95

BEHAVIOR OF ANTIMONY AND ARSENIC IN SULFURIC ACID SOLUTION

ABSTRACT

CHOKO TEREZA ITO 1

TADAHISA NISHIMURA KASUTERU TOZAWA 1

The presence of antimony and arsenic in many mineral sulfides leads to a need to understand the way in which both species react in those processes which have been developed for extracting valuable elements from those minerals.

This paper deals ｾｮ＠ particular with the precipitation reactions of antimonious, antimonic, arsenious and arsenic species in sulfuric acid solution in relation to various hydranetàllurgical processes.

The system Sb20 (x:3,5) - As 2o (y:3,5) - so3-H2o has been investigated ｯｶｾｲ＠ a wide range Óf sulfuric ac1d concentration. The solubility and stability ranges of Sb203 , Sb2o5 , As 2o3 aad compounds formed in the system have been deEermineà at 25 C. Furthermore, the behavior of antimony and arsenic in sulfuric acid solution is discussed.

1 Research Institute of Mineral Dressing and Metallurgy (SENKEN) Tohoku University Sendai, Japan

96

BEHAVIOR OF ANTIMONY AND ARSENIC IN SULFURIC ACID SOLUTION

by Choko Tereza Ito, Tadahisa Nishimura

and Kazuteru Tozawa

Research Institute of Mineral Dressing

and Metallurgy (SENKEN)

Tohoku University

Sendai, Japan

ABSTRACT

The presence of antimony and arsenic in many mineral sulfides

leads to a need to understand the way in which both species react

in tho se processes which have been developed for extracting

valuable elements from those minerals.

This paper deals in particular with the precipitation reactions

of antimonious, antimonic, arsenious and arsenic species in

sulfuric acid solution in relation to various hydrometallurgi cal

processes.

The system, Sb 2ox ( x:3, 5 ) - As 20y ( y:3, 5 ) - so 3 - H20 has

been investigated over a wide ranges of sulfuric acid concentration.

The solubility and stability ranges of Sb 2o 3 , Sb 2o 5 , As 2o 3 and

compounds formed in the system have been determined at 25°C.

Furthermore, the behavior of antimony and arsenic in sulfuric acid

solution is discussed.

INTRODUCTION

ln copper smelters in Japan, various complex sulfide concentrates

are treated. An appreciable quantity of arsenic and antimony is

accompanied in the concentrates. Control of both elements is very

important for producing high grade copper metal. Many new processes

97

for their treatment have been developed and installed in some

smelters(1),(2), but there are still many problems to be solved.

Onahama 5melter(3) has been produced pure arsenic trioxide by

vacuum-cooling the filtrate of liquor( diluted sulfuric acid satu­

rated with As 2o3 ) from plant for washing converter gas. It is very

important for production of pure arsenic trioxide to determine the

solubility of arsenic trioxide in concentrated sulfuric acid and to

examine the contamination with antimony.

Recently, arsenic and antimony contents tend to increase in a

conventional electrolyte for the electrorefining of copper. The

elements form often a floating slime which lowers the quality of

electrolytic copper(4).

To clarify the behavior of antimony and arsenic in sulfuric acid

solution for solving such problems in the hydrometallurgical opera-

tions, it is necessary to know the equilibrium for the following

systems.

( 1 ) The system 5b2o 3 - 503 - H20

(2) The system sb2o 5 - 5o3 - H20

(3) The system As 2o 3 - 5o3 - H2o

(4) The system As 2o 5 - 5o3 - H20

(5) The system 8b203 - As 2o 3 - 503 - H2o

(6) The system 5b2o 3 - As 2o 5 - 503 - H2o

(7) The system 5b2o 5 - As 2o 3 - so3 - H20

(8) The system sb2o 5 - As 2o 5 - so3 - H2o

In this paper, the equilibrium for these systems is investigated.

