Adsorptivity of polyvinylpolypyrrolidone for selective separation of U(VI) from nitric acid media

Adsorptivity of polyvinylpolypyrrolidone (PVPP), a candidate resin with selectivity to U(VI) in HNO₃ media, to various metal ions was examined. It was found that PVPP has a strong adsorptivity to U(VI) in wide concentration range of HNO₃. The Scatchard plot analysis revealed that the adsorption of U(VI) by PVPP occurs at plural binding sites. The infrared spectroscopic analysis suggested that the strong binding site is due to the coordination of the carbonyl oxygen atom and the nitrogen atom in the pyrrolidone ring to UO₂ ²⁺. It was also found that fission product ions except Re(VII) as the simulant of Tc(VII) and Pd(II) are not adsorbed onto PVPP. The adsorptivities to Tc(VII) and Pd(II) species are weak, indicating that U(VI) can be separated from other metal ions by PVPP.     

Utilization of gamma-ray irradiation for hydrogen production from water

A technique has been proposed to promote hydrogen production from water by increasing the energy deposition in water through the conversion of γ-ray to low-energy electrons, which is achieved by putting solid materials into water. Simulation studies by the MCNP code indicate that the average deposited energy in water can be increased by optimizing geometry of the materials. In the present experiments using Al₂O₃ particles of various average diameters, the maximum amount of hydrogen produced is 3.48 μmol/cm³ for the water containing Al₂O₃ particles of 3 μm diameter, which is more than two order of magnitude larger of the H₂ produced in water-only configuration.     

Nanometer-sized gelatin particles prepared by means of gamma-ray irradiation

Nanometer-sized gelatin particles have been prepared by means of gamma-ray irradiation and characterized by static and dynamic light scattering combined with circular dichroism (CD) measurements. The molecular weight of the nanoparticles was much larger than that of the original gelatin molecules, whereas the hydrodynamic radius was much smaller. Radius of gyration evaluated from the angular dependence of the static light scattering intensity decreased with increasing irradiation dose. CD spectra of the gelatin nanoparticles were independent of temperature, and it is suggested that the nanoparticles consist of highly and randomly packed gelatin and their conformation is stable against the temperature change.     

Influences of Co-60 gamma-ray irradiation on electrical characteristics of Al2O3 MOS capacitors

Effects of gamma-ray irradiation on the electrical characteristics of Al₂O₃ MOS capacitors such as barrier height, acceptor concentration, series resistance and interface state parameters have been studied by analyzing capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The fabricated MOS capacitors were irradiated with gamma-rays at doses up to five grays. C–V and G/ω–V measurements were recorded prior to and after irradiation at high frequency. The results show that the measured capacitance and conductance values decreased with increasing in irradiation dose and C–V and G/ω curves has been shifted toward the negative voltages. Moreover, the series resistance (R _s) and density of interface states increased with increasing in irradiation dose and density of interface states (D _it) were calculated as order of 10¹² eV^?1cm^?2 prior to and after irradiation. Due to presence and variations in the R _s values, the corrected and the measured C–V and G/ω–V exhibited different behaviors. Therefore other electrical characteristics were assessed from corrected C _c characteristics. It was observed that acceptor concentration decreased with increasing in barrier height of device due to changes in interface states and diffusion potential.     

Functionalization of gold and carbon nanostructured materials using gamma-ray irradiation

Gold nanoparticles were successfully attached to the surface sites of carbon nanotubes (CNT). Both nanostructured materials were functionalized by λ-ray irradiation without chemical treatments for creating active sites. UV–visible absorption spectra of the un-irradiated and gamma ray-irradiated nanomaterials are also studied. The absorption spectrum of the irradiated CNT shows a new strong peak located at 700 nm, which might act as the active site on the surface of CNT, the result being an attachment of gold nanoparticles. This approach provides an efficient method to attach other nanostructures to carbon nanotubes for using them in different applications such as medicine and synthesis of catalytic materials.     

Generation of HNO2 by bubbling NO in HNO3 system and its application in the PUREX process

This work is aimed at studying HNO₂ generation by bubbling NO in HNO₃ solution. The formation and decomposition of HNO₂ depend on the 2NO+HNO₃+H₂O3HNO₂ reaction. During the HNO₂ generation, the HNO₃ concentration was kept constant. The influence of HNO₃ concentration, temperature, NaNO₃ concentration and NO bubbling rate was studied. Its possible application in the PUREX process was evaluated.     

Method for the degradation of dibutyl phthalate in water by gamma-ray irradiation

The degradation and mineralization of dibutyl phthalate (DBP), one of endocrine disruptors, by g-ray irradiation were demonstrated. The degradation was enhanced by the effective energy conversion of g-rays to low-energy electrons and photons with the assistance of the interactions between g-rays and metals, which is especially in the case of high Z materials effective. Numerical simulations using EGS code supported the experimental results. Improvements of the energy conversion process are also suggested by controlling the shape of the metal and its spatial configuration in the DBP solution.     

