Degradation of Erioglaucine Dye Under γ-irradiation

The kinetics and the mechanism degradation of erioglaucine dye in aqueous solution irradiated under γ-rays from ⁶⁰Co are investigated. From the results of the absorption UV-Vis spectra of 0.7 mM erioglaucine solution as function of dose, the concentration of erioglaucine decreases exponentially with increasing the γ-irradiation dose and the plot on a logarithmic scale against the dose shows a clear pseudo first order rate. The apparent pseudofirst order rate constant (kapp= 1.8¥10^-3 min^-1) was calculated. We also found the degradation mechanism as results of mass-spectrum analyses of the degradation products under the γ-irradiated erioglaucine solution. The results show that the principal cleavage is the C-N bond.     

The radiation-induced degradation of a diazo dye in aqueous solution,II

The effect of -radiation on the color intensity of aerated, deaerated and oxygenated aqueous solutions of a diazo dye (Helion Red 8B) has been investigated. The decoloration yields of Helion Red 8B neutral aqueous solution, G(-Dye), for the nitrogen-, oxygen- and aerated-saturated solutions were found to be 0.77, 0.46 and 0.36 in the respective early stage. The rate constant for the reaction of the OH radical with the HR8B dye, obtained from competition kinetics using ethanol, was found to be 1.3·10¹⁰ M^–1·s^–1. In aerated solutions (pH 3), the G(-Dye) decreased markedly upon the addition of a very small amount of ethanol. Suggestions are made for possible use of the dye as a radiation dosimeter in the dose range of 0.1 to 2 kGy.     

High energy induced decoloration and mineralization of Reactive Red 120 dye in aqueous solution: A steady state and pulse radiolysis study

Gamma radiation induced decoloration and degradation of aqueous solution of Reactive Red 120 dye (RR-120) have been investigated under different experimental conditions. Rate constants for the reaction of hydrated electron and hydroxyl radical with RR-120 were determined to be 1.2×10¹⁰ and 7.9×10⁹ mol^?1 dm³ s^?1, respectively, by pulse radiolysis technique. The decoloration and degradation efficiency were measured in terms of % decoloration and % TOC, respectively. Decoloration was observed to be most efficient under reducing condition, where the radiolytic yield for the decoloration of dye was determined to be 0.14 μmol/J. The extent of decoloration for both aerated and oxygen saturated solution was almost identical, whereas it decreased in N₂O saturated solution as well as N₂ saturated solution. For a solution having 10.56 μg/ml total organic carbon (TOC) at a dose of 3 kGy, 48% mineralization takes place in oxygen saturated solution whereas under aerated condition same was observed to be lowered to 38%.     

Gamma radiolysis of morin

Gamma irradiation studies of morin (10^–5M) in ethanol and dimethyl sulphoxide (DMSO) in the dose range of 149–895 Gy and of 4.5–45 Gy were carried out, respectively, in aerated and anoxic conditions purged with nitrogen and nitrous oxide. The decoloration yield of morin was studied as a function of dose. The relative radiation sensitivity was estimated under similar conditions. The effect of the concentration (10^–5–10^–4M) of iodine, succinic acid and acryl amide on radiolysis of morin was investigated at constant dose in both solvents and results were interpreted in terms of scavenging reactions.     

Kinetic characteristics of initiated oxidation of limonene

The kinetics of oxygen absorption .n the process of limonen (4-isopropenyl- l-methulcyclohex-1-ene) oxidation was studied in chlorobenzene solution at 40–80 °C. The values of the kinetic parameters of oxidation and the activation energy (38.1 kJ mol^–1) have been determined. The nonlinear dependence of the rate of the oxidation of limonene on its concentration has been established, The rate constants of the chain termination reactions were estimated by chemiluminescence techniques.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1676–1681, July, 1996.     

Radiolysis of U(VI)-arsenazo-1 complex in aqueous solutions

The effect of absorbed dose on the decolouration of U(VI)-arsenazo-1 complex solutions has been investigated at pH 8.3. G-values were determined as a function of complex concentration as well as of OH, e _aq ^– scavengers. Using competition kinetics, rate constants were determined and the degradation mechanism discussed.     

