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Land Decontamination in South Tangerang and
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Management of Contaminated Soil Waste
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A R T I C L E I N F O A B S T R A C T 12
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AIJ use only:
Received date Revised date Accepted date Keywords:
Contaminated soil
137Cs
Decontamination
Management of contaminated soil Treatments
...
Recently it was found the contamination of 137Cs that was on an empty land in an area at South Tangerang, for that reason the area which was contaminated with
137Cs needs to be cleaned up by doing the decontamination works at that place.
Then continue with the activity of managing contaminated soil. The decontamination works were carried out by peeling the contaminated soil, and then put it into a 100L drum. The drums contained contaminated soil send to the interim storage facility for further treatment. To resolve the case of 137Cs contamination on the soil, it is necessary to study the decontamination and management of contaminated soils. Some techniques and strategies for decontamination and managing 137Cs contaminated in the soil are presented in this paper. Further evaluation needs to be done so that the results of the study could be used appropriately to treat the contaminated soil waste from the land in South Tangerang.
© 2020 Atom Indonesia. All rights reserved
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INTRODUCTION∗
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In middle of February 2020, Indonesia was
17
shocked by the founding of 137Cs radioactive
18
contamination on an empty land in the South
19
Tangerang by Bapeten (nuclear energy regulatory
20
body in Indonesia), and then the news in Indonesia
21
(newspaper and online news) was filled with this
22
sensational news [1-5]. Radioactive contamination
23
has been found on an empty land close to the
24
resident home in South Tangerang. The location of
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the event is shown in Figure 1. The higher activity
26
compared to the surrounding environment causes
27
the regulatory body to pay attention and
28
coordination with National Nuclear Energy Agency
29
(BATAN) to carry out a mitigation plan of the land
30
to perform the decontamination activity. The
31
contamination needs to be handled well, carefully
32
and safely so as not to cause panic in the
33
community, and more importantly that the activity is
34
able to minimize the subsequent impacts such as the
35
possibility of further spreading of radioactive
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∗ Corresponding author.
E-mail address:
contaminants into around the location. The
37
decontamination activities started under the
38
supervision of BATAN to decontaminate soils.
39
40
Figure 1. Map of location of radioactive contamination 41
has been found 42
43
Before conducting the studies of
44
decontamination and management of contaminated
45
soil by 137Cs, the nature of 137Cs needs to be
46
understood first. Radiocesium-137 has a high
47
solubility properties in solution and has long half-
48
life (about 30 y). When the 137Cs reach the
49
groundwater, it can cause as primary causes of
50 Atom Indonesia
water contamination to the residents at the
51
surrounding location due to easy associated with
52
plants and species exist in terrestrial and water
53
environment [6]. However the 137Cs is not very
54
mobile in the environment, it tends to accumulate
55
and bind strongly on the most surface of soil hence
56
absorb more localized. Consequently, 137Cs is
57
difficult for uptake by vegetation through roots [7].
58
Since the behavior of Cs+ ion is very similarly to
59
Na+ and K+ ions, thus facilitating its digestion and
60
assimilation in living organisms [8]. If the human
61
body is possessed by 137Cs substance, cells in the
62
body could become damaged due to the radiation
63
that might penetrate the entire body, and then it is
64
deposited in the soft tissues such as muscle and
65
nerve cell, and might also cause cancer [9]. To
66
protect the public health and worker, Bapeten issues
67
the regulations on Radiation Protection and Safety
68
in the Utilization of Nuclear Energy, where the
69
average effective dose limit for radiation workers is
70
set at 20mSv / year, while for the general public is
71
set at 1 mSv / year [10].
72
73
The circumstances in which the problem of
74
radioactive contamination (137Cs) occurred in South
75
Tangerang have a different character from the event
76
of nuclear accidents in Fukushima and Chernobyl.
77
In the events of Fukushima and Chernobyl
78
accidents, the contamination that occurs in the
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surface soil due to the release of 137Cs from the
80
accident went to the atmosphere which makes it the
81
most abundant radioactive atmospheric pollutant
82
capable of taking health hazards. The 137Cs will then
83
return down to earth as a 137Cs fallout and settle on
84
the soil surface to a large extent as 137Cs
85
contaminants. Most of the contaminants have fallen
86
to the surface of the soil, so soil decontamination
87
activities in Fukushima and Chernobyl were carried
88
out by peeling the surface soil to a depth of about 5-
89
15 cm [12,13]. This activity was intended to clean
90
up the area from contaminants. While the 137Cs
91
contamination in South Tangerang was different.
