Effective removal of cesium from wastewater via adsorptive filtration with potassium copper hexacyanoferrate-immobilized and polyethyleneimine-grafted graphene oxide

Chemosphere 250 (2020) 126262

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Effective removal of cesium from wastewater via adsorptive filtration with potassium copper hexacyanoferrate-immobilized and polyethyleneimine-grafted graphene oxide Yonghwan Kim a, Ho Hyeon Eom a, Yun Kon Kim a, David Harbottle b, Jae W. Lee a, * a b

Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, United Kingdom

h i g h l i g h t s

g r a p h i c a l a b s t r a c t


KCuHCF is evenly immobilized in PEIrGO matrix by diffusion crystallization.
High flux was obtained by the increased interlayer spacing of GO with PEI grafting.
Rapid and selective removal of Csþ was achieved through the adsorptive filtration.
It exhibited stable Csþ removal under various pH ranges and groundwater conditions.

a r t i c l e i n f o

a b s t r a c t

Article history: Received 7 January 2020 Received in revised form 14 February 2020 Accepted 16 February 2020 Available online 19 February 2020

As an attractive alternative to radioactive cesium removal, we introduced an adsorptive filtration method using a composite membrane consisting of potassium copper hexacyanoferrate (KCuHCF) and graphenebased support. Polyethyleneimine-grafted reduced graphene oxide (PEI-rGO), used as an immobilizing matrix, was effective not only in distributing KCuHCF inside the composite with the aid of abundant amino-functionality, but also in achieving high water flux by increasing the interlayer spacing of the laminar membrane structure. Due to the rapid and selective cesium adsorption properties of KCuHCF, the fabricated membrane was found to be effective in achieving complete removal of cesium ions under a high flux (over 500 L m2 h1), which is difficult in a conventional membrane utilizing the molecular sieving effect. This approach offers strong potential in the field of elimination of radionuclides that require rapid and complete decontamination. © 2020 Elsevier Ltd. All rights reserved.

Handling Editor: Y Yeomin Yoon Keywords: Cesium removal Potassium copper hexacyanoferrate Graphene oxide Adsorptive filtration

1. Introduction Severe risks of radioactive materials and irreversible long-term damage from nuclear accidents have led to discussions on the

* Corresponding author. E-mail address: [email protected] (J.W. Lee). https://doi.org/10.1016/j.chemosphere.2020.126262 0045-6535/© 2020 Elsevier Ltd. All rights reserved.

decommissioning of nuclear power plants and the disposal of radioactive waste (Baik et al., 2017; Hwang et al., 2019). Cesium137, one of the major radionuclides, is produced in the fission process of Uranium 235 and emits strong gamma rays with about a 30-year half-life (Yoon et al., 2019). Since radioactive cesium in aqueous solutions is chemically similar to potassium ions and easily enter the ecosystem, it is one of the most hazardous radioactive materials that requires attention among nuclear wastes and was

