Swelling Characterization of the Superabsorbent Copolymer in the Petroleum-Based Solvent-Water Mixtures

The crosslinked and porous copolymer grains were synthesized by inverse suspension polymerization of acrylamide. The synthesized copolymer was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). It was achieved to absorbed 418 g water by 1 g copolymer after 5 min waiting time. Moreover, it was seen that about 99% of water was absorbed by 1 g copolymer in the solvent water mixtures (300 mL solvent–200 mL distilled water) after 2.5 min waiting time. The diffusion coefficients of the copolymer in the solvent-water mixtures were found between 8.87 · 10⁴ and 10.64 · 10⁴ cm²s^?1. Furthermore, the copolymer in distilled water achieved to reach a high value of the diffusion coefficient (13.2 · 10⁴ cm²s^?1).     

A combined method for the determination of the isotopic vector of plutonium isotopes in environmental samples

A combination of alpha-spectrometry, liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) was used for the determination of plutonium isotopes. ²³⁸Pu and ^239+240Pu were measured by alpha-spectrometry after separation of Pu by anion-exchange using ²³⁶Pu tracer as recovery monitor. After alpha-measurement, one part of the sample was dissolved for determining ²⁴¹Pu by LSC. Another part was used for the measurement of the ²⁴⁰Pu/²³⁹Pu atom ratio by AMS at VERA. Thus, it was possible to obtain complete information on the Pu isotopic composition of the samples. This method was applied to environmental reference samples and samples contaminated from nuclear reprocessing.     

On the Aqueous Chemistry of the UIV–DOTA Complex

The 1,4,7,10-tetrazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) aqueous complex of U^IV with H₂O, OH⁻, and F⁻ as axial ligands was studied by using UV/Vis spectrophotometry, ESI-MS, NMR spectroscopy, X-ray crystallography, and electrochemistry. The U^IV–DOTA complex with either water or fluoride as axial ligands was found to be inert to oxidation by molecular oxygen, whereas the complex with hydroxide as an axial ligand slowly hydrolyzed and was oxidized by dioxygen to a diuranate precipitate. The combined data set acquired shows that, although axial substitution of fluoride and hydroxide ligands instead of water does not seem to significantly change the aqueous DOTA complex structure, it has an important effect on the electronic configuration of the complex. The U^IV/U^III redox couple was found to be quasi-reversible for the complex with both axially bonded H₂O and hydroxide, but irreversible for the complex with axially bonded fluoride. Intriguingly, binding of the axial fluoride renders the irreversible one-electron U^V/U^IV oxidation of the [U^IV(DOTA)(H₂O)] complex quasi-reversible, which suggests the formation of the short-lived pentavalent form of the complex, an aqueous non-uranyl chelated U^V cation.     

Study of the Fragmentation of D-Glucose and Alkylmonoglycosides in the Presence of Sodium Ions in an Ion-Trap Mass Spectrometer

Abstract

Using electrospray ion-trap mass spectrometry, the fragmentation of D-glucose and alkylmonoglycopyranosides (alkyl-GPs) was studied. In the presence of Na⁺, B₁ and ^0,2A fragmentations were observed. The alkyl-GPs also showed a ^2,5Afragmentation. A cluster containing no carbon atoms and adducts of this cluster with neutral molecules were observed. Standards of alkylmonoglycofuranosides (alkyl-GFs) were not available; however, their fragmentation was studied by high-performace liquid chromatography–mass spectrometry (HPLC-MS) and HPLC-MS² using an industrial mixture of alkylpolyglycosides. The cluster and its adducts were more easily formed by the alkyl-GPs than by the alkyl-GFs, but the ^0,2A cross-ring cleavage was more easily produced by the alkyl-GFs.     

Reexamination of the theory of exaltation of the migration current by preceding electrode reactions

The effect of the preceding current of Hg(CN)₂, CdSO₄, ZnSO₄, and HCl on the K⁺ wave, of Hg(CN)₂ and CuSO₄ on the Cd²⁺ wave, of CdSO₄ on the Zn²⁺ wave, and of Hg(CN)₂ and CdSO₄ on the IO^?₃ wave was investigated. No exaltation of the Cd²⁺ wave was observed and only small variations of the Zn²⁺ and IO^?₃ waves. The increase of the K⁺ waves was roughly in accord with the prediction of the theory of the so-called exaltation of migration currents by preceding electrochemical reactions. However, the exaltation can be explained by concomitant reactions of K-amalgam with water and electrochemical reduction of hydrogen, which are accelerated by other ions (and also by the ions involved in the preceding reactions) and which, consequently, invalidate the equation of the exaltation of migration currents.     