THE EQUILIBRIUM FOR THE SY5TEM Sb(III,V) - As(III,V) - S03 - H20

1. The system Sb20J - S03 - H20

H2o is of great interest in chemical

analytical procedures and in industry of production of various

98

antimony compounds. There is several information in the literature

on the system sb2o 3 - so3 - H2o.

fates are produced by reacting

A variety of antimony(III) sul-

Sb2o 3 and H2so4. The results

reported on the chemical compositinn and solubility of these com­

pounds are inconsistent and contradictory.

The equilibrium for the system sb2o 3 - so3 - H2o was examined by

shaking the mixture of antimony trioxide and sulfuric acid solution

( O - 1820 g/1 H2so4 ) at 25°C for one month. The results from

the chemical analysis of solutions and precipitates are plotted

in Figure 1 together with data by Gospodinov et al. (5) at 100°C.

Various compounds are formed in the system Sb2o 3 - so3 - H2o at

both temperatures.

Figu r e 1(a) shows that the so3 /sb2o 3 molar ratio in the precipi­

tates is either 0.50, 0.66, 1.0, 2.0 or 3 . 0, indicating the

existence of the five compounds. These compounds are represented

without indicating hydration as 2Sb2o 3 -so3 , 3Sb20 3 ·2S03, Sb203 •S03,

Sb2o 3 ·2so3 and Sb2o 3 ·3S03. At 25°C, Sb2o 3 is stable as a solid in

the range of O - 20 g/1 H2so4 , 2Sb2o 3 ·so3 in 30 - 360 g/1 H2so4 ,

3Sb 2o 3 ·2S0 3 in 400- 560 g/l H2 so 4 , Sb 2o 3·so 3 in 590- 880 g/1

H2so4 , Sb20 3 ·2S03 in 950 - 1280 g/1 H2so4 and Sb20 3 ·3S03 in 1370 -

1800 g/1 H2so4. Below 800 g/1 H2so4 , the results agree well with

those obtained at roem temperature by Hintermann et al.(6).

In Figure 1(b), Sb2o 3 -so3 and sb2o 3 ·2S03 have the highest so1u­

bi1ity in 880 g/1 and in 1280 g/1 H2 so 4 at 25°C, respective1y.

Furthermore, the solubility of these compounds wi11 increase with

an increase in temperature.

The data of Figure 1 are a1so shown in Figure 2 as a ternary

diagram of the system sb2o 3 - so3 - H2o at 25°C. The typica1 X-ray

diffraction patterns of their compounds are shown in Figure 3.

99

2. The system 5b2o 5 - 503 - H2o

There is very little data on the system 5b 2o 5 - 50 3 - H2o.

The experiment was carried out by shaking the mixture of antimony

pentaoxide ( amorphous ) and sulfuric acid solution ( O - 1540 g/1

H25o4 ) at 25°C for one month. X-ray diffraction confirmed the

nonexistence of antimony(V) sulfate at 25°C. Figure 4 shows that

5b 2o 5 ( amorphous) is highly soluble at 1100 g/1 H25o 4 at 25°C.

3. The system As 2o 3 - 503 - H2o

The system As 2o 3 - 503 - H2o is of importance in many hydro­

metallurgical processes for separation and recovery of arsenic as

arsenic trioxide from acidic solutions.

The equilibrium for this system was examined by shaking the mix-

ture of arsenic trioxide ( cubic and sulfuric acid solution ( O -

1770 g/1 H25o4 ) at 25°C for two weeks. X-ray diffraction confirmed

the existence of As 2o 3 and As 2o 3-5o 3 as a solid between O to 1550

g/1 H2so4 and above 1340 g/1 H2so4 , respectively. X-ray diffraction

pattern of arsenic(III) sulfate, As 2o 3 -so3 , agreed with that pub­

lished by JCPDS (Card File No.22-072). The concentration of arsenic

(III) in solutions are plotted in Figure 5 together with data by

Inomata et al.(7) and Zieren Company (7). The solubility of As 2o 3

decreases significant1y with an increase in concentration of su1fu-

ric acid in the range of 100 to 1080 g/1 H2so4 ,

s1ight1y in the range of 1080 to 1280 g/1 H2so 4 .