Radiation deterioration in mechanical properties and ion exchange capacity of Nafion N117 swelling in water

The base form Nafion N117 samples swelling in the oxygen-saturated distilled water were irradiated with γ-rays or with electron beams at various doses up to 1600 kGy at room temperature or at 343 K to obtain detailed information on the effect of oxygen on the radiation deterioration in the Nafion mechanical properties and in the ion exchange capacity. The contribution of the radical reactions where oxygen molecules did not participate was dominant for the radiation deterioration in the mechanical properties of the Nafion N117 membrane swelling in the oxygen-saturated distilled water at room temperature. The effect of oxygen molecules was not significant due to the little oxygen concentration in the distilled water even though oxygen was saturated in the water. The Nafion N117 membrane irradiated with γ-rays at 343 K became a weak and brittle material, since the rise of the temperature activated the reactions. Oxygen molecules, in contrast, have negligible part in the reactions at 343 K due to their lower solubility in the water. We observed the negligible effect of the radiation sources as well as of the dose rate below 10 kGy/h on the radiation deterioration in Nafion N117 mechanical properties at room temperature. The irradiation of the Nafion membrane with γ-rays or with electron beams is one of the acceleration tests of the Nafion degradation. We made clear that the dissolved fluorine measured using a fluoride ion meter is a hopeful index for the in situ judging of the Nafion mechanical deterioration. The ion exchange capacity of the membrane irradiated up to 1600 kGy was the 20% decrease of the initial capacity at room temperature. Nafion side chains terminating with –SO₃⁻ M⁺ groups were radiation-durable compared with the backbone.     

Paramagnetic Centers in Irradiated Potassium Picrate

The formation of paramagnetic centers in potassium picrate in a radiation field was found using EPR spectroscopy. Stable paramagnetic centers were identified as 2,6-dinitro-para-quinone, iminoxyl, and ^– radicals. The kinetics of buildup of stable paramagnetic centers was studied over a wide dose range (0.14–5 MGy), and the temperature stability was studied at 77–550 K. It was found that the decay of paramagnetic centers in the temperature range 373–523 K obeyed the laws of polychronous kinetics. A reaction scheme for the radiation-thermal decomposition of sodium picrate with the participation of radical radiolysis products was proposed.     

Gamma radiolysis of anthraquinone dye aqueous solution

The decoloration of Acid Blue 62 in aqueous solution was mainly attributed to the attack of the e _aq ^– and OH radicals on the dye molecule. The mechanisms of these reactions were investigated in detail including the influence of pH, dose rate and oxygen.     

Determination of Oxygen in Halide Fluorotantalate Melts by IR Spectroscopy

The possibility of determining oxygen as impurity in halide melts containing potassium heptafluorotantalate by IR spectroscopy was investigated. These melts are used for obtaining tantalum powders by the sodium–thermal method. It was found that a linear correlation exists between the oxygen concentration in the melt c _O(c _O= 0.05–1.0 wt %) and the ratio of intensities of IR absorption lines in the region of 1200–400 cm^–1. This correlation can be used for determining oxygen in the melt and for predicting the concentration of this element in sodium–thermal tantalum powders.     

On the characteristics and mechanism of the radiation-induced chain reaction between sulfur dioxide and molecular oxygen in acid solutions

