Separation of gallium, indium and thallium by extraction with n-octylaniline in chloroform

0039-9140/88 $3.00 + 0.00 Copyright @ 1988 Pergamon Press c

Tolonta,Vol. 35, No. 5, pp. 351-360, 1988 Printed in Great Britain. All rights reserved

SEPARATION OF GALLIUM, INDIUM AND THALLIUM BY EXTRACTION WITH n-OCTYLANILINE IN CHLOROFORM SHASHIICANTR. KUCHEKAR

and

MANOHAR B. CH.AVAN*

Analytical Chemistry Laboratory, Department of Chemistry, Marathwada University, Aurangabad 431004, India (Received 18 March 1986. Received 25 November 1987. Accepted 10 December 1987) Smmmuy-Extraction of gallium(III), indium(II1) and ~allium(II1) with n-octylaniline in chloroform at various concentrations of hydrogen halide acids (HCl, HBr, HI) has been studied and a scheme for their separation proposed. The procedure can be successfully apphed to the separation and dete~ination of gallium in presence of mercury, bismuth, manganese, zinc and lead; indium in presence of bismuth, antimony, lead, mercury, cadmium and zinc; and thallium in presence of mercury, cadmium, manganese, aluminium, tin and antimony. The advantage of the method is that the reagent can be recovered for reuse. The method is simple, rapid, and effects clear-cut separation.

Liquid ion-exchanges have been used for the solvent extraction of many metals.‘*2 Liquid anionexchangers are based on primary, secondary and tertiary aliphatic amines. Owing to their generally greater solubility, primary amines are used less frequently than secondary amines. The presence of an octyl group in the pura position in aniline renders this amine more basic and less soluble in water, and p-n-octylaniline has been used as a group extractant for the noble metals.3*4However, this application had limitations, such as the difficulty caused by the tendency of the reagent, which was synthesized from octylbenzene, to form emulsions. Later5 it was reported that the formation of emulsions is minima1 if the reagent is synthesized from n-octanol and aniline. Here, the use of p-n-octylaniline as an extractant for gallium, indium and thallium(II1) from hydrogen halide acids is reported. The advantage of the method is that the reagent can be recovered for reuse without loss of extraction efficiency. Other extractants useful for gallium, indium and thallium(II1) include TBP? ~-~n~laniline,’ mesityl oxide,’ 4-methylpentan-2-ol,9 trioctylamine’O and Aliquat 336,‘O but all are subject to limitations.‘o The method described here offers a rapid and clear-cut separation of gallium, India and thallium(II1) from each other.

B&k sohrtio~~Prepared by dissolving 27.2 g of sodium acetate tetrahydrate in 400 ml of water, adding 17 ml of glacial acetic acid and diluting to one litre. Reagent solution. p-n-Gctylaniline was prepared according to the method given by Pohlandt,s and used as a 10% v/v solution in chloroform, and diluted further as required. The chloroform and all other materials used were of guaranteed grade. Doubly distilled water was used throughout. Extraction of the individual elements (in the absence of the others) Adjust the hydrochloric acid concentration to 8.OM for gallium (W360 pg/ml), 2.OM for indium (40-320 pg/ml; 8.OM lithium chloride medium), and O.lM for thallium (20-80 p&lml). Shake 25 ml of test solution for 1 min with 10 ml of 3, 8 and 1.5% reagent solution in chloroform for Ga, In and Tl respectively. Allow the phases to separate. Strip gallium and indium from the organic phase by shaking it for I min with two 25ml nortions of distilled water. For Tl(II1) use two 35ml portions of acetate buffer for stripping. Determine the metal ion in the aqueous phase complexometrically. Recovery of reagent Shake the residual organic phase two or three times with IO-ml portions of ~monia solution (s.g. 0.88 solution diluted 1:1 with water), and then with distilled water. Distil off the chloroform, and treat the p-n-octylaniline with sodium hydroxide pellets to remove the last traces of water. After decantation, distil the reagent under reduced pressure before use. Rl?SULTS AND DISCUSSION

EXPERIMENTAL

Reagents Standard solution of gallium(III) and indium(IIi). Prepared as described earlier.“J2 Standard solution of tha~l~um(rrI). Prepared by dissolution of the hydroxide in concentrated hydrochloric acid, and dilution. Standardixed complexomet~~lly after addition of bromine water to ensure all the thallium was in the tervalent state.” *Author to whom correspondence

should be addressed.

Gallium, indium and thaflium were extracted from their solutions in hydrochloric, hydrobromic or hydriodic acid, with different concentrations of p-noctylaniline solution in chloroform. Figure 1 shows the results. The effect of lithium chloride as saltingout agent on extraction of gallium and indium from hydrochloric acid is shown in Fig. 2. The results given in Fig. 1 and Table 1 show that it is possible to separate the three elements by appropriate choice of 357

SHASHIKANTR.

