共查询到20条相似文献,搜索用时 31 毫秒
1.
A rapid and efficient treatment method, using periodate (PI) for sonochemical oxidation of persistent and bioaccumulative perfluorooctanoic acid (PFOA) was developed. With an addition of 45 mM PI, 96.5% of PFOA was decomposed with a defluorination efficiency of 95.7% after 120 min of ultrasound (US). The removals of PFOA were augmented with an increase in PI doses. In all the PI + US experimental runs, decomposition efficiencies were essentially similar to those of defluorination, indicating that PFOA was decomposed and mineralized into fluoride ions. Lower solution pHs resulted in an increase in decomposition and defluorination efficiencies of PFOA due to acid-catalyzation. Dissolved oxygen increased the amount of IO4 radicals produced, which consumed the more effective IO3 radicals. Consequently, presence of oxygen inhibited the destruction of PFOA. The PFOA degradation rates with different gases sparging are in the following order: nitrogen > air > oxygen. Effects of anions follow the Hofmeister effects on PFOA degradation (i.e., Br− > none ⩾ Cl− > SO42−). Br− could react with OH to yield radical anion Br2− that enhances the PFOA degradation. A reaction pathway was also proposed to describe the PI oxidation of PFOA under US irradiation. 相似文献
2.
Wei Liu Juan Kou Xiaoli Jiang Zhujun Zhang Honglan Qi 《Journal of luminescence》2012,132(4):1048-1054
A highly sensitive chemiluminescence (CL) method for the determination of nitrofurans (NFs) was developed based on the enhancement of CL intensity of luminol–H2O2–NFs system by silver nanoparticles (AgNPs). It was supposed that the oxygen-related radicals of OH and superoxide radical (O2?) could be produced when NFs reacted with H2O2. Furthermore, the enhancement mechanism was originated from the reinforcer of AgNPs, which could catalyze the generation of the OH radical. Then OH radicals reacted with luminol anion and HO2? to form luminol radical (L?) and O2?. The excited state 3-aminophthalate anion was obtained in the reaction of L? and O2?, which was the emitter (luminophor) in the luminol–H2O2 CL reaction system and the maximal emission of the CL spectrum was at 425 nm. The experiments of scavenging oxygen-related radicals were done to confirm these reactive oxygen species participated in the CL reaction. The limits of detection (LOD) (S/N=3) were 8×10?7 g mL?1 for furacilin, 8×10?8 g mL?1 for furantoin, 4×10?8 g mL?1 for furazolidone and 2×10?7 g mL?1 for furaltadone. The proposed method was successfully applied to the determination of NFs in feeds and pharmaceutical samples. 相似文献
3.
《Solid State Ionics》2006,177(1-2):1-9
Oxygen re-equilibration kinetics, along with the equilibrium conductivity, have been measured on undoped, single-crystal TiO2−δ, by a four-probe d.c. conductivity relaxation technique, against oxygen partial pressure in the range of − 16 < log(PO2/atm) ≤ 0 at different temperatures in the range of 1173 ≤ T/K ≤ 1373. The isothermal conductivity varies as σ ∝ PO2m with m ≈ − 1/4, − 1/5 and − 1/6 in turn with increasing PO2 up to 1 atm, suggesting a sequential variation of the majority ionic disorder types from Tii to Tii to VO, respectively. Contrary to the conventional knowledge that due to the local (defect) equilibrium postulate there should be one and only one chemical diffusivity or single relaxation time for a binary oxide, the oxygen re-equilibration kinetics has turned out to be twofold with two different relaxation times depending on oxygen activities. This is interpreted as being due to the independent relaxation of each sublattice of TiO2 in an oxygen activity gradient applied, indicating a failure of local equilibrium during oxygen re-equilibration. From the two different relaxation times the chemical diffusion coefficients of component Ti and O are separately evaluated and subsequently, their self-diffusion coefficients. The latter are found to be in a good agreement with the literature data. 相似文献
4.