but increases

Above 1340 g/1

H2so4 in which As 2o 3 -so3 is stable,

(III) is very 1ow.

the concentration of arsenic

On the basis of the chemica1 ana1ysis of so1utions and precipi-

tates a ternary diagram of the system As 2o 3 - 503 - H2o at 25°C was

constructed as shown in Figure 6.

4. The system As 2o 5 - so3 - H2o

There is very litt1e data on the systern As 2o 5 - so 3 - H2o.

100

Menzies et al.(8) reported that arsenic pentaoxide is stable in

water as As 2o 5 ·4H2o below 20°C and as 3As2o 5 ·5H2o above 40°C.

Arsenic pentaoxide is highly soluble in water ( dissolved in water

up to 570 g/1 As(V) at 25°C )(9). It can therefore be presumed that

arsenic pentaoxide is highly soluble in sulfuric acid solution.

5. The system Sb2o 3 - As203 - S03 - H20

Very little is known about the system Sb- As- S0 3 - H20•

The equilibrium for the system Sb2o 3 - As 2o 3 - so3 - H2o was

examined by shaking the mixture of antimony trioxide(orthorhombic),

arsenic trioxide(cubic)( with Sb2o 3 /As 2o 3 molar ratio : 0.10/0.10 )

and · sulfuric acid solution ( O - 1690 g/ 1 H2 so 4 ) at 25°C for one

month.

X-ray diffraction confirmed that sb2o 3 or 2Sb2o3 -so3 and As 2o 3

monoclinic ) exist as a solid in the range of O - 450 g/1 H2so4 ,

while antimony(III) sulfates and As 2o3 (cubic) exist in the range

of 500 - 1600 g/1 H2so4 at 25°C.

The results from the ｣ｨ･ｭｩ｣ｾｬ＠ analysis of solutions and precipi-

tates are plotted in Figure 7. The stability range and solubility

of antimony(III) sulfates in sulfuric acid solution are invariable

in the presence of As 2o 3 ( monoclinic or cubic ). The solubility of

As 2o 3 lowers in the range of O - 450 g/ 1 H2 so 4 in which the crystal

form of As 2o 3 is changed from cubic to monoclinic by the presence

of Sb2o 3 or 2Sb2o 3 ·so3• But the solubility of As 2o 3 is invariable

in the range of 500 - 1600 g/1 H2so4 in which As 2o 3 (cubic)is stable

even in the presence of antimony(III) sulfates.

The results described above suggest that in the presence of large

amount of antimony(III) in sulfuric acid solution, arsenic trioxide

will be contaminated with antimony (III) because of the very low

solubility of antimony(III) sulfates.

101

6. The system Sb2o 3 - As 2o 5 - so3 - H20

1) The system sb2o 3 - As 2o 5 - H2o

The equi1ibrium for the system Sb2o 3 - As 2o 5 - H2o was examined

by shaking the mixture of antimony trioxide ( orthorhombic ) and

arsenic acid solution ( with Sb2o 3 /As 2o 5 molar ratio : 0.25/0.10 -

0.10/0.10 ) at 25°C for three months. THe results are plotted in

Figure 8 as a function of pH.

Figure 8(a) shows the existence of antimony(III) arsenate having

Sb2o 3 /As 2o 5 molar ratio of 1.0 in the pH range of 1.6 - 2.3. The

formula of the compound will be represented as SbAs04 without

hydrate by the chemical analysis and by the thermoanalysis shown

in Figure 9. The X-ray diffraction pattern of SbAs04 shown in

Figure 10 is in disagreement with that published by JCPDS ( Card

File No.1-728 ).

