Radiolysis of Tributyl Phosphate by Particles of High Linear Energy Transfer

Tributyl Phosphate (TBP), used in chemical separation processes for used nuclear fuel, is susceptible to radiolysis causing losses in process performance. We have studied its degradation by exposing dry 1M TBP/n-dodecane solutions to gamma radiation from a cesium-137 source and in a mix of low and high linear energy transfer (LET) radiation by irradiating samples in the UC Irvine TRIGA^® reactor and utilizing the ¹⁰B(n,α)⁷Li reaction. In a 1 M solution of TBP in n-dodecane the degradation of TBP (G^?_TBP) was found to be 0.36 and 0.14 μmol/J for low and high LET radiation, respectively. The formation of dibutyl phosphoric acid, DBP, (G⁺_DBP) in this solution was found to be 0.18 and 0.047 μmol/J for low and high LET radiation, respectively. In samples exposed to low LET as well as a mix of low and high LET a variety of TBP degradation products containing phosphorus were observed indicating that other degradation products than DBP and the monobutyl diacid (MBP) were formed. Our results for both low and high LET radiation compare well with previous studies on these systems indicating that high LET degrades TBP to a lesser extent than gamma radiation. Available data for high LET is not as abundant as for low LET making such comparisons challenging. Nevertheless, our method yields a value for G⁺_DBP that agrees well with previous alpha radiolysis studies indicating that our method shows promise for studying high LET radiolysis in liquid-liquid extraction systems.     

Hydrogen Production in the Radiolysis of Dodecane and Hexane

The yields of molecular hydrogen, H₂, have been measured in the radiolysis of dodecane and hexane following radiolysis by γ-rays and a variety of heavy ions. Measured yields with γ-rays are found to be slightly higher than literature values and decrease by about 25% on aeration of the sample. Increasing the linear energy transfer (LET) from γ-rays to radiolysis with protons results in a decrease of H₂ yields by about 15% due to the increased importance of second-order H atom combination reactions. A further increase in LET results in a slight increase in H₂ yields.     

Radiation chemistry of the branched-chain monoamide di-2-ethylhexyl-isobutyramide

The radiolytic degradation of di-2-ethylhexyl-isobutyramide (DEHiBA) was examined by subjecting the compound to gamma irradiation, measuring the remaining concentration of the intact compound, identifying the degradation products, and measuring uranium distribution ratios. The combined effects of radiation dose, contact with aqueous solutions of HNO₃, and aeration were also examined. The DEHiBA displayed significant stability at doses up to 1000 kGy, undergoing a slow exponential concentration decrease that was accompanied by the appearance of multiple degradation products. The most abundant compounds that were formed by radiolysis resulted from cleavage of the C_carbonyl–N and C_ethylhexyl–N bonds, generating di-ethylhexylamine and mono-ethylhexyl-isobutyramide. Acid contact did alter the radiolytic pathways, with acid favoring cleavage of the C_carbonyl-N bond, while a more diverse array of compounds was formed in the absence of acid. Pulsed radiolysis experiments were also conducted, in which picosecond bursts of energetic electrons were used to irradiate solutions of dodecane containing DEHiBA; formation of the dodecane radical cation was implicated, which serially reacted with DEHiBA to form a radical or radical cation species intermediate in the formation of the observed products. The slow degradation kinetics suggests that DEHiBA possesses good potential for selective extraction of uranium in fuel cycle extraction operations.     

