cyanidation of a copper gold ore.pdf

5/19/2018 CYANIDATION OF A COPPER GOLD ORE.pdf

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I I I T E l U l n T I O n l I L 1011RIIIILM

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PRO[ESSlnr:

ELSEV IER Int. J. Miner. Process. 50 (1997) 127-141

C y a n i d a t i o n o f a c o p p e r - g o l d o re

G . D e s c h ~ n e s a ,* , P .J .H . P r u d ' h o m m e

a Energy, Mines and Resources Canada, Canada Ctr. fo r Mineral and Energy Technology, 555 Booth Street,

Ottawa, Ontario KIA OG1, Canada

Received 10 April 1996; accepted 13 January 1997

Abstract

A free mil ling gold ore, which contains 0.4% copper as chalcopyrite, was treated with cyanide.

In the pre-leaching, the kinetics of oxidation of soluble sulphides are not an accurate indication for

the length of the treatment. Efficient gold leaching is achieved only under specific conditions

using oxygen, lead nitrate and a high concentration of free cyanide. The addition of lead nitrate

results in a higher gold extraction, although cyanide consumption cannot be reduced below

1.85 kg/ t without a drop in the extraction. Without lead nitrate, the gold recovery is lower than

90% but with lead nitrate, it reaches 98%. The addition of oxygen increases the gold recovery by

1.5%. The extraction of gold is not sensi tive to lead nitrate additions when higher than 300 g/ t .

The redox potential values could thus be used as control parameters for lead nitrate addition, at the

different stages of cyanidation, to indicate the state of the system.

The increase of lead nitrate concentration inhibits the dissolution of chalcopyrite but the

approach used was not efficient enough to decrease the cyanide consumption. The high concentra-

tion of copper in solution requires a concentration of NaCN in the range of 700 mg/ L. When the

average NaCN concentration is lower than 640 mg /L, gold recovery drops significantly. It was

also found that lead nitrate can be added directly at the start of cyanidation to achieve a

performance equivalent to the situation in which it is added during pre-leaching. 1997 Elsevier

Science B.V.

Keywords: gold; cyanide; extraction; eaching; ead nitrate; oxygen; chalcopyrite

1 . I n t r o d u c t i o n

There are ma ny gold deposits with a signific ant amo unt of copper ( > 0.3%). Despite

the selectivity of cyanide for gold, copper minerals represent a real problem because of

* Corresponding author. E-mail: [email protected]

0301-751[6/97/ 17.00 1997 Elsevier Science B.V. All rights reserved.

Pll S0301-7516(97)00008-2


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128

G. Desch~nes, P.J.H. Prud homme / lnt. J. Miner. Process. 50 (1997) 127-141

t he i r so l ub i l i t y i n cyan i de so l u t i ons . Am ong t he coppe r m i ne r a l s , cha l copyr i t e and

ch r yso co l l a show a l ow so l ub i li t y ( Habash i , 1967). Tec hno l og i e s a r e cu r r en t l y be i ng

d e v e l o p e d f o r t h e t r e a t m e n t o f c o p p e r - g o l d o r e s f o r g o l d r e c o v e r y . W o r k o n a n

am m oni a / cyan i de l e ach sys t em i nd i ca t e s t ha t l e ach i ng a f l o t a t i on t a i l i ng unde r con -

t r o ll e d c o n d it io n s o f p H a n d a m m o n i a a l l o w s e f f e c t iv e g o ld r e c o v e r y a n d l o w c y a n i d e

consum pt i on ( Mui r e t a l . , 1995) . The Sce r e s i n i p r oces s a l l ows t he r ecyc l i ng o f cyan i de

c o n s u m e d b y c o p p e r m i n e r a ls b y l o a d in g t h e c o p p e r c y a n i d e o n t o a c t iv a t e d c a rb o n . T h e

S c e r e s i n i p r o c e s s a n d t h e a m m o n i a / c y a n i d e l e a c h i n g p r o c e s s h a v e r e a c h e d c o m m e r c i a l

sca le in the recent years (Zheng e t a l . , 1995) , whi le e f for t s a re s t i l l underway for the

deve l opm en t o f t h i ou r ea and t h i o su l f a t e l e ach i ng p r oces se s . Th i ou r ea l e ach i ng o f a

coppe r - go l d o r e showed m ode r a t e succes s ( Lacos t e e t a l . , 1996) .

The add i t i on o f oxygen and l e ad n i t r a t e i s known t o be bene f i c i a l f o r t he k i ne t i c s o f

g o l d d i s s o l u t i o n a n d / o r c y a n i d e c o n s u m p t i o n d u r i n g t h e p r o c e s s i n g o f o r e s c o n t a i n i n g

sulphide minera l s (Weichse lbaum e t a l . , 1989; Duf resne e t a l . , 1994; Desch~nes and

W al l ing f o r d , 1995). I t ha s a lso been d em o ns t r a t ed t ha t the add i t i on o f o t he r ox i d i z i ng

agen t s i nc r ea se s t he k i ne t i c s o f go l d d i s so l u t ion ( S t oy chev sk i and W i l li am s , 1993).

The add i t i on o f l e ad n i t r a t e and oxygen i s a com m on p r ac t i c e du r i ng t he cyan i da t i on

o f su l ph i de bea r i ng go l d o r e s ( Desch~nes and Pu t z , 1995) . F r om t he l a ck o f spec i f i c

i n f o r m a t i on in t he l i t e r a tu r e and d i ve r s i t y o f p r ac t i c e s i n go l d p l an ts , i t becam e app a r en t

t ha t a sys t em a t i c a s se s sm en t o f t he add i t i on o f l e ad n i t r a t e and oxygen i s r equ i r ed . An

exhaus t i ve b i b l i og r aph i ca l r ev i ew i nd i ca t ed t ha t l e ad n i t r a t e a c t s a s a c a t a l y s t a t t he

sur face of the gold , prevent ing pass iva t ion (Morr i son , 1994) . I t a l so inhib i t s the

d i s so l u t i on o f m e t a l l i c su l ph i des , t he r eby r educ i ng cyan i de consum pt i on .

The goa l o f t he cu r r en t wor k i s t o quan t i f y t he i n f l uence o f l e ad n i t r a t e on t he

l each i ng k i ne t i c s and r eagen t s consum pt i on du r i ng t he l e ach i ng o f a go l d o r e con t a i n i ng

cha l copyr i t e and a l so py r r ho t i t e a s t he r eac t i ve su l ph i de m i ne r a l s t o ob t a i n an e f f i c i en t

ex t r ac t i on o f go l d , an accep t ab l e consum pt i on o f cyan i de and a m od i f i c a t i on o f t he

copp e r m i ne r a l a c t i v i t y .

