Analytica Chimica Acta, 167 (1985) 403-407 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

Short Communication

COLUMN EXTRACTION SEPARATION OF BERYLLIUM WITH TRIBU’IYL PHOSPHATE IN THIOCYANATE MEDIA

CHHAYA SHARMA and S. M. KHOPKAR*

Indian Institute of Technology, Powai, Bombay 400 076 (India)

(Received 11th April 1984)

Summary. Beryllium is extracted from 2 M ammonium thiocyanate onto a silica gel column impregnated with tributyl phosphate and eluted with 0.1 M hydrochloric acid before spectrophotometric determination with eriochrome cyanine R. Beryllium can be separated from binary and tertiary mixtures by taking the advantage of differences in extractability and elution characteristics of the various elements. The method is used to determine beryllium in beryl.

Tributyl phosphate [l] has been used for the liquid-liquid extraction of beryllium, but the method had little practical utility because extraction was possible only from 0.1 M hydrochloric acid containing 14 M lithium chloride and was not quantitative. The addition of salicylic acid offered no special advantages [2]. In order to improve the selectivity of beryllium separations, attempts were made to utilize tributyl phosphate in reversed-phase paper chromatography [ 31 and extraction chromatography. Beryllium was also separated from manganese and zinc by extraction chromatography on a Fluoroplast column [4]. However, there has been no systematic investiga- tion of the extractionchromatographic separation of beryllium from associ- ated elements with tributyl phosphate as extractant. Little work on column separations has been reported, although some information is available on paperchromatographic separations of beryllium with various extractants [ 5-71. This communication presents a method for the extraction separation of beryllium from binary and tertiary mixtures with tributyl phosphate coated on a silica gel column from thiocyanate media.

Experimental Apparatus and reagents. The apparatus used was similar to that used

earlier [8]. A beryllium solution was prepared by dissolving 0.047 g of beryllium-nitrate tetrahydrate (BDH AnalaR) in 250 ml of distilled water containing 1% nitric acid. The solution, standardized gravimetrically [9], contained 4.24 mg Be ml-‘. A solution containing 10 Erg Be ml-’ was pre- pared by appropriate dilution. The silica gel was hydrophobized and coated with tributyl phosphate as described earlier [ 81.

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General procedure. To an aliquot containing 10 I.cg of beryllium, ammo- nium thiocyanate was added to give a concentration of 2 M. The solution was passed through the column at 1 ml min-‘. The extracted beryllium was stripped with a variety of mineral acids and salt solutions. Ten 2-ml fractions were collected and the beryllium in each fraction was determined spectro- photometrically as its complex with eriochrome cyanine R at 510 nm [lo].

Analysis of beryl. A sample of beryl was dissolved as described earlier [ll] . An aliquot was made 2 M in ammonium thiocyanate and passed

* through the column at 1 ml mm -l. Sodium, potassium passed through the column, extracted aluminium with traces of calcium and magnesium were eluted with 0.2 M ammonium acetate. Beryllium was eluted with 0.1 M hydrochloric acid, and determined as described above.

Results and discussion In batch experiments [ 111, beryllium was quantitatively extracted with

50% tributyl phosphate in toluene from 0.5 M hydrochloric acid in the pres- ence of 5 M ammonium thiocyanate. It could be stripped with 1 M sodium hydroxide. However, it was not possible to use similar conditions in the column work.

The concentration of ammonium thiocyanate was varied from 0.5 to 5 M. The effect on beryllium extraction is shown in Fig. 1. Extraction was quanti- tative from 2-4 M ammonium thiocyanate; all subsequent extractions were done from 2 M ammonium thiocyanate.

After extraction, beryllium was stripped with various mineral acids and salts. It was found that 0.14 M hydrochloric acid, l-5 M nitric acid, l-4 M sulphuric acid or 0.1-l M ammonium chloride quantitatively eluted beryl-

t 70’

5 60-

; 0 SO- : ; bO-

3---_ 0 1 2 3 i 5 6

M of Thuxyantie -

Fig. 1. Effect of thiocyanate concentration on extraction of beryllium.

lium from the column. However, 0.01-0.25 M ammonium acetate did not strip any beryllium, 0.5-l M only removed 10% of the beryllium, and even 2 M did not give quantitative removal.

Separation of beryllium from binary mixtures. Unlike beryllium, some elements (alkali metals, lead, nickel, molybdenum, silver, tin) were not extracted from 2 M ammonium thiocyanate, thus they passed through the column. The retained beryllium was stripped with 0.1 M hydrochloric acid, which enabled beryllium to be separated from various ions at concentration ratios of 1:lO (w/w) (Table 1).

Other elements including the alkaline earths, aluminium, manganese and cobalt coextracted with beryllium. Because 0.01-0.25 M ammonium ace- tate was a poor stripping agent for beryllium, but an effective stripping agent for these other elements, the latter were eluted with 0.2 M ammonium ace- tate and beryllium was subsequently eluted with 0.1 M hydrochloric acid.

