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Process Chemistry and Mineralogy
of Brannerite Leaching
Rorie Gilligan and Aleks Nikoloski
SAIMM Hydrometallurgy Conferenc...
Introduction
• Brannerite, UTi2O6 is the most common refractory
uranium mineral
• Most important uranium mineral after ura...
Processing of brannerite and ores
• Leached under more aggressive conditions compared to
other U minerals
• >75°C, >25 g/L...
Mineralogy
• Associated in ores with titanium minerals
rutile (TiO2), ilmenite (FeTiO3) and titanite
(CaTi(SiO4)O)
• Brann...
Leaching experiments (acid)
• Brannerite leached for 5 hours
• 0.05 mol/L Fe3+
• 0.10-2.00 mol/L H2SO4 or 0.25-1.00 mol/L ...
Leaching experiments (alkaline)
• Brannerite leached for 24 hours
• 0.010 - 0.025 mol/L Fe3+ as K3Fe(CN)6
• 1.00 mol/L tot...
Brannerite specimen (Cordoba, Spain)
Brannerite interior
Anatase (TiO2)
coating
Anatase and
silica filled
cracks
Leaching kinetics – acid
Varied temperature, 0.25 mol/L acid Varied acid concentration, 52°C
0%
10%
20%
30%
40%
50%
60%
70...
Acid leaching kinetics – effect of apatite
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5
Uraniumextraction
Time ...
Leaching kinetics – alkaline
Varied temperature, 2:1 HCO3
-:CO3
2- Varied bicarbonate:carbonate ratio, 70°C
0%
10%
20%
30%...
Final extractions – varied temperature
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 10 20 30 40 50 60 70 80 90 100
Finalu...
Brannerite
characterisation
Si: Red
U: Green
Ti: Blue
Altered zones along
cracks low in U/Ca
Cracks filled with
microcryst...
Post-leach
mineralogy -
sulphuric acid
Altered zones
susceptible to
corrosion.
Note the depth of
corrosion either side
of ...
Post-leach
mineralogy -
hydrochloric acid
Uranium drawn out
from altered zones
Secondary titanium
oxide forms within
leach...
Post-leach
mineralogy – apatite
interaction
Varied temperature, 25
g/L H2SO4, apatite
• Residual apatite
associated with g...
Post-leach mineralogy (alkaline)
Minimal corrosion
at 50°C
Some pitting at
70°C
Formation of
secondary
anatase on
surface ...
Conclusions
• Brannerite leaching strongly dependent on temperature
in all lixiviants
• Sulphate media superior to chlorid...
Further reading
• Gilligan, R., Nikoloski, A.N. 2015. The extraction of uranium from
brannerite – A literature review. Min...
Questions?
Contact us
r.gilligan@murdoch.edu.au
a.nikoloski@murdoch.edu.au
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Gilligan and Nikoloski 2016 Process Chemistry and Mineralogy of Brannerite Leaching - SAIMM Hydrometallurgy 2016 Cape Town, South Africa

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Gilligan and Nikoloski 2016 Process Chemistry and Mineralogy of Brannerite Leaching - SAIMM Hydrometallurgy 2016 Cape Town, South Africa

