Journal of Nuclear and Radiochemical Sciences, Vol. 7, No. 2, pp. 29-32, 2006

Comparative Study on Bromide and Iodide Ion-Isotopic Exchange Reactions Using Strongly
Basic Anion Exchange Resin Duolite A-113
R. S. Lokhande,a P. U. Singare,*,b and M. H. Dolea
aDepartment of Chemistry, University of Mumbai, Vidyanagri, Santacruz, Mumbai-400098, India
Department of Chemistry, Bhavan’s College, Munshi Nagar, Andheri, Mumbai 400 058, Indiab

Received: June 16, 2006; In Final Form: September 4, 2006
Kinetics of ion-isotopic exchange reaction was studied using industrial grade ion exchange resin Duolite A-113. The
radioactive isotopes 131I and 82Br were used to trace the ion-isotopic exchange reaction. The experiments were performed in the temperature range of 26.0 ˚C to 43.0 ˚C and the concentration of external ionic solution varying from0.005 M to 0.100 M. For bromide ion-isotopic exchange reaction, the calculated values of specific reaction rate, initial rate of bromide ion exchange, and amount of bromide ions exchanged were obtained higher than that for iodide
ion-isotopic exchange reaction under identical experimental conditions. The observed variation in the results for two
ion-isotopic exchange reactions was due to the difference in the ionic size of bromide and iodide ions.

1. Introduction
There are number of liquid processes and waste streams at
nuclear power plants, fuel reprocessing plants, and nuclear
research centers that require treatment for removal of radioactive contaminants. One of the most common treatment methods for such aqueous streams is the use of ion exchange, which
is a well developed technique that has been employed for many
years in nuclear industries. The ion exchange process is veryeffective at transferring the radioactive content of a large volume of liquid into a small volume of solid. Efforts to develop
new ion exchangers for specific applications are continuing. In
spite of their advanced stage of development, various aspects
of ion exchange technologies have been continuously studied toimprove the efficiency and economy of their application inradioactive waste management. The selection of an appropriate ion exchange material for the liquid radioactive waste treatment is possible on the basis of information provided by themanufacturer. However since the selection of the appropriateion exchange material depends on the needs of the system, it isexpected that the data obtained from the actual experimental
trials will prove to be more helpful. Generally the selected ion
exchange materials must be compatible with the chemical
nature of the waste such as pH, type of ionic species present aswell as the operating parameters notably temperature. Also
while designing an ion exchange processing system it is desirable to have an adequate knowledge of the rate at which thereaction occur. From the reaction rate information it is possible
to decide the required contact time, which will further influence the physical size of the radioactive waste processing plant.
Although there are different alternative methods available toknow the reaction rate, but radioactive isotopic technique isexpected to be the most appropriate method as it offers several
advantages such as high detection sensitivity, capability of insitu detection, and physico-chemical compatibility with thematerial under study. Therefore in the present investigation
attempts were made to study the rate of bromide and iodide
ion-isotopic exchange reactions by application of radiotracer
technique using strongly basic anion exchange resin Duolite A113 under various operational parameters.
Research works on radiochemical applications,1 characteriza*Corresponding author. E-mail: pravinsingare@vsnl.net

tion of ion exchangers,2-4 their exchange properties in various
aqueous and organic medium,5-7 ion exchange equilibrium,8-17
and ion exchange reaction kinetics18-27 were performed extensively. However not much work was carried out to study thekinetics of ion-isotopic exchange reaction28-31 using these ionexchangers. In the present investigation attempts were made tostandardize the parameters affecting the ion-isotopic exchange
reaction kinetics by application of tracer technique. The resultsof the present investigation will be useful to set the operational
process parameters for the efficient industrial application ofthis ion exchanger. The same radioactive tracer technique canbe applied for the characterization of other industrial grade ion
exchange resins so as to decide about their selection for thespecific industrial application.
2. Experimental
2.1. Conditioning of ion exchange resin. Duolite A-113 assupplied by the manufacturer (Auchtel Products Ltd., Mumbai,India) is a strongly basic anion exchanger in chloride form having quaternary ammonium N + (CH 3) 3 functional group containing 8% styrene divinylbenzene of 20–50 mesh size. For
the present investigation the resins were converted into iodide
and bromide form by using 10% potassium iodide and 10%
potassium bromide solution respectively by adjusting the flowrate as 1 mL / min. The resins were then washed with double
distilled water, until the washings were free from iodide/bromide ions as tested by AgNO3 solution. These resins in bromide and iodide form were then dried separately over P2O5 indesiccators at room temperature.
2.2. Radioactive Tracer Isotopes. Details regarding theisotopes used in the present experimental work are given inTable 1.
TABLE 1: Properties of 131I and 82Br tracer isotopes (Ref. 32)
Isotopes Half-life

