In nuclear power plants and other nuclear facilities the removal of cobalt from radioactive liquid waste is needed to reduce the radioactivity concentration in effluents. In liquid wastes containing strong organic complexing agents such as EDTA cobalt removal can be problematic due to the high stability of the Co-EDTA complex. In this study, the removal of cobalt from NaNO3 solutions using antimony oxide (Sb2O3) synthesized from potassium hexahydroxoantimonate was investigated in the absence and presence of EDTA. The uptake studies on the ion exchange material were conducted both in the dark (absence of UV-light) and under UV-C irradiation. Ca2+ or Ni2+ were included in the experiments as competing cations to test the selectivity of the ion exchanger. Results show that UV-C irradiation noticeably enhances the cobalt sorption efficiency on the antimony oxide. It was shown that nickel decreased the sorption of cobalt to a higher extent than calcium. Finally, the sorption data collected for Co2+ on antimony oxide was modeled using six different isotherm models. The Sips model was found to be the most suitable model to describe the sorption process. The Dubinin-Radushkevich model was further used to calculate the adsorption energy, which was found to be 6.2 kJ mol−1.

Several metal antimonates MSbO (M = Si, Ti, Mn, Sn) have been studied for the removal of several key radionuclides ( 60 Co, 90 Sr and 137 Cs) from nuclear waste solutions. Special emphasis was the removal of radionuclides from acidic effluents and from effluents of high Ca content. Synthesis and initial screening test indicated that increasing the degree of substitution of other metals (M) for Sb increases the uptake of divalent cations (Sr, Co) in acidic media. Some of the synthesised compounds also showed considerable tolerance for Ca ions in Sr removal. Column tests with granular silicon antimonate gave very good decontamination factors (DF) for 85 Sr (DF up to 10000) and 134 Cs (DF up to 600) in nitric acid solution (0.1 M) and for 57 Co (up to 5000) 85 Sr (up to 3000) in neutral simulated pond water. Precoat tests with manganese antimonate powder gave high decontamination factors for 57 Co (DF up to 600) in simulated NPP floor drain water. In general, the performance of the metal antimonates was considerably better than that of commercial materials (zeolite, titanate, and silicotitanate) that were tested in parallel for

This paper describes the processes used at the Fukushima Daiichi plant, Japan, to purify the waste effluents generated in the cooling of damaged reactors. These include primary cesium removal with the Kurion zeolite system and the SARRY system utilizing silicotitanate to remove radiocesium from water recirculated to reactors for cooling. Another process is the ALPS system to purify the retentates of the reverse osmosis plant to further purify the water from radionuclides after primary cesium separation. In ALPS, a major role is played by the transition metal hexacyanoferrate product CsTreat and sodium titanate SrTreat in the removal of radiocesium and radiostrontium, respectively. The performance of these four exchangers (zeolite, silicotitanate, hexacyanoferrate, and sodium titanate) is critically analyzed with respect to processing capacities and the decontamination factors obtained in the processes. Furthermore, general information on preparation, structure and ion exchange of these ion-exchanger categories is given with additional information on their use in nuclear waste effluent treatment processes. Finally, the importance of selectivity and associated factors are discussed.

From the environmental and end-users’ viewpoints, electrospun ion exchange fibres provide highly efficient and sustainable material for separation of for example trace pollutants, such as radionuclides and heavy metals. This work aimed to reduce the amount of ion exchange material needed per unit volume of raw material subjected to an ion exchange process. We present a very simple process to electrospinning of sodium titanate fibres, but also test results of ion exchange kinetics measurements. Sodium titanate fibres are very promising material and it is possible that by exploiting electrospun inorganic sub-micron fibres the ion exchanger mass required for a given capacity can be decreased significantly.

The purpose of this study was to investigate the separation of Co, Nd and Dy from a ternary Co-Nd-Dy solution using amorphous zirconium phosphate (am-ZrP). Am-ZrP was synthesized by a precipitation method at room temperature and subsequently characterized by Fourier transform-infrared spectrometry, thermogravimetry, scanning electron microscopy, X-ray diffraction, solid-state 31P magic angle spinning nuclear magnetic resonance spectrometry and sodium hydroxide titration (with and without background salt). The ion exchange kinetics of am-ZrP that were determined in ternary 1 mM equimolar solutions at equilibrium pH 2.5. The effect of pH on the adsorption was studied in ternary 1 mM equimolar solutions and the uptakes of the metals increased with increasing pH until approximately pH 3.5. The adsorption isotherms of Co, Nd and Dy were tested in a series of ternary equimolar solution, the total uptake amounted to 4.13 meq/g at pH ~ 3.0. The preference of am-ZrP for these metals occurred in decreasing order Dy > Nd ≫ Co. The separation of Co, Nd and Dy from their 1 mM equimolar ternary mixture was investigated on an am-ZrP column. Effects of loading (7.8%, 62% and 100%) on the separation were compared by measuring the corresponding HNO3 elution fractions. It was found that with a lower metal loading of 7.8%, three clear elution bands were obtained. Am-ZrP exhibited selective separation properties towards the ternary Co-Nd-Dy system, which contribute to the future scale-up studies for the recycling of NdFeB magnets.

