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The role of arsenic in the homogeneous precipitation of As Sb and Bi impurities incopper electrolyte

Xue-Wen Wang a Qi-Yuan Chen b Zhou-Lan Yin b Ming-Yu Wang a Fang Tang a

a School of Metallurgical Science and Engineering Central South University Changsha 410083 Chinab College of Chemistry and Chemical Engineering Central South University Changsha 410083 China

a b s t r a c ta r t i c l e i n f o

Article history

Received 10 January 2011Received in revised form 24 February 2011

Accepted 18 April 2011

Available online 28 April 2011

Keywords

Copper electrore1047297ning

Electrolyte puri1047297cation

Arsenato antimonic acid

Arsenato antimonate

The role of arsenic in the homogeneous precipitation of impurities arsenic antimony and bismuth in copper

electrolyte was studied Experiments found that though the formation of arsenato antimonates is one of the

control-steps in the homogeneous precipitation and antimony is absolutely necessarily for arsenato

antimonates formation arsenic played an important role for the homogeneous precipitation as well Arsenic

(V) is not only a reactant of arsenato antimonates formation but also an oxidant of Sb(III) oxidation Arsenic

(V) can oxidize antimony from Sb(III)to Sb(V) in copper electrolyte If the concentration of arsenic (V) is over

6 gL and the mole ratio of As(III)As(V) is less than 009 the oxidation can be taken place at room

temperature and the equilibrium value of the φ As(V)As(III) is about 0606 in the electrolyte Under these

conditions the precipitation rate of antimony from the electrolyte can be reached over 97 Arsenic (III) can

promote arsenato antimonates formation and depress 1047298oating slimes formation simultaneously The higher

the arsenic (III) concentration is the easier the formation of arsenato antimonates will be If arsenic (III) is

lack the copper electrolyte is prone to be over oxidized which will result in the formation of 1047298oating slimes

Floating slimes and arsenato antimonates have a similar chemical composition To distinguish arsenato

antimonates from 1047298oating slimes the most effective way was thermal decomposition

copy 2011 Elsevier BV All rights reserved

1 Introduction

In copper electrore1047297ning the impurities of arsenic antimony and

bismuth are dissolved along with copper from the anode to the

electrolyteIf no electrolyte is bled from theelectrore1047297ning circuit the

impurities would gradually accumulate in the electrolyte which

would result in a variety of intolerable problems such as contami-

nation of the cathodes and passivation of the anodes Therefore a

number of methods have been proposed for the puri1047297cation of copper

electrolyte besides the typical treatment such as prevention the

supersaturation of arsenic antimony and bismuth in copper electro-

lyte with stannic acid (Schuize 1972) adsorption antimony and

arsenic from the electrolyte with activated carbon (Navarro and

Alguacil 2002 Toyabe et al 1987) co-precipitation of bismuth and

antimony from the electrolyte by adding a carbonate of barium

strontium or lead (Hyvarinen 1979) removal antimony and bismuth

from the electrolyte using ion exchange resins (Cunnigham et al

1997) extraction of antimony and bismuth from copper electrolyte

with LIX1104SM (Navarro et al 1999) adsorption bismuth and

antimony with an adsorbent containing antimony (Wang et al 2003)

removal bismuth from copper electrolyte solutions using MRT ( Izatt

et al 2010) and separation and concentration arsenic from the

copper electrolyte using electrodialysis (Cifuentes et al 2002)

It is well known that a part of the impurities arsenic antimony and

bismuth dissolved from the anode can spontaneously precipitate from

the electrolyte to the anode slimes during copper electrore1047297ning and

the volume of the copper electrolyte withdrawn to be puri1047297ed per ton

cathode (VPTC) is diverse in different copper re1047297neries Even in the

same re1047297nery with the same anode the VPTC value is not the same

under different electrore1047297ning conditions (Wang 2003) which

indicates that the ef 1047297ciencies of homogeneous co-precipitation of

impurities arsenic antimony and bismuth are different ie the

fraction of arsenic antimony and bismuth dissolved from the anode

and then deposited to form the anode slimes vary under different

electrore1047297ning conditions

It was found that the homogeneous co-precipitation of impurities

arsenic antimony and bismuth in copper electrolyte is dominant in

the forms of arsenato antimonates (Wang et al 2006) and there are

two control-steps in the homogeneous co-precipitation one is the

oxidation of antimony from Sb(III) to Sb(V) and the other is the

formation of arsenato antimonates (Wang et al 2011) Although

antimony is absolutely necessarily for the formation of arsenato

antimonates (Wang et al 2006) recently it was found that arsenic

also plays an important role in the formation of arsenato antimonates

(Wang et al 2011) The aim of this paper is to present the roles of

Hydrometallurgy 108 (2011) 199ndash204

Corresponding author

E-mail address wxwcsu163com (X-W Wang)

0304-386X$ ndash see front matter copy 2011 Elsevier BV All rights reserved

doi101016jhydromet201104007

Contents lists available at ScienceDirect

Hydrometallurgy

j o u r n a l h o m e p a g e w w w e l s ev i e r c o m l o c a t e h yd r o m e t