92
Here the contamination came from 137Cs source
93
contaminated the surface and also in the sub-surface
94
of soil, so that the decontamination method that
95
must be carried out also has a slight difference in
96
treatment. To do the decontamination activity in
97
South Tangerang, an approach with the MARSSIM
98
manual can help decontamination activities [14].
99
The soil from the result of soil removal were put
100
into 100L drums. From the activity of
101
decontamination in South Tangerang, some
102
hundreds of drums containing 137Cs contaminated
103
soil were produced and sent them to an interim
104
storage (IS) facility to be stored safely before further
105
processing.
106
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The technique of removal of 137Cs radioactive
108
from soil is a necessity and important, therefore the
109
results of the study are expected to find appropriate
110
technologies for the further use. For this reason, an
111
initiative the study of decontamination of 137Cs
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contamination into soil and the manage volume of
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waste generated from decontamination work will be
114
discussed in the paper. Information obtained from
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the activities of decontamination and management
116
of the wastes, such as procedures, methods,
117
decontamination techniques and management of
118
137Cs contaminated soil (also how to remove and
119
treat the 137Cs from soil) will be explained briefly, as
120
well as some techniques and strategies for
121
approaching the treatment of contaminated soils.
122
Further evaluation needs to be done might the
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results of the study could be considered
124
appropriately for the stakeholders to manage the
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contaminated soil waste of the land in South
126
Tangerang.
127 128 ∗
METHODOLOGY
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To conduct this study, the existing primary and
131
secondary data and the informations are relevant to
132
the decontamination of 137Cs contaminated soil and
133
its subsequent processing have been used. An
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approach using the MARSSIM manual can assist in
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the preparation of the initial survey activity
136
procedures, as well as the results to be obtained
137
from land decontamination activities. Then to learn
138
the techniques of accumulating the 137Cs
139
concentration of contaminated soils used study
140
material of management of contaminated soils
141
which was obtained from a compilation work to
142
similar activities in many places that have been
143
published. From here, the reviewed decontamination
144
techniques are then evaluated to obtain the suitable
145
treatment methods that can be considered for use in
146
the plan for processing of contaminated land waste
147
in further. In the end of the paper, some method to
148
reduce the volume of the contaminated soil wastes
149
are considered to be proposed to the management.
150
151
RESULTS AND DISCUSSION
152 153
In the case of environmental contamination
154
with radioactive material, the mitigation approach
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can use the guidance of MARSSIM manual, where
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the survey of area classification in the site
157
investigation process for conducting the radiation
158
survey is shown in Figure 2 [14].
159 160
The survey process was carried out in a
161
walkover survey method, where the output from this
162
activity was the data about type and level of
163
radiological from the contaminants. The results of
164
the survey can also be used to classify
165
contamination areas, work paths of workers in
166
decontamination activities and to recommend the
167
activities and tools, as well as analytical methods to
168
be used in the decontamination activities.
169 170 171
172
Figure 2. Survey classification process of MARSSIM manual 173
[14].
174 175
From the results of walkover surveys that
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have been carried out, it has been obtained such as
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the type and level of radiology of the area of
178
contaminated soil. The type of radionuclide was
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137Cs which is allegedly come from radioactive
180
sources which spread out over the area. There are
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some hotspots were found at that location, and the
182
dose exposure in these area is about 149 µSv/hour
183
[15]. The hotspot is then got pay attention to be
184
chosen as the center or target of the decontamination
185
activity plan.
186
187
The results of the analysis of coring activities
188
shown as slightly strange result if the results are
189
intended as radiologic contamination at the surface
190
of the soil. At the location, high activity has been
191
obtained at the ground surface in one point, but at
192
another point there is a high activity in certain
193
depths in the soil was obtained. This showed that
194
contamination occurred at the location with 137Cs
195
radioactive material is an intentional action, and this
196
behavior can be suspected of an attempt to hide
197
radioactive material in the area by an irresponsible
198
person.
199
200
The decontamination activity is carried out,
201
firstly by peeling off the soil layer that has been
202
contaminated by 137Cs. The results obtained from
203
this activity, contaminants can be removed from the
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incident area and a significant reduction in activity
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concentration in the contaminated area occurred
206
(from 149 to 0.3-0.75 µSv/hour) [16]. The drums
207
contained contaminated soil and then successfully
208
transported to the interim storage facilities at
209
Serpong Nuclear Center.