Mud Hills clinoptilolite has been used in an effluent treatment plant (SIXEP) at the Sellafield nuclear reprocessing site. This material has been used to remove 134/137Cs and 90Sr successfully from effluents for 3 decades. Samples of the zeolite have been tested in column experiments to determine their ability to remove radioactive Cs+ and Sr2+ ions under increasing concentrations of competing ions, Ca2+, Mg2+, Na+ and K+. These ions caused increased elution of Cs+ and Sr2+. Ca2+, Mg2+ and K+ were more effective competitors than Na+. For Na+, it was found that if concentration was reduced, then column performance recovered rapidly.

Bauxite residue (BR) is an inevitable industrial[GRAPHICS]waste generated through the classic Bayer extraction of alumina from bauxite minerals. It contains relatively significant amount of valuable rare earth elements, including scandium, and therefore, we explored the suitability of trace scandium recovery from BR acid leachate by titanium phosphate (TiP) ion exchangers. Three kinds of TiP materials (amorphous TiP, alpha-TiP, and gamma-TiP) were synthesized through fluorine-free precursors and characterized by chemical analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR), ultraviolet/visible (UV/vis) diffuse reflectance spectrometry, P-31 magic angle spinning (MAS) nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and potentiotnetric titration. The Sc3+ exchange capacities were determined as 1.74, 0.55, and 0.22 mequiv g(-1) for amorphous, alpha-, and gamma-TiP, respectively. Competition of major elements (Fe, Al, Ca) in BR leachate with Sc uptake were studied in batch experiments using binary equimolar mixtures, and the separation factors of Sc/Fe2+, Sc/Al, and Sc/Ca reached magnitudes of 10-1000 on amorphous TiP. The high Sc(3+)selectivity by amorphous TiP was suspected to be the matching of Ti4+ lattice radius with Sc3+ ionic radius (both 0.745 A). Finally, the separation of trace scandium from the simulated BR leachate solution was demonstrated on an amorphous TiP column. The interference of Fe3+ has been partially resolved by on-column reduction using sodium sulphite. The optimized final eluate contained only Sc, Fe, and Al. The concentration ratio of Sc/Fe can be increased by a factor of 8.8 and Sc/Al by 265 through a single cycle of chromatographic separation with an Sc recovery rate of 91.1%.

Solid-phase adsorbents for rare-earth ions are prepared by covalently binding organophosphate ligands on mesoporous silica via a versatile metal(iv)–O–P linkage.

The recovery of Nd and Dy from a ternary Co–Nd–Dy system using layered crystalline zirconium phosphate (α-ZrP) was investigated. α-ZrP was synthesized by the refluxing method, and subsequently characterized by sodium hydroxide titration, Fourier transform-infrared spectrometry, thermogravimetry, scanning electron microscopy, and X-ray diffraction. The selectivity and ion exchange kinetics of the α-ZrP material were determined with regard to the individual elements. The influence of solution pH on the uptake was studied in ternary 1 and 2 mM equimolar solutions. The results showed that in acidic solution (pH 1–3), very little Co was taken up, while Nd and Dy uptakes were at reasonable levels (0.5–0.6 meq/g). The uptake isotherms of Nd, Dy, and Co were measured separately at pH 2.5 and 4.5 in ternary equimolar solution series. At pH 4.5, the loading capacities were about 0.2 meq/g for Co, 1.1 meq/g for Nd, and 1.5 meq/g for Dy. Dy was thus clearly preferred over Nd by α-ZrP. The loading of an α-ZrP column showed a similar preferred pattern. Nitric acid eluent removed Co, Nd, and Dy, but there was no separation of the metals in the eluate. A mixture of nitric and phosphoric acids, however, produced a strong separation. Co was very weakly retained in the column, and the ratio Dy/Nd in the eluent was in the range of 2–7. Thus, the α-ZrP material showed encouraging ion exchange properties for the separation and recycling of Nd and Dy from a ternary Co–Nd–Dy system. Much more work is needed, however, to develop a practical separation flowsheet.