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arsenic (V) and arsenic (III) respectively in the formation of arsenato

antimonates

2 Experimental

21 Materials apparatus and analysis

To properly understand the role of arsenic in the formation of

arsenato antimonates synthetic and industrial copper re1047297

ningelectrolytes were used Sulfuric acid hydrogen peroxide solution

(30 vol) CuSO4sdot5H2O As2O3 9999 Sb 9999 Bi distilled water

and the powder of arsenato antimonicacid of AAAc(11) were used in

the experiments The AAAc(11) powder contains As 2135 wt and

Sb 3508 wt and the arsenic and antimony in it both are

quinquevalent

The electrolytes used in the experiments contained the basic

components 34ndash36 gL Cu 180ndash185 gL free H2SO4 and the impurities

arsenic antimony and bismuth They were synthesized at about 80 degC

and then placed in beakers for ageing without stirring and thermal

retardation The initial concentration of the synthetic electrolytes is

shown in Table 1 The industrial copper re1047297ning electrolyte was taken

from Guixi smelter and its composition is listed in Table 2

The Sb(III) and Bi(III) added into the electrolytes were respectively

prepared by dissolving metallic antimony and bismuth in concen-

trated sulfuric acid and diluting with water As2O3 was 1047297rstly

dissolved in water under heating and stirring then oxidized with

the hydrogen peroxide solution to obtain As(V) The excess H2O2 was

decomposed by boiling the solution for about half an hour The AAAc

(11) solution was obtained by dissolving the AAAc(11) powder in

distilled water

The composition of experimental samples was determined by

inductively coupled plasma emission spectroscopy (ICP) with a PS-6

PLASMA SPECTROVAC BAIRD (USA) The valence of elements was

determined by standard chemical methods (Chemistry Department and

Hangzhou University 1982) The IR spectrum was obtained using the

KBr disk method with an AVATAR 360 (Nicolet) spectrophotometer

operatingin therangeof 4000ndash400 cmminus1 TGDTGcurves were obtained

on a METTLER TOLEDO Thermogravimetric Analyzer (TGSDTA851e) inthe temperature range of 25ndash1100 degC at a heating rate of 5 degC minminus1

under dynamic argon (70 ml minminus1) atmospheres

3 Results and discussion

31 Oxidation of antimony from Sb(III) to Sb(V)

It is well known that antimony and arsenic dissolve electrochem-

ically from copper anodes as trivalent ions and then are oxidized to

pentavalent ions by the air (O2) dissolved in copper re1047297ning

electrolytes Furthermore As(III) oxidizes before Sb(III) Under

certain conditions the higher the concentration of arsenic is the

faster the oxidation of antimony from Sb(III) to Sb(V) in copper

electrolyte will be (Wang et al 2011)To properly understand the role of arsenic in the oxidation of

antimony from Sb(III) to Sb(V) the prepared Sb(III) andor Bi(III)

were 1047297rst added into the synthetic copper electrolytes under stirring

at above 65 degC to avoid them hydrolyzation and then the prepared As

(V) was added into The electrolytes placed in the beakers with cover

for ageing without stirring and thermal retardation and white

precipitates formed in all the electrolytes during the aging Afteraging for a week 1047297ltration was carried out and the concentrations of

As Sb and Bi in the 1047297ltered electrolytes were listed in Table 3

From Table 1 and Table 3 it can be worked out that after aging the

precipitation rate of antimony in the 4 5 6 7 and 8

electrolytes is over 97 while that in the 1 2 and 3 electrolytes

is below 65 though the initial concentrations of antimony in the

electrolytes were almost the same (about 15 gL Sb see Table 1) at

about 80 degC After the As(V) adding in it was observed that the

temperature of theprecipitates begin to form in the4 5 67 and

8 electrolytes was over 65 degC while that in the 1 2 and 3

electrolytes was below 50 degC When the aged 1 2 and 3

electrolytes were heated over 60 degC under stirring the precipitates

formed in them were dissolved which indicates that the precipitates

formed in the aged 1 2 and 3 electrolytes are Sb(AsO4) (Wang

2003) or amorphous antimonious acid (Petkova 1997) as the

solubility of them increase with temperature increase while the

precipitates formed in the aged 4 5 6 7 and 8 electrolytes

couldnt dissolve even if under boiling

In order to differentiate the precipitates formed in the aged 4 5

6 7 and 8 electrolytes from those formed in the aged 1 2 and

3 electrolytes after 1047297ltration the precipitates were washed with

dilute sulfuric acid and distilled water respectively and then dried at

60 degC under vacuum till their weights were constant Table 4 gave the

compositions of the precipitates formed in 3 and 4 electrolytes

From Table 4 it canbe seen that the precipitatescontain antimony (V)

and the content of antimony (V) in the precipitate formed in 4

electrolyte is much higher than that in the precipitate formed in 3

electrolyte and some of the As(V) was changed into As(III) in the

electrolytes see Table 3 which indicates that some of the Sb(III) wasoxidized to Sb(V) by the added As(V) The precipitate formed in 4

electrolyte should be arsenato antimonates because the precipitate

couldnt dissolve under boiling The formation of arsenato antimo-

nates in the electrolyte can be expressed by the following equations

(Wang et al 2006)

H3AsO4 thorn SbOthorn

thorn 3H2O frac14 HAsO2 thorn Hfrac12SbethOHTHORN6 thorn Hthorn

eth1THORN

aH3AsO4 thorn bHfrac12SbethOHTHORN6

thorn cMeOthornrarrMecAsaSbbOeth3athorn5bthornc=2thorn1THORNHethathorn5bminus2cthorn2THORNbullxH2O thorn cH

thorn

thorn etha thorn b thorn c=2minus1minusxTHORNH2O where Me

frac14 AsethIIITHORN BiethIIITHORN and SbethIIITHORN age1bge1 cleeth3a thorn bTHORN eth2THORN

The IR spectrum of the precipitate formed in the 4 electrolyte is

shown in Fig 1 where the main bands can be respectively assigned

to νs and νas of OndashH (34037 and 16313 cmminus1) (Losilla et al 1998) δ

of OndashH (13832 and 13495 cmminus1) (Naiumlli and Mhiri 2001) δ of AsndashOH

Table 1

Initial concentrations of impurities As Sb and Bi in the synthetic copper electrolytes gL

