IEA-PUB-24
SEPARATION OF BISMUTH FROM LEAD W I T H
(EHTYLENEDINITRILO) TETRAACETIC ACID
A P P L I C A T I O N TO R A D I O C H E M I S T R Y
SEPARAÇÃO DE BISMUTO E CHUMBO COM ÁCIDO ETILENODIANINOTETRAACÉTICO (EDTA) — APLICAÇÃO Ã RADIOQUÍMICA
F.
W.
LIMA
e. A.
ABRÃO
c
Publicação
24
I E A
I960
INSTITUTO DE ENERGIA
Caixa
Postal
11049
ATÔMICA
(Pinheiros)
CIDADE UNIVERSITÁRIA "ARMANDO DE SALLES OLIVEIRA"
SÃO PAULO — BRASIL
• V.
CONSELHO
Pi-esidente — Prcf.
Vice-Presidente
Dr.
NACIONAL
João
DE
Christovão
— Prof. D r . A t h o s
UNIVERSIDADE
PESQUISAS
DE
Cardoso
da S i l v e i r a
SÃO
Ramos
PAULO
R e i t o r — Prof. D r . G a b r i e l S y l v e s t i e T e i x e i r a d e C a i v a l h o
V i c e R e i t o r — P r o f . Dv. F r a n c i s c o J o ã o H u m b e r t o
INSTITUTO
Maffei
DE
ENERGIA
ATÓMICA
DIRETOR
Prof. Dr. Marcello D a n i y de S o u z a
CONSELHO
TÉCNICO-CIENTÍFICO
Rcpreíénlanles
do
Conselho
P r o f . Dr. Luiz Cintra do
Prof. D r . P a i i l u s
Repi'esenlantes
Aulus
da
Prof. D r . F r a n c i s c o
Prof. D r . J o s é
Sanios
de
Pesquisas
Pornpéia
Universidade
João
Moura
CONSELHO DE
Nacional
Prado
c'e
Humberto
São
Paulo
Maffei
Gonçalves
PESQUISAS
Prof. Dr. M a r c e l l o D a m y
de Souza
Santos
— C h e f e d a D i v i s ã o de Fí.sica
I^i-of. E n g . P a u l o S a r a i v a
de
— C h e l a da D i v i s ã o
Prof. Dr. FaiLSto W a l t e r L i m a
de
— C h e f e da D i v i s ã o de
I-'rcf. D r . P ó m u l o R i b e i r o
Nuclear
Toledo
Fisica
de
Radiocuu'niica
Pieroni
— C h e f e d a D i v i r ã o de
Radiobiología
Reatores
Reprinted from A N A L Y T I C A L C H E M I S T R Y , VoL 3 2 , P a g e 4 9 2 , April 1960
Copyright 1960 by the American Chemical Society and reprinted by permission of the copyright owner
Separation of Bismuth from Lead with
(Ethylenedinitrilo)tetraácetic Acid
Application to Radiochemistry
FAUSTO W . LIMA and ALCÍDIO
Radiochemistry
Division,
P- Bismuth
can
be
separated
from
lead
Instituto
ABRÃO
de Energia
radiochemically
b y using
(ethyl-
e n e d l n i t r i l o ) t e t r a a c e t i c a c i d in a m o d i fication of the p r o c e d u r e p r o p o s e d b y
Pribll
and
successful
tracer
Cuta.
The
when both
separation
elements
is
are at
c o n c e n t r a t i o n o r w h e n o n e (or
b o t h ) o f t h e m is a t m a c r o c o n c e n t r a t i o n .
A
single-step
covery
separation
greater
than
permits
9 0 %
of
rebolh
elements with p r a c t i c a l l y no c o n t a m i n a tion.
and
The
rapid
completed
procedure
involves
manipulation
in
less
than
simple
and can be
15
minutes,
w h i c h is i m p o r t a n t w h e n t h e h a l f
lives
o f the isotopes a r e short.
P
a n d Cuta (7) described a
separation of b i s m u t h from lead
when both cations a r e present in more
t h a n tracer concentration. T h i s separation is accomplished b y complexing
t h e elements with (ethylcnedinitrilo)tetraacetie acid ( E D T A ) a n d then
a d d i n g calcium ion vvliich replaces
bismuth in t h e E D T A complex. If t h e
solution is slightly ammoniacal, b i s m u t h
is precipitated as t h e hydroxide a n d
can be filtered off. F o r gravimetric
purposes, it is necessary to add equivalent a m o u n t s of calcium n i t r a t e a n d
E D T A to t h e lead-bismuth solutions;
by using a large excess of t h e calcium
salt, t h e precipitated bismuth hydroxide
always contains some calcium, and it is
nece.ssai-y to dissolve a n d rcpurifj' it (7).