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also the most damaging material in the 2011 Fukushima nuclear accident (Yoshida and Kanda, 2012). Due to this severity, radionuclides, especially cesium, must be completely and safely removed and stored. For remediation of radionuclides, conventional wastewater treatment technologies such as evaporation or coagulation/precipitation can be used, but currently selective separation techniques are required for the final waste volume minimization (Nilchi et al., 2011). For this purpose, adsorption processes with high energy efficiency are actively being developed. In the case of selective cesium ion removal, the sieving effect from the structural specificity of crystals and organic molecules has been exploited. For instance, organic molecular sieves (Awual et al., 2014), twodimensional inorganics, such as transition metal dichalcogenides (Feng et al., 2018; Manos and Kanatzidis, 2009) and clays (Kim et al., 2018b; Park et al., 2017; Zhang et al., 2019), and titanosilicate (Kim et al., 2019c; Liu et al., 2015; Oleksiienko et al., 2017) showed selective Csþ removal performance. Among these candidates, the transition metal hexacyanoferrate (MHCF) has attracted the most attention due to its simple synthesis and superior adsorption performance for cesium ions (Kim et al., 2018a, 2018c). In many cases, the removal of cesium occurs by ion-exchange with Kþ in the interstitial sites of the MHCF crystal, and it is a rapid and selective process (Kim et al., 2017c; Roh et al., 2019). The selective adsorption characteristics are attributed to the lattice being able to accept only small hydrated ions such as cesium, and it can be slightly changed depending on the type of transition metal that forms a crystal structure with hexacyanoferrate (Vincent et al., 2014). However, most MHCFs have particle diameters of only a few tens of nanometers and are highly dispersible in water, making them difficult to recover after use (Kim et al., 2017a; Vanderheyden et al., 2018). The drawbacks caused by the small sorbent size have been overcome through various approaches, such as grafting them to porous materials or immobilizing them in polymer matrices (Kim et al., 2017b; Lee et al., 2019). Although this composite formation strategy was able to overcome the disadvantages of nanoparticle adsorbents, it could lead to reduced adsorption capacity and ion accessibility due to the support materials and still has been mainly evaluated only in batch-shaking operations. Meanwhile, membrane filtration is the most frequently used and promising continuous separation technology in wastewater treatments. Polymeric membranes such as polyamide are mainly used for deionization, but laminar membranes using twodimensional materials such as graphene oxide (GO) recently have been drawing attention (Kim et al., 2019b; Shi et al., 2018; Wang et al., 2018). Since it is possible to adjust the path width of permeate through a facile modification and has good stability, GO membrane has a wide application range (Li et al., 2018; Meng et al., 2019). Nonetheless, it is difficult to separate target species selectively with a high flux through size-sieving in the membrane process due to the trade-off between permeability and selectivity (Ding et al., 2019b, 2019a; Song et al., 2018). Particularly in the treatment of radioactive materials, which requires extremely high selectivity, it has been difficult to expect rapid removal from conventional membrane separation. To achieve selective cesium ion separation with a high flux, we demonstrate adsorptive filtration by a composite membrane using polyethyleneimine (PEI)-grafted GO and potassium copper hexacyanoferrate (KCuHCF) nanoparticles. The adsorptive filtration using the composite membrane fabricated by selective adsorbents and a matrix with sufficiently large pores could achieve high selectivity and permeability. It is expected to be a very attractive alternative for the treatment of radioactive materials, since the high selective adsorption capability can lead to final waste volume

minimization and increase the process efficiency due to rapid treatment. As an immobilizing matrix, we used PEI-grafted GO to widen the passage of permeate and evenly distribute cesiumselective adsorbent nanoparticles of KCuHCF, with the aid of abundant amino-functionality. Since KCuHCF has fast adsorption kinetics, the composite exhibited excellent cesium ion removal performance under a high water flux. 2. Material and methods 2.1. Materials Potassium hexacyanoferrate (K4[Fe(CN)6]$3H2O), branched polyethyleneimine (PEI, Mn: 10,000), and graphite powder (<20 mm) were purchased from Sigma Aldrich. Hydrogen peroxide was purchased from Daejung Co. Ltd., and copper sulfate (CuSO4$5H2O) was acquired from KANTO Chemical Co. Inc. Cesium chloride was supplied from Alfa Aesar. Sodium hydroxide, sulfuric acid, phosphoric acid, and potassium permanganate were obtained from Junsei Chemical. Polyethersulfone membrane (PES, 47 mm, 0.22 mm) was supplied by Millipore.a 2.2. Syntheses 2.2.1. Graphene oxide preparation Graphene oxide (GO) was synthesized by the improved Hummers’ method (Marcano et al., 2010). First, 3 g of graphite powder and 18 g of potassium permanganate were mixed in a flask. Separately, a solution containing 360 mL of H2SO4 and 40 mL H3PO4 was prepared and added to the flask slowly. The mixture was then allowed to react under mild stirring at 50  C for 12 h. Upon cooling to room temperature, the mixture was poured onto 400 mL of ice, and 3 mL H2O2 was added to the flask. A yellow-brown solid was obtained upon decanting the supernatant. GO was recovered after the solid was centrifuged at 10,000 rpm for 1 h, and the precipitate was washed with 30% HCl, deionized water, and ethanol. Finally, the GO powder was collected after freeze-drying for 3 days. 2.2.2. PEI functionalization of GO PEI functionalization of GO was conducted by modifying the reported method (Kim et al., 2019a). First, a 0.1 g L1 GO dispersion was prepared and sonicated for 5 h. The supernatant was then collected to obtain the exfoliated GO after centrifugation at 7000 rpm for 30 min. Separately, a 5 wt% PEI aqueous solution (Mn ~ 10,000) was prepared and added to the GO dispersion with NaOH (2 g L1) so that the concentration of PEI was 2 g L1. The mixture was then heated at 80  C for 6 h under magnetic stirring. GO was subsequently reduced and grafted with PEI, and the composite (rGO-PEI) was washed with deionized water several times with centrifugation at 9000 rpm and finally re-dispersed in DI water (approximately ~10 mg L1). 2.2.3. KCuHCF immobilized membrane fabrication CuSO4$5H2O was added to the rGO-PEI dispersion to attain a concentration of 0.02 M. The resulting dispersion was then stirred for 4 h to allow the copper ions to be adsorbed to the PEI-rGO. A certain amount of Cu-PEI-rGO dispersion was vacuum filtered on the PES substrate (47 mm diameter with a pore size of 0.2 mm, Millipore) to form the Cu-PEI-rGO membrane. The fabricated membrane was thoroughly washed with DI water and submerged in a 0.05 M K4Fe(CN)6 solution for 12 h to promote diffusioninduced precipitation between immobilized Cu2þ and [Fe(CN)6]4-. Finally, potassium copper hexacyanoferrate (KCuHCF)-immobilized membranes were firmly attached to the PES substrate and washed with DI water. The composite membranes were denoted as HCF-