Stability of dispersions in polar media

The stability of dispersions in polar organic media was reviewed comparing with that of in aqueous and non-polar media. Structure and properties of the double layer of AgI in water-ethylene glycol were studied and the stability of the dispersions was related to the study of the double layer.Coagulation concentrations of Ag,AgI and α-FeOOH dispersions in methanol, ethanol 1,2-propanol and acetone by the addition of electrolytes were determined.Coagulation by monovalent counterions is due to double layer compression. With bi- and multivalent counterions or in low dielectric constant-solvents coagulation is primarily caused by charge neutralization.The effect of an ionic surfactant, AOT on the stability of TiO₂ or α-Fe₂O₃ in water-p-dioxane mixtures was studied. AOT behaved as a coagulating agent in polar media ( ϵ = 10–50) , though it worked as a dispersing agent in non-polar (dioxane) and water rich media. AOT accordingly coagulated the dispersion a carbon black in 2-butanone, though a nonionic surfactant did not so. Desolvation from the particle surface is considered to be an important origin of coagulation by AOT in polar media, because AOT is not adsorbed on particles and comsiderably dissociates into ions in 2-butanone.     

Effect of gamma-ray irradiation on the mechanical strength of polystyrene-ferrocene composite

Thin films of polystyrene-ferrocene (PS---Fe) composite were irradiated with various doses of gamma irradiation ranging from 4·1 to 25·3 Mrad. The Vickers hardness number (H_v) was calculated for pure and irradiated specimens. It was used to analyse mechanical strength at a saturation load of 100 g. The mechanical strength was found to increase with irradiation dose up to 12 Mrad. Brittleness of the composite PS-Fe was found to occur at a higher dose of 25 Mrad as compared to 15 Mrad for polystyrene. Further, fracture toughness, brittleness index and yield strength were calculated for various irradiated specimens consequent to crack propagation in the specimens.     

Measurement of the ash content of iron-rich coals by gamma-ray irradiation

Ash contents of some coal samples from Enugu mines in Nigeria were measured using gamma-ray irradiation technique. The method employed gamma-ray energies of 0.060, 0.662 and 1.33 MeV of²⁴¹Am,¹³⁷Cs and⁶⁰Co, respectively, and a counting system with a scintillation detector, to obtain empirical relationships between the conventionally determined ash content and the measured gamma-attenuation coefficient in the sample. The sensitivity of the method was observed to decrease drastically with increase in ash content above 35% ash, and with increase in energy of the gamma-ray. Further analyses showed that the error in the ash content determination was due to iron content which was not constant, but increased with ash content, with vidth variation above a mean value of ±0.64% Fe₂O₃.     

Degradation behavior of poly (l-lactide-co-glycolide) films through gamma-ray irradiation

Gamma-ray irradiation is a very useful tool to improve the physicochemical properties of various biodegradable polymers without the use of a heating and crosslinking agent. The purpose of this study was to investigate the degradation behavior of poly (l-lactide-co-glycolide) (PLGA) depending on the applied gamma-ray irradiation doses. PLGA films prepared through a solvent casting method were irradiated with gamma radiation at various irradiation doses. The irradiation was performed using 60Co gamma-ray doses of 25–500 kGy at a dose rate of 10 kGy/h.The degradation of irradiated films was observed through the main chain scission. Exposure to gamma radiation dropped the average molecular weight (M_n and M_w), and weakened the mechanical strength. Thermograms of irradiated film show various changes of thermal properties in accordance with gamma-ray irradiation doses. Gamma-ray irradiation changes the morphology of the surface, and improves the wettability. In conclusion, gamma-ray irradiation will be a useful tool to control the rate of hydrolytic degradation of these PLGA films.     

Effect of irradiation on AMP based resins for cesium separation from HNO3 feed solutions: batch and column studies

Three different resins containing ammonium molybdophosphate (AMP), viz. PMMA (polymethylmethacrylate) resin, composite AMP resin and ALIX (a bisphenol based resin), were evaluated for their irradiation stability. The studies included batch as well as column studies and were carried out for cesium uptake behaviour at 3 M acidity. The resin beads were irradiated to varying dose viz., 0 MRad, 10 MRad, 20 MRad, 50 MRad and 100 MRad. The time taken to attain equilibrium was rather long and about 2–5 h were found to be required for attaining equilibrium in batch studies. Batch Cs(I) uptake studies revealed no significant effect on the K _d values in case of the PMMA resin while in case of the composite resin and ALIX resin, a decrease in the K _d was observed as a function of irradiation dose. The resin capacity indicated contrasting behaviour with irradiation dose for the resins. Column runs have been carried out for the uptake of radio cesium using both unirradiated and irradiated resins using feed solutions containing 3 MHNO₃. The loading capacities of the resins were found to be proportional to their Cs loading capacities observed in batch studies. Study revealed that the composite AMP had the maximum and PMMA has the least loading capacity. Results of these studies show that these AMP based resins can be used for cesium separation from acidic nuclear waste.     

