Several novel extraction chromatography resins (EXC) have been synthesised by solvent impregnation of the triazine ligands 6,6 -bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[1,2,4]triazin-3-yl)-2,2 - bipyridine (CyMe4BTBP) and 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-1,10- phenanthroline (CyMe4BTPhen) into Amberlite XAD7 and Amberchrom CG300 polymer supports.
Journal of Chromatography A 1669 (2022) 462950 Contents lists available at ScienceDirect Journal of Chromatography A journal homepage: www.elsevier.com/locate/chroma Rapid separation of americium from complex matrices using solvent impregnated triazine extraction chromatography resins Joe Mahmoud a, Matthew Higginson b, Paul Thompson b, Christopher Gilligan b, Francis Livens a, Scott L Heath c,∗ a b c Department of Chemistry, University of Manchester, M13 9PL, UK AWE, Aldermaston, Reading, RG7 4PR, UK Department of Earth and Environmental Sciences, University of Manchester, M13 9PL, UK a r t i c l e i n f o Article history: Received September 2021 Revised March 2022 Accepted March 2022 Available online March 2022 Keywords: Americium Separation Nuclear forensics Extraction chromatography a b s t r a c t Several novel extraction chromatography resins (EXC) have been synthesised by solvent impregnation of the triazine ligands 6,6 -bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[1,2,4]triazin-3-yl)-2,2 bipyridine (CyMe4 BTBP) and 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-1,10phenanthroline (CyMe4 BTPhen) into Amberlite XAD7 and Amberchrom CG300 polymer supports The resins have been physically characterised by a suite of spectroscopic, analytical and imaging techniques The resins have also been evaluated in terms of their ability to selectively extract americium from complex matrices intended to simulate those typical of spent nuclear fuel raffinate, environmental samples and nuclear forensics samples The resins have been compared with previously reported attempts to generate EXC resins based on CyMe4 BTBP and CyMe4 BTPhen Previously reported resins all rely on complex synthesis for the formation of a covalent bond between extractant and support by contrast with the simpler solvent impregnation method reported here The Amberchrom supported CyMe4 BTBP resin achieved a weight distribution ration (DAm ) of 170 within 60 and a decontamination factor (DF) of >10 0 for americium over lanthanides by column chromatography The Amberchrom CyMe4 BTPhen resin achieved a DAm of 540 within 30 and a DF for americium from lanthanides of 60–160 © 2022 The Authors Published by Elsevier B.V This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Introduction The purification of americium from complex matrices is a great challenge in radiochemical separation science Separation from the chemically and physically similar lanthanide elements is particularly difficult [1] The separation of americium from the lanthanide elements has major applications in nuclear fuel reprocessing [2], environmental monitoring [3] and nuclear forensics [4] Two strategies currently exist for the long-term management of spent nuclear fuel; the first is disposal in an underground facility, and the second is reprocessing, which can include the partitioning of minor actinides, of which americium is one, from the fission products This can be followed by transmutation of the minor actinides to radionuclides with shorter half-lives, i.e less hazardous, by ‘burning’ the minor actinides as fuel in ‘Generation IV’ fast neutron reactors [5] ∗ Corresponding author E-mail address: scott.l.heath@manchester.ac.uk (S.L Heath) The feasibility and safety of the first approach would be greatly facilitated by the removal of americium from spent nuclear fuel since total minor actinide content is typically about only 0.1% of the total mass, yet americium alone contributes strongly to the long-term associated heat and radiotoxicity [6,7] The second approach is reliant on the effective partitioning of americium from the fission products which occur as 5% of spent nuclear fuel, 1–2% of which consist of lanthanides [8] The lanthanides have a high neutron absorption cross section and hence would act as a poison in potential americium-based nuclear fuel [8,9] Americium is also a key element of interest in environmental monitoring to assess the environmental and ecological impact of releases caused by nuclear weapons testing, nuclear power production and the management of nuclear wastes [10] The key isotope of interest is Am-241, which is generated by the decay of its parent isotope Pu-241 (t1/2 14.3 years) which is also an environmental contaminant released by nuclear weapons testing and civil nuclear operations One reason for the importance of Am-241 for environmental monitoring is that it can be used as an indicator of the presence of plutonium easily by rapid gamma counting of samples https://doi.org/10.1016/j.chroma.2022.462950 0021-9673/© 2022 The Authors Published by Elsevier B.V This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) J Mahmoud, M Higginson, P Thompson et al Journal of Chromatography A 1669 (2022) 462950 If Am-241 is detected in samples those samples can be sent for time consuming full radiochemical analysis for plutonium Environmental samples are typically comprised of soil and sediment which are inherently complex matrices and usually contain approximately 200 ppm of lanthanides [10] Nuclear Forensic Analysis (NFA) is a multidisciplinary science that requires methodologies for the collection and analysis of seized nuclear or radioactive material, or material that may be contaminated with nuclear or radioactive material for the purpose of informing criminal investigations NFA utilises radio-analytical chemistry and radiometric techniques in order to establish isotopic and elemental composition, macro- and microscopic structure, amongst other properties, in an attempt to elucidate the provenance and intended use of interdicted nuclear or radioactive material [4] Nuclear forensic investigations may require an estimation of the age of nuclear material, where age is defined as the time elapsed since the last chemical processing of the material The age dating of