2 . E x p e r i m e n t a t i o n

2.1. Material

A s a m p l e o f 2 7 k g o f - 2 . 5 4 c m o r e f r o m A b it ib i , Q u e b e c , w a s c r u s h e d in a j a w

c r ushe r and i n a r o t a r y c r ushe r and t hen pu l ve r i zed . The l oad was t hen g r ound t o 89%

- 7 4 / ~m ( we t s c r een i ng ) i n a ba l l m i l l . I t was r o l l ed t o hom ogen i ze t he m a t e r i a l and

br eak up agg r ega t e s . To ob t a i n r ep r e sen t a t i ve s am pl e s , t he m a t e r i a l was cu t i n t o 5 - kg

ba t ches and t hen i n t o 500- g ba t ches , wh i ch we r e u sed f o r l e ach i ng . A 0 .635- cm r i f f l e

a n d a P T Z m o d e l R e t s c h r o t a r y fe e d e r w e r e u s e d .

T h e m i n e ra l o g i ca l s tu d y w a s d o n e b y s c a n n in g e l e c t ro n m i c r o s c o p y , o n a J E O L 7 3 3

scann i ng e l ec t r on m i c r op r obe i n backsca t t e r ed e l ec t r on m ode and us i ng ene r gy d i spe r -

s i ve X- r ay spec t r om e t r y . The m i ne r a l og i ca l ana l ys is by X - r ay d i f f r ac ti on ( Tab l e 1 )


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G. Desch ~n es , P . J .H . Pru d h o mm e / I n t . J . M in e r Pro cess . 5 0 (1 9 9 7 ) 1 2 7 -1 4 1 129

Table 1

Chemical and mineralogical analyses of the co pper-g old ore

Chem ical analysis (%) Mineralogical analyses

Au 9.55 (g /t ) Major phases: chlorite, quartz and albite

Si 22.4

Fe 10.9 Minor phases: chalcopyrite, pyrrhotite, ilmenite and magn etite

Al 6.9

Ca 4.8

Mg 3.4 Traces: sphalerite and marcasite

Sto

1.58.

Cu 0.40

Zn 0.3

As < 0.2

Pb 0.1

Sb


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130 G . D e s c h ~ n e s , P .J . H . P r u d h o m m e / l n t. J . M i n e r . P r o c e s s . 5 0 ( 1 9 9 7 ) 1 2 7 - 1 4 1

Fig. 2. Backscattered electron image show ing inclusions of Au -A g alloy in pyrrhoti te .

W a t e r f r o m t h e p l a n t w a s u s e d in t h e c y a n i d a t i o n t e st s. T h e c h e m i c a l a n a l y s i s o f th e

w a t e r i n d ic a te s a s m a l l a m o u n t o f f re e c y an i d e (1 5 r a g / L ) a n d s o m e c o p p e r ( 3 9 m g / L ) .

I t a l s o h a s a r e l a t i v e l y h i g h t h i o c y a n a t e c o n t e n t ( 3 4 7 m g / L ) .

2.2. Equipment and experimental procedure

The l ime , sod ium cyan ide , l e ad n i t r a t e and oxygen a r e a l l c e r t i f i ed r eagen t -g r ade

chemica l s , excep t f o r t he t e s t t o eva lua t e t he ox ida t i on o f su lph ides du r ing p r e - l e ach ing .

To quan t i fy t he k ine t i c s o f ox ida t i on o f so lub l e su lph ides t o su lpha t e and t h io su l -

pha t e , a p r e - l e ach ing t e s t was done . P r e - l e ach ing t akes 4 h , du r ing wh ich t ime , s ample s

a r e t aken a t i n t e rva l s o f 30 min , 1 h , 2 h and 4 h . D i s t i l l ed wa t e r i s added t o ma in t a in a

cons t an t pu lp dens i t y . L ime i s added t o ma in t a in pH a t 10 .5 . Where l e ad n i t r a t e i s added

dur ing p r ep roces s ing , i t i s i n t roduced immed ia t e ly a f t e r t he s t a r t o f ag i t a t i on .

T h e g o l d l e a c h i n g v e s s e l is m a d e o f g l a s s a n d h a s a c a p a c i t y o f o n e l it re . T h e c o v e r

has fou r open ings w h ich a l l ow in se r t i on o f t he e l ec t rodes , t he ag i t a to r and t he t ube fo r

o x y g e n a d d it io n . A C h e m c a d e t p H m o n i t o r g i v e s p H r e a d in g s . M i x i n g i s p r o v i d e d b y a n

a g i t a t o r w i t h 2 . 5 - c m T e f l o n p a d d l e s p o w e r e d b y a v a r i a b l e - s p e e d e l e c t r i c m o t o r .

T h e t e s t s w e r e p e r f o r m e d o n p u l p s ( 5 0 % w e i g h t ) f o r a l ea c h i n g t i m e o f 4 8 h . F o r

e a c h t es t, a s a m p l e o f 5 0 0 g o r e a n d 5 0 0 m L o f le a c h i n g s o l u t io n w e r e u s e d . T h e o r e

w a s i n t r o d u c e d i n t o t h e r e a c t o r a n d p u l p e d f o r a f e w m i n u t e s . T h e n t h e c y a n i d e s a l t

( N a C N ) w a s a d d e d . A g i t a t i o n s p e e d w a s k e p t c o n s t a n t a t 4 0 0 r p m . C y a n i d e w a s a d d e d

d u r i n g th e t es t t o m a i n t a i n a c o n s t a n t c o n c e n tr a t io n o f f r e e c y a n i d e ( + 5 % ) . A 2 5 - m L

sam ple o f pu lp was t ak en w i th a p ipe t t e a f t e r 4 . 0 h , 6 . 0 h , 24 .0 h and a t t he end . Af t e r

f i l t r a t i on o f t he s ample s , t he so l i d s we re r e tu rned t o t he r eac to r . The oxygen con t en t was

v a r i e d b y b u b b l i n g a m i x t u r e o f o x y g e n a n d a i r f o r c o n t r o l p u r p o s e s . T h e o x y g e n


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G. Desch~n es, P . J .H . Pru d h o m me / I nt . J. Min er . Pro cess . 5 0 (1 9 9 7 ) 1 2 7 -1 4 1 131

c o n t e n t w a s k e p t c o n s t a n t b y u s i n g a m a s s f l o w m o n i t o r a n d a n e l e c t r o d e w h i c h

m e a s u r e d t h e d i s s o lv e d o x y g e n c o n t e n t (D O ) .

T h e r e d o x p o te n t ia l w a s m e a s u r e d w i th a c o m b i n a t io n e l e c tr o d e ( P t, A g , A g C 1 / K C I

4 M ) con nec t ed t o a m u l t i m e t e r . At t he end o f the t e st , t he s l u r ry was f i l t e r ed and t he

f i l te r c ake w as w ashed w i t h 1000 m l o f d i s t il l ed wa t e r . Th i s c ake was an a l yzed by

pr ec i ous m e t a l s f i r e a s say a f t e r be i ng d r i ed , hom oge n i zed and s am pl ed . The go l d

ex t r ac t i on ca l cu l a t i ons a r e ba sed on t he go l d con t en t va l ue s o f t he p r oces sed t a i l i ngs ,

com par e d t o the go l d con t en t va l ue o f t he m i l l head s am pl e . Th e r e i s a 6% d i f f e r ence in

t he go l d c on t en t o f the av e r age ca l cu l a t ed head ( go l d i n t he t a il ing p l us go l d i n so l u t i on )

and t he head a s say .