210
211
The results of peeled soil surface were then
212
put into a 100L drums and the investigation of the
213
distribution of intrusions of 137Cs into sub-soil layer
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will be identified by coring works in the area of
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contaminated soil as shown in Figure 3. Some
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hundred quantity of drum is obtained, after which
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the drums are brought to the interim storage facility
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in BATAN for further treatment, Figure 4.
219
220
221
Figure 3. Activities of decontamination and investigation in the 222
land area: (a) soil peeling and (b) coring of soil layer 223
224
a
b
225
Figure 4. Radiation workers with drums resulting from the 226
surface soil decontamination activities 227
228
The next step after decontamination activity is
229
management plan of the contaminated soil with the
230
treatment works of contaminated soil to reduce the
231
quantity of waste volume that has accumulated in
232
the interim storage facility. If this step is successful,
233
the result can reduce the amount of contaminated
234
soil waste, and also it will reduce the use of drums
235
contained contaminated soil, so that the capacity of
236
interim storage facilities would be increased.
237 238
The strategy to reduce the volume of
239
contaminated soils can be shown in Figure 6.
240
Drums which contain the contaminated soil are
241
separated, the drums which have levels of below the
242
allowable activity concentration and with the drums
243
that have a higher activity concentration.
244
245
Figure 6. Strategy to reduce volume of contaminated soil from 246
decontamination results 247
248
If drums with a low activity concentration is found,
249
then the contaminated soil can be removed from the
250
drum and placed in a location that does not need to
251
be controlled anymore or can be released into the
252
environment after got the approval from Bapeten.
253
Whereas for the drums that are still classified as
254
having a high activity concentration, the soil
255
"needs" to be sorted out again. The soil that have a
256
low activity concentration level can be included in
257
the soil that can be cleared or release them into
258
environment. While parts of the soil which has
259
contain a high concentration activity of 137Cs will be
260
extracted with a chemical agent. The volume
261
reduction method of this works is an ex-situ method,
262
will do at the facility of interim storage.
263
264
Soils which are still high in concentration
265
activity will be further processed. Furthermore,
266
some processing techniques by removing 137Cs from
267
the soil will be studied. Efforts to extract 137Cs from
268
the contaminated soil are carried out by leaching
269
137Cs from the soil sample. Radiocesium would
270
strongly bound to the soil due to the existence of
271
mineral flakes in the contaminated soil structure
272
[17,18]. The presence of minerals in the soil
273
composition could bind the 137Cs firmly [19-22] so
274
an effort to desorption 137Cs from the minerals is
275
needed. Removal of 137Cs from contaminated soils
276
can be done through wet and/or dry processes,
277
where each of the processes has the advantages and
278
disadvantages. But the main thing from this activity
279
is that the principle of radioactive waste treatment
280
must not be ignored, that is the reduction volume of
281
treated waste.
282 283
Since 137Cs is the primary cause of soil
284
contamination in a land at South Tangerang, and
285
recent the contaminated soil is storing at the facility
286
of interim storage, 137Cs radioactive management
287
has now become a priority. As the previous
288
mention that decontamination of 137Cs contaminated
289
soils can be done through wet and/or dry processes.
290
In the next paragraph a brief discussion of some
291
processes that possible to be carried out to manage
292
contaminated soil wastes. In some of the literature,
293
the first stage to manage contaminated soil waste is
294
an attempt to remove 137Cs from the contaminated
295
soil [23-25]. Several methods have been carried out
296
using leaching solutions to remove 137Cs from
297
contaminated soil. And then the solution from the
298
results of the radioactive leaching is processed with
299
a variety of absorbent materials, both derived from
300
natural materials, organic or modified materials, or
301
can also be done by using other methods.
302
303
In fact, the most effective method to reduce
304
the negative effects of radiation in contaminated soil
305
is by removing 137Cs from the contaminated soil.
306
With regard to the easy operation and volume
307
reduction processes for the radioactively
308
contaminated soil, the extraction process might
309
become an effective strategy for treatment of
310
contaminated soil from the decontamination results.
