Rapid removal of radioactive cesium by polyacrylonitrile nanofibers containing Prussian blue

Accepted Manuscript Title: Rapid removal of radioactive cesium by polyacrylonitrile nanofibers containing Prussian blue Authors: Hyuncheol Kim, Minsun Kim, Wanno Lee, Soonhyun Kim PII: DOI: Reference:

S0304-3894(17)30950-0 https://doi.org/10.1016/j.jhazmat.2017.12.050 HAZMAT 19082

To appear in:

Journal of Hazardous Materials

Received date: Revised date: Accepted date:

28-7-2017 8-11-2017 19-12-2017

Please cite this article as: Kim H, Kim M, Lee W, Kim S, Rapid removal of radioactive cesium by polyacrylonitrile nanofibers containing Prussian blue, Journal of Hazardous Materials (2010), https://doi.org/10.1016/j.jhazmat.2017.12.050 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Rapid

removal

of

radioactive

cesium

by

SC RI PT

polyacrylonitrile nanofibers containing Prussian blue

U

Hyuncheol Kim1, Minsun Kim2, Wanno Lee1, and Soonhyun Kim2*

Nuclear Emergency and Environmental Protection Division, Korea Atomic Energy Research

N

1

Smart Textile Convergence Research Group, Daegu Gyeongbuk Institute of Science and

M

2

A

Institute (KAERI), Daejeon, 34057, Republic of Korea.

TE

Submitted to

D

Technology (DGIST), Daegu, 42988, Republic of Korea.

EP

Journal of Hazardous Materials

CC

(Revised)

A

November 2017

* Corresponding author (S. Kim) Tel: +82-53-785-3410; fax: +82-53-785-3439 E-mail address: [email protected]

1

N

U

SC RI PT

Graphical abstracts

A

Highlights

We synthesized Prussian blue incorporated polyacrylonitrile nanofiber (PB/PAN)



PB nanoparticles can be incorporated successfully into the PAN matrix



With simple filtering for the 137Cs removal, PB/PAN showed high removal efficiency



PB/PAN showed high 137Cs removal efficiency even in the actual seawater medium



PB/PAN can be practically applied for the Cs removal from radioactive wastewater

EP

TE

D

M



CC

Abstract

After the Fukushima Daiichi Nuclear Power Plant disaster in Japan in 2011, the demand

A

drastically increased for efficient technology for the removal of radioactive cesium. Prussian blue (PB) nanoparticles have shown excellent adsorption ability toward Cs. In this study, we synthesized PB nanoparticles incorporated polyacrylonitrile nanofiber (PB/PAN). PB/PAN has the porous structure of nanofibers, with diameters of several hundred nanometers. PB nanoparticles can be incorporated successfully into the PAN matrix without any change to

2

their intrinsic crystallinity and structure. The mesoporous structure of PB/PAN and the incorporation of PB nanoparticles led to an increase in the Brunauer–Emmett–Teller surface area and pore volume. In addition, PB/PAN exhibited excellent wettability with water. With

SC RI PT

simple filtering for the removal of radioactive cesium, PB/PAN showed high removal efficiency (87 ± 3%) within 10 seconds for 10 mL of 137Cs solution (1000 Bq L-1). In addition, the 137Cs removal by PB/PAN showed high removal efficiency (70 ± 2 %, after 1 h), even in the actual seawater medium (1000 Bq L-1 of

137

Cs). Therefore, PB-incorporated PAN

nanofibers can be considered useful in the practical application of Cs removal from

A

N

U

radioactive wastewater.

M

Keywords: Radioactivity; Cesium 137; Prussian blue; Polyacrylonitrile nanofibers;

TE

1. Introduction

D

Electrospinning

EP

The Fukushima Daiichi Nuclear Power Plant (FDNPP) was damaged extensively by an earthquake and tsunami on 11 March 2011. The disaster led to the release of highly toxic

CC

radionuclides into the environment. Several studies investigated the activity concentration of 137

Cs in seawater after the accident [1-3]. As

137

Cs was transported downward by vertical

A

water mixing, the 137Cs released into the ocean could be detected in the ocean surface and in the subsurface, which indicates it circulated over the entire ocean without artificial removal of it. Fukushima-derived radionuclides were observed even off the North American west coast [4]. After the accident, much effort was expended on controlling the release of the radioactive wastewater into the environment. However, the radioactive wastewater produced

3

from the treatment process in the FDNPP could not be controlled completely. This resulted in a significantly higher level of 137Cs compared with the levels before the Fukushima incident attributable to the ongoing release of 137Cs from the FDNPP [5, 6]. Because of its long half137

Cs is considered a highly toxic and harmful

SC RI PT

life (T1/2: ~ 30 y) and mimic of potassium,

nuclide. Accordingly, immense efforts have been made to develop an effective and easy technique to separate and recover 137Cs from contaminated water.