plutonium is of particular importance in nuclear forensics since it can be used to distinguish legacy material from material more recently produced Several parent-daughter pairs can be exploited for the dating of plutonium, though most rely on plutonium/uranium ratios that require larger sample sizes [11] and can be more sensitive to environmental interferences [12] The Pu241/Am-241 pair can also be used to determine the age of a plutonium sample and is less sensitive to environmental contaminants allowing for more accurate age verification The use of Pu-241/Am241 isobars does however require more intensive chemical preprocessing for sufficient separation so as to allow for analysis by mass spectrometry and alpha spectrometry [11–13] Age dating information may be key to the enforcement of a negotiated Fissile Materials Cut-Off Treaty (FMCT) [11] which aims to ban the production of fissile material for use in nuclear weapons [14] The applications discussed all typically require the separation of very small quantities (fg-pg) of americium from complex matrices that can contain many naturally occurring elements of the Periodic Table at greater than mg/g concentrations Unfortunately, the methods currently available for the purification of americium from these interferences are typically very time-consuming, multi-stage flowsheets of chemical operations that require the application of complex chemistry and demand considerable skill on the part of the operator and are dependant on a well characterised matrix for efficient recovery of americium A major drawback of most separation schemes is that collection of the purified americium fraction is usually one of the last stages, meaning a lot of effort is expended on removing all other elements to leave americium, rather than removing americium at the start of these separation schemes Extraction chromatography (EXC) is based upon the same principles as solvent extraction (SX) but the separation is carried out using a chromatographic column The extractant is physically adsorbed or covalently bound onto the surface of a porous support, usually an organic polymer, consisting of bead-like particles [15] Benefits of EXC over SX include: • • • • • Fig Molecular structures of CyMe4 BTBP and CyMe4 BTPhen multi-stage chromatographic techniques and ease of operation of ion-exchange chromatography [16,17] There are currently several EXC resins commercially available that are commonly used in f-block element separations, but none that are specifically selective for americium over lanthanides without the use of toxic thiocyanate reagents [18] EXC may represent the cleanest and simplest approach to rapid separations of americium from complex matrices provided that a suitably efficient and selective extractant can be devised The efficacy of the triazine ligands CyMe4 BTBP (BTBP) and CyMe4 BTPhen (BTPhen) in selective solvent extractions of americium for its purification from lanthanides is well documented in the literature [19–22] with BTBP representing the current European reference ligand for actinide/lanthanide separations [23] The molecular structres of the ligands are shown in Fig A handful of attempts have been made to immobilise BTBP and BTPhen onto solid supports to generate an EXC resin capable of selective americium extraction from aqueous media [24–27], and these attempts are reviewed in Section 1.1 These methods however all rely on the generation of a covalent bond between the ligand and support This work describes the synthesis and characterisation of BTBP and BTPhen EXC resins produced by the solvent impregnation method [28–35] which provides a simpler, faster and cheaper synthetic route for the production of EXC material 1.1 Review of Immobilised BTBP & BTPhen extractants Few examples exist in the literature of the production of EXC resins based on BTBP and BTPhen extractants but these examples are reviewed here Harwood showed that CyMe4 BTPhen can be immobilised on silica-coated γ -Fe2 O3 magnetic nanoparticles (MNPs) by a phenyl ether linkage to the C-5 of the phenanthroline unit [24] The functionalised MNPs were subsequently used for a solid-liquid extraction of Am(III) from Eu(III) with SFAm/Eu =1700 ± 300 in M nitric acid [24], compared with SFAm/Eu =400 in comparable solvent extraction experiments [20] and also allowing the possibility of magnetic collection Generation of EXC resins by bonding the BTBP and BTPhen moieties to silica gel gave 14% and 10% (w/w) loading respectively [25] Batch experiments showed that the BTBP resin had poor affinity for both Am(III) and Eu(III) in the 0.001–4 M nitric acid range and poor separation factors with high uncertainties were observed after sonication and shaking in contact with Am-241 and Eu-152 tracers [25] The BTPhen resin was more successful, with maximum measured weight distribution ratios of DAm =4900 ± 1000 in 0.1 M nitric acid and a maximum SFAm/Eu =140 in M nitric acid Follow-up work suggested that the complex between the surface-bound ligand and the metal forms a 1:1 complex with a 10-coordinate metal ion, including three nitrate ligands, as opposed to the 2:1 ligand to metal complexes found in the solvent extraction system, due to the short carbon-link chain length between the silica particle and ligand [24,25] The BTPhen EXC resin was tested in 0.001–4 M perchloric acid A significant drop in distribution ratios for both metals was observed by comparison with elimination of the requirement for mixing and phase separation and associated issues around ligand solubility and phasetransfer kinetics, removal of the possibility of third phase formation, allowance for variable elution profile, the reduction, or total absence, of radioactive organic waste streams, the potential to recondition and reuse the resin and improve cost effectiveness For these reasons EXC is often touted as offering both the high selectivity of SX systems alongside the advantages associated with J Mahmoud, M Higginson, P Thompson et al Journal of Chromatography A 1669 (2022) 462950 the nitric acid system at all concentrations except 0.001 M This was interpreted as highlighting the importance of the nitrate ion in the extraction [36] An EXC resin