Th e l e ach so l u t i on and wash so l u t ion w e r e t i tr a t ed f o r f r ee cyan i de wi t h s i l ve r n i tr a t e

us i ng r hodam i ne a s an i nd i ca t o r and bo t h so l u t i ons we r e a s sayed f o r go l d and ba se

m e t a l s ( Fe , Cu) by a t om i c abso r p t i on spec t r oscopy . The go l d concen t r a t i ons i n t he

so l u t i ons gave t he ex t r ac t i on k i ne t i c s p l o t . The p r e sence o f coppe r cyan i de caused

in te rfe r ,ence dur ing t i t ra t ion w i th s i lver n i t ra te . Th us , t i t r a t ion resul t ed in the loss o f

C N - f i' om th e c o p p e r / c y a n i d e c o m p l e x a n d a n in c r e a se in t h e v a lu e o b t ai n e d f o r f r e e

cyan i de . Th i s e r r o r i nc r ea sed a s t he coppe r concen t r a t i on i n t he so l u t i on i nc r ea sed . The

va l ues we r e no t co r r ec t ed because t he p l an t t ha t p r oces se s t h i s o r e u se s t he s am e

t i t ra t ion method.

3 . R e s u l t s

3.1. Pre-leaching

Fig . 3 i l lus t ra tes the oxida t ion of so luble su lphides to su lpha te and th iosulpha te . For

t h i s t e , ; t , d i s t i l l ed wa t e r was u sed ( 50% we i gh t , r oom t em pe r a t u r e ) . The pH was

Effect o f the lenght o f

the p re - leach

800 ~

~ 700 ~ S042

600

/

~' 500

.~_

400

W

3

.~. 200

1O0

$ 3 0 ~z

S2032

O - ~ , I , ,

60 120 180 240

Tim e ( rain)

Fig . 3 . K ine t i c s of the oxida t ion of so luble su lphides in the pre - l eaching of a copper -gold ore wi th a i r .

pH 10.5.


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132 G. Desch~nes, P.J.H. Prud homme lnt. J. Miner. Process. 50 (1997) 127-141

con t ro l l ed a t 10 .5 and o x ida t i on oc cu r r ed i n t he p r e sence o f a ir on ly . The r e su l t s i nd ica t e

tha t 75% o f the so lub l e su lph ides w e re ox id i zed t o su lpha t e s a f t e r 30 min . Th i s pe r i od o f

30 min r ep re sen t s t he t ime du r ing wh ich t he o r e i s ag i t a t ed w i th a i r i n t he mi l l c i r cu i t .

Ox ida t i on o f me ta l l i c su lph ides t o fo rm th io su lpha t e and su lpha t e occ u r s a cco rd in g to

the fo l l owing r eac t i ons :

2 S 2 - + 2 0 2 + H 2 0 - - + S z O 3 - + 2 O H - ( 1 )

S2 O 2 - --[-2 O H - + 2 0 2 ~ 2 SO 4 2- H20 ( 2 )

Th io su lpha t e ( $2 O 2- ) cou ld a l so be ox id i zed t o t e t ra th iona t e (La t imer , 1938 ):

2S2 O 2- --+ S4 O2 + 2e (3 )

Te t r a th iona t e i s no t s t ab l e i n a lka l i ne so lu t i ons , be ing conve r t ed t o t h io su lpha t e and

t r i t h iona t e acco rd ing t o (G o ldhabe r , 1983 ) :

4 S 4 O 2 - + 5 O H - - - + 5 S2 O 2 - + 2 S3 06 2 + 3 H 2 0 ( 4 )

F i g . 3 sh o w s a v e r y s m a l l c o n c e n t r a t io n o f t h i o s u lp h a t e ( 1 0 m g / L ) a n d t r it h io n a t e

( 5 8 m g / L ) a f te r 3 0 m i n ; th e c o r re s p o n d in g s u l p h at e c o n ce n t ra t io n i s 62 6 m g / L .

So lub l e su lph ides t ha t a r e d i s so lved a r e py r rho t i t e , ma rcos i t e and cha l copyr i t e , py r rho t i t e

be ing t he l e a s t s t ab l e .

3.2. Effect o f pre-leaching and oxygen

Tab le 2 i ll u s t r a te s t he e f f ec t s o f p r e - l e ach ing w i th a i r and l e ad n i t r a te and t he e f f ec t

o f i n je c t in g o x y g e n d u r i n g c y a n i d a t io n . T r e a t m e n t w i t h o u t p r e - l e a c h i n g a n d w i t h o u t th e

i n j ec t io n o f o x y g e n r e s u l ts i n a g o l d r e c o v e r y o f 8 9 . 6 % a n d a c y a n i d e c o n s u m p t i o n o f

1 .46 kg / t ( t e s t 1 ) . P r e - l e ach ing fo r 30 min w i th a i r ( t e s t 2 ) changes a lmos t no th ing i n

t h e s y s t e m , e v e n i f o x y g e n i s a d d e d d u r i n g c y a n i d a t i o n . T h e g o l d r e c o v e r y a n d c y a n i d e

c o n s u m p t i o n a r e p r a c t i c a l ly s i m i l a r. T h e a d d i ti o n o f 2 0 0 g / t P b ( N O 3 ) 2 d u ri n g p r e -

l e ach ing , w i thou t t he in j ec t i on o f ox yge n du r ing cyan ida t i on , r e su l t s in an obv iou s

i n c r e a se i n g o l d r e c o v e r y to 9 5 . 3 % . T h e r e i s a n i n c r e a s e o f 0 . 1 0 k g / t i n c y a n i d e

c o n s u m p t i o n , t o 1 . 6 4 k g / t ( t e s t 3 ) .

Table 2

Effect of pre-leaching on the cyanidation of a copper-go ld ore

T e s t Pre-leaching 02 NaCN cons. [Cu] [CNS- ] Au rec.

(ppm) (kg/t) (mg /L) (mg /L) (%)

1 none 7 1.46 514 1045 89.6

2 air 15 1.54 554 1071 89.8

3 Pb(NO3)2 7 1.64 627 1275 95.3

4 Pb(NO3)2 15 1.85 713 1418 96.8

Pre-leaching: 30 m in; cyanidation: pH 10.5, Na CN 700 m g/ L , 48 h.


