Council for Mineral Technology

The Resurrection of Hydrometallurgy’s Own

RIP van Winkle: UraniumMarthie Kotze

IntroductionØWhy RIP van Winkle??ØTitle character in a story by Washington Irving:v slept for 20 years and didn't recognize the world when he woke

up

v Uranium developments woke up after 25 years: is everything different?

ØRIP currently very topical for uraniumØ In1959 17 plants in RSA; only 1 remainedØRevival in Southern Africav biggest activity in Namibia

Uranium in NamibiaExtract Resources Limited Kalahari Minerals Plc Forsys Metals Corp. Westport Resources Namibia (Pty) Ltd. Dunefield Mining Company Ancash Investments (Pty.) Ltd. Galahad Gold Plc Paladin Resources Ltd Rössing Uranium Ltd Areva (Uramin) Namura Mineral Resources Xemplar Energy Corp. Metals Australia Ltd Bannerman Resources Limited West Australian Metals Ltd Cheetah Minerals Exploration Corporate & Resource Consultants Etruscan Resources Namibia Nam-China Minerals and Development Namibia Mineral Mining Plants & Products Philco Twenty (Pty) Ltd Reptile Investment Four Jaco Floris Smith Nova Energy Ltd. Pitchstone Exploration Ltd. Manica Minerals Ltd., Erongo Energy Ltd Atomredmetzoloto OJSC Reptile Uranium Namibia (Pty) Ltd Mineral Commodities Ltd Africa Uranium Ltd

Indian Ocean

MineralogyØ185 uranium minerals according to US Geological

SurveyØMineralogy can be complexØAssociated metals such as V, Mo, TiØMultitude of processing routesØProcess selection is done carefullyØActive industry from early 1950’sv Learn from lessons in previous cycle and other industries, eg

heap leaching

Uranium in HMDØPast 4 years: major increase in demand for uranium

project work at Mintek due to price hike/demand vLanger Heinrich, Kayelekera, Dominion Reefs, Buffelsfontein, Rand Uranium, Harmony, Valencia, Anglo Gold Ashanti, othersvCarbonate, sulphuric acid leaching: since 1920’svPressure leachingvS/L: flocculants, paste thickening, etcvDirect SX, direct IX, IX + SX (incl. RIP)

ØHMD activities:vResin evaluations, incl. silica issuesvResin durabilityvMetRIX™ demonstrationvHPGR: leaching efficiency?vDiagnostic leachingvBPC stripping: neutralization into column

Leach AspectsØ28% of all production via ISLv Rather hydrometallurgical mining

ØProcess improvements in Leninabad: 2 stage leachv Initial generation of ferrous via acid leach of Fe

vSubsequent aeration and acid leach

ØCarous acid as oxidantvDecrease in acid consumption

ØAcid pugging at Somair and Cominak, NigerØHeap leaching: Trekkopje, SomairØBioleaching: tank and heapØPressure leaching

Pressure LeachingØSince 1950’s

ØRefractory minerals such as brannerite, davidite

ØProduction of acid from associated S-minerals via

flotation

ØIn combination with atmospheric leach

Ø5 alkaline and 5 acid pressure leach plants

globally

ØDominion Reefs in Klerksdorp: 2008

ØKnowledge-base larger

Some Flowsheet OptionsØUranium One, Klerksdorp: CCD èBPC SXèADU

ØEzulwini: CCDèNIMCIXèSXèADU ppt

ØLanger Heinrich: CCD èClarification èFBIXèPpt

ØVaal River South: CCD èNIMCIX èMS SXè ADU

ØTrekkopje: Heap leach è NIMCIXè SDU

ØKayelekera: RIPè direct pptØAngloGold Ashanti: South Uranium upgrade, new

plant at Kopanang: NIMCIX / RIP

Uranium One: BPCs Klerksdorp

AngloGold Ashanti: Vaal River South

RIP: Gold/Uranium RecoveryØ RIP not novel technology:

v Early 1950’s proposed by USA Atomic Energy Commissionv Implemented by Anaconda Co: 3000 t/dv being used in FSU for decades for Au and U3O8v previously applied in some form in USA (baskets)v Relix process: inverted fluidised bed (resin floating at top)

§ demonstrated in pachuca tank, Stilfontein Gold Mine 1970§ West Driefontein: over 2 years§ Small scale demonstration run at NIM§ Mechanically operable, performance poor due to back mixing

Ø Use in Western World limitedØ Some Au RIP plants in Western World:

v but resins different; also operational demands for uranium higherØ Major potential CAPEX and OPEX savings for RIP vs

CCD/filtration, so v large drive to consider RIP especially for low grade ores

Ø Major resin improvements by most large resin manufacturers Ø Kayelekera installing agitated carousel-based RIP, direct ppt

Ø Cost model for MetRIX™: RIP generally more cost effective for uranium recovery from lower grade ores and large throughput

RIP: Opportunities & ConcernsOpportunitiesØ No solid/liquid separationØ No PLS clarification as for fixed bed IX and SXØ Direct precipitation

v Continuous elution: higher grade LSL, purer uranium product v can this consistently provide required product quality??

