/L H2SO4
• 25-96°C (four intermediate values)
• Selected experiments repeated with gangue additives
• 10 g/L fluorapatite or fluorite
• Uranium and titanium dissolution monitored
• Solids characterised by XRD, SEM and EDX

9. Leaching kinetics – brannerite
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5
Uraniumextraction
Time (h)
96°C
52°C
25°C
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5Uraniumextraction
Time (h)
100 g/L H₂SO₄
50 g/L H₂SO₄
25 g/L H₂SO₄
Varied temperature, 25 g/L H2SO4 Varied acid concentration, 52°C

10. Leaching kinetics – effect of apatite
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5
Uraniumextraction
Time (h)
96°C
96°C + fluorapatite
52°C
52°C + fluorapatite
25°C
25°C + fluorapatite
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5Uraniumextraction
Time (h)
100 g/L H₂SO₄
50 g/L H₂SO₄
25 g/L H₂SO₄
100 g/L H₂SO₄ + fluorapatite
50 g/L H₂SO₄ + fluorapatite
25 g/L H₂SO₄ + fluorapatite
Varied temperature, 25 g/L H2SO4 Varied acid concentration, 52°C

11. Final extractions vs. acid concentration (52°C)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 50 100 150 200
Uranium,titaniumextraction
[H₂SO₄] (g/L)
U - ferric sulphate
U - ferric sulphate, apatite
U - ferric sulphate, apatite, corrected acid conc.
Ti - ferric sulphate
Ti - ferric sulphate, apatite
Ti - ferric sulphate, apatite, corrected acid conc.
Acid concentration adjusted according to P dissolution
Effect of apatite greater than what can be attributed to
a drop in acid concentration

12. Leaching kinetics – effect of fluorite
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5
Uraniumextraction
Time (h)
25 g/L H₂SO₄, 96°C + fluorite
100 g/L H₂SO₄, 52°C + fluorite
25 g/L H₂SO₄, 52°C + fluorite
25 g/L H₂SO₄, 96°C
100 g/L H₂SO₄, 52°C
25 g/L H₂SO₄, 52°C

13. Post-leach
mineralogy
Varied temperature, 25 g/L
H2SO4, apatite
• Residual apatite associated
with gypsum
• No uranium phosphates
were detected
• A phosphorus enriched
titanium oxide rim was
identified on leached
brannerite
• This suggests that the
effects of phosphate on
brannerite leaching are
more complex than general
uranium leaching

14. Post-leach
mineralogy
• Varied acid concentrations,
52°C, apatite
• Some pitting seen at 50-100
g/L H2SO4.
• Higher acid concentrations
counteracted the effects of
phosphate
P U Ti P S Ca
25 g/L H2SO4
100 g/L H2SO4
50 g/L H2SO4

15. Post-leach
mineralogy
• Varied acidity, 52°C,
fluorite
• Brannerite leached
alongside fluorite was
heavily corroded
• Fluorite did not dissolve
completely
• No brannerite identified in
96°C, 25 g/L H2SO4 leach
residue
Ca U Ti
25 g/L H2SO4
100 g/L H2SO4

16. Conclusions
• Phosphate minerals inhibit uranium dissolution
• Not just due to acid consumption
• Also contribute to brannerite passivation
• Less of a problem at higher acidities
• Acid and sulphate counteract the effects of phosphate
• Fluorite significantly increases rate of uranium dissolution

17. Further reading
• Gilligan, R., Nikoloski, A.N. 2015. The extraction of uranium from
brannerite – A literature review. Minerals Engineering 71, 34-48
• Gilligan, R., Nikoloski, A.N. 2015. Leaching of brannerite in the
ferric sulphate system. Part 1: Kinetics and reaction mechanism.
Hydrometallurgy 156, 71-80
• Gilligan, R., Deditius, A., Nikoloski, A. N. 2016. Leaching of
brannerite in the ferric sulphate system. Part 2: Mineralogical
transformations during leaching. Hydrometallurgy 159, 95-106
• Gilligan, R., Nikoloski, A.N., 2016. Leaching of brannerite in the
ferric sulphate system. Part 3: The influence of reactive gangue
minerals. Hydrometallurgy (under review)

18. Questions?
Contact us
r.gilligan@murdoch.edu.au
a.nikoloski@murdoch.edu.au