311
312
Shibata et.al. [26] conducted a study on 137Cs
313
decontamination by flushing with water to the
314
simulation of 137Cs contaminated soil. The results
315
show that only about 7% of 137Cs are extracted by
316
water and the remaining 90% of 137Cs is still
317
strongly bound in soil samples. Then based on
318
particle size, a sieving equipment was used to sort
319
the contaminated soil. The results showed that most
320
of the 137Cs had accumulated in soil samples with
321
particle size of about 425 μm, which was the
322
particle size of minerals in the soil (vermiculite). It
323
is predicted that 137Cs are absorbed at the frayed
324
edge of vermiculite. The extraction ratio will
325
increase along with a longer processing period.
326
Yanaga and Parajuli [21,24], conducted an
327
extracting 137Cs from solution by contacting
328
artificially contaminated soil with KI solution, and
329
as a comparison they also carried out soil washing
330
with demineralized water. The results show that the
331
process of removing of 137Cs from contaminated soil
332
will increase along with the increase in the
333
concentration of KI was given into the solution.
334
Increasing the processing time does not increase the
335
extracted 137Cs. It is supposed due to the movement
336
of 137Cs in the soil into the mineral site, so that the
337
bond that occurs between 137Cs with minerals
338
becomes stronger. Whereas the extraction with
339
water only gives a little 137Cs which are released
340
into the solution as shown in Figure 7.
341
342
Figure 7. Variation of extraction time versus 137Cs removal 343
from solution [21]
344 345
Hirose [23] extracted 137Cs from
346
contaminated soil using Milli-Q water, Ammonium
347
acetate and acetic acid solutions. The results of
348
overall extracted fractions of 137Cs using the three-
349
step sequential extraction process could only
350
produce less than 30% of 137Cs that were removed
351
from solution. There is an interesting study
352
conducted by Kim et.al [27] to develop a system to
353
washing the contaminated soil. To remove 137Cs
354
from contaminated soil they use many chemical
355
agents, such as H2O, citric acid, citric acid+HNO3,
356
NH4NO3, FeCl3, (COOK)2⋅H2O, (NH4)2SO4,
357
H2C2O4⋅H2O, NaOH, and Na3PO4 solutions. The
358
obtained results showed that the H2C2O4⋅H2O
359
chemical agent has provided the highest efficiency
360
value for removal 137Cs from the solution, where the
361
efficiency was almost to 50%. Oxalic acid will
362
form a stable metal-complex with 137Cs, and
363
dissolves hydroxides. Besides that the H2C2O4⋅H2O
364
also reasonable in price, so H2C2O4⋅H2O is an
365
optimal chemical agent for washing the soil. The
366
contaminated soils that has been extracted 137Cs then
367
can be classified as soil having low radioactive
368
content. But if the soil still has a high radioactive
369
activities, then the soil will be treated with another
370
method, such dry method to avoid increasing a
371
secondary wastes. The previous mention are some
372
methods for removing 137Cs from contaminated soil.
373
The 137Cs extracted solution is then processed in
374
several of ways which can make the activity in the
375
solution reduced.
376 377
To reduce the Cs-137 concentration on the
378
treated water using some methods such as
379
adsorption/ion exchange, electrochemical, and
380
biomaterials processes are being develop intensively
381
through investigating works. Among them some
382
processes are the most attractive for
383
decontaminating 137Cs from solution, were
384
adsorption/ion exchange, and electrochemical
385
processes with considerable removal capabilities.
386
These decontamination strategies research works
387
resulted the large proportion of the publications. For
388
the next topic of discussion mainly address to the
389
attractive investigation works in creating materials
390
for adsorption processes. The adsorption process is
391
usually not a stand-alone process, it is a complex
392
process involving the physical and chemical
393
reactions, although ion exchange is a special kind of
394
chemical adsorption. In the most cases, to improve
395
the capability and selectivity of the adsorption
396
materials, they are always modified or
397
functionalized with an ion-exchanger. As a result,
398
adsorption and ion exchange functions usually
399
occurred simultaneously during a typical adsorptive
400
removal process. Based on the origin of the
401
materials, variations in the composition of the
402
absorbent material will determine the mechanism
403
that dominates when it was used to process 137Cs.
404
Adsorption materials generally could be divided into
405
three categories, there are carbonaceous, clay, and
406
biomass materials/biosorbents.
407 408
Carbonaceous materials or activated carbon,
409
this material is a pioneer of investigation of the
410
adsorptive materials for the removal of various
411
contaminations (heavy metals or radionuclides)
412
from aqueous solutions. Due to their good active
413
adsorption sites and has special porous structure
414
(extremely large specific area), this material has
415
performed satisfied to its capability in the
416
adsorption of organic and inorganic contaminants.