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PEI-rGO with 1 mg deposition of PEI-rGO, and membranes, where ¼ 0.5 and 2 mg of PEI-rGO was deposited, were named HCFPEI-rGO-0.5 and 2, respectively.

2.3. Physicochemical characterization The surface morphology of the prepared membranes was characterized using scanning electron spectroscopy (SEM, Hitachi SU5000) coupled with energy dispersive spectroscopy (EDS) for elemental composition analysis. Transmission electron microscopy was carried out with a Tecnai F20 (FEI, 200 kV). To investigate the chemical functionalization, x-ray photoelectron spectroscopy (XPS) was performed with Axis-Supra (Kratos), and the peaks were analyzed through the Avantage software (Thermo VG package) by binding energy correction with reference to C 1s at 284.5 eV. Chemical bonds upon GO reduction and KCuHCF synthesis were identified using Fourier Transform Infrared Spectroscopy (FT-IR, Nicolet iS50) with an attenuated total reflectance (ATR) mode. The x-ray diffraction (XRD) patterns were obtained using Ultima IV (Rigaku) with Cu Ka (l ¼ 0.15418 nm) set at 40 kV and 40 mA.

2.4. Adsorptive filtration Water permeability and Csþ removal performance of HCF-PEIrGO membranes were evaluated using a dead-end filtration cell with an effective membrane area of 7.065 cm2. A slightly wet membrane was used and every filtration experiment was conducted after 100 mL of pure water was permeated under a pressure regulated to 4 bar by nitrogen gas. The adsorptive filtration of Csþ performance was investigated under a pressure of 1 bar by measuring the Csþ concentration of feed and permeate with an inductively coupled plasma mass spectrometer (ICP-MS, Agilent ICP-MS 7700S). The Csþ rejection efficiency (RE) was calculated with the following equation:

Cp RE ¼ 1  Cf

3

!  100 ð%Þ

(1)

where Cp (mg L1) and Cf (mg L1) is the Csþ concentration of permeate and feed, respectively. The permeate flux (J, L m2 h1) was calculated with the following equation:

J ¼ V=A$t

(2)

where V (L) is the volume of the permeate, A (m2) is the effective area of filtration cell, and t (h) is the time interval. 3. Results and discussion 3.1. Physicochemical characterization To evenly distribute the KCuHCF particles in a composite membrane, a PEI-rGO composite was synthesized first to utilize the abundant amino functional groups in PEI. As expressed in Fig. 1, exfoliated GO was simultaneously reduced and functionalized by the reaction with PEI under the alkaline condition. Then, copper ions were added to the dispersed PEI-rGO to be coordinated in the amino functional groups, followed by vacuum filtration on a PES support microfiltration membrane. By immersing the membrane in a K4Fe(CN)6 solution, the KCuHCF crystals were formed through the reaction between coordinated copper ions and diffused hexacyanoferrate ions. Through microscopic observations, the formation of the HCFPEI-rGO membrane was confirmed, as shown in Fig. 2. First, it was found that the exfoliated GO and PEI-rGO used in the experiments had a form of nanosheets, as shown in the TEM images (Figs. S1(a) and (b)), and it could form a thin film of about a few hundred nanometers (Figs. S1(c) and (d)). The PEI-rGO membrane presented irregularity and a rough surface compared to the laminar

Fig. 1. Schematic representation for the fabrication of HCF-PEI-rGO membranes.

