The leaching of brannerite:influence of reactive gangue minerals

Rorie Gilligan and Aleks NikoloskiAusIMM International Uranium Conference, Adelaide June 7-8 2016

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)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

Questions?Contact us

r.gilligan@murdoch.edu.aua.nikoloski@murdoch.edu.au