Prussian blue (PB) is a face-centered cubic-lattice, zeolite-like inorganic material that

U

can exchange its potassium ions for cesium ions [7, 8]. As the PB crystal has a lattice spacing

N

size similar to the hydration radius of the Cs ion, PB has shown excellent adsorption ability

A

toward Cs and has been utilized to assist Cs removal from the bodies of patients after the

M

Chernobyl disaster in Russia in 1986 [9-11]. Although PB can take up Cs effectively, the separation and recycling after adsorption remain an obstacle to practically applying the

D

material. Therefore, support materials, with high surface areas or magnetic properties have

TE

been applied to immobilize PB. As was reported by Yi et al., the core–shell structured magnetic microsphere was functionalized with potassium titanium ferrocyanide to effectively 137

EP

decontaminate

Cs [12]. Chen et al. first applied the PB-nanoparticles implemented non-

CC

woven fabric as an efficient adsorbent for Cs removal [13]. Wen et al. made a flexible freestanding sodium titanate nanobelt membrane as an efficient sorbent for the removal of 90Sr, Cs nuclides, and oils [14]. Jang et al. developed PB/reduced graphene oxide foam

A

137

composite materials for the efficient removal of 137Cs from contaminated water [15]. On the other hand, PB was also used in electrochemical switch ion-exchange applications, which were carried on electrically conductive carbon fibers, for the recovery of Cs ions as well as adsorption [16, 17].

4

Electrospinning is a versatile technique to produce continuous fibers with diameters ranging from a few nanometers to a few micrometers [18]. Electrospun nanofibrous materials have significant potential relevant to various emerging environmental applications, including

SC RI PT

the effective oil/water, as electrospinning is a simple process and the electrospun nanofiber can be controlled [19, 20]. Accordingly, increasing attention is being paid to the functional materials incorporated composite nanofibers in various fields. Previously, Bang et al. have prepared PB-incorporated polyvinyl alcohol (PVA) nanofibers for the adsorption of Cs from radioactive wastewater [21]. This material showed excellent and faster Cs adsorption.

N

U

However, PVA is highly soluble in water; therefore, post treatment should be carried out.

A

On the other hand, polyacrylonitrile-based nanofibers have been used widely in

M

filtration and reverse osmosis membranes because of their high chemical resistance, thermal stability, and excellent wettability with water [22]. Recently, PAN composite nanofibers were

D

made, consisting of nanoscale inorganic fillers, such as Fe-montmorillonite and halloysite

TE

nanotubes, and a PAN matrix to improve the mechanical and thermal properties [23, 24]. PB

EP

also coated on the surface of PAN-based carbon fiber by electrodeposition and used as a catalyst in catalytic graphitization [25]. Moreover, PB nanolayer on PAN membranes was in-

CC

situ prepared and PAN based PB nanofibers were also demonstrated for Cs removal in water [26, 27]. Previously, we made a TiO2-incorporated PAN nanofiber during the preparation of

A

a TiO2-incorporated carbon nanofiber mat and TiO2 nanofibers [28, 29]. Nano-sized TiO2 powder was homogeneously dispersed in a PAN solution and TiO2-containing PAN nanofiber webs were well obtained.

5

In this study, we synthesized PB-incorporated PAN nanofibers (PB/PAN) for the efficient removal of

137

Cs from radioactive wastewater. The physicochemical properties of

SC RI PT

the prepared PB/PAN were measured and their Cs removal activities were investigated.

2. Experimental Details 2.1. Preparing of PB/PAN

The PB/PAN was prepared by using electrospinning [28, 29]. A 10 wt% PAN solution

U

was prepared by dissolving PAN (Mw = 150000, Sigma-Aldrich) in N,N-dimethylformamide

N

(DMF, 99%, Sigma-Aldrich), heating the mixture at 85 °C while stirring for 4 h, followed by

A

cooling to room temperature, and stirring for another 12 h. A viscous yellow-brown solution

M

was obtained in this way. Subsequently, 5 or 10 wt% of PB powder (based on the wt% of the

D

PAN solution, Sigma-Aldrich) was added to the PAN solution and stirred vigorously for 12 h.

TE

The PB/PAN was prepared by electrospinning, with the PB containing the PAN solution being fed at a constant rate of 20 μL/min. An electric field of 20 kV was applied, with a distance of

EP

15 cm between the needle and the collector plate. The PB/PAN nanofiber webs were obtained at the collector. In the rest of the text, the prepared samples are denoted as PB(wt%)/PAN,

CC

according to the wt% of the PB powder to the PAN solution.