Electrolytes 1 2 3 4 5 6 7 8

As 0000 4021 5009 6013 7050 8078 9042 10002

Sb 1550 1548 1544 1558 1542 1536 1532 1533

Bi ndash 0505 ndash ndash 0524 ndash ndash 0544

Cu 3412 3527 3574 3465 3568 3485 3601 3586

H2SO4 1814 1837 1845 1828 1847 1808 1842 1837

Table 2

Composition of industrial copper re1047297ning electrolyte gL

Cu H2SO4 As(III) As(V) Sb(III) Sb(V) Bi

4671 18468 054 497 042 007 032

200 X-W Wang et al Hydrometallurgy 108 (2011) 199ndash 204

7232019 ismuto 6

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and SbndashOH (11266 cmminus1) (Naiumlli and Mhiri 2001 Qureshi and

Kumar 1971) νas of AsndashOH (10316 cmminus1) (Colomban et al 1989)

νas of As-OX(X= AsSb) (8169 cmminus1) (Myneniet al 1998) νas ofSbndash

OH (6186 cmminus1) and νas of SbndashOY(Y= As Sb) (5026 cmminus1)

(Colomban et al 1989 Qureshi and Kumar 1971) There are AsndashOndash

Sb SbndashOndashSb bonds formed among As(V) As(III) Sb(V) and Sb(III) in

the precipitate which are the characteristic bands of arsenato

antimonates (Chen et al 2004) Therefore the precipitates formed

in the 4 electrolyte is arsenato antimonates so are the precipitates

formed in 5 6 7 and 8 electrolytes

From reactions (1) and (2) it can be seen that arsenic (V) is not

only an oxidant forantimonyoxidation from Sb(III) to Sb(V) butalso a

reactant for arsenato antimonates formation in copper electrolyte

The concentration relationship between the arsenic (V) and the

antimony in the aged electrolytes was shown in Fig 2 As seen in

Fig 2 theconcentration of antimony declined sharply when the As(V)

concentration is over 45 gLin theaged electrolytes From Table 1 and

Table 4 it can be found that Sb(III) can be obviously oxidized to Sb(V)

by As(V) when the initial As(V) concentration was more than 6 gL in

the electrolytes

Under normal conditions it is dif 1047297cult for arsenic (V) to oxidize

antimony from Sb(III) to Sb(V) because the difference of the standard

electrode potentialsφ o

As(V)As(III) (0559 V) and φ o

Sb(V)Sb(III) (0720 V) is

over015 V (Dean1985) However when Sb(V) andAs(V)reactwith As

(III) Sb(III) and Bi(III)to form the precipitates of arsenato antimonates

the concentration of Sb(V) decreases remarkably in the electrolyte and

the φ Sb(V)Sb(III) becomes less than or equal to the φ As(V)As(III) thus

arsenic (V) can oxidize antimony from Sb(III) to Sb(V) in copper

electrolyteThe relationship between the As(III)As(V) mole ratio and the

antimony concentration in the aged electrolytes was given in Fig 3 As

seen in Fig 3 the concentration of antimony increasedrapidly when the

value of As(III)As(V) mole ratio was higher than 009 in the 1047297nal

solutions in other words the formation of arsenato antimonates made

antimony concentration decreased rapidly under the1047297nal As(III)As(V)

mole ratio less than 009 which means that As(III)As(V) mole ratio 009

is near theequilibriumvaluethat arsenic (V)can oxidizeantimonyfrom

Sb(III) to Sb(V) in copper electrolyte at room temperature or the

equilibrium value of the φ As(V)As(III) and φ Sb(V)Sb(III) both are about

0606 if the concentration is close to the activity for As(III) and As(V)

respectively in the electrolyte In fact reaction (1) could take place in all

the electrolytes listed in Table 1 except the 1 electrolyte when the

prepared As(V) was added into but only the formation of arsenatoantimonates can promote reaction (1) proceeding till Sb(III) concen-

tration very little

It was found that by heating the aged 6electrolyte at 85 degC under

stirring for about 05 h the precipitates formed in it were turned from

arsenato antimonates into antimonate The XRD pattern of the

antimonate was shown in Fig 4 This further con1047297rmed that arsenic

(V) can oxidize antimony from Sb(III) to Sb(V) in copper electrolyte

Above experimental results indicate that the oxidation of

antimony from Sb(IIII) to Sb(V) by As(V) depends on not only the

concentration of As(V) but also on the mole ratio of As(III)As(V) and

the temperature of copper electrolyte Thus it can be seen that the

oxidation of antimony from Sb(IIII) to Sb(V) during copper electro-

re1047297ning can follow the indirect oxidation mechanism namely the

oxidation of arsenic from As(III) to As(V) by the air (O2) dissolved in

the re1047297ning electrolyte and the subsequent oxidation of antimony

from Sb(IIII) to Sb(V) by the As(V)

32 Prevention copper electrolyte over oxidation

During test it was found that by adding suf 1047297cient hydrogen

peroxide solution into the aged 3 electrolytes (listed in Table 3) to

oxidize the Sb (III) only about 40 of the antimony was precipitated

in the form of arsenato antimonates After 1047297ltrating the electrolyte

was boiled for half an hour and some suspending white precipitates

appeared and then the white precipitates were separated from the

electrolyte by 1047297ltration again The 1047297lter cake was dried at 60 degC under

vacuumtill its weight was constant and its chemicalcompositionwasanalyzed The analyses results showed that the 1047297lter cake contains As

