Journal o f Radioanalytical Chemistry, Vol. 33 (19 76] 123-128

C E R T A I N M I C R O - C H E M I C A L S E P A R A T I O N S U S I N G H Y D R O U S F E R R I C O X I D E AS A S E L E C T I V E S O R B E N T

II. SEPARATION AND DETERMINATIONS OF SMALL AMOUNTS OF CADMIUM FROM COPPER AND FROM NICKEL

BRIJ BHUSHAN, K. R. KAR

Department of Chemistry, University of Delhi, Delhi (India)

(Received October 15, 1975)

Traces of cadmium from relatively high amounts of nickel and ~opper can be separated by the selective sorption of the cadmium ethylenediamine complex on hydrous ferric oxide. A batch chromatographic technique has been elaborated on this basis.

Introduction

None of the s p e c t r o p h o t o m e t r i c methods 1-2 is app l i cab le for the de =

t e rmina t ion of c a d m i u m in the p r e s e n c e of l a r g e amounts of c o p p e r / n i c k e l

(>200 ppm) without t he i r p r i o r s epa ra t ion . Thus fo r ana ly s i s of the

m i x t u r e s containing l a r g e amounts of c o p p e r / n i c k e l , a p r i o r chemica l s e -

pa r a t i on of the cons t i tuents is i m p e r a t i v e . A n u m b e r of column methods

3-6 in which have been worked out fo r the p u r p o s e by d i f fe ren t w o r k e r s ,

the final s e p a r a t i o n is based m os t l y on elution with so lven t s . However ,

the e f f ic iency of s e p a r a t i o n is dependent on the co lumn length; i f the length

of the co lumn is not enough, the re a r e chances of the n e a r b y ca t ions c o m -

ing into the solut ion. In an a t t em p t to i m p r o v e the s i tuat ion, the s e l ec t iv i t y

of hydrous f e r r i c oxide towards the e thy lened iamine complexes of Cd, Cu

and Ni was inves t iga ted . P r e l i m i n a r y s tud ies , involving the use of l l 5 c d

as the r ad ioac t ive ind ica tor , r evea l ed that f r o m the aqueous m i x t u r e of

Cd, Cu and Ni in p r e s e n c e of e thy lened iamine , Cd a lone is so rbed by the

J. Radioanal. Chem. 33 (1976) 123

9*

B. BHUSHAN, K.R. KAR: CERTAIN MICRO-CHEMICAL, II.

so rben t to the complete exclusion of the o ther const i tuents . Fur the r the

absorbed Cd could be brought into solution, by eluting with 0.08N ace t ic

acid. On the basis of these observa t ions , a method has been worked out,

which may be used for the chemica l separa t ion of t r a ce s of Cd f rom r e -

la t ively la rge quanti t ies of Cu and Ni. The p r e s e n t paper r ep o r t s the r e -

sul ts of the invest igat ion, including chemica l separa t ion and d e t e r m i n a -

tion of the separa ted components .

Experimental

M a t e r i a l s a n d m e t h o d s .

F o r r a d iome t r i c de te rmina t ions , spec t ropho tome t r i c de te rmina t ions ,

p H - m e a s u r e m e n t s , exchanger ma te r i a l and p repa ra t i on of s tandard solu-

tions of b inary mix tures , see Par t I of this s e r i e s of communicat ion.

R a d i o a c t i v e i s o t o p e , l l 5 c d [ T = 4 3 d; chemica l f o rm

Cd(NO3) 2 in dil. HNO 3 solut ion] was obtained f ro m the isotope divis ion,

BARC, Bombay, India.

T e m p e r a t u r e . Al l the expe r imen t s w e r e c a r r i e d out at a t e m p e r a -

tu re of 25 + 2 ~ in a l abora to ry provided with a C l ima t i ze r a i rcondi t ioner .

P r o c e d u r e

A. R a d i o m e t r i c i n v e s t i g a t i o n f o r d e t e r m i n a t i o n o f

e x p e r i m e n t a l c o n d i t i o n s . The p r o c e d u r e is essen t ia l ly the

same as desc r ibed in Par t I of this communicat ion, except l l 5 c d was

used in the b inary mix tu res of cadmium with copper and nickel.

B. S e p a r a t i o n a n d d e t e r m i n a t i o n o f C d ( I I ) i n i t s

b i n a r y m i x t u r e s w i t h C u ( I I ) o r N i ( I I ) . A t y p i c a l s e p a r a -

t ion of Cdfll) f r om Cu(II) is desc r ibed .