A

2.2. Characterization of PB/PAN The surface morphology images were obtained by using a field emission scanning

electron microscope (FE-SEM, Hitachi S4-8020, Japan). The transmission electron micrographs were obtained from a high-resolution transmission electron microscope (HRTEM, Hitachi HF-3300, Japan). The X-ray diffraction (XRD) patterns were obtained with an

6

X-ray diffractometer (Panalytical, Empyrean, 40 kV, 30 mA), using Cu-Kα1 radiation (λ = 1.54178 Å) and a quartz monochromator. Fourier transformation infrared spectroscopy (FTIR) (Continuum, Thermo Scientific) was conducted to identify the chemical interactions

SC RI PT

occurring inside the PB/PAN. The background and sample spectra were obtained over the frequency range 4000–600 cm−1, with 32 scans per specimen at a resolution of 0.4 cm−1. The Brunauer-Emmett-Teller (BET) surface areas were determined from the nitrogen adsorptiondesorption isotherms at 77 K (ASAP 2020 Micromeritics). The effective surface areas were estimated at a relative pressure (P/P0) ranging from 0.01 to 0.1. The pore size distribution

U

was computed by applying the Barrett-Joyner-Halenda (BJH) method in a relative pressure

A

M

GONIOSTAR (Surface Technology).

N

(P/P0) range of 0.01 to 0.995. The water contact angles were measured by using

TE

D

2.3. Cs ion adsorption measurement The Cs ion adsorption experiment was performed with 20 mL of desired amount of

EP

CsCl solution. 0.1 g of PB(10)/PAN was added to the solution, which was subsequently kept in the dark to allow adsorption of the Cs ion. After adsorption, the sample aliquots were

CC

intermittently withdrawn by a 1-ml syringe and filtered through a 0.45 m PTFE filter (Millipore). The Cs ion concentration was monitored using ion chromatography (IC,

A

DIONEX ICS-3000 series). The effects of pH were conducted in 400 M of Cs+ with pH values of 3, 6, 9 adjusted by 0.1 mM of HCl or NaOH solution). 2.4. Removal of 137Cs We prepared a solution of 1000 Bq L-1 of

137

Cs by diluting

137

Cs stock solution,

7

obtained from Eckert & Ziegler, with de-ionized water (MilliQ-Plus, 18 ΩM). To compare the removal of 137Cs between PAN and PB(10)/PAN, 40 mg of PAN and PB(10)/PAN were placed in a filter holder connected to a syringe containing 10 mL of 137Cs solution. The sample

SC RI PT

solution was passed through the PAN and PB(10)/PAN, respectively, at less than 10 seconds. To determine 137Cs, 5 mL of the filtered solution was placed in a 20 mL plastic vial and mixed with 5 mL of scintillation cocktail (Ultima Gold AB, Perkin Elmer). The activity concentration of 137Cs was measured by LSC (liquid scintillation counting, Quantulus 1220,

U

Perkin Elmer).

𝐴𝑡 × 100 𝐴0

M

A

A = 100 −

N

The removal of 137Cs (A) was calculated with the following equation:

D

where A0 and At are the activity concentrations of 137Cs before and the after test, respectively. 137

Cs was tested with 40 mg of PB(5)/PAN and

TE

The time-dependent removal of

PB(10)/PAN, which were soaked (without shaking) in 10 mL of

137

Cs solution at room

EP

temperature. The sample solution was left to stand for 5, 10, and 60 min, and 24 h.

CC

Subsequently, the test solution was filtered through a syringe filter (0.22 m). The removal of 137Cs was analyzed by the above-mentioned method.

A

2.4. Removal of 137Cs from seawater The removal of 137Cs by PB-incorporated PAN nanofibers was examined in seawater

containing 1000 Bq L-1 of

137

Cs. Seawater samples were collected from the East Sea, with

35 ‰ salinity, 7.2 ± 0.3 (average ± standard deviation [SD]) ppm of Sr, 1150 ± 13 ppm (1 SD) of Mg, and 395 ± 8 (1 SD) ppm of Ca. We soaked 40 mg of PB(5)/PAN and PB(10)/PAN in

8

10 mL of 137Cs-contaminated seawater for 1 h, after which it was filtered through a syringe filter (0.22 m). The solution was analyzed by LSC to determine the removal rate of 137Cs, based on the above-mentioned method. The concentrations of cations were analyzed by

SC RI PT

inductively coupled plasma optical emission spectrometry (ICP-OES, Varian) before and after the treatment.

3. Results and Discussion

U

3.1. Characterization of PB/PAN

N

The morphology of PAN, PB(5)/PAN, and PB(10)/PAN is shown in Fig. 1. The

A

obtained nanofibers were randomly distributed to form the fibrous web, the diameters of

M

which were several hundred nanometers. It was observed clearly that the PAN nanofiber

D

exhibited an ultrafine and uniform structure, whereas the PB(5)/PAN and the PB(10)/PAN

TE

exhibited a partly nonhomogeneous fibrous structure. Although the addition of PB nanoparticles had a slight effect on the uniformity of the fibrous structure, we did not detect

EP

PB aggregates resulting from the poor dispersion of PB in the PAN solution. Magnified SEM images of the PAN (Fig. 1b) indicated that the surface of the PAN has a porous and rough

CC

structure. The porous structure on the surface of the fibers is attributed to the phase separation

A

resulting from the rapid evaporation of solvent during electrospinning. As regards the PB(5)/PAN and the PB(10)/PAN (Figs 1d and 1f), several bright, white, spherical particles can be seen on the surface, which could be PB nanoparticles. The PB nanoparticles with diameters of 20–60 nm are distributed well rather than aggregated in the PAN nanofiber, as shown in the TEM images (Fig. 2). The SAED pattern of PB(10)/PAN (Fig. 2i) was compared

9

with that of PAN (Fig. 2c), indicating the existence of PB nanoparticles. It is shown clearly that the PB nanoparticles are homogeneously dispersed in the PAN solution and agglomeration of PB nanoparticles did not occur in the obtained electrospun PB/PAN. As the

SC RI PT

PB/PAN is not soluble in water at all, the obtained PB/PAN can be used as electrospun material without any further treatment.