417
To enhance their abilities to be more selective for
418
certain metal ion or radionuclide, some chemical
419
additives often to be added to the carbonaceous
420
materials [28]. Carbonaceous materials has the low
421
stability and selectivity properties towards the target
422
metal ions, so they require the modification/
423
immobilization with a selective inorganic ion
424
exchanger on their large surface of activated carbon.
425
This process can not only enhance the adsorption
426
capacity but also improve their stability and
427
selectivity properties. Some researchers have
428
conducted research on modification of activated
429
carbon materials, but these two studies will be very
430
interesting to be noted. They modified the natural
431
materials came from nature such as of rice hull and
432
areca nut where the surface of the material was
433
immobilized with nickel hexaxyanoferrate (NiHCF)
434
[29], or potassium nickel hexaxyanoferrate
435
(KNiHCF-GAC) to absorb Cs ions in solution [30].
436
The results show that these material has become
437
better in their performance for absorbing Cs ions in
438
solution, and the maximum adsorption capacity
439
reaches 163.9 mg/g for KNiHCF-GAC. Many
440
results of research have been reported from the use
441
of carbonaceous material to absorb metal ions or
442
radionuclides, but the disadvantage of this material
443
is the stability of the properties of the final product
444
is still rough. The process of making these materials
445
to achieve as a standardized product still needs to be
446
considered. And many more absorbent materials
447
made from activated carbon, such as those made as
448
carbon nanotubes, but this discussion is not
449
mentioned.
450 451
Other natural materials that got pay attention
452
for radionuclide decontamination such as 137Cs are
453
clay material as electrochemical process. This
454
natural material is very attractive because of its
455
good ion exchange capability, where ions such as
456
Na, K, Ca, Mg exist at their exchange site. Metal
457
ions such as 137Cs in solution will replace their
458
position in the clay material and then the sorption of
459
radionuclides can occur into the material. Many clay
460
materials have been intensively studied, such as
461
zeolite, bentonite, kaolinite minerals as absorbent
462
materials to absorb 137Cs, both for treatment
463
processing purposes and as buffer material in the
464
near surface disposal facilities [31,32]. But for
465
decontamination activities, these materials need to
466
be modified previously to increase or improve their
467
absorption capacity (cation exchange capacity /
468
CEC). Modification of clay material by using
469
nickel [33], or by pillarization of clay
470
(montmorillonite and geothite materials) before
471
used as absorbent [34]. Since clay materials have
472
alumina octahedral sheet in their structure
473
(especially for bentonite and zeolite), the lattice has
474
unbalance charge due to the Al-octahedral sheet
475
give the excess of negative charge. If any cation
476
present in solution (such as 137Cs), it could be
477
counterbalance to this negative charge in order to
478
neutralization the compound [35]. Figure 8 is the
479
illustration of bentonite structure.
480
481
Figure 8. The structure of bentonite mineral [35]
482 483
Naturally clay materials are widely used to
484
providing the alternative materials choice for
485
decontamination of 137Cs in the soil. Another
486
advantage by using the natural material is, this
487
natural material is easily available and attractive in
488
prices and easily bound to the immobilization
489
material of radioactive waste package.
490
491
Biomass material (as biosorbents) used to
492
absorb metal ions has also attracted the attention to
493
the researchers. Cross linking between persimmon
494
waste and sulfuric acid was used by Pangeni et al
495
[36] to eliminate 137Cs from the solution. The
496
adsorption capacity towards 137Cs has become
497
greatly increased after the used of this process.
498
There is also the creation of walnut shell and pine
499
cone for absorbing 137Cs by functionalizing with
500
NiCHF and Fe (III) HCF which are useful for
501
increasing the absorption capacity of materials to
502
metal ions. The advantage of this material is, as
503
materials derived from carbonaceous materials, the
504
management of spent material is easy. The
505
combustion process with an incinerator unit can
506
complete the volume reduction process, this
507
material will be reduced to almost 91.9% in volume
508
(at 500o C for 2 h).
509
510
Because the materials as previously
511
mentioned have the property of low capacity,
512
stability and small in size. The using of other
513
materials with more sophisticated technology
514
(advanced materials) can also be considered to be
515
created to eliminate 137Cs from the environment,
516
such as the use of graphene-like layers that are
517
chemically durable and resist to radiation emission.