《Solid State Ionics》2006,177(19-25):1925-1928
Nonstoichiometry of the perovskite-type solid solutions La0.9Ca0.1Cr1−yAlyO3−δ was studied by high-temperature gravimetry under controlled P(O2) atmospheres of 1–10− 23 bar at 1073–1273 K. The observed data were described by a regular solution-like model for the randomly distributed defects of VO¨, CrCr., CaLa,, and AlCrX. With the increase in y, VO¨ formation becomes much easier. For y > 0.8, some fraction of CaLa, becomes surrounded only by AlCrX and VO¨ remains around such CaLa, up to high P(O2) to reduce the maximum oxygen content below 3.000. 相似文献
5.
《Ultrasonics sonochemistry》2014,21(1):53-59
Formation of highly reactive species such as OH, H, HO2 and H2O2 due to transient collapse of cavitation bubbles is the primary mechanism of sonochemical reaction. The crucial parameters influencing the formation of radicals are the temperature and pressure achieved in the bubble during the strong collapse. Experimental determinations estimated a temperature of about 5000 K and pressure of several hundreds of MPa within the collapsing bubble. In this theoretical investigation, computer simulations of chemical reactions occurring in an O2-bubble oscillating in water irradiated by an ultrasonic wave have been performed for diverse combinations of various parameters such as ultrasound frequency (20–1000 kHz), acoustic amplitude (up to 0.3 MPa), static pressure (0.03–0.3 MPa) and liquid temperature (283–333 K). The aim of this series of computations is to correlate the production of OH radicals to the temperature and pressure achieved in the bubble during the strong collapse. The employed model combines the dynamic of bubble collapse in acoustical field with the chemical kinetics of single bubble. The results of the numerical simulations revealed that the main oxidant created in an O2 bubble is OH radical. The computer simulations clearly showed the existence of an optimum bubble temperature of about 5200 ± 200 K and pressure of about 250 ± 20 MPa. The predicted value of the bubble temperature for the production of OH radicals is in excellent agreement with that furnished by the experiments. The existence of an optimum bubble temperature and pressure in collapsing bubbles results from the competitions between the reactions of production and those of consumption of OH radicals at high temperatures. 相似文献
6.
Ruiyang Xiao David Diaz-Rivera Ziqi He Linda K. Weavers 《Ultrasonics sonochemistry》2013,20(3):990-996
Hydroxyl radical (OH) scavengers are commonly used in sonochemistry to probe the site and nature of reaction in aqueous cavitational systems. Using pulsed wave (PW) ultrasound with comparative sonochemistry we evaluated the performance of OH scavengers (i.e., formic acid, carbonic acid, terephthalic acid/terephthalate, iodide, methanesulfonate, benzenesulfonate, and acetic acid/acetate) in a sonochemical system to determine which OH scavengers react only in bulk solution and which OH scavengers interact with cavitation bubbles. The ability of each scavenger to interact with cavitation bubbles was assessed by comparing the pulse enhancement (PE) of 10 μM of a probe compound, carbamazepine (CBZ), in the presence and absence of a scavenger. Based on PE results, acetic acid/acetate appears to scavenge OH in bulk solution, and not interact with cavitation bubbles. Methanesulfonate acts as reaction promoter, increasing rather than inhibiting the degradation of CBZ. For formic acid, carbonic acid, terephthalic acid/terephthalate, benzenesulfonate, and iodide, the PE was significantly decreased compared to in the absence of the scavenger. These scavengers not only quench OH in bulk solution but also affect the cavity interface. The robustness of acetic acid/acetate as a bulk OH scavenger was validated for pH values between 3.5 and 8.9 and acetic acid/acetate concentrations from 0.5 to 0.1 M. 相似文献
7.