T h e present a u t h o r s have observed t h a t
t h e excess of calcium n i t r a t e added to
t h e l e a d - E D T A solution, in ammoniacal
media, will sliglitK' c o n t a m i n a t e tlie
bismuth hydroxide with lead a n d
reprecipitation is necessary.
HIBIL
T h e separation of lead from b i s m u t h
is always an i m p o r t a n t radiochemical
probl(;m, as isotoj^es of b o t h elements
often occur togi'ther—for
instance,
in nuclcai- processes such as lead-204
(d, 2n) bismuth-204 a n d lead-206
(d, 2n) bismuth-206 (9, 10), a n d in
n a t u r a l radioactive lead-bismuth mixtures previously scisaratcd in t h e uranium, thorium, a n d actinium series.
T o obtain radiochemically pure lead212 a n d bismuth-212, R u d e n k o {S)
492
•
ANALYTICAL CHEMISTRY
Atômica,
CP.
11049
{Pinheiros),
São Paulo,
devised a method in which b i s m u t h a n d
lead a r e precipitated as b i s m u t h gállate
a n d lead sulfide, respectively. T i t r a tion of bismuth with E D T A in t h e
presence of large a m o u n t s of lead has
been described by Fritz ( / ) . Traces
of lead h a v e been separated a n d determined in t h e presence of small a m o u n t s
of b i s m u t h by Moore {6), who precipit a t e d bismuth sulfide with copper as a
carrier in hydrochloric acid m e d i u m ;
lead remains in t h e filtrate.
T h e classical separation of lead from
b i s m u t h b y precipitating b i s m u t h h y droxide with sodium hydroxide a n d
forming sodium plumbite, which is
soluble, has t h e d i s a d v a n t a g e t h a t some
lead is entrained with t h e bismuth
precipitated. Also, b i s m u t h is somew h a t soluble in t h e excess sodium
hydroxide required to form t h e lead
plumbite a n d each fraction is contaminated by t h e other element.
S t a r t i n g with t h e m e t h o d suggested
by Pfibil and Cuta (7), a new m e t h o d
has been devised for the separation of
lead from bismuth, whatever their
relative concentrations, which avoids
t h e use of calcium t o dissociate t h e
b i s m u t h - E D T A complex; t h e method
is especially useful in radiochemical
problems when one or b o t h elements
are present a t tracer level.
PRINCIPLES O F METHOD
Pfibil and Cuta (7) h a v e called a t t e n tion t o t h e different behavior of bivalent a n d trivalent metals with E D T A
in connection with the possibility of
precipitating t h e metals from E D T A
solutions with a m m o n i u m hydroxide.
T h e bivalent metals form very stable
complexes with E D T A , which, with t h e
exception of beryllium, cannot be precipitated o u t of solution by a m m o n i u m
hydroxide. Some of t h e trivalent
m e t a l - E D T A complexes are also very
stable even in relatively acid solutions
and cannot be precipitated with a m monium hydroxide. However, sodium
hydroxide will effect precipitation a n d
W'ill do so quantitatively, imless t h e
amphoteric character of t h e metal
Brazil
prevents this reaction, as is t h e case
with a l u m i n u m (7).
T h e facts observed by t h e a b o v e
a u t h o r s suggested t h a t t h e system of
l e a d - b i s m u t h E D T A complexes could
be resolved a n d both cations separated
b y using only sodium hydroxide as
precipitant, as it is n o t necessary t o use
calcium to replace t h e t r i v a l e n t m e t a l in
t h e complex.
T h e complexing efficiency of E D T A
with b i s m u t h is greatly affected by t h e
hydrolytic effect a t high p H values.
By adding sodium hydroxide t o a mixture of t h e E D T A complexes of b i s m u t h
a n d lead, b i s m u t h is precipitated as t h e
hydroxide, a n d as no large excess of
alkali is required to form t h e soluljle
sodium plumbite, t h e inconvenience of
dissolution of some b i s m u t h hj'droxide
is avoided. I n t h e procedure described
in t h e present paper, t h e a m o u n t of
sodium hydroxide a d d e d t o t h e mixture
of E D T A complexes of lead a n d b i s m u t h
m i g h t be determined b y t h e Phenolphthalein end point. However, because a slight excess of E D T A p r e v e n t s
a q u a n t i t a t i v e ijrecipitation of b i s m u t h
in solution m a d e alkaline against Phenolphthalein, a n excess of sodium hydroxide
was u.sed over t h e end point of t h e
indicator, t h e final sodium hydroxide
concentration being a b o u t Q.IM. A t
this concentration t h e a m o u n t of sodium
hydroxide present is n o t large enough
t o dissolve t h e b i s m u t h hydroxide
formed, b u t it is sufficient t o precipitate
t h e b i s m u t h from t h e solution of E D T A .