518
The use of Prussian blue nano particles (PBNP)-
519
incorporated with polyvinyl alcohol (PVA) to form
520
a composite of nano particles [37], or to create a
521
unique structural properties of the titanate nanotubes
522
also promised their use to absorb 137Cs from solution
523
[38]. And there are many more materials in the form
524
of composite nano particles prepared by researchers
525
to absorb 137Cs from solution, however we do not
526
discussed it yet. Meanwhile, an important role in
527
the adsorption process of clay materials plays both
528
ion exchange and electrostatic interactions. The
529
modification and combination of these materials are
530
of considerable concern and necessity to improve
531
their adsorption capacity increased. Removal of
532
137Cs from the solution by using an adsorption and
533
ion exchange methods is summarized in Table 2
534
[26]. The leaching solution from contaminated soil
535
containing 137Cs is then processed with materials as
536
discussed above or processed it with an evaporation
537
unit, before finally the remaining solution from
538
processing results can be released into the
539
environment.
540 541
542 543
After the management of contaminated soil
544
waste is carried out by the wet method, we now
545
discuss the contaminated soil waste is treated in a
546
dry methods. The electrokinetic method will be
547
discussed in this part. Yu has conducted his
548
research on decontamination of 137Cs using the
549
electrokinetic method [39]. He conducted this
550
research to test the feasibility of electrochemical
551
methods removing 137Cs from soil inspired by the
552
Chernobyl accident. Electrokinetic decontamination
553
has a few unique advantages. It works by electro-
554
osmotic effects, the removal of contaminants by soil
555
flushing in where pressure-driven flow is so low
556
such in low-permeability soils as clays materials.
557
The location of the electrodes will determine the
558
electric field lines, and it causing the ions to move
559
along the electric field lines to reach a high level of
560
flow direction control. Electromigration of charged
561
species independent to soil pore size and thus it
562
applies equally to coarse and fine-grained soils.
563
This method has been widely used to remove
564
heavy metals from the soil. The experiment has used
565
a compartment model with a one-dimensional
566
electrokinetic process on the soil. To decontaminate
567
contaminants from the soil, electrokinetic soil
568
technology applies a low-level direct current to the
569
contaminated soil by placed the electrodes in the
570
soil samples. And according to their charge,
571
contaminants travel toward the cathode or anode.
572
The contaminants are then deposited at the
573
electrodes. The mass transfer rate can be divided
574
into four components. One is caused by pressure-
575
driven advection, by dispersion/diffusion, by ionic
576
migration and by electro-osmosis. The components
577
are obtained from the difference between mass
578
fluxes into the compartment and the fluxes out of
579
the compartment. The electrical potential appearing
580
in the mass flux expressions for electromigration,
581
and electro-osmosis might be related to the electric
582
current by charge flux of both diffusion and ionic
583
migration of all charged species. Large forces may
584
restore the charge balance on a time-scale much
585
faster than any other in the system. By assuming
586
that the solution outside the electric double layer is
587
electrically neutral, which means that there is no net
588
charge accumulation in each compartment, the
589
electric current will be constant along the one-
590
dimensional medium. Figure 9 is a schematic
591
diagram of the electrokinetic process used to extract
592
metal ions/radionuclides from the soil.
593
594
Figure 9. Schematic diagram of the electrokinetics soil 595
decontamination process [39]
596 597
The soil is flushed at a low velocity with
598
water constantly. The flushing is used to remove the
599
radionuclide that accumulates at the cathode. The
600
soil then was given a 100 V DC voltage using 2
601
inert electrodes. The application of the DC voltage
602
to soil causes the evolution of oxygen at the anode
603
and the evolution of hydrogen at the cathode
604
occurred. The effect of electrokinetic processes on
605
the soil also depends on the sorption and diffusion
606
parameters of radionuclides in the soil.
607
608
High sorption and slow diffusion properties
609
of the soil, makes radionuclides cleaning up process
610
take a long time, a few months. Increasing DC
611
current on the soil sample can reduce the treatment
612
time. In materials that have good absorption ability
613
such as bentonite, the treatment time will be longer.
614
Figure 10 shows the typical of remaining fraction of
615
137Cs after treatment by using electrokinetic method
616
[39]. A high of Kd value will cause the treatment
617
time of 137Cs much longer.
618
619
Figure 10. Remaining fraction of activity during the treatment, 620
with variation of Kd values (m3kg-1), modification from 621
ref.[39].