Extraction chromatography in the DHDECMP—HNO3 system

The extraction behaviour of Ce(III) and Am(III) in extraction chromatography has been investigated on the basis of partition and infrared studies. The stationary phase was purified undiluted DHDECMP supported on Amberlite XAD-4 and the mobile phase was nitric acid. The results have shown that the equilibria for the extraction of Ce(III) and Am(III) by the DHDECMP/XAD-4 resin agreed very closely with those in solvent extraction.     

含铁氢氟酸和硝酸混合酸中氢氟酸和硝酸含量的测定

在氢氟酸和硝酸的混酸中由于Fe3+的存在干扰了测定,本文讨论了对上述酸的测定方法,本法采用氟电极测定混合酸中氢氟酸的含量,其中Fe3+的干扰可加入柠檬酸三钠除去[1].用氢氧化钠作滴定剂,用玻璃电极作指示电极,用二次微商法确定滴定的体积,通过计算得出总酸的含量[2],从总酸中减去氢氟酸的含量即为硝酸的含量.     

Optical detection of NO3 and NO2 in “pure” HNO3 vapor,the liquid-phase decomposition of HNO3

Flowing and static gas-phase samples of HNO₃ in O₂ and N₂ were analyzed by long-path ultraviolet/visible (UV/VIS) spectroscopy to reveal the presence of both NO₂ and NO₃, the concentrations of which were calculated using differential absorption cross sections. NO₂ is produced predominantly by the heterogeneous decomposition of HNO₃, whereas NO₃ is generated in the gas phase by the thermal decomposition of N₂O₅, a product of the self-disproportionation of liquid HNO₃. © 1993 John Wiley & Sons, Inc.     

The determination of boron in biological materials by neutron irradiation and prompt gamma-ray spectrometry

A prompt-gamma neutron activation technique has been developed using the (n, ) apparatus situated at the O degree through-tube of the Imperial College CONSORT II Reactor with a thermal neutron flux at the target position of approximately 2×10⁶ n cm^–2 sec^–1, and a Compton-suppression system involving a lithium-drifted germanium (Ge(Li)) detector and a sodium iodide anti-Compton shield. Boron levels of 1–5 g g^–1 (detection limit 0.05 g B for 10,000 sec period of measurement) can be attained using the Compton-suppression system with graphical inter-polation correction for the 472 keV sodium-ray peak contribution to the Doppler-broadened 478 keV boron gamma-ray peak resulting from the¹⁰B(n, )⁷Li reaction. Very good agreement is reached for boron levels compared using this system for various Standard Reference Materials and other published values. Measurement of the boron content of bone and tooth samples from rheumatoid arthritis individuals shows lower levels, (p<0.05); 16.13±7.53 g g^–1, when compared with a control population; 19.79±4.18 g g^–1. A positive correlation existed between the boron content of bone and tooth material for each study group. Results indicate that boron availability may be associated with rheumatoid arthritis.     

Kinetics study of the reaction HO + HNO3

The reaction has been studied using a discharge-flow tube with resonant fluorescence detection of HO. Measurements of k₁ have been made at temperatures between 237 and 404 K. Our results and earlier work suggest that the rate constant has a minimum at T ? 500 K. Below room temperature our results are given by the expression k = (2.0 ± 0.4) × 10^?14 exp[(430 ± 60)/T] cm³ molecule^?1 s^?1, where the error limits include an estimate of the measurement accuracy. No dependence of k₁ on pressure at 300 K is observed in studies between 1- and 10-torr helium. An upper limit of k_b < 1% k₁ at 300 K is given.     

Amino-acid synthesis in aqueous media under ultrasonic irradiation

The now-famous “Miller-Urey experiment” used a reduced mixture of gases to form basic organic molecules, such as amino acids. Since then, several methods have tried to reproduce the synthesis of amino acids under unusual conditions. All authors agree that the formation mechanisms of amino acids under such conditions might be of radical origin. If so, sonochemistry, known to enhance or to promote radical pathways, should be a powerful tool to access the synthesis of these compounds. We explored the feasibility of amino acid synthesis under ultrasonic irradiation in aqueous medium under a reductive atmosphere. The effects of several experimental parameters such as incident ultrasound frequency, temperature, nature and concentration of initial reactants, reaction time, and acoustic energy were explored.