Major ConcernsØ Silica fouling and impact on OPEX

v Resin lifev Rate of fouling and concomitant regeneration requirementv Effect of silica on resin lifev Management strategy around silica – design to limit uranium

losses to barrenv Optimise resin residence time

Ø Resin durability or potential loss: sensitivity of economics to resin loss

RIP Grade Resins

300 400 500 600 700 800 900 1000 1100 1200

0

20

40

60

80

100

MP1 GT1 MP2 GT2

Cum

ulat

ive,

%

Size, µm

Silica FoulingØ Very little information from literature

Rate of silica foulingØ Silica concentration in PLSØ Temperature of leachØ Leach: pressure vs ambientØ pH or acid content of leachØ Time before PLS is contacted with resin: RIP

probably worseØ Resin residence time in leached pulpØ Silica content on resin

Impact of Silica FoulingØSlows down kinetics of loading

vLower operating capacityvLarger resin flow required to maintain uranium recoveries

ØSlower rate of strippingvLonger residence time in strippingvOften lower stripping efficiencyvLower recoveries in adsorption

ØIncrease in reagent consumption due to larger resin flowratesØCause crud formation in SX (SX on eluate)ØPoorer quality ADU due to silica content

Silica Fouling

1 2 30

4

8

12

16

20

24

SiO

2, %

Cycle of poisoning

MP1; MP2; GT1; GT2

SEM Analysis

0

100

200

300

400

500

600

0 100 200 300 400 500 600 700

0

100

200

300

400

500

600

0 100 200 300 400 500 600 700

Gel type resinSilica content: 0 %

4.47 %; 6 %; 9.1 %

Relative counts

Dis

tanc

e, µ

mMacroporous resin

Silica content: 0 % 6.2 %; 12.3 %; 18 %

Dis

tanc

e, µ

m

SEM+BEI+EDS

Silica Fouling – How?ØSi(OH)4 is neutral specie at pH 2 –v enter resin as non-electrolytev lower degree of crosslinking more favourable

Øquarternary ammonium acts as a precipitant vwhy not throughout resin??

ØHSO42- counter-ion on resin – hydrogen bonding

ØSurface phenomenon – part of solution precipitationv this would indicate that smaller resin with higher surface

area should have higher rate of silica ppt

U3O8 Loading- 24 hrs

0%

10%

20%

30%

40%

50%

60%

0% 5% 10% 15% 20% 25%

SiO2 content

Rela

tive

loss

of U

3O8 m

ax c

apac

ity

MP1 GT1 MP2 GT2

Adsorption: 8 hrs

0%

10%

20%

30%

40%

0% 5% 10% 15% 20% 25% 30%

SiO2 in the resin

Loss

in u

ptak

e af

ter 8

hrs

con

tact

MP GT Linear (MP) Linear (GT)

Sand Attritioning

1 2 3 4 50

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

5 0

5 5

1 2 3 4 50

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

5 0

5 5

M P 1 n o s i l i c a , c a u s t i c ; n o s i l i c a

6 . 2 % S i O 2 ; 1 2 . 3 % S i O 2 1 8 . 0 % S i O 2 ; L i n e a r f i t t i n g

Cum

ulat

ive lo

ss, %

Cum

ulat

ive lo

ss, %

G T 1 n o s i l i c a , c a u s t i c ; n o s i l i c a

4 . 5 % S i O 2 ; 6 . 0 % S i O 2 9 . 1 % S i O 2 ; L i n e a r f i t t i n g

C y c l e s

MetRIX™ Demonstration plant

ConclusionsØWhat did RIP find?ØVery different world, eg communication, etc.ØVery little ‘novel’ in uranium hydrometvBPCs for direct SX, even lower gradevHeap leaching, incl. biovOthers eg. radiometric sortingvFlotation for S-minerals and/or uraniumvS/L separation: PBCs, paste and high rate thickeners,etc

In HMDØFurther work required to select optimum resin typevWhat is optimum SiO2 content on resin: durability, reagent consumption, residence time ?

ØSilica management – solution and resinØFurther durability work in MetRIX™ demonstration plant –to be published in JulyØDirect precipitation from RIP eluate – main drivers:vCAPEX and OPEX for SX circuit (fire issues)vLower acid concentration required to minimise neutralisation costsvPurity??

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