Ying-Nan Chen Huan-Huan Li Bin Yue Yuan-Yuan Liu Hai-Bin Chu Yong-Liang Zhao 《Journal of luminescence》2012,132(6):1414-1419
Using 2,3-pyrazine dicarboxylate (pzdc2?) as ligand, a series of new terbium complexes Tb2L2(HL)(NO3)10 H2O, Tb2Mg2L4(HL)(NO3)14 H2O, Tb2Ca2L4(HL)(NO3)14 H2O, Tb2Sr2L4(HL)(NO3)14 H2O, Tb2Ba2L4(HL)(NO3)14 H2O, Tb2Cd2L4(HL)(NO3)14 H2O, Tb2Co2L4(HL)(NO3)14 H2O, Tb2Ni2L4(HL)(NO3)14 H2O and Tb2Zn2L4(HL)(NO3)14 H2O (L=pzdc2-) have been synthesized. The complexes were characterized by elemental analysis, ICP-AES, molar conductivity measurement, TG-DSC analysis, IR spectroscopy and UV absorption spectroscopy. The luminescence spectra, luminescence lifetimes and emission quantum efficiencies of the complexes were measured. The results show that doping alkaline earth metal ions have significantly increased the luminescence intensities and quantum efficiencies of the complexes, and the sequence of the quantum efficiencies of the doped complexes is Ba2+>Ca2+>Mg2+>Sr2+. The enhancement of luminescence efficiencies may result from the decrease of the concentration quenching effect of Tb3+ ions, intramolecular energy transfer from the ligands coordinated with doped ions to Tb3+ ions and the lattice distortion of the complexes. The luminescence efficiencies of the Tb3+ ions are also enhanced by doping Cd2+ and Zn2+ ions. However, the complexes doped with Co2+ or Ni2+ ions exhibit luminescence quenching, which is caused by the energy consumed by these two ions in the form of d-d electron transitions. 相似文献
8.
The sonochemical reduction of MnO4− to MnO2 in aqueous solutions was investigated as a function of alcohol concentration under Ar. The rate of MnO4− reduction initially decreased with increasing alcohol concentration, and then increased when the alcohol concentration was increased further. The concentrations at which the reduction rates were minimum depended on the hydrophobic properties of the added alcohols under ultrasonic irradiation. At low concentrations, the alcohols acted as OH radical scavengers; at high concentrations, they acted as reductant precursors: Rab, formed by abstraction reactions of the alcohols with sonochemically formed OH radicals or H atoms, and Rpy, formed by alcohol pyrolysis under ultrasonic irradiation. The results suggest that the reactivity order of the sonochemically formed reducing species with MnO4− at pH 7–9 is the sum of H2O2 and H > Rpy > Rab. The peak wavelengths of MnO2 colloidal solutions formed at high 1-butanol concentrations shifted to shorter wavelengths, suggesting the formation of small particles at high 1-butanol concentrations. The rates of sonochemical reduction of MnO2 to Mn2+ in the presence of 1-butanol were slower than that in the absence of 1-butanol, because the sonochemical formation of H2O2 and H, which act as reductants, was suppressed by 1-butanol in aqueous solutions. 相似文献
9.
《Journal of Physics and Chemistry of Solids》2003,64(6):939-946
X-irradiation of single crystals of Tp–GeH3 (Tp: triptycene) led to the trapping of the radical Tp–GeH2. The angular variations of the resulting EPR spectra were recorded at 300 and 77 K. The drastic temperature dependence of the spectra was caused by both a strong anisotropy of the g-tensor and a rotation of the GeH2 moiety around the C–Ge bond. The determination of the EPR tensors as well as the analysis of this motion required to take the presence of disorder in the crystal into account. In accordance with DFT calculations, Tp–GeH2 is shown to be pyramidal and to adopt, in its lowest energy structure, a staggered conformation. Rotation around the C–GeH2 bond is blocked at 90 K and is almost free above 110 K. The experimental barrier, obtained after simulation of the EPR spectra as a function of the rotational correlation time, is equal to 1.3 kcal mol−1, which is slightly inferior to the barrier calculated by DFT (3.6 kcal mol−1). Calculations performed on Tp–CH3, Tp–GeH3 and Tp–GeH2 show that the rotation barrier ΔErot around the C–Ge bond drastically decreases by passing from the germane precursor to the germanyl radical and that ΔErot increases by passing from the germane to its carbon analogous. Structural parameters involved in these barrier differences are examined. 相似文献
10.