Radioactivity/ mCi

γenergy/ Me–V

Chemicalform

Physicalform

Iodide*Aqueous131I

8.04 d50.3682

Br36 h50.55

Bromide** Aqueous* Sodium iodide in dilute sodium sulphite.
** Ammonium bromide in dilute ammonium hydroxide.

© 2006 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 11/01/2006

LokhandeJ. Nucl. Radiochem. Sci., Vol. 7, No. 2, 2006

R-I + I*- (aq) →← R-I* + I (aq) .

Br131I

4.3

4.1

3.9

3.7
020

406080100

Time / minFigure 1. Kinetics of ion-isotopic exchange reactions using ion exchange
resin Duolite A-113. 1.000 g of ion exchange resins in bromide and iodide
form was equilibrated separately with 200 mL of 0.005 M (1 mmole)labeled bromide and iodide ion solutions respectively at a constant temperature of 26.0 ˚C for three hours. Activity of labeled iodide ion solution atcomplete equilibrium = 9120 cpm. Activity of labeled bromide ion solution at complete equilibrium = 6068 cpm.

(1)

Here R-I represents ion exchange resin in iodide form; I*- (aq)represents aqueous iodide ion solution labeled with 131I radiotracer isotope.
The activity of solution was measured at a fixed interval of
every 2.0 min. To know the activity exchanged at infinite time,
the activity was measured after three hours. The activity measured at various time intervals was corrected for backgroundcounts. Due to the rapid iodide ion-isotopic exchange reaction
taking place, the activity of solution decreases rapidly initiallyand then due to the slow exchange reaction the activity of thesolution decreases slowly and finally remains nearly constant.
Similar experiments were carried out with labeled iodide ion
solution of various concentration in the range of 0.005 M to
0.100 M in the temperature range of 26.0 ˚C to 43.0 ˚C keeping amount of ion exchange resin in iodide form 1.000 g constant. The experiment was also performed by using different
amount of ion exchange resin in iodide form in range of 1.000
g–5.000 g by using 0.005 M labeled iodide ion solution at aconstant temperature of 26.0 ˚C.
2.4. Study on kinetics of bromide ion-isotopic exchange
reaction. The experiment was performed in similar way as
explained above by using labeled bromide ion solution of different concentrations in the temperature range 26.0 ˚C to 43.0
˚C by using ion exchange resin in bromide form varying from1.000 g to 5.000 g. Labeling the bromide ion solution was doneby using dilute solution of radioactive 82Br tracer isotope in thesimilar manner as explained above. The bromide ion-isotopic
exchange reaction taking place can be represented as:
R-Br + Br*- (aq) →← R-Br* + Br (aq) .

82

Log of activity

2.3. Study on kinetics of iodide ion-isotopic exchange
reaction. In a stoppered bottle 200 mL of 0.005 M iodide ion
solution was labeled with diluted 131I radioactive solution using
a micro syringe, such that 1.0 mL of labeled solution has aradioactivity of around 15,000 cpm (counts per minute) whenmeasured with γ -ray spectrometer having NaI (Tl) scintillation
detector. Since only about 50–100 µL of the radioactive iodide
ion solution was required for labeling the iodide ion solution,
the iodide ion concentration will remain unchanged, which was
further confirmed by potentiometer titration against AgNO3solution. The above labeled iodide ion solution of known initial activity was kept in a thermostat adjusted to 26.0 ˚C. The
swelled and conditioned dry ion exchange resins in iodide form
weighing exactly 1.000 g were transferred quickly into thislabeled iodide ion solution which was vigorously stirred byusing mechanical stirrer and the activity in cpm of 1.0 mL ofsolution was measured. The activity in cpm so measured represents initial activity at zero time. The solution was transferred back to the same bottle containing labeled iodide ion
solution after measuring activity. The iodide ion-isotopic
exchange reaction can be represented as:(2)Here R-Br represents ion exchange resin in bromide form andBr*- (aq) represents aqueous bromide ion solution labeled with82
Br radiotracer isotope.
3. Results and Discussion
In the present investigation, it was observed that due to therapid ion-isotopic exchange reactions the activity of solution
goes on decreasing sharply with time and then further theactivity remains nearly constant due to slow exchange reaction.
Preliminary studies33, 34 shows that reaction was of first order.
Therefore logarithm of activity was plotted against time. This
gives a composite curve in which the activity initially decreases
sharply and thereafter very slowly (Figure 1), evidently rapid82

