studies on the extraction and separation of antimony with methyl iso-butyl ketone

Journal of Radioanalytical Chemistry, VoL 45 (19 78} 317-324

STUDIES ON THE EXTRACTION AND SEPARATION OF ANTIMONY WITH METHYL ISO-BUTYL KETONE

R. SHABANA,* H. RUF

Institute oJ'Radiochemistry, Nuclear Research Center Karlsruhe (FRG)

(Received January 23, 1978)

Systematic studies are carried out on the extraction of tri-and pentavalent antimony with MIBK from pure acid halide solutions as well as from binary mixtures of each with sulphuric acid. The influence of KI on the extraction of antimony from sulphuric acid is also investigated. It is found that the extraction of antimony halides is highly affected by addition of sulphuric acid to the aqueous phase. The extractability of some other elements at the optimum conditions for antimony extraction is also studied in order to establish separation procedures. In the light of the obtained results, analytical advantages are mentioned and separation procedures are recommended. The extraction mechanism is also discussed in order to explain the role of sulphuric acid in the extraction equilibria.

Introduction

The extraction of ant imony with organic solvents from iodide and bromide sys-

tems has been investigated by several authors. 1-4 It has been found that many ele-

ments follow ant imony in the organic phase. GRIMANIS 5 has found that the

highest distr ibution coefficient for the extract ion o f ant imony into benzene is

achieved at working solutions of 10M in H2SOa and 0.03M in KBr. I t has been

also reported s-s that the extract ion o f certain metal halides is highly influenced

by addit ion of sulphuric acid to the aqueous phase.

In the present work systematic studies are carried out on the extract ion behavi-

our of tri- and pentavalent ant imony from pure acid halide or sulphuric acid solu-

tions by methyl isobutyl ketone (MIBK). The extract ion o f ant imony is also stud-

ied from halide solutions containing sulphuric acid. The extractabi l i ty of some

other elements is also studied at the opt imum conditions for Sb extract ion in

order to find selective separation procedures.

*Permanent address: Nuclear Chemistry Dept. Atomic Energy Establishment, Cairo, Egypt.

J. Radioanal. Chem. 45 (1978) 317

R. SHABANA, H. RUF: STUDIES ON THE EXTRACTION AND SEPARATION

Experimental

Chemicals and radioactive tracers: Methyl isobutyl ketone (MIBK) (a product of Merck) is used as the solvent for the extraction of the investigated elements. Acids and all other chemicals used are of analytical grade quality.

The isotopes 22Na, 13aCs, 9~ 133Ba, 76As, 124Sb, 75Se, 6~ 95Zr, 144Ce, 152Eu, 239Np, 238pu and 241Am are used for tracing the corresponding

elements.

Procedure: Batch extraction experiments are carried out in stoppered glass tubes by shaking equal volumes (5 ml) of both aqueous and organic phases. The tubes are mechanically shaken for 20 minutes at room temperature (20-+ 3 ~ After disengagement, aliquots are withdrawn for measurements. The distribution ratio D is determined radiometrically from the radioactivities of the corresponding isotope

it. both phases. Each D value represents in most cases the average of three measurements.

Plutonium and americium are detected by measuring their a-activities while Sr/Y pair is detected by the ~3-activity. The other isotopes are detected by measuring their y-activities in solution by a NaI(T1) crystal connected to a counting assembly. A methane flow counter is used for a- and fl-measurements after the preparation of dry samples on quartz or teflon plates.

Results and discussion

It is interesting to note that the distribution ratios for the extraction of certain metal halides which are poorly extractable, are highly increased by the addition of sulphuric acid to the aqueous phase. 5-8 Hence, the extraction of antimony from individual solutions of HC1, HBr or H2 SO, as well as from binary mixtures of halo- acid and sulphuric acid solutions is investigated in order to verify this influence in the present extraction system.

(1) Extraction of antimony from single acid solutions: The extraction of tri- and pentavalent antimony with MIBK is studied as a function of HC1, HBr or H2SO4 concentrations and the obtained data are represented in Fig. 1. As can be seen, antimony is poorly extractable from sulphuric acid solutions in the whole range of acidity studied which agrees with that previously reviewed. 9 The distribution ratio is increased with increasing halo-acid concentration. It can be observed that the extraction behaviour of Sb(III) and Sb(V) is more or tess the same. This implies that the separation of the two oxidation states is rather difficult to be achieved in the regarded systems.

318 J. Radioanal. Chem. 45 (1978)


10-1

'S Z ! t

I t 5

d , I

O~ x

10-~

10 3 i 1 1 i _ _ I ~ _ _ L ~ , . 0 1 2 3 /. 5 6 7

A c i d , M

Fig. 1. Effect of HCI, HBr and H=SO, concentrat ions on the extract ion o f Sb with MIBK.