Sonocatalytic performance of pyrite nanoparticles was evaluated by the degradation of sulfasalazine (SSZ). Pyrite nanoparticles were produced via a high energy mechanical ball milling (MBM) in different processing time from 2 h to 6 h, in the constant milling speed of 320 rpm. X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR) analysis and Brunauer–Emmett–Teller (BET) confirmed the production of pyrite nanoparticles during 6 h of ball milling with the average size distribution of 20–80 nm. The effects of various operational parameters including pH value, catalyst amount (mg/L), SSZ concentration (mg/L), ultrasonic frequency (kHz) and reaction time on the SSZ removal efficiency were examined. The obtained results showed that the maximum removal efficiency of 97.00% was obtained at pH value of 4, catalyst dosage of 0.5 g/L, SSZ concentration of 10 mg/L and reaction time of 30 min. Experimental results demonstrated that the kinetic of the degradation process can be demonstrated using Langmuir–Hinshelwood (L-H) kinetic model. The effect of different inorganic ions such as Cl−, CO32− and SO42− was investigated on the L-H reaction rate (kr) and adsorption (Ks) constants. Results showed that the presence of the mentioned ions significantly influenced the L-H constants. The impact of ethanol as a OH radical scavenger and some enhancers including H2O2 and K2S2O8 was investigated on the SSZ removal efficiency. Accordingly, the presence of ethanol suppressed SSZ degradation due to the quenching of OH radicals and the addition of K2S2O8 and H2O2 increased the SSZ removal efficiency, due to the formation of SO4− and additional OH radicals, respectively. Under the identical conditions of operating parameters, pyrite nanoparticles maintained their catalytic activity during four consecutive runs. 相似文献
11.
In this study, synergistic degradation of antibiotic norfloxacin (NOR) was obtained in a novel sonochemical ultrasound/zero-valent iron/tetraphosphate system (US/ZVI/TPP). Compared to three common organic ligands (EDTA, EDDS, and DTPA), TPP could perform more excellently in activation of O2 to produce reactive oxidative species (ROS) and lead to efficient Fenton-like oxidative degradation of NOR in the sonochemical in situ chemical oxidation (ISCO) system. An optimized initial condition was obtained as 10 mg/L NOR, 0.3 mM TPP, 1 g/L ZVI and initial pH 7, and the US/ZVI/TPP system would effectively degrade NOR with relative low dosage of ZVI and ligand as well as broad pH work range 3–9. It was found that three ROS (OH, O2− and H2O2) instead of OH only would participate in the NOR degradation, while the in situ generation of H2O2 during the series of Fe-TPP reactions should be more critical. Fourteen organic intermediates and four inorganic products were detected during the NOR decomposition, suggesting that two main degradation pathways would occur under OH oxidation via cleavage of the piperazine ring and defluorination of the benzene ring, respectively. Finally, an integrated reaction mechanism in the US/ZVI/TPP system was proposed including solid-liquid interfacial iron corrosion as well as bulk homogenous oxygen activation and Fenton reactions, wherein US would play mechanically and chemically promotional roles. Besides, triple-repeated treatments suggested the relative long-term re-usage of ZVI particles and low effluent dissolved iron (<0.6 mg/L). 相似文献
12.
《Ultrasonics sonochemistry》2014,21(5):1787-1796
Application of Advanced Oxidation Processes (AOP) such as sono, photo and sonophoto catalysis in the purification of polluted water under ambient conditions involve the formation and participation of Reactive Oxygen Species (ROS) like OH, HO2, O2−, H2O2 etc. Among these, H2O2 is the most stable and is also a precursor for the reactive free radicals. Current investigations on the ZnO mediated sono, photo and sonophoto catalytic degradation of phenol pollutant in water reveal that H2O2 formed in situ cannot be quantitatively correlated with the degradation of the pollutant. The concentration of H2O2 formed does not increase corresponding to phenol degradation and reaches a plateau or varies in a wave-like fashion (oscillation) with well defined crests and troughs, indicating concurrent formation and decomposition. The concentration at which decomposition overtakes formation or formation overtakes decomposition is sensitive to the reaction conditions. Direct photolysis of H2O2 in the absence of catalyst or the presence of pre-equilibrated (with the adsorption of H2O2) catalyst in the absence of light does not lead to the oscillation. The phenomenon is more pronounced in sonocatalysis, the intensity of oscillation being in the order sonocatalysis > photocatalysis ⩾ sonophotocatalysis while the degradation of phenol follows the order sonophotocatalysis > photocatalysis > sonocatalysis > sonolysis > photolysis. In the case of sonocatalysis, the oscillation continues for some more time after discontinuing the US irradiation indicating that the reactive free radicals as well as the trapped electrons and holes which interact with H2O2 have longer life time (memory effect). 相似文献
13.
