Affinity and removal of radionuclides mixture from low-level liquid waste by synthetic ferrierites

The affinity and removal efficiency of ¹³⁷Cs⁺, ¹³³Ba²⁺, ⁸⁵Sr²⁺ and ²⁴¹Am³⁺ mixture from aqueous solutions using two synthetic ferrierites HSZ 700KOA and 700KOD commercially used as a catalyst in oil industry were investigated. The uptake of metal ions as a function of different parameters has been studied using batch equilibrium technique. Kinetic curves showed that the equilibrium was mostly reached within 45 min for Cs⁺ and Ba²⁺ and revealed to be longer for Sr²⁺ and Am³⁺. Using Freundlich and Langmuir adsorption isotherms, the results showed that the affinity and adsorption capacity of 700KOA and 700KOD follow the order: Cs⁺ > Ba²⁺ > Sr²⁺ > Am³⁺ with higher values for first material. Both adsorbents exhibited significant high capacity for Cs⁺ relative to other cations giving q _max 1.97 and 1.78 mmol g⁻¹ for 700KOA and 700KOD, respectively. All metals uptake found to be concentration dependant and independent of the pH over 2 to 10 range except Am³⁺; this reveals that the adsorption mechanism is controlled mainly by pure ion exchange reaction for Cs⁺, Ba²⁺, Sr²⁺ and by surface complexation mechanism for Am³⁺. These simple nontoxic materials are recommended to be used for radioactive waste treatment especially fission product ¹³⁷Cs and activation product ¹³³Ba.     

Structural and mechanistic studies on ion insertion into the molecular box {[CpCo(CN)3]4[Cp*Ru]4}

The molecular box [CpCo(CN)₃]₄[Cp*Ru]₄ (Co₄Ru₄) reacts readily with a variety of monocations to form M⊂Co₄Ru₄⁺ (M=K⁺, Cs⁺, Rb⁺). Ion competition experiments, monitored by ESI-MS, show that the molecular box binds the smaller K⁺ more rapidly than Cs⁺, but that thermodynamically Co₄Ru₄ prefers the larger ion. The rates of ion-insertion for K⁺ and Cs⁺ into Co₄Ru₄ were found to qualitatively follow second order kinetics with K⁺, 300 M⁻¹ s⁻¹ and Cs⁺, 36 M⁻¹ s⁻¹. The ratio k_K/k_Cs qualitatively matched the ESI-MS results from ion competition experiments. The rates of ion-insertion into Co₄Ru₄ were found to depend on the counter anions. In particular, RbBF₄ reacted with Co₄Ru₄ more slowly than did RbOTf. The slower rates allowed us to establish second order kinetics. ¹H NMR studies reveal that the Cp signal for Co₄Ru₄ is very sensitive to the presence of entering ions, e.g., Rb⁺, whereas the corresponding Cp signal for Rb⊂Co₄Ru₄⁺ was insensitive to the presence of Rb⁺. The molecular structures of [Co₄Ru₄] · 6MeCN, [K⊂Co₄Ru₄]BF₄ · 7MeCN, [Cs⊂Co₄Ru₄]BF₄ · 6MeCN and [Tl⊂Co₄Ru₄]BF₄ · 6MeCN, determined by X-ray diffraction, showed that although the compounds crystallized in the same space group I23, a correlation exists between the Ru-N/Co-C bond distances and the size of the interstitial ion.     

Behavior and distribution of <Superscript>239+240</Superscript>Pu and <Superscript>241</Superscript>Am in the east coast of Peninsular Malaysia marine environment

The present distributions of ^239+240Pu, ²⁴¹Am and activity ratio of ²⁴¹Am/^239+240Pu in surface seawater of the Peninsular Malaysia east coast were studied. The surface seawater samples were collected at 30 identified stations during the expedition conducted in 2008. ^239+240Pu activity concentrations in surface seawater of the studied area were in the range of 2.33 ± 0.20–7.95 ± 0.68 mBq/m³, meanwhile ²⁴¹Am activity concentrations ranged from MDA to 1.90 ± 0.23 mBq/m³. The calculated activity ratios of ²⁴¹Am/^239+240Pu were varied and disperse distributed with the ranged of 0.12–0.53. The relationships between anthropogenic radionuclide and oceanographic parameters such as turbidity and salinity were examined. The linearly relationships between ^239+240Pu and oceanographic parameters are important for better understanding of its transport processes and behavior in the east coast of Peninsular Malaysia marine environment. Thus, the differ of distribution of ^239+240Pu, ²⁴¹Am and ²⁴¹Am/^239+240Pu in the studied area mainly due to high affinity of ^239+240Pu to associate with sinking particles, mobility nature of ²⁴¹Am, degree of particle reactive of both anthropogenic radionuclides, scavenging and removal process; and others.     