[Dotted lines represent Sb(III) and solid lines represent Sb(V)] o - HCI, L - HBr and

X - H~SO4

(2) Extraction of antimony from mixed media: The extraction of Sb(IIl) and

Sb(V) with MIBK from 4.5M H2SO4 solution is studied as a function of HC1 or HBr concentration in the aqueous phase, and the data are given in Fig. 2. This fig-

ure shows that the extraction [which is negligible (D < 0.05) in absence of acid

halide] is increased sharply with increasing the halogen ion concentration up to

~0.3M. At higher concentrations of HC1 or HBr concentration, steady values for the distribution ratio are attained.

Similar studies are carried out on the extraction of Sb(III) from 4.5M H2SO4 solution as a function of KI concentration and the data are cited in Table 1. These

data show also that the distribution ratio is sharply increased with increasing KI

concentration. It is observed from Fig. 2 and Table 1 that the distribution ratio for antimony extraction increases in the order: chloride < bromide < iodide. It is to be mentioned that mutual separation of Sb(III) and Sb(V) can be performed

�9 ;7, Radioanal . Chem. 45 [1978) 3 1 9


DA 10 3 - -

lO 2

10

1

10 [ ~ L ~ ~ 1 J J ~ , I D . -

0 . 5 1.0 1 5 Halo-acid, b4

Fig. 2. Effect of HC1 and HBr concentrations on the extraction of Sb from 4.5M H 2804 with MIBK. [Dotted lines represent Sb(III) and solid lines represent Sb(V)] o - HC1 and

- HBr

Table 1 Effect of KI concentration on the extraction of Sb(III) from 4.5M H 2 SO4 solution

KI, M Distribution ratio, D

0.035

0.070

0.10

0.15

0.20

0.25

0.30

0.35

0.10

0.24

2.00

1 1 . 0 0

40.80

106

240

450

f r o m so lu t ion o f 4 .5M in H2SO4 and 1M in HC1 b y successive e x t r a c t i o n s w i t h a

reasonable sepa ra t ion fac to r as obse rved f r o m Fig. 2.

On the o t h e r h a n d , the ex t r ac t ab i l i t y o f pen t ava l en t a n t i m o n y w i t h MIBK f rom

1.4M HC1 or HBr so lu t ions is s tud ied as a f u n c t i o n o f H2 SO4 c o n c e n t r a t i o n . The


R. SHABANA, H. RUF: STUDIES ON THE EXTRACI'ION AND SEPARATION

Table 2 Extractability of antimony(V) as a function of its concentration

in MIBK from 4.5M H2SO4-1.4M HCI or HBr

Concentration of Sb, mg/ml

3.56 7.12 9.13

18.26 27.39 36.52 45.65 54.78 73.04

100.43

Corresponding molarity of Sb

0.029 0.058 0.075 0.150 0.225 0.300 0.375 0.450 0.600 0.825

Distribution ratio

4.5M H2SO4-1.4M HCI

60 64 66 73 87 82 63 23 21

7

4.5M H2SO 4 -1.4M HBr

72 94

110 173 176 146 135 133 76 28

obtained results are represented in Fig. 3. This figure shows that the distribution

ratio is sharply increased with increasing H2SO4 concentration and then reached

steady values at concentrations higher than ~3.5 and 4.5M H2SO4 in case of HBr

and HC1 systems, respectively. Therefore, it is preferable to work at low halide

and sulphuric acid concentrations.

From the above mentioned results, solutions of about 4.5M in H2 SO4 and 1.4M

in acid halide as well as 4.5M H2SO4-0.3M KI may be recommended for the extraction of antimony.

Attention has also been given to the influence of the antimony concentration, in the aqueous phase, on its extraction from chloride and bromide media in presence of sulphuric acid. The data given in Table 2 show the extractability of Sb(V)

with MIBK, from solutions of 4.5M in H2SO4 and 1.4M in HC1 or HBr, as a function of its concentration. As can be seen, the distribution ratio increases with in-

creasing antimony concentration up to concentrations which correspond to the

stoichiometric proportion of antimony and chloride or bromide ions present in the aqueous phase.

Extraction mechanism: In extraction system involving oxygen-containing solvents, the main characteristics of extraction from aqueous halide solutions is the extrac-

tion of protonated metal complex anions, preferentially single-charged. Therefore,

the extraction mechanism suggested for the studied systems is regarded as:

Sb n§ + nX- ~ SbXn (1)

f. Radioanal. Chem. 45 (1978) 32I

Di

10 z

10

1

10-1

10 0

I ] I I I ] 1 2 3 4 5 6

H2S04, M


Fig. 3. Effect of H2 SO4 concentration on the extraction of Sb(V) from 1.4M HCI or HBr with MIBK. o - HCI and ~ - HBr

SbXn + HX + H20 g (SbXn+l)- + H 3 0 + -H 20

, Ia(SbX.§ (2) (H~SO4)

H(SbXn§ + mS ~ H(SbXn+I)" m S , (3)

where X- is the halide anion, H(SbXn.I) is the extractable profonated anion com-

plex of ant imony, and S is the solvent molecule. Indeed this is in agreement with

the data given in Table 2 where maximum extractabili t ies are observed at stoichlo-

metric ratios of Sb and halide ions.