Department of Chemistry – Radiochemistry, 55, Finland. E-mail: Wenzhong.Zhang@hels Department of Chemistry, KU Leuven, Cele Heverlee, Belgium. E-mail: Koen.Binnemans Department of Chemistry, FI-00014 Univers † Electronic supplementary inform characterisations. See DOI: 10.1039/c7ta0 ‡ These two authors contributed equally t § Deceased, September 11, 2017. Cite this: J. Mater. Chem. A, 2017, 5, 23805

Rare earth elements (REEs), composed by all lanthanides plus scandium and yttrium, have found use in modern high-tech applications including permanent magnets, fluorescent lamps and catalytic converters. It is worth noting that certain application of REEs requires ultra-purity of one element despite their shared chemical properties. Separation and purification therefore becomes an important task. Commercially, the REEs are now separated by solvent extraction technology and the high-purity REEs are produced by ion-exchange process. In recent years, the recycling of REEs from industrial waste streams has received more and more attention [1].

Three zirconium phosphate products A, B and C, made through different synthesis routes, were investigated for their europium and americium ion exchange properties utilizing radiotracers Eu-152(3+) and Am-241(3+). Aim of this investigation was to see how material properties change based on different synthesis, and how does the changes effect on trivalent Eu and Am uptake and affinities on the materials. Ultimate goal of an ongoing research is to create inorganic exchanger suitable for separation of trivalent actinides and lanthanides. Powder X-ray diffraction showed that all three products had same a-zirconium phosphate crystal structure. The P:Zr ratio determined by microscope X-ray microanalysis was also the same for all products: 2.43 +/- 0.05. However, infrared absorbance, material acidity, particle morphology, and Eu and Am distribution coefficients differed significantly between products. The intensities of the strong IR absorption at approximately 960 cm(-1), attributed to vibrations of the orthophosphate group, were in descending order B > C > A. Material acidity showed the same descending order B > C > A. First acidity constants pK(al) were 2.3 for product B, 3.1 for C and 3.5 for A. Unit cell volumes increased in the reverse order: B < C < A. Distribution coefficients (K-D), studied for pH 0 to 3 nitric acid media, varied remarkably. For any given pH the K-D descended in the order A > C > B for both Eu and Am. Separation factors, defined as K-D (Eu): K-D (Am), were from 4 to 41 for product A, from 5 to 15 for B, and from 3 to 7 for C. Selectivity coefficients (k(M/H), M = Eu, Am) and sorption strength decreased along with increasing ZrP product acidity. Metal binding coefficients (k(M)) had high values, up to 109, especially in ZrP C and A, while the selectivity coefficients were low, 10-5 to 10(-1), because they relate to the third power of the low pK(al). It was observed that for ZrPs there are strong interdependencies between acidity of the product, unit cell volume, IR absorption, K-D, k(M/H) and k M. Finally, it can be concluded that the ion exchange properties of alpha-ZrP products can be modified considerably by varying their synthesis conditions, perhaps to tailor specific actinide/lanthanide separations.

Antimony oxide was synthesized by a simple method involving the mixing of 6M HCl and antimony pentachloride, adjusting the synthesis pH with 25% ammonia. The obtained material was characterized using X-ray diffraction, field emission scanning electron microscopy, and surface area and pore size analysis. The material structure resembled that of Sb6O13. The cobalt sorption efficiency of the synthesized antimony oxide was tested in the dark and under UV-C irradiation. The 0.01M NaNO3 test solution contained varying concentrations of Co2+ and EDTA and was traced with Co-57. The cobalt concentration in the solutions was determined by gamma spectroscopy. The synthesized material proved to have a high cobalt uptake. In the presence of 20 mu M EDTA, 99.7% of cobalt was removed from the solution after 2 h of UV-C irradiation.

For the modeling of cesium sorption on biotite, samples of natural biotite separated from gneissic rocks were converted into monoionic potassium, sodium, and calcium forms, and sorption isotherms for Cs/K, Cs/Na and Cs/Ca exchange were determined at pH 6 and 8 in 10(-4) 10(-8) M Cs solutions. Selectivity coefficients for Cs/K, Cs/Na, and Cs/Ca ion exchange reactions were calculated from the isotherm data, using the Gaines-Thomas convention. At Cs loadings below 1% of the total ion exchange capacity, the overall selectivity coefficient for Cs/Ca exchange was approximately five and seven orders of magnitude higher than those for Cs/Na and Cs/K exchange, respectively. Based on the selectivity coefficients, the ion exchange isotherms were modeled with the U.S. Geological Survey PhreeqC program, assuming three different types of ion exchange site: sites on the basal planes on biotite crystal surfaces with 95% site abundance, probable interlayer sites on crystal edges [frayed edge sites (FESs)] (0.02%) and third-type sites (5%), the physical background of which is unclear. Of these three types, the FES sites were superior in Cs selectivity, while the planar sites exhibited the lowest selectivity, and the third-type sites had selectivity between these two. The functionality of the model was successfully verified by modeling the Cs sorption isotherms on crushed mica gneiss rock in saline groundwater. Determination of the exchangeable ions K, Na, Ca, and Cs on the basal plane and edge surfaces by scanning electron microscopy-energy-dispersive x-ray spectroscopy (SEM-EDX) supports the results of modeling: edge sites highly prefer Cs ions and also Ca and Na ions but not K ions.

