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Effective 137Cs+ and 90Sr2+ immobilisation from groundwater by inorganic polymer resin Clevasol® embedded within a macroporous cryogel host matrix

Effective 137Cs+ and 90Sr2+ immobilisation from groundwater by inorganic polymer resin Clevasol® embedded within a macroporous cryogel host matrix
Effective 137Cs+ and 90Sr2+ immobilisation from groundwater by inorganic polymer resin Clevasol® embedded within a macroporous cryogel host matrix

The conservative fission products 137Cs and 90Sr are of concern when present in groundwater, as they present a radiological hazard to organisms and can be transported long distances from their source. To provide an interceptive permeable reactive barrier (PRB) solution which accommodates the throughflow of groundwater whilst removing 137Cs+ and 90Sr2+, we report the synthesis of a novel composite cryogel which performs as a permeable hierarchical sorbent. This material incorporates the ion-exchanger Clevasol® into a PVA-based cryogel host matrix with interconnected macropores, producing a composite cryogel (Clevasol®-PVACC). Clevasol®-PVACC enables the in-situ deployment of an ion-exchanger with rapid uptake kinetics for 137Cs+ and 90Sr2+, inside of a robust and permeable scaffold with green chemistry. Clevasol®-PVACC has a facile, one-pot and scalable synthesis, and can possibly also be used at other stages of the nuclear fuel cycle, such as radioactive liquor treatment. Critically, the incorporated Clevasol® resin is vitrifiable, which is optimal for long-term storage and geological disposal if high activities are adhered onto the resin. The effective partition coefficients (kd) and effective Langmuir uptake capacities (qmax) of the Clevasol® resin in Sellafield groundwater simulant are respectively 105 mL/g and 298 mg/g for Cs+, and >104 mL/g and 128 mg/g for Sr2+.

Cesium/cesium, Environmental radioactivity, Radionuclides, Remediation, Sellafield, Strontium
Chaplin, Joshua D.
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Berillo, D.
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Purkis, J. M.
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Byrne, Marie
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Tribolet, A. D.C.C.M.
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Warwick, P. E.
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Cundy, A. B.
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Chaplin, Joshua D.
2623b2e6-0c41-4252-ba6c-aa368d72ad28
Berillo, D.
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Purkis, J. M.
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Byrne, Marie
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Tribolet, A. D.C.C.M.
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Warwick, P. E.
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Cundy, A. B.
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Chaplin, Joshua D., Berillo, D., Purkis, J. M., Byrne, Marie, Tribolet, A. D.C.C.M., Warwick, P. E. and Cundy, A. B. (2022) Effective 137Cs+ and 90Sr2+ immobilisation from groundwater by inorganic polymer resin Clevasol® embedded within a macroporous cryogel host matrix. Materials Today Sustainability, 19, [100190]. (doi:10.1016/j.mtsust.2022.100190).

Record type: Article

Abstract

The conservative fission products 137Cs and 90Sr are of concern when present in groundwater, as they present a radiological hazard to organisms and can be transported long distances from their source. To provide an interceptive permeable reactive barrier (PRB) solution which accommodates the throughflow of groundwater whilst removing 137Cs+ and 90Sr2+, we report the synthesis of a novel composite cryogel which performs as a permeable hierarchical sorbent. This material incorporates the ion-exchanger Clevasol® into a PVA-based cryogel host matrix with interconnected macropores, producing a composite cryogel (Clevasol®-PVACC). Clevasol®-PVACC enables the in-situ deployment of an ion-exchanger with rapid uptake kinetics for 137Cs+ and 90Sr2+, inside of a robust and permeable scaffold with green chemistry. Clevasol®-PVACC has a facile, one-pot and scalable synthesis, and can possibly also be used at other stages of the nuclear fuel cycle, such as radioactive liquor treatment. Critically, the incorporated Clevasol® resin is vitrifiable, which is optimal for long-term storage and geological disposal if high activities are adhered onto the resin. The effective partition coefficients (kd) and effective Langmuir uptake capacities (qmax) of the Clevasol® resin in Sellafield groundwater simulant are respectively 105 mL/g and 298 mg/g for Cs+, and >104 mL/g and 128 mg/g for Sr2+.