Sorption of radionuclides on natural materials

Information about the sorption of radionuclides on natural materials used for cementation of liquid radioactive wastes (RAW) is important for predictions of migration rates of radionuclides in the products of fixation. Cementation process for conditioning liquid RAW uses, besides cement, materials which improve quality of products. In Czechoslovakia technology among these materials are clinoptilolite tuffit, mordenite tuff, tobermorite and fly ash. Liquid RAW issued from nuclear power plants contains the principal radionuclides⁶⁰Co,¹³⁴Cs and¹³⁷Cs, therefore, a sorption study of these radionuclides was carried out. pH of liquid RAW was 12.5–13.7 and salt content ca. 200 g·dm^–3. Results of sorption are given by distribution coefficients. The best results for cesium in those pH region and salt content had mordenite tuff D_Cs=100 dm³·kg^–1 and the worst results had fly ash D_Cs=4.1 dm³·kg^–1. The best results for cobalt in those solutions had tobermorite D_Co=38 dm³·kg^–1 and the worst results had fly ash D_Co=6.9 dm³·kg^–1.     

Uptake behavior of americium on alginic acid and alginate polymer gels

The uptake behavior of Am³⁺ was investigated by using alginic acid and alginate polymer gels. The affinity of radioactive nuclides for carboxyl groups in gel matrices increased in the order of Na⁺ < Cs⁺ < Co²⁺ < Pd²⁺, Sr²⁺, Fe³⁺ < Eu³⁺, Am³⁺. Among alginate gels, calcium alginate exhibited relatively higher uptake rate and distribution coefficient of Am³⁺. The column packed with calcium alginate beads was effective for the removal of trace amounts of Am³⁺ from acidic nitrate solutions.     

Cellulose scaffolds modulated synthesis of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocrystals: preparation,characterization and properties

Magnetic Co₃O₄ nanoparticles were prepared by using microporous regenerated cellulose films as sacrificial scaffolds. The cellulose macromolecules and the porous structure of the films made them used as spatially confined reacting sites where Co(OH)₂ nanoparticles could be synthesized in situ. When the cellulose matrix was removed by sintering at 500 °C, Co₃O₄ nanoparticles were obtained. XRD and XPS indicated that the prepared nanoparticles were pure Co₃O₄ without any impurity. TEM and SEM images revealed that the particle size of the nanoparticles was smaller than 100 nm. The nanoparticles had weak ferromagnetic properties at 25 °C. Furthermore, the pronounced quantum confinement effects of the synthesized nanoparticles have been observed, the optical bandgap energies determined were about 1.92 ~ 2.12 and 2.74 ~ 2.76 eV for O²⁻ → Co³⁺ and O²⁻ → Co²⁺ charge-transfer processes, respectively. Furthermore, the resulted Co₃O₄ nanoparticles behaved stable electrochemical performance with promising applications in the electrode for lithium ion battery.     

Extraction of actinides and fission products from salt solutions using polyethylene glycols (PEGs)

The extraction behavior of several metal ions viz., Am³⁺, Eu³⁺, UO₂ ²⁺, Th⁴⁺, Sr²⁺ and Cs⁺ was investigated from sulphate medium employing phosphotungstic acid (PTA) and polyethylene glycol (PEG). The influence of various parameters such as pH, PTA concentration, PEG concentration and salt concentration was studied. The order of extraction followed the trend: Am³⁺>Eu³⁺>>Th⁴⁺>UO₂ ²⁺>Sr²⁺>Cs⁺ which deviate significantly from the reported order with conventional solvents. The relatively poor extraction of UO₂ ²⁺, Sr²⁺ and Cs⁺ was ascribed to their lack of interaction with the phosphotungstate anion. The separation behaviour of Am³⁺ vis-a-vis Eu³⁺ was also investigated under different experimental conditions.     