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G. Desch~nes, P.J.H. Prud homme / lnt. J. M iner. Process. 50 (1997) 127-141 133

E f f e c t o f o x y g e n a n d

pre-leach

lOO

8 0

~ 70

._~ 6 0 a t i o

50 /~ Y ~ 1 1 None A i r

f 2 A i r 0 2

~ 40 3 Pb(N O3)z Air

.I

~ 4 Pb (NO3)2 02

'~ 30

20

10

0 ~ I ~ ~ ~ I ~ ~ L ~ ~ i i ~ ~ ~ I ~ i

8 16 24 32 40 48

Time (11)

Fig. 4. Effect of pre-leachingand oxygen on gold leaching of a copper-gold ore. Pre-leaching:Pb(NO3)2 200

g/t, 30 rain; cyanidation:pH 10.5, NaCN 700 mg/L, 02 15 ppm, 48 h.

Elsne r's equation shows the role of oxygen in the oxidation-reduction reaction:

4Au + 8CN - + 0 2 + 2H 20 --* 4A u( CN )2 + 4O H- (5)

The c ombine d use of lead nitrate during pre-leaching (200 g /0 and 0 2 (15 ppm)

during cyanidation increases the gold recovery to 96.8%. However, cyanide consump-

tion also increases to 1.85 kg /t . Fig. 4 presents the gold dissol ution plots for tests 1 to 4.

It appears that the use of lead nitrate and oxygen provides the most rapid dis soluti on of

the gold (test 4) and the highest gold recovery.

3 .3 . E f f e c t o f P b ( N O 3 )2 c o n c e n t r a t i o n d u r i n g p r e - l e a c h i n g

An examinati on of Table 3 indicates that gold recovery is increased proportionally to

lead nitrate added during pre-leaching. In fact, it rises from 96.5% Au with 100 g/t

Table 3

Effect of the addition of lead nitrate on the cyanidationof a copper-gold ore

Test Pb(NO3)2 NaCN cons. [Pb] Au rec.

(g/t) (kg/t) (mg/L) (%)

5 100 1.86 < 0.05 96.5

4 200 1.85 < 0.05 96.8

6 300 2.06 < 0.05 97.8

7 400 2.16 < 0.05 97.3

8 200 a 2.41 < 0.05 97.9

9 300 2.24 < 0.05 97.4

a Test with the addition of Pb(NO3)2 during gold leaching: [NaCN] 750 mg/L.

Pre-leaching: 30 min; cyanidation:pH 10.5, NaCN 710 mg/L, 02 15 ppm, 48 h.


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134 G . D e s c h ~ n e s , P . J . H . P r u d h o m m e / l n t. J . M i n e r . P r o c e s s . 5 0 ( 1 9 9 7 ) 1 2 7 - 1 4 1

E f f e c t o f l e a d n i tr a t e

c o n c e n t r a t i o n

1

9

8O

A 7

i

0

40

20

10

0

8 16 24 32 4 48

T i m e h )

Fig. 5. Effect of lead nitra te on gold leac hing of a cop per -go ld ore . Pre- leaching: 30 m in; cyanidation:

pH 10.5 , NaC N 710 m g/ L, 02 15 ppm, 48 h.

P b ( N O 3 ) 2 t o 9 7 . 8 % w i t h 3 0 0 g / t P b ( N O 3 ) 2 ( te s ts 4 t o 6 ) . T h e g o l d r e c o v e r y r e m a i n s

t he s am e f o r P b ( N O 3 ) 2 c o n c e n t r a t io n s gr ea t e r t han 300 g / t ( t e s t 7 ) .

A r ecen t r ev i ew ( M or r i son , 1995) i nd ica t e s t ha t l e ad n i tr a t e c an ac t i n d i f f e r en t ways .

I ndeed , i t c an ac t i va t e the su r f ace o f a pa s s iva t ed pa r t i c l e o f go l d , p r even t t he f o r m a t i on

of a pa s s i va t i on f i l m on t he su r f ace o f go l d , a c t a s an ox i d i z i ng agen t , p r ec i p i t a t e t he

so l ub l e su l ph i des o r p r om ot e t he ox i da t i on o f so l ub l e su l ph i des t o su l pha t e. I n t h is c a se ,

l e ad n i t ra t e f avour s t he d i s so l u t i on o f go l d , so i t p r ob ab l y ac t s a t t he su r f ace o f t he go l d

par t i c les to prevent pass iva t ion . F ig . 5 i l lus t ra tes the extent of gold d i sso lu t ion in

p r e sence o f va r i ous concen t r a t i ons o f l e ad n i t r a t e . Al t hough t he sys t em us i ng 400 g / t

Pb ( N O3 ) 2 shows t he f a s t e s t d is so l u t i on k i ne t ic s du r i ng t he f i r st 16 h, t he g o l d r eco ve r y

i s a b o u t t h e s a m e a t 3 0 0 g / t a n d 4 0 0 g / t P b ( N O 3 ) 2 w i t h 9 7 . 8 % a n d 9 7 . 3 % ,

r e spec t i ve l y .

Th e add i t i on o f Pb ( NO 3) 2 i nc r ea se s cy an i de con sum pt i on no t i c eab l y . In f ac t , con -

s u m p t i o n is 1 .8 6 k g / t w i t h 1 0 0 g / t

P b ( N O 3 ) 2 a n d

r i s e s t o 2 . 1 6 k g / t w i t h 4 0 0 g / t

Pb ( N O3) 2 . P r ev i ous w or k on a su l ph i de - bea t i ng go l d o r e i nd i ca t ed a 50% dec r ea se i n

cyan i de consum pt i on us i ng l e ad n i t r a t e wh i l e keep i ng t he s am e go l d r ecove r y , bu t

i nc r ea s i ng l e ach i ng k i ne t i c s by 30% ( DeschSnes and Wa l l i ng f o r d , 1995) . The d i f f e r ence

i n t he r e sponse o f t he o r e t o t he add i t i on o f l e ad n i t r a t e i s a t t r i bu t ed t o t he du r a t i on o f

t he p r e - l e ach i ng . I n t he p r ev i ous wor k , t he r e was a 4 - h p r e - l e ach i ng f o r an o r e

con t a i n i ng 12% pyr i t e , 1 .4% py r r ho t i t e and 0 .14% cha l copy r i t e . I n t he p r e sen t te s t wor k ,

t he p r e - l e ach i ng i s on l y 0 .5 h and t he m a t e r i a l ha s a coppe r con t en t 3 t i m es h i ghe r t han

t he p r ev i ous o r e . The r e i s no py r i t e , and py r r ho t i t e i s a l so a m i no r com ponen t .