Mechanistic Features of the TiO2 Heterogeneous Photocatalysis of Arsenic and Uranyl Nitrate in Aqueous Suspensions Studied by the Stopped‐Flow Technique

The dynamics of the transfer of electrons stored in TiO₂ nanoparticles to As^III, As^V, and uranyl nitrate in water was investigated by using the stopped‐flow technique. Suspensions of TiO₂ nanoparticles with stored trapped electrons (e_trap^?) were mixed with solutions of acceptor species to evaluate the reactivity by following the temporal evolution of e_trap^? by the decrease in the absorbance at λ=600 nm. The results indicate that As^V and As^III cannot be reduced by e_trap^? under the reaction conditions. In addition, it was observed that the presence of As^V and As^III strongly modified the reaction rate between O₂ and e_trap^?: an increase in the rate was observed if As^V was present and a decrease in the rate was observed in the presence of As^III. In contrast with the As system, U^VI was observed to react easily with e_trap^? and U^IV formation was observed spectroscopically at λ=650 nm. The possible competence of U^VI and NO₃^? for their reduction by e_trap^? was analyzed. The inhibition of the U^VI photocatalytic reduction by O₂ could be attributed to the fast oxidation of U^V and/or U^IV.     

Preparation of actinide targets for the synthesis of the heaviest elements

The heaviest elements are synthesized in heavy-ion induced hot fusion reactions with various actinide targets. Because the actinide material is often available only in very limited amounts, a deposition method with high yields (~90 %) is needed. We report on the production of ²⁴⁴Pu, ²⁴³Am, ²⁴⁸Cm, ²⁴⁹Bk, and ²⁴⁹Cf targets on thin Ti backings by molecular plating. Different chemical purification steps using ion chromatographic techniques were applied for the purification of ²⁴⁹Cf and ²⁴⁴Pu. The deposition procedure applied for the production of ~0.4–0.8 mg/cm² thick targets is described. The deposition yield was determined either by α-particle or γ-ray spectroscopy. Furthermore, neutron activation analysis has been applied in the case of ²⁴⁴Pu, ²⁴³Am, and ²⁴⁸Cm. Information about the spatial distribution and homogeneity of the target layer was obtained by radiographic imaging.     

Origin of the oxygen in the oxidation of triphenylphosphine by potassium persulfate—application of the 18O isotope effect in 31P NMR

Potassium persulfate oxidizes triphenylphosphine to triphenylphosphine oxide in 60% aqueous acetonitrile. It has been suggested that the oxygen of the product, triphenylphosphine oxide, might originate from solvent water, following nucleophilic attack on an intermediate phosphonium ion. We have investigated the origin of the oxygen in the oxidation of triphenylphosphine by potassium persulfate in 60% aqueous acetonitrile containing 20% [¹⁸O]water. The product was analyzed by using the ¹⁸O isotope effect in ³¹P NMR spectroscopy. The magnitude of the ¹⁸O isotope-induced shift was determined by synthesizing triphenylphosphine [¹⁸O]oxide and was found to be 0.038 ppm upfield. The product of the oxidation reaction in 20% [¹⁸O]water displayed no ¹⁸O isotope effect. The origin of the oxygen in the oxidation reaction is the persulfate ion, consistent with an alternative mechanism involving nucleophilic attack by water at the sulfur atom of a phosphonium peroxysulfate intermediate.     

Effect of the specific activity of the tracer on rat luteinizing hormone radioimmunoassay

Rat luteinizing hormone /LH/ was labelled with¹²⁵I by the Chloramine T method.¹²⁵I-LH, used as tracer in radioimmunoassay, was separated from the labelling reaction mixture by gel filtration. By using the proper protein/radioiodine ratio in the labelling reaction mixture the specific activity of¹²⁵I-LH was adjusted to 2.5–20.5 MBq g^–1. The influence of the specific activity on the assay parameters as well as on the tracer stability was investigated.     

