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Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method
G Model EA 24734 No. of Pages 5
Electrochimica Acta xxx (2015) xxx–xxx
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Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta
Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method Gye-Nam Kim * , Seung-Soo Kim, Uk-Rang Park, Jei-Kwon Moon Korea Atomic Energy Research Institute, 1045 Daedeokdaero, Yuseong-gu, Daejeon 305-353, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Article history: Received 22 November 2014 Received in revised form 10 March 2015 Accepted 28 March 2015 Available online xxx
The soil contaminated with cesium was sampled at an area near a nuclear facility in Korea. Electrokinetic decontamination equipment and electrokinetic-elctrodialytic decontamination equipment were manufactured to decontaminate the contaminated soil. The removal efficiency according to the lapsed time by the electrokinetic decontamination equipment and the electrokinetic-elctrodialytic decontamination equipment was investigated through several experiments. The difference between the removal efficiency of the electrokinetic-elctrodialytic equipment without an anion exchange membrane and that with an anion exchange membrane was investigated through several experiments. The removal efficiency of 137Cs+ from soil by electrokinetic-electrodialytic decontamination technology was higher than that of 137Cs+ from soil by electrokinetic decontamination technology. The removal efficiency of 137 Cs+ was sharply reduced after 7 days on using electrokinetic decontamination, because the 137Cs+ on the surface of the soil particles had almost been removed for 7 days. The removal efficiency of 137Cs+ was increased after 7 days on using electrokinetic-electrodialytic decontamination with soil stirring. The soil stirring accelerated the desorption of cesium ions from soil and an anion exchange membrane shortened the period for removing cesium from the soil cell by preventing the influx of cesium ions into the anode room. The more the initial radioactivity concentration of soil increased, the more the removal efficiency of 137Cs+ from soil increased. When the electrokinetic-electrodialytic decontamination period of 0.3– 7.0 days elapsed, 137Cs+ in the soil was removed by about 12–83%. When the electrokinetic-electrodialytic decontamination period of 10–21 days elapsed, the 137Cs+ in soil was removed by about 91–97%. ã 2015 Elsevier Ltd. All rights reserved.
Keywords: Decontamination Cesium Removal Soil Electrokinetic Electrodialytic
1. Introduction The radioactive soil at the KAERI radioactive waste storage facility has a slightly high hydro-conductivity, and was mainly contaminated with 137Cs 30–35 years ago. Recently, a soil washing method was applied to remove 137Cs from the radioactive soil, but it appeared that the removal efficiency of 137Cs was low, and a lot of waste solution was generated [1]. Meanwhile, an electrokinetic decontamination method provides a high removal efficiency of 137 Cs and generates little waste effluent. Thus, it was suggested that an electrokinetic decontamination method is a suitable technology in consideration of the soil characteristics near South Korean nuclear facilities [2]. The electrokinetic process holds great promise for the decontamination of contaminated soil as it has a high removal efficiency and is time-effective for a low permeability. Electrokinetic decontamination can be used to treat soil contaminated with inorganic species and radionuclides [3].
* Corresponding author.
The main mechanisms of a contaminant's moveme nt in an electrical field involved in electrokinetic technology are the electro-migration of the ionic species and electro-osmosis. Electro-migration probably contributes significantly to the removal of contaminants, especially at high concentrations of ionic contaminants and/or a high hydraulic permeability of soil [4]. The cathode reaction should be depolarized to avoid the generation of hydroxides and their transport in soil. The selected liquid, also known as a purging reagent, should induce favorable pH conditions in soil, and/or interact with the incorporated heavy metals so that these heavy metals are removed from the soil [5]. Recently, researchers have been investigating whether this method can be used to remove subsurface contaminants, and they have compiled published research on the use of electrokinetic techniques to decontaminate fine-grained soil and have discussed some of the problems that occur during this process [6–8]. Meanwhile, researchers have also tried to develop soil flushing techniques in which soil-bound contaminants are transferred to a liquid phase by desorption and solubilization. Several flushing solutions have been investigated, such as water, acids, bases,
http://dx.doi.org/10.1016/j.electacta.2015.03.208 0013-4686/ ã 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: G.-N. Kim, et al., Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method, Electrochim. Acta (2015), http://dx.doi.org/10.1016/j.electacta.2015.03.208
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chelating agents, alcohol, and other additives [9]. In practice, acid washing and chelator soil washing are the two most prevalent removal methods [10–11]. Recently, acetic acid or sodium dodecyl sulfate was used as an electrolyte for electrokinetic decontamination to increase the removal efficiency of metal [12–13]. In addition, most of the electrokinetic equipment has been manufactured as a horizontal type. Laboratory-scale electrokinetic decontamination has been performed for TRIGA soil during the past 5 years, but at this time, a study related to washing- electrokinetic decontamination was performed [14–15]. Jing-Yuan Wang (2007) started to develop vertical electrokinetic equipment to easily remove the contaminants accumulated at a cathode. The equipment has a cathode in the upper side so that the reagent in the soil cell might flow upward, and the contaminants in the soil cell might be accumulated in the upper side. Upward vertical electrokinetic equipment has already been used to remove heavy metal from kaolin [16] and to remove organic material from some of the soil [17]. Meanwhile, the electrodialytic method has generally been used for treating waste solution and soil remediation, which attaches an ion exchange membrane at the anode room or cathode room [18–21]. In this study, the soil contaminated with cesium was sampled at an area near a nuclear facility in Korea. The electrokinetic decontamination equipment and electrokinetic-elctrodialytic decontamination equipment were manufactured to decontaminate the contaminated soil. The difference between the removal efficiency according to the lapsed time by the electrokinetic decontamination equipment and the electrokinetic-elctrodialytic decontamination equipment was investigated through several experiments. The difference between the removal efficiency of the electrokinetic-elctrodialytic equipment without an anion exchange membrane and that with an anion exchange membrane was investigated through several experiments. In addition, the removal efficiency trend according to different cesium radioactivity of soil was drawn out through several experiments. 2. Materials and methods 2.1. Characteristics of contaminated soil The soil in a drum was contaminated with cesium in a drum, and Table 1 shows the cesium soil hydraulic properties. The saturation degree of the surface at a nuclear facility site is small, and the hydraulic conductivity of the soil is a little lower. The pH of the soil is a little acidic. 2.2. Manufacturing of electrokinetic decontamination equipment
Fig. 1. A schematic diagram of electrokinetic decontamination equipment.