F i g . 6 shows t he coppe r d i s so l u t i on cu r ve and t h i ocyana t e f o r m a t i on a s a f unc t i on o f

t he am o un t o f added l e ad n i tr a t e. Be t wee n 0 and 100 g / t l e ad n it r a te , t he r e i s s e l ec ti ve

l each i ng o f coppe r and su l phur . Consequen t l y , t he concen t r a t i ons f o r coppe r and


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Ef fec t o f l ead n i t r a te


1800~ 1800

1600 700

0 0 i /

V S

o= 12oo

1000~ 500

800 ~

4 0 0

0 1O0 200 300 400

[ P b N O 3 ) 2 ] g / t )

Fig . 6 . Copper d i s so lu t ion and format ion of th iocyana te dur ing cyanida t ion as a func t ion of the concent ra t ion

of l ead ni t ra t e . P re - l eaching: 30 min; cyanida t ion: pH 10.5, NaC N 71 0 rag / l , 02 15 ppm, 48 h .

t h iocyaJaa t e i n so lu t i on i nc r ea se . Acco rd ing ly , t h i s c ause s an i nc r ea se i n cyan ide

c o n s u m p t i o n . W o r k o n a d i f f e r e n t m a t e r i a l , w i t h s u r f a c e a n a l y s e s b y T O F - L I M S ( T i m e

o f F l ig h t L a s e r I o n i s a t io n M a s s S p e c t r o m e t r y ) ( M a r t i n a n d C a b r i , 1 9 9 4 ) in d i c a te s t h a t

c h a l c o p y r i t e s h o w s m o r e p r o n o u n c e d d i s s o l u t i o n w h e n t r e a t e d w i t h l e a d n i t r a t e .

A c c o r d i n g t o F i g . 6 , t h e c o p p e r c o n t e n t re a c h e s a m a x i m u m a r o u n d 1 20 g / t o f

Pb (NO: ~) 2 , then dec rea se s a s m ore l e ad n i t r a t e i s add ed . A t t h i s l eve l , l e ad n i t r a te

pas s iva t e s t he su r f ace o f t he cha l copyr i t e . I t s eems t ha t t he r e i s a d i r ec t r e l a t i onsh ip

b e t w e e n d i s s o l v e d c o p p e r , c y a n i d e c o n s u m p t i o n a n d g o l d r e c o v e r y . T h e r e l a t i o n s h i p

a m o n g t h e s e t h re e f a c t o r s c e a s e s to a p p l y w h e n t h e c o n c e n t r a ti o n o f l e a d n i tr a te e x c e e d s

2 0 0 g / t . M o r e o v e r , t h e C N S - c o n t e n t f l u c t u a t e s w i t h o u t i n d i c a t i n g a n y s p e c i f i c

te nd en c, y . T h e c o p p e r a n d C N S - c o n t e n t s t h u s c a n n o t b e u s e d a s i n d i c a t o rs t o g u i d e t h e

a d d i ti o n o f l e a d n i tr a te i n d e f i n i n g t h e o p t i m u m s y s t e m .

The r edox po t en t i a l shows a spec i f i c r e l a t i onsh ip t o t he sys t em. F ig . 7 i l l u s t r a t e s t he

c h a n g e i n r e d o x p o t e n t i a l w i t h t i m e f o r d i f f e r e n t c o n c e n t r a t i o n s o f l e a d n i t r a t e a d d e d

dur ing p r ep roces s ing . I t i s c l e a r t ha t t he o r e r eac t s d i f f e r en t l y depend ing on t he amoun t

o f l e ad n i t r a t e added du r ing t he p r e - l e ac h ing . I n f ac t , an i nc r ea se i n Pb (NO 3) 2 concen t r a -

t io n i n c r e a s e s t h e r e d o x p o t e n ti a l. F o r 1 0 0 g / t P b ( N O 3 ) 2 , t h e r e d o x p o t e n t i a l v a r i e s

b e t w e e n - 1 6 0 a n d - 1 7 6 m V , w h i l e f o r 4 0 0 g / t P b ( N O 3 ) = , t h e re d o x p o t e n t ia l v a r i e s

b e t w e e n - 1 17 a n d - 1 45 m V . T h e s e v a l u e s c o u l d th u s b e u s e d a s c o n t r o l p a r a m e t e r s a t

t h e d i f f e r e n t s ta g e s o f c y a n i d a t i o n a n d c o u l d i n d i c a t e t h e s t a t e o f t h e s y s t e m a t d i f fe r e n t

l e a c h i n g t i m e s . F o r t h i s o re , c o p p e r d i s so l u t io n i s a b o u t 3 5 % . T h i s v a l u e i s m u c h h i g h e r

than t ha t r epo r t ed i n t he l i t e r a tu r e , wh ich i s 5 . 6% fo r cha l copyr i t e (Habash i , 1967 ) . Of

t h e m i n e r a l s c o n t a i n in g c o p p e r , c h a l c o p y r i t e s h o w s t h e l o w e s t d i s s o l u ti o n r a t e .


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E f f e c t o f le a d n i t ra t e c o n c e n t r a t io n

o n t h e r e d o x v a l u e

-100

T e s t [ P b N 0 3 ) 2 ]

-110 (g/t)

5 100

-120 4 200

\ 6 300

:~A -13 0 \ ~ _7 4 00

x -140

o

= -150

-160

~ ~

-170

- 1 8 0 t I i i I i i I i I i

0 8 16 24 32 40 48

T i m e ( h )

F i g . 7. R e d o x p o t e n t i a l f o r g o l d l e a c h i n g a s a f u n c t i o n o f l e ad n i t r a t e a d d e d . P r e - l e a c h i n g : 3 0 m i n ; c y a n i d a t i o n :

p H 1 0 . 5 , N a C N 7 1 0 m g / L , 0 2 1 5 p p m , 4 8 h .

F i g . 8 i ll u s tr a te s t h e r e la t io n s h i p b e t w e e n g o l d r e c o v e r y a n d t h e r e a g e n ts c o n s u m p t i o n

e x p r e s s e d a s t h e g r o s s p r o f it ( e x tr a c t io n i n c o m e l e s s t h e c o s t o f r e a g en t s: P b ( N O 3 ) 2 ,

1 . 2 0 / k g ; N a C N , 2 . 0 0 / k g ) . T h e o p ti m u m s y st em u s e s b e t w e e n 1 00 a n d 3 0 0 g / t

P b ( N O 3 ) 2 . M o r e o v e r , w e c a n s e e t h a t th i s g r a p h i n d i c a t e s a s m a l l v a r i a t i o n in p r o f it

E f f e c t o f l e a d n i t r a t e


1 7 5

150

I -

. . . ; - , ~ - - - - ~ .., - - .~.

0

n ,

o .

0

l= 125

1 0 0 , i , , I , , i , I i i , , I , , , h I , , , ,

0 1O0 200 3 00 400 500

[ P b N 0 3 ) 2 ] g / t )

F i g . 8 . P r o f i t f r o m g o l d l e a c h i n g a s a f u n c t i o n o f t h e a m o u n t o f l ea d n i t r at e a d d e d . P r e - l e a c h i n g : 3 0 m i n ;

c y a n i d a t i o n : p H 1 0 . 5 , N a C N 7 1 0 m g / L , 0 2 1 5 p p m , 4 8 h .