produced by the Heath group was formed by covalently binding Me4 BTPhen via an aniline link to poly(vinylbenzene) [26] The resin gave americium recoveries of greater than 95% and decontamination factors greater than 10 0 When applied to a complicated mixture, designed to simulate a nuclear forensic sample, americium recovery was unaffected and only cadmium and praseodymium co-extracted [26] The BTPhen ligand has also been electrospun into polystyrene fibres [27] which showed reasonable distribution coefficients, with a maximum DAm =780 ± 50 in 0.1 M nitric acid and a maximum SFAm/Eu =57 ± in M nitric acid The fibres also showed an ability to extract curium with a maximum DCm =440 ± 40 in M nitric acid 2.3 Batch experiments Resin (100 mg) was soaked for a minimum of h in >18 M deionised water before being removed from the water and added to a solution containing 50–100 Bq Am-241 in the stated acids and vortex mixed at 20 0 rpm for 1–60 The acid solution was drained and the resin and solution reweighed to allow for the application of a mass correction in the weight distribution calculation The acid solution was transferred to a standard measurement geometry and counted by gamma spectroscopy 2.4 Column studies A standard plastic column, with an internal diameter of mm, was packed to a 39 mm height using 0.6–0.7 g of resin These dimensions were chosen to emulate the size of many pre-loaded commercially available EXC resin columns typically used in radiochemical separations The column was loaded with a minimum volume of solution containing 50–100 Bq of Am-241 and mg of stable Be(II), Sr(II), Cd(II), Cs(I), Ba(II), Y(III), Mo(VI), Ce(III), Pr(III), Nd(III), Sm(III), Tb(III) and Ag(I) generated from their nitrate/hydrochloride salts or otherwise purchased as a certified standard from Essex Scientific Laboratories Ltd, UK All elements were at natural isotope abundances The column was eluted with the stated elution profiles with a flow rate of 0.2 mL min−1 controlled using a vacuum box Each fraction was collected and made to a standard geometry before being counted by gamma spectroscopy A small aliquot was removed and diluted for analysis of stable isotopes by ICP-MS Materials and methods 2.1 General All radionuclides used were provided from calibrated stocks in the School of Chemistry, University of Manchester Micropipettes of 10–10 μL, 20–20 μL, 0.1–1 mL and 2–10 μL were calibrated on a decimal place balance with >18 M deionised water in the temperature range 18–22 °C and were found to be within their stated range All acid solutions were made from analytical grade concentrated solutions and were diluted with >18 M deionised water Gamma counting was performed using a Canberra 2020 coaxial HPGe gamma spectrometer with an Ortec DSPEC-50 multi-channel analyser energy and efficiency calibrated for the geometry used Gamma spectroscopy was performed against a standard of known activity counted in the same geometry and Am-241 was quantified using the diagnostic photon energy of Am-241 (59.5 keV) Limits of detection were calculated by the GammaVision software Peaks of values greater than 3σ above the background count were considered significant ICP-MS analysis was performed on an Agilent 7500cx spectrometer Multiple standards for each element in the range 1–100 ppb were used for ICP-MS quantification All reagents and solvents used were of standard analytical grade The estimated uncertainty on the measurements of stable isotopes quantified by ICP-MS is 10% based on a standard uncertainty multiplied by a coverage factor k = 2, providing a level of confidence of approximately 95% Infrared Spectrometry was performed using a Bruker Invenio-S infrared spectrometer Scanning electron microscope images were produced using a FEI Quanta 650 FEG ESEM equipped with a Bruker XFlash® |30 silicon drift detector (SDD) instrument Samples were prepared with a gold coating Results & discussion The aim of this work was to produce an americium selective EXC resin based upon the solvent impregnation of BTBP and BTPhen extractants into polymer supports This allows for a simpler, faster and cheaper method to produce the extraction chromatography material by comparison with the covalent bond forming methods reviewed in Section 1.1 The benchmark for a successful extractant was considered to be a material that could achieve a selective americium extraction with a decontamination factor of >10 0 over lanthanides with both separation and quantification of Am-241 deliverable within one working day These criteria were chosen as they represent the standard achieved by the covalently bound BTPhen resin previously reported [26] A decontamination factor is a measure of the purification of the component that is to be extracted (product) from another component (interference) The principle is commonly used in radiochemical separations and is defined in Eq (1): DF = Pf inal /Pinitial I f inal /Iinitial (1) Decontamination factor Eq (1) where P represents the Product and I the Interference, both of which are commonly expressed in units of activity in the case of radioactive isotopes or alternatively in units of concentration The term ‘separation factor’ (SF) is also commonly used to quantify separations In the context of the work reviewed and presented here SF is taken to be the ratio of distribution coefficients of the target material to be extracted and the interference, as is common in the literature The EXC resins produced have also been characterised in terms of extractant loading, homogeneity of distribution of the extractant across the support and the accuracy and reproducibility of the production method Methods for determination of the extraction capabilities of EXC resins are common in the literature, although 2.2 Resin synthesis Polymer (Amberlite XAD7/Amberchrom CG300) was pretreated according to the manufacturer’s instructions The required quantity of polymer was added to a solution of ligand (CyMe4 BTBP/CyMe4 BTPhen) that had been dissolved in acetone with stirring at 45 °C The ratio of polymer to ligand was chosen to meet the target loading on the resin, i.e g of 40% (w/w) resin consisted of g of pre-treated polymer added to 0.4 g of ligand dissolved