Characteristics of the -induced chain reaction between sulfur dioxide and molecular oxygen in perchloric and sulfuric acid media in the presence of Ce(III) ions have been studied. The concentration effects of dissolved oxygen (0.2·10^–3–9.4·10^–3 mol/dm³, sulfur dioxide (0.3·10^–1–2.0·10^–1 mol/dm³ and Ce(III) (0.2·10^–3–4.8·10^–3 mol/dm³) and dose rate (0.26·10¹⁹–1.0·10¹⁹ eV/dm³·s) on the radiation — chemical yield of oxygen consumption G(–O₂) and accumulation of sulfate G(HSO ₄ ^– ), have been investigated. The reaction proceeds with G(–O₂) reaching 10²–10³ molecule/100eV in a catalytic regime. The reaction rate in perchloric acid medium is 3–4 times lower than that in the sulfuric acid medium and depends on the SO₂, O₂ and Ce(III) concentrations, the reaction order varying from 1.0 to 0 and/or in the reverse direction. The mechanism of the process involves chain propagation with 3 stages and 3 intermediates: SO₃H, HSO₅ and Ce(IV). The catalytic effect is caused by the interaction of HSO₄ with Ce(IV) ions followed by their reduction when interacting with SO₂, yielding SO₃H radicals. Chain termination may be due to one or two of the three intermediates or due to all three particles, the kinetics depending on this. Kinetic equations describing the experimental data have been obtained.     

Degradation of 4-chlorophenol in aqueous solution by γ-radiation and ozone oxidation

The degradation of 4-chlorophenol (4-CP) by using gamma rays generated by a ⁶⁰Co source in the presence of O₃ was investigated. The radiolysis of 4-CP and the kinetics of 4-CP mineralization were analyzed based on the determination of total organic carbon (TOC). The influence of initial 4-CP concentration and the free radicals scavengers (such as NaHCO₃ and t-butanol) on the 4-CP degradation was also studied. The results showed that when the radiation rate was 336 Gy·min⁻¹, 4-chlorophenol at concentration of 10 mg·L⁻¹ could be completely degraded at the radiation dose of 2 kGy. The degradation of 4-chlorophenol could be described by a first-order reaction model, the rate constant of 4-CP degradation by combined ozonation and radiation was 0.1016 min⁻¹, which was 2.4 times higher than the sum of radiation (0.0294 min⁻¹) and ozonation (0.0137 min⁻¹). It revealed that the combination of radiation and ozonation resulted in synergistic effect, which can remarkably increase the degradation efficiency of 4-CP.     

Wavelength modulation diode laser atomic absorption spectrometry in analytical flames

The potential of wavelength modulation laser atomic absorption spectrometry in analytical flames is demonstrated by the measurement of titanium, cesium and chromium applying fundamental and frequency doubled radiation of commercially available semiconductor diode lasers. In dependence on the radiation power, absorbances of the order of 10⁻⁴–10⁻⁶ are measured, which reveal very low detection limits even when weak absorption lines are used.     

Phenol Degradation Features in Aqueous Solutions upon Dielectric-Barrier Discharge Treatment

The formation kinetics and mechanism were studied for the intermediate and final products of degradation of aqueous phenol solutions in air and oxygen low-temperature dielectric-barrier discharge plasmas in a reactor with different geometric arrangements of electrodes. It was shown that the plasma-enhanced oxidation of phenol could be described in the general form by the well-known mechanism of enzymatic oxidation of toxic pollutants (-mechanism). The estimated effective rate constant of phenol degradation in an aqueous solution in an ₂ plasma in reactors with the parallel-plate and coaxial arrangement of electrodes was 2.2 × 10^–3 s^–1 and 5.8 × 10^–2 s^–1, respectively. It was found that the potential toxicity of solutions after treatment was 7.5 times lower than that of the untreated solutions.     

The kinetics and mechanism of the oxidation of DL ethionine and thiourea by potassium ferrate

The kinetics of the reaction between ethionine and thiourea were investigated under pseudo and non-pseudo-first-order conditions. Ethionine was oxidized to the sulfoxide within 500 s and thiourea was oxidized to urea within 10 s. Above a pH of ca. 8.5 the reaction was first-order in the concentration of the organosulfur compound, the hydrogen ions and the ferrate ions, whereas, below this pH, the kinetics were independent of the hydrogen ion concentration. A possible mechanism for both compounds is initial protonation of the ferrate ion followed by the two electron rate-determining step of addition of oxygen to the organosulfur compound. The kinetic parameters for ethionine compare favorably with those for similar compounds, whereas thiourea tends to be more active. The rate constant for the rate-determining step is 4.1 × 10² M^–1 s^–1 for ethionine and 4.1 × 10³ M^–1 s^–1 for thiourea.     