Extraction of other elements: The extractabi l i ty of some other elements is in-

vestigated at the op t imum conditions for ant imony extract ion in order to find new

interseparation possibilities. The distribution ratio values for the studied elements

are given in Table 3. As can be seen from this table, As and Ba follow Sb in the

chloride and bromide systems as well as Se follows Sb in the bromide system only.

Np and Ce are slightly extracted from the chloride and bromide systems. The ex-



Table 3 Extractability of some metal halides with MIBK in presence of 4.5M H2SO 4

Distribution ratio

Element 4.5M H~SO 4 - 4.5M H~ SO 4 -- 4.5M H a SO 4- 1.4M HCI--MIBK 1.4M HBr-MIBK 0.33M KI--MIBK

Na

Cs Sr/Y Co(II) Eu(III) Pu(IV) Am(Ill) Zr(IV) Np(IV) Ce(III) Ba(II)

Se(IV) As(III) ,Sb(III) As(V) Sb(V)

0.015 0.014

<0.001 0.020 0.006 0.005 0.008 0.050 0.170 0.200 2.080 0.210 2.020 9.900 0.082

246.000

0.012 0.004 0.030 0.010 0.006

<0.001 <0.001

0.050 0.190 0.160 1.780 4.321

116.300 39.900

158 120

0.022 0.010

<0.001 0.035 0.019

<0.001 0.117 0.100 0.178 0.069 0.081

185.600 380.000

tractability o f the other investigated elements (Na, Cs, Sr, Co, Zr, Eu, Pu and Am) is very low or negligible.

From the forementioned data, it can be concluded that the given extraction sys-

tems (H2SO4 - acid halide - MIBK and H2 SO4 - K I - MIBK) are convenient for quantitative extraction o f antimony as well as for its separation from the foremen-

tioned poorly extractable elements. The back-extraction of antimony can be ac-

complished by washing the organic phase with pure sulphuric acid solution. Separa-

tions within the group of well extracted elements may be also performed by suc-

cessive extractions. Furthermore, the given procedures are applicable for the deter-

mination :of antimony in biological samples which are usually digested and dissolved

in concentrated sulphuric acid by making these solutions 4.5M in H2SO4 and 1.4M

halo-acid or 0.33M KI. It is to be mentioned that the chloride system is recom-

mended for the separation of Sb(V) from Sb(III) as well as for the separation o f

Sb(V) from As(V) as can be observed from Table 3.

J. Radioanal. Chem. 45 (1978) 323

R. SHABANA, tt. RUF: STUDIES ON THE EXTRACTION AND SEPARATION

The first author (R. SHABANA) wishes to express his appreciation to the Nuclear Research Center in Karlsruhe which gave him the opportunity to carry out this work in the Federal Republic of Germany. He would also like to express his thanks to Prof. Dr. SEELMANN- EGGEBERT, the director of the Institute of Radiochemistry for his kind encouragement and interest. Thanks also due to all the collegues in the Analytical Chemistry Division for their help during this work.

References

1. H. M. IRVING, F. J. C. ROSSOTTI, Analyst, 77 (1952) 801. 2. H. GOTO, Y. KOKITA, J. Chem. Soc. Japan, 82 (1961) 1212. 3. A. P. GRIMANIS, G. W. LEDDICOTTE, U. S. At. Energy Comm. Rept. ORNL-3397, 1962,

p. 74. 4. A. B. SOKOLOV, L. I. MOSEEV, A. G. KARABASH, Zh. Neorg. Khim., 16 (1961) 994. 5. A. P. GRIMANIS, I. HADZISTELIOS, Anal. Chim. Acta, 41 (1968) 15. 6. R. SHABANA, F. HAFEZ, J. Radioanal. Chem., 29 (1976) 99. 7. R. SHABANA, H. RUF, J. Radioanal. Chem., 36 (1977) 389. 8. R. SHABANA, Radiochem. Radioanal. Letters, 32 (1.978) 53. 9. T. L. MOORE, R. J. LARAN, P. C. YATES, J. Phys. Chem., 59 (1955) 90.

324 .I. Radioanal. Chem. 45 (1978)

studies on the extraction and separation of antimony with methyl iso-butyl ketone

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