(V) 1798 wt and Sb(V) 3726 wt It is interesting that the 1047297lter

cake can be dissolved in distilled water at about 50 degC under stirring

which indicates that the electrolyte was over oxidized and the

arsenato antimonic acid of AAAc(11) was formed in it (Wang et al

2004a) The AAAc(11) has the structure of (HO)3AsndashOndashSb(OH)4ndashOndash

Sb(OH)4ndashOndashAs(OH)3 and the suspending precipitates are the hydro-

lyzates of AAAc(11) (Wang et al 2004a Wang et al 2005) The

Table 3

Concentrations of the impurities in the electrolytes listed in Table 1 after ageing gL

Electrolytes 1 2 3 4 5 6 7 8

As(V) 00 2846 3821 4589 5541 7030 7397 10461

As 00 3333 4 359 4973 5 900 7 440 7 884 1 1025

Sb 0660 0 654 0 544 0038 0 037 0 030 0 021 0019

Bi ndash 0476 ndash ndash 0135 ndash ndash 0116

Table 4

Compositions of the precipitates formed in 3 and 4 electrolytes wt

Samples As As(V) Sb Sb(V)

3 2723 2586 4785 030

4 2612 2498 4351 473

4000 3000 2000 1000

20

40

60

80

100

5 0 2

5 6

6 1 8 5

7

8 1 6

9 0

1 0 3 1

5 6

1 1 2 6

6 2

1 3 4 9

4 9

1 3 8 3

1 8

1 5 9

7

0 0

1 6 3

1

2 7

3 4 0 3 6

5

T r a n s m i t t a n c e

Wavenumbers (cm-1)

Fig 1 IR spectrum of the precipitates formed in 4 electrolyte

4 6 8 1000

02

04

06

S b g L

- 1

As(V) gL-1

Fig 2 Effect of As(V)concentration on antimony concentration in the aged electrolytes

201 X-W Wang et al Hydrometallurgy 108 (2011) 199ndash 204

7232019 ismuto 6

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and SbndashOH (11266 cmminus1) (Naiumlli and Mhiri 2001 Qureshi and

Kumar 1971) νas of AsndashOH (10316 cmminus1) (Colomban et al 1989)

νas of As-OX(X= AsSb) (8169 cmminus1) (Myneniet al 1998) νas ofSbndash

OH (6186 cmminus1) and νas of SbndashOY(Y= As Sb) (5026 cmminus1)

(Colomban et al 1989 Qureshi and Kumar 1971) There are AsndashOndash

Sb SbndashOndashSb bonds formed among As(V) As(III) Sb(V) and Sb(III) in

the precipitate which are the characteristic bands of arsenato

antimonates (Chen et al 2004) Therefore the precipitates formed

in the 4 electrolyte is arsenato antimonates so are the precipitates

formed in 5 6 7 and 8 electrolytes

From reactions (1) and (2) it can be seen that arsenic (V) is not

only an oxidant forantimonyoxidation from Sb(III) to Sb(V) butalso a

reactant for arsenato antimonates formation in copper electrolyte

The concentration relationship between the arsenic (V) and the

antimony in the aged electrolytes was shown in Fig 2 As seen in

Fig 2 theconcentration of antimony declined sharply when the As(V)

concentration is over 45 gLin theaged electrolytes From Table 1 and

Table 4 it can be found that Sb(III) can be obviously oxidized to Sb(V)

by As(V) when the initial As(V) concentration was more than 6 gL in

the electrolytes

Under normal conditions it is dif 1047297cult for arsenic (V) to oxidize

antimony from Sb(III) to Sb(V) because the difference of the standard

electrode potentialsφ o

As(V)As(III) (0559 V) and φ o

Sb(V)Sb(III) (0720 V) is

over015 V (Dean1985) However when Sb(V) andAs(V)reactwith As

(III) Sb(III) and Bi(III)to form the precipitates of arsenato antimonates

the concentration of Sb(V) decreases remarkably in the electrolyte and

the φ Sb(V)Sb(III) becomes less than or equal to the φ As(V)As(III) thus

arsenic (V) can oxidize antimony from Sb(III) to Sb(V) in copper

electrolyteThe relationship between the As(III)As(V) mole ratio and the

antimony concentration in the aged electrolytes was given in Fig 3 As

seen in Fig 3 the concentration of antimony increasedrapidly when the

value of As(III)As(V) mole ratio was higher than 009 in the 1047297nal

solutions in other words the formation of arsenato antimonates made

antimony concentration decreased rapidly under the1047297nal As(III)As(V)

mole ratio less than 009 which means that As(III)As(V) mole ratio 009

is near theequilibriumvaluethat arsenic (V)can oxidizeantimonyfrom

Sb(III) to Sb(V) in copper electrolyte at room temperature or the

equilibrium value of the φ As(V)As(III) and φ Sb(V)Sb(III) both are about

0606 if the concentration is close to the activity for As(III) and As(V)

respectively in the electrolyte In fact reaction (1) could take place in all

the electrolytes listed in Table 1 except the 1 electrolyte when the

prepared As(V) was added into but only the formation of arsenatoantimonates can promote reaction (1) proceeding till Sb(III) concen-

tration very little

It was found that by heating the aged 6electrolyte at 85 degC under

stirring for about 05 h the precipitates formed in it were turned from

arsenato antimonates into antimonate The XRD pattern of the

antimonate was shown in Fig 4 This further con1047297rmed that arsenic

(V) can oxidize antimony from Sb(III) to Sb(V) in copper electrolyte

Above experimental results indicate that the oxidation of

antimony from Sb(IIII) to Sb(V) by As(V) depends on not only the

concentration of As(V) but also on the mole ratio of As(III)As(V) and

the temperature of copper electrolyte Thus it can be seen that the

oxidation of antimony from Sb(IIII) to Sb(V) during copper electro-

re1047297ning can follow the indirect oxidation mechanism namely the

oxidation of arsenic from As(III) to As(V) by the air (O2) dissolved in

the re1047297ning electrolyte and the subsequent oxidation of antimony

from Sb(IIII) to Sb(V) by the As(V)