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Fig. 2. Cross-sectional SEM images of (a) Cu-adsorbed PEI-rGO and (b) HCF-PEI-rGO membrane, and (c) top-view SEM image of HCF-PEI-rGO. (d) Cross-sectional SEM image and line scanning EDS spectra of N (blue), Fe (red), and Cu (orange) (scale bars: 5 mm). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

KCuHCF existed not only on the surface but also between the PEIrGO layers. The formation and Cu-coordination of the PEI-rGO composite used as the matrix of KCuHCF particles were demonstrated by the XPS analysis. As shown in Fig. 3(a), the high-resolution C 1s XPS spectrum of GO was deconvoluted into four peaks corresponding to graphitic sp2-hybridized carbon (CeC, 284.8 eV), hydroxyl and epoxy (CeO, 286.9 eV), carbonyl (C]O, 288.2 eV), and carboxyl groups (OeC]O, 289.3 eV) (Roy et al., 2015). After the reaction with PEI, the deconvoluted C 1s spectrum of PEI-rGO showed that the peaks of carbonyl and carboxyl groups completely disappeared, and the intensity of the CeO peak centered at 286.8 eV was reduced

GO membrane, and Cu-coordinated PEI-rGO formed a membrane with a thickness of about 1 mm (Fig. 2(a)). After the HCF-PEI-rGO membrane formation by the diffusion-induced reaction with K4Fe(CN)6, the thickness of the membrane did not change much (Fig. 2(b)), and relatively large KCuHCF crystals formed on the surface, as seen in the top-view SEM image (Fig. 2(c)). To ensure that Fe(CN)64 ions properly diffused into the composite and that KCuHCF is formed throughout the Cu-coordinated PEI-rGO layer, a thicker membrane was prepared by deposition in five-fold quantities and an elemental analysis of the membrane cross-section was performed by SEM-EDS. As seen in Fig. 2(d), the K, Cu, and N elements were evenly distributed within the layer, confirming that

(b Intensity (a.u.)

Intensity (a.u.)

(a

294

292

290

288

286

284

Binding Energy (E) (eV)

282

280 406

404

402

400

398

Binding Energy (E) (eV)

Fig. 3. XPS spectra of (a) C 1s for GO and PEI-rGO, and (b) N 1s for rGO-PEI and Cu-adsorbed rGO-PEI membranes.

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(b)

Absorbance (a.u.)

Normalized Intensity (a.u.))

(a)

4000

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3600

3200

2800

2400

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Wavenumber (cm-1)

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1600

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2 (º)

Fig. 4. (a) FT-IR spectra of GO, PEI-rGO, Cu-adsorbed PEI-rGO, and HCF-PEI-rGO membranes. (b) XRD patterns for PES support, GO, PEI-rGO, and HCF-PEI-rGO membranes.