Radiolytic and hydrolytic degradation of the hydrophilic diglycolamides

The stability of different hydrophilic diglycolamides against acid degradation and radiolysis was studied. Tetraethyldiglycolamide (TEDGA) was found to undergo degradation in nitric acid at high reaction rates at elevated temperatures with a maximum of a ~8% decrease per hour at 65°C in 4 mol L^–1 HNO₃. The radiolysis was studied for tetramethyldiglycolamide (TMDGA), TEDGA, methyl-tetraethyldiglycolamide (Me-TEDGA), and dimethyl-tetraethyldiglycolamide (Me₂-TEDGA). The degradation rates decreased with increasing molecular weight, following the trend TMDGA > TEDGA > Me-TEDGA ≥ Me₂-TEDGA. Degradation products were identified by mass spectrometric techniques and were found to be comparable to those previously reported for the radiolysis of lipophilic diglycolamides in dodecane. Significant insight into the degradation mechanism in water was gained using pulse radiolysis experiments. The ^?OH radical was identified as the most important reactive species and predominant mechanism of radical reaction is one of electron transfer rather than H-atom abstraction.     

A CHEMICAL MODEL OF THE SOLVENT EXTRACTION SYSTEM: NITRIC ACID- URANYL NITRATE- WATER - TRI-n-BUTYL PHOSPHATE (TBP) - DILUENT

ABSTRACT

A mathematical model founded on the equilibrium constants expressions has been developed for the simultaneous extraction of nitric acid and uranyl nitrate with TBP in alkane diluents. The model uses chemical activities of nitric acid and uranyl nitrate in the aqueous phase and the stoichiometric concentrations of their TBP solvates in the organic phase. The apparent formation constants of the species (TBP)₂, (TBP)₂HNo₃, TBPHNO₃, and UO₂(NO)₃ 2TBP, present in the organic phase, have been established. The model fits well the distribution results over the whole concentration range of the extraction isotherms, and extractant concentrations 5–10% TBP. The starting data are the chemical activities of nitric acid and uranyl nitrate in the aqueous phase and their stoichiometric concentrations in the organic phase.     

Application of Vapor Pressure Osmometry to the Study of Uranyl Nitrate and Thorium Nitrate Complexes with Tributyl Phosphate

Molecular weights of uranyl nitrate and thorium nitrate solutions in TBP were determined using vapor pressure osmometry. The results seem to show that in carbon tetrachloride uranyl nitrate forms a di-solvate only, whereas in acetone solution this complex is partly dissociated. Thorium nitrate results have been explained assuming a mixture of two complexes with TBP-a di-solvate and a tri-solvate. The equilibrium constant for the reaction Th(NO₃)₄ · 2TBP + TBP ? Th(NO₃)₄ · 3TBP was found to be K_x = 30 at 25°C.     

A Study of the γ-Radiolysis of N,N-Didodecyl-N′,N′-Dioctyldiglycolamide Using UHPLC-ESI-MS Analysis

Solutions of N,N-didodecyl-N′,N′-dioctyldiglycolamide in n-dodecane were subjected to γ-irradiation in the presence and absence of both an aqueous nitric acid phase and air sparging. The solutions were analyzed using ultra-high-performance liquid chromatography-electrospray ionization-mass spectrometry (UHPLC-ESI-MS) to determine the rates of radiolytic decay of the extractant as well as to identify radiolysis products. The DGA concentration decreased exponentially with increasing dose, and the measured degradation rate constants were uninfluenced by the presence or absence of acidic aqueous phase, or by air sparging. The identified radiolysis products suggest that the bonds most vulnerable to radiolytic attack are those in the diglycolamide center of these molecules and not in the side chains.     

Role of activated carbon on micropollutans degradation by ionizing radiation

The objective of this study was to analyze the influence of the presence of activated carbon on the degradation of the triiodinated contrast medium diatrizoate (DTZ) by the simultaneous use of gamma radiation and activated carbon. Four commercial activated carbons (Ceca, Witco, Sorbo, and Merck) with different textural and chemical characteristics were used for this purpose. The percentage DTZ removal obtained was considerably higher with the gamma radiation/activated carbon (GM/AC) system than with radiolysis in the absence of activated carbon, and it depended on the specific activated carbon employed. First, we optimized the amount of activated carbon required to maximize the amount of DTZ removed by the GM/AC system (0.06 g). The degradation constants were higher with the GM/AC system than with radiolysis alone, evidencing a synergic effect that favors pollutant removal. This synergic effect is independent of the textural but not the chemical characteristics of the activated carbon, observing a higher synergic activity for carbons with a higher surface content of oxygen, specifically quinone groups. We also highlight that the synergic effect of the activated carbon requires adsorbent–adsorbate electrostatic interaction and is absent when this interaction is hindered.     