32 Prevention copper electrolyte over oxidation

During test it was found that by adding suf 1047297cient hydrogen

peroxide solution into the aged 3 electrolytes (listed in Table 3) to

oxidize the Sb (III) only about 40 of the antimony was precipitated

in the form of arsenato antimonates After 1047297ltrating the electrolyte

was boiled for half an hour and some suspending white precipitates

appeared and then the white precipitates were separated from the

electrolyte by 1047297ltration again The 1047297lter cake was dried at 60 degC under

vacuumtill its weight was constant and its chemicalcompositionwasanalyzed The analyses results showed that the 1047297lter cake contains As

(V) 1798 wt and Sb(V) 3726 wt It is interesting that the 1047297lter

cake can be dissolved in distilled water at about 50 degC under stirring

which indicates that the electrolyte was over oxidized and the

arsenato antimonic acid of AAAc(11) was formed in it (Wang et al

2004a) The AAAc(11) has the structure of (HO)3AsndashOndashSb(OH)4ndashOndash

Sb(OH)4ndashOndashAs(OH)3 and the suspending precipitates are the hydro-

lyzates of AAAc(11) (Wang et al 2004a Wang et al 2005) The

Table 3

Concentrations of the impurities in the electrolytes listed in Table 1 after ageing gL

Electrolytes 1 2 3 4 5 6 7 8

As(V) 00 2846 3821 4589 5541 7030 7397 10461

As 00 3333 4 359 4973 5 900 7 440 7 884 1 1025

Sb 0660 0 654 0 544 0038 0 037 0 030 0 021 0019

Bi ndash 0476 ndash ndash 0135 ndash ndash 0116

Table 4

Compositions of the precipitates formed in 3 and 4 electrolytes wt

Samples As As(V) Sb Sb(V)

3 2723 2586 4785 030

4 2612 2498 4351 473

4000 3000 2000 1000

20

40

60

80

100

5 0 2

5 6

6 1 8 5

7

8 1 6

9 0

1 0 3 1

5 6

1 1 2 6

6 2

1 3 4 9

4 9

1 3 8 3

1 8

1 5 9

7

0 0

1 6 3

1

2 7

3 4 0 3 6

5

T r a n s m i t t a n c e

Wavenumbers (cm-1)

Fig 1 IR spectrum of the precipitates formed in 4 electrolyte

4 6 8 1000

02

04

06

S b g L

- 1

As(V) gL-1

Fig 2 Effect of As(V)concentration on antimony concentration in the aged electrolytes

201 X-W Wang et al Hydrometallurgy 108 (2011) 199ndash 204

7232019 ismuto 6

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formation of the hydrolyzates in the electrolyte can be expressed by

the following equations (Wang 2003 Wang et al 2005)

H3AsO4 thorn HSbethOHTHORN5 frac14 Hfrac12H2AsO3ndashOndashSbethOHTHORN5 thorn H2O eth3THORN

2Hfrac12H2AsO3 ndashOndashSbethOHTHORN5frac14 ethHOTHORN3AsndashOndashSbethOHTHORN4 ndashOndashSbethOHTHORN4 ndashOndashAsethOHTHORN3 thorn H2O eth4THORN

AAAc(11)+H2OrarrH thorn

(HO)3AsndashOndashSb(OH)4ndashOndashSb(OH)5H+ H3AsO4 (5)

(HO)3As ndashOndashSb(OH)4ndashOndashSb(OH)5H + H2O rarrH thorn

HSb(OH)5ndashOndashSb

(OH)5H +H3AsO4 (6)

afrac12HSbethOHTHORN5 ndashOndashSbethOHTHORN5Hthorn bfrac12ethHOTHORN3AsndashOndashSbethOHTHORN4 ndashOndashSbethOHTHORN5HrarrethH3AsO4THORN

bSb2ethathornbTHORNOethathornbthorncTHORN

ethOHTHORNeth10athorn9bminus2cTHORNHeth2athornbTHORN thorn cH2O where age0 bge0 etha thorn bTHORNge2 cge1

eth7THORN

The hydrolyzation of AAAc(11) is harmful for cathode copper

quality as the essential component of the hydrolyzates is antimony

(V) which has a good adsorbability for the impurities arsenic

antimony and bismuth in copper electrolyte (Wang et al 2003)

When some of the impurities were adsorbed by the hydrolyzates the

so-called1047298oatingslimes were formedin the electrolyte (Wang 2003)

To con1047297rm that the formation of 1047298oating slimes is caused by the

hydrolyzation of AAAc(11) in copper electrolyte the industrial

electrolyte was placed in a beaker with cover under stirring and

external polarization in a thermostatic water bath Maintaining the

temperature at about 65 degC the AAAc(11) solution was slowly

dropped in the electrolyte till white precipitates appeared After

ageing for 24 h 1047297ltration was performed The compositions of the

1047297ltrate and the 1047297lter cake were listed in Table 5 The composition of

the 1047298

oating slimes obtained by 1047297

ltering the electrolyte of DayeSmelter copper electrore1047297ning circulating systemwas listed in Table 5

as well It can be seen that the 1047298oating slimes and the hydrolyzates

formed in the electrolyte have the similar chemical composition

which indicates that they might be the same compounds and

antimony (V) is the essential component of 1047298oating slimes (Abe and

Takasawa 1987)