APPARATUS A N D REAGENTS
T h e activities of t h e radioisotopes
were determined in a mica window
Geiger counter with 1.2 mg. per sq.
cm. of window thickness. A decimal
scaling unit. Model 166 (Nuclear
Chicago Corp.), was used as a register.
For g a m m a scanning, a one-channel
pulse analyzer ( I n s t i t u t o de Energia
Atômica) was used; a linear amplifier
(Technical M e a s u r e m e n t Corp.), Alodel
A1-4A, a decimal scaler, Model 181-A,
a n d a sodium iodide-thallium wellactivated scintillation crystal, Model
X T - 1 0 0 (both from Nuclear-Chicago
Corp.) were also used. T h e g a m m a -
countiiig system was standardized by
using i(>ad-210 (0.047 m.e.v.), cadmium109 (0.087 m.e.v.), tin-113 (0.393
m.e.v.), a n d cesiuin-137 (0.G()2 m.e.v.)
sources.
Lead nitrate tagged with lead-210
was obtained fi-om C a n a d i a n R a d i u m
and U r a n i u m Corp., and was ijurified
by pulp-paper chromatographic techniques using butyl alcohol in a S^V
solution of hydrochloric acid ( 4 , S).
Spectrographic analysis of t h e purified
mateiial is presented in Table I.
Carrier-free lead-210 a n d bismuth-210
were obtained from old r a d i u m t u b e s
used for radiotherapy. T h e tubes were
smeai'cd with a piece of cotton which
was then t r e a t e d with nitric acid, the
solution was filtered a n d made O.LV
in nitric acid, and lead and bismuth
were deposited by electroly.sis on platinum electrodes which were boiled in
nitric acid 1 t o 1 to remove t h e radioisotopes.
The E D T A was of analytical grade
and was purified further hy dissolution
in a m m o n i u m hydroxide a n d precipitation twice with liydrochloric acid.
A standard solution was m a d e hy weighing t h e required a m o u n t of acid t o
make a O.IM solution, dissolving it in
a m m o n i u m hydroxide, ascei'taining t h e
p H t o S.O, a n d t i t r a t i n g w'ith m a g nesuim chloride using Eriochrome Black
T as indicator. Solutions of other concentrations in E D T A were m a d e by
dilution.
PROCEDURE
The experiments were m a d e in four
groups depending on t h e relative
a m o u n t s of bismuth a n d lead. In
group A, macro a m o u n t s of lead a n d
bismuth were present; in group B,
lead was a t macro a m o u n t and bismutli
a t tracer level; in group C, lead was a t
tracer level a n d bismuth in macro
a m o u n t ; a n d in group D , both elem e n t s were a t tracer level.
T h e radioisotope solutions obtained
from t h e nitric acid t r e a t m e n t of t h e
p l a t i n u m electrodes were boiled to eliminate excess of nitric acid a n d m a d e to
volume in 100-ml. volumetric flasks.
Depending on t h e experimental group,
carriers of bismuth a n d / o r lead were
added a t this stage and t h e mixture
was considered ready for separation.
T h e concentrations of the solutions
in t h e various groujis w-ere l l . S m g .
per ml. of lead ion (groups A and 13)
a n d 13.4 mg. per ml. of bismuth ion
(groups A a n d C ) . T h e a m o u n t s of
radioactive isotopes of b o t h elements
in all four groups were from 0.006 t o
0.2 /ic. per ml. of solution of lead-210
in secular equilibrium with bismuth-210.
For t h e same set of experiments t h e
concentration of t h e radioactive isotopes in t h e original solution was t h e
same.
For t h e experiments, 1 ml. of solution
was t a k e n to a beaker a n d the volume of
0.0 I M E D T A solution required for
comi.)lexation of t h e metals was added.
F o r t h e e.xperiments in group D , where
bismuth a n d lead were a t tracer concentration, t h e volume of 0.01 M E D T A
was 1 ml. T h e solution was t r e a t e d
with \N sodium hydroxide until the
formation of a p e r m a n e n t i.jink color
of phenolphtlialein indicator, t h e n a n
excess of alkali was added, a n d the
voliune was m a d e to 20 ml.; the final
concentration of sodium h j droxide was
O.l.W. A t this stage bismuth is precipitated as t h e hydroxide or there is
tiie formation of a radiocolloid if it is
present a t trace concentration, t h e recovery of bismuth being over 9 8 % .