in acetone The resulting slurry was left being stirred at room temperature for hour before the excess acetone was removed using a rotary evaporator J Mahmoud, M Higginson, P Thompson et al Journal of Chromatography A 1669 (2022) 462950 Table Calculated ligand loading based upon combustion analysis of EXC resins ID Resin Resin Resin Resin Resin Resin Resin Resin Ligand Substrate Target Loading /% (w/w) Measured Loading /% (w/w) RSD /% CyMe4 BTBP CyMe4 BTPhen CyMe4 BTPhen CyMe4 BTBP CyMe4 BTBP CyMe4 BTPhen CyMe4 BTPhen Me4 BTPhen Amberlite Amberlite Amberchrom Amberchrom Amberchrom Amberchrom Amberchrom PVB 3.5 3.5 40 40 40 40 3.5 3.6 31 52 42 42 6 0.5 3 4 Fig SEM images of Amberchrom CG300 starting material and Resins 4–8 detailed physical characterisation of EXC resins is less so A robust method for the cheap and easy synthesis of a selective EXC resin could theoretically be generalised to extraction of any metal by judicious choice of ligand Such a method could provide a powerful tool for radiochemical separation procedures The materials synthesised in this work have been compared with previous attempts to produce EXC resins using BTBP and BTPhen extractants which have been reviewed in Section 1.1 to the surface of the beads and dislodged during sample preparation or whether the material consists of both surface bound ligand and unbound crystalised ligand The BTPhen ligand presents a different morphology (Resin and Resin 7) The longer, thinner crystals of the BTPhen ligand appear to be less homogenously distributed about the support than in the case of the BTBP and perhaps less strongly closely associated with the surface of the polymer Resin is a covalently bound resin previously synthesised [26] The Me4 BTPhen ligand appears to be more evenly distributed across the Amberlite polymer beads in this resin by comparison with the solvent impregnated resins There is a total absence of unbound ligand in the interstitials which is to be expected given the covalent bond between the ligand and the support 3.1 Physical characterisation of resins 3.1.1 IR spectroscopy IR spectroscopy showed phenanthroline stretches, diagnostic of the BTBP and BTPhen ligands in both the Amberlite and Amberchrom materials [20] qualitatively confirming the presence of the ligands on the supports 3.2 Radiochemical separations 3.2.1 Batch experiments The affinity of the resins for the metals to be extracted from solution has been characterised by the weight distribution ratio (Dw ) parameter (Eq (2)) The term A0 represents the initial activity of the metal being extracted, As the activity remaining in solution post extraction, mL the volume of solvent used in the extraction and g the grams of resin Units of concentration or mass may also be used rather than activity in the case of non-active metals In this work Dw for non-active metals has been calculated based upon mass in grams 3.1.2 Elemental analysis Elemental analysis for nitrogen was used to measure the extractant loadings on the polymer supports (Table 1) 3.1.3 Scanning electron microscopy Scanning electron microscope (SEM) images were taken of the starting and ligand-loaded materials, except for resins 1–3 which showed no americium extraction capability The images of the starting material and ligand-loaded resins are shown in Fig The BTBP loaded resins (Resin and Resin 5) have the ligand crystallised as platelets adhering to the surface of the polymer support Nitrogen mapping is consistent with localisation of the BTBP ligand in these features The ligand is evenly distributed on the individual polymer bead shown, although unbound ligand is also seen in the interstitial space It is unclear from these images whether this crystallised ligand was originally weakly bound Dw = (A0 − As ) mL A0 g (2) Eq (2): Weight distribution ratio This metric was chosen as it is commonplace in the literature [17,18,25,27,36,37–43] and thus provides a convenient point of comparison between the resins examined here and those previously reported elsewhere The weight distribution ratio is also eas4 J Mahmoud, M Higginson, P Thompson et al Journal of Chromatography A 1669 (2022) 462950 ily converted into other common measures of extraction capability such as capacity factor (k’) and free column volumes (FCV) for comparison between batch experiment systems and column experiments [44] and bound by aniline linkage with free rotation around the carbon bonds would not be expected to be hindered in this way 3.2.1.2 Amberchrom supported resins Due to the poor americium extraction capabilities displayed by the Amberlite based resins the polymer support was switched to Amberchrom CG300 which has a much smaller particle size range of 50–100 μm and lower mean pore diameter of 0.03 μm The loading was increased to 5% (w/w) for Resin since the ligand was no longer in limited supply and this loading better approximated Resin Resin also displayed poor uptake of americium from M nitric acid after 24 h contact time Given the poor uptake despite the change of support to a lower particle size and the now freely available ligand it was decided to prepare resins of 40% (w/w) loading on the Amberchrom support The 40% (w/w) loading was chosen to bring the triazine based resins in line with the standard 40% (w/w) loading for commercially available EXC resins typically used in actinide separations such as TEVA, UTEVA, LN resin, Actinide Resin etc [47] This loading was found to be the maximum capacity for the various organic ligands on Amberchrom used in these EXC resins with further loading leading to significant leaching of ligand from the support into solution during the extraction procedure [47] Batch experiments were utilised to probe the americium extraction capabilities of the 40% (w/w) loaded resins The resins were vortex mixed for 1–60 with M and 0.01 M nitric acid solution containing 50–100 Bq Am-241 Nitric acid was chosen at these concentrations for the reasons previously discussed As can be seen in Fig 3, with a DAm min=50 and a DAm max=170, Resin performed well by comparison to both its SX analogue which is reported to achieve only a DAm on the order of 10 after 60 contact time and also with a covalently bound 