4.5 5.9 14.5 cm for Experiment 1. As Experiment 1, a paper filter was inserted between the electrode compartment and the contaminated soil to prevent an influx of soil. A pump supplies a reagent to the reagent reservoir at 0.5–1 ml/min, and the reagent reservoir supplies a chemical solution to the anode room. The electric current between electrodes is 0.6A, and the electric voltage between electrodes is 4.5–5.2 V. The temperature in the cathode room was below 65 C. 0.5 M of HNO3 was used as electrolyte reagent to accelerate the desorption of cesium from soil on stirring soil. Experiments 1and 2 used a different soil sample radioactivity, and the electrokintic decontamination period was 21 days without exception. In Experiment 2, an anion exchange membrane was inserted between the anode room and the contaminated soil to prevent an influx of cesium ions, and a paper filter was inserted between the cathode room and the contaminated soil. 200 g of contaminated soil was placed into a horizontal soil cell, namely, the ratio of liquid (mg)/ soil (g) is 0.5. 2.3. Manufacturing of electrokinetic-electrodialytic decontamination equipment To increase the removal velocity of cesium from the soil, electrokinetic-electrodialytic decontamination equipment was manufactured. This equipment mixed the electrokinetic and electrodialytic concepts. Fig. 3 shows a schematic diagram of electrokinetic-electrodialytic decontamination. In this study, the
Electokinetic equipment decontamination was manufactured for the experiments. Fig. 1 shows a schematic diagram of the electrokinetic decontamination equipment, and Fig. 2 shows the manufactured electrokinetic decontamination equipment. The electrokinetic decontamination equipment consists of a horizontal soil cell, two electrode compartments (anode/cathode rooms), a reagent reservoir, an effluent reservoir, and a power supply, and 480 g of contaminated soil was placed into a horizontal soil cell of
Table 1 Hydraulic properties of cesium soil. Parameter
Value
Bulk density (g/cm3) Porosity (%) Hydraulic conductivity (cm/sec) Water content (%) pH
1.51 41.8 3.8 105 23.4 5.7 Fig. 2. Manufactured electrokinetic decontamination equipment.
Please cite this article in press as: G.-N. Kim, et al., Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method, Electrochim. Acta (2015), http://dx.doi.org/10.1016/j.electacta.2015.03.208
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cathode room and the contaminated soil. 200 g of contaminated soil was placed into a horizontal soil cell, namely, at a ratio of liquid (mg)/soil(g) of 0.5. 2.4. Radioactivity measurement for soil
Fig. 3. A schematic diagram of the electrokinetic-electrodialytic decontamination equipment.
electrokinetic-electrodialytic decontamination equipment was manufactured as shown in Fig. 4. An impellor was used in the electrokintic-electrodialytic decontamination experiments. The impellor was installed in the middle of the horizontal soil cell, and the rpm of the impellor was 60. A pump supplies a reagent to the reagent reservoir by 2–3 ml/min, and the reagent reservoir supplies a chemical solution to the anode room. The electric current between electrodes is 0.6A, and the electric voltage between electrodes is 4.5–5.2 V. The temperature in the cathode room was below 50 C. Experiments 3 and 4 used soil samples with a different radioactivity, and the electrokintic decontamination period was 21 days without exception. Also, 200 g of contaminated soil was placed into a horizontal soil cell, namely, at a ratio of liquid (mg)/soil (g) of 0.5. In Experiment 4, an anion exchange membrane was inserted between the anode room and the contaminated soil to prevent an influx of cesium ions, and a paper filter was inserted between the
The initial cesium concentration for the soil was measured using a Multi-Channel Analyzer (MCA) with a standard tube of 1,000 cc, QCY48 (Amersham), manufactured by the Korea Reach Institute Standards and Sciences. The MCA operates in a pulse height analyzer mode. The scintillation counter measures the pulse height distribution from a gamma ray source. The amplitude of an incoming analogue pulse is digitized by an analogue digital converter (ADC), and the digital value is used as the address of the incremented memory location. Thus, the screen display of the number of counts vs. the channel number is really a histogram of the number of counts vs. the pulse height, i.e., a pulse height spectrum. The time required to measure the radioactivity concentration of a gravel sample using the MCA was estimated to be 4–8 hours. The initial radioactivity concentration of the soil before electrokinetic-electrodialytic decontamination was calculated. The electrokinetic-electrodialytic experiment was stopped at pre-determined interim times, the soil samples were extracted from the soil cell, and the radioactivity concentration of the soil samples were then measured using the MCA. The soil samples were returned to their initial locations in the soil cell, and the experiment was continuously restarted. The removal efficiency of the nuclides was calculated as a ratio of the initial soil concentration, and the soil concentrations were measured at pre-determined interim times. After completion of the electrokinetic-electrodialytic decontamination experiments for radioactive soil with initial concentrations of 1.0–25 Bq/g, the residual concentration of soil was calculated. Finally, the decontamination period required for decontaminating the initial soil concentration to a clearance concentration level (137Cs:0.1 Bq/g) was estimated using the experimental electrokinetic-electrodialytic results. 3. Results and discussion 3.1. Electrokinetic decontamination results Cesium (137Cs+) in the contaminated soil in the electrokinetic decontamination was removed by electro-osmosis, electro-migration, and a hydraulic pressure flow, as in the following equation: j ¼ ½ðko þ km ÞRrI þ kh rpC
Fig. 4. Manufactured electrokinetic-electrodialytic decontamination equipment.
D
t2
rC
(1)
where j is the molar flux of the species per unit pore area, Ko is the electro-osmotic permeability, Km is the electro-migration coefficient, R is the electric resistance, I is the electric current, Kh is the hydraulic permeability, P is the pressure, C is the molar concentration, D is the diffusion coefficient, and t is a non-dimensional tortuosity. To remove cesium from the soil, electrokinetic decontamination equipment was manufactured. Table 2 shows the results of the removal efficiency according to the lapsed time by the electrokinetic decontamination as Experiment 1. When the decontamination period of 0.3 days, 2 days, and 7 days elapsed, 137Cs+ in the soil was removed by about 10%, 30%, and 60%. However, the removal efficiency of 137Cs+ was sharply reduced after 7 days, because the 137 Cs+ on the surface of the soil particles had almost been removed for 7 days. It is considered that the 137Cs+ located deeply in soil cannot be removed by the electromagnetic strength between cathode electrode and cesium ions, because the ion of cesium is one positive charge. Thus, when the decontamination period of
Please cite this article in press as: G.-N. Kim, et al., Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method, Electrochim. Acta (2015), http://dx.doi.org/10.1016/j.electacta.2015.03.208
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Table 2 Removal efficiency according to the lapsed time by electrokinetic decontamination (Experiment 1).