Photometrische Bestimmung von Iod und Iod-freisetzenden Oxidationsmitteln

Zusammenfassung Zwischen der Extinktion bei 350 nm und der Gesamtiodkonzentration von iodidhaltigen, wäßrigen Lösungen besteht unabhängig vom pH-Wert ein weitgehend linearer Zusammenhang, der zur quantitativen Bestimmung von Iod und Iod-freisetzenden Oxidationsmitteln herangezogen werden kann. Bei Verwendung eines Spektralphotometers mit einer Ablesbarkeit von 0,0001–3,0 E und 1,0 bzw. 0,1 cm Küvetten reicht der Meßbereich unter den gewählten Bedingungen von <10^–7 bis 1,3×10^–3 m/l, wobei als Nachweisgrenze 3,3×10^–8 m/l ermittelt wurde.Mit relativen Standardabweichungen von 0,3–0,6, 0,8 bzw. 4,0% in den Konzentrationsbereichen 10^–3–10^–5. 10^–6 und 10^–7 m/l ist die Präzision der photometrischen Iobestimmung signifikant besser als die der amperometrischen Titration, welche zur Zeit als genaueste Methode zur Bestimmung von Halogenen and anderen starken Oxidationsmitteln anerkannt wird. Die Vorteile der Methode, die aufgrund des äußerst geringen meßtechnischen Aufwandes besonders für Reihen- und Routineuntersuchungen geeignet ist, werden im einzelnen an Hand eines Vergleiches mit der potentiometrischen Iodbestimmung [1] bzw. anderen photometrischen Methoden aufgezeigt.

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Photometric determination of iodine and iodine-releasing oxidants

Summary Between the absorption at 350 nm and the total iodine concentration of aqueous solutions containing an excess amount of iodide exists a nearly linear relation independent of the pH-value over a concentration range of more than 4 powers of ten. This enables a simple and precise determination of iodine and iodine releasing oxidants. Using a spectrophotometer with a readability of 0.0001 to 3.0 absorption units and 1.0 resp. 0.1 cuvettes the measuring range comprises under the selected conditions <10^–7 to 1.3 ×10^–3 m/l with a detection limit of 3.3×10^–8 m/l (at pH 7).With relative standard deviations of 0.3 to 0.6, 0.8 resp. 4.0% in the concentration range 10^–3 to 10^–5, 10^–6 and 10^–7 m/l the precision of the photometric determination of iodine is clearly better than that of the amperometric titration (at present accepted as most precise method for the determination of halogens and other strong oxidants). The method (requiring only a very simple instrumental equipment) is suited especially for routine and serial investigations. Its advantages are demonstrated in particular on the basis of comparison with the potentiometric determination of iodine [1] resp. other photometric methods.

     

Simultaneous determination of sodium dodecyl sulphate and sodium linear-dodecylbenzenesulphonate with 1-stearyl-4-(4-aminonaphthylazo)-pyridinium bromide by spectrophotometry

A rapid and sensitive spectrophotometric method for the simultaneous determination of sodium dodecyl sulphate (SDS) and sodium linear-dodecylbenzenesulphonate (DBS) with 1-stearyl-4-(4-aminonaphthylazo)-pyridinium bromide (SAPB) is described using the difference at the maximum absorption wavelength of the SDS- and the DBS-ion associate. SDS and DBS have been determined independently by measuring their respective absorbances at the maximum absorption wavelength. The apparent molar absorptivities of the SDS- and the DBS-ion associate are 8.0×10⁴ l mol^–1 cm^–1 at 445 nm and 4.5×10⁴ l mol^–1 cm^–1 at 424 nm, respectively. The calibration graph for SDS is linear in the range from 0.1 to 1.0×10^–6 mol/l in the presence of 1.2×10^–6 mol/l DBS and for DBS from 0.8 to 2.0×10^–6 mol/l in the presence of 8.0×10^–7 mol/l SDS. The relative standard deviation (n=15) for 8.0×10^–7 mol/l SDS is 3.4% and for 1.6×10^–6 mol/l DBS 2.1%. The proposed method has been applied to the simulatenous determination of SDS and DBS in river water samples.     