The XRD patterns of PAN, PB(5)/PAN, and PB(10)/PAN are shown in Fig. 3a. The PAN nanofibers exhibited two peaks, a strong diffraction peak centered at 16.8° and a weak

U

diffusion diffraction peak centered at 27.9°, which is consistent with previously reported

N

results [28, 30]. As regards PB(5)/PAN and PB(10)/PAN, sharp diffraction peaks were

A

observed at 17.4, 24.7, 35.3, and 39.5°. These can be assigned to the (200), (220), (400), and

M

(42) planes of face-centered cubic-lattice PB particles (JCPDS 73-0687) [31]. The intensities of the diffraction peaks were drastically increased with an increasing addition of PB. Fig. 3b

D

shows the FT-IR spectra of PAN, PB(5)/PAN, and PB(10)/PAN. The peak at 2088 cm-1 is

TE

attributed to the stretching vibration of -C≡N, which is a characteristic peak of PB [32]. The

EP

position of the peak was not changed at all. From the XRD and FT-IR results, we can confirm that PB nanoparticles were successfully incorporated into the PAN matrix without any change

CC

to the intrinsic properties of these PB nanoparticles. In Fig. 4a, N2 adsorption-desorption isotherms of PAN, PB(5)/PAN, and PB(10)/PAN

A

are shown. The PB-incorporated PAN nanofibers exhibited type IV isotherms with type H3 hysteresis, which is a characteristic of a mesoporous structure. It can be seen that PB(10)/PAN has a higher volume adsorbed compared with PB(5)/PAN, which was attributed to an increase in the mesopore content of the fibers by increasing the amount of PB nanoparticles. The pore-

10

size distribution curves of PAN, PB(5)/PAN, and PB(10)/PAN are shown in Fig. 4b. Pore volume was not observed at all in PAN, whereas PB(5)/PAN and PB(10)/PAN have significant amounts of pores. The pores are distributed mainly within a broad peak, ranging

SC RI PT

from 10 to 50 nm, and they increase drastically with an increase in the amount of PB nanoparticles. The BET surface areas of PAN, PB(5)/PAN, and PB(10)/PAN were 7.7 m2/g, 19.8 m2/g, and 28.7 m2/g, respectively. The BET surface area and pore volume increased with the increasing amount of PB nanoparticles, which can be attributed to an increase in the

U

internal porosity and surface roughness because of the presence of the PB nanoparticles.

N

To investigate the hydrophilic nature, the wettability of PAN, PB(5)/PAN, and

A

PB(10)/PAN was studied by measuring the water contact angle. The photographs of the

M

measurement of the water contact angle are shown in Fig. 5. The surface of the PBincorporated PAN nanofibers showed a lower water contact angle (65° and 43° for

D

PB(5)/PAN and PB(10)/PAN, respectively) compared with that of the pure PAN nanofibers

TE

(98°). This obviously indicates that the addition of PB nanoparticles increased the hydrophilic

EP

nature of the PAN nanofiber. The wettability should be related to the hydrophilic nature and, especially, to the structural porosity.

CC

3.2. Cs ion adsorption on PB/PAN

A

The adsorption capacity of PB/PAN for Cs ion was investigated and the results are

shown in Fig. 6. Figure 6a shows that the adsorption of Cs ion on PB/PAN was influenced by solution pH. At low pH, the adsorption of Cs ion was slightly decreased. This might be due to the electrostatic interaction between PB nanoparticles and cationic Cs ions. Figure 6b shows the time-dependent concentration of Cs ions on PB/PAN. The adsorption of Cs ions

11

increased rapidly and reached to equilibrium. The adsorption of isotherm of PB/PAN were determined in various concentration of Cs ion solution (0.05, 0.1, 0.2, 0.4, 1, 2 mM). Figure 6c shows that the adsorption capacity increased with increasing equilibrium concentration of

SC RI PT

Cs+. The maximum adsorption capacity was 0.75 mmol g-1. This is in consistent with that of PB nano-layer on PAN membranes and PB or PB powder [26]. This result indicates that the incorporated PB nanoparticles did not decrease the adsorption capacity. 3.3. Removal of 137Cs by PB/PAN 137

Cs by the PB-incorporated PAN nanofibers was

U

The removal efficiency of

N

investigated by varying the contact time. First, filtering experiments were carried out, as 137

A

shown in Fig. 7. A solution of 1000 Bq L-1 of

Cs was passed through the syringe filter 137

PB(10)/PAN exhibited extremely fast adsorption of

137

Cs solution per 10 seconds. The

Cs. The PB(10)/PAN showed high

D

M

holder with PB(10)/PAN, at a rate of 10 mL of

TE

removal efficiency (87 ± 3%), whereas PAN only adsorbed 5 ± 3% of 137Cs. The result shows that the PB-incorporated PAN nanofiber could remove the 137Cs easily by simple filtering.

