Band 110, Heft 2

In 2014 the first synthesis of a transactinide carbonyl complex – seaborgium hexacarbonyl – was reported. This was achieved in gas-phase chemical experiments in a beam-free environment behind the recoil separator GARIS. Extending this work to heavier elements requires more efficient techniques to synthesize carbonyl complexes as production rates of transactinide elements drop with increasing atomic number. A novel approach was thus conceived, which retains the benefit of a beam-free environment but avoids the physical preseparation step. The latter reduces the yields for products of asymmetric reactions such as those used for the synthesis of suitable isotopes of Sg, Bh, Hs and Mt. For this a series of experiments with accelerator-produced radioisotopes of the lighter homologues W, Re and Os was carried out at the tandem accelerator of JAEA Tokai, Japan. A newly developed double-chamber system, which allows for a decoupled recoil ion thermalization and chemical complex formation, was used, which avoids the low-efficiency physical preseparation step. Here, we demonstrate the feasibility of this newly developed method using accelerator-produced short-lived radioisotopes of the 5d homologues of the early transactinides.

A new method is developed to calculate the dilution ratio N of the two reactant solutions during nucleation rate determination. When the initial apparent supersaturation ratio S N  =  f(N) in the dilution tank is controlled between 1.66 and 1.67, the counted nuclei is the most, both nuclei dissolving and secondary nucleation avoided satisfactorily. Based on this methoed, Plutonium(IV) oxalate is precipitated by mixing equal volumes of tetravalent plutonium nitrate and oxalic acid solutions. Experiments are carried out by varying the supersaturation ratio from 8.37 to 22.47 and temperature from 25 to 50 °C. The experimental results show that the nucleation rate of plutonium(IV) oxalate in the supersaturation range cited above can be expressed by the equation R N  = A N exp(− E a /RT )exp[− B /(ln S ) 2 ], where A N  = 4.8 × 10 23  m −3  s −1 , and E a  = 36.2 kJ mol −1 , and B  = 20.2. The crystal growth rate of plutonium(IV) oxalate is determined by adding seed crystals into a batch crystallizer. The crystal growth rate can be expressed by equation G ( t ) =  k g exp( −E’ a /RT ) ( c  −  c eq ) g , where k g  = 7.3 × 10 −7 (mol/L) −1.1 (m/s), E ’ a  = 25.7 kJ mol −1 , and g =  1.1.

In this investigation, a synthetic Talc Phosphogypsum ferri-silicate TPFS sorbent was prepared by thermal activation then evaluated the uranium ions removal from sulfate waste solution containing uranium. Generally, the synthetic adsorbents from raw and waste materials have a significant attention from scientists because the environmental concern and economic development, particularly, the uranium elimination from radioactive waste solutions. The uranium removal percentage and loading capacity were determined by optimization the conditions of adsorption such as the pH range, adsorbent/adsorbate ratio, uranium concentration of radioactive waste solutions, equilibrium time and temperature. The resultant adsorption efficiency and loading capacity were 87.2% and 375 mg g −1 , respectively. The adsorption isothermally was in accordance with Langmuir isotherm model, in addition pseudo-second-order kinetic model, with theoretical capacity of 384.6 and 333 mg g −1 , respectively. Uranium (VI) adsorption on TPFS was inhibited at elevated temperatures. The removal of uranium from sulfate waste solution by TPES sorbent according to the thermodynamic functions values was exothermic (∆ H of −16.095) and non-spontaneous in nature (∆ G of −17.27 at 303 K). In addition, there was a decrease in the randomness at the TPFS/uranium waste solution interface with ∆ S value of 3.88.

Tamusu area is the primary pre-selection site of clayrock disposal repository for high-level radioactive waste (HLW) in China. However, the research on the migration behavior of nuclides in Tamusu clayrock is still in its infancy. For the first time in laboratory, the diffusion behavior of Re(VII) in Tamusu clayrock core was studied by means of through-diffusion method. The effects of pH, ionic strength and humic acid on the diffusion behavior of Re(VII) in clayrock were studied. The effective diffusion coefficient, apparent diffusion coefficient and rock capacity factor value were obtained. All the experimental conditions of Re(VII) diffusion in Tamusu clayrock are compared with other geological samples under the same conditions in literature data. The diffusion mechanism of radionuclide in Tamusu clay is discussed, which can provide experimental data for site selection and safety assessment of high-level radioactive waste repository in China. The experimental results showed an effective application and reference for the countries disposed HLW in mudrocks or clayrocks, such as France, Belgium etc. in Europe. Moreover, this research can provide the original data support for the metallogenic regularity and prospecting prognosis of rare element rhenium in different geological environments.