Removal Eff. 1 Removal Eff. 2 Removal Eff. 3 Removal Eff. 4
Initial radioactivity concentration
0.3 2 7 10 14 21 (days) (days) (days) (days) (days) (days)
22.7 (Bq/g)
10.8%
33.7%
62.3%
64.3%
68.4%
73.3%
13.6 (Bq/g)
9.6%
32.4%
60.5%
63.7%
67.8%
71.7%
6.2 (Bq/g)
8.7%
30.2%
59.6%
63.4%
66.7%
70.4%
1.6 (Bq/g)
7.4%
29.5%
58.2%
62.5%
65.5%
69.4%
Table 4 Removal efficiency according to the lapsed time by electrokinetic-stirring decontamination without an anion exchange membrane (Experiment 3).
Removal Eff. 1 Removal Eff. 2 Removal Eff. 3
J¼ 10 days, 14 days, and 21 days elapsed, the 137Cs+ in the soil was removed by about 63%, 66%, and 71%. Meanwhile, the more the initial radioactivity concentration of soil increased, the more the removal efficiency of 137Cs+ from soil increased. It is considered that in case of the high radioactivity concentration of soil, the greater amount of 137Cs+ attached to the surface of the soil particles had been removed during same decontamination period. Table 3 shows the results of the removal efficiency according to the lapsed time by electrokinetic decontamination with an anion exchange membrane as Experiment 2. 200 g of contaminated soil occupied a lower part of a horizontal soil cell, and the electrolyte occupied an upper part of a horizontal soil cell. An anion exchange membrane was inserted between the anode room and the contaminated soil to prevent an influx of cesium ions in the electrolyte occupied an upper part of a horizontal soil cell. It is not necessary to install a cation-exchange membrane between the cathode room and the soil cell to prevent an influx of OH from the cathode room, because the pH of the electrolyte in the cathode room was below 1 due to a constant efflux of the electrolyte through the outlet of the cathode room. On the other hand, an anion exchange membrane was inserted between the anode room and the soil cell to prevent an influx of cesium ions from soil cell. If cesium ions flow into the anode room from the soil cell, the period for removing cesium from the soil cell will be prolonged due to the electrolyte mixed with cesium ions in the anode room. When the decontamination period of 0.3 days, 2 days, and 7 days elapsed, 137Cs+ in the soil was removed by about 9%, 30%, and 58%. Similarly, the removal efficiency of 137Cs+ was sharply reduced after 7 days. When the decontamination period of 10 days, 14 days, and 21 days elapsed, the 137Cs+ in soil was removed by about 62%, 64%, and 69%. The removal efficiencies of Experiment 1 and Experiment 2 were almost the same values. 3.2. Electrokinetic-stirring and electrokinetic-electrodialytic decontamination results Cesium (137Cs+) in the soil cell in the electrodalytic decontamination was removed on the basis of the following equation: Table 3 Removal efficiency according to the lapsed time by electrokinetic decontamination with an anion exchange membrane (Experiment 2).
Removal Eff. 1 Removal Eff. 2 Removal Eff. 3
Initial radioactivity concentration
0.3 2 7 10 14 21 (days) (days) (days) (days) (days) (days)
21.6 (Bq/g)
10.1%
32.5%
60.1%
62.7%
66.5%
71.4%
11.8 (Bq/g)
8.9%
30.2%
58.2%
62.1%
63.8%
69.3%
1.4 (Bq/g)
7.1%
27.4%
56.9%
60.3%
62.1%
67.2%
Initial radioactivity concentration
0.3 2 7 10 14 21 (days) (days) (days) (days) (days) (days)
23.4 (Bq/g)
11.2%
38.6%
71.5%
77.4%
80.2%
83.7%
15.6 (Bq/g)
10.5%
37.5%
68.9%
75.3%
78.3%
81.5%
1.5 (Bq/g)
7.9%
32.8%
65.8%
70.4%
74.6%
78.4%
h dI F dAM
where J is the molar flux, h is the current efficiency, F is the Faraday constant, and AM is the effective area of ion exchange membrane. Cesium is removed from soil by ion exchange through stirring with nitric acid solution in the soil cell. The action of cesium and nitric acid solution is expressed by the following equation: HNO3
CsX ! Csþ þ HX þ NO 3 where X represents the soil matrix. Cesium (137Cs+) in the contaminated soil in the electrokineticstirring decontamination equipment was removed by electro-osmosis, electro-migration, and ion exchange. The pH achieved in the soil cell on using 0.5 M of HNO3 as electrolyte was below 0.5, which accelerated the desorption of cesium ions from soil. The experimental electrokinetic- stirring conditions were as follows. Table 4 shows the results of the removal efficiency according to the lapsed time by electrokinetic-stirring decontamination without an anion exchange membrane as Experiment 3. When the decontamination period of 0.3 days, 2 days, and 7 days elapsed, 137Cs+ in the soil was removed by about 10%, 37%, and 68%. However, the removal efficiency of 137Cs+ was reduced after 7 days, because the 137Cs+ on the surface of the soil particle had almost been removed for 7 days. However, the removal efficiency of Experiment 3 was increased more than Experiments 1 and 2, because Experiment 3 used an impellor to increase the surface area of soil particles making contact with electrolyte in the horizontal soil cell. In addition, when the decontamination period of 10 days, 14 days, and 21 days elapsed, the 137Cs+ in soil was removed by about 75%, 78%, and 81%. The removal efficiency of Experiment 3 was increased more than Experiment 1 and 2 due to the impellor. Table 5 shows the results of the removal efficiency according to the lapsed time by electrokinetic-electrodialtic decontamination with an anion exchange membrane as Experiment 4. An anion exchange membrane was inserted between the anode room and the contaminated soil to prevent an influx of cesium ions in the electrolyte occupying an upper part of a horizontal soil cell. When the decontamination period of 0.3 days, 2 days, and 7 days elapsed, 137 Cs+ in the soil was removed by about 12%, 38%, and 83%. Table 5 Removal efficiency according to the lapsed time by electrokinetic-electrodialytic decontamination with an anion exchange membrane (Experiment 4).