KINETICS OF THE COMPLEXATION OF UO2(NO3)2 WITH TRIBUTYL PHOSPHATE (TBP) IN XYLENE#

ABSTRACT

The kinetics of ligand exchange between bulk solution TBP and uranyl nitrate bound TBP in o-xylene has been investigated by ³¹P dynamic NMR spectroscopy. First order ligand exchange rate constant, k, and the activation energy for the uranyl nitrate-TBP system were determined from plots of transverse relaxation rates (In (l/τ)) versus reciprocal temperature (1/T). Using the Eyring equation, the average values of activation enthalpy, δH^* (30.8±5.1 kJ-mole^?1), and activation entropy, δS^* (-109±19 J/mol-K) have been calculated. The negative entropy of activation value indicates an increase in order on proceeding from the reactants to the activated complex. Therefore, an associative mechanism may be proposed for the ligand exchange reaction between UO₂(NO₃)₂ TBP2 and TBP. Equilibration of the extractant phase with 1.0 M HC1 did not change the ligand exchange rate constants or the activation parameters appreciably. These results are discussed in comparison with previous reports on TBP exchange rates for this system.     

Physiochemical Properties of Gamma-Irradiated Tri-iso-amyl Phosphate–Dodecane System: Effect of Aqueous Phase Acidity

ABSTRACT

Tri-iso-amyl phosphate (TiAP) in dodecane (DD) is emerging as a potent alternative for the extraction of suitable actinides from nitric acid solutions comprising various metal ions. A detailed investigation on the evolution in physicochemical properties upon gamma irradiation of TiAP-DD system has been carried out. Physical properties, such as density, viscosity, phase disengagement time, interfacial tension, etc., were measured for neat as well as irradiated solvent phases. Effect of aqueous phase acidity, which is an important parameter during extraction, on the hydrodynamic properties of the solvent during radiolysis was compared. ATR–FTIR spectroscopy of the irradiated phase was compared to find out the formation of new classes of compounds, if any.     

Studies on the use of N,N,N′,N′-Tetra(2-Ethylhexyl) Diglycolamide (TEHDGA) for Actinide Partitioning II: Investigation on Radiolytic Stability

Abstract

N,N,N′,N′-tetra(2-ethylhexyl)diglycolamide (TEHDGA) was found to be a promising extractant for actinide partitioning from high-level waste (HLW) (Part I). In order to evaluate the applicability of TEHDGA to the HLW partitioning process, investigations on its radiolytic stability were carried out. The present work deals with the studies on the uptake of americium by γ-irradiated 0.2 M TEHDGA/n-dodecane in the absence and presence of phase modifiers—di(n-hexyl)octanamide (DHOA), isodecanol and n-decanol—against the absorbed dose up to 1 × 10⁶ Gy in the presence of nitric acid at varying concentrations. The addition of phase modifiers suppressed the radiolysis of TEHDGA in n-dodecane and DHOA was found to be the most effective radiolysis suppressor. Investigations were also carried out on the degradation of neat TEHDGA by γ-irradiation, and it was attempted to isolate and identify its degradation products by instrumental analysis. The radiolysis study showed that the degradation products were formed by the cleavage of the –C-N bond, to eliminate an ethylhexyl group, and the bond adjacent to the ether bond. The results obtained for TEHDGA radiolysis were compared with that of its straight-chain isomer TODGA, and TEHDGA was observed to be more resistant to radiation than TODGA. The changes in the physico-chemical properties of γ-irradiated TEHDGA against the absorbed dose were also investigated.     