14% (w/w) BTBP-silica resin reported by Harwood which did not show any americium extraction from nitric acid in the 0.001–4 M concentration [25] The uncertainties graphed represent the calculated RSD based upon triplicate studies Resin did not perform as well as the BTPhen SX counterpart which is reported to achieve DAm >10 0 within 15 [20,21] and the silica bonded covalent resin (10% w/w) reported by Harwood which is reported to achieve DAm >30 0 within 90 in 0.1 M nitric acid [25] Despite this, the DAm max=540 after 15 contact time in M nitric acid and DAm max=460 after 15 in 0.01 M nitric acid still represent good extraction of americium with >94% of americium was extracted from solution within 10 and >99% within 60 The high DAm values in 0.01 M nitric acid imply that this would not constitute an appropriate back-extraction phase as is the case in the BTPhen SX system The americium extraction capability of Resin was also tested in M and 0.1 M hydrochloric acid and was not competitive with the nitric acid system achieving DAm max=125 ± 11 The Dw values for simulated matrix elements on Resin for all of the elements included were in the range of Dw =10–30 except for cadmium and silver which had DCd max=135 and DAg max=340 after 30 of contact time The affinity of BTPhen for cadmium and silver has been previously reported in solvent extraction studies using the ligand [22] The selectivity for americium over lanthanides displayed by the soft N-donor ligands BTBP and BTPhen is commonly attributed to the greater covalency of the 5f orbitals by comparison with the 4f orbitals [20,48,49] Care must be taken with the definition of covalency in this context since early actinides display greater covalency due to the relative radial extension of the 5f valence orbitals The valence orbitals of the minor actinides such as americium however are more contracted and computational calculations suggest that selectivity for An(III) over Ln(III) by soft N-donor ligands is likely due to a better energy match between metal and ligand orbitals [50] 3.2.1.1 Amberlite supported resins The first resins synthesised in this work were based upon the impregnation of BTBP and BTPhen into high purity Amberlite XAD7 at a loading of 3.5% (w/w) as described in Section 2.2 The loading of 3.5% was chosen for these resins to closely resemble the loading of the covalently bound resin that has been previously reported by the Heath group [26] (Resin 8) Resin had a nominal loading of 5% but this was lowered to 3.5% due to the limited availability of ligand at the time of this study The slight deviation in ligand loadings was not considered to be of detriment to the comparison since the ligand loading represented a large theoretical excess of ligand to americium used in these separations The Amberlite substrate represents a commonly used polymer support in the production of EXC resins [28,31,33,35,45] and has a particle size of 560–710 μm which matches the particle size of Resin [26] Amberlite is also chemically inert and stable in the systems of interest The extraction and separation capabilities of Resin and Resin were tested by vortex mixing experiments in which 100 mg of resin was contacted with M and 0.01 M nitric acid containing yttrium, europium and americium Nitric acid was chosen at these concentrations as they represent the extraction and backextraction phases respectively for the analogous BTBP/BTPhen solvent extraction (SX) system which consists of the BTBP/BTPhen ligand (0.01 M) in a 1-octanol diluent [20–22] Yttrium and europium were chosen as they are commercially available radiotracers for the elements that can be conveniently counted by gamma spectroscopy, and they represent realistic contaminants that may be found in environmental/nuclear forensics samples Europium is the commonly used test case for americium/lanthanide separations in the literature, often being considered the lanthanide ‘analogue’ of americium due to europium’s similar electronic configuration and ionic radii [46] Resin showed no affinity for americium even after 24 h of contact time at either acid concentration This agrees with the results reported by Harwood [25] covered in Section 1.1 The analogous BTBP SX system however displays a DAm of ca 10 after 60 of contact time [25] meaning that the BTBP Amberlite resin underperformed by comparison Resin showed some affinity for americium within the same period with a DAm value of 42 ± and 94 ± in M and 0.01 M and nitric acid respectively however in both cases there was significant co-extraction of europium resulting in modest separation factors of ± and 24 ± The analogous BTPhen SX system is reported to achieve DAm >10 0 within 15 [20,21] and SFAm/Eu >400 [20] whilst the silica bonded covalent resin (10% w/w) reported by Harwood is reported to achieve DAm >30 0 within 90 in 0.1 M nitric acid [25] The poor extraction kinetics observed in the case of the BTPhen Amberlite resin, despite the large theoretical excess of ligand to metal, may be caused by sub-optimal orientation of the adsorbed ligand onto the Amberlite support Only ligands that present the binding pocket to the solution are likely to be capable of metal extraction and it may be that the 560–710 μm particle size and corresponding 0.04 μm mean pore diameter of this support are not conducive to providing this configuration with high enough availability at the loading of 3.5% (w/w) It is noted that Horwitz et al reports pore diameter as a key consideration when immobilising an extractant across similar polymer supports [17] Resin 8, which successfully extracted americium under similar conditions despite its 5% (w/w) loading, supports this conclusion as the lig5 J Mahmoud, M Higginson, P Thompson et al Journal of Chromatography A 1669 (2022) 462950 Fig Weight distribution ratios as a function of contact time for americium and simulated matrix elements Fig Elution profiles for americium and simulated matrix elements on Resin columns 3.2.2 Column studies A column separation of americium from the simulated matrix was performed using Resin and the elution profile of the column is displayed in Fig 4a Significant amounts (46–54%) of simulated matrix elements passed straight through