11/15

G. Desch ~nes , P . J .H . Pru d h o m me / I nt . J. Min er . Pro cess . 5 0 (1 9 9 7 ) 1 2 7 -1 4 1 137

Ef fect o f the locat ion point

o f lead n i tra te add i tion

~ 7 0

50 ~

ea ch Cy a n

~ / / I 4 Pb(NO3)z 02 I

20

10

0

0 8 16 24 32 40 48

T i m e h )

Fig . 9 . E l~fec t of the meth od o f addi t ion of l ead n i t ra t e on gold l eaching o f cop per -go ld ore wi th Pb(NO 3) 2

200 g / t . P re - l eaching 30 rn in ; cyanida t ion: NaC N 710 ra g/ L , pH 10.5 , 02 15 ppm , 48 h .

( a b o u t $ 1 . 0 0 / 0 in t he r a n ge o f c o n t en t v al u es b e tw e e n 1 00 a nd 4 0 0 g / t o f P b ( N O 3 ) 2 .

As t he op t i m um sys t em i s de f i ned by econom i c c r i t e r i a , i t c an be s een t ha t t he bene f i t

gener at qed by t he i nc r ea se i n g o l d r eco ve r y i s d i m i n i shed b y t he c os t o f ad d i ng m or e l e ad

n i tr a te a n d c o n s u m i n g m o r e c y a n id e . N o t e s t w a s p e r f o r m e d b e t w e e n 0 a n d 1 0 0 g / t l e a d

n i t ra t e bu t r epe t i t i on o f t he t e s t wi t hou t l e ad n i t r a t e i nd i ca t e s a l m os t t he s am e r e su lt s .

A s t udy on t he add i t i on o f l e ad n i t r a t e du r i ng l e ach i ng , a s opposed t o i t s add i t i on

dur i ng p r e - l e ach i ng , show ed t ha t t h i s p r ac t ic e i s e f f i c i en t bu t t he p r e - l e ach i ng i s r equ i r ed

t o r educe t he cyan i de consum pt i on ( Desch~nes and W a l l ing f o r d , 1995). F i g . 9 i l lu s t ra t e s

bo t h ca se s . Cur v e 4 r ep r e sen ts t he add i ti on o f l e ad n i tr a t e ( 200 g / t ) du r i ng p r e - l e ach i ng

and cu r ve 8 i t s add i t i on a t t he s t a r t o f cyan i da t i on . Cur ve 8 i nd i ca t e s be t t e r cyan i da t i on

kine ti cs ,: and a g old reco ve ry tha t i s 1 .1% higher . C yan ide con sum pt ion i s a l so grea te r

w h e n l e a d n it ra t e is a d d e d a t th e s t ar t o f c y a n i d a ti o n ( ~ 0 . 6 k g / 0 . H o w e v e r , th e t w o

sys tem ~; a r e com par ab l e i n econ om i c te r m s . L ead n i t ra t e c an t hus be added e i t he r du r i ng

cyanid~tt ion or d ur ing pre- leacb ing .

3.4. Ej)~ct of cyanide concentration

Th e e f f ec t o f t he concen t r a t ion o f f r ee cyan i de was a s se s sed w i t h t he sys t em us i ng

pr e - l each i ng wi t h l e ad n i t r a t e and i n j ec t i on o f oxygen du r i ng t he 48 - h cyan i da t i on

pe r i od . The r e su l t s a r e g i ven i n Tab l e 4 . The go l d ex t r ac t i on i s no t i n f l uenced by

c y a n i d e c o n c e n t ra t io n s b e t w e e n 6 4 0 to 8 4 0 m g / L N a C N ( ~ 9 6 . 6 % ) . T h e e x tr a c t io n i s

v e r y s e n s it iv e t o t h e f r e e c y a n i d e c o n c e n t r a ti o n w h e n t h e s o d i u m c y a n i d e c o n c e n t r a t io n

f a ll s b e l o w 6 4 0 m g / L ; t h e y i e l d d r o p s ra p i d ly , to le s s t h a n 9 0 % w i t h 5 0 0 m g / L N a C N ,

and th i s cor resp ond s to a loss of 6 .7% ( tes t s 10 and 12). The re is a l so a s igni f i cant

i n c re a s e i n t h e c y a n i d e c o n s u m p t i o n w h e n t h e c o n c e n t r a ti o n o f N a C N i s g r e a te r th a n

7 1 0 m g / L ( fr o m 1 .85 k g / t t o 2 .7 8 k g / t ) .


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138 G. Desch~nes, P.J .H. P rud hom me / ln t. J . Mine r . Process . 50 (1997) 12 7-1 41

T a b le

4

E f f e c t o f c y a n id e c o n c e n t r a t io n o n g o ld l e a c h in g o f a c o p p e r - g o ld o r e

T e s t [NaCN] NaCN cons. [Cu] [Fe] Au rec.

(mg/L) (kg/t) (rag/L) (mg/L) (%)

10 500 1.56 675 4 89.4-

12 640 1.76 691 6 96.5

4 710 1.85 713 8 96.8

11 840 2.78 770 24 96.6

Pre- leaching:

Pb(NO3) 2 200 g /t , 30

rain; cyanidat ion:

pH 10.5, 02 15 ppm, 48 h.

The add i t iona l free cyan ide does not promote go ld d is so lut ion . Rather , the add i t iona l

c y a n i d e f a vo ur s t he d i s s o l u t i o n o f c o p p e r , t he c o n c e n t r a t i o n o f w h i c h i n c r e a s e s t o 7 7 0

p p m . T he i n c r e a s e o f f r e e c y a n i d e c o n c e n t r a t i o n s ho u l d i n c r e a s e t he c o n c e n t r a t i o n o f

C u( C N ) 43 - a n d d e c r e a s e the c o n c e n t r a ti o n o f C u ( C N ) 2 ( H s u a n d T ra n , 199 5 ) . I n fa c t ,

t h i s i n c r e a s e i s r e s p o n s i b l e f o r o n l y a b o ut 0 . 2 4 k g / t o f a d d i t i o n a l c y a n i d e c o n s um e d .

N o t e t ha t i r o n f r o m p y r rho ti te o r cha l c o p y r i t e i s o n l y ve r y s l i g h t l y d i s s o l ve d . T h e c o p p e r

d i s s o lu t i o n w o u l d b e r e s p o n s ib l e f o r 9 0% o f t h e c y a n i d e c o n s u m e d i f i t is a s s u m e d t h a t

t h e c o p p e r c y a n i d e c o m p l e x e x i s t s m o s t l y a s C u ( C N ) 2 - c o m p l e x .