Synthesis of PAN/ferrocyanide composite incorporated with cetrimonium bromide and its employment as a bifunctional adsorbent for coremoval of Cs+ and HCrO4− from aqueous solutions

Polyacrylonitrile/ferrocyanide composite incorporated with cetrimonium bromide (PFICB) was synthesized and evaluated as a novel bifunctional adsorbent for coremoval of Cs⁺ and HCrO₄^?. Results of the reaction time effect showed that adsorption of Cs⁺ and HCrO₄^? onto PFICB were rapid processes. The effect of the solution pH in the range 2.5–10 revealed that PFICB had the ability to simultaneously remove Cs⁺ and HCrO₄^?. The maximum adsorption capacity of PFICB was found to be 41.79 mg/g for Cs⁺ and 19.39 mg/g for HCrO₄^?. These values were compared with those reported in literature using other adsorbents.

     

Sorption of 14C, 99Tc, 137Cs, 90Sr, 63Ni, and 241Am onto a rock and a fracture-filling material from the Wolsong low- and intermediate-level radioactive waste repository, Gyeongju, Korea

Sorption experiments for radionuclides such as ¹⁴C, ⁹⁹Tc, ¹³⁷Cs, ⁹⁰Sr, ⁶³Ni, and ²⁴¹Am were conducted using two different groundwaters (GM-1 and SS-5) and solid materials (granodiorite and fracture-filling material) sampled from the Wolsong low- and intermediate-level radioactive waste (LILW) repository, Gyeongju, Korea. The distribution coefficients of the radionuclides, K _d’s, were obtained and their sorption properties were discussed for each radionuclide. For all sorbing radionuclides, the K _d values for the fracture-filling material were observed to be higher than those for granodiorite regardless of the groundwater. The K _d values were increased in the sequence ⁹⁹Tc < ¹⁴C < ⁹⁰Sr < ¹³⁷Cs < ⁶³Ni < ²⁴¹Am regardless of sorbent types implying that the sorption of radionuclides onto geological media is affected by their chemical behavior in accordance with geochemical environments. Anionic radionuclides such as ¹⁴C and ⁹⁹Tc showed very low K _d values both for the granodiorite and fracture-filling material. The mineralogical composition of the geological media and groundwater conditions was also observed to be important in the sorption of sorbing radionuclides, especially in the case of strongly sorbing radionuclides.     

Extraction of tri- and tetravalent actinides with dihexyl N,N-diethylcarbamoylmethyl phosphonate (DHDECMP) and TBP from nitric acid solutions

Extraction of trivalent (Pu³⁺, Am³⁺, actinides and Eu³⁺, a representative of lanthanides) and tetravalent (Np⁴⁺ and Pu⁴⁺) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP) in combination with TBP in benzene from 2M nitric acid. The stoichiometries of the species extracted were found to be M(NO₃)₃·(3–n) TBP·n DHDECMP (for trivalent ions) and M(NO₃)₄·(2–n) TBP·n DHDECMP (for tetravalent ions) by the slope ratio method. The extraction constants evaluated (from the distribution data) indicate that for tetravalent ions (with solvation number two) the extraction constant increases when TBP (Kh=0.17) molecules are successively replaced by more basic DHDECMP (Kh=0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHDECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu³⁺ and Am³⁺, a lesser decrease being observed for Pu³⁺ (larger ion).     

Paramagnetic behaviour of silver nanoparticles generated by decomposition of silver oxalate

Silver oxalate Ag₂C₂O₄, was already proposed for soldering applications, due to the formation when it is decomposed by a heat treatment, of highly sinterable silver nanoparticles. When slowly decomposed at low temperature (125 °C), the oxalate leads however to silver nanoparticles isolated from each other. As soon as these nanoparticles are formed, the magnetic susceptibility at room temperature increases from −3.14 10⁻⁷ emu.Oe⁻¹.g⁻¹ (silver oxalate) up to −1.92 10⁻⁷ emu.Oe⁻¹.g⁻¹ (metallic silver). At the end of the oxalate decomposition, the conventional diamagnetic behaviour of bulk silver, is observed from room temperature to 80 K. A diamagnetic-paramagnetic transition is however revealed below 80 K leading at 2 K, to silver nanoparticles with a positive magnetic susceptibility. This original behaviour, compared to the one of bulk silver, can be ascribed to the nanometric size of the metallic particles.     

Selective ion exchange onto Slovakian natural zeolites in aqueous solutions

Ion exchange isotherms have been measured and plotted for the uptake of cesium, barium, cobalt, zinc, silver and amonium onto clinoptilolite- and mordenite-rich tuffs of Slovakian origin selectively for both the natural and near homoionic Na form as well, using the radioanalytical determination. The higher quality clinoptilolite-rich tuff has been proven to be effective for a potential radionucleides removal in native form according to the following selectivity sequence: Ag⁺,Ba²,Cs⁺>NH₄ ⁺>Co²⁺, while parent tuff in Na exchanged variety exhibited a little different sequence according to: Ag⁺?>?NH₄ ⁺?>?Ba²⁺?>?Cs⁺. The raw and Na exchanged mordenite-rich tuffs proved subsequently more or less similar selectivity : Ag⁺?>?Zn²⁺?>?Cs⁺, Ba²⁺?>?Co²⁺ and Ag⁺?>?Zn²⁺.     

