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Chemcon 2013 66 th Annual Session of Indian Institute of Chemical Engineers
Hosted at Institute of Chemical Technology, Mumbai 400 019
Electrodeionization of Cesium from AMP-PAN
Conference Paper · December 2013
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Chemcon 2013
th
66 Annual Session of Indian Institute of Chemical Engineers
Hosted at Institute of Chemical Technology, Mumbai 400 019
27-30 December 2013
Electrodeionization of Cesium from AMP-PAN
Ch.Mahendra1, P.M.Satyasai2, C.Anand babu3, K.Revathy1, K.K.Rajan1
1
Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu
2
Waste Immobilisation Plant, Bhaba Atomic Research Centre Facilities, Kalpakkam, Tamilnadu
3
PSG college of Technology, Coimbatore, Tamilnadu
E-mail addresses: mahendra.ch6@gmail.com, pmssai@igcar.gov.in, canandbabu@gmail.com, krevathy@igcar.gov.in,
kkrajan@igcar.gov.in
Abstract: Electrodeionization of Ammonium Molydo Phosphate-Poly Acrylo Nitrile (AMP-PAN) loaded with cesium ions has
been done in Electrodialysis setup consisting of three compartments. Deionization of AMP-PAN resin was done using
ammonium sulphate as regenerative solution. The effect of current density and concentration of regenerative solution on the
recovery of cesium form AMP-PAN was studied.
Keywords: AMP-PAN, cesium, elecrodeionizaiton, currentdensiy
investigations is an assessment of the influence of the
current density and concentration of regenerative solution
on recovery of cesium from AMP-PAN in electro dialysis
setup.
1. Introduction:
Waste management is one of the challenges that Indian
Nuclear power program needs to address effectively due to
the radio toxicity and longevity of the radio nuclides
present in the waste. Cesium is one of the principal fission
products of U 235 and Pu 239 with a half life of around
30y. Removal of Cs from the waste would not only
decrease the radioactivity level of the waste significantly,
but make the Cs available for many useful applications.
Many methods have been proposed for separation of Cs
from the aqueous waste of which Ion exchange showed
promising results. Among cesium selective inorganic
sorbents, Ammonium Molydo Phosphate (AMP)-Poly
Acrylo Nitrile (PAN) showed a good uptake of Cs from
acidic high level waste [1]. Owing to the industrial and
medical applications of Cs, extraction of Cs in pure form is
desired for its reuse. Regeneration of the AMP-PAN could
be done with saturated ammonium salts but the separation
of Cs from high concentrated ammonium salts is difficult.
2. Material and Methods:
All the chemicals used in the experiments were
analytical grade. The properties of AMP-PAN used in
study were presented in Table.1. The solutions
ammonium and cesium were prepared through
dissolution of (NH4)2SO4 and CsCl respectively,
deionized water and 4N HNO3.
of
the
of
the
in
Table 1: Properties of AMP-PAN
Electrodeionisation is a developing technique, which is
currently under study for recovery of metals from dilute
solutions [2,3,4]. In our previous work, Electro Dialysis Ion
Exchange (EDIX) was studied for recovery of Cs from the
AMP-PAN (loaded with Cs) by passing low concentrations
of ammonium solution through anode compartment [5]. In
the present study, ammonium solution for regeneration of
AMP-PAN is passed directly through the middle
compartment containing the resin already loaded with
cesium ions. The objective of the experimental
Trade name
AMP-PAN
Nature
cationic
Particle size
0.4-.0.5mm
pore diameter
Macro porous
Bulk density
1.5 g/m³
AMP loaded on resin
65%
Moisture content
55%
Experimental setup
The cell used in this study was composed of three
compartments separated by ion-exchange membranes; a
schematic is presented in Fig. 1. Platinum coated titanium
electrodes were used as anode and cathode. The central
1
Chemcon 2013
th
66 Annual Session of Indian Institute of Chemical Engineers
Hosted at Institute of Chemical Technology, Mumbai 400 019
27-30 December 2013
compartment containing the resin loaded with cesium is
separated from anode and cathode compartments by
anionic and cationic membranes respectively. Before filling
the central compartment with 20g of AMP-PAN, it was
loaded with Cs in column by passing 750ppm Cs in 4N
HNO3 through the column. The capacity of the resin was
found to be 32 mg of Cs/ g of resin at 5ml/min flow rate of
the feed solution. The central compartment was 5mm in
thickness and the anode and cathode compartments were
8mm in thickness. All the three compartments were made
of perpex glass sheet. 10000ppm NH4+ regenerative
solution is passed through the middle compartment at
5ml/min once through while in the anode and cathode
compartments, 0.1N HNO3 and 1N HNO3 solutions were
circulated at 200 ml/min using peristaltic pumps. The cell
was operated for 10 hours at different current densities and
different concentrations of the regenerative solution.
Samples were collected from all the compartments at
regular intervals of time and analysed for cesium
concentration.
