Leaching of Brannerite Ores

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AusIMM International Uranium Conference
Leaching of Brannerite Ores

June 2010

Speaker: Chris Bucknell

A Member of the Bureau Veritas Minerals Group

Contents

1. Disclaimers

2 Background on leaching Brannerite
2.

3. Bottle Rolls – as a base line

4. Agitation L
4 A it ti Leaches
h
a) Effect of Temperature
b) Effect of Grind Size
c) Effect of Free Acid Level

5. What next?

AMDEL - BUREAU VERITAS PRESENTATION – 2010 chris.bucknell@amdel.com

Disclaimers

Everything I know about anything can be written on a postage stamp.
The full data lying behind these results is not detailed as part of this
presentation but is necessary to draw inferences from the results.
The information presented is based on lab scale not plant scale.
When I say Brannerite, I am actually talking about the Uranium
predominantly contained in the Brannerite present, but also the U in
trace intergrowths of Uraninite associated with the Brannerite as well
Brannerite,
as the U in the Thorite.
All free acid levels are in g/L at the conclusion of the leach unless
otherwise specified ie they are discharge values.
All ORP values are referenced against a Ag/AgCl electrode.
If the answer to your question is not in this presentation then maybe
you misunderstood your question.


History of Brannerite Leaching


History of Brannerite Leaching

“One of the most difficult uranium minerals to dissolve” Born et al 1975.
Rate of Brannerite dissolution is directly proportional to sulphuric acid concentration.
Born et al
al.
BUT there is an upper limit to sulphuric acid concentration at which point the dissolution
rate decreases ~200g/L. Born et al.
Four fold increase in extraction from 50 deg C to 70 deg C Born et al
C. al.
Leaching rate increases with increasing ORP until Eh of +575mV. Born et al.
Leaching on an impure concentrate from Climax, Colorado showed 13% extraction at
g p ,
room temperature using 10% sulphuric acid. D.R. George 1950 per Clegg et al 1958.
Radium Hill concentrate was processed at Port Pirie in 98% boiling sulphuric acid.
Fitzgerald, M.L. and Hartley, F.R. 1965.
Ores from the Blind River district, require leaching for 48 hours at 50 dec C with 50g/L
free acid. Clegg et al 1958.
Elliot Lake processed at 48 hours in “hot” sulphuric acid discharging at 40g/L free acid.
F.C L d
F C Lendrum per B Born et al.
t l
Leaching of Valhalla ore at 50 deg C for 30 hours at 25g/L achieved extraction of 83-
85%. Goldney et al 1972.


Bottle Rolls – as a baseline

Bottle Roll Parameters
Mullock ore grade sample - likely weathered –
head grade 750ppm.
Temperature ambient.
Duration 7 days.
Sample size 1kg.
1kg
Target free acid of 20g/L.
Sodium chlorate addition of 1kg/T.
S f /
ORP target >550mV.
Slurry density 40wt%.
Two particle sizes trialled. One at 100%
passing 38mm and the other at 100% passing
19mm.

Bottle Rolls - as a baseline
100 30

90

25
80

/T)
%)
xtraction (%

mption (kg/
70
20

60

Ac Consum
50 15
Uranium Ex

40

10
30

cid
U

20
5

10

0 0
0 1 2 3 4 5 6 7 8
Float concentrate 50wt% solids
Target free acid 20g/L Temp 90 deg C Time (days)
U Extraction BR1 @ 38mm Uranium Extraction BR2 @ 19mm Acid Consumption BR1 @38mm Acid Consumption BR2 @19mm

Observations
1. Overall extraction of U was 22%. Extraction, potentially not flattened out.

2. Acid consumption of 27kg/T.

3. Suggests some relatively easily, but small, amount of extractable uranium present.


Agitation Leaches – Effect of Temperature

Agitation Leach Parameters
Mullock ore grade sample - likely weathered
– head grade 750ppm.
Duration 24 hours.
Sample size 1kg.
Target free acid of 20g/L
20g/L.
ORP target >550mV.
O
Slurry density 40wt%.
One particle size trialled @ 75 microns.
Range of temperatures 25, 50, 70, 90 deg C.


Agitation Leaches – Effect of Temperature
100

90

80
raction (%)

70

60
ranium Extr

50

40

30
Ur

20

10

0
0 5 10 15 20 25

Float concentrate
Grind size 40 microns
Time (hrs)
50wt% solids
Temp 90 deg C U Extraction - 25 deg C U Extraction - 50 deg C U Extraction - 70 deg C U Extraction - 90 deg C

Observations
1. Extraction effective only at 90 deg C.

