elution behaviour of metals from carbon saimm 2009 m jeffrey r pleysier k bunney

Elution behaviour of metals from carbon SAIMM 2009

M Jeffrey

R Pleysier

K Bunney

CSIRO. Elution behaviour of metals from carbon

Background

• National Pollution Inventory reporting (NPI)• 93 reportable substances

• Objectives• Help industry and government with environmental planning and

management• Provide communities with information on emissions • Promote waste minimisation, cleaner production and efficiency

• Gold mines• Identified as major emitter of Hg

• Not amalgamations but as ppm levels in cyanide leach liquors.

2


Project Objectives - general

• ID toxic trace elements in CIP streams

• Deportment

• Understand of the dissolution of toxic trace elements. (cyanide)

• Potential to avoid or sequester in benign form.

• Adsorption/elution characteristic

• Hg, Ni, Cu, Sr, Cd, As, Pb, Si, Se, Sb, Te, Cr, ……..(19)

3


Project Objectives - specific

• Hg speciation ( carbon)

• Mine site - Hg only partly elutes EW and smelt regen gases

• Manage Hg in one concentrated stream

• Elution Column – construct , description

(better stripping of Hg)

4


Laboratory Elution Column

5



Pump

• Altex model 110A (PD piston type)

• 0.1 – 10 mL/min

• 0 – 25,000 kPa (4000 psi)

6



Pump

Gauges (2)

• 0 – 1500 kPa (0-230 psi)

7



Pump

Gauges

PRV (2)

• 70 – 1500 kPa adjustable

(10 – 225 psi)

8



Pump

Gauges

PRV

Column

• ØID 25 x 600 mm SS swagelok fittings

• 100 g carbon capacity

• 150 mL void volume.

• Screens top and bottom (300μm)

9



Pump

Gauges

PRV

Column

Heating

• Electrical heating tape/insulated

• T/C (type k)

• PID controller (Eurotherm CE 375)

• Pre heater coil for eluant.

10



Pump

Gauges

PRV

Column

Heating

Cooling

• SS coil in water bucket

11



Pump

Gauges

PRV

Column

Heating

Outlet•3 way- to gauge- prv- needle control valve

12


Commissioning

• Samples• Local mine site• C1 (Au 909 g/t Hg 187 g/t)

• C1 aw (Au 1140 g/t Hg 229 g/t)

• C2 aw (Au 355 g/t Hg 92 g/t )

• Commissioning• AARL

• (2% NaCN + 2% NaOH)• 130OC • Pressure 200 kpa• 30 min bake• 20 BV DI

13


Commissioning -profiles

Pressure

•200 kpa gave poor flow control

•700 kpa gave better flow and temp control

•Profile similar-not effected by pressure

Gold Elution

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500Eluant mass (g)

[Au

] (m

g/L

)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Au

Rec

ove

ry

200 kPa

700 kPa

14


Commissioning -profiles

Pressure

•Profiles similar

•Hg eluted sl faster

•Recovery sl lower

•Earlier than gold

•Typical plant recovery 50-60%

Mercury elution

0

5

10

15

20

25

30

35

40

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

200 kPa

700 kPa

200 kPa

700 kPa

15


Plant sample –Au profiles

Samples

•3 loaded carbon samples from local minesite

•Good profiles and good recoveries for gold

•Results similar to plant data.

Gold Elution

0

50

100

150

200

250

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

C1 loaded

C1 AW

C2 AW

16


Plant sample – Hg profiles

Samples

•As previous

•Hg recovery only 57%

•Lower if not acid washed 41%.

•Mechanism of improvement yet to be determined.

Mercury Elution

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

C1 loaded

C1 AW

C2 AW

17


Vary temp – Au profiles

Effect of temp

•130oC = 93% Au

•160oC = 97% Au

•Higher temp

•Faster elution

•Higher [Au]s

•Higher recovery.

Gold elution

0

50

100

150

200

250

300

350

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

130ºC

160ºC

18


Vary temp – Hg profiles

Effect of temp

•130oC = 57% Hg

•160oC = 40% Hg

•Higher temp =

•LESS mercury.

•Higher temp decomposes NaCN ?