用微胶囊萃取铀

用微胶囊萃取铀倪沛红张明祖陈漫里严年喜（苏州大学化学化工学院，苏州２１５００６）关键词微胶囊萃取铀界面缩聚平均粒径１前言铀作为核燃料之一具有重要的应用价值。有关铀的提取方法已经研究得很多，主要是采用溶剂萃取的方法。八十年代以来，有关液膜法萃取铀的研究...     

铀酰配合物高效识别水溶液中Fe3+的性质研究

基于含氮的柔性三羧酸配体异氰脲酸三(2-羧乙基)酯(H3tci),合成了一个具有二维空间结构的铀酰配合物(UO2(tci)·2H2O),通过X射线单晶衍射的方法测定了其晶体结构.在水溶液中,研究了该铀酰配合物对过渡金属离子的荧光作用,结果显示,该配合物对Fe3+有较好的敏感性.进一步的探索实验表明,该配合物可以高选择性...     

Effect of Radiolysis in Altering the Physiochemical and Metal Retention Properties of Solvent-Diluent-Acid Systems

Systematic studies were performed on radiolytic degradation of Tri-n-Butyl Phosphate diluted with n-Dodecane or Normal Paraffin Hydrocarbon in the presence/absence of nitric acid as a function of absorbed gamma dose. Viscosity and phase disengagement time increased with absorbed dose but interfacial tension decreased gradually. The extent of damage caused during radiolysis was estimated by Zr retention in the organic phase. The effectiveness of carbonate wash in restoring the quality of the solvent was evaluated. Comparison of the IR spectra for the neat and the degraded samples revealed the formation of nitro alkanes at absorbed dose above 20 MRad.     

Studies of new oligomer–metal complexes and their antibacterial activities

A new oligomeric ligand was synthesized from anthranilic acid and 2‐aminopyridine with formaldehyde using a condensation technique in the presence of acid medium. Oligomer–metal complexes were prepared involving transition metal ions Cu(II), Mn(II) and Zn(II) using the synthesized oligomer as ligand. The oligomeric ligand and its metal complexes were characterized using various spectral techniques such as Fourier transform infrared, electronic, electron spin resonance, ¹H NMR and ¹³C NMR. Gel permeation chromatography was used to determine number‐, weight‐ and size‐average molecular weights of the oligomeric ligand. The surface characteristics and nature of the oligomeric ligand and its metal complexes were examined using scanning electron microscopy and X‐ray diffraction analysis. The thermal properties and degradation behaviour of the oligomeric ligand and its complexes were investigated using thermogravimetric analysis. Kinetic and thermodynamic studies of the ligand and its metal complexes were carried out using Freeman–Carroll (FC) and Sharp–Wentworth (SW) methods. From the thermogravimetric data, kinetic and thermodynamic parameters such as activation energy, order of reaction, entropy change, apparent entropy, frequency factor and free energy change were calculated. The activation energy was further calculated from the Phadnis‐Deshpande (PD) method and the degradation mechanism for the thermal decomposition reaction is proposed. The activation energy calculated from the FC and SW methods was in good agreement with that calculated from the PD method. The oligomeric ligand and its metal complexes were screened for antibacterial activity. It was found that the synthesized compounds were potent antibacterial agents. © 2012 Society of Chemical Industry     

电子束辐照降解氰化浸金废水的研究进展

电子束辐照处理废水技术具有能处理众多难降解、高毒性污染物,适应性广泛,不产生二次污染,安全可靠等优点。浸金废水是高毒性含氰废水,锌氰络合物是浸金废水中的主要成分之一。通过电子束辐照锌氰络合物水溶来模拟电子束辐照降解浸金废水研究,研究了不同初始浓度、不同辐照剂量下的辐照效应,分析了电子束辐照降解浸金废水的可行性及存在的问题,并展望其应用发展前景。     

Thermal behavior of poly(acrylic acid)–poly(vinyl pyrrolidone) and poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