EP

The time-dependent 137

Cs removal according to the PB loading is shown in Fig. 8.

Cs increases with increasing reaction time and reaches equilibrium after

CC

The removal of

137

1 h. The PB(10)/PAN exhibited less than 90%

137

Cs removal when the contact time was

A

within 10 min, and it was approximately 97% after 1 h, similar to 24 h contact time. Moreover, as the PB loading increased, the PB-incorporated PAN nanofibers showed improved removal efficiency at a contact time of 5 min. However, the performance after 1h was the same. This could be ascribed to the adsorption capacity of PB(5)/PAN, which could adsorb

137

Cs

sufficiently in this experimental condition.

12

3.3. Removal of 137Cs from seawater 137

Cs in a real seawater

SC RI PT

The PB-incorporated PAN was applied for the removal of

medium, for which 137Cs-spiked seawater was used. In this experiment, the removal of 137Cs occurred in the presence of PB(5)/PAN and PB(10)/PAN. As shown in Fig. 9, the removal of 137

Cs from seawater by PB-incorporated PAN was less than that from distilled water.

U

Nevertheless, PB(10)/PAN showed high removal efficiency (69.8 ± 2.2 % after 1 h).

To investigate the effect of several competitive cations, the concentrations of cations

N

such as Ca2+, Mg2+, and Sr2+ were monitored before and after the reaction. As shown in

A

Table 1, these concentrations did not change at all. This implies that the cationic species Ca2+,

M

Mg2+, and Sr2+ did not act competitively. Therefore, the increase in ionic strength could

TE

the PB and the 137Cs.

D

decrease the adsorption capacity by reducing the electrostatic forces between the surfaces of

EP

As described above, the PB-incorporated PAN can efficiently adsorb the radioactive Cs. A simple schematic diagram is shown in Fig. 10. As shown, radioactive

137

Cs can

CC

penetrate into mesoporous PAN nanofibers and be rapidly adsorbed in PB particles. It has been commonly accepted that the exclusive abilities of PB nanoparticles to adsorb hydrated

A

Cs ions are caused by regular lattice spaces surrounded by cyanido-bridged metal [33].

13

4. Conclusions We successfully created PB nanoparticle-incorporated PAN nanofiber. To evaluate the dispersion of PB nanoparticles in PAN nanofibers and the effect of PB on the removal of

SC RI PT

radioactive Cs, their morphology, physicochemical properties, and adsorption performances were investigated. Morphological analysis revealed the porous structure of nanofibers, with diameters of several hundred nanometers. Analyses with XRD and FTIR confirmed that the PB nanoparticles were successfully incorporated into the PAN matrix without changing their

U

intrinsic crystallinity and structure. Surface area analysis showed the mesoporous structure

N

of PB/PAN, and the incorporation of PB nanoparticles led to an increase in the BET surface

A

area and pore volume. The results of the water contact angle measurements revealed that the

M

addition of PB nanoparticles enhanced the wettability of the PAN nanofibers, with PB(10)/PAN exhibiting excellent wettability with water. As regards the removal of 137Cs,

D

PB(10)/PAN showed high removal efficiency (87 ± 3%) within 10 seconds for 10 mL of 137Cs

TE

solution (1000 Bq L-1) by simple filtering. In addition, the removal of 137Cs by PB(10)/PAN showed high efficiency (69.8 ± 2.2 % after 1 h), even in a real seawater medium. In conclusion,

EP

PB-incorporated PAN nanofibers can be considered useful in the practical application of Cs

CC

removal from radioactive wastewater. This is because PB/PAN can absorb the radioactive Cs rapidly from wastewater and it can be used directly without further preparation or purification.

A

Acknowledgments This work was supported by the DGIST R&D Program of the Ministry of Science, ICT & Future Planning (17-NT-02 and 17-BT-02). This work was also supported by Basic Science Research Program, through the National Research Foundation of Korea (NRF),

14

funded by the Ministry of Science, ICT & Future Planning (2017R1A2B4003919). This work was also supported by the KAERI R&D Program of the Ministry of Science, ICT &

A

CC

EP

TE

D

M

A

N

U

SC RI PT

Future Planning of Korea (522220-17).

15

References [1] M. Aoyama, K. Hirose, Artificial radionuclides database in the Pacific Ocean: HAM

SC RI PT

database, Sci. World J., 4 (2004) 200-215. [2] M.C. Honda, T. Aono, M. Aoyama, Y. Hamajima, H. Kawakami, M. Kitamura, Y. Masumoto, Y. Miyazawa, M. Takigawa, T. Saino, Dispersion of artificial caesium-134 and 137 in the western North Pacific one month after the Fukushima accident, Geochem. J., 46 (2012) e1-e9.