The solubility of SbAs04 can be characterized by the reaction

SbAs04 (s) + 2H2o = HSb02 + H3As04

The solubility product for SbAs04 is given by

( 1 )

(2)

By calculating from date of Figure 8(b), the value of Kso is

10-6•67 and the value of the standard free energy for formation of

SbAso4 is - 176.2 kcal/mol.

By using this free energy data, the equilibrium log [As(V)] - pH

diagram was calculated and i1lustrated in Figure 11. An increase in

concentration of total antimony(III) in acidic solution leads to

further stabilization of SbAso4•

2) The system sb2o 3 - As 2o 5 - so3 - H2o

The equilibrium for the system Sb2o 3 - As 2o 5 - so3 - H2o was

examined by shaking the mixture of antimony trioxide(orthorhombic),

arsenic acid solution ( with Sb2o 3 /As 2o 5 molar ratio : 0.10/0.10 )

and sulfuric acid solution ( O - 141 O g/1 H2so 4 ) at 25°C for one

102

month. The results are plotted in Figure 12.

Figure 12(a) shows the existence of three compounds having the

5b2o 31As 2o 5 molar ratio of 1.0, 1.5 or 2.0. From the results of

the chemical analysis, the formula of these compounds will be

represented as 5bAso4 formed in the range of O - 930 gll H25o4 ,

ＳＵ｢ Ｒ ＰｾﾷＲａｳ Ｒ Ｐ Ｕ ﾷＴＵＰ Ｓ＠ in 1020 - 1100 gll H25o4 and 25b2o 3 ·As 2o 5 ·4503

in 1150 - 1370 gll H25o4• X-ray diffraction patterns of these two

antimony(III) arsenate sulfates are shown in Figure 13.

Figure 12(b) shows that the level of antimony(III) in sulfuric

acid solution was reduced by the precipitation of 5bAso4• Further­

more, the solubility behavior of 5bAs04 in sulfuric acid solution

( 200 gll H25o4 ) is studied at 25°C. The results are shown in

Figure 14. X-ray diffraction confirmed that only 5bAs04 is formed

at initial 5b2o 3 I As 2o 5 molar ratio in the mixture below 1.0,

while 25b2o 3 ·503 is formed together with 5bAso4 at initial 5b2o 3 I

As 2o 5 molar ratio above 1.5.

Figure 14(b) shows that antimony(III) concentration equilibrated

with the mixture of 5bAso 4 and 25b 2o 3·5o 3 become equal to the solu­

bility of 25b2o 3 ·5o3• Corresponding to ｴｨｩｾ＠ antimony(III) concent­

ration, arsenic(V) concentration trends toward a minimum value

which is controlled by the solubility product of 5bAs04•

Therefore, 5bAs04 will be one of. the constitutive compounds in

the floating slime formed during the electrorefining of copper.

7. The systems 5b2o 5 - As 2o 3 - 503 - H2o and

5b2o 5 - As 2o 5 - 503 - H20

The experiments were carried out by varying the 5b2o 51As2o 3 or

As 2o 5 molar ratio in the mixture of 5b2o 5 ·2H20 and arsenious or

arsenic acid solution and sulfuric acid solution ( 200 gll H25o4

at 25°C. The results proved the nonexistence of compounds of 5b2o 5

with As 2o 3 or As 2o 5 in sulfuric acid solution.

103

CONCLUSION

In arder to clarify the behavior of antimony and arsenie in

sulfurie aeid solution, the system sb2ox( x:3,5 )- As 2oy( y:3,5 )-

so3 - H2o át 25°C was investigated by mixing method. Six antimony

one arsenie sulfate in

the system As 2o 3 - so3 - H2o and one antimony arsenate and two

antimony arsenate sulfates in the system sb2o 3 - As 2o 5 - S03 - H20

were identified. The solubility and stability ranges of those

eornpounds, Sb2o 3 , Sb2o 5 and As 2o 3 were determined.