To 25 ml por t ion of the alkal ine (ethylenediamine, pH ca 8.5) mix-

tu re containing 1.25 to 20#g of Cd(II) and <120 000/~g of Cu(II) is

124 J. Radioanal. Chem. 33 (1976)

B. BHUSHAN, K. R. KAR: CERTAIN MICRO-CHEMICAL, II.

added 600 mg of the hydrous f e r r i c oxide. The mix tu re is shaken mechani -

ca l ly fo r about 3 .5 h r s . By this t r ea tmen t , the en t i r e quant i ty of Cd(lI) is

taken up by the exchanger ma te r i a l , leaving Cu(II) in the supernatant . The

c l e a r solut ion is s epa ra t ed by centr i fugat ion and p r e s e r v e d for the de-

t e rmina t ion of Cu(II). The exchanger ma t e r i a l containing the absorbed

Cd(II) is washed with water , whose pH is adjusted to 8.5 by adding e thylene-

d iamine, and the washing is added to the superna tan t solut ion. The de-

pos i ted Cd(lI) is brought into the solut ion by 2 x 10 ml of 0.08N ace t i c

acid.

The sepa ra ted cat ions a r e de t e rmined as follows:

(I) Cadmium - by the spec t ropho tome t r i c method 2 using PAN as co lour

fo rming reagent , a t 550 nm of the v is ib le sp ec t ru m .

(II) Copper - the complex is f i r s t decomposed with dilute hydroch lo r i c

acid and sodium n i t r i t e and then the amount of Cu(II) is d e t e rm in ed by 7

t i t ra t ing against 0 .01M EDTA solution in conjunction with murex ide as

indica tor .

Exac t ly the same p r o c e d u r e can be applied for the separa t ion of

Cd(II) f r om Ni(lI), and the sepa ra ted meta ls can then be de t e rmined as

above, (I) Cd - spec t ropho tome t r i ca l l y 2 and (II) Ni - by co m p lex o m e t r i c 7

t i t r a t ions .

Tes t ing the e f f ic iency of the separat ion: The poss ib le so u rce s of

e r r o r in the analys is due, namely, to (I) re ten t ion of the Cu ions along

with the Cd(II) in the exchanger , (II) re ten t ion of the Cd(II) in the su p e r -

natant solution containing CuflI) ions and fllI) passage of Fe ions (ex-

changer mate r ia l ) during elution in the eluate, have been ca re fu l ly examin-

ed.

The absence of Cd(II) in the superna tan t was conf i rmed r a d i o m e t r i c a l -

ly us ing l l S c d as rad ioac t ive indicator , and the passage of Fe(III) ion

J.. RadioanaL Chem. 33 (1976) 125

B. BHUSHAN, K. R. FAR: CERTAIN MICRO-CI-~EMICAL, II.

in t~e eluate was checked by its spot t e s t with a , a ' -dipyridyl . 8 F o r

checking the re ten t ion of Cu(II) in the exchanger ma te r i a l , the [ Cu(en) 3]

complex solution of the specif ied concent ra t ion was individually shaken,

washed and eluted as desc r ibed in the p roced u re . A smal l f rac t ion of the

eluate was then tes ted for Cu(II) with sa l icyla ldoxime; 9 Absence of Cu(II)

in the exchanger is a lso indi rec t ly indicated by its comple te r e c o v e r y in

the superna tan t I/quid (Table 2).

2+

The resu l t s p r e sen t ed in Table 1-3 show that smal l quanti t ies of

Cd(II) (1.25 to 20 /~g) can be sepa ra ted f r o m re l a t ive ly l a rge quant i t ies

of Cu(II) or Ni(II), p e r 600 mg of the hydrous f e r r i c oxide used as sorbent .

Table 1

P r e l i m i n a r y invest igat ion of deposi t ion and r e c o v e r y of

Cd(II) on hydrous f e r r i c oxide using 115mCd Amount of the hydrous f e r r i c oxide = 600 mg; pH 8.5;

t ime of shaking = 3 .5 hrs

Sample, No

1

2

3

4

5

�9 6 ~

7

~8-

9

Cd(II) pe r 25 ml sample init ially, ~ g

1.25

2.50

5.00

I0 .00

15.00

2O.OO

25.00

50 :00

100 ;'GO

Cd(II) lef t back in solut ion a f t e r shak-

ing, /~ g

Nil

Nil

Nil

Nil

Nil

Nil

0 .30

1.50

39.84

,2d(II) r e c o v e r e d on elution, /~g

1.24

2 .48

4 .90

9.98

15.02

20.00

24.20

49.00

60.00

J. Radioanal. Chem. 33 (1976)

B. BUSHAN, K. R. KAR: CERTAIN MICRO -CHEMICAL, II.

Table 2

Separation and determination of Cd(II) and Cu(II) in mixtures.