U

[3] K.O. Buesseler, S.R. Jayne, N.S. Fisher, I.I. Rypina, H. Baumann, Z. Baumann, C.F.

N

Breier, E.M. Douglass, J. George, A.M. Macdonald, H. Miyamoto, J. Nishikawa, S.M. Pike,

A

S. Yoshida, Fukushima-derived radionuclides in the ocean and biota off Japan, Proc. Natl.

M

Acad. Sci. U. S. A., 109 (2012) 5984-5988.

[4] J.N. Smith, R.M. Brown, W.J. Williams, M. Robert, R. Nelson, S.B. Moran, Arrival of

D

the Fukushima radioactivity plume in North American continental waters, Proc. Natl. Acad.

TE

Sci. U. S. A., 112 (2015) 1310-1315.

EP

[5] M. Castrillejo, N. Casacuberta, C.F. Breier, S.M. Pike, P. Masqué, K.O. Buesseler, Reassessment of 90Sr, 137Cs, and 134Cs in the Coast off Japan Derived from the Fukushima

CC

Dai-ichi Nuclear Accident, Environ. Sci. Technol., 50 (2016) 173-180. [6] M. Aoyama, Y. Hamajima, M. Hult, M. Uematsu, E. Oka, D. Tsumune, Y. Kumamoto,

A

134Cs and 137Cs in the North Pacific Ocean derived from the March 2011 TEPCO Fukushima Dai-ichi Nuclear Power Plant accident, Japan. Part one: surface pathway and vertical distributions, J. Oceanogr., 72 (2016) 53-65.

16

[7] J.F. Keggin, F.D. Miles, Structures and Formulæ of the Prussian Blues and Related Compounds, Nature, 137 (1936) 577-578. [8] W. Jin, A. Toutianoush, M. Pyrasch, J. Schnepf, H. Gottschalk, W. Rammensee, B. Tieke,

SC RI PT

Self-Assembled Films of Prussian Blue and Analogues:  Structure and Morphology, Elemental Composition, Film Growth, and Nanosieving of Ions, J. Phys. Chem. B, 107 (2003) 12062-12070.

[9] P.A. Haas, A Review of Information on Ferrocyanide Solids for Removal of Cesium from Solutions, Sep. Sci. Technol., 28 (1993) 2479-2506.

U

[10] C. Delchet, A. Tokarev, X. Dumail, G. Toquer, Y. Barre, Y. Guari, C. Guerin, J.

N

Larionova, A. Grandjean, Extraction of radioactive cesium using innovative functionalized

A

porous materials, RSC Advances, 2 (2012) 5707-5716.

M

[11] B. Kong, J. Tang, Z. Wu, J. Wei, H. Wu, Y. Wang, G. Zheng, D. Zhao, Ultralight

D

Mesoporous Magnetic Frameworks by Interfacial Assembly of Prussian Blue Nanocubes,

TE

Angew. Chem. Int. Ed., 53 (2014) 2888-2892. [12] R. Yi, G. Ye, F. Wu, M. Wen, X. Feng, J. Chen, Highly efficient removal of

137

Cs in

EP

seawater by potassium titanium ferrocyanide functionalized magnetic microspheres with multilayer core-shell structure, RSC Advances, 4 (2014) 37600-37608.

CC

[13] G.-R. Chen, Y.-R. Chang, X. Liu, T. Kawamoto, H. Tanaka, D. Parajuli, M.-L. Chen,

A

Y.-K. Lo, Z. Lei, D.-J. Lee, Prussian blue non-woven filter for cesium removal from drinking water, Sep. Purif. Technol., 153 (2015) 37-42. [14] T. Wen, Z. Zhao, C. Shen, J. Li, X. Tan, A. Zeb, X. Wang, A.-W. Xu, Multifunctional flexible free-standing titanate nanobelt membranes as efficient sorbents for the removal of radioactive 90Sr2+ and 137Cs+ ions and oils, Sci. Rep., 6 (2016) 20920.

17

[15] S.-C. Jang, Y. Haldorai, G.-W. Lee, S.-K. Hwang, Y.-K. Han, C. Roh, Y.S. Huh, Porous three-dimensional graphene foam/Prussian blue composite for efficient removal of radioactive 137Cs, Sci. Rep., 5 (2015) 17510.

SC RI PT

[16] J.-Y. Su, G.-P. Jin, T. Chen, X.-D. Liu, C.-N. Chen, J.-J. Tian, The characterization and application of prussian blue at graphene coated carbon fibers in a separated adsorption and electrically switched ion exchange desorption processes of cesium, Electrochim. Acta, 230 (2017) 399-406.