622 623
Likewise the presence of organic matter in the
624
soil can reduce the decontamination ability of
625
electrokinetic devices. Radionuclides will be
626
associated with organic matter in the soil so that the
627
effect of soil pH is also important. Increasing pH in
628
the soil causes the functional groups in organic
629
matter to do the protonization processes, and
630
radionuclides absorbed in organic matter hardly. In
631
the electrokinetic decontamination process at least
632
there will be affected by several parameters such as
633
the activity of metal ion concentration in the soil,
634
electric current density, electrode distance, flow of
635
washing solution (chemical agent), type of soil
636
sample, treatment time, soil pH etc. Manipulation of
637
all parameter values will obtaine the optimal
638
conditions of the electrokinetic process to be able to
639
decontaminate metal ions or radionuclides such as
640
137Cs from the contaminated soils.
641 642
In the course of time, this method has been
643
studied more advance by Cameselle [40], Shahrani
644
[41] and Mao [42]. Then to improve the
645
decontamination results of 137Cs, electrokinetic
646
method is combined with other methods such as
647
water flushing [43], acid enhanced [44] and
648
electodialytic [45].
649
650
From the study, there is an interesting information,
651
where soil from the clean-up resulted is processed
652
by classifying it based on their particle size. This
653
method is very interesting to use as an initial stage
654
of decontamination proses of contaminated soils
655
before other methods are used to extract 137Cs from
656
contaminated soils. It is known that 137Cs will be
657
absorbed in soil particles, and it was believed that
658
137Cs will bind stronger in the smaller particle sizes
659
of soil. Where the smaller the particle, the stronger
660
137Cs are bound due to in the smaller particle sizes
661
contain many mineral fragment. The 137Cs
662
deposited on soils with tightly bound at the
663
exchangeable site of the soil. Kim et.al. used a
664
sieving method based on the differences in particle
665
size of the soil, contaminated soil was managed
666
where 3 sieve sizes were <0.063, 0.063 <x <0.1,>
667
0.1 mm was used [27]. Particle size distribution
668
used for the research is highly dependent on the
669
characteristics of the soil at the contaminated
670
location. Kim took the soil samples with particle
671
size > 0.063 mm for treatment, because the soil with
672
particle size <0.063 mm contained high
673
concentration of 137Cs and then was immediately
674
immobilized.
675
676
For the experiment, Kim et.al. taken 50 drums
677
were selected based on the surface effective doses
678
rate of waste drums. There are about 7% of drums
679
having a surface effective dose rate exceed from
680
0.05 mR/h, 33% of drums below 0.02 mR/h, while
681
the majority of drums (60%) are in the range
682
between 0.02 - 0.05 mR/h. About 10 kg of
683
contaminated soil is taken from each drum, and then
684
dried before the sieving process based on their
685
particle size. The radioactive Cs target as a part of
686
soil that used are have the concentration level of >
687
400 Bq/kg. Radiometric measurement of soil
688
samples used an MCA units. The soil sample is first
689
dried for more than a week before being used for the
690
experiments. Soil that has dried and then classified
691
with a sieving unit into 3 particle sizes for 30
692
minutes. The results of the particle size
693
classification analysis of contaminated soil are
694
shown in Table 3.
695
696 697
The radioactive concentrations of 137Cs in the parts
698
of contaminated soil were higher than the target
699
concentration level, especially in the drums with
700
has surface effective dose > 0.05 mR/h. The soil
701
with particle size with range between 0.063 to 1.0
702
mm provides the largest portion in soil particle size.
703
It is easier to decontaminate a soil having a particle
704
size larger than 1.0 mm, the soil particles having
705
sizes that range from 0.063 to 1.0 mm is selected to
706
be washed with water to take the 137Cs
707
contaminant. The smaller size of the soil particle
708
resulted the higher radioactive concentration emitted
709
from soil particles. Soil that has the particle size
710
smaller than 0.063 mm and then to be processed
711
with compaction method to reduce their volume
712
before to immobilized it. By using water washing
713
method, the fine particles (<0.063 mm) gave
714
extremely low in removal efficiency of 137Cs.
715
Contaminated soil is then washed by using the
716
chemical agents such as citric acid, citric acid +
717
HNO3, NH4NO3, FeCl3, (COOK)2⋅H2O,
718
(NH4)2SO4, H2C2O4⋅H2O, NaOH, and KI solutions
719
[22,39]. All the chemical agents were compared
720
their ability to remove 137Cs from contaminated soil.