Removal Eff. 1 Removal Eff. 2 Removal Eff. 3 Removal Eff. 4
Initial radioactivity concentration
0.3 2 7 10 14 21 (days) (days) (days) (days) (days) (days)
20.5 (Bq/g)
14.0%
40.7%
86.5%
92.3%
95.1%
12.4 (Bq/g)
12.7%
38.1%
83.9%
91.1%
93.5%
5.8 (Bq/g)
11.9%
36.7%
81.4%
87.5%
91.3%
1.7 (Bq/g)
11.1%
35.3%
79.5%
85.3%
89.2%
98.2% 0.37 97.2% 0.35 95.4% 0.27 94.1% 0.1
Please cite this article in press as: G.-N. Kim, et al., Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method, Electrochim. Acta (2015), http://dx.doi.org/10.1016/j.electacta.2015.03.208
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However, the removal efficiency of 137Cs+ was reduced after 7 days, because the 137Cs+ on the surface of the soil particles had almost been removed for 7 days. The removal efficiency of Experiment 4 was increased more than that of Experiment 3 because Experiment 4 used the anion exchange membrane to prevent the contamination of 137Cs+ in the anode room. When the decontamination period of 10 days, 14 days, and 21 days elapsed, the 137Cs+ in soil was removed by about 91%, 93%, and 97%. Meanwhile, the more the initial radioactivity of soil decreased, the more the removal efficiency of 137Cs+ was reduced. The soil stirring accelerated the desorption of cesium ions from soil and an anion exchange membrane shortened the period for removing cesium from the soil cell by preventing the influx of cesium ions into the anode room. Conclusively, the removal efficiency of 137Cs+ from soil by electrokinetic-electrodialytic decontamination technology was higher than that of 137Cs+ from soil by electrokinetic decontamination technology. In addition, the anion exchange membrane in electrokinetic-electrodialytic decontamination increased the removal efficiency of 137Cs+ from soil due to the interception of an infiltration of 137Cs+ in the anode room. 4. Conclusions The removal efficiency of 137Cs+ from soil by electrokineticstirring decontamination technology was higher than that of 137Cs+ from soil by electrokinetic decontamination technology. In addition, the anion exchange membrane in electrokinetic-electrodialytic decontamination increased the removal efficiency of 137Cs+ from soil due to the interception of an infiltration of 137Cs+ in the anode room. Meanwhile, the more the initial radioactivity concentration of soil increased, the more the removal efficiency of 137Cs+ from soil increased. When the electrokinetic-electrodialytic decontamination period of 0.3–7.0 days elapsed, 137Cs+ in the soil was removed by about 12 - 83%. However, the removal efficiency of 137Cs+ was sharply reduced after 7 days because the 137 Cs+ on the surface of soil particles had almost been removed for 7 days. When the decontamination period of 10–21 days elapsed, the 137Cs+ in soil was removed by about 91–97%. The soil stirring
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accelerated the desorption of cesium ions from soil and an anion exchange membrane shortened the period for removing cesium from the soil cell. Acknowledgements This project was carried out under the Nuclear R&D Program by MOST in KOREA. References [1] G.N. Kim, W.K. Choi, C.H. Bung, J.K. Moon, J. Ind. Eng. Chem. 13 (2007) 406–413. [2] G.N. Kim, Y.H. Jung, J.J. Lee, J.K. Moon, Journal of the Korean Radioactive Waste Society 25 (2) (2008) 146–153. [3] K. Reddy, C.Y. Xu, S. Chinthamreddy, J. Hazard. Mater. B 84 (2001) 279–296. [4] S. Pamukcu, J.K. Wittle, Environ. Prog. 11 (3) (1992) 241–270. [5] K. Reddy, S. Chinthamreddy, J. Geotech. Geoenviron. Eng. (March) (2003) 263–277. [6] F. Braud, S. Tellier, M. Astruc, 68 (1998) 105–121. [7] S.O. Kim, S.H. Moon, K.W. Kim, Water Air and Soil Pollution 125 (2001) 259–272. [8] M.M. Page, C.L. Page, Journal of Environmental Engineering. ASCE 128 (2002) 208–219. [9] C. Chaiyaraksa, N. Sriwiriyanuphap, Chemosphere 546 (2004) 129–135. [10] C.G. Rampley, K.L. Ogden, Environ. Sci. Technol. 32 (7) (1988) 987–993. [11] B. Sun, F.J. Zhao, E. Lombi, S.P. McGrath, Environ Pollut. 113 (2001) 111–120. [12] B. Kornilovich, N. Mishchuk, K. Abbruzzese, G. Pshinko, R. Klishchenko, Colloids and Surfaces A: Physicochem. Eng. Aspects 265 (2005) 114–123. [13] A. Giannis, E. Gidarakos, A. Skouta, Desalination 211 (2007) 249–260. [14] G.N. Kim, Y.H. Jung, J.J. Lee, J.K. Moon, C.H. Jung, Separation and Purification Technology 63 (2008) 116–121. [15] G.N. Kim, W.Z. Oh, H.J. Won, W.K. Choi, J. Ind. Eng. Chem. 9 (3) (2003) 306–313. [16] J.Y. Wang, X.J. Huang, J.C.M. Kao, O. Stabnikova, Journal of Hazardous Materials B136 (2006) 532–541. [17] J.Y. Wang, X.J. Huang, J.C.M. Kao, O. Stabnikova, Journal of Hazardous Materials B144 (2007) 292–299. [18] T.R. Sun, L.M. Ottosen, P.E. Jensen, Pulse current enhanced electrodialytic soil remediation: Comparison of different pulse frequencies, J. Hazard. Mater. 237– 238 (2012) 299–306. [19] G.M. Nystrom, L.M. Ottossen, A. Villumsen, Test of experimental set-ups for electrodialytic removal of Cu Zn, Pb and Cd from different contaminated harbor sediments, Eng. Geol. 77 (2005) 349–357. [20] P.E. Jensen, L.M. Ottosen, B. Allard, Electro dialytic versus acid extraction of heavy metals from soil washing residue, Electrochim. Acta 86 (2012) 115–123. [21] M.R. Jakobsen, J. Fritt-Ramussen, S. Nielsen, L.M. Ottosen, Electrodialytic removal of cadmium from wastewater sludge, J. Hazard. Mater. 106 (2004) 127–132.