[17] S. Karnjanakom, Y. Ma, G. Guan, P. Phanthong, X. Hao, X. Du, C. Samart, A. Abudula,

U

Fabrication of nickel hexacyanoferrate film on carbon fibers by unipolar pulse

A

Electrochim. Acta, 139 (2014) 36-41.

N

electrodeposition method for electrochemically switched ion exchange application,

M

[18] D. Li, Y.N. Xia, Electrospinning of nanofibers: Reinventing the wheel?, Adv. Mater., 16

D

(2004) 1151-1170.

TE

[19] H. Zhu, S. Qiu, W. Jiang, D. Wu, C. Zhang, Evaluation of Electrospun Polyvinyl Chloride/Polystyrene Fibers As Sorbent Materials for Oil Spill Cleanup, Environ. Sci.

EP

Technol., 45 (2011) 4527-4531. [20] P. Zhang, R. Tian, R. Lv, B. Na, Q. Liu, Water-permeable polylactide blend membranes

CC

for hydrophilicity-based separation, Chem. Eng. J., 269 (2015) 180-185.

A

[21] H. Bang, K. Watanabe, R. Nakashima, W. Kai, K.-H. Song, J.S. Lee, M. Gopiraman, I.S. Kim, A highly hydrophilic water-insoluble nanofiber composite as an efficient and easilyhandleable adsorbent for the rapid adsorption of cesium from radioactive wastewater, RSC Advances, 4 (2014) 59571-59578.

18

[22] O. Masson, A. Baeza, J. Bieringer, K. Brudecki, S. Bucci, M. Cappai, F.P. Carvalho, O. Connan, C. Cosma, A. Dalheimer, D. Didier, G. Depuydt, L.E. De Geer, A. De Vismes, L. Gini, F. Groppi, K. Gudnason, R. Gurriaran, D. Hainz, Ó. Halldórsson, D. Hammond, O.

SC RI PT

Hanley, K. Holeý, Z. Homoki, A. Ioannidou, K. Isajenko, M. Jankovic, C. Katzlberger, M. Kettunen, R. Kierepko, R. Kontro, P.J.M. Kwakman, M. Lecomte, L. Leon Vintro, A.P. Leppänen, B. Lind, G. Lujaniene, P. Mc Ginnity, C.M. Mahon, H. Malá, S. Manenti, M. Manolopoulou, A. Mattila, A. Mauring, J.W. Mietelski, B. Møller, S.P. Nielsen, J. Nikolic, R.M.W. Overwater, S.E. Pálsson, C. Papastefanou, I. Penev, M.K. Pham, P.P. Povinec, H.

U

Ramebäck, M.C. Reis, W. Ringer, A. Rodriguez, P. Rulík, P.R.J. Saey, V. Samsonov, C.

N

Schlosser, G. Sgorbati, B.V. Silobritiene, C. Söderström, R. Sogni, L. Solier, M. Sonck, G.

A

Steinhauser, T. Steinkopff, P. Steinmann, S. Stoulos, I. Sýkora, D. Todorovic, N.

M

Tooloutalaie, L. Tositti, J. Tschiersch, A. Ugron, E. Vagena, A. Vargas, H. Wershofen, O.

D

Zhukova, Tracking of airborne radionuclides from the damaged Fukushima Dai-Ichi nuclear

TE

reactors by European Networks, Environ. Sci. Technol., 45 (2011) 7670-7677. [23] M. Makaremi, R.T. De Silva, P. Pasbakhsh, Electrospun Nanofibrous Membranes of

EP

Polyacrylonitrile/Halloysite with Superior Water Filtration Ability, J. Phys. Chem. C, 119 (2015) 7949-7958.

CC

[24] H. Qiao, Y. Cai, F. Chen, Q. Wei, F. Weng, F. Huang, L. Song, Y. Hu, W. Gao,

A

Influences of organic-modified Fe-montmorillonite on structure, morphology and properties of polyacrylonitrile nanocomposite fibers, Fiber Polym, 10 (2009) 750-755. [25] Q.-l. Peng, H.-h. Zhou, Z.-h. Huang, J.-h. Chen, Y.-f. Kuang, Catalytic graphitization of polyacrylonitrile-based carbon fibers coated with Prussian blue, J. Cent. South Univ. Technol., 17 (2010) 683-687.

19

[26] Z. Jia, X. Cheng, Y. Guo, L. Tu, In-situ preparation of iron(III) hexacyanoferrate nanolayer on polyacrylonitrile membranes for cesium adsorption from aqueous solutions, Chem. Eng. J., 325 (2017) 513-520.

SC RI PT

[27] K.-H. Park, D.-Y. Choi, J.-H. Park, C. Kim, T.-Y. Kim, J.-W. Lee, Characterization and Application of Electrospun Prussian Blue Nanofibers Synthesized by Electrospinning Polyacrylonitrile Solution, Int. J. Electrochem. Sci., 11 (2016) 1472-1481.

[28] S. Kim, S.K. Lim, Preparation of TiO2-embedded carbon nanofibers and their photocatalytic activity in the oxidation of gaseous acetaldehyde, Appl. Catal. B: Environ., 84

U

(2008) 16-20.