721
The use of oxalic acid and KI chemical agents has
722
given a high removal efficiency value to
723
decontaminate 137Cs from the soil. Around 50% of
724
137Cs can be taken out from the soil contaminated by
725
both chemical agents. What is more, the price of
726
both chemical agents is reasonable. Solution from
727
extraction resulted which is containing the 137Cs
728
concentration is then treated by using one of the
729
absorbent material as previous mentioned, while the
730
absorbent can be advance processed in various
731
ways, such as compaction, incineration (combustion
732
then ash are immobilized), immobilization and
733
polymerization (when using organic resins as
734
absorbents).
735
736
The final result of this study is a proposal of
737
the strategy to treat appropriately the contaminated
738
soil waste from the land in South Tangerang. Here,
739
we suggest 3 proposals to be considered, one of
740
which is hopely the most suitable method to be
741
applied to manage the waste of contaminated soil
742
from South Tangerang,
743 744
In the first proposal, 137Cs contaminated soil
745
waste is treated by separation method according to
746
their particle size. Three sizing particle sizes are
747
object of this process. Only soil with particle size
748
greater than 0.063 mm will be further processed.
749
Advanced treatment by using wet method
750
(chemically), where contaminated soil (with particle
751
size greater than 0.063 mm) is contacted with
752
chemical agents such as KI or H2C2O4 to remove
753
137Cs from the soil into solution. The solids part
754
which are obtained are expected to be low in 137Cs
755
concentration, so they can be released into the
756
environment. The obtained liquid is then processed
757
again by absorption method use the material that has
758
selectively absorption property to 137Cs. The liquid
759
which “clean” from 137Cs or a low concentration of
760
137Cs can then be released into the environment, or
761
used as a mixing fluid in the immobilization
762
process. The solids which are rich with 137Cs are
763
then immobilized by compaction and cementation
764
methods becomes as waste packages. The waste
765
package is then sent to a long-term storage facility
766
(LTSF). The flow chart of proposal 1 is shown in
767
Figure 11. We do not use HNO3 or H2SO4 to extract
768
137Cs from soil due to avoid of strong acid in the
769
next processes.
770
771
In the second proposal, we propose the
772
contaminated soil is treated with a dry method. In
773
the beginning of the treatment process is similarly as
774
did in the first proposal, where the contaminated soil
775
is separated based on particle size. But in the next
776
process, the accumulation process of 137Cs in the
777
soil is done by dry method (electrokinetic method),
778
where the soil which has a particle size > 0.063 mm
779
is put into a column. The column and then is given a
780
DC electric voltage and a flush water to maintain
781
soil pH.
782
783
Figure 11. The first proposal (wet processes) 784
785
Based on the different in electrical voltage,
786
the metal ion as a positive charge (such as 137Cs)
787
will move and be deposited at the cathode, and vice
788
versa to anode. To make the catode saturated with
789
137Cs, the long treatment time required. And then the
790
cathode immobilized by compacting or cementing.
791
Soil that was contaminated then becomes less
792
contaminated, and can be released into the
793
environment or applied as the cover of waste
794
package on the LTSF. The flow chart of the
795
processes is shown in Figure 12.
796
797
Figure 12. The second proposal (dry process) 798
799
As a comparison of the two kinds of
800
treatment processes, the treatment method in the
801
first proposal is relatively more familiar and has
802
more proven technology compared to the process
803
which is carried out in the second ones. In the first
804
treatment method, the treatment time also looks
805
relatively faster and the material used is more
806
reliable and feasible than the materials in the second
807
proposal. Processing with electrokinetic method will
808
require more lot of energy, longer treatment time,
809
more complicated process, and the technology has
810
not been proven (relatively expensive). The use of
811
the treatment method proposed in the first proposal
812
is more promising to be applied in the near future.
813
Affected parameters must be obtained completely so
814
the engineers can design the required processing
815
units. However good mastery of electrokinetic
816
methods can do the cleanup activities in situ.
817
818
And the last proposal -perhaps this is the
819
easiest method to do- is the compaction method
820
applied to all drums containing the remediated soil.
821
The 100L drum is compacted in the inside of the
822
200L drum, then the 200L drum contained the
823
results of the compaction will be sent to the long-
824
term storage facility
825 826