Log of activity after resolution

30Br

131

I

4
3.8
3.6
3.4
3.2
02

46810Time / minFigure 2. Variation of log activity after resolution with time for ionisotopic exchange reactions using ion exchange resin Duolite A-113.
See footnote of Figure 1.

and slow ion-isotopic exchange reactions were occurring simultaneously. The specific reaction rates for the rapid exchange
reaction were obtained by resolving the composite curve in amanner similar to the determination of decay constants ofradioactive isotopes in a mixture. The rapid ion-isotopic
exchange reaction undergo completion in a short interval oftime of about 15 to 20 min, however slow ion-isotopic
exchange reaction continues over a much longer interval oftime and the exchange reaction is assumed to reach the complete equilibrium after three hours. Hence the activity measured after three hours represents the activity of solution atcomplete equilibrium. At this later stage as the slow exchange
process was the only reaction taking place, the log of activity
due to slow process against time curve gives a straight line.
Now the straight line was extrapolated back to zero time. The
extrapolated portion represents the contribution of slow process
to the total activity which now includes rapid process also. The
activity due to slow process was subtracted from the total activity at various time intervals. The difference gives the activity
due to rapid process only. The log of this activity after resolution was plotted against time which gives a straight line withnegative slope (Figure 2). From the slope of this line the specific reaction rates (k) of rapid ion-isotopic exchange reaction
were calculated. The amount of ions (Br- /I- ) exchanged inmmol on the resin were obtained from the initial and final
activity of solution and the amount of exchangeable ions in 200
mL of solution. From the amount of ions exchanged on theresin in mmol and the specific reaction rates (min-1), the initial

Comparative Study on Bromide and Iodide Ion-Isotopic Exchange

J. Nucl. Radiochem. Sci., Vol. 7, No. 2, 2006

31

TABLE 2: Effect of concentration on ion-isotopic exchange reactions using ion exchange resin Duolite A-113
Concentration ofexternal labeledionic solution(M)Amount of ionsin 200 mL ionicsolution (mmol)

0.005

1.0

R-Br + Br*- (aq) →← R-Br* + Br (aq)R-I + I*- (aq) →← R-I* + I* (aq)Specificreaction rate(min-1)

Amount ofbromide ionsexchanged(mmol)

Initial rate ofbromide ion
exchange(mmol/min)Specific
reaction rate(min-1)

Amount ofiodide ionsexchanged(mmol)

Initial rate ofiodide ion
exchange(mmol/min)

0.177

0.743

0.132

0.112

0.528

0.059

0.010

2.0

0.175

1.210

0.212

0.110

0.762

0.084

0.020

4.0

0.173

2.347

0.406

0.113

1.550

0.175

0.100

20.0

0.180

10.68

1.923

0.111

5.117

0.568

1.000 g of ion exchange resins in bromide and iodide form was equilibrated separately with 200 mL of labeled bromide and iodide ion solution
respectively of different concentrations at a constant temperature of 26.0 ˚C for three hours.

