Synthesis and Characterization of Hydrous Zirconia as an Ion-exchanger for Removal of Radioactive Iodine

In terms of nuclear waste management, the behavior of radionuclides with long half-lives, such as I-129, is of special concern especially for the final depository of nuclear waste. In addition, generally speaking, iodine is highly mobile and easily transferable to the natural environment. Furthermore, because iodine is an essential element for the synthesis of thyroid hormones, it accumulates in the human thyroid. Thus, radioactive iodine can also be the greatest potential danger of dose uptake for humans. Among many kinds of iodine species, it is rather challenging to separate iodate selectively from other anions and thus it is necessary to investigate new materials which can adsorb iodate efficiently for the removal of radioactive iodine. In this study, the iodate adsorption ability of hydrous zirconia has been investigated. Hydrous zirconia has been reported as an anion-exchanger, and because of its stability, this material is a promising candidate for selective iodate removal from radioactive waste solutions. White solid of hydrous zirconia was successfully synthesized with an amorphous structure. Its surface showed a character in between amphoteric and basic. The isotherm indicated that the material has a preference to adsorb iodate and the saturation value of adsorption was estimated to 1.8 mmol/g. The material showed lower uptakes as pH got higher. Among several competing anions tested, divalent sulphate ions suppressed the iodate adsorption to some extent due to higher affinity to the material surface. In a basic environment, boric acid also suppressed strongly the adsorption probably because of the formation of tetrahydroxyborate with hydroxide sites on the material surface. These suppressions of iodate adsorption became stronger as the concentration got higher. Post-heating at 400 °C resulted in the transformation of the material structure to tetragonal and a slight improvement of iodate adsorption rate. As the temperature of post-heating got higher, the structure became more monoclinic and showed the lower uptakes, which may be due to the loss of hydroxide sites. A column setup of the material with simulant of wastewater from Fukushima Daiichi Nuclear Power Plant has been operating and approximately 11,000 bed-volume of the solution has been gone through, but still, the column is yet to reach a 100% breakthrough. Based on the results presented in this study, it can be concluded that synthesized hydrous zirconia showed clear iodate preference and a possible high performance for the waste treatment from nuclear power plants

The effect of phosphonates on lanthanide separation for surface-grafted porous zirconia

The effect of phosphonate groups on selective lanthanide sorption for a series of inorganic-organic hybrid materials was investigated. Four functional ligands with an increasing number of aminomethylenephosphonate groups were attached to the porous zirconia matrix via the post-synthetic grafting method. Successful surface grafting was confirmed by FTIR and P-31 MAS-NMR spectroscopies. All the synthesized hybrids showed a lanthanide uptake of about 100 mu mol g(-1) at pH 3. The sorption studies revealed that the hybrids of ligands with a larger number of phosphonate groups possess higher selectivity, as one with the largest number showed a separation factor of over 80 for La3+ and Lu3+. Fixed-bed column experiments also demonstrated the materials' favored uptake of Lu3+ over La3+ at pH 3, in addition to the reusability and applicability to the actual separation settings. These results propose strategies for the selection of organic ligands for hybrid sorbent synthesis.Peer reviewe

Anion exchange on hydrous zirconium oxide materials: application for selective iodate removal