In production of arsenie trioxide from sulfurie aeid solution

eontaining a large amount of antirnony(III) by erystallization, the

produeed arsenie trioxide will be eontarninated with antimony(III)

beeause of very low solubility of antirnony(III) sulfates formed.

Only antimony(III) arsenates are formed as antirnony arsenie

eornpound in sulfurie aeid solution. Therefore, SbAs04 whieh is

stable below 900 g/1 H2so4 , is one of the eonstitutive eompounds

in the floating slirne during the eleetrorefining of eopper. To

further know distinetly the meehanism of formation of the floating

slirne, more detailed studies will also be neeessary in the presence

of bisrnuth and copper at higher temperature.

REFERENCES

(1) Mohri, E. : J. Min. Met. Inst. Japan, 94 451-456 (1978). (2) Yashuda, M. : J. Min. Met. Inst. Japan, W 555-560 (1984). (3) Kono, H., Sugawara, Y. and Hashimoto, M. : Paper presented at

112 th AIME Annual Meeting, Atlanta USA, Mareh 1983. (4) Lindsfrom, N.F.R. : Urlited States Patent, 3,753,877 (1973). (5) Gospodinov, G. and Ojkova, T. : z. anorg. allg. Chem., 472

233-240 (1981 ). (6) Hinterrnann, Jf.E. and Venuto, C.J.: J. Eleetroehern. Soe., 115

10-12 (1968). A -

(7) Menzies, A.W.C. and Potter, P.D. : J. Am. Chern. Soe., 34 1452 ( 1912). -

(8) Broul, M. et al. : Physieal Seiences Data 6, Solubility in Inorganie Two-Component Systems, Elsevier Seientific Publish­irig Company (1981).

(9) Inornata, I. et al. : J. Sulphurie Aeid Soe., 9 127-133, 169-175 (1956). -

10.4

! 4

i .!

I

10 ｲＭｾｾＮＮＮＮＮＮＮＬＮ｟ＬＮＮＮＮＬＮＮＮＮＬＮＮＮＬＮＮＮＬＮＮＮＮＮＮＮＭＬＭＬＮＮＭＭＬＭｾＬ｟ＬＮＮＮＮＬ＠

- ,,.. •• wort, n•c Ｌ ｬｾﾷ ｜＠ ft

s . i = 4

•••• lospodt- t i e1, IOO'C I Ｇｩｾ＠ Ｎｾ＠I -.,_. ｾＧ＠ '

,.-4 ' '\ I "

I

l

.............. I , ...

Ｐｾｾ Ｇ Ｇ Ｇ ＮＧＧＧ＠ ,,,,,,! o 600 1000 1500

H1SO, I t/1 l

Fig. 1 (a) The so3/sb2o3 molar ratio in precipitates

(b) The antimony(III) concentration in solution after equilibrating various mixtures of antimony trioxide and

sulfuric acid solution at 25 and 100°C,

lltO 11 21 11 41 IG 10 1t 10 U wttl

so,

Fig. 2 The system sb2o3 - so3 - H2o at 25°C.

lOS

(E) "'f»·t!l>(>,•"'f' •• Ulo (A)"'f'>(00'-1<) .... • .....

" .... .. .... .. ..... • ,5uc 5u• t.IG • ·- .. ·- " .....

' 1 ... .. J J.L. I

1- • l I III l.d l ｾ＠... .. .. ... - ..

H2so4 20 g11 H2so4 956 g/1

-•• III, .. Ulo •• "'· '·"' • (l) """'' ""

.... .. (f)"'f'>' ..., .... 1 • ._ • ..... • .... >o ... " .....

" ..... " .... .. ..... • ... 11 ..... .. ....

" .... .. ... M ..... ... Ｕ＼ｾｾｾｍ＠ ..... • 1 •• ..