Commercial operations found that when arsenic concentration

was below 5 gL the amount of 1047298oating slimes formed in copper

electrolyte increases obviously This indicates that the copper

electrolyte is easy to be over oxidized if the anode is shot of arsenic

(Baltazar et al 1987 Noguchi et al 1995) In order to reduce 1047298oating

slimes formation the most effective way is to improve the

homogeneous co-precipitation of impurities arsenic antimony and

bismuth in copper electrolyte (Wang et al 2011) ie the most

effective way is to speed-up the formation of arsenato antimonates

From reactions (1) to (4) it can be seen that the formations of

arsenato antimonates and arsenato antimonic acid AAAc(11) are

competitive for impurities arsenic antimony and bismuth in copper

electrolyte Arsenic (III) is one of the reactants of reaction (2)

Quantum chemical calculations showed that the reaction of H3AsO4

and HSb(OH)6 with As(III) to form arsenato antimonates is more

easily than that with Sb(III) or Bi(III) (Chen et al 2004) that is to say

arsenic (III) plays an important role for the formation of arsenato

antimonates as well By increasing arsenic concentration the

formation of arsenato antimonates can be improved provided that

the mole ratio of SbAsBi in the anode is suitable for arsenato

antimonates formation (Wang et al 2011) as maintaining the mole

ratio of As(III)As(V) constant the concentration of arsenic (III)

increases with the total arsenic concentration increaseAlthough1047298oating slimes are by-products of copper electrore1047297ning

and a lot of 1047298oating slimes formed in copper electrolyte might not be

encountered for several years under normal conditions because

arsenic (III) is generated constantly during copper electrore1047297ning

which not only avoids the copper electrolyte over oxidation but also

speeds-up the formation of arsenato antimonates However in 1987

and 1988 this was occurred two times in Guixi Smelter copper

electrore1047297ning cells The 1047298oating slimes not only 1047298oated on the

surface of the cells but also suspended in the electrolyte and a lot of

knots were formed on the surface of the cathodes (Wu 1988) By

investigation it was found that the 1047298oating slimes formation derived

from the addition of the decoppered solution of copper anode slimes

to the circulating system The added solution contained 25ndash35 gL Cu

01ndash25 gL Se(IV) and 05ndash20 gL Te(IV) The H2SeO3 and H2TeO3 canoxidize not only arsenic from As(III) to As(V) but also antimony from

Sb(III) to Sb(V) completely which suggests that the added solution

made the electrolyte over oxidation This further shows that it is

dif 1047297cult to avoid 1047298oating slimesformation with the lack of arsenic (III)

000 003 006 009 012 015 01800

02

04

06

S b c o

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

Mole ratio of As(III)As(V)

Fig 3 Effect of As(III)As(V) mole ratio on antimony concentration in the aged

electrolytes

Fig 4 XRD pattern of the precipitates formed in 7 electrolyte by heating at 85 degC

under stirring for about 05 h

Table 5

Compositions of the 1047298oating slimes formed in commercial copper electrore1047297ning

electrolyte and the precipitate obtained by making AAAc(11) hydrolyzed in the

electrolyte listed in Table 2 and then 1047297ltering

As(V) As(III) Sb(V) Sb(III) Bi Cu H2SO4

Filtrate gL 552 038 038 012 025 4654 18612

Filter cake wt 981 316 4173 587 138 010 ndash

Floating slimes wt 8 7 6 0 57 3 724 4 5 5 7 7 4 ndash ndash

202 X-W Wang et al Hydrometallurgy 108 (2011) 199ndash 204

7232019 ismuto 6

httpslidepdfcomreaderfullismuto-6 56

in copper electrolyte In order to minimize the formation of 1047298oating

slimes partial arsenic was reduced from As(V) to As(III) (Braun et al

1976 Petkova 1997) or the solution containing arsenic (III) was

added into the copper electrolyte (Demaerel 1987 Xiao et al 2007)

to enhance the homogeneous co-precipitation of impurities arsenic

antimony and bismuth in copper electrolyte and the concentration of

arsenic is maintained over 7 gL in many copper re1047297neries This

indicates that maintaining arsenic (III) suf 1047297cient can effectively

prevent 1047298

oating slimes formation in copper electrolyte

33 Distinction between 1047298oating limes and arsenato antimonates

The 1047298oatingslimes andthe arsenato antimonates formedin copper

electrolytes both contain As(V) As(III) Sb(V) Sb(III) and Bi(III) and

they are both white amorphous precipitates and have no 1047297xed

composition (Wang 2003 Wang et al 2006) Therefore to

differentiate 1047298oating limes from arsenato antimonates is necessary

Thermal decomposition is one of the most effective ways used to

distinguish the amorphous solids Fig 5 shows the TGDTG curves for

the thermal decomposition of AAAc(11)(Wang et al 2005) arsenato

antimonates (Wang et al 2004b) and the 1047298oating slimes listed in

Table 5 Fig 5a showed that the curve of AAAc(11) decomposition

process is divided into four stages The 1047297rst which occurs from 25 degC

to ~200 degC is attributed to the dehydration till three and a half H2O

molecules A clear plateau is reached at about 210 degC when the

decomposed product of As2O5bullSb2O5bull35H2O was formed The second

stage occurs from ~350 degC to ~410 degC which could be inferred to the

reaction of As2O5bullSb2O5bull35H2Orarr2AsSbO4+35H2Ouarr+O2uarr The sec-

ond clear plateau is reached above 410 degC with the existence of

AsSbO4 The third stage occurs between ~ 870 degC and ~ 975 degC which

corresponds to the reaction of 2AsSbO4rarrSb2O3+As2O3uarr+O2uarr The

fourth stage is caused by Sb2O3 evaporation

Although 1047298oating slimes are the hydrolyzed products of AAAc(11)