F i g . 10 s ho w s t he g o l d d i s s o l u t i o n k i n e t i c s f o r t he fo ur c o n c e n tr a t i o n s o f f r e e c y a n i d e

t e s t e d ( e x p r e s s e d a s N a C N ) . T he i n c r e a s e i n c y a n i d e c o n t e n t p r o m o t e s t he d i s s o l u t i o n o f

g o l d d ur i n g t he f i r s t 2 4 h o f l e a c h i n g , b u t t he o p t i m um l e a c h i n g k i n e t i c s a r e a t a n

i nt er m e d ia te c y a n i d e c o n c e n t r a t io n , i n th i s c a s e 7 10 m g / L . W o r k i n d ic a t e d tha t t he g o l d

d i s s o l u t i o n r a t e i s a c c e l e r a t e d i n o x y g e n - e n r i c he d s l ur r i e s i n p r e s e n c e o f c ha l c o p y r i t e

Ef fec t o f the

co n cen t ra tio n o f cyan id e

100

80

50 f/' (mg /L)

~ // 1o 500

, , , 40 12 640

' ,~ 3 0 4 710

11 840

2O

10

0 . I ~ I I r J ~ J I L

0 8 16 24 32 40 48

T i m e h )

Fig. 10.

E f f e c t o f c y a n id e c o n c e n t r a t io n o n g o ld l e a c h in g o f a c o p p e r - g o ld o r e . P r e - l e a c h in g :

Pb(NO3) 2 200

g/t, 30

m in ; c y a n id a t io n :

pH 10.5, 02 15 ppm, 48 h.


13/15

G. Desch~n es, P . J .H . Pru d h o m me / I n t. J . Min er . Pro cess . 5 0 (1 9 9 7 ) 1 2 7 -1 4 1

139

and py r r ho t i t e ( L i u and Yen , 1995). I t i s sugges t ed t ha t t he Cu( C N) ~ - l e aches go l d

acco r d i ng t o t he f o l l owi ng equa t i on :

A u + 2 C u ( C N ) ~ - ~ A u ( C N ) 2 + 2 C u ( C N ) 2 + e ( 6 )

I t w ~.s f o u n d t h a t C u ( C N ) 3 - i s m o r e e f f e c t i v e f o r le a c h i n g t h a n C N - ( L a B r o o y e t a l.,

1991) . i [ t i s be l i eved tha t the copper ( I ) cyanide so lu t ions do not show a l imi t ing ra te

because o f t he h i gh a f f i n i t y o f oxy gen f o r coppe r ( I ) wh i ch f ac i l i ta t e s t he oxy gen t r ans f e r

in so lu t ion .

I t was i nd i ca t ed ea r l i e r t ha t t i t r a t i on wi t h s i l ve r n i t r a t e ove r e s t i m a t e s t he am oun t o f

f r ee cyan i de . I n f ac t, the Cu ( CN ) 3 - com pl ex l o se s a m o l ecu l e o f f r ee cyan i de du r i ng

t i tr a t ion , i n a cco r da nce w i th t he f o l l owi ng equ a t ion :

C u ( C N ) ] - --> C u (C N )2 3 - + C N - ( 7 )

The d i s soc i a t i on o f t h i s com pl ex cause s a h i ghe r concen t r a t i on o f f r ee cyan i de . S i nce

t he p l an t u se s t he s am e t i t r a t i on m e t hod , t he va l ue s i n t h i s r epo r t a r e com par ab l e wi t h

t he p r odu c t i on da t a , a s t he e r r o r i nduced i s o f the s am e na t u r e.

4 . D i s c u s s i o n

T h e h i g h c o p p e r c o n t e n t o f t h i s o r e ( 0 . 4 % ) c r e a t e s a k i n e t i c p r o b l e m f o r g o l d

ex t r ac t i on , Th i s exp l a i n s , pa r t l y , why t he add i t i on o f l e ad n i t r a t e and oxygen enhances

go l d d i s so l u t ion and s i gn i f ic an t l y i m pr o ves go l d r ecove r y . Lea d n i t r a te ha s no e f f ec t on

t h e o v e r a ll g o ld e x t ra c t io n w h e n a d d e d i n a m o u n t s h i g h e r th a n 3 0 0 g / t . H o w e v e r , l ea d

n i t r a te i s no t f ou nd t o be e f f i c i en t f o r r educ i ng t he cyan i d e consum pt i on . Th i s e f f ec t is

probab]Ly re la ted to the ver y shor t pre - leac hing p er iod u sed in the cur re nt tes t . A lon ger

p r e - l each i ng wou l d have a pos i t i ve i m pac t on t he cyan i de consum pt i on . I ndeed , t he

r e su lt s i nd i ca t e t ha t l e ad n i t ra t e c an b e a dded du r i ng p r e - l e ach i ng o r d i r ec t l y du r i ng t he

cyan i da t i on wi t hou t any obse r vab l e d i f f e r ence i n f i na l pe r f o r m ance because t he ga i n

c r ea t ed by t he i nc r ea se o f t he go l d ex t r ac t i on i s a t t enua t ed by t he i nc r ea se o f cyan i de

consum ed . I t a l so appea r s t ha t t he k i ne t i c s o f ox i da t i on o f so l ub l e su l ph i des i s no t a

good i nd i ca t i on o f t he l eng t h o f t he p r e - l e ach i ng r equ i r ed t o have a pos i t i ve e f f ec t .

I n go l d p l an t s , t he s t r a t egy o f l e ad n i t r a t e add i t i on i s no t a l ways we l l de f i ned o r

unde r sl :ood ( Desch~nes and P u t z , 1995). Fo r t h is o r e , i t was f o und t ha t t he con cen t r a t i on

o f t h i ocyana t e and coppe r c anno t be u sed a s r e l i ab l e i nd i ca t o r s t o ad j us t t he add i t i on

r a t e. O n t he o t he r hand , t he r edo x po t en t ia l cou l d be u sed a s a gu i de f o r t he l e ad n i tr a t e

add i t i on . A m e t i cu l ous app r oach shou l d be p r ac t i s ed t o s t anda r d i ze t he r ead i ng o f t he

e l ec t r odes u sed i n each l e ach t ank and t o ensu r e avo i d i ng t he d i s t u r bance r e l a t ed t o

con t am i na t i on o f t he e l ec t r o l y t e .

An exces s o f l e ad n i t ra t e is de t r i m en t a l becau se i t inc r ea se s t he cyan i de consum pt i on ,

p r obab l y by ox i d i z i ng cyan i de . Th i s hypo t hes i s i s d i f f i cu l t t o con f i r m because t h i s

e x c e s s h a d n o e f f e c t o n g o l d r e c o v e r y . T h e h i g h c o p p e r c o n t e n t o f t h is o r e j u st i fi e s t h e

h i g h r e q u i r e m e n t o f f r e e c y a n i d e f o r l e a c h i n g . T h e h i g h c o n c e n t r a t i o n o f f r e e c y a n i d e

a l so l e ads t o a h i gh consum pt i on o f t h i s r e agen t . Any concen t r a t i on o f cyan i de be l ow a

c r i t i c a l l eve l , howeve r , m eans a s i gn i f i c an t d r op i n go l d ex t r ac t i on .


