Flotation of Ultramafic Ni Ore

Salah Uddin

Research SeminarMarch 12, 2010

Froth: Sulphides and Ultramafic

3

Convention flotation

0

2

4

6

0 20 40 60 80 100Ni recovery (%)

Ni g

rade

(%)

20

25

30

35

0 20 40 60 80 100Ni recovery (%)

MgO

gra

de (%

)H1 H2L H2UH3L H3U H4

Dai et al., 2009

Low Ni grade achieved through conventional flotation Not sufficient rejection of MgO minerals

4

Possiblity-1: Metal ion activation

With Cu

With Ni

D. Fornasiero and J. Ralston, 2005

Activation of negatively charged silicates by adsorbed positively charged metal ions possibly promotes MgO recovery

Effect of metal ions on surface charge

5

-0.0015

-0.001

-0.0005

0

0.0005

7.5 8.5 9.5 10.5 11.5

SP (V

)

pH

ore

0.006M MgCl2

0.018M MgCl2

Observation – Mg2+ interacts

6

Observation – Shift of potential to a more negative one suggests removal of positive metallic species from surfaces. This also indicates presence of

ionic species in the system

Effect of EDTA

7

pH 9 pH 11 pH 11 with EDTA

EDTA: Visual observations

8

Flotation test-1

CMC0.05g

1 wt% EDTA

Ore100g

Adjust pH~10Na2CO3

PAX0.004g

MIBC0.003g

Concentrates 1,2 and 3

Na2CO31g

Identify the effect of metal ions

Tail

9

Ni grade vs recovery

0

2

4

6

0 10 20 30 40 50 60 70 80

Ni recovery (%)

Ni g

rade

(%)

0 wt% EDTA

1 wt% EDTA

10

Mg grade vs. recovery

Overall, change in grade/recovery relationships suggests metal ion activation has some influence on flotation

0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 45 50

Mg recovery (%)

Mg

grad

e (%

)

0 wt% EDTA

1 wt% EDTA

11

Possibility-2: Entanglement

Micrograph of a ore sample shows Fibres apparently entangle the other particles

12

Score Compound Name

Chemical Formula

42 Clinochrysotile

Mg3 Si2 O5 ( O H )4

34 Lizardite 1\ITT\RG

Mg3 Si2 O5 ( O H )4

33 Magnesium Aluminum Silicate

Mg O ! Al2 O3 ! Si O2

MgO bearing minerals

A considerable portion of the ore is occupied by Clinochrysotile. This a type of chrysotile, the most prevalent form of naturally occurring asbestos

This can influence flotation by 1) entangle and entrainment and 2) Impeding bubble motion (higher viscosity pulp)

13

Fibre disintegration

Chrysotile

Amphibole

23 2 5 4 4 2( ) 6 3 2 ( )Mg Si O OH H Mg Si OH H O+ ++ → + +

Serpentine-acid reaction

One way to tackle this problem would be by weakening and disintegrating chrysotile fibres using acid

14

Flotation test-2

CMC

1 wt% EDTA

Ore100g (pH ~ 7)

Adjust pH 10Na2CO3

PAX MIBC

Concentrates 1,2 and 3

Tail

HCl

Identify the effect of fibre disintegration

0% HCl 5% HCl

10% HCl 15% HCl

Dissolved metal ions

Amount of dissolved Fe, Ni and Mg in solution was determined (ICP-MS)Higher dissolution of Mg corresponds to higher dimensional instability

and disintegration of fibres

0

2

4

6

8

10

12

0 5 10 15

Dis

tribu

tion

(%)

HCl

FeNiMg

17

Ni grade vs recovery

Significant increase in Ni grade vs recovery was achieved with 10 and 15 wt% HCl

0

4

8

12

0 10 20 30 40 50 60 70 80 90 100

Ni recovery (%)

0 wt% HCl

5 wt% HCl

10 wt% HCl

15 wt% HCl

Ni g

rade

(%)

18

Mg grade vs recovery

Significant decrease in Mg in the concentrates with 10 and 15 wt% HCl

10

14

18

22

0 5 10 15 20 25

Mg recovery (%)

Mg

grad

e (%

)

5 wt% HCl

10 wt% HCl15 wt% HCl

19

Insol recovery

Amount of insol in concentrates decreased with HCl concentration

0

10

20

30

40

con 1 tail

% In

sol

0% HCl

5% HCl

10% HCl

15% HCl

20

Conclusions

• Physical entanglement of chrysotile fibres with the particles most probably plays the key role

• Fibres can be effectively disintegrated using combined chemical (acid) and mechanical (grinding) treatment

• Result is significant improvement in Ni metallurgy