their TGDTG curves are not the same in Fig 5b not only the 1047297rst stage

vanished but also the second stage diminished markedly because many

(HO)3As- and HO-groups were lost through the reactions (5) (6) and

(7) In Fig 5c the 1047297rst and second stages all vanished as there are few

HO-groups and no (HO)3As-groups in the arsenato antimonatesMoreover the positions and the shapes of the third stage are

different among the three TGDTG curves In Fig 5a AsSbO4 is a pure

substance it has a 1047297xed decomposition temperature and the As2O3 is

very easy to be volatilized at about 975 degC so the DTG curve is very

sharp at the temperature In Fig 5c the stage occurs between ~682 degC

and ~738 degC which could be inferred to the reactions of As2O5rarr-

As2O3+O2 Sb2O3+O2rarrSb2O5 Sb2O3+Sb2O5rarr2Sb2O4 As2O3+

Sb2O5rarr2AsSbO4 Bi2O3+Sb2O5rarr2BiSbO4 (Wang et al 2004b) The

TGcurve for the stage is similar to a polygonal line which isdue to not

only the As2O3 quick-volatilizing but also the structure of As(III) Sb

(III) and Bi(III) linking directly with Sb(V) and As(V) through O

bands in the arsenato antimonates because the reactions of the As(V)

with the Sb(III) and the Sb(V) with the As(III) Sb(III) or Bi(III) are

very easy to carry out at 682ndash738 degC In Fig 5b the third stage showsthat the similar reactions were occurred in the 1047298oating slimes as the

composition of the 1047298oating slimes is similar to that of the arsenato

antimonates and the reaction temperatures are almost the same at

the stage but the As(III) Sb(III) and Bi(III) in the1047298oating slimes were

adsorbed by the surface of AAAc(11) hydrolyzates most of the

adsorbed As(III) Sb(III) and Bi(III) cant react with the Sb(V) and As

(V) till they diffuse to the inner of the hydrolyzates which made the

reactions speed slow and the TGDTG curves of the 1047298oating slimes at

the stage be different from that of the arsenato antimonates

4 Conclusion

Arsenic (V) and arsenic (III) are both important for the formation

of arsenato antimonates in copper electrolyte When the arsenic (V)

concentration is over 6 gL and the mole ratio of As(III)As(V) is less

than about 009 the oxidation of antimony from Sb(III) to Sb(V) by As

(V) can occur in copper electrolyte and the equilibrium value of the

φ Sb(V)Sb(III) is about 0606 in the electrolyte Under these conditions

the precipitation rate of antimony from the electrolyte can be reached

over 97 Maintaining the mole ratio of As(III)As(V) constant the

increase of arsenic (III) concentration can improve the combination of

the Sb(V) with As(V) As(III) Sb(III) and Bi(III) to form the precipitate

of arsenato antimonates By increasing arsenic concentration the

homogeneous co-precipitation of impurities arsenic antimony and

bismuth can be promoted obviously provided that arsenic (III) in

copper electrolyte is suf 1047297cient and the mole ratio of SbAsBi in the

anode is suitable for arsenato antimonates formation which is the

most ef 1047297cient way to prevent 1047298oating slimes formation

0 200 400 600 800 1000

9

18

27

36

Temperature (oC)

W

e i g h t ( m g )

TG

-08

-06

-04

-02

00

02

d w

d t ( m g o C - 1 )

DTG

50 100 150 200

372

384

396

a

0 200 400 600 800 1000

0

10

20

30

40

Temperature (oC)

W e i g h

t ( m g )

TG

-025

-020

-015

-010

-005

000

005

d w d t ( m g o C - 1 )

DTG

b

0 200 400 600 800 1000

4

5

6

7

8

9

TemperatureoC

W i g h t m g

TG

-0012

-0010

-0008

-0006

-0004

-0002

0000

0002

d w d t m g o C

- 1

DTG

c

Fig 5 TG and DTG curves for the thermal decomposition of AAAc(11) 1047298oating slimes

and arsenato antimonates a AAAc(11) b 1047298oating slimes c arsenato antimonates

203 X-W Wang et al Hydrometallurgy 108 (2011) 199ndash 204

7232019 ismuto 6

httpslidepdfcomreaderfullismuto-6 66

Acknowledgement

The authors acknowledge 1047297nancial support from the National

Natural Science Foundation of China (No 50274075)

References

Abe S Takasawa Y 1987 Prevention of 1047298oating slimes precipitation in copperelectrore1047297ning In Hoffmann JE Bautista RG Ettel VA Kudryk V Wesely RJ

(Eds)The Electrore1047297ningand Winningof CopperTMS WarrendalePA USApp 87ndash

98Baltazar V Claessens PL Thiriar J 1987 Effect of arsenic and antimony in copperelctrore1047297ningIn Hoffmann JEBautistaRG EttelVA KudrykV WeselyRJ (Eds)The Electrore1047297ning and Winning of Copper TMS Warrendale PA USA pp 173ndash195

Braun TB Rawling JR Richards KJ 1976 Factors affecting the quality of electrore1047297ning cathode copper In YannopoulosJC Agarwal JC(Eds) ExtractiveMetallurgy of Copper vol I Metallurgical Society of AIME New York pp 511 ndash524

Chemistry Department Hangzhou University 1982 Chemical Analysis (AnalyticalChemistry Handbook Part II) Chemical Industry Press Beijing in Chinese

Chen QY Wang XW Yin ZL Zhang PM Hu HP 2004 Mechanism of ArsenatoAntimonates formation during copper electrore1047297ning In Lan XZ Zhao XC(Eds) Abstract Compile of ICHM p 35 Xian