the column in the loading fraction with the exception of cadmium and silver which were strongly retained on the column whilst 27.6% of the americium eluted in the loading fraction The americium on the column was strongly retained until a small amount (ca 3%) was eluted across fractions 16–18 by 0.1 M HCl Elution with 15 mM TBP solution stripped 5.5% of the bound americium from the column across fractions 19–21 The DF for americium from simulated matrix elements in the highest americium containing fraction (fraction 20) which contained 2.7% of the americium initially loaded onto the column fell short of the target of DF > 10 0 for americium over lanthanides at DF =60 This was driven by the poor recovery of americium and high coelution of lanthanides by the use of the TBP stripping agent Total americium recovery from the column was 38.9% Gamma spectroscopy of the column confirmed that the remainder of the americium was retained on the column An alternative elution profile shown in Fig 4b maintained the loading fraction at M nitric acid before 11 fractions of M HCl were used to elute the lanthanides from the column Americium was retained on the column during these elutions The column was rinsed with 15 mM TEDGA solution and 52% of the americium initially added to the column was recovered across frac- tions The calculated DF for americium based on fraction 13, which contained the highest proportion of americium, (28%) are shown in Fig This method produced DF values that were in line with or greater than the target value of DF >10 0 for americium over lanthanides Fig 5a displays the elution profile for an americium separation from simulated matrix elements based upon a column separation using Resin There was 100% retention of americium on the column in the loading fraction whilst 50–53% of beryllium, strontium, caesium, barium and yttrium passed straight through the column with a further 16–22% of these elements eluted cumulatively across the elution profile Lanthanides were strongly retained on the column until the application of 0.1 M HCl Terbium was an exception as 11% passed straight through in the loading fraction Elution of 15– 31% of lanthanides was observed across the elutions with 0.1 M HCl A small amount of americium coelution was observed across the 0.1 M HCl fractions with a total of 7% americium eluted across the fractions Application of 15 mM TBP eluent led to a total americium recovery of 89% of the total americium applied to the column across 10 fractions The DF for americium from lanthanides achieved by this column separation was insufficient at DF =10–20 As may have been expected from the weight distribution ratios observed in the batch experiments both cadmium and silver were both strongly retained on the column, with a total eluted recovery of only 3.6% and 8.2% respectively demonstrating that the BTPhen J Mahmoud, M Higginson, P Thompson et al Journal of Chromatography A 1669 (2022) 462950 Fig Elution profiles for americium and simulated matrix elements on Resin columns clear fuel, environmental, and nuclear forensics samples within the desired 24 hour timescale A CyMe4 BTPhen resin (Resin 6) of 40% (w/w) loading with an Amberchrom support showed good extraction of americium from nitric acid solutions achieving a maximum weight distribution ratio (DAm ) of 540 within 15 of contact time The same resin achieved decontamination factors in the range of 60–160 for americium over lanthanides by column chromatography A CyMe4 BTBP resin (Resin 4) of 40% (w/w) loading on an Amberchrom support achieved maximum also showed good extraction of americium from nitric acid achieving a maximum weight distribution ratio (DAm ) of 170 within 60 Decontamination factors of >10 0 were attained for several interferences including many lanthanides by column chromatography This work has demonstrated a rapid, cheap and easy methodology for the generation of extraction chromatography resins from commercially available, relevant extractants and support materials Resins can be easily prepared on inert supports and the process controlled using analytical techniques The resins can then be applied to fundamental radiochemical studies to establish key performance metrics Future work will focus upon the optimisation of this method by further investigation into other promising americium/lanthanide selective ligands and the optimisation of separation and recovery of americium by characterising the affinity of the resins with a greater range of acids and stripping phases Fig Decontamination factors for americium from lanthanides on Resin and Resin columns resin may be valuable as a rapid filtration method for these elements Fig 5b shows the elution profile based upon repeated HCl washes for the alternative column separation scheme using Resin as detailed above The strategy of removing the lanthanides by repeated HCl washes prior to stripping the americium with TBP dramatically improved the DF of americium over most elements as is shown in Fig The lanthanide elements however did not meet the target of DF >10 0 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 Conclusion Joe Mahmoud: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing – original draft, Writing – review & editing, Visualization Matthew Higginson: Conceptualization, Validation, Investigation, Data curation, Writing – review & editing, Supervision, Project administration, Funding acquisition Paul Thompson: Conceptualization, Writing – review & editing, Supervision, Project administration, Funding acquisition Christopher Gilligan: Conceptualization, Methodology, Investigation, Validation, Data curation Francis Livens: Resources, Writing – review & editing, Supervision, Project administration, Funding acquisition Scott L Heath: Conceptualization, Resources, Data curation, Writing – review & editing, Supervision, Project administration, Funding acquisition Several extraction chromatography resins synthesised by the solvent impregnation of CyMe4 BTBP and CyMe4 BTPhen into Amberlite XAD7 and Amberchrom CG300 have been reported The prepared resins have been well characterised both for ligand loading and homogeneity of distribution of ligand across the support