Tin dioxide and its antimony doped counterpart were synthesized using traditional sol–gel procedure. The metal oxides were then turned into composites by mixing them with polyacrylonitrile (PAN) and composite spheres ready for use in traditional column applications were obtained. The characterization of materials was investigated by X-ray diffraction, scanning electron microscopy–energy dispersive X-ray, surface area, point of zero charge and thermal analyses. Static batch experiments showed that the antimony doped tin dioxide–PAN (Sb doped SnO2–PAN) is an effective material for nickel removal and the composite maintains its good metal uptake properties in dynamic column conditions. The composite showed a high nickel uptake capacity of 9 mmol/g in 0.1 M NaNO3 solution. It was observed that the ion exchange kinetics of antimony doped tin dioxide (Sb doped SnO2) was remarkably fast for 57Co and 63Ni ions but turning the material into PAN composite significantly decreased the materials kinetic properties.

Colloidal tin oxide with an average particle size of 3.5 nm, which was ex-situ synthesized by the sol-gel method, has been attached to the surface of amino-functionalized poly(acrylate-co-silane) latex particles with a diameter of 100 nm to yield a composite with selective sorption properties toward Co(2+) ions. Electrokinetic properties and the colloidal stability of the synthesized latex/SnO2 composites have been evaluated in dependence on SnO2 content and pH; the sorption capacity and distribution coefficients of composites for Co(2+) ions were in accordance with the SnO2 content and its sorption performance as an individual compound. Composite coatings obtained by casting latex/SnO2 dispersions on quartz sand spiked with (57)Co radionuclide have efficiently eliminated radionuclides migration from the surface when the SnO2 volume fraction in the film was 3.5-4.7%. Furthermore, at these SnO2 loadings, the composite coatings retained the coherent structure of the original latex coating with SnO2 particles homogeneously distributed over the film thickness. The presence of competing Ca(2+) ions in the leaching media at a concentration of above 0.01 mol/L results in a decrease of the distribution coefficients of the latex/SnO2 composite and significantly higher (57)Co leaching. The value of the distribution coefficient of the sorption material to be used in latex composite coatings to prevent migration of radionuclides shall be close to 10(6) mL/g.

The adsorption of Co(II) by EDTA-modified chitosan was studied in the presence of solution phase EDTA and other interfering species. The increasing amount of EDTA inhibited Co(II) adsorption due to the competition between solution phase and surface bound chelating agents. However, Co(II) removal reached 99% from the solutions where all the Co(II) ions were chelated by EDTA. Oxalate, on the other hand, with considerably lower chelating ability than that of EDTA did not affect the adsorption of Co(II). Furthermore, EDTA–chitosan was effective adsorbent for Co(II) in the simulated decontamination solutions and in the solutions traced with radiocobalt 57Co. Both isotherm and kinetic modeling were conducted for pure and EDTA containing Co(II) solutions and the presence of EDTA clearly affected the obtained results. FTIR- and CE-analysis suggested that EDTA–chitosan was able to capture Co(II) from its dissolved EDTA-chelate. Stability of EDTA–chitosan was confirmed by regeneration and column studies.

New dual functionality scintillating anion-exchange resins were developed for selective determination of (TcO4-)-Tc-99 in various natural freshwater samples. Stable scintillating particles were formed by preparing the vinyl monomer 2-[4-(4'-vinylbiphenylyl)1-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (vPBD), starting with the commercial organic flour TBut-PBD and its subsequent copolymerization with styrene, divinylbenzene, and p-chloromethylstyrene mixture. To integrate the radiochemical separation and radiometric detection steps within the same bead, the chloromethyl groups of the scintillating resins were subjected to amination reactions with dioctylamine (DOA) and trioctylamine (TOA). On-line quantification of (TcO4-)-Tc-99 was achieved by packing the scintillating anion-exchange resin into Teflon tubing for quantification by a flow scintillation analyzer (FSA). The two functionalized resins were selective for pertechnetate over the common anions in natural freshwaters, especially Cl- and SO42- with up to 1000 ppm and with up to 10 ppm 1(-) and Cr2O72-. The uptake efficiency of the TOA sensor decreased from 97.88% to 85.08% in well water and river water, respectively, while the counting efficiency was almost constant (69.50%). The DOA performance showed lower efficiency in the two water types relative to TOA. On the other hand, the DOA sensor could be regenerated by 5 M HNO3 for reuse at least four times without losing its chemical or optical performance. The detection limit was 1.45 Bq which could be achieved by loading 45 mL from well and tap water containing the maximum contaminant level (MCL) of Tc-99 (33 Bq/L). (C) 2013 Elsevier Ltd. All rights reserved.