Please cite this article in press as: G.-N. Kim, et al., Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method, Electrochim. Acta (2015), http://dx.doi.org/10.1016/j.electacta.2015.03.208
Electrochimica Acta xxx (2015) xxx–xxx
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Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta
Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method Gye-Nam Kim * , Seung-Soo Kim, Uk-Rang Park, Jei-Kwon Moon Korea Atomic Energy Research Institute, 1045 Daedeokdaero, Yuseong-gu, Daejeon 305-353, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Article history: Received 22 November 2014 Received in revised form 10 March 2015 Accepted 28 March 2015 Available online xxx
The soil contaminated with cesium was sampled at an area near a nuclear facility in Korea. Electrokinetic decontamination equipment and electrokinetic-elctrodialytic decontamination equipment were manufactured to decontaminate the contaminated soil. The removal efficiency according to the lapsed time by the electrokinetic decontamination equipment and the electrokinetic-elctrodialytic decontamination equipment was investigated through several experiments. The difference between the removal efficiency of the electrokinetic-elctrodialytic equipment without an anion exchange membrane and that with an anion exchange membrane was investigated through several experiments. The removal efficiency of 137Cs+ from soil by electrokinetic-electrodialytic decontamination technology was higher than that of 137Cs+ from soil by electrokinetic decontamination technology. The removal efficiency of 137 Cs+ was sharply reduced after 7 days on using electrokinetic decontamination, because the 137Cs+ on the surface of the soil particles had almost been removed for 7 days. The removal efficiency of 137Cs+ was increased after 7 days on using electrokinetic-electrodialytic decontamination with soil stirring. The soil stirring accelerated the desorption of cesium ions from soil and an anion exchange membrane shortened the period for removing cesium from the soil cell by preventing the influx of cesium ions into the anode room. The more the initial radioactivity concentration of soil increased, the more the removal efficiency of 137Cs+ from soil increased. When the electrokinetic-electrodialytic decontamination period of 0.3– 7.0 days elapsed, 137Cs+ in the soil was removed by about 12–83%. When the electrokinetic-electrodialytic decontamination period of 10–21 days elapsed, the 137Cs+ in soil was removed by about 91–97%. ã 2015 Elsevier Ltd. All rights reserved.
Keywords: Decontamination Cesium Removal Soil Electrokinetic Electrodialytic
1. Introduction The radioactive soil at the KAERI radioactive waste storage facility has a slightly high hydro-conductivity, and was mainly contaminated with 137Cs 30–35 years ago. Recently, a soil washing method was applied to remove 137Cs from the radioactive soil, but it appeared that the removal efficiency of 137Cs was low, and a lot of waste solution was generated [1]. Meanwhile, an electrokinetic decontamination method provides a high removal efficiency of 137 Cs and generates little waste effluent. Thus, it was suggested that an electrokinetic decontamination method is a suitable technology in consideration of the soil characteristics near South Korean nuclear facilities [2]. The electrokinetic process holds great promise for the decontamination of contaminated soil as it has a high removal efficiency and is time-effective for a low permeability. Electrokinetic decontamination can be used to treat soil contaminated with inorganic species and radionuclides [3].
* Corresponding author.
The main mechanisms of a contaminant's moveme nt in an electrical field involved in electrokinetic technology are the electro-migration of the ionic species and electro-osmosis. Electro-migration probably contributes significantly to the removal of contaminants, especially at high concentrations of ionic contaminants and/or a high hydraulic permeability of soil [4]. The cathode reaction should be depolarized to avoid the generation of hydroxides and their transport in soil. The selected liquid, also known as a purging reagent, should induce favorable pH conditions in soil, and/or interact with the incorporated heavy metals so that these heavy metals are removed from the soil [5]. Recently, researchers have been investigating whether this method can be used to remove subsurface contaminants, and they have compiled published research on the use of electrokinetic techniques to decontaminate fine-grained soil and have discussed some of the problems that occur during this process [6–8]. Meanwhile, researchers have also tried to develop soil flushing techniques in which soil-bound contaminants are transferred to a liquid phase by desorption and solubilization. Several flushing solutions have been investigated, such as water, acids, bases,
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Please cite this article in press as: G.-N. Kim, et al., Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method, Electrochim. Acta (2015), http://dx.doi.org/10.1016/j.electacta.2015.03.208
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chelating agents, alcohol, and other additives [9]. In practice, acid washing and chelator soil washing are the two most prevalent removal methods [10–11]. Recently, acetic acid or sodium dodecyl sulfate was used as an electrolyte for electrokinetic decontamination to increase the removal efficiency of metal [12–13]. In addition, most of the electrokinetic equipment has been manufactured as a horizontal type. Laboratory-scale electrokinetic decontamination has been performed for TRIGA soil during the past 5 years, but at this time, a study related to washing- electrokinetic decontamination was performed [14–15]. Jing-Yuan Wang (2007) started to develop vertical electrokinetic equipment to easily remove the contaminants accumulated at a cathode. The equipment has a cathode in the upper side so that the reagent in the soil cell might flow upward, and the contaminants in the soil cell might be accumulated in the upper side. Upward vertical electrokinetic equipment has already been used to remove heavy metal from kaolin [16] and to remove organic material from some of the soil [17]. Meanwhile, the electrodialytic method has generally been used for treating waste solution and soil remediation, which attaches an ion exchange membrane at the anode room or cathode room [18–21]. In this study, the soil contaminated with cesium was sampled at an area near a nuclear facility in Korea. The electrokinetic decontamination equipment and electrokinetic-elctrodialytic decontamination equipment were manufactured to decontaminate the contaminated soil. The difference between the removal efficiency according to the lapsed time by the electrokinetic decontamination equipment and the electrokinetic-elctrodialytic decontamination equipment was investigated through several experiments. The difference between the removal efficiency of the electrokinetic-elctrodialytic equipment without an anion exchange membrane and that with an anion exchange membrane was investigated through several experiments. In addition, the removal efficiency trend according to different cesium radioactivity of soil was drawn out through several experiments. 2. Materials and methods 2.1. Characteristics of contaminated soil The soil in a drum was contaminated with cesium in a drum, and Table 1 shows the cesium soil hydraulic properties. The saturation degree of the surface at a nuclear facility site is small, and the hydraulic conductivity of the soil is a little lower. The pH of the soil is a little acidic. 2.2. Manufacturing of electrokinetic decontamination equipment
Fig. 1. A schematic diagram of electrokinetic decontamination equipment.