2. Optimum extraction at 90 deg C of 93%.

3. Extraction potentially not flattened out.


Agitation Leaches – Acid Consumption
40

/T) 35

30
Acid Consumption (kg/

25

20

15

10
A

5

0
0 5 10 15 20 25

Float concentrate
Time (hrs)
50wt% solids
Temp 90 deg C Acid Consumption - 25 deg C Acid Consumption - 50 deg C Acid Consumption - 70 deg C Acid Consumption - 90 deg C

Observations
1. Reconfirms majority of acid is consumed by gangue.

2. Acid consumed at 90 deg C is double the level at ambient but extraction is 9 times better.

3. If you can keep the free acid low, you will waste less acid on the gangue.


Agitation Leaches – Effect of Grind Size

Agitation Leach Parameters
Concentrate sample – Head Grade 981ppm
981ppm.
Temperature 90 deg C.
Duration
D ti 24 hhours.
Sample size 1kg.
Target free acid of 30g/L.
ORP target >550mV.
Slurry density 50wt%
50wt%.
Two particle sizes trialled. One at p80 75
microns and the other at p80 40 microns.


Agitation Leaches – Effect of Grind Size
100

90

80

70
U Extractio (%)

60
on

50

40

30

20

10

0
0 5 10 15 20 25

Float concentrate
Target free acid 30g/L
Time (hours)
50wt% solids
Temp 90 deg C 75 microns 40 microns

Observations
1. Overall extraction of U was the same irrespective of grind size.

2. Extraction at 40 microns initially quicker than 75 microns.

3. What if the gangue is so effectively attacked with the high acid levels that grinding could be minimised or eliminated?


Agitation Leaches – Effect of Free Acid
100

90

80

70
U Extractio (%)

60
on

50

40

30

20

10

0
0 5 10 15 20 25

Float concentrate
Time (hours)
50wt% solids
Temp 90 deg C 12g/L 30g/L 40g/L

Observations
1. Free acid levels of 12g/L not sufficient to achieve significant extraction.

2. Extraction accelerated in the initial stages by higher free acid levels.

3. Similar ultimate extraction achieved with target free acid of 30 and 40g/L.


Conclusions

A temperature of 90 deg C was required before any real extraction of
U was observed. Compare this to 70 deg C in Born et al.
No observed difference in extraction between 50 and 70 deg C where
Born et al found a 4 fold increase.
Maybe you don’t need to grind it as fine as you think, due to the
intense acid attack on the gangue.
The initial extraction rate can be improved by moving from 30g/L to
40g/L but with little effect on the overall extraction.
Keeping the free acid low but above some threshold value (~20-
low, ( 20
30g/L), may minimise the acid consumption.
There is a quite complex interaction between temperature, free acid
and grind size to optimise against before finalising your capital
decisions.
Just as all Coffinites are not the same in terms of their leach
behaviour, it unlikely that all Brannerites will be the same.

References

Born, C.A., Queneau, P.B., Ronzio, R.A. (Sept 1975). Processing of
Wolframite Cassiterite
Wolframite-Cassiterite Concentrate for Brannerite Removal. Transactions
of the Society of Mining Engineers, AIME, Col 258, pp218-221.
Clegg, J.W. and Foley, D.D. (Sept 1958). Uranium Ore Processing.
Addison Wesley Publishing Company, Maaaschusetts, USA.
Goldney, N., Canning, R.G. and Gooden, J.E.A. (July 1972). Extraction
Investigations with ome Australian Uranium Ores AMDEL presentation to
Ores.
AAEC Symposium on Uranium Processing.
Fitzgerald, M.L. and Hartley, F.R. (1965) Eighth Commonwealth Mining
and Metallurgical Congress Vol3. Chapter 9 – Uranium. AMDEL Ltd
Report CM 1122/77.


Next Year………

So what about next years conference?

Some real ore examples can be presented from three possible areas:
1. Ion Exchange of Uranium from Carbonate Extractions

2. Selective precipitation of V from Carnotite Extractions
p p
3. Solvent Extraction of Brannerite sourced PLS


Amdel – A Member of the Bureau Veritas Minerals Group


Leaching of Brannerite Ores

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