through the reduction of GO (Liu et al., 2013). Furthermore, a shoulder peak centered at 285.5 eV was attributed to CeN groups from PEI, in addition to the CeC peak centered at 284.8 eV. The PEIrGO composite could then adsorb copper ions successfully, as shown in the Cu 2p spectrum (Fig. S2), and the binding of copper was verified through N 1s XPS spectra (Fig. 3(b)). The deconvoluted N 1s spectra showed that PEI-rGO has primary-, secondary-, and tertiary amino-functional groups, with the corresponding peaks centered at 398.5, 399.1, and 400.1 eV, respectively. After the coordination of copper ions, the peaks corresponding to the primaryand secondary amines were shifted to higher binding energy, 399.1 and 399.9 eV, respectively, although the peak from the tertiary amine (400.1 eV) was not shifted. This suggested that the electron pairs of amino functional groups in PEI contributed to the adsorption of copper ions to the composite. The in-situ reduction and amino-functionalization of GO through the reaction with PEI were further analyzed by FT-IR. As shown in Fig. 4(a), the characteristic broad bands between 3200 and 3600 cm1 indicating eOH stretching vibrations were clearly observed for the GO membrane, but in the PEI-rGO membrane, the intensity of those bands became weak and the peaks at 2850 and 2920 cm1 attributed to CeH stretching vibrations from PEI became relatively clear. In addition, through the reaction with PEI, the characteristic peaks at 1734 and 1625 cm1 indicating C]O and C]C stretching vibrations of GO disappeared and a shoulder peak at 1650 cm1 corresponding to the CeN of the amide bond was created. Therefore, these results exhibit that reduction and PEI grafting of GO were achieved. Change of the IR spectra after the copper ion adsorption was not noticeable, and after subsequent K4Fe(CN)6 diffusion, an intense characteristic peak at 2070 cm1 ascribed to C^N stretching vibration was observed, indicating that KCuHCF was formed inside and on the surface of the composite membrane. XRD analyses were conducted to determine whether the fabricated membrane has a laminar structure and the characteristics of the crystal components. As shown in Fig. 4(b), while the GO membrane has a laminar structure with a d-spacing of 8.27 Å, the PEI-rGO membrane did not exhibit peaks except for the amorphous peak attributed to the PES support, indicating that the regularity disappeared through the reduction of GO (Kim et al., 2019a). Similarly, no peaks were observed except for the amorphous peak after the coordination of Cu ions. Through the reaction with K4Fe(CN)6, KCuHCF crystals were formed and resulted in four characteristic peaks of K2Cu[Fe(CN)6] (PDF #20e0875) at 17.8, 25.1, 34.1, and 36.4 (Takahashi et al., 2015). Furthermore, the crystalline

size of the KCuHCF in the membrane was estimated with Scherrer’s equation:

L¼

K$l b$cos q

(3)

where K is a shape factor (dimensionless, 0.94), l is the X-ray wavelength (nm), b is the line broadening at half of the maximum intensity (FWHM, rad), and q is the diffraction angle at the peak (rad). From the distinguishable peaks at 17.8 and 25.1, the calculated crystalline size is 11.2 nm, which is consistent with the size of KCuHCF in previous works (Kim et al., 2017a). 3.2. Adsorptive filtration To assess whether the prepared HCF-PEI-rGO membrane could be applied to the rapid treatment of wastewater, water flux was measured using pure water. Fig. 5(a) shows the pure water flux according to the pressure change. All the membranes of different loading amounts had a proportional increase in water flux as the pressure increased, and the flux decreased as the loading amount of HCF-PEI-rGO on the PES support increased, as expected. These flux values are large compared to the reverse osmosis and nanofiltration membranes such as a GO laminar membrane (<100 L m2 h1 bar1) (Song et al., 2018), as the reaction with PEI has increased dspacing and irregularity. The high flux can be said to be favorable conditions for application to adsorptive filtration by taking advantage of the rapid ion-exchange of KCuHCF. The Csþ adsorption performance was determined by measuring the concentration of permeate at intervals by the continuous filtration of a 1 ppm CsCl solution (Fig. 5(b)). As permeation was carried out with 100 mL of the solution while controlling the loading amount of the adsorptive membrane, the PEI-rGO membrane was able to remove Csþ initially, but the removal efficiency sharply dropped due to a lack of adsorption capacity. The removal efficiency of HCF-PEI-rGO-0.5 gradually decreased to less than 95% from the fifth cycle, due to the small adsorption capacity caused by the insufficient loading amount and possibly because the high flux also prevented cesium ions from contacting KCuHCF sufficiently. On the contrary, HCF-PEI-rGO and HCF-PEI-rGO-2 removed more than 99% of cesium ions of 100 mL solutions; in other words, 130 mg of cesium could be completely removed by a 1 m2 membrane. Such high adsorption capacity is beneficial to treat large volumes of cesium contaminated water, leading to waste volume reduction. Furthermore, it was confirmed that the adsorbed cesium in the

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(a)

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80 60 40 20

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Fig. 5. (a) Pure water flux as a function of pressure and (b) Csþ removal efficiency as a function of filtrate volume (Initial Csþ concentration was 1 ppm).