Separation of beryllium from tertiary mixtures. There are various possi- bilities for separating tertiary mixtures. For example, if a mixture containing caesium, lead or nickel, cadmium or aluminium, and beryllium was passed through the column, caesium, lead or nickel was not extracted and passed through the column. Cadmium or aluminium could be eluted with 0.2 M

TABLE 1

Separation of beryllium (10 fig) from binary mixtures

Metal ion

Amount Be taken found* (me) (rg)

Recovery W)

Column wash solution

Li Na K Rb cs Mg Ca Sr Ba V(V) Mo( VI) Mn co

4

Cd Al Sn Pb

10.0 9.7 97 2 M NH,SCN, 30 ml 5.0 10.0 100 2 M NH,SCN, 20 ml 5.0 9.5 95 2 M NH,SCN, 25 ml 5.0 10.0 100 2 M NH,SCN, 20 ml 5.0 9.8 98 2 M NH,SCN, 20 ml 2.5 9.8 98 0.2 M NH,Ac, 20 ml 5.0 10.0 100 0.2 M NH,Ac, 15 ml 5.0 9.8 98 0.2 M NH,Ac, 15 ml 5.0 10.2 102 0.2 M NH,Ac, 20 ml 5.0 10.2 102 0.2 M NH,Ac, 20 ml

10.0 10.0 100 2 M NH,SCN, 30 ml 4.1 10.0 100 0.2 M NH,Ac, 20 ml 5.0 9.8 98 0.2 M NH,Ac, 20 ml 5.0 9.7 97 2 M NH,SCN, 20 ml 5.0 9.8 98 2 M NH,SCN, 30 ml 2.9 10.0 100 0.2 M NH,Ac, 15 ml 2.4 10.1 101 0.2 M NH,Ac, 15 ml 2.5 9.9 99 0.2 M NH,Ac, 15 ml 5.0 9.5 95 0.2 M NH,Ac, 30 ml 5.0 10.2 102 2 M NH,SCN, 26 ml

*Be eluted with 10 ml of 0.1 M HCl.

406

ammonium acetate and beryllium could then be stripped with 0.1 M hydro- chloric acid. For a nickel/beryllium/iron(III) mixture, nickel was not ex- tracted, beryllium was eluted with 2 M hydrochloric acid and iron with 0.2 M hydrochloric acid. At >2 M hydrochloric acid, iron(II1) formed solvated species with hydrochloric acid and tributyl phosphate and remained on the column. The results are given in Table 2.

Analysis of beryl. Results of triplicate analyses of various beryl solutions are shown in Table 3. The beryllium values compare well with those found by atomic absorption spectrometry (a.a.s.), and show the effectiveness of the method, which took 2 h. The separations used will be useful for determina- tions of beryllium in other minerals and in fission products.

TABLE 2

Determination of beryllium in tertiary mixtures

Metal ions

Weight (me;)

Taken Found*

Recovery (%)

Eluting agent

Pb 2.00 2.02 Cd 1.50 1.45 Be 0.010 0.0096

Ni 2.50 2.40 Al 1.00 0.98 Be 0.010 0.0094

Ni 2.00 1.94 Be 0.010 0.0098 Fe( HI) 1.00 0.97

Pb 2.00 2.00 Al 1.00 0.99 Be 0.010 0.0098

CS 1.00 0.995 Cd 1.50 1.46 Be 0.010 0.0098

*Determined speclrophotometrically [ 121.

101 2 M NH,SCN, 25 ml 96 0.2 M NH,Ac, 15 ml 96 0.1 M HCl, 10 ml

99 2 M NH,SCN, 20 ml 98 0.2 M NH,Ac, 20 ml 94 0.1 M HCl, 10 ml

97 2 M NH,SCN, 20 ml 98 2 M HCI, 10 ml 97 0.1 M HCl, 50 ml

100 2 M NHJCN, 25 ml 99 0.2 M NH,Ac, 20 ml 98 0.1 M HCl, 10 ml

99.5 2 M NH,SCN, 26 ml 97 0.2 M NH,Ac, 16 ml 95 0.1 M HCl, 10 ml

TABLE 3

Analysis of beryl

Sample no.

Beryllium found (96)

Present method A.a.8.

1 4.5,4.4,4.3 4.2,4.2,4.2 2 4.7, 5.0, 5.0 5.0, 5.0, 6.0 3 5.0,5.0, 5.0 6.0, 5.0, 5.1 4 4.0,4-o, 4.0 4.0, 4.0,4.0

407

We thank the Council of Scientific and Industrial Research, New Delhi, for sponsoring this project and awarding Junior Research Fellowship to one of us (C. S.).

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