gilligan and nikoloski 2016 brannerite and gangue interaction - ausimm u conference adelaide 2016
TRANSCRIPT
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The leaching of brannerite:influence of reactive gangue minerals
Rorie Gilligan and Aleks NikoloskiAusIMM International Uranium Conference, Adelaide June 7-8 2016
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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)
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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
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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°C60-75 g/L H2SO4
36-48 h leaching time• Pressure leaching trialled in South Africa in the 1970s-80s
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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
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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
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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
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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
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Leaching kinetics – brannerite
0 1 2 3 4 50%
10%20%30%40%50%60%70%80%90%
100%96°C52°C25°C
Time (h)
Ura
nium
ext
racti
on
0 1 2 3 4 50%
10%20%30%40%50%60%70%80%90%
100% 100 g/L H₂SO₄50 g/L H₂SO₄25 g/L H₂SO₄
Time (h)U
rani
um e
xtra
ction
Varied temperature, 25 g/L H2SO4 Varied acid concentration, 52°C
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Leaching kinetics – effect of apatite
0 1 2 3 4 50%
10%20%30%40%50%60%70%80%90%
100%96°C96°C + fluorapatite52°C52°C + fluorapatite25°C25°C + fluorapatite
Time (h)
Ura
nium
ext
racti
on
0 1 2 3 4 50%
10%20%30%40%50%60%70%80%90%
100%100 g/L H₂SO₄50 g/L H₂SO₄25 g/L H₂SO₄100 g/L H₂SO₄ + fluorapatite50 g/L H₂SO₄ + fluorapatite25 g/L H₂SO₄ + fluorapatite
Time (h)U
rani
um e
xtra
ction
Varied temperature, 25 g/L H2SO4 Varied acid concentration, 52°C
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Final extractions vs. acid concentration (52°C)
0 50 100 150 2000%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
U - ferric sulphateU - ferric sulphate, apatiteU - ferric sulphate, apatite, corrected acid conc.Ti - ferric sulphateTi - ferric sulphate, apatiteTi - ferric sulphate, apatite, corrected acid conc.
[H₂SO₄] (g/L)
Ura
nium
, tita
nium
ext
racti
on
Acid concentration adjusted according to P dissolutionEffect of apatite greater than what can be attributed to a drop in acid concentration
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Leaching kinetics – effect of fluorite
0 1 2 3 4 50%
10%20%30%40%50%60%70%80%90%
100%
25 g/L H₂SO₄, 96°C + fluorite100 g/L H₂SO₄, 52°C + fluorite25 g/L H₂SO₄, 52°C + fluorite25 g/L H₂SO₄, 96°C100 g/L H₂SO₄, 52°C25 g/L H₂SO₄, 52°C
Time (h)
Ura
nium
ext
racti
on
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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
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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
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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
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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
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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)