358

kl

KUCHEKAR and

MANOHAR B. CHAVAN

60

0

1

3

2

Fig. 1. Extraction of Ga (1.4 mg), In (2.6 mg), Tl (2.0 mg) with n-octylaniline (R) as a function of HCl, HBr or HI concentration. 1, Ga, HCl 3% R; 2, Ga, HBr, 3% R; 3, In, HI, 1.5% R; 4, In, HCl, 7% R; 5, Tl, HCI, 1.5% R; 6, Tl, HBr, 1.5% R.

conditions. Because thallium(II1) is reduced to thallium(1) by iodide, it is essential to remove thallium before hydriodic acid is used in the separation scheme. Fortunately gallium and indium are not extracted at all at low enough hydrochloric acid concentration, whereas thallium can be completely extracted if the concentration of the organic base is high enough. Gallium is not extracted at all from hydriodic acid solution, whereas indium is completely extractable from a 1SM solution of potassium iodide in 2.5M sulphuric acid. Finally, gallium can be extracted from 8M hydrochloric acid. The method is shown as a flow-chart in Fig. 3.

0.5 1.0

Gallium is extracted quantitatively when the total chloride concentration is about 8M. For quantitative extraction of indium(II1) from 2M hydrochloric acid in a single step it is necessary to use 8M lithium chloride as the salting-out agent. Other salting-out agents such as ammonium chloride and magnesium chloride have no significant effect on the extraction of gallium and indium. However, aluminium chloride cannot be used, as it interferes in the final determination. Log-log plots of distribution coefficients vs. amine concentration at fixed acidity for gallium, indium and thallium indicate a 1:l limiting mole ratio of amine to metal, which suggests that the species extracted is

Ga(III)*

In(III)t

In(III)$

Tl(III)*

53.0 (2.8) 69.2 (5.7)

camp. ext. camp. ext.

92.7 (31.8) camp. ext.

camp. ext.

camp. ext.

-

camp. ext.

-

camp. ext.

-

-

(;;:;)

25.0 (0.8) 37.0 (1.5) 48.0 (2.3) 60.0 (3.8) 71.0 (6.1) 80.3 (;;.;)

-

-

(125:O) camp. ext. comn. ext.

(66:7) camp. ext. camp. ext.

-

-

1.5 2.0 2.5

(Y3::) 91.0 (25.3) 93.0 (;;.o’)

3.0 5.0 7.0 10.0

5

Fig. 2. Extraction of Ga (1.4 mg) and In (2.6 mg) as a function of salting-out agent (LiCl) concentration: @-Ga; O-In.

Table 1. Percentage extraction and distribution coefficient (in brackets) as the function of n-octylaniline concentration in chloroform (R) R, %

4

HCl (MI

Acid molarity

Ga, In, Tl taken, 1.4, 2.6 and 2.0 mg, respectively. *Ga(III), 6M HCl; Tl(II1) 0.N HCI. tIn(III), 2M HCl + 8M LiCl. §In(III), 1.5M KI + 2.5M H,SO,.

Ga(III) l-9 mg, In(II1) l-8 mg, Tl(II1) 0.5-2.0 mg

I I I 1 0

O.lM HCl or pH = 1.0 in a total volume of 25 ml (Extract for 1 min with 10 ml of 1.5% n-octylaniline in chloroform)

I I I

I I

Aqueous phase (Ga, In) Evaporate aqueous phase to reduce the volume and add sufficient KI and H,SO, to make their concentrations 1.5M and 2.5M in volume of 25 ml, respectively. Then extract for 1 min with 10 ml of 1.5% n-octylaniline in chloroform

Organi: phase Cn) Strip with two 35ml portions of acetate buffer solution and estimate complexometrically in the aqueous phase

I

I

I

Grganic phase (In)

Aqueous phase (Ga)

I I

I I I

Strip with two 2Lml portions of distilled water and estimate complexometrically

Evaporate the aqueous phase almost to dryness to remove HI, dissolve the residue in water, add sutlicient HCl to make its concentration 8.OM in a volume of 25 ml. Then extract for 1 min with 10 ml of 3% n-octylaniline in chloroform

I

I

Organic’ phase (Ga) Strip with two 25-ml portions of distilled water and estimate complexometrically

Aqueoui phase rejected

Fig. 3. Flow-chart for separation,

Table 2. Effect of diverse ions Diverse inn .___ added

MnWI H.&II)

V(v)

w-v

n(w)

Diverse

Amount tolerated, mg Ga(II1)

In(II1)

Tl(II1)

:

15

20 20 co-ext. co-ext. 20

2: 5 co-ext. co-ext. 5

20 20 10 20

Amount tolerated, mg

inn

added --Au(II1) Ag(I) Pt(IV) Pd(I1) Ru(II1) Rh(II1) Te(IV) Fe(II) Fe(II1) Fluoride Citrate Ascorbate Acetate Phosphate Thiourea Thiocyanate Tartrate H,02 30% (100 vol.) Thiosulphate. Gxalate EDTA Malonate Salicylate

Ga(II1)

In(II1)