TiO2-biochar (TiO2-BC) nanocomposite was synthesized by sol-gel method. The characteristics of the prepared nanocomposite were examined using X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption analysis. The performance of synthesized TiO2-BC nanocomposite as efficient sonocatalyst was studied for the degradation of Reactive Blue 69 (RB69). Sonocatalytic degradation of RB69 in the presence of TiO2-BC nanocomposite could be explained by the mechanisms of hot spots and sonoluminescence. The optimized values for main operational parameters were determined as pH of 7, TiO2-BC dosage of 1.5 g/L, RB69 initial concentration of 20 mg/L and ultrasonic power of 300 W. Furthermore, the effect of OH, h+ and O2− scavengers on the RB69 degradation efficiency was studied. Gas chromatography-mass spectroscopy analysis was used to identify intermediate compounds formed during the RB69 degradation. The results of repeated applications of TiO2-BC in the sonocatalytic process verified its stability in long-term usage. 相似文献
14.
Central events of ultrasonic action are the bubbles of cavitation that can be considered as powered microreactors within which high-energy chemistry occurs. This work presents the results of a comprehensive numerical assessment of frequency and saturating gases effects on single bubble sonochemistry. Computer simulations of chemical reactions occurring inside a bubble oscillating in liquid water irradiated by an ultrasonic wave have been performed for a wide range of ultrasonic frequencies (213–1100 kHz) under different saturating gases (O2, air, N2 and H2). For O2 and H2 bubbles, reactions mechanism consisting in 25 reversible chemical reactions were proposed for studying the internal bubble-chemistry whereas 73 reversible reactions were taken into account for air and N2 bubbles. The numerical simulations have indicated that radicals such as OH, H, HO2 and O are created in the bubble during the strong collapse. In all cases, hydroxyl radical (OH) is the main oxidant created in the bubble. The production rate of the oxidants decreases as the driving ultrasonic frequency increases. The production rate of OH radical followed the order O2 > air > N2 > H2 and the order becomes more remarkable at higher ultrasonic frequencies. The effect of ultrasonic frequency on single bubble sonochemistry was attributed to its significant impact on the cavitation process whereas the effects of gases were attributed to the nature of the chemistry produced in the bubble at the strong collapse. It was concluded that, in addition to the gas solubility, the nature of the internal bubble chemistry is another parameter of a paramount importance that controls the overall sonochemical activity in aqueous solutions. 相似文献
15.
L. Villeneuve L. Alberti J.-P. Steghens J.-M. Lancelin J.-L. Mestas 《Ultrasonics sonochemistry》2009,16(3):339-344
Water sonolysis leads to the formation of hydroxyl radicals (OH). Various techniques are used to detect the OH production and thus to assess the level of ultrasound-mediated cavitation generated in vitro. In this study, we used terephthalic acid (TA) as an OH trap. This method is based on the fluorescent properties of hydroxyterephthalic acid (HTA) formed by the reaction of TA with OH and used as an indicator of the degree of inertial cavitation caused.The experimental system is comprised mainly of a focused piezoelectric ultrasound transmitter and a measurement cell containing 1X PBS/TA diluted solution. In the first part, we aimed to characterize the most appropriate experimental conditions (TA dosimeter solution, irradiation time) in order to optimize the resulting HTA fluorescence values. Then, we could determine that the HTA production increased with the level of the cavitation phenomenon caused by the acoustic power from which OH production may be estimated. 相似文献
16.
Fabrice Guittonneau Abdesselam Abdelouas Bernd Grambow Sandrine Huclier 《Ultrasonics sonochemistry》2010,17(2):391-398
Ultrasound treatment was used to study the decrease of the granulometry of graphite, due to the cavitation, which allows the erosion by separating grains. At a smaller scale, cavitation bubble implosion tears apart graphite sheets as shown by HRTEM, while HO and H radicals produced from water sonolysis, generate oxidative and reductive reactions on these sheet fragments. Such reactions form smaller species, e.g. dissolved organic matter. The methodology proposed is very sensitive to unambiguously identifying the in situ composition of organic compounds in water. The use of the atmospheric pressure chemical ionization (APCI) Fourier transform mass spectrometry (FTMS) technique minimizes the perturbation of the organic composition and does not require chemical treatment for analysis. The structural features observed in the narrow range (m/z < 300) were mainly aromatic compounds (phenol, benzene, toluene, xylene, benzenediazonium, etc.), C4–C6 alkenes and C2–C10 carboxylic acids. Synthesis of small compounds from graphite sonication has never been reported and will probably be helpful to understand the mechanisms involved in high energy radical reactions. 相似文献
17.