All steps were carried o u t on a h o t
plate.
Table
Lead
I.
Spectrographic
Nitrate
Tagged
Analysis
with
of
Lead-210
A f t e r C h r o m a t o g r a p h i c Purification
Per C e n t
Al
Si
0.002
0.0005
0.0001
0.00U3
0.001
0.0001
0.0001
Ca
Cu
Fe
Mg
Ag
RESULTS A N D DISCUSSION
T j p i c a l results for the percentage of
contamination of tlic lead fraction witli
bismuth on t h e various groups of experim e n t s are ¡íresented in Table I I . D a t a
are given for t h e cases where t h e precipitation was carried o u t by t h e
method descrilied in this paper a n d , for
com))arison, b y using only sodium
hydroxide without previous complexation of t h e cations. T h e percentage of
cont:i,m i nation was calculated by using
the formula given in {S)—i.e.,
a =
1 -
(.4'
/ l " ) / . - ! ' e.xp ( - X Í " ) -
P e r C e n t Bismuth C o n t a m i n a t i o n o f O r i g i n a l A m o u n t o f L e a d
A
B
a
b
0.8
0
8.0
5.8
4.8
a
1.7
0
1.0
^
where a is tlie fi'action (contamination)
of bismuth on t h e lead bismuthiol precipitate, A' a n d A" a r e t h e activities of
the precipitate a t times t' a n d t",
respectively, rind X is t h e disintegration
constant for bismutli-210.
Talkie I I shows t h a t contamination
of tlie lead fraction is practically
fdssent for groups A a n d B, as compared
to a lai'ge contamination when no
previous complexntion b y E D T A is
carried out. TIK; largest percentage of
contamination (7.6%) is observed in
grou|) D when botli cations are a t tracer
l(,'vel. Even in this group the results
are much better t h a n wlien t h e classical
method of precipitating witli sodium
hydroxide alone is used, where extremely
high values for contamination are
found.
T h e contamination for the corresponding bismuth fractions of Table 11
was cliecked b y 7-ray spectrometry of
these fractions, ns described. T h e results
are present in Figure 1 for two typical
( C o l u m n s a, c a t i o n s p r e v i o u s l y c o m p l e x e d with E D T A ;
complexation)
0
-
A" exp (— Xt'y
T h e preci|)itate or t h e radiocolloidal
bismuth was filtered off, washed with a
dilute solution of sodium hydroxide
and w^ater, a n d m o u n t e d for counting.
Before filtering, t h e paper ( W h a t m a n
No. 42) w'as t r e a t e d with sodium h_ydroxide solution.
T h e purity of each fi'action, tlie precipitate of bismuth hydroxide and the
soluble lead, were determin(.'d next.
P a r i t y of t h e bisnuith pre-ci|iitated was
chc^cked by g a m m a s|,)ectrometry looking for t h e 0.047-m.e.v. ]:;hotO|,:eak for
lea.d-210. P u r i t y of t h e lead
filtrate
solution was verified by adding bismuth
carrier to t h e filtrate (also, lead carrier
when working with carrier-free lead,
groups A a n d D ) a n d precipitating
both elements with bismuthiol I (2..5d i m e r c a p t o - 1,3,4 - thiodiazol), m o u n t ing t h e precipitates, and counting.
T h e a m o m i t of bismuth jircsent in the
lead fraction was calculat(>d by the
method proposed by Lima (,5).
T a b l e II.
having [ircviously complexed the cations
with E D T A .
T o check t h e i;oasibility of some cont a m i n a t i o n of t h e bismuth hydroxide
l.)reci|)itate witli lead, when t h e bismuth-EDTyV com|.)lcx was broken b y
adding calcium ions, the preci|.)itation of
bismuth hydroxide was also carried
o u t by this technique.
Fractions
colinnns b, no previous
D
C
b
a
b
a
b
.37.0
35.0
9.5
3.8
4.1
4.0
34.0
10.5
11.0
0.1
2,1
7.6
27.0
21.5
15.0
T o compare results, separations were
also carried o u t by t h e classical precipitation of bismuth hydroxide (or
radiocolloid formation if a t tracer level)
with sodium hydroxide a n d by foiining
t h e soluble sodium plumbite, without
preci])itates of each group. Curves a
correspond to t h e bismutli fractions
obtained when t h e two cations in t h e
mixture were previously complexed
with E D T A . Curves b a r e for t h e
eases when bisnuith hydroxide was
VOL. 3 2 , N O . 4, APRIL 1960
•
493
/
\
.J
1000
17K.ty Pb-2I0
500-
- 500
50
—I
S.I000
roo
1
Kev
0
110001
500
50
100 Kev
500
300L
"0
Figure 2 .