10 5 2 5 2 5 2 co-ext. co-ext. 200 200 200 100 100 100 100 100 lml

2 5 5 5 2 5 5 co-ext. co-ext. 100 200 100 200 200 50 50 200 lml

20 In(II1) 20 Ga(II1) 20 WW 10 Cr(vI) : 15 5 5 Mo(VI) 5 20 5 Zn(I1) Sn(I1) co-ext. 5 5 5 WII) Bi(II1) 20 15 1: co-ext. 20 Sb(II1) 10 t: co-ext. pb(II) 5 5 10 Ti(IV) 5 5 10 Co(I1) 10 Cu(II) 80 200 10 5 2: Ni(I1) 100 50 5 Al(II1) 5 20t 25 5 5 10 As(III) 80 1; 20 5 5 Mg0I) 100 200 10 15 15 ReWI) Ga, In, Tl taken, 1.4, 2.6 and 2.Omg, respectively. *Masked with ascorbate. tbfasked with thiosulphate. $Masked with fluoride. 359

Tl(II1) 5 5 5 2 5 5 5 & 100 100 Int. 200 200 Int. Int. 200 1.5 ml Int. 200 100 80 200

360

SHAWIKANT

Table 3. Separation and determination and thallium Elements taken, mg

R. KUCHEKARand MANOHARB.

of gallium, indium

Elements found, mg

Ga

In

n

Ga

In

Tl

1.40 2.80 7.11 5.67 9.95 2.81

2.57 2.57 7.71 5.14 5.14 7.71

2.31 2.31 1.15 2.31 1.15 2.31

1.39 2.78 7.07 5.61 9.88 2.80

2.57 2.57 7.67 5.09 5.14 7.70

2.31 2.31 1.15 2.31 1.15 2.31

probably RNH: . MCI; where R is C8H&H,, and M is Ga, In or Tl. Extraction was found to be more than 99.9% complete in 30 set, so a I-min shaking period is recommended for all three extractions. Eflect

of diverse

ions

Several ions were examined for interference (Table 2) in the proposed method. An error of f 1.5% in analyte recovery was considered tolerable. The species which seriously affect the extraction are Tl(III), In(III), Sn(I1) and Fe(I1, III) for gallium; Tl(III), Ga(II1) and Fe(I1, III) for indium; Pb(II), Bi(III), thiosulphate, thiocyanate, thiourea and ascorbate for thallium. Separation

and &termination

of Ga, In and TI

Tables 3 and 4 show the results for analysis of mixtures containing the three elements, and for analysis of mixtures containing only one of them. Acknowledgemenrs-Thanks are due to the U.G.C., New Delhi, for providing a fellowship for SRK. The authors express their deep sense of gratitude to Dr R. A. Chalmers for his valuable suggestions in the preparation of the manuscript.

CHAVAN

Table 4. Determination of gallium, indium and thallium in synthetic mixtures: results of three determinations of each sample Ga, In or Tl, tng Diverse elements taken, mg Hg(I1) 10, Bi 5, Mn(I1) 10, Zn 5 Mn(II), 15, Pb 5 Bi 5, Sb(II1) 5 Hg(I1) 5, Cd 5, Pb 5, Zn 5 He(B) 5. Cd 2. M;;(B) 10 Al 2.5, Sn(II) 5, Sb(II1) 10

Taken

Found

14OGa 14OGa

1.40, 1.40, 1.39 1.39, 1.42, 1.42

2.57 In 2.57 In

2.57, 2.53, 2.55 2.49, 2.52, 2.52

2.31 Tl

2.25.I 2.23.I 2.30

2.31 Tl

2.31, 2.30, 2.31

REFERENCES A. R. Prabhu and S. M. Khopkar, J. Sci. Ind. Research, 1971, 30, 16. J. Stary, The Solvent Extraction of Metal Chelates, Pergamon Press, Oxford, 1964. A. A. Vasilyeva, I. G. Yudelevich, L. M. Gindin, T. V. Labian, S. R. Shulman, I. L. Kotlarevsky and V. N. Andrievsky, Talanta, 1975, 22, 745. 4. C. Pohlandt and T. W. Steele, Natl. Inst. Metallurgy, Johannesburg,

Repf. No. 1881, 1977.

5. C. Pohlandt, Talanta, 1979, 26, 199. 6. A. K. De and A. K. Sen, ibid., 1967, 19, 629. 7. M. M. L. Khosla, S. R. Singh and S. P. Rao, ibid., 1974, 21, 411.

8. M. B. Chavan and V. M. Shinde, Chem. Anal. (Warsaw), 1974, 19, 1183. 9. S. B. Gawali and V. M. Shinde, Anal. Chem., 1976,48, 62.

10. S. D. Shete and V. M. Shinde, Analysr, 1982, 107,225. 11. M. B. Chavan and V. M. Shinde, Anal. Chim. Acta, 1972, 59, 165.

12. Idem, Sepn. Sci., 1973, 8, 285. 13. F. J. Welcher, The Analytical Uses of Ethylenediaminetetraacetic Acid, pp. 177, 180, 183. Van Nostrand, New York, 1961.