:.- 1- • ..... .. I .III .. I.U '

.... • 1 .... • l .m

" ... ..

I ｾ＠1 ... • .....

" 1.21& • I i ol I ... .. .. .

H2so4 38 g/1 H2so4 1279 911

•• "'• •i UI, •• 111,

. (<) ｾＧＢＢＧ Ｇ ＮＮＮＬ＠10.101 1 <•> '"t'>'"">·'ll 10. ... • '·"' lt ....

' ..... .. ...... .... .... .. .. .. " J.:IQ • t.m . ..... '

J,2ST • 1.t01 "' ..... " J:.Jtt •

ｾｵ｣＠ 1-·· .. ;til .... • 2. 1 .. • 1 •• • ..... • ...... • 1- 1 ..... "

:t.m • 1 ..... 1 .... .. 1 ...

"

III J • I 1 .... • 1 ... .

J I ., I ·.1.11

• ... .. . .. .. H2so4 l97g/1 H2so4 1463 911

.. •l lllo (M)"'f'>•""J(II •• III, fi· III,

(D) '"f'>' ... ..... .. '·"· " ... 12 ... .. 4-Ul • ... • .... .. . .... I. ... ..

" ..... .. . .... .. .. ... • ..... " . ... • . .... •

s-- ..... .. ｾ｜ｕ＠ ·- .. ... .. .... • .. ... • t.l ..

" .... • ... • . .... •

lal I ｾｩ＠ utd ... .. .. .. .. . .. .. H2so4 797 911 H2so4 1714 g/1

Fig. 3 X-ray d,iffraction patterns of compounds in the systern

Sb203 -so3 - H20.

106

ｳｲｯｾＭｲｾｾｾｾＭｲｾｾｾｾｾｾ＠

4

ｾＳ＠::::::. ... ｾ＠ 2

500 1000 1500 H2so. <em

Fig. 4 The solubility of Sb2o5 (amorphous) in sulfuric aci d solution at 25°C.

ＱＵｾｾｾｾＭＭＭＭＭＭｾｾｾｾＭＭｾ＠

-o- pruentwork.25t.2wuh

• ._. Zitttl Co.. 25t

·-<>· 1•••11 .. 111, 40t. 2HtL

·•· • • 2ot • •

i .. c

5

01. ;: Ｚ ｾＬｴｲｾｾｪ＠o 500 1000 1500

HtSO, I g/ 1 I

Fig. 5 The arsenic1III) concentration in solution after

equilibrating various mixtures of arsenic trioxide and sulfuric acid solution at 25°C.

107

l._ft.,Uft. • • . , ___ I I

I..O.·Ift. · •-..-1 ••'- ' IA.O.· liO.

I e ＭＭＭＭｾｾＲＭＮｯＮ ﾷ ＠

12 1\ . \ :? 10

\ \ ｜ Ｍ｣ｾ＠\

\ \

,, .,,,.. .... ,,'

Ｇ ＢＢＢＧ ﾷ Ｍ ﾷ ｾ＠Ｐ ｯ ＭＭｾｾｾ Ｕｾｯｯｾｾｾ ｾ ＬｯｾｯｯｾｾｾｾＬｾＵｾｾｾ＠

H,so, <1/ll

Fig. 7 (a) The Sb2o3/As2o3 molar ratio in the precipitates

(b) The antimony(III) and arsenic (III) concentrations in solution after equilibrating mixture 'of antimony trioxide and

arsenic trioxide at various sulfuric acid concentrations at 25°C.