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Accepted/In Press date: 30 June 2022
e-pub ahead of print date: 6 July 2022
Published date: November 2022
Additional Information: Funding Information: We thank ADePhine GmbH (Bern, Switzerland) for supplying the Clevasol® resin for our testing. D Berillo acknowledges the European Union's Horizon 2020 Research and Innovation Programme (under the Marie Skłodowska-Curie Fellowship grant agreement 701289) which supported time when writing this paper. A B Cundy, P E Warwick and J M Purkis acknowledge funding from the TRANSCEND (TRANsformative SCience and Engineering for Nuclear Decommissioning) consortium ( EPSRC grant number EP /S01019X/1). We thank three peer reviewers for improving the manuscript through their comments. Funding Information: Column experiments were performed to determine breakthrough curves for Cs and Sr in a simulated in-situ scenario, whereby contaminated groundwater would flow through the Clevasol®-PVACC in one direction. A closed system was assembled as per Fig. SI IV in the Supporting Information, whereby a Gilson Minipuls 3 peristaltic pump set to 0.09 rpm delivered the stable Cs or Sr influent solution constantly at 1.60–1.65 cm3/h through the column. This flow is within the range of the Quaternary Upper aquifer at Sellafield [57]. Samples were collected at the base of the column throughout the experiment by a modified Redirac LKB 2112 fraction collector. The column (7 mm diameter x 58 mm length) was wet packed with Fisher Chemicals Extra Pure sand. System flow was visually verified using Bromocresol green, and the absence of Cs and Sr sorption onto the sand was confirmed by passing influent through the column when only packed with sand. The experiment was then run with a 1 mm layer of Clevasol®, of mass between 37.4 and 39.6 mg, at the base below the sand. Influent solutions contained stable Sr or Cs at a concentration of 20 ppm, made by dissolving CsCl or SrCl2·6H2O in Milli-Q H2O or SGS. Sr samples were measured using a Thermo Scientific CAP 6000 series ICP-OES. Cs samples were measured with an Agilent 8800 Triple Quad ICP-MS, with samples diluted in 2.5% HNO3 with a 5 ppb internal Re standard and using a peristaltic pump at 1 mL/min.The incorporation of Clevasol® particles in the Clevasol®-PVACC significantly reduces SSA relative to blank PVA-based cryogel without particles (Table 1). Using the reported materials and methodology herein, we found the blank PVA-based cryogel to have a significantly higher SSA than previously reported (∼130 vs ∼60 m2/g [53]); we attribute this most probably to variations in molecular weight and deacetylation levels between PVA brands [58]. Previously, we reported cryogels based on CHI-polyelectrolyte complexes which also possess an internal mesoporous structure [59]; SSA of the cryogels presented in Table 1 are comparable to CHI-based functionalised cryogels based on CHI-GA with Pd or Au nanoparticles [50,52]. Clevasol®-PVACC had a higher Young's modulus (Table 1) and demonstrated better resistance to strain (Fig. SI VI in the Supporting Information) than the blank PVA cryogel, demonstrating that the incorporation of the Clevasol® particles into the PVA-based cryogel significantly increased the durability of the material. This is a beneficial trait for practical environmental application within PRBs. Functionalising a PVA-based cryogel with other fine-grained sorbent particles could possibly therefore also potentially enhance the structural integrity of the composite material relative to the blank material, which is promising for future research using PVA-based cryogels as a host matrix. Our additional testing to investigate the potential of CHI as an alternative polymer to PVA showed that the blank CHI-based cryogel had a higher rigidity than the PVA-based cryogel (i.e. undergoing lower strain at higher stresses, Fig. SI VI in the Supporting Information), indicating that it likely has a much higher resistance to hydrostatic pressure. However, this could equally indicate that CHI-based cryogels may be more brittle than PVA-based cryogels. Further research could therefore focus on the optimisation of the synthesis of cryogel-sorbent composites, including exploring the effects of particle incorporation into CHI-based cryogels.We thank ADePhine GmbH (Bern, Switzerland) for supplying the Clevasol® resin for our testing. D Berillo acknowledges the European Union's Horizon 2020 Research and Innovation Programme (under the Marie Skłodowska-Curie Fellowship grant agreement 701289) which supported time when writing this paper. A B Cundy, P E Warwick and J M Purkis acknowledge funding from the TRANSCEND (TRANsformative SCience and Engineering for Nuclear Decommissioning) consortium (EPSRC grant number EP/S01019X/1). We thank three peer reviewers for improving the manuscript through their comments. Publisher Copyright: © 2022 The Author(s)
Keywords: Cesium/cesium, Environmental radioactivity, Radionuclides, Remediation, Sellafield, Strontium

Identifiers

Local EPrints ID: 470485
URI: http://eprints.soton.ac.uk/id/eprint/470485
PURE UUID: 093f226c-90d2-46f2-8a60-2ec9309804d5
ORCID for J. M. Purkis: ORCID iD orcid.org/0000-0002-6387-1220
ORCID for P. E. Warwick: ORCID iD orcid.org/0000-0001-8774-5125
ORCID for A. B. Cundy: ORCID iD orcid.org/0000-0003-4368-2569

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Date deposited: 11 Oct 2022 16:51
Last modified: 19 Oct 2022 01:58

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Contributors

Author: Joshua D. Chaplin
Author: D. Berillo
Author: J. M. Purkis ORCID iD
Author: Marie Byrne
Author: A. D.C.C.M. Tribolet
Author: P. E. Warwick ORCID iD
Author: A. B. Cundy ORCID iD

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