4.5 5.9 14.5 cm for Experiment 1. As Experiment 1, a paper filter was inserted between the electrode compartment and the contaminated soil to prevent an influx of soil. A pump supplies a reagent to the reagent reservoir at 0.5–1 ml/min, and the reagent reservoir supplies a chemical solution to the anode room. The electric current between electrodes is 0.6A, and the electric voltage between electrodes is 4.5–5.2 V. The temperature in the cathode room was below 65 C. 0.5 M of HNO3 was used as electrolyte reagent to accelerate the desorption of cesium from soil on stirring soil. Experiments 1and 2 used a different soil sample radioactivity, and the electrokintic decontamination period was 21 days without exception. In Experiment 2, an anion exchange membrane was inserted between the anode room and the contaminated soil to prevent an influx of cesium ions, and a paper filter was inserted between the cathode room and the contaminated soil. 200 g of contaminated soil was placed into a horizontal soil cell, namely, the ratio of liquid (mg)/ soil (g) is 0.5. 2.3. Manufacturing of electrokinetic-electrodialytic decontamination equipment To increase the removal velocity of cesium from the soil, electrokinetic-electrodialytic decontamination equipment was manufactured. This equipment mixed the electrokinetic and electrodialytic concepts. Fig. 3 shows a schematic diagram of electrokinetic-electrodialytic decontamination. In this study, the
Electokinetic equipment decontamination was manufactured for the experiments. Fig. 1 shows a schematic diagram of the electrokinetic decontamination equipment, and Fig. 2 shows the manufactured electrokinetic decontamination equipment. The electrokinetic decontamination equipment consists of a horizontal soil cell, two electrode compartments (anode/cathode rooms), a reagent reservoir, an effluent reservoir, and a power supply, and 480 g of contaminated soil was placed into a horizontal soil cell of
Table 1 Hydraulic properties of cesium soil. Parameter
Value
Bulk density (g/cm3) Porosity (%) Hydraulic conductivity (cm/sec) Water content (%) pH
1.51 41.8 3.8 105 23.4 5.7 Fig. 2. Manufactured electrokinetic decontamination equipment.
Please cite this article in press as: G.-N. Kim, et al., Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method, Electrochim. Acta (2015), http://dx.doi.org/10.1016/j.electacta.2015.03.208
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cathode room and the contaminated soil. 200 g of contaminated soil was placed into a horizontal soil cell, namely, at a ratio of liquid (mg)/soil(g) of 0.5. 2.4. Radioactivity measurement for soil
Fig. 3. A schematic diagram of the electrokinetic-electrodialytic decontamination equipment.
electrokinetic-electrodialytic decontamination equipment was manufactured as shown in Fig. 4. An impellor was used in the electrokintic-electrodialytic decontamination experiments. The impellor was installed in the middle of the horizontal soil cell, and the rpm of the impellor was 60. A pump supplies a reagent to the reagent reservoir by 2–3 ml/min, and the reagent reservoir supplies a chemical solution to the anode room. The electric current between electrodes is 0.6A, and the electric voltage between electrodes is 4.5–5.2 V. The temperature in the cathode room was below 50 C. Experiments 3 and 4 used soil samples with a different radioactivity, and the electrokintic decontamination period was 21 days without exception. Also, 200 g of contaminated soil was placed into a horizontal soil cell, namely, at a ratio of liquid (mg)/soil (g) of 0.5. In Experiment 4, an anion exchange membrane was inserted between the anode room and the contaminated soil to prevent an influx of cesium ions, and a paper filter was inserted between the
The initial cesium concentration for the soil was measured using a Multi-Channel Analyzer (MCA) with a standard tube of 1,000 cc, QCY48 (Amersham), manufactured by the Korea Reach Institute Standards and Sciences. The MCA operates in a pulse height analyzer mode. The scintillation counter measures the pulse height distribution from a gamma ray source. The amplitude of an incoming analogue pulse is digitized by an analogue digital converter (ADC), and the digital value is used as the address of the incremented memory location. Thus, the screen display of the number of counts vs. the channel number is really a histogram of the number of counts vs. the pulse height, i.e., a pulse height spectrum. The time required to measure the radioactivity concentration of a gravel sample using the MCA was estimated to be 4–8 hours. The initial radioactivity concentration of the soil before electrokinetic-electrodialytic decontamination was calculated. The electrokinetic-electrodialytic experiment was stopped at pre-determined interim times, the soil samples were extracted from the soil cell, and the radioactivity concentration of the soil samples were then measured using the MCA. The soil samples were returned to their initial locations in the soil cell, and the experiment was continuously restarted. The removal efficiency of the nuclides was calculated as a ratio of the initial soil concentration, and the soil concentrations were measured at pre-determined interim times. After completion of the electrokinetic-electrodialytic decontamination experiments for radioactive soil with initial concentrations of 1.0–25 Bq/g, the residual concentration of soil was calculated. Finally, the decontamination period required for decontaminating the initial soil concentration to a clearance concentration level (137Cs:0.1 Bq/g) was estimated using the experimental electrokinetic-electrodialytic results. 3. Results and discussion 3.1. Electrokinetic decontamination results Cesium (137Cs+) in the contaminated soil in the electrokinetic decontamination was removed by electro-osmosis, electro-migration, and a hydraulic pressure flow, as in the following equation: j ¼ ½ðko þ km ÞRrI þ kh rpC
Fig. 4. Manufactured electrokinetic-electrodialytic decontamination equipment.
D
t2
rC
(1)
where j is the molar flux of the species per unit pore area, Ko is the electro-osmotic permeability, Km is the electro-migration coefficient, R is the electric resistance, I is the electric current, Kh is the hydraulic permeability, P is the pressure, C is the molar concentration, D is the diffusion coefficient, and t is a non-dimensional tortuosity. To remove cesium from the soil, electrokinetic decontamination equipment was manufactured. Table 2 shows the results of the removal efficiency according to the lapsed time by the electrokinetic decontamination as Experiment 1. When the decontamination period of 0.3 days, 2 days, and 7 days elapsed, 137Cs+ in the soil was removed by about 10%, 30%, and 60%. However, the removal efficiency of 137Cs+ was sharply reduced after 7 days, because the 137 Cs+ on the surface of the soil particles had almost been removed for 7 days. It is considered that the 137Cs+ located deeply in soil cannot be removed by the electromagnetic strength between cathode electrode and cesium ions, because the ion of cesium is one positive charge. Thus, when the decontamination period of
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Table 2 Removal efficiency according to the lapsed time by electrokinetic decontamination (Experiment 1).