At Anode:
2H2O → O2 + 4H+ + 4eMiddle compartment: Ion Exchange Resin:
R-Cs+ + NH4+
4H2O + 4eCs+
NH4OH
3. Results and Discussion
3.1Effect of current density
The recovery of cesium from AMP-PAN loaded with
cesium was determined at different current densities
ranging from 20 mA/cm2 to 60mA/cm2. The percentage of
cesium recovered with time from the middle and cathode
compartments was shown in Fig.2 and Fig.3 and total
cesium recovered from all the compartments at different
current densities was shown in Fig.4.
Cs
NH4
CsOH
-
NH4 + OH
Cathode
SO4-
→ 2H2 + 4OH-
+ OH+
-
Anode
R-NH4+ +Cs+
At Cathode:
% Cs recovered in cahtolyte
+
Reactions in different compartments
+
35
30
25
20 mA/cm²
20
30 mA/cm²
15
40 mA/cm²
10
60 mA/cm²
5
0
0
3
6
9
12
Time, h
AEM
0.1N HNO3
CEM
(NH4)2SO4
Figure 2: Cs recovery in cathode compartment at
different current densities
In the middle compartment, the regenerative solution
containing the NH4+ replaces the cesium ions on the AMPPAN resin when it comes in contact with the resin. Some
part of the eluted cesium from the resin migrates towards
the cathode compartment under the applied current and the
other part goes in the middle compartment outlet solution
as the regenerative solution is flowing once through. From
Fig.2 it was observed that cesium recovery in cathode
compartment is increasing with increasing the current
density. It may be explained by the fact that with increasing
1N HNO3
Figure 1: Schematic of Experimental setup
AEM - Anion Exchange Membrane
CEM - Cation Exchange Membrane
2
Chemcon 2013
th
66 Annual Session of Indian Institute of Chemical Engineers
Hosted at Institute of Chemical Technology, Mumbai 400 019
27-30 December 2013
The middle compartment is separated from the anode
compartment with anion exchange membrane which
restricts the diffusion of cations towards anode, negligible
amounts of cesium were found in the anode compartment.
With increasing current density, water splitting enhanced at
the bipolar interface of the cationic exchange resin and the
anion ion exchange membrane which resulted in H+ and
OH- formation.
60
50
40
30
20 mA/cm²
30 mA/cm²
40 mA/cm²
60 mA/cm²
20
10
20mA/cm²
30mA/cm²
40mA/cm²
60mA/cm²
12
Voltage drop/ volts
% Cs recovered in middle
compartment
current density more number of ions can migrate in unit
time per unit area. In the initial hours, the elution in the
middle compartment outlet and migration towards cathode
compartment was high when compared to later hours. From
Fig.3 it was observed that the total cesium eluted from the
outlet of middle compartment was decreasing with
increasing the current density. Increase in migration rate at
higher current densities had decreased the availability of
cesium ions to elute from the outlet of the middle
compartment.
10
8
6
4
2
0
0
2
4
6
Time/h
0
0
2
4
6
8
Time/ h
10
12
65.07
59.82
% Cathode
58.21
47
38.41
13.04
20
Conductivity/ mScm¯¹
61.41
50.08
18.07
21.41
30
40
Current densiy, mA/cm²
12
The uptake of protons by the resin might have prevented
the cesium to diffuse from deeper sites of the resin to the
surface of the resin which resulted in decrease in total
recovery at higher current densities. This is also evident
from the voltage drop across the cell as shown in Fig.5
where at higher current densities voltage was decreasing
with time. The uptake of protons by the resin increased its
conductivity and hence resulted in sharp voltage decrease
at higher current densities. At lower current densities
(20mA/cm2) where water splitting at the bipolar interface is
less pronounced, the voltage drop was almost constant.
The total amount of cesium recovered from all the
compartments is shown in Fig.4. With increasing current
density from 20mA/cm2 to 30mA/cm2 the total recovery of
cesium increased from 61.41% to 64.07% and further
increase in current density form 40 to 60 mA/cm2 resulted
in decrease of recovery.
% Middle
10
Fig.5. Variation of voltage drop at different current
densities
Fig.3.Cs recovered in middle compartment at different
current densities
% Total recovered
8
32.49
26.72
60
Fig.4. Total percentage of cesium recovered from all
compartments
60
50
40
30
20
10
0
M-20mA/cm²
M-30mA/cm²
M-40mA/cm²
M-60mA/cm²
0
2
4
6
Time/h
8
10
12
Fig.6. Variation of conductivity of middle compartment
eluent with time for different current densities
3
Chemcon 2013
th
66 Annual Session of Indian Institute of Chemical Engineers
Hosted at Institute of Chemical Technology, Mumbai 400 019
27-30 December 2013
Fig.6 shows the eluent conductivity at the outlet of the
middle compartment when the regenerative solution passes
once through the resin. At the outlet, the eluent
conductivity is almost constant with time but decreased
with increase in current density.