ｾ＠ 1.5 ｲＭＮＮＮＮＬＮＮＮＭＭＭＮＮＮＭＭＭＭＭＮＭｾＭ

.5 I ｾ＠ 1.0 ' SbAsO, I

1 I ＰｾＵ＠.___.......__.___,_----l..___j

.. ,.......---...----.-......----1

s o .! -2

> i -3

5-4 ｾ＠ ... ｾ＠ -5

\ At(VI

&o-o- SbUIIl

-· ｾｾＭＭｾＭＭｾｾｾｾ＠D

pH

108

ｲＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭｾ＠;Ã til. ;Á 1/1.

uoe 11 2 •• • .... 100 '·"' • •••• ti 1·111 • Ult 11 .l.tll • 2.121 11 1.13f . 12 un 2S 1.TM 1 , .... 1 1.111 • Sa• 2.102 12 1.111 I

40 2t··

.. . ..

Fig. 9 X-ray diffraction pattern

of SbAs04•

Fig. 8 Relationship between pH and (a) . the Sb2o 3/As 2o 5 molar ratio in the precipitates and (b) the antimony(III) and

arsenic(V) concentrations in solution after equilibrating

various mixtures of antimony trioxide and arsenic acid solution at 25°C.

ｗｯｾｨｴ＠

SbAo01 1lo ｾ＠ T 6 925

Ｒｓ｢｡ＰｩｾＮＭＭＮＹＭ

ｳｾＮＭＭＭｾｌ＠

40

200 coo soo soo 1000 ·c

Fig. 10 Thermoanalytical curves of SbAso4

•

109

ｾ＠ -1 e

g -2

Fig. 11 Equilibrium log [As(V)] - pH diagram for the system

Sb(III) - As(V)- H20 at 25°C.

i .!1

• ii i ｾｾ＠ ｬＭＭＭＭＭＢＺＮＺＺＺＦＺＱＡＡＺｾ］ＧＭＭＭＮｯｬＭＭｾ＠

j : L........-..1... ｾ｟Ｎ｟｟Ｎ｟Ｎ｟｟Ｌ＠ｯｾｾｾＭｔｾ ｾｾｾ Ｍｲｾｾ＠

--- 111(111) h Sb20,. so,. y ＱＱＱｾ＠

Ｍ ﾷｾｾｾｾｾｾｾｾｾｾ｟Ｎ｟＠

o 600 1000 1500 H,so, lo/ll

Fig. 12 (a) The Sb2o3/As2o5 molar ratio in precipitates

(b) The antimony(III) and arsenic(V) concentrations in

solution after equilibrating mixture of antimony trioxide and arse­

nic acid solution at various sulfuric acid concentrations at 25°C.

u

Su}

110

.. •• lllt •• ,,,,

tllozO,· Aoz01· 4S0, •1 III, 11

lll>:o3 ·ru,o1·&so3 ..... •• l.111 14 .,. .. . . ... e.m • l.l41 • • ••• ' J,41f ..... .. J •• ' '··· .. .... ... ' ... • •••• • 3 .... ... • J ... • Ult 13 ｾＮ＠ ..

I ••• 11 , ... 14 s:u .... ' . .. UM • J ... 14 ..... 11 ..,. .... 11 J ••• • J.m • ··= U&& a ••• ' •••• • . .. ... IOJ .. ,. ' •••• •

.. .. . .. H2so4 1095 g/1 tt2so4 t254 g/1

Fig. 13 X-ray diffraction patterns of antimony arsenate

sulfates.

i .. •i

I

l -1 ｾ＠ Ao!VI

s ; : -2 ｾ＠c

& -3 4 ;

-4 ｾ＠ ＤｾＨＱＱ＠

--- SoMIItllof nbz0l·S03

-5 o 0.5 I. O 1.5 2.0 l5

lnitiat ｾＰＮ＠ lfttlar rttit in fllxt•re

The Sb2o3 /As 2o5 molar ratio in precipitates

lllt • • • • ' • • • 4

..

Fig. 14 (a)

(b) The antimony(III) and arsenic(V) concentrations in solution after equil i brating va.rious mixtures of antimony

trioxide. and arsenic acid solution in sulfuric acid solution,

200 g/ 1 'H2 so4 , at ＲＵｾｃ Ｎ＠