Spectral characteristics of the bands of NH groups and structure of 2-thioxobenzazolines in solvents with low polarities

The IR spectra of five 2-thioxo-benzazolines in carbon tetrachloride (2500–3500 cm^–1) and chloroform (3200–3500 cm^–1) are examined. Analysis of the spectral parameters of the absorption band of the unassociated NH groups showed that the high proton-donor capacity of the hydrogen atom of the thioamide group of 2-thioxobenzoxazoline is evidently associated with the high electronegativity of the oxygen atom. The existence of intermolecular hydrogen bonds with a degree of dissociation of 0.3 in carbon tetrachloride and 0.1 in chloroform was established by means of the concentration dependence of the spectra. A change with time in the integral coefficient of the absorption band of the unassociated NH groups was observed in solutions in carbon tetrachloride; this is explained by interaction of the 2-thioxobenzazolines with carbon tetrachloride. The IR spectra, a table of the spectral characteristics, the dependence of the relative integral intensity on the concentration, and the dependence of the optical density of the absorption band of free NH groups on time are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 69–71, January, 1979.     

Effect of gamma-rays on the formation of color centers in copper-containing lead borate glasses

Absorption bands in the range of 350–950 nm, induced in copper-containing lead borate glasses by -rays were identified and characterized. The effect of irradiation dose, copper oxide and lead oxide contents on the intensity and position of the induced absorption bands were also considered. Several induced absorption bands were observed. At least two bands in the ranges of 740–780 and 850–870 nm could be identified. They are suggested to be associated with induced Cu⁽²⁺⁾ ions. The band in the 800–830 nm (1.6 eV) range is ascribed to the Pb⁽³⁺⁾ ion, whereas others in the ranges of 600–630 and 650–730 nm are associated with the intrinsic defects formed in the base glass.     

Facile ion-exchange synthesis of Gd-doped K2Ta2O6 photocatalysts with enhanced visible light activity

One of the well-known ways of increasing the visible light absorption capability of semiconducting materials is cation doping. This study aims to use Gd doping to tailor the bandgap energy of K₂Ta₂O₆ (KTO) for photocatalytic degradation of organic pollutants under visible light irradiation. Accordingly, the parent KTO and Gd-doped KTO with different Gd concentrations (K_2-3xGd_xTa₂O₆; x = 0.025, 0.05, 0.075 and 0.1 mol%) were synthesized by hydrothermal and facile ion-exchange methods, respectively. The powder XRD, FT-IR, SEM-EDS, TEM-SAED, N₂ adsorption-desorption, XPS, UV–Vis DRS, PL and ESR techniques were used to investigate the effect of Gd dopant concentration on the structural and photocatalytic properties of KTO. The photocatalytic activity of these samples was investigated for the photocatalytic degradation of methylene blue (MB) dye in an aqueous solution at room temperature under visible light irradiation. The experimental results show that all Gd-doped KTO samples exhibit enhanced photocatalytic activity compared with parent KTO toward MB degradation. In particular, Gd-KTO obtained by doping of 0.075 mol% shows the highest photocatalytic activity among the Gd-doped samples and the degradation efficiency of MB was 79% after 180 min of visible light irradiation, which is approximately 1.5 times as high as that by parent KTO (53%). In addition, trapping experiments and electron spin resonance (ESR) analysis demonstrated that the hydroxyl radicals (^?OH) have played a crucial role in the photocatalytic degradation of MB. The reusability and stability of Gd doped-KTO with a Gd content of 0.075 mol% against MB degradation were examined for five cycles. Based on the present study results, a visible light induced photocatalytic mechanism has been proposed for Gd0075-KTO sample.