Production of artifact methylmercury during the analysis of certified reference sediments: use of ionic exchange in the sample treatment step to minimise the problem

Production of artifact methylmercury (MeHg⁺) during the analysis of two certified reference sediments, CRM-580 and IAEA-405, was investigated. Leaching of the analyte from the solid sample was achieved by ultrasound assisted acidic extraction. The aqueous leachate was either ethylated (NaBEt₄) or phenylated (NaBPh₄) using acetic/acetate or citric/citrate to buffer the solution. Preconcentration of the volatile compounds was carried out by extraction with an organic solvent (n-hexane) or solid phase microextraction (SPME). MeHg⁺ was finally separated and detected by gas chromatography with atomic emission or mass spectrometry detection (GC-MIP-AED or GC-MS). In all the cases the concentrations obtained for MeHg⁺ in the CRM-580 were significantly higher than the certified value. For the IAEA-405, however, the MeHg⁺ concentration found was always statistically indistinguishable from the certified value. Experiments were also conducted with synthetic samples, such as aqueous mixtures of MeHg⁺ and inorganic mercury (Hg²⁺) or silica-gel spiked with both compounds. The methylation rates found (defined as the percentage of Hg²⁺ present in the sample which methylates to give artifact MeHg⁺) ranged from not observable (in certain synthetic aqueous mixtures) to 0.57% (analysis of CRM-580 under certain conditions). As the amount of Hg²⁺ available in the sample seems to be the main factor controlling the magnitude of the artifact, several experiments were conducted using an ionic exchange resin (Dowex M-41) in order to minimise the concentration of this chemical in the reaction medium. First, a hydrochloric leachate of the sample was passed through a microcolumn packed with the exchanger. Second, the resin was mixed with the sample prior to extraction with HCl. In both cases, the predominant Hg²⁺ species, HgCl₄²⁻, was adsorbed on the resin, whereas MeHg⁺, mainly as MeHgCl, remained in solution. Following the second option, a new method to analyse MeHg⁺ in conflictive matrices like certain sediments was proposed. This approach produced better results for the CRM-580, but a MeHg⁺ concentration slightly, but statistically significant, higher than the reference value was still obtained.     

Evaluation of the radioactivity in concrete from accelerator facilities

For evaluation of radioactivity induced in the concrete samples from accelerator facilities, the residual radioactivity in concrete sample, collected from seven accelerator facilities, was determined by γ-ray spectrometry. The tritium was extracted by the heating method using an IR furnace, and measured with a liquid scintillation counter. It was found that the major radioisotopes activated mainly by neutrons in the concrete samples were ¹⁵²Eu, ⁶⁰Co, ¹³⁴Cs and ³H. The concentrations of radioactivities induced by thermal neutron capture are the highest at a depth of 10 cm in the concrete wall. The correlation between tritium, ⁶⁰Co and ¹⁵²Eu activity was investigated by measuring many concrete samples for seven accelerator facilities. The results indicate that their activities are strongly correlated with each other. So it would also be concluded that the total activity in shielding concrete could be estimated on the basis of the activities of ⁶⁰Co and ¹⁵²Eu.     

Determination of the attenuation of epicadmium neutrons using the method of varying Cd-thickness

A new approach is presented for experimental determination of the cadmium correction factor F_Cd using the method of varyind Cd-thickness. In this method, the shift of the effective Cd cut-off value by varying the Cd-thickness was taken into consideration F_Cd for the following isotopes was determined with 1 mm cadmium covers^110mAg,^114mIn,¹²²Sb,¹⁴⁰La,¹⁵³Sm,^116mIn,¹⁶⁰Tb,¹⁶⁶Ho,^176mLu,¹⁸⁸Re,¹⁹²Ir,¹⁹⁴Ir¹⁹⁸Au,²³³Pa and²³⁹Np.     

Swelling Capacity of Montmorillonite in the Presence of Electrolytic Ions

The aim of this study was to investigate the effect of inorganic cations (Na⁺, Ca²⁺, Ba²⁺, Fe³⁺, Al³⁺) with different valence and concentration on the swelling behaviors of montmorillonite. Na-montmorillonite, obtained from China, was chosen as experimental objective. It was first characterized through the measurements of swelling capacity and zeta potential. Then, swelling properties of Na-montmorillonite influenced by cation concentration, valence, and hydration analyzed were studied. The results showed that the swelling capacity was much inhibited by cations of higher concentrations, higher valences, or weaker hydration. This work also verified the conclusion that the decreased degree of potential is more significant caused by cations of higher valence.     