membrane was not easily released even after 100 mL of pure water and 100 mL of 1 mM HCl were subsequently penetrated (Fig. S3). From these results, the remaining adsorptive filtration was characterized with the HCF-PEI-rGO membrane, considering the treatment rate and capacity. To determine the effect of competitive cations on selective Csþ removal using the HCF-PEI-rGO membrane, high concentrations of Naþ, Kþ, and Ca2þ were added to a 1 ppm Csþ solution and filtrated with 50 mL. As shown in Fig. 6(a), the molar concentration of Naþ was increased from 0.1 to 1 mol L1, and the Csþ removal efficiency was gradually decreased to 89%. Similarly, from the results of an experiment using Ca2þ (Fig. 6(b)), the removal efficiency of the representative divalent ion Csþ decreased to 92% with increasing

Ca2þ concentration. It can be seen that Naþ and Ca2þ did not significantly reduce the selective Csþ removal of KCuHCF, although the molar concentrations of both Naþ and ions were around 100 times higher than that of Csþ. As already reported, their hydrated ion sizes are larger than Csþ, making capture by the KCuHCF lattice difficult, and consequently the result of a similar experiment using Kþ showed largely reduced Csþ removal efficiency with increasing Kþ concentration (Fig. S4) (Wang et al., 2015). Under various pH conditions and simulated groundwater conditions, Csþ removal efficiency was evaluated to confirm the stability in various hydrological environments of the HCF-PEI-rGO membrane (Fig. 6(c)). From the results of filtration with 50 mL samples of a 1 ppm CsCl solution in a range of pH 2e12, prepared by

Fig. 6. Csþ removal efficiencies of HCF-PEI-rGO membrane as a function of co-existing (a) Naþ concentration and (b) Ca2þ concentration. Csþ removal efficiencies (c) in various pH and (d) as a function of filtrate groundwater volume. (Initial Csþ concentration was 1 ppm).

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titration using HCl and NaOH, all samples showed more than 98% Csþ removal efficiency, although the decomposition of KCuHCF occurred in the extreme ends of the pH range. Naþ ions present in basic conditions did not have a significant effect on Csþ removal, as shown in the competitive ion experiments, and protons caused slight inhibition of Csþ adsorption in acidic conditions (Kim et al., 2017a). To confirm the applicability of the membrane to practical remediation, 1 ppm of Csþ was added to the solution prepared by simulating general groundwater conditions (146 ppm of Naþ, 6 ppm of Kþ, 21 ppm of Mg2þ, 5 ppm of Ca2þ) from the literature (Fig. 6(d)) (Datta et al., 2014). It can be seen that the HCF-PEI-rGO membrane showed stable Csþ removal efficiency, and the removal efficiency was slightly degraded compared to the experiment in Fig. 5(b). 4. Conclusions A novel strategy has been presented for the fabrication of a composite membrane for adsorptive filtration of cesium ions by taking advantage of the rapid and selective adsorption performance of potassium copper hexacyanoferrate (KCuHCF). As an effective immobilizing matrix of KCuHCF, polyethyleneimine-grafted GO was used to induce a high flux by widening the passage of wastewater and to promote coordination of a copper precursor with abundant amino-functional groups of PEI for subsequent diffusion-induced crystallization using [Fe(CN)6]4-. Microscopic and spectroscopic observations were conducted to verify the processes of grafting of PEI with the simultaneous reduction of GO and immobilization of KCuHCF crystals inside the PEI-rGO composite. This fabrication methodology was effective in obtaining high water fluxes over 500 L m2 h1 and achieved stable Csþ removal due to the good adsorption kinetics of KCuHCF. On the basis of these rapid treatments, high removal performance, and simplicity of final waste disposal, adsorptive filtration using the HCF-PEI-rGO membrane can provide a promising alternative to radionuclide treatment processes. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. CRediT authorship contribution statement Yonghwan Kim: Conceptualization, Methodology, Investigation, Writing - original draft. Ho Hyeon Eom: Data curation, Investigation. Yun Kon Kim: Conceptualization, Writing - review & editing. David Harbottle: Supervision, Project administration. Jae W. Lee: Writing - review & editing, Supervision, Project administration, Funding acquisition. Acknowledgements The authors are grateful for the financial support from the UKRepublic of Korea Joint Research Program. Jae W. Lee acknowledges the NRF grant (NRF-2019M2A7A1001773) funded by the Ministry of Science and ICT, Republic of Korea. D. Harbottle acknowledges the financial support of the Engineering and Physical Sciences Research Council grant number EP/S032797/1. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.chemosphere.2020.126262.

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