material by a suite of analytical techniques including IR spectroscopy, elemental (CHN) analysis, SEM imaging, and elemental mapping Resins of 3.5–5% (w/w) loading based on Amberlite and Amberchrom were found to be ineffective for americium extraction and separation from lanthanides and other elements common in nu7 J Mahmoud, M Higginson, P Thompson et al Journal of Chromatography A 1669 (2022) 462950 Acknowledgement [23] A Geist, C Hill, G Modolo, M.R.S.J Foreman, M Weigl, K Gompper, M.J Hudson, [2, ] bipyridine, an effective extracting agent for the separation of Americium (III) and Curium (III) from the Lanthanides, 6299 (2007) https://doi.org/10.1080/07366290600761936 [24] A Afsar, L.M Harwood, M.J Hudson, P Distler, J John, Effective separation of Am(iii) and Eu(iii) from HNO3 solutions using CyMe4-BTPhen-functionalized silica-coated magnetic nanoparticles, Chem Commun (2014) 15082–15085, doi:10.1039/c4cc07478e [25] A Afsar, P Distler, L.M Harwood, J John, J Westwood, Extraction of minor actinides, lanthanides and other fission products by silica-immobilized BTBP/BTPhen ligands, Chem Commun 53 (2017) 4010–4013, doi:10.1039/ c7cc01286a [26] M.A Higginson, O.J Marsden, P Thompson, F.R Livens, S.L Heath, Separation of americium from complex radioactive mixtures using a BTPhen extraction chromatography resin, React Funct Polym 91–92 (2015) 93–99, doi:10.1016/j reactfunctpolym.2015.05.002 [27] A Afsar, J Westwood, P Distler, L.M Harwood, S Mohan, J John, F.J Davis, Separation of Am(III), Cm(III) and Eu(III) by electro-spun polystyreneimmobilized CyMe4-BTPhen, Tetrahedron 74 (2018) 5258–5262, doi:10.1016/ j.tet.2018.04.037 [28] A.G Strikovsky, K Jerˇábek, J.L Cortina, A.M Sastre, A Warshawsky, Solvent impregnated resin (SIR) containing dialkyl dithiophosphoric acid on Amberlite XAD-2: extraction of copper and comparison to the liquid-liquid extraction, React Funct Polym 28 (1996) 149–158, doi:10.1016/1381-5148(95)0 0607 [29] J.L Cortina, A Warshawsky, Developments in solid-liquid extraction by solvent-impregnated resins, ChemInform (2010) 28, doi:10.1002/chin 199752337 [30] N Kabay, J Luis, A Trochimczuk, M Streat, Reactive & functional polymers solvent-impregnated resins (SIRs) – Methods of preparation and their applications, React Funct Polymers 70 (2010) 484–496, doi:10.1016/j reactfunctpolym.2010.01.005 [31] J.L Cortina, N Miralles, A.M Sastre, M Aguilar, A Profumo, M Pesavento, Solvent-impregnated resins containing di-(2,4,4-trimethylpentyl) phosphinic acid Study of the distribution equilibria of Zn (II), Cu(II) and Cd(II), Reactive Polymers 21 (1993) 103–116 [32] P Taylor, M.S Hosseini, M Hosseini, A Hosseini, Solvent Impregnated Resins containing Quinizarin : preparation and Application to Batch - mode Separation of Cd (II), Cu (II), Ni (II), and Zn (II) in aqueous media prior to the determination by flame atomic absorption spectrometry, Sep Sci Technol 42 (2007) 3465–3480, doi:10.1080/01496390701626552 [33] J.L Cortina, N Miralles, A Sastre, M Aguilar, A Profumo, M Pesavento, Solvent impregnated resins containing Cyanex 272 Preparation and application to the extraction and separation of divalent metals, 18 (1992) 67–75 [34] Y Tang, S Bao, Y Zhang, L Liang, Effect of support properties on preparation process and adsorption performances of solvent impregnated resins, React Funct Polym 113 (2017) 50–57, doi:10.1016/j.reactfunctpolym.2017.02 006 [35] J.L Cortina, N Miralles, M Aguilar, A.M Sastre, Solvent impregnated resins containing Di-(2-Ethylhexyl) phosphoric acid - preparation and study of the retention and distribution of the extractant on the resin, Solvent Extr Ion Exch 6299 (2007) 349–369, doi:10.1080/07366299408918214 [36] A Afsar, P Distler, L.M Harwood, J John, J.S Babra, Z Selfe, J Cowell, J.S Babra, Z.Y Selfe, J Westwood, Separation of minor actinides from lanthanides using immobilized ligand systems: the role of the Counterion, Heterocycles 99 (2018) 3–10, doi:10.3987/com- 18- s(f)71 [37] E.R Bertelsen, J.A Jackson, J.C Shafer, E.R Bertelsen, J.A Jackson, J.C Shafer, A Survey, A survey of extraction chromatographic f -element separations developed by E P Horwitz, Solvent Extr Ion Exch 38 (2020) 1–39, doi:10.1080/ 07366299.2020.1720958 [38] M.L Dietz, E.P Horwitz, A.H Bond, Extraction Chromatography : Progress and Opportunities, Chemistry Division, Argonne National Laboratory, 1997 [39] F.W.E Strelow, R Rethemeyer, C.J.C Bothma, Ion exchange selectivity scales for cations in nitric acid and sulfuric acid media with a sulfonated polystyrene resin, Anal Chem 37 (1965) 106–111, doi:10.1021/ac60220a027 [40] D.R Mcalister, E.P Horwitz, Characterization of extraction of chromatographic materials containing Bis (2-ethyl-1-hexyl) phosphoric acid, and Bis (2,4,4Trimethyl-1-Pentyl) phosphinic acid, Solvent Extr Ion Exch 6299 (2007) 757– 769, doi:10.1080/07366290701634594 [41] N Gharibyan, A Dailey, D.R McLain, E.M Bond, W.A Moody, S Happel, R Sudowe, A Walter, Extraction behavior of americium and curium on selected extraction chromatography resins from pure acidic matrices, Solvent Extr Ion Exch 32 (2014) 391–407, doi:10.1080/07366299.2014.884888 [42] A Afsar, J Cowell, P Distler, L.M Harwood, J John, J Westwood, Synthesis of Novel BTPhen-Functionalized Silica-Coated magnetic nanoparticles for separating trivalent actinides and lanthanides, Synlett 28 (2017) 2795–2799, doi:10.1055/s- 0036- 1590865 [43] M.L Dietz, E.P Horwitz, L.R Sajdak, R Chiarizia, An improved extraction chromatographic resin for the separation of uranium from acidic nitrate media, Talanta 54 (2001) 1173–1184 [44] D.C Harris, C.A Lucy, Quantitative Chemical Analysis, 9th ed., WH Freeman, 2015 [45] E.P Horwitz, M.L Dietz, R Chiarizia, H Diamond, A.M Essling, D Graczyk, Separation and preconcentration of uranium from acidic media by extraction chromatography, Anal Chim Acta 266 (1992) 25–37, doi:10.1016/0 03-2670(92) 85276-C Funding for this project was provided by AWE and EPSRC via a studentship to JM through the Next Generation Nuclear Centre for Doctoral Training, The University of Manchester Supplementary materials Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.chroma.2022.462950 References [1] K.L Nash, C Madic, J.N Mathur, J