TABLE 3: Effect of amount of ion exchange resin on ion-isotopic exchange reactions using ion exchange resin Duolite A-113
R-Br + Br*- (aq) →← R-Br* + Br (aq)Amount of ionexchange resin(g)Specific reaction
rate(min-1)

Amount ofbromide ionsexchanged(mmol)

R-I + I*- (aq) →← R-I* + I (aq)Initial rate ofbromide ionexchange(mmol/min)Specific reaction Amount of iodide Initial rate of iodide
rateions exchangedion exchange(min-1)(mmol)(mmol/min)10.177

0.743

0.132

0.112

0.528

0.059

2

0.197

0.696

0.137

0.161

0.538

0.086

30.216

0.754

0.162

0.204

0.557

0.113

4

0.265

0.764

0.202

0.221

0.578

0.127

5

0.293

0.786

0.230

0.253

0.583

0.147

Different amount of ion exchange resins in bromide and iodide form was equilibrated separately with 200 mL of 0.005 M (1 mmol) labeled bromide andiodide ion solution respectively at a constant temperature of 26.0 ˚C for three hours.

TABLE 4: Effect of temperature on ion-isotopic exchange reactions using ion exchange resin Duolite A-113
R-Br + Br*- (aq) →← R-Br* + Br (aq)Temperature
˚C

26.0

R-I + I*- (aq) →← R-I* + I (aq)Specific
reaction rate(min-1)

Amount ofbromide ionsexchanged(mmol)

Initial rate ofbromide ion
exchange(mmol/min)Specific
reaction rate(min-1)

Amount of iodide
ions exchanged(mmol)

Initial rate ofiodide ion
exchange(mmol/min)

0.177

0.743

0.132

0.112

0.528

0.059

32.0

0.187

0.756

0.141

0.136

0.640

0.087

43.0

0.203

0.9400.191

0.168

0.828

0.139

1.000 g of ion exchange resins in bromide and iodide form was equilibrated separately with 200 mL of 0.005 M (1 mmol) labeled bromide andiodide ion solutions respectively at various temperatures for three hours.

82

Br

131

I

12

Amount of ionsexchanged (mmol)

rate of (Br- /I-) ion exchanged in mmol/min was calculated.
Because of smaller ionic size of bromide ions as comparedto that of iodide ions, it was observed that the exchange of bromide ions occurs at the faster rate than that of iodide ions.
Hence under identical experimental conditions, the specificreaction rate /min-1, amount of ion exchanged in mmol and initial rate of ion exchange in mmol/min are calculated to behigher for bromide ion-isotopic exchange reaction than that ofiodide ion-isotopic exchange reaction as summarized in Tables
2–4. For both bromide and iodide ion-isotopic exchange reaction under identical experimental conditions of temperature
26.0 ˚C, amount of ion exchange resin 1.000 g, the values ofspecific reaction rate remains nearly constant even though theconcentration of external exchangeable ionic solution was varied twenty times i.e. from 0.005 M to 0.100 M as shown inTable 2. However when the concentration of ionic solution was10864200.005

0.01

0.02

0.1

Concentration of labeled ionic solution / M

Figure 3. Effect of concentration on ion-isotopic exchange reactions
using ion exchange resin Duolite A-113. See footnote of Table 2.

32

Lokhande

J. Nucl. Radiochem. Sci., Vol. 7, No. 2, 2006
82

131

Br82

I
Amount of ionsexchanged (mmol)

Amount of ionsexchanged (mmol)

I110.80.6
0.4
0.20131Br12345

Amount of ion exchange resin / g0.80.60.40.20263243Temperature / ˚CFigure 4. Effect of amount of ion exchange resin on ion-isotopicexchange reactions using ion exchange resin Duolite A-113. See footnote of Table 3.

Figure 5. Effect of temperature on ion-isotopic exchange reactions
using ion exchange resin Duolite A-113. See footnote of Table 4.

kept constant 0.005 M, the specific reaction rate increases
sharply with rise in temperature from 26.0 ˚C to 43.0 ˚C asshown in Table 4. For 1.0 mmol of bromide ions in solution,
the amount of bromide ions exchanged increases from 0.743
mmol at 26.0 ˚C to 0.940 mmol at 43.0 ˚C; while under thesame experimental conditions the amount of iodide ionsexchanged increases from 0.528 mmol to 0.828 mmol as shownin Table 4. From the results, it appears that bromide ionsexchange at the faster rate as compared to that of iodide ions asshown in Figures 3–5 which was related to their ionic size.

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