Amount of the exchanger = 600 mg; pH 8.5; time of shaking = 3.5 hrs

Composition of Amount of metal ions Amount of metal mixtures before separation left in the supernatant ions in the eluate

~3d(lI), Cu(II), Cd(II), Cu(II), Cd(II), Cu(II), Pg /~g /~g p g /~g /~g

3.206

6.413

9.618

12.825

15.330

19.238

22.444

20 000

20 000

20 000

20 000

20 000

20 000

20 000

Nil

Nil

Nil

Nil

Nil

Nil

Nil

20 000

20 000

20 000

20 000

20 000

20 000

20 000

3. 276

6.480

9.675

12. 740

15. 370

19. 500

22. 300

Nil

Nil

Nil

Nil

Nil

Nil

Nil

It may be pointed out that even micro quantities of Cu(II) or Ni(II) can be

freed f rom the Cd(II) by the same procedure; st i l l l a rger quantities of the

Cd(II) can also be completely removed by simply increasing the amount of

the sorbent. By using l l 5 c d as a radioactive t racer , it has been shown that

the method is applicable for the complete separation of even up to one

microgram of Cd(II) f rom a mixture of Cu(II) or Ni(II).

The mechanism of separation is postulated to be:

~ F e - OH OH,.- .~Fe_O- + H O 2

[Cd(en) 3 ] 2+ --~Fe--<) [ ~. Cd(en) 3]

J. Radioanal. Chem. 33 {1976) 1 2 7

B. BHUSHAN, IL R. KAR: CERTAIN MICRO-CHEMICAL, II.

T a b l e 3

S e p a r a t i o n and d e t e r m i n a t i o n of Cd( l I ) and Ni(II) in m i x t u r e s

A m o u n t of the e x c h a n g e r = 600 rag; pH 8 .5 ; t i m e of s h a k i n g = 3 . 5 h r s

C o m p o s i t i o n of m i x t u r e s b e f o r e s e p a r a t i o n

Cd(II) , ~ g

3.206

6.413

9.618

12.825

15.330

19.238

22.444

Ni(n), /~g

30 000

30 000

30 000

30 000

30 000

30 000

30 000

t C h e c k e d w i t h D. M. G.

A m o u n t of m e t a l i ons l e f t in the s u p e r n a t a n l

A m o u n t of m e t a l i ons in the e l u a t e

Cd( I ] ) , /~g

Cd(II ) , Ni( I I ) , /~g ~ g

Nil 30 000

Nil 30 000

Nil 30 000

Nil 30 000

Nil 30 000

Nil 30 000

Nil 30 000

3. 100

6 . 1 3 9

9 . 8 2 5

12 .740

15 .385

19 .250

;22. 500

Ni(II) ~

Nil

Nil

Nil

Nil

Nil

Nil

Nil

One of the authors (B. B.) is thankful to the Council of Scientific and Industrial Research, India, for providing financial assistance.

References

1. E. B. SANDELL, Colorimetric Determination of Traces of Metals, Interscience, New York, 1959.

2. H. A. FLASHKA, A. J. BARNARD, Chelates in Analytical Chemistry, Marcel Dekker, New York, 1972.

3. Y. YOSHINO, M. KOJIMA, Japan Analyst, 5 (1955) 311. 4. F. W. E. STRELOW, Anal. Chem., 32 (1960) 1185. 5. J. S. FRITZ, T. A. RETTING, Anal. Chem., 34 (1962) 1562. 6. F. W. E. STRELOW, A. H. VICTOR, C. R. VANZYL, C. ELOFF, AnaL Chem., 43 (1971) 870. 7. G. SCHWARZENBACH, Complexometric Til~ations, Interscience, New York, 1960. 8. F. FEIGL, Spot Tests in Inorganic Analysis, Elsevier, 1958, p. 482. 9. F. FEIGL, Spot Tests in Inorganic Analysis, Elsevier, 1958, p. 83.

128 Z RadioanaL Chem. 33 (1976)