  1. 1. Process Chemistry and Mineralogy of Brannerite Leaching Rorie Gilligan and Aleks Nikoloski SAIMM Hydrometallurgy Conference, Cape Town, August 1-3 2016
  2. 2. Introduction • Brannerite, UTi2O6 is the most common refractory uranium mineral • Most important uranium mineral after uraninite and coffinite • Has a general formula of (U,Th,REE,Ca)(Ti,Fe3+)2O6 • Thorium and light rare earth elements substitute uranium
  3. 3. Processing of brannerite and ores • Leached 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 1970s-80s
  4. 4. Mineralogy • Associated in ores with titanium minerals rutile (TiO2), ilmenite (FeTiO3) and titanite (CaTi(SiO4)O) • Brannerite in ores is amorphous and altered, due to its own radioactivity • Altered brannerite is more susceptible to leaching
  5. 5. Leaching experiments (acid) • Brannerite leached for 5 hours • 0.05 mol/L Fe3+ • 0.10-2.00 mol/L H2SO4 or 0.25-1.00 mol/L HCl • 25-96°C (up to 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
  6. 6. Leaching experiments (alkaline) • Brannerite leached for 24 hours • 0.010 - 0.025 mol/L Fe3+ as K3Fe(CN)6 • 1.00 mol/L total carbonate as NaHCO3 and Na2CO3 • 50-90°C (three intermediate values) • Selected experiments repeated with a high-brannerite ore from Queensland • Uranium and titanium dissolution monitored • Solids characterised by XRD, SEM and EDX
  7. 7. Brannerite specimen (Cordoba, Spain) Brannerite interior Anatase (TiO2) coating Anatase and silica filled cracks
  8. 8. Leaching kinetics – acid Varied temperature, 0.25 mol/L acid Varied acid concentration, 52°C 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 1 2 3 4 5 Uraniumextraction Time (h) H₂SO₄, 96°C HCl, 96°C H₂SO₄, 52°C HCl, 52°C H₂SO₄, 25°C HCl, 25°C 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 1 2 3 4 5Uraniumextraction Time (h) 2.00 M H₂SO₄ 2.00 M HCl 1.00 M H₂SO₄ 1.00 M HCl 0.50 M H₂SO₄ 0.50 M HCl 0.25 M H₂SO₄ 0.25 M HCl 0.10 M H₂SO₄
  9. 9. Acid 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, 0.25 mol/L H2SO4 Varied acid concentration, 52°C
  10. 10. Leaching kinetics – alkaline Varied temperature, 2:1 HCO3 -:CO3 2- Varied bicarbonate:carbonate ratio, 70°C 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 4 8 12 16 20 24 Uraniumextraction Time (h) 90°C 80°C 70°C 60°C 50°C 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 4 8 12 16 20 24Uraniumextraction Time (h) 4:1 2:1 1:1
  11. 11. Final extractions – varied temperature 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 10 20 30 40 50 60 70 80 90 100 Finaluraniumextraction Temperature (°C) 0.25 M H₂SO₄ 0.25 M HCl 1.00 M CO₃²⁻ (24 h) 1.00 M CO₃²⁻ (5 h)
  12. 12. Brannerite characterisation Si: Red U: Green Ti: Blue Altered zones along cracks low in U/Ca Cracks filled with microcrystalline anatase Si/Pb accumulate at edges of altered zones
  13. 13. Post-leach mineralogy - sulphuric acid Altered zones susceptible to corrosion. Note the depth of corrosion either side of the anatase inclusions Uranium is shown in green, titanium in blue
  14. 14. Post-leach mineralogy - hydrochloric acid Uranium drawn out from altered zones Secondary titanium oxide forms within leach pits at higher T Uranium is shown in green, titanium in blue, silicon in red 0.25 M HCl 25°C 0.25 M HCl 96°C
  15. 15. Post-leach mineralogy – apatite interaction 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
  16. 16. Post-leach mineralogy (alkaline) Minimal corrosion at 50°C Some pitting at 70°C Formation of secondary anatase on surface at 90°C Uranium is shown in green, titanium in blue, silicon in red
  17. 17. Conclusions • Brannerite leaching strongly dependent on temperature in all lixiviants • Sulphate media superior to chloride media • Phosphate minerals inhibit uranium dissolution in acid • Also contribute to brannerite passivation • Less of a problem at higher acidities • Acid and sulphate counteract the effects of phosphate • Alkaline leaching slow but effective
  18. 18. 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 164, 343-354
  19. 19. Questions? Contact us r.gilligan@murdoch.edu.au a.nikoloski@murdoch.edu.au

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