Cifuentes L Crisoacutestomo G Ibaacutentildeez JP Casas JM Alvarez F Cifuentes G 2002 Onthe electrodialysis of aqueous H2SO4ndashCuSO4 electrolytes with metallic impurities

J Membr Sci 207 1ndash16Colomban PH Doremieux-Morin C Piffard Y Limage MH Novak A 1989

Equilibrium between protonic species and conductivity mechanism in antimonicacid H2Sb4O11bullnH2O J Mol Struct 213 83ndash96

Cunnigham RM Calara JV King MG 1997 In Mishra B (Ed) EPD Congress TMS

Warrendale PA USA pp 453ndash460Dean JA 1985 Langess Handbook of Chemistry ed 13 McGraw-Hill IncDemaerel JP 1987 The behavior of arsenic in the copper electrore1047297ning process In

Hoffmann JE Bautista RG Ettel VA Kudryk V Wesely RJ (Eds) TheElectrore1047297ning and Winning of Copper TMS Warrendale PA USA pp 195ndash210

Hyvarinen OVJ 1979 Process for selective removal of bismuth and antimony from anelectrolyte especially in electrolytic re1047297ning of copper US Patent No 4157946

IzattSRIzatt NE Dale JB Bruening RL2010MRT usein copperre1047297ning bismuthremoval fromcopper electrolyte solutions Proceedingsof Copper 2010ConferenceHamburg Germany

Losilla ER Salvadoacute MA Aranda MAG Cabeza A Pertierra P Garcia-Granda SBruque S 1998 Layered acid arsenates α-M(HAsO4)2bullH2O (M=Ti Sn Pb)synthesis optimization and crystal structures J Mol Struct 470 93 ndash104

Myneni SCB Traina SJ Waychunas GA Logan TJ 1998 Experimental andtheoretical vibrational spectroscopic evaluation of arsenate coordination inaqueous solutions solids and at mineral-water interfaces Geochim CosmochimActa 62 3285ndash3300

Naiumlli H Mhiri T 2001 X-ray structural vibrational and calorimetric studies of a newrubidium pentahydrogen arsenate RbH5(AsO4)2 J Alloys Comp 315 143ndash149

Navarro P Alguacil FJ 2002 Adsorption of antimony and arsenic from a copperelectrore1047297ning solution onto activated carbon Hydrometallurgy 66 101 ndash105

Navarro P Simpson J Alguacil FJ 1999 Removal of antimony(III) from copper insulphuric acid solutions by solvent extraction with LIX 1104SM Hydrometallurgy53 121ndash131

Noguchi F Itoh H Nakamura T 1995 Effect of impurities on the quality of electrore1047297ned cathode copper behavior of antimony in the anode In Proc of Copper 1995 Vol 3 337ndash348

Petkova EN 1997 Mechanisms of 1047298oating slime formation and its removal with the

help of sulphur dioxide during the electrore1047297ning of anode copper Hydrometal-lurgy 46 277ndash286Qureshi M Kumar V 1971 Synthesis and IR X-ray and ion-exchange studies of some

amorphous and semicrystalline phases of titanium antimonateSeparation of VO2+

from various metal ions J Chromatogr A 62 (3) 431 ndash438Schuize R 1972 Process for preventing supersaturation of electrolytes with arsenic

antimony and bismuth US Patent No 3696012Toyabe K Toyabe K Segawa CH Sato H 1987 Impurity control of electrolyte at

Sumitomo Niihama Copper Re1047297nery In Hoffmann JE Bautista RG Ettel VAKudryk V Wesely RJ (Eds) The Electrore1047297ning and Wining of Copper TheMetallurgical Society Pennsylvania USA pp 117ndash128

Wang XW 2003 Study on the mechanism of the formation and action of arsenatoantimonic acid in copper electrore1047297ning Central South University doctoral thesisChangsha (in Chinese)

Wang XW Chen QY Yin ZL Zhang PM Long ZP Su ZF 2003 Removal of impurities from copper electrolyte with adsorbent containing antimony Hydro-metallurgy 69 39ndash44

Wang XW Chen QY Yin ZL Zhang PM Zhang QX He YH 2004a Discovery of arsenato antimonic acid J Cent South Univ (Science and Technology) 35 (supple 1)

130ndash133 in ChineseWang XW Chen QY Yin ZL Li YG 2004b Study on the thermochemical behavior

of arsenato antimonates Book of Abstracts of The 18th IUPC InternationalConference on Chemical Thermodynamics and The 12th national Conference onChemical Thermodynamics and Thermal Analysis Beijing p 342

Wang XW Chen QY Yin ZL Zhang PM Wang YW 2005 Synthesis andcharacterization of the arsenato antimonic acid of AAAc(11) Journal of CentralSouth University of Technology 12 (Supple 1) 76ndash81

Wang XW Chen QY Yin ZL Xiao LS 2006 Identi1047297cation of arsenato antimonatesin copper anode slimes Hydrometallurgy 84 211 ndash217

Wang XW Chen QY Yin ZL Wang MY Xiao BR Zhang F 2011 Homogeneousprecipitation of As Sb and Bi impurities in copper electrolyte during electrore1047297n-ing Hydrometallurgy 105 355ndash358

Wu JL 1988 Re1047298ection on the twice technical 1047298uctuation Copper Flash Smelting (2)9ndash15 in Chinese

Xiao FX Zheng YJ Wang Y Xu W Li CH Jian HS 2007 Novel technology of puri1047297cation of copper electrolyte TransNonferrous MetSoc China17 1069ndash1074

204 X-W Wang et al Hydrometallurgy 108 (2011) 199ndash 204