The incorporation of marble particles into the framework of composite material through the polymerization of acrylic acid (AA) and acrylamide acid (AM) using induced gamma irradiation was performed. The novel poly[AA-AM]-marble composite was characterized by multiple analytical instruments such as: energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) analysis, differential thermal analysis-thermogravimetric analysis (DTA-TGA), Fourier transformer infrared (FTIR), surface area measurements using Brunauer–Emmett–Teller (BET) method and scanning electron microscope (SEM). Radioisotopes of fission ( 152+154 Eu) and activation products ( 60 Co) are the major environmental threats. Sorption of stable isotopes of cobalt and europium onto the synthesized composite material as the sorbent is applied. Sorption kinetics of Eu 3+ and Co 2+ were computed. The obtained results were analyzed by pseudo-first- and second-order, intraparticle diffusion, and Elovich kinetic models. It is deduced that the pseudo-second-order was more fitted and a chemisorption mechanism was suggested. The sorption capacity for Eu 3+ and Co 2+ on the prepared composite material was measured at the contact time (2 h) and pH = 4 (for Eu 3+ ), pH = 6 (for Co 2+ ) and it was found to be 91.2 and 13.1 mg/g, respectively. A promising result for the decontamination of both Eu and Co ions was obtained in various aquatic ecosystem applications such as: river water, tap water and groundwater.

Nanocomposites have received voluminous interest due to the combination of unique properties of organic and inorganic component in one material. In this class, magnetic polymer nanocomposites are of particular interest because of the combination of excellent magnetic properties, stability, and good biocompatibility. This paper reports the preparation and characterization of nanocomposites films based on natural rubber in latex state (NRL) loaded with different concentrations of semiconducting magnetite nanoparticles (Fe 3 O 4 ) (MNPs) (5, 10, 15, 20, and 30%). NRL (100%) and NRL/Fe 3 O 4 nanocomposites were prepared by solution casting technique then, exposed to various irradiation doses (50, 70, 100 kGy).The nanocomposite’s morphological, and physical properties were investigated through various spectroscopic techniques such as Fourier-transformed infrared, X-ray diffraction, scanning electron, and transmission electron microscopies. The mechanical properties, including the tensile strength and elongation at break percentage ( E b %) of the nanocomposites were also studied and compared with the 100% NRL films. Based on the results obtained from the mechanical study, it is found that the NRL/20% Fe 3 O 4 nanocomposite film exhibited the highest tensile strength at 100 kGy. On the other hand, based on the conductivity study, it is found that, NRL/Fe 3 O 4 nanocomposite with 10% magnetite exhibit the highest conductivity as the content of magnetite plays an important and effective role based on the high and homogeneous dispersity.

This study, uses two polyfunctional monomers (PFMs) namely ethylene glycol dimethacrylate (EGDMA) as a bifunctional monomer and trimethylolpropane triacrylate (TMPTA) as a trifunctional monomer were used as co-agents in irradiation crosslinking of Ethylene Propylene Diene Monomer Rubber (EPDM). The effect of concentration of each PFM and irradiation dose on the crosslinking density, gel content, swelling behavior in motor and brake oils, in addition to the mechanical and thermal stability properties of EPDM was investigated in detailed. The results showed a remarkable increase in the gel content, crosslinking density and mechanical properties as the concentration of PFMs increased from 1 to 5 phr (parts per hundred parts of rubber). The various blends of EPDM with the trifunctional monomer express the highest gel content and crosslinking density than those with the bifunctional monomer. The addition of 5 phr of TMPTA to EPDM causes a dramatic improvement in tensile strength (TS) of the prepared blend reached to 188% compared to neat EPDM at 50 kGy. At the same time, the maximum TS of the blend containing 5 phr of EGDMA achieved only 41% compared to neat EPDM at an irradiation dose of 100 kGy. The swelling of irradiated samples in brake oil revealed a stronger oil resistance than motor oil. For all irradiated samples, the oil uptake decreased with the irradiation dose up to 100 kGy. The EPDM samples containing 5 phr of TMPTA recorded the highest oil resistance at 100 kGy. The results also showed that the addition of PFMs and irradiation treatment of the various prepared blends improved the thermal stability of EPDM. Finally, neat EPDM and the blends containing 1 and 3 phr of EGDMA can be used as radiation dosimeters in the very high dose range (50–200 kGy).