14/15

140 G . D e s c h ~ n e s , P .J . H . P r u d h o m m e / l n t . J. M i n e r . P r o c e s s . 5 0 ( 1 9 9 7 ) 1 2 7 - 1 4 1

5 . C o n c l u s i o n s

Ef f i c i en t l e ach i ng o f a f r ee m i l l ing g o l d o r e , wi t h a h i gh co ppe r con t en t , i s a ch i eved

on l y unde r spec i f i c cond i t i ons u s i ng oxygen , l e ad n i t r a t e and a h i gh concen t r a t i on o f

f r ee cyan i de . The k i ne t i c s o f f o r m a t i on o f so l ub l e su l ph i des canno t be u sed a s a d i r ec t

i nd i ca ti on o f t he l eng t h o f t he p r e - l e ach i ng r equ i r ed . T he add i t ion o f l e ad n i t r a te r e su l ts

i n a h i g h e r g o l d r e c o v e r y , a lt h o u g h c y a n i d e c o n s u m p t i o n c a n n o t b e r e d u c e d b e l o w 1 .8 5

k g / t wh en a s soc i a t ed to a go l d ex t r ac t ion o f 97% . T he ex t r ac t i on o f go l d i s no t s ens i ti ve

t o le ad n i tr a t e add i t ion i f an add i t ion h i ghe r t han 300 g / t i s em pl oyed . The r edox

po t en t i a l va lue s co u l d t hus be u sed a s con t r o l pa r am e t e r s f o r l e ad n i tr a t e add i t ion , a t t he

d i f f e r en t s t ages o f cyan i da t i on . Lead n i t r a t e i nh i b i t s t he d i s so l u t i on o f cha l copyr i t e bu t

t he p r e - le ach i ng used was no t e f f i c ien t enoug h t o dec r ea se t he cyan i de consum pt i on .

T h e h i g h c o n c e n t r a ti o n o f c o p p e r in s o l u t io n r e q u ir e s a c o n c e n t r a ti o n o f 7 0 0 m g / L

N a C N f o r le a c h in g .

A c k n o w l e d g e m e n t s

T h e a u t h o r s w i s h t o t h a n k D e n i s C o u t u r e , C l a u d e D u f r e s n e a n d J e a n C h ~ t e a u n e u f o f

Cam bi o r f o r t he i r pa r t i c i pa t i on and co l l abo r a t i on , t he f i nanc i ng p r ov i ded unde r t he

p r o j e c t a n d t h e i n f o r m a t i o n c o n v e y e d . T h a n k s a l s o t o o u r a s s a y l a b o r a t o r y o f M i n i n g

and Mi ne r a l Sc i ences , t o J ean C l ou t i e r f o r t he f i r e a s say , t o G i l l e s La f l am m e and J .T .

Szym ansk i f o r t he m i ne r a l og i ca l ana l ys i s and t o Mar t i n Fo r t i e r , a s t uden t t r a i nee f r om

Laval Univers i ty , for h i s ass i s t ance in the l abora tory t es t s .

R e f e r e n c e s

Desch~nes, G., Putz, A. (Eds.), 1995. The Second Survey of Gold Cyanidation Plants. MSL Report 95-14

(CR), April.

Desch~nes, G., Wallingford, G., 1995. Effect of oxygen and lead nitrate on the cyanidation of a sulphide-bearing

gold ore. Miner. Eng. 8, 8.

Dufresne, C., Desch~nes, G., Cimon, D., 1994. Control of cyanidation at the Yvan V6zina plant. Miner. Eng. 7

(11), 1427-1434.

Goldhaber, M.B., 1983. Experimental study of metastable sulfur oxyanion formation during pyrite oxidation at

pH 6-9 and 30C. Am. J. Sci. 283, 193-217.

Habashi, F., 1967. Kinetics and mechanisms of gold and silver dissolution in cyanide solutions. Bur. Mines

Bull. April, 59.

Hsu, Y.J., Tran, T., 1995. Selective removal of gold from copper-gold cyanide liquors using zinc. Miner. Eng.

9 (1), 1-13.

LaBrooy, S.R., Komosa, T., Muir, D.M., 1991. Selective leaching of gold from copper-gold ores using

ammonia-cyanide mixture. Proc. 5th Extractive Metallurgy Conf., Perth, pp. 127-132.

Lacoste, P., Desch~nes, G., Ghali, E., 1996. Thiourea leaching of a copper gold ore using statistical design.

Hydrometallurgy (in press).

Latimer, W.M., 1938. The Oxidation States of the Elements and their Potential in Aqueous Solutions.

Prentice-Hall, Englewood Cliffs, N.J.

Liu, G.Q., Yen, W.T., 1995. Effect of sulphide minerals and dissolved oxygen on gold and silver dissolution in

cyanide solutions. Miner. Eng. 8 (1/2), 111-123.


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G. Desch~nes, P.J.H. Prud homme / lnt. J. Miner. Process. 50 (1997) 127-141 141

Ma rtin, C.J., Cabri , L.J., 1994. An investigation by T O F-L IM S of the surface co mp osit ion of sulphide

minera ls f rom leaching and e lec t rochemica l exper iments . AM TEL Repor t 94 /3 9 , Aug.

M orrison, R.M., 1994. Factors imp acting on lead nitra te addit ions to cyanidation circuits . M SL Repo rt 94-42

(CR), Nov.

Mo rrison, R.M., 1995 . Investig ation of lead nitra te effects in gold cyanidation circuits . MS L R eport 95-5 (CR),

Feb.

Mu ir , D. , Vukcevic , S. , Shuttleworth, J ., 19 95 . Optim izing the amm on ia-cy anid e leaching process for

coppe:F-gold ores. Proc. Randol Gold Forum, Perth '95, Perth, pp. 225-229.

Stoych evski, M. , W ill iams, L.R. , 1993 . Inf luence of oxygen, h ydrog en peroxide a nd oxone on disso lution of

gold from pyrite ore . Trans. Inst . Min. Metall . C, 93-98.

W eichselbau m, J. , Tum ilty, J .A., Schmidt, C.G. , 198 9. Impro ved gold recovery by cyanidation -- a kinetic

problem. Proc. Extraction Metallurg y '89. I .M.M., L ondo n, pp. 1 0-1 3 July 67 9-6 90 .

Zheng, J . , Ritchie , I .M. , LaBrooy, S.R. , Singh, P. , 1995. Study of gold leaching in oxygenated solutions

contain ing cy an ide -co pp er-a m m on ia using a rotating quartz crystal microbalance. Hydrometallurgy 39,

2 7 7 - 2 9 2 .

cyanidation of a copper gold ore.pdf

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