Determination of the Rate Constant of the Reaction of CCl2 with HCl

The rate constant of the reaction between CCl₂ radicals and HCl was experimentally determined. The CCl₂ radicals were obtained by infrared multiphoton dissociation of CDCl₃. The time dependence of the CCl₂ radicals' concentration in the presence of HCl was determined by laser‐induced fluorescence. The experimental conditions allowed us to associate the decrease in the concentration of radicals to the self‐recombination reaction to form C₂Cl₄ and to the reaction with HCl to form CHCl₃. The rate constant for the self‐recombination reaction was determined to be in the high‐pressure regime. The value obtained at 300 K was (5.7 ± 0.1) × 10^?13 cm³ molecule^?1 s^?1, whereas the value of the rate constant measured for the reaction with HCl was (2.7 ± 0.1) × 10^?14 cm³ molecule^?1 s^?1.     

Study of alkaloids from the flora of the Siberian and Altai regions. 6. Crystal and molecular structure of songorine Z-oxime

Oximation of songorine afforded a mixture of its Z- and E-oximes. The crystal and molecular structure of the Z-isomer was established by X-ray diffraction analysis. Its structure was also confirmed by the spectral data (2D ¹H—¹H and ¹³C—¹H NMR spectroscopy and mass spectrometry). The structure of isomeric E-oxime was established by comparing its NMR spectroscopic data (¹H and ¹³C) with the data for the Z-isomer.     

1H NMR: a tool to study the fate of pollutants in the environment

In situ ¹H NMR, directly performed on biological fluids is a very powerful tool to study the fate of pollutants in the environment. The biodegradation of 2-aminobenzothiazole by Rhodococcus rhodochrous was monitored by reverse phase HPLC and by in situ ¹H NMR, methods performed directly on culture media without purification. The xenobiotic was biotransformed into a hydroxylated derivative. The chemical structure of this metabolite was determined by a long-range ¹H–¹⁵N heteronuclear shift correlation without any previous ¹⁵N enrichment of the compound. This approach allowed the assignment of the metabolite structure to 2-amino-6-hydroxybenzothiazole.     

Synthesis of Schiff bases on the basis of the isosteviol terpenoid

The transformation of the carboxy and keto groups of the isosteviol (ent-16-ketobeyeran-19-oic acid) diterpenoid was used to synthesize its new nitrogen-containing derivatives, including Schiff bases by the C⁴ and C¹⁶ atoms of the isosteviol frame. The structure of the resulting compounds was established by X-ray diffraction.     

水溶液中掺铬层状二氧化锰可充性研究

由高温分解KMnO₄制备层状K-birnessite前驱体, 再经过离子交换反应制备Cr-birnessite. 在2.5 mol/L LiOH水溶液中研究了Cr-birnessite电极的可充性. 据AAS测试和锰的价态分析得Cr-birnessite的分子式为Cr_0.26Mn_0.84O_2＋0.04. SEM显示Cr-birnessite为片状颗粒, XRD分析表明其层状结构在充放电前后没有明显变化. 恒电流充放电实验表明在2.5 mol/L LiOH水溶液中以1 C大电流速率对Cr-birnessite进行全充全放循环可达70次而保持初始容量的93%, 显示了良好的循环可逆性. AAS表明在充放电过程中材料中的铬离子没有脱嵌, Li^＋脱嵌/嵌入. 循环伏安曲线表明在大约 －0.3和0 V出现两个氧化峰, 在－0.1 V左右出现一个还原峰, 循环20周电流大小没有明显变化. 利用恒电位阶跃法测得Li^＋在Cr-birnessite 中的扩散系数平均值为1.57×10^－10 cm²·s^－1 .     

Chemiluminescence in the reaction of the RuII trisbipyridyl complex with dimethyldioxirane

The reaction of dimethyldioxirane (1) with the Ru^II trisbipyridyl complex accompanied by chemiluminescence (CL) was studied. It is established that the intensity of CL and the rate of its decay increase proportionally with the concentration of Ru^II. The bimolecular rate constant (k ₂) of the reaction of1 with Ru^II was determined. The activation parameters (E _a and logA) for this reaction were calculated from the temperature dependence ofk ₂. The excitation yield of Ru^II* (η _Ru ^* ) was estimated. The quenching of Ru^II* by dioxirane was studied, and the bimolecular quenching constant and the coefficient of excitation regeneration were determined. It was suggested that the catalysis of the decomposition of1 and the excitation of Ru^II occurvia a mechanism of chemically initiated electron exchange. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1138–1142, June, 1997.