Thermal analysis (TGA and DTA) of samples of PAA, PVP, PAA–PVP complexes, containing different weight fractions of PAA and ternary polymer–metal–polymer complexes, were studied. The activation energy parameters for the thermal degradation were also calculated. The study of the effect of FeCl₃, NiCl₂, and Ni(NO₃)₂ on the TGA and DTA curves of the complexes showed that the decompositions are dependent on the concentrations and the nature of the metal ions. The DTA traces of PAA–PVP complex containing FeCl₃, NiCl₂, and Ni(NO₃)₂ showed that the treatment of the complex with these metal ions causes considerable changes in the thermal decomposition of PAA–PVP complex. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4049–4057, 2006     

Radiolysis Studies of Oxidation and Nitration of Tyrosine and Some Other Biological Targets by Peroxynitrite-Derived Radicals

The widespread interest in free radicals in biology extends far beyond the effects of ionizing radiation, with recent attention largely focusing on reactions of free radicals derived from peroxynitrite (i.e., hydroxyl, nitrogen dioxide, and carbonate radicals). These radicals can easily be generated individually by reactions of radiolytically-produced radicals in aqueous solutions and their reactions can be monitored either in real time or by analysis of products. This review first describes the general principles of selective radical generation by radiolysis, the yields of individual species, the advantages and limitations of either pulsed or continuous radiolysis, and the quantitation of oxidizing power of radicals by electrode potentials. Some key reactions of peroxynitrite-derived radicals with potential biological targets are then discussed, including the characterization of reactions of tyrosine with a model alkoxyl radical, reactions of tyrosyl radicals with nitric oxide, and routes to nitrotyrosine formation. This is followed by a brief outline of studies involving the reactions of peroxynitrite-derived radicals with lipoic acid/dihydrolipoic acid, hydrogen sulphide, and the metal chelator desferrioxamine. For biological diagnostic probes such as ‘spin traps’ to be used with confidence, their reactivities with radical species have to be characterized, and the application of radiolysis methods in this context is also illustrated.     

Effect of Gamma Radiation on Glass Leaching

Significant increases in the leaching rate of PNL 76–68, a complex simulated nuclear waste glass, were observed to occur in the presence of gamma radiation. Some of the enhanced leaching is due to the generation of nitric acid from air radiolysis in the leach vessel. Nitric acid appears to preferentially attack zinc and lanthanides, both of which normally build up on the surface of the glass when leached in nonacidic solutions. Increased rates were also found for samples irradiated while leaching but with air excluded to eliminate nitric acid formation, indicating that water radiolysis products may also be important. Samples irradiated prior to leaching showed dissolution rates indistinguishable from those of unirradiated specimens.     

Synthesis, Spectral, Morphology, Thermal Degradation Kinetics and Antibacterial Studies of Terpolymer Metal Complexes

Terpolymer metal complexes involving transition metal ions such as Cu(II), Mn(II) and Zn(II) were prepared using a terpolymer ligand derived from anthranilic acid–phenyl hydrazine–formaldehyde (APHF). The terpolymer ligand and its metal complexes were intended to spectral characterizations viz. FTIR, electronic, ESR, ¹H NMR and ¹³C NMR to elucidate the structural confirmations. The number, weight, and size average molecular weights of the terpolymer ligand were determined by gel permeation chromatography (GPC). The empirical formula of the repeating unit for both the terpolymer ligand and its metal complexes was clearly justified by elemental analysis. The thermal stability of the ligand and its metal complexes was established by thermogravimetric analysis (TGA). On basis of the TGA data, the kinetic and thermodynamic parameters such as activation energy (E _a), order of reaction (n), entropy change (ΔS), apparent entropy (S*), frequency factor (Z) and free energy change (ΔF) were calculated using Freeman–Carroll and Sharp–Wentworth methods. Further the degradation mechanism for the thermal decomposition was also identified from Phadnis–Desphande method. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to establish the surface morphology and nature of the terpolymer ligand and its metal complexes. In addition, the terpolymer ligand and its metal complexes were screened against the growth of few bacteria and their inhibitions were measured and reported.