Persulfate-based oxidation of recalcitrant pollutants has been investigated as an alternative to OH radical based advanced oxidation processes due to distinct merits such as greater stability and non-selective persistent reactivity of oxidant species. The present study has attempted to highlight mechanistic features of persulfate-based decolorization of textile dye (Azorubine) using sono-hybrid techniques of activation. Three activation techniques, viz. sonolysis, Fe2+ ions and UVC light and combinations thereof, have been examined. UVC is revealed to be the most efficient decolorization technique. The mechanism of sonolysis (i.e. thermal activation of persulfate in the bubble-bulk interfacial region) is revealed to be almost independent of the mechanism of UVC. Fe2+ activation is revealed to have an adverse interaction with UVC due to scavenging of sulfate radicals by Fe2+ ions. The best hybrid activation technique for persulfate-based degradation and mineralization of Azorubine is UVC + ultrasound. Due to independent mechanisms, degradation and mineralization of the dye obtained with simultaneous application of UVC and ultrasound is nearly equal to the sum of degradation and mineralization obtained using individual techniques. 相似文献
18.
W. Piecek L. Jaroszewicz E. Miszczyk Z. Raszewski M. Mrukiewicz P. Kula K. Jasek P. Perkowski E. Nowinowski-Kruszelnicki J. Zieliński J. Kędzierski M. Olifierczuk U. Chodorow P. Morawiak R. Mazur K. Kowiorski P. Harmata J. Herman 《Opto-Electronics Review》2017,25(2):103-109
There exists a problem with an in situ diagnostics of contamination of ethyl alcohol in a human being exhaled air. When ethyl alcohol in a mouth blowing (in a gaseous state) exists, the characteristic CH stretch absorption bands in CH3 and CH2 functional groups in ethanol (CH3CH2OH) appear at a wavelength of λ = 3.42 μm. To investigate the presence of ethyl alcohol in exhaled human air, the light beam of λ = 3.42 μm is passing through an air sample. If one alternately measures the intensity of the investigated beam and the reference, a percentage of ethanol in the air sample can be estimated using a sensitive nondispersive infrared (NDIR) system with a stable operating flow mass detector. To eliminate a mechanical chopper and noise generating stepper motors, a photonic chopper as a liquid crystal shutter for λ = 3.42 μm has been designed. For this purpose, an innovative infrared nematic liquid crystal mixture was intentionally prepared. The working mixture was obtained by a selective removal of CH bonds and its exchange by heavier polar substituents, what ensures a lack of absorption band of CH bonds. The paper presents theory, concept and final experimental results of the infrared nematic liquid crystals mixture and the liquid crystal shutter for breathalyzer applications. 相似文献
19.
20.
《Ultrasonics sonochemistry》2014,21(1):428-435
Ciprofloxacin (CIPRO) and ibuprofen (IBU), a hydrophilic and a hydrophobic compound, respectively, were degraded by ultrasound at the frequencies of 20 and 620 kHz in aqueous solution containing matrix organic compounds. Compared to in its absence, in the presence of terephthalate (TA), a commonly used OH scavenger, CIPRO degradation was inhibited by a factor of 40–1500 depending on the frequency and initial concentration. However, the degradation rates of IBU were only reduced between 30% and 80% with TA present compared to in its absence. Similar to TA, the presence of Suwannee River Fulvic Acid (SRFA) inhibited CIPRO degradation to a greater extent than that of IBU but overall inhibition by SRFA was dramatically less than by TA. Although both TA and SRFA inhibited the degradation of CIPRO and IBU, the mechanisms of inhibition are different. TA reacts with OH in bulk solution and our evidence also indicates that it accumulates on or interacts with cavitation bubbles. On the other hand, SRFA stays in bulk solution, quenching OH and/or associating with the target compounds. 相似文献