Facile synthesis of cobalt oxide/reduced graphene oxide composites for electrochemical capacitor and sensor applications

Reduced graphene oxide sheets decorated with cobalt oxide nanoparticles (Co₃O₄/rGO) were produced using a hydrothermal method without surfactants. Both the reduction of GO and the formation of Co₃O₄ nanoparticles occurred simultaneously under this condition. At the same current density of 0.5 A g⁻¹, the Co₃O₄/rGO nanocomposites exhibited much a higher specific capacitance (545 F g⁻¹) than that of bare Co₃O₄ (100 F g⁻¹). On the other hand, for the detection of H₂O₂, the peak current of Co₃O₄/rGO was 4 times higher than that of Co₃O₄. Moreover, the resulting composite displayed a low detection limit of 0.62 μM and a high sensitivity of 28,500 μA mM⁻¹cm⁻² for the H₂O₂ sensor. These results suggest that the Co₃O₄/rGO nanocomposite is a promising material for both supercapacitor and non-enzymatic H₂O₂ sensor applications.     

Simultaneous recovery of plutonium and americium from assorted analytical waste solutions using extraction chromatography

A rapid extraction chromatography based methodology was developed for simultaneous recovery of plutonium and americium from various kinds of analytical waste obtained during chemical quality control of plutonium based nuclear materials using sulphonic acid based actinide? resin. Efforts were made to understand the effect of initial feed acidity, gamma radiation and the concentrations of Am³⁺ and Pu⁴⁺ on their k _d. values. Processing of assorted analytical waste solutions through this method revealed that more than 95 % of Am³⁺ and 90 % of Pu⁴⁺ were adsorbed on the resin while iso- propanol can be successfully employed for the quantitative recovery of both the actinides from the loaded resin phase.     

Macroporous Co3O4 platelets with excellent rate capability as anodes for lithium ion batteries

This paper reports the microwave-assisted synthesis of Co₃O₄ nanomaterials with different morphologies including nanoparticles, rod-like nanoclusters and macroporous platelets. The new macroporous platelet-like Co₃O₄ morphology was found to be the best suitable for reversible lithium storage properties. It displayed superior cycling performances than nanoparticles and rod-like nanoclusters. More interestingly, excellent high rate capabilities (811 mAh g^?1 at 1780 mA g^?1 and 746 mAh g^?1 at 4450 mA g^?1) were observed for macroporous Co₃O₄ platelet. The good electrochemical performance could be attributed to the unique macroporous platelet structure of Co₃O₄ materials.     

Coordination of Actinide Single Ions to Deformed Graphdiyne: Strategy on Essential Separation Processes in Nuclear Fuel Cycle

The coordination of actinides and lanthanides, as well as strontium and cesium with graphdiyne (GDY) was studied experimentally and theoretically. On the basis of experimental results and/or theoretical calculations, it was suggested that Th⁴⁺, Pu⁴⁺, Am³⁺, Cm³⁺, and Cs⁺ exist in single‐ion states on the special triangular structure of GDY with various coordination patterns, wherein GDY itself is deformed in different ways. Both experiment and theoretical calculations strongly indicate that UO₂²⁺, La³⁺, Eu³⁺, Tm³⁺ and Sr²⁺ are not adsorbed by GDY at all. The distinguished adsorption behaviors of GDY afford an important strategy for highly selective separation of actinides and lanthanides, Th⁴⁺ and UO₂²⁺, and Cs⁺ and Sr²⁺, in the nuclear fuel cycle. Also, the present work sheds light on an approach to explore the unique functions and physicochemical properties of actinides in single‐ion states.     