Removal Eff. 1 Removal Eff. 2 Removal Eff. 3 Removal Eff. 4
Initial radioactivity concentration
0.3 2 7 10 14 21 (days) (days) (days) (days) (days) (days)
22.7 (Bq/g)
10.8%
33.7%
62.3%
64.3%
68.4%
73.3%
13.6 (Bq/g)
9.6%
32.4%
60.5%
63.7%
67.8%
71.7%
6.2 (Bq/g)
8.7%
30.2%
59.6%
63.4%
66.7%
70.4%
1.6 (Bq/g)
7.4%
29.5%
58.2%
62.5%
65.5%
69.4%
Table 4 Removal efficiency according to the lapsed time by electrokinetic-stirring decontamination without an anion exchange membrane (Experiment 3).
Removal Eff. 1 Removal Eff. 2 Removal Eff. 3
J¼ 10 days, 14 days, and 21 days elapsed, the 137Cs+ in the soil was removed by about 63%, 66%, and 71%. Meanwhile, the more the initial radioactivity concentration of soil increased, the more the removal efficiency of 137Cs+ from soil increased. It is considered that in case of the high radioactivity concentration of soil, the greater amount of 137Cs+ attached to the surface of the soil particles had been removed during same decontamination period. Table 3 shows the results of the removal efficiency according to the lapsed time by electrokinetic decontamination with an anion exchange membrane as Experiment 2. 200 g of contaminated soil occupied a lower part of a horizontal soil cell, and the electrolyte occupied an upper part of a horizontal soil cell. An anion exchange membrane was inserted between the anode room and the contaminated soil to prevent an influx of cesium ions in the electrolyte occupied an upper part of a horizontal soil cell. It is not necessary to install a cation-exchange membrane between the cathode room and the soil cell to prevent an influx of OH from the cathode room, because the pH of the electrolyte in the cathode room was below 1 due to a constant efflux of the electrolyte through the outlet of the cathode room. On the other hand, an anion exchange membrane was inserted between the anode room and the soil cell to prevent an influx of cesium ions from soil cell. If cesium ions flow into the anode room from the soil cell, the period for removing cesium from the soil cell will be prolonged due to the electrolyte mixed with cesium ions in the anode room. When the decontamination period of 0.3 days, 2 days, and 7 days elapsed, 137Cs+ in the soil was removed by about 9%, 30%, and 58%. Similarly, the removal efficiency of 137Cs+ was sharply reduced after 7 days. When the decontamination period of 10 days, 14 days, and 21 days elapsed, the 137Cs+ in soil was removed by about 62%, 64%, and 69%. The removal efficiencies of Experiment 1 and Experiment 2 were almost the same values. 3.2. Electrokinetic-stirring and electrokinetic-electrodialytic decontamination results Cesium (137Cs+) in the soil cell in the electrodalytic decontamination was removed on the basis of the following equation: Table 3 Removal efficiency according to the lapsed time by electrokinetic decontamination with an anion exchange membrane (Experiment 2).
Removal Eff. 1 Removal Eff. 2 Removal Eff. 3
Initial radioactivity concentration
0.3 2 7 10 14 21 (days) (days) (days) (days) (days) (days)
21.6 (Bq/g)
10.1%
32.5%
60.1%
62.7%
66.5%
71.4%
11.8 (Bq/g)
8.9%
30.2%
58.2%
62.1%
63.8%
69.3%
1.4 (Bq/g)
7.1%
27.4%
56.9%
60.3%
62.1%
67.2%
Initial radioactivity concentration
0.3 2 7 10 14 21 (days) (days) (days) (days) (days) (days)
23.4 (Bq/g)
11.2%
38.6%
71.5%
77.4%
80.2%
83.7%
15.6 (Bq/g)
10.5%
37.5%
68.9%
75.3%
78.3%
81.5%
1.5 (Bq/g)
7.9%
32.8%
65.8%
70.4%
74.6%
78.4%
h dI F dAM
where J is the molar flux, h is the current efficiency, F is the Faraday constant, and AM is the effective area of ion exchange membrane. Cesium is removed from soil by ion exchange through stirring with nitric acid solution in the soil cell. The action of cesium and nitric acid solution is expressed by the following equation: HNO3
CsX ! Csþ þ HX þ NO 3 where X represents the soil matrix. Cesium (137Cs+) in the contaminated soil in the electrokineticstirring decontamination equipment was removed by electro-osmosis, electro-migration, and ion exchange. The pH achieved in the soil cell on using 0.5 M of HNO3 as electrolyte was below 0.5, which accelerated the desorption of cesium ions from soil. The experimental electrokinetic- stirring conditions were as follows. Table 4 shows the results of the removal efficiency according to the lapsed time by electrokinetic-stirring decontamination without an anion exchange membrane as Experiment 3. When the decontamination period of 0.3 days, 2 days, and 7 days elapsed, 137Cs+ in the soil was removed by about 10%, 37%, and 68%. However, the removal efficiency of 137Cs+ was reduced after 7 days, because the 137Cs+ on the surface of the soil particle had almost been removed for 7 days. However, the removal efficiency of Experiment 3 was increased more than Experiments 1 and 2, because Experiment 3 used an impellor to increase the surface area of soil particles making contact with electrolyte in the horizontal soil cell. In addition, when the decontamination period of 10 days, 14 days, and 21 days elapsed, the 137Cs+ in soil was removed by about 75%, 78%, and 81%. The removal efficiency of Experiment 3 was increased more than Experiment 1 and 2 due to the impellor. Table 5 shows the results of the removal efficiency according to the lapsed time by electrokinetic-electrodialtic decontamination with an anion exchange membrane as Experiment 4. An anion exchange membrane was inserted between the anode room and the contaminated soil to prevent an influx of cesium ions in the electrolyte occupying an upper part of a horizontal soil cell. When the decontamination period of 0.3 days, 2 days, and 7 days elapsed, 137 Cs+ in the soil was removed by about 12%, 38%, and 83%. Table 5 Removal efficiency according to the lapsed time by electrokinetic-electrodialytic decontamination with an anion exchange membrane (Experiment 4).