N

[29] S.K. Choi, S. Kim, S.K. Lim, H. Park, Photocatalytic comparison of TiO2 nanoparticles

A

and electrospun TiO2 nanofibers: Effects of mesoporosity and interparticle charge transfer, J.

M

Phys. Chem. C, 114 (2010) 16475-16480.

D

[30] T. Xu, F. Wu, Y. Gu, Y. Chen, J. Cai, W. Lu, H. Hu, Z. Zhu, W. Chen, Visible-light

TE

responsive electrospun nanofibers based on polyacrylonitrile-dispersed graphitic carbon nitride, RSC Advances, 5 (2015) 86505-86512.

EP

[31] L. Chang, S. Chang, W. Chen, W. Han, Z. Li, Z. Zhang, Y. Dai, D. Chen, Facile one-pot synthesis of magnetic Prussian blue core/shell nanoparticles for radioactive cesium removal,

CC

RSC Advances, 6 (2016) 96223-96228.

A

[32] M. Hu, S. Furukawa, R. Ohtani, H. Sukegawa, Y. Nemoto, J. Reboul, S. Kitagawa, Y. Yamauchi, Synthesis of Prussian Blue Nanoparticles with a Hollow Interior by Controlled Chemical Etching, Angew. Chem. Int. Ed., 124 (2012) 1008-1012. [33] M. Ishizaki, S. Akiba, A. Ohtani, Y. Hoshi, K. Ono, M. Matsuba, T. Togashi, K. Kananizuka, M. Sakamoto, A. Takahashi, T. Kawamoto, H. Tanaka, M. Watanabe, M.

20

Arisaka, T. Nankawa, M. Kurihara, Proton-exchange mechanism of specific Cs+ adsorption via lattice defect sites of Prussian blue filled with coordination and crystallization water

A

CC

EP

TE

D

M

A

N

U

SC RI PT

molecules, Dalton Trans., 42 (2013) 16049-16055.

21

Figure Captions Figure 1. SEM images of (a, b) PAN, (c, d) PB(5)/PAN, and (e, f) PB(10)/PAN.

SC RI PT

Figure 2. HR-TEM images of (a, b) PAN, (d, e, f) PB(5)/PAN, and (g, h) PB(10)/PAN, and the SAED patterns of (c) PAN and (i) PB(10)/PAN.

Figure 3. (a) XRD patterns of PAN, PB(5)/PAN, and PB(10)/PAN. (b) FT-IR spectra of PAN, PB(5)/PAN, and PB(10)/PAN.

U

Figure 4. (a) N2 adsorption-desorption isotherms of PAN, PB(5)/PAN, and PB(10)/PAN. (b)

N

Pore-size distribution curves of PAN, PB(5)/PAN, and PB(10)/PAN.

A

Figure 5. Photos showing the water contact angles of (a, b) PAN, (c, d) PB(5)/PAN, and (e,

M

f) PB(10)/PAN.

D

Figure 6. Adsorption of Cs ions by PB(10)/PAN. (a) Effects of pH on adsorption capacity of

TE

Cs ions. (b) Time-dependent adsorption of Cs ion. (c)Adsorption isotherm of Cs ion. 137

Cs by PAN and PB(10)/PAN by filtering, and the diagram of the

EP

Figure 7. Removal of

CC

filtration.

Figure 8. Time-dependent 137Cs removal by PB(5)/PAN and PB(10)/PAN.

A

Figure 9. Removal of

137

Cs by PB(5)/PAN and PB(1)/PAN from distilled water and real

seawater medium for 1 h. Figure 10. Simple illustration of Cs adsorption on PB nanoparticles in PB/PAN.

22

Fig. 1

23

D

TE

EP

CC

A

SC RI PT

U

N

A

M

Fig. 2

24

D

TE

EP

CC

A

SC RI PT

U

N

A

M

Fig. 3

25

D

TE

EP

CC

A

SC RI PT

U

N

A

M

Fig. 4

26

D

TE

EP

CC

A

SC RI PT

U

N

A

M

Fig. 5

27

D

TE

EP

CC

A

SC RI PT

U

N

A

M

Fig. 6

28

D

TE

EP

CC

A

SC RI PT

U

N

A

M

D

TE

EP

CC

A

SC RI PT

U

N

A

M

Fig. 7

29

D

TE

EP

CC

A Fig. 8

30

SC RI PT

U

N

A

M

D

TE

EP

CC

A Fig. 9

31

SC RI PT

U

N

A

M

D

TE

EP

CC

A

SC RI PT

U

N

A

M

Fig. 10

32

Table 1. The concentrations of Ca2+, Mg2+, and Sr2+ Mg2+ (mg/L)

Sr2+ (mg/L)

Before

395 ± 8

1150 ± 13

7.2 ± 0.3

After

390 ± 5

1154 ± 11

7.1 ± 0.2

A

CC

EP

TE

D

M

A

N

U

SC RI PT

Ca2+ (mg/L)

33