ABSTRACT
Oxidative degradation of ofloxacin (OFX) by sulfate free radicals (SO4 (-â¢)) in the UV/Oxone/Co(2+)oxidation process was investigated for the first time, with a special focus upon identifying the transformation products as well as understanding the reaction pathways. Thirteen main compounds were identified after the initial transformation of OFX; the detailed structural information of which were characterized by high-performance liquid chromatography-high resolution mass spectrometry and MS fragmentation analysis. The degradation pathways mainly encompassed ring openings at both the piperazinyl substituent and the quinolone moiety, indicating that the usage of SO4 (-â¢) aided the oxidative degradation of OFX to undergo more facile routes compared to those in previous reports by using OH(â¢)/h(+) as the oxidant, where the initial transformation attacks were mainly confined to the piperazine moiety. Moreover, in this study, smart control over the pH conditions of the oxidation system via different modes of Oxone dosage resulted in the selective degradation of the functional sites of OFX molecule, where it was shown that the SO4 (-â¢)-driven destruction of the quinolone moiety of OFX molecule favored the neutral pH conditions. This would be beneficial for the reduction of bacterial resistance against quinolones in the aqueous environment.
Subject(s)
Anti-Bacterial Agents/chemistry , Ofloxacin/chemistry , Oxidants/chemistry , Sulfuric Acids/chemistry , Water Pollutants, Chemical/chemistry , Chromatography, Liquid , Cobalt/chemistry , Mass Spectrometry , Oxidants/radiation effects , Oxidation-Reduction , Sulfates/chemistry , Sulfuric Acids/radiation effects , Ultraviolet RaysABSTRACT
To decrease single-wall carbon nanotube (SWCNT) lengths to a value of 100-200 nm, aggressive cutting methods, accompanied by a high loss of starting material, are frequently used. We propose a cutting approach based on low temperature intensive ultrasonication in a mixture of sulfuric and nitric acids. The method is nondestructive with a yield close to 100%. It was applied to cut nanotubes produced in three different ways: gas-phase catalysis, chemical vapor deposition, and electric-arc-discharge methods. Raman and Fourier transform infrared spectroscopy were used to demonstrate that the cut carbon nanotubes have a low extent of sidewall degradation and their electronic properties are close to those of the untreated tubes. It was proposed to use the spectral position of the far-infrared absorption peak as a simple criterion for the estimation of SWCNT length distribution in the samples.
Subject(s)
Crystallization/methods , Nanotubes, Carbon/chemistry , Nitric Acid/chemistry , Sonication/methods , Sulfuric Acids/chemistry , Cold Temperature , Complex Mixtures/chemistry , Complex Mixtures/radiation effects , Materials Testing , Nanotubes, Carbon/radiation effects , Nitric Acid/radiation effects , Particle Size , Sulfuric Acids/radiation effectsABSTRACT
The spectral radiation of sonoluminescence (SL) from sulfuric acid doped with various Xe concentrations has been studied in a hydrochemical simulation, including radiation effects of both continuum and line emissions. The simulation considers the same temperature for both continuum and line parts of the SL spectrum and gives results in agreement with the experiment. Also, it can properly show period-doubling dynamics for a 50 torr bubble. For most of the allowable driving pressures, it is shown that both the temperature and the intensity of SL for a 4 torr bubble are greater than those of a 50 torr bubble. However, for the range of pressures near the maximum driving conditions of the 50 torr bubble, the SL intensity of this bubble can be up to three orders of magnitude greater than the 4 torr bubble. This case, which is in agreement with the experiment, is obtained when the light-emitting region of the 50 torr bubble is about three orders of magnitude greater than the 4 torr bubble.
Subject(s)
Luminescent Measurements/methods , Models, Chemical , Sulfuric Acids/chemistry , Sulfuric Acids/radiation effects , Computer Simulation , TemperatureABSTRACT
Single-bubble sonoluminescence (SBSL) was explored under a variety of multifrequency excitations. In particular, biharmonic excitation was used to produce SBSL for unprecedented low dissolved noble gas concentrations in a sulfuric acid solution. Reducing the amount of dissolved noble gas makes it possible to reach higher acoustic pressures on the SL bubble, which otherwise are not attainable because of the Bjerknes instability. By using biharmonic excitation, we were able to experimentally trap and to spatially stabilize SL bubbles for xenon pressure overhead as low as 1 mbar. As a result, we have access to regions in phase space where the plasma temperatures are higher than the ones reached before for bubbles driven at ≈30 kHz.
Subject(s)
Luminescent Measurements/methods , Microbubbles , Models, Chemical , Sulfuric Acids/chemistry , Sulfuric Acids/radiation effects , Ultrasonography/methods , Computer Simulation , Radiation Dosage , SoundABSTRACT
Electrocatalysts of Pt-TiO2 were prepared by sol-gel and microwave assisted polyol method for the oxygen reduction reaction in acid media. The prepared electrocatalysts were morphologically and structurally characterized by X-Ray Diffraction, Scanning Electronic Microscopy and EDX analysis. Cyclic voltammetry and rotating disk electrode techniques were employed for electrocatalytic evaluation. It was found that electrocatalysts consisted of crystalline particles with nanometric size, and those obtained at pH = 9 showed an acceptable activity for the oxygen reduction reaction in acid media.
Subject(s)
Electrochemistry/methods , Heating/methods , Platinum/chemistry , Polymers/chemistry , Sulfuric Acids/chemistry , Titanium/chemistry , Catalysis , Materials Testing , Oxidation-Reduction/radiation effects , Phase Transition/radiation effects , Platinum/radiation effects , Polymers/radiation effects , Sulfuric Acids/radiation effects , Titanium/radiation effectsABSTRACT
Deprotection of oximes to the corresponding carbonyl compounds in silica sulfuric acid/surfactant/paraformaldehyde system can be carried out in excellent yields at 50 degrees C in water under ultrasound irradiation.
Subject(s)
Carbon/chemistry , Carbon/radiation effects , Oximes/chemistry , Oximes/radiation effects , Silicon Dioxide/chemistry , Sonication/methods , Sulfuric Acids/chemistry , Sulfuric Acids/radiation effects , Catalysis , Formaldehyde/chemistry , Formaldehyde/radiation effects , Polymers/chemistry , Polymers/radiation effects , Solutions/chemistry , Surface-Active Agents/chemistry , Surface-Active Agents/radiation effects , Water/chemistryABSTRACT
The mechanism of the inverse oxygen effect in the irreversible radiation-induced chemical alterations in protoporphyrin in sulfuric acid solution was investigated. The decrease of the molecular decay yield was shown to associate with the ability of oxygen to exclude H atoms from the radiation reactions and to inhibit the development of the protoporphyrin transformation chain process.
Subject(s)
Oxygen , Porphyrins/radiation effects , Protoporphyrins/radiation effects , Sulfuric Acids/radiation effects , SolutionsABSTRACT
The one-electron oxidation of horseradish peroxidase compound II to compound I by sodium periodate was observed. The bimolecular rate constant for the NaIO4--compound II interaction is equal to 9.5 +/- 1 x 10(-3) M-1s-1 at room temperature. Irradiation, using ultraviolet light, of the solution containing compound II and persulfate in the presence of bicarbonate, chloride, or bromide, leads ot the fast accumulation of compound I due to the oxidative action of SO4, CO3, Cl2, and Br2 anion radicals, which are products of the photolysis.