Removal Eff. 1 Removal Eff. 2 Removal Eff. 3 Removal Eff. 4
Initial radioactivity concentration
0.3 2 7 10 14 21 (days) (days) (days) (days) (days) (days)
20.5 (Bq/g)
14.0%
40.7%
86.5%
92.3%
95.1%
12.4 (Bq/g)
12.7%
38.1%
83.9%
91.1%
93.5%
5.8 (Bq/g)
11.9%
36.7%
81.4%
87.5%
91.3%
1.7 (Bq/g)
11.1%
35.3%
79.5%
85.3%
89.2%
98.2% 0.37 97.2% 0.35 95.4% 0.27 94.1% 0.1
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However, the removal efficiency of 137Cs+ was reduced after 7 days, because the 137Cs+ on the surface of the soil particles had almost been removed for 7 days. The removal efficiency of Experiment 4 was increased more than that of Experiment 3 because Experiment 4 used the anion exchange membrane to prevent the contamination of 137Cs+ in the anode room. When the decontamination period of 10 days, 14 days, and 21 days elapsed, the 137Cs+ in soil was removed by about 91%, 93%, and 97%. Meanwhile, the more the initial radioactivity of soil decreased, the more the removal efficiency of 137Cs+ was reduced. The soil stirring accelerated the desorption of cesium ions from soil and an anion exchange membrane shortened the period for removing cesium from the soil cell by preventing the influx of cesium ions into the anode room. Conclusively, the removal efficiency of 137Cs+ from soil by electrokinetic-electrodialytic decontamination technology was higher than that of 137Cs+ from soil by electrokinetic decontamination technology. In addition, the anion exchange membrane in electrokinetic-electrodialytic decontamination increased the removal efficiency of 137Cs+ from soil due to the interception of an infiltration of 137Cs+ in the anode room. 4. Conclusions The removal efficiency of 137Cs+ from soil by electrokineticstirring decontamination technology was higher than that of 137Cs+ from soil by electrokinetic decontamination technology. In addition, the anion exchange membrane in electrokinetic-electrodialytic decontamination increased the removal efficiency of 137Cs+ from soil due to the interception of an infiltration of 137Cs+ in the anode room. Meanwhile, the more the initial radioactivity concentration of soil increased, the more the removal efficiency of 137Cs+ from soil increased. When the electrokinetic-electrodialytic decontamination period of 0.3–7.0 days elapsed, 137Cs+ in the soil was removed by about 12 - 83%. However, the removal efficiency of 137Cs+ was sharply reduced after 7 days because the 137 Cs+ on the surface of soil particles had almost been removed for 7 days. When the decontamination period of 10–21 days elapsed, the 137Cs+ in soil was removed by about 91–97%. The soil stirring
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accelerated the desorption of cesium ions from soil and an anion exchange membrane shortened the period for removing cesium from the soil cell. Acknowledgements This project was carried out under the Nuclear R&D Program by MOST in KOREA. References [1] G.N. Kim, W.K. Choi, C.H. Bung, J.K. Moon, J. Ind. Eng. Chem. 13 (2007) 406–413. [2] G.N. Kim, Y.H. Jung, J.J. Lee, J.K. Moon, Journal of the Korean Radioactive Waste Society 25 (2) (2008) 146–153. [3] K. Reddy, C.Y. Xu, S. Chinthamreddy, J. Hazard. Mater. B 84 (2001) 279–296. [4] S. Pamukcu, J.K. Wittle, Environ. Prog. 11 (3) (1992) 241–270. [5] K. Reddy, S. Chinthamreddy, J. Geotech. Geoenviron. Eng. (March) (2003) 263–277. [6] F. Braud, S. Tellier, M. Astruc, 68 (1998) 105–121. [7] S.O. Kim, S.H. Moon, K.W. Kim, Water Air and Soil Pollution 125 (2001) 259–272. [8] M.M. Page, C.L. Page, Journal of Environmental Engineering. ASCE 128 (2002) 208–219. [9] C. Chaiyaraksa, N. Sriwiriyanuphap, Chemosphere 546 (2004) 129–135. [10] C.G. Rampley, K.L. Ogden, Environ. Sci. Technol. 32 (7) (1988) 987–993. [11] B. Sun, F.J. Zhao, E. Lombi, S.P. McGrath, Environ Pollut. 113 (2001) 111–120. [12] B. Kornilovich, N. Mishchuk, K. Abbruzzese, G. Pshinko, R. Klishchenko, Colloids and Surfaces A: Physicochem. Eng. Aspects 265 (2005) 114–123. [13] A. Giannis, E. Gidarakos, A. Skouta, Desalination 211 (2007) 249–260. [14] G.N. Kim, Y.H. Jung, J.J. Lee, J.K. Moon, C.H. Jung, Separation and Purification Technology 63 (2008) 116–121. [15] G.N. Kim, W.Z. Oh, H.J. Won, W.K. Choi, J. Ind. Eng. Chem. 9 (3) (2003) 306–313. [16] J.Y. Wang, X.J. Huang, J.C.M. Kao, O. Stabnikova, Journal of Hazardous Materials B136 (2006) 532–541. [17] J.Y. Wang, X.J. Huang, J.C.M. Kao, O. Stabnikova, Journal of Hazardous Materials B144 (2007) 292–299. [18] T.R. Sun, L.M. Ottosen, P.E. Jensen, Pulse current enhanced electrodialytic soil remediation: Comparison of different pulse frequencies, J. Hazard. Mater. 237– 238 (2012) 299–306. [19] G.M. Nystrom, L.M. Ottossen, A. Villumsen, Test of experimental set-ups for electrodialytic removal of Cu Zn, Pb and Cd from different contaminated harbor sediments, Eng. Geol. 77 (2005) 349–357. [20] P.E. Jensen, L.M. Ottosen, B. Allard, Electro dialytic versus acid extraction of heavy metals from soil washing residue, Electrochim. Acta 86 (2012) 115–123. [21] M.R. Jakobsen, J. Fritt-Ramussen, S. Nielsen, L.M. Ottosen, Electrodialytic removal of cadmium from wastewater sludge, J. Hazard. Mater. 106 (2004) 127–132.
Please cite this article in press as: G.-N. Kim, et al., Decontamination of Soil Contaminated with Cesium using Electrokinetic-electrodialytic Method, Electrochim. Acta (2015), http://dx.doi.org/10.1016/j.electacta.2015.03.208