The radioactive 129I is a top-priority radionuclide due to its the long half-life (1.57 × 107 years) and high mobility. Because of the planned and accidental releases to the environment, specific separation technologies are required to limit the potential radiation dose to human beings. Zirconium oxides are known for their adsorption capability and selectivity to oxyanions and here the applicability to selective IO3− removal has been investigated regarding the uptake mechanism, regeneration and competition caused by other anions, like environmentally relevant SO42−. Granular aggregates of hydrous zirconium oxides with and without Sb doping showed high potential for the selective IO3− removal in the presence of competing anions, like the forementioned SO42− (apparent capacity between 0.1–0.4 meq g−1 depending on SO42− concentration). The main uptake mechanism was found to be outer-sphere complexation (ion-exchange) to the protonated hydroxyl groups of hydrous zirconium oxides, but also minor mechanisms were identified including inner-sphere complexation and reduction to I−. The materials were observed to be easily and successively regenerated using dilute acid. Hydrous zirconium oxides showed high potential for IO3− removal from waste solutions regarding technical (high selectivity and apparent capacity) and ecological/economic (feasible regeneration) aspects.The radioactive I-129 is a top-priority radionuclide due to its the long half-life (1.57 x 10(7) years) and high mobility. Because of the planned and accidental releases to the environment, specific separation technologies are required to limit the potential radiation dose to human beings. Zirconium oxides are known for their adsorption capability and selectivity to oxyanions and here the applicability to selective IO3- removal has been investigated regarding the uptake mechanism, regeneration and competition caused by other anions, like environmentally relevant SO42-. Granular aggregates of hydrous zirconium oxides with and without Sb doping showed high potential for the selective IO3- removal in the presence of competing anions, like the forementioned SO42- (apparent capacity between 0.1-0.4 meq g(-1) depending on SO42- concentration). The main uptake mechanism was found to be outer-sphere complexation (ion-exchange) to the protonated hydroxyl groups of hydrous zirconium oxides, but also minor mechanisms were identified including inner-sphere complexation and reduction to I-. The materials were observed to be easily and successively regenerated using dilute acid. Hydrous zirconium oxides showed high potential for IO3- removal from waste solutions regarding technical (high selectivity and apparent capacity) and ecological/economic (feasible regeneration) aspects.Peer reviewe

Associations between clinical neck symptoms and various evaluations ofcervical intervertebral disc degeneration by magnetic resonance imaging

Purpose: Magnetic resonance imaging (MRI) is widely used to evaluate intervertebral disc degeneration. Recently, various evaluations of cervical disc degeneration using MRI have been conducted, but there is no gold standard. The purpose of this study was to compare the reproducibilities of previously reported classifications for evaluating cervical disc degeneration by MRI and their associations with clinical symptoms. Participants and methods: A total of 582 subjects underwent conventional MRI of the cervical spine. Disc degeneration was assessed in each intervertebral disc from C2/3 to C7/T1 using five different classifications: Matsumoto's grading system, Miyazaki's grading system, Nakashima's grading system, Jacobs' grading system, and Suzuki's grading system. MR images of 30 participants were used, and Cohen's kappa coefficient of agreement of each classification was calculated for intra-observer and inter-observer reliabilities. These five classifications of disc degeneration and changes of vertebral endplates were measured, and associations with clinical symptoms were assessed. Results: Kappa (κ) values of intra-observer agreement were higher for Jacobs' classification, whereas those of inter-observer agreement were higher for Nakashima's and Jacobs' classifications than for other classifications. The prevalences of neck pain and shoulder stiffness were 27.4% and 41.9%, respectively. There were no associations for any classifications of disc degeneration and Modic types with neck pain or shoulder stiffness. Only the presence of Schmorl's nodes was associated with neck pain. Conclusion: At present, there is no specific classification for cervical disc degeneration associated with clinical symptoms. Vertebral endplate changes might be associated with clinical symptoms. It may be necessary to create a new classification for better reproducibility of the evaluation of cervical disc degeneration

A simple method for quantifying iodate and iodide fractions in solution using Ag+-impregnated activated carbon

The speciation of iodine in environment must be known in order to properly assess its geological fate and to study potential remediation materials for the decontamination of water containing radioactive iodine. In this study, the utilization of silver-impregnated granular activated carbon for separation between two iodine species, iodate and iodide, from each other was studied in different solution matrices with batch and column experiments. A high separation of the iodine species was achieved in the high concentrations of interfering ions, e.g. chloride, and in both mu M and trace iodine concentrations. The method is suitable for both radioactive and non-radioactive iodine.Peer reviewe

Natural radioactivity of residues from groundwater treatment facilities in Finland