3.2 Effect of regenerative solution concentration
% Cs recovered in
catholyte
25
Conductivity/ mScm¯¹
C-20mA/cm²
450
400
350
300
250
200
150
100
50
0
C-30mA/cm²
C-40mA/cm²
C-60mA/cm²
15
10
5
% C-100000 ppm
% C-25000 ppm
0
0
0
2
4
6
8
10
Fig.7. Variation of conductivity of catholyte with time for
different current densities
150
% Cs eluted from middle
compartment
A-20mA/cm²
A-30mA/cm²
A-40mA/cm²
A-60mA/cm²
200
100
50
0
0
2
4
6
Time/h
8
10
4
6
8
Time/h
10
12
The effect of regenerative solution concentration was
found by passing 10000ppm and 25000ppm of NH4+
through the middle compartment containing the AMP-PAN
resin loaded with cesium at 40mA/cm2 current density.
When a high concentration of regenerative solution was
passed through an ion exchange resin, more ions were
available for exchange and hence fast kinetics could be
observed. From the Fig.9 it was observed that the migration
of cesium ions towards cathode decreased with increasing
the regenerative solution concentration from 10000ppm to
25000ppm. Whereas the cesium eluted in the middle
compartment outlet increased with increase in the
regenerative solution concentration as shown in Fig.10.
The variation of conductivities of catholyte and anolyte
with time for different current densities is shown in Fig.7
and Fig.8 respectively. The hydroxide generation at the
cathode and proton generation at the anode as mentioned in
the reactions at the respective electrodes might have
contributed for the decrease in the catholyte conductivity
and increase in the anolyte conductivity. With increasing
the current densities the reaction rates at the electrodes
were also increased.
250
2
Fig.9.Cs recovered in cathode compartment for
different regenerative solution concentration at
40mA/cm²
12
Time/h
Conductivity / mScm¯ ¹
20
12
80
70
60
50
40
30
20
10
0
% M-10000 ppm
% M-25000 ppm
0
Fig.8. Variation of conductivity of anolyte with time for
different current densities
2
4
6
Time/h
8
10
12
Fig.10.Cs eluted from middle compartment for
different regenerative solution concentration at
40mA/cm²
4
Chemcon 2013
th
66 Annual Session of Indian Institute of Chemical Engineers
Hosted at Institute of Chemical Technology, Mumbai 400 019
27-30 December 2013
increasing the regenerative solution concentration recovery
of cesium has been increased but most of the cesium was
recovered through elution from the middle compartment.
As observed from Fig.10, around 40% of the cesium loaded
on the AMP-PAN resin eluted through the middle
compartment in the first one hour for 25000 ppm
regenerative solution whereas only 20% of the loaded
cesium eluted for 10000 ppm regenerative solution. From
Fig.9 it was seen that for both 10000 ppm and 25000 ppm
regenerative solutions almost same amount of cesium was
migrated to cathode compartment in the first one hour.
When 25000 ppm solution was passed, most of the
available cesium for exchange was eluted from the resin
but out of the total eluted only a few percent migrated to
cathode compartment in the first one hour. As migration of
ions depends on the available membrane area and applied
current, only a few percent has migrated out of the total
eluted from the resin in the initial hours. After 6h of
operation, the total Cs recovery from all the compartments
was very low and complete recovery requires longer time
operations which would not be economical.
% Total
%M
[1] T. J. Tranter, R. S. Herbst, T .A .Todd, A. L. Olson, H.
B. Eldredge, Evaluation of ammoniumolybdo
phosphate-polyacrylonitrile (AMP–PAN) as a cesium
selective sorbent for the removal of 137Cs from acidic
nuclear waste solutions. Adv. Environ. Res., 6, 2002,
107-121.
[2] A. Smara, R. Delimi,E. Chainet, J. Sandeaux, Removal
of heavy metals from diluted mixtures by a hybrid ion
exchange / electro dialysis process. Sep.Purif.Technol.,
57(1), 2007, 103-110.
[3] S. Ezzahar, A. T. Cherif, J. Sandeaux, R. Sandeaux, C.
Gavach, Continuous electro permutation with ion
exchange textiles. Desalination.,104, 1996, 227-233
[4] H. Strathmann, K. Kock, Effluent free regeneration of
%C
77.58
59.824
References
a Pb-charged ion exchange resin by electro dialysis.
Polym.Prepr.Am.Chem.Soc.Div.Polym.Chem., 21,
1980, 105-106.
67.1
38.41
[5] Ch. Mahendra, Suranjan Bera, C. Anand babu, K. K.
21.41
10000 ppm
Rajan, Separation of cesium by Electrodialysis Ion
exchange using AMP-PAN. Sep.Sci.Technol., 48,
2013, 2473-2478.
10.26
25000 ppm
Rengenerative solution Conc.
Fig.11. Total Cs recovered from all compartments for
different regenerative solution concentration at
40mA/cm²
Fig.11 shows the percentage of cesium recovered from
cathode and middle compartments for different
regenerative solutions. It was observed that with increasing
the regenerative solution concentration from 10000 ppm to
25000 ppm, cesium recovery increased from 59.82 % to
77.58%. Most of the cesium recovered at higher
concentration was because of elution rather than migration.
4. Conclusion
Electrodeionization of cesium from AMP-PAN increased
with increase in current density from 20mA/cm2 to
30mA/cm2 and further increase resulted in decrease of
deionization. The deionization of cesium from the resin
occurred in the form of migration to cathode compartment
and elution from middle compartment as in columns. With
5
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