Mercury elution

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

130ºC

160ºC

19


Vary cyanide – Au profiles

Effect of cyanide

•Increasing [NaCN]

•Increases rate Au

•Increases recovery

Gold elution

0

50

100

150

200

250

300

0 200 400 600 800 1000 1200 1400 1600 1800Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

0%

2%

5%

20


Vary cyanide – Hg profiles

Mercury elution

0

20

40

60

80

100

120

140

0 200 400 600 800 1000 1200 1400 1600 1800Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

0%

2%

5%

Effect of cyanide

•Increasing [NaCN]

•Increases rate Hg

•Increases recovery

•But still only 61%

•Potential to leave Hg on carbon

21


Zadra – Au profiles

Zadra

•Maintains [CN]

•Slower rate Au

Gold elution

0

50

100

150

200

250

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

AARL

Zadra

* soak period added to determine impact on Hg elution

*

22


Zadra – Hg profiles

Zadra

•Maintains [CN]

•Similar rate Hg

•Improved recovery

•76% Hg recovery

Mercury elution

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

AARL

Zadra

23


Zadra – Au at 110oC

Zadra

•Maintains [CN]

•Much slower rate

•Very poor recovery

•Temp important for Au

Gold elution

0

50

100

150

200

250

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

AARL 130ºC

Zadra 110ºC

24


Zadra – Hg at 110oC

Zadra

•Maintains [CN]

•Rapid elution

•Recovery 87%

Mercury elution

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Rec

ove

ry

AARL 130ºC

Zadra 110ºC

25


Data Split elution

Gold Mercury

•high temp low temp

•low [CN] high [CN]

Mutually exclusive conditions split elution?

•Zadra at 90oC + 130oC AARL

26


Split

Conditions

•Zadra at 90oC

•2% NaOH

•2% NaCN

•1500 mL

•AARL at 130oC

•30 min soak

•DI elution 1000 mL

Split elution

0

50

100

150

200

250

0 500 1000 1500 2000 2500 3000Eluant mass (g)

Co

nce

ntr

atio

n (

mg

/L)

0%

20%

40%

60%

80%

100%

Rec

ove

ry

Hg

Au

Series2

27


Split elution results

Mercury

•98% recovery in 10BV at 90oC

•Eluate… high Hg, low Au

•Hg recovery via S ppt etc

Gold

•10-15% Au into Hg eluate

•Further refinements possible (lower temp further???)

•Gold recycle recovery?

28


Summary

• Recovery of Hg into one stream possible.(ie removal from carbon/regen circuit desirable solution)

• Elute/separate Hg/Au with one set of elution conditions not possible,

• But split or sequential elutions works well

• Further optimisation/recovery possible

29


Further work / objectives

• ID other toxic trace elements in CIP streams• Hg started, As, Se, Cd, Sb, Te, Pb, Cr, Ni, organics ???

• Deportment • What accumulate where?

• Potential to avoid or sequester in benign form.

• Adsorption/elution characteristic • Effect of acid washing?

• Impact on silver• In progress.

30

Contact UsPhone: 1300 363 400 or +61 3 9545 2176

Email: [email protected] Web: www.csiro.au

Thank you

MineralsRon PleysierProject Scientist

Phone: 08 9334 8923Email: [email protected]: www.csiro.au/group


Split elution - Ag

Silver

•Elutes with Hg at low temp in CN

•Residual with gold

5% NaCN at 90ºC + DI at 130ºC

0

50

100

150

200

250

0 500 1000 1500 2000 2500 3000

Eluant mass (g)

Co

nc

(mg

/L)

Hg

Au

Ag


Split elution – reverse method

DI at 140ºC + 5% NaCN at 110ºC

0

50

100

150

200

250

0 500 1000 1500 2000 2500 3000

Eluant mass (g)

Co

nc

(mg

/L)

Hg

Au

Ag Silver

•Partially elutes with Au at high temp low CN

•But needs CN to elute bulk

•Best conditions for silver elution 130oC with 2%NaCN and NaOH

Silver elution

0.00

50.00

100.00

150.00

200.00

250.00

0 500 1000 1500 2000 2500

Eluant volume (mL)

[Ag

] m

g/L

0

10

20

30

40

50

60

70

80

90

100

Ag

re

co

ve

ry %


Hg Elutions - updates

• 10M HNO3 will strip Hg from carbon on the bench overnight.

• NaCN strips (atmospheric) at 40, 60, 75, 90oC

34

elution behaviour of metals from carbon saimm 2009 m jeffrey r pleysier k bunney

Documents

kpa adjustable

poor flow control700

better flow

gasesmanage hg

gtc2 awau

gtc1 awau

carbon saimm

naoh130oc pressure