The accumulation of naturally occurring radionuclides in solid residues was investigated from groundwater treatment facilities (GTFs) in Finland. Natural radionuclides U-238, Ra-226, Pb-210 and Ra-228 were found in various precipitates, sludges and filters at concentrations exceeding the general clearance level of 1 kBq kg−1 used for solid materials in the European directive 2013/59/Euratom. The accumulation of natural radionuclides in different solid residues was observed even when the activity concentrations in the untreated groundwater were relatively low, and when there was no measurable change in the concentrations between raw and treated groundwater within analytical uncertainties. Based on mass and activity balance considerations this is thought to be due to the large volumes of treated water per year. The exposure of workers to natural radiation from solid residues in the regular use of a groundwater facility was found not to be likely to exceed 0.3 mSv a−1 if the activity concentrations are <10 kBq kg−1 for U-238, Ra-226, Pb-210 and Ra-228. The worker exposure from solid residues is therefore likely to remain below the reference level of 1 mSv a−1, and indoor radon is more of a concern for the radiation protection of workers at GTFs. However, the natural radionuclide content in the different solid residues from groundwater treatment needs to be characterised properly to be able to ensure safety in the final use of the residues with respect to the potential exposure of the public

Schematic representation of the mechanism by which MFG-E8 deficiency is associated with the enhanced production of IgM Abs that specifically recognize the ONE-modified proteins and phosphatidylserine exposed on the outer leaflet of the apoptotic cell membranes.

<p>Note that the possibility of the presence of ONE-derived epitopes in apoptotic cells cannot be eliminated.</p

Presence of ONE-specific IgM antibodies in the MFG-E8^−/− mice.

<p>(<b>A</b>) Formation of ONE via 4-hydroperoxy-2-nonenal during the peroxidation of ω6 polyunsaturated fatty acids. (<b>B</b>) Separation of MFG-E8^+/+mice sera by gel filtration. The serum was eluted with PBS at the flow rate of 0.5 ml/min at room temperature with monitoring of the absorbance at 280 nm. The column system was composed of Hi Prep 16/60 Sephacryl S-300. The total IgM was determined by a direct antigen ELISA using the anti-IgM antibodies. The anti-ONE IgM titers were determined by a direct antigen ELISA using the ONE-modified BSA as the absorbed antigens. (<b>C</b>) Glomerular immunoglobulin deposition in 60-week-old female MFG-E8^+/+ (WT) and MFG-E8^−/− (KO) mice. Kidney sections were stained with Alexa Fluor 488-conjugated antibody against mouse IgG or IgM. <i>HE</i>: Hematoxylin and Eosin. (<b>D</b>) Cross-reactivity of antibodies eluted from the kidneys of MFG-E8^+/+ (WT) and MFG-E8^−/− (KO) mice. The IgM titer of the antibodies was determined by a direct antigen ELISA using native BSA, ONE-treated BSA, and DNA as the absorbed antigens. In panels B and C, the results are representative of three separate experiments with similar results. In panel D, the results represent the means ± SD of three separate experiments performed in duplicate determinations. There were no statistically significant differences between WT and KO groups.</p

Characterization of ONE-specific IgM mAbs.

<p>(<b>A</b>) Cross-reactivity of the ONE-specific IgM mAbs established from the MFG-E8^−/− mice. The IgM titer of the mAbs was determined by a direct antigen ELISA using dsDNA and native and aldehyde-modified BSA as the absorbed antigens. The results represent the means ± SD of three separate experiments performed in duplicate determinations. Asterisks indicate a significant difference between BSA and ONE-modified BSA groups: *, P<0.05; **, P<0.01; ***, P<0.001. Differences were analyzed by the unpaired two-tailed Student’s t test. (<b>B</b>) Sequence alignment of the hypervariable regions of ONE-specific IgM mAbs prepared from female MFG-E8^−/− mice. CDR1, CDR2, and CDR3 represent the Kabat definition complementarity-determining regions (CDRs). Hyphens (−) indicate sequence gaps, and the dots (•) indicate the sequence not determined. Sequences were aligned using the program CLUSTALW and were manually modified. Accession numbers for the sequences are as follows. Gen Bank: 9E10, CAN87019. Protein data bank: 26-2f, 1H0D; anti-Hiv-1, 1MF2. (<b>C</b>) V region gene use of ONE-specific IgM mAbs. All sequencing analyses were performed at least three times.</p