Characteristic Fragmentation of Polysiloxane Monolayer Films by Bombardment with Monatomic and Polyatomic Primary Ions in TOF-SIMS

This study reports the characteristic fragmentation patterns from two polysiloxane polymers that form ordered overlayer on silver substrates. Results are compared for the bombardment of various monatomic and polyatomic projectiles of Cs⁺, C₆₀⁺ (10 keV), Bi₁⁺, and Bi₃⁺ (25 keV) in the high mass range time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra. Results are reported from sub-monolayer (solution cast) coverages of poly(dimethylsiloxane)s with the number average molecular weights (M_n) of 2200 and 6140 Da, respectively, and Langmuir-Blodgett monolayers of poly(methylphenylsiloxane) with molecular weights (MW) from 600 and 1000 Da. For each film, Bi projectiles resulted in the emission of positive silver cluster ions from the substrate under the polymer overlayer and peaks corresponding to silver cluster ions with larger mass were observed by impact of polyatomic 25 keV Bi₃⁺ projectiles. In addition, depending on the change of energy of Bi₃⁺, a different pattern of fragments was observed. With Cs⁺ and C₆₀⁺ impact, however, the emission of silver cluster ions was not detected. In the case of C₆₀⁺ impact for PDMS-6140, peaks corresponding to silver-cationized intact oligomers were not observed. In this paper, these results are explained by the possible bombardment mechanism for each projectile, based on its mass, energy, and split trajectories of the component atoms under the polyatomic impact.     

Metal binding selectivity of oxa-aza macrocyclic ligand: a DFT study of first- and second-row transition metal for four coordination systems

A detailed theoretical study of the 1,7,1l,17-tetraoxa-2,6,12,16-tetraaza-cycloeicosane ligand ([20]AneN₄O₄) coordinated to Fe²⁺, Co²⁺, Ni²⁺, Ru²⁺, Rh²⁺, and Pd²⁺ transition metal ions was carried out with the B3LYP method. Two different cases were performed: when nitrogen is the donor atom (1a _q ) and also with the oxygen as the donor atom (1b _q ). For all the cases performed in this study 1a _q structures were always more stable than the 1b _q ones. Considering each row is possible to see that the energy increases with the increase of the atomic number. The M²⁺ cation binding energies for the 1a _q complexes increase with the following order: Fe²⁺ < Ru²⁺ < Co²⁺ < Ni²⁺ < Rh²⁺ < Pd²⁺.

     

Application of a carbonized apricot stone for the treatment of some radioactive nuclei

Apricot stone shells were carbonized under certain chemical and thermal conditions to produce sorbents having a quantitative affinity to retain some radioactive nuclei. The sorbent shows a thermal stability upto 500 °C. The diffraction patterns clarify that the sorbent is mainly amorphous in structure. Carbon in these shells was elementally analyzed and the data reveal a predominant content of acidic surface centers with hydrophilic properties. The isoelectric point (pH_PZC) was determined and found to be 4.2 implying the acidic nature of the sorbent surface. The sorption of Cs⁺, Co²⁺ and Eu³⁺ on the prepared sorbent was studied from aqueous solution under different variables and the sorption capacity had values from 0.23-1.15 meq/g.     

Sorption behavior of Am<Superscript>3+</Superscript> on suspended pyrite

Sorption behavior of ²⁴¹Am (~10⁻⁹ M) on naturally occurring mineral pyrite (particle size: ≤70 μm) has been studied under varying conditions of pH (2–11), and ionic strength (0.01–1.0 M (NaClO₄)). The effects of humic acid (2 mg/L), other complexing anions (1 × 10⁻⁴ M CO₃ ²⁻, SO₄ ²⁻, C₂O₄ ²⁻ and PO₄ ³⁻), di- and trivalent metal ions (1 × 10⁻³ M Mg²⁺, Ca²⁺ and Nd³⁺) on sorption behavior of Am³⁺ at a fixed ionic strength (I = 0.10 M (NaClO₄)) have been studied. The sorption of ²⁴¹Am on pyrite increased with pH from 2.8 (84%) to 8.1 (97%). The sorption of ²⁴¹Am decreased with ionic strength at low pH values (2 ≤ pH ≤ 4), but was insensitive in the pH range of 4–10, suggesting the formation of outer-sphere complexes on pyrite surface at lower pH, and inner-sphere complexes at higher pH values. The sorption of ²⁴¹Am increased in the presence of (i) humic acid (5 < pH < 7.5), and (ii) C₂O₄ ²⁻ (2 < pH < 3). By contrast, other complexing anions such as (carbonate, phosphate, and sulphate) showed negligible influence on ²⁴¹Am sorption. The presence of Mg²⁺, Ca²⁺ ions showed marginal effect on the sorption profile of ²⁴¹Am; while the presence of Nd³⁺ ion suppressed its sorption significantly under the conditions of present study. The sorption of ²⁴¹Am on pyrite decreased with increased temperature indicating an exothermic process.