Lacquement, Actinide separation science and technology, Chem Actinide Transactinide Element (2010) 2622–2798, doi:10 1007/978- 94- 007- 0211- 0_24 [2] T Kooyman, Current state of partitioning and transmutation studies for advanced nuclear fuel cycles, Ann Nucl Energy 157 (2021) 108239, doi:10.1016/ j.anucene.2021.108239 [3] F.R Livens, Evaluation of methods for the radiometric measurement of Americium-241 in environmental samples, Analyst 114 (1989) 1097–1101, doi:10.1017/CBO9781107415324.004 [4] K.J Moody, I.D Hutcheon, P.M Grant, Nuclear Forensic Analysis, 2nd ed., CRC Press, 2014 [5] E.M González-Romero, Impact of partitioning and transmutation on the high level waste management, 241 (2011) 3436–3444 https://doi.org/10.1016/j.nucengdes.2011.03.030 [6] M Salvatores, Nuclear fuel cycle strategies including partitioning and transmutation, 235 (2005) 805–816 https://doi.org/10.1016/j.nucengdes.2004.10.009 [7] M Nilsson, K.L Nash, A review of the development and operational characteristics of the TALSPEAK process, Solvent Extract Ion Exchange 6299 (2007) 665–701, doi:10.1080/07366290701634636 [8] J Veliscek-Carolan, Separation of actinides from spent nuclear fuel: a review, J Hazard Mater 318 (2016) 266–281, doi:10.1016/j.jhazmat.2016.07.027 [9] J Magill, V Berthou, D Haas, J Galy, R Schenkel, H.W Wiese, G Heusener, J Tommasi, G Youinou, Impact limits of partitioning and transmutation scenarios on the radiotoxicity of actinides in radioactive waste, Nucl Energy 42 (2003) 263–277, doi:10.1680/nuen.42.5.263.37622 [10] P.E Warwick, I.W Croudace, R Carpenter, Review of analytical techniques for the determination of Americium-241 in soils and sediments, Appl Radiat Isot 47 (1996) 627–642, doi:10.1016/0969-8043(96)0 023-1 [11] Y Chen, Z Chang, Y Zhao, J Zhang, J Li, F Shu, Studies on the age determination of trace plutonium, J Radioanal Nucl Chem (2009) 675–678, doi:10.1007/s10967- 009- 0056- [12] U Nygren, H Ramebäck, C Nilsson, Age determination of plutonium using inductively coupled plasma mass spectrometry, 272 (2007) 45–51 https://doi.org/10.1007/s10967-006-6780-9 [13] B.H.T Zhang, F.R Zhu, J Xu, Y.H Dai, D.M Li, X.W Yi, L.X Zhang, Y.G Zhao, Age determination of plutonium material by alpha spectrometry and thermal ionization mass spectrometry, 331 (2008) 327–331 https://doi.org/10.1524/ract.2008.1499 [14] F.M.C Treaty, N Treaty, Verification of a fissile Material Cut-Off treaty, (1997) [15] J Lehto, X Hou, Radionuclides in the Environment Nuclear and Radiochemistry, Wiley-VCH, 2011 [16] S Siekierski, Theoretical aspects of extraction chromatography, J Chromatogr Lib (1975) 1–16 [17] E.P Horwitz, D.R Mcalister, M.L Dietz, E.P Horwitz, D.R Mcalister, M.L.D Extraction, M.L Dietz, Separation science and technology extraction chromatography versus solvent extraction: how similar are they? Separat Sci Technol 41 (2007) 2163–2182, doi:10.1080/01496390600742849 [18] E.P Horwitz, M.L Dietz, R Chiarizia, H Diamond, S.L Maxwell, M.R Nelson, Separation and preconcentration of actinides by extraction chromatography using a supported liquid anion exchanger: application to the characterization of high-level nuclear waste solutions, ACTA Anal Chimica Acta 310 (1995) 63– 78, doi:10.1016/0 03-2670(95)0 0144-O [19] M Nilsson, S Andersson, F Drouet, C Ekberg, M Foreman, M Hudson, J.O Liljenzin, D Magnusson, G Skarnemark, Extraction properties of 6,6 -Bis-(5,6dipentyl-[1,2,4] triazin-3-yl)-[2,20]bipyridinyl (C5-BTBP), Solvent Extr Ion Exch 24 (2006) 299–318, doi:10.1080/07366290600646947 [20] F.W Lewis, L.M Harwood, M.J Hudson, M.G.B Drew, J.F Desreux, G Vidick, N Bouslimani, G Modolo, A Wilden, M Sypula, T.H Vu, J.P Simonin, Highly efficient separation of actinides from lanthanides by a Phenanthroline-Derived Bis-triazine ligand, J Am Chem Soc 133 (2011) 13093–13102, doi:10.1021/ ja203378m [21] F.W Lewis, L.M Harwood, M.J Hudson, M.G.B Drew, A Wilden, M Sypula, G Modolo, T.-.H Vu, J.-.P Simonin, G Vidick, N Bouslimani, J.F Desreux, From BTBPs to BTPhens: the effect of ligand pre-organization on the extraction properties of quadridentate Bis-Triazine ligands, Procedia Chem (2012) 231–238, doi:10.1016/j.proche.2012.10.038 [22] M.A Higginson, P Thompson, O.J Marsden, F.R Livens, L.M Harwood, F.W Lewis, M.J Hudson, S.L Heath, Rapid selective separation of americium/curium from simulated nuclear forensic matrices using triazine ligands, Radiochim Acta 103 (2015) 687–694, doi:10.1515/ract- 2015- 2403 J Mahmoud, M Higginson, P Thompson et al Journal of Chromatography A 1669 (2022) 462950 [46] N Vajda, CK Kim, Determination of 241 Am isotope: a review of analytical methodology, J Radioanal Nucl Chem 284 (2010) 341–366, doi:10.1007/ s10967-010-0475-y [47] C Pin, J Rodriguez, Separation Methods Based on Liquid-Liquid Extraction, Extraction Chromatography, and Other Miscellaneous Solid Phase Extraction Processes, 2nd ed., Elsevier Ltd., 2013, doi:10.1016/B978- 0- 08- 095975- 7.01409- [48] F.W Lewis, L.M Harwood, M.J Hudson, M.G.B Drew, V Videva, V.Véronique Hubscher-Bruder, BTBPs versus BTPhens: some reasons for their differences in properties concerning the partitioning of minor ac- tinides and the advantages of BTPhens, Inorg Chem 52 (2013) 4993–5005, doi:10.1021/ic3026842 [49] M.J Hudson, L.M Harwood, D.M Laventine, F.W Lewis, Use of soft heterocyclic N-donor ligands to separate actinides and lanthanides, Inorg Chem 52 (2013) 3414–3428, doi:10.1021/ic3008848 [50] N Kaltsoyannis, Does covalency increase or decrease across the actinide series? Implications for minor actinide partitioning, Inorg Chem 52 (2013) 3407–3413, doi:10.1021/ic3006025 ... leave americium, rather than removing americium at the start of these separation schemes Extraction chromatography (EXC) is based upon the same principles as solvent extraction (SX) but the separation. .. and simplest approach to rapid separations of americium from complex matrices provided that a suitably efficient and selective extractant can be devised The efficacy of the triazine ligands CyMe4 BTBP... Moody, S Happel, R Sudowe, A Walter, Extraction behavior of americium and curium on selected extraction chromatography resins from pure acidic matrices, Solvent Extr Ion Exch 32 (2014) 391–407,