25
Gamma-ray
50 GAMMA ENERGY ^ 5 K.ey.
scanning o f bismuth f r a c t i o n
when
c a l c i u m i o n is u s e d t o b r e a k t h e b i s m u t h - E D T A c o m p l e x
Slit width, 20 k.e.v.; gain setting, 4
100
Kev
50
0
100
Kov
GAMMA ENERGr
Figure
1.
Gamma-ray
scanning
o f t h e bismuth
a.
Cations complexed with EDTA
b.
No previous complexation
fractions
Slit width, 2 0 k.e.v.; gain setting, 4
when this ion is used in excess. Figure
2 is a typical scanning of a b i s m u t h
hydroxide precipitate when calcium,
in a n excess of 1 0 % over t h e equivalent
a m o u n t of E D T A , was used t o break t h e
b i s m u t h - E D T A complex.
LITERATURE CITED
precipitated b y sodium hydroxide with
no previous complexation. I n all four
groups t h e results were reproducible
and t h e 47-k.e.v. photoelectric peak of
lead-210 could always be detected in
t h e bismuth fraction t h a t was precipitated without previous complexation with E D T A . B y comparing t h e
areas under t h e curves in Figure 1 with
t h e areas obtained with t h e original
lead-210 solutions, i t is found t h a t t h e
contamination is a b o u t 8 % for t h e case
when t h e cations a r e n o t previously
complexed with E D T A a n d sodium
hydroxide is used a s precipitant.
In groups C a n d D , where lead w a s
present a t tracer level, t h e b i s m u t h
hydroxide precipitate showed some contamination b v lead when an excess of
494
calcium ion was used for disruption of
the E D T A complexes. T h e small increase in concentration of lead ions,
originating from a n eventual exchange
reaction between l e a d - E D T A complex
a n d calcium ions, would favor a n ent r a i n m e n t of lead b y b i s m u t h hydroxide;
This e n t r a i n m e n t would b e in accordance with F a j a n s ' rule {2), because lead
ions, when present in macro a m o u n t s ,
will form t h e insoluble lead hydroxide;
consequently,
in accordance
with
Fajans' rule, lead ions, when a t tracer
concentration, would b e coprecipitated
with b i s m u t h hydroxide. T h e entrainm e n t of lead m i g h t also b e d u e t o a n
occlusion, in t h e b i s m u t h hydroxide,
of some l e a d - E D T A complex together
with t h e calcium ion t h a t is absorbed
ANALYTICAL CHEMISTRY
P H I X T E D I N U . S . A.
( 1 ) Fritz, J. S., ANAL. CHEM. 2 6 , 1 9 7 8
(1954).
( 2 ) H a h n , O., " A p p l i e d R a d i o c h e m i s t r y , "
p. 6 5 , Cornell U n i v e r s i t y Press, I t h a c a ,
N . Y . , 1936.
( 3 ) L i m a , F . W . , ANAL. CHEM. 2 5 , 1 9 2 4
(1953).
( 4 ) L i m a , F . W . , doctor's t h e s i s . U n i v e r s i t y of S ã o P a u l o , Brazil, 1 9 5 5 .
(5) Lima, F . W . , J. Chem. Educ. 3 1 ,
153 ( 1 9 5 4 ) .
( 6 ) M o o r e , V . J . , Analyst
8 1 , 553 (1956).
(7) Pfibil, R . , Cuta, J., Collection Czechoslov. Chem. Communs. 16, 3 9 1 ( 1 9 5 1 ) .
(8) R u d e n k o , M . P . , / . Anal. Chem.
U.S.S.R. {Eng. trans.) 1 1 , 3 8 5 ( 1 9 5 6 ) .
( 9 ) Seaborg,
G.
T.,
Perlman,
I.,
Rev.
Modern Phys. 2 0 , 5 8 5 (1948).
( 1 0 ) T e m p l e t o n , D . H . , H o w l a n d , J . J.,
P e r l m a n , I . , Phys. Rev. 7 2 , 7 6 6 ( 1 9 4 7 ) .
RECEIVED for r e v i e w D e c e m b e r 2 2 , 1 9 5 8 .
A c c e p t e d N o v e m b e r 2, 1959.