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Degradation of tetracycline by medium pressure UV-activated peroxymonosulfate process: Influencing factors, degradation pathways, and toxicity evaluation
摘要： This study employed the medium pressure UV/peroxymonosulfate (MPUV/PMS), a new sulfate radical-based advanced oxidation process, to eliminate tetracycline (TTC) in water. At pH = 3.7, initial TTC concentration of 11.25 μM, PMS dosage of 0.2 mM and UV dose of 250 mJ cm-2, 82 % of TTC was degraded by MPUV/PMS. The second-order reaction rate constants of TTC with SO4?- and ?OH were found to be 1.4 × 1010 M-1 s-1 and 6.0 × 109 M-1 s-1, respectively. Radical quenching experiments indicated that ?OH played the major role in the degradation of TTC. Higher PMS dosage (0.1 mM~1.0 mM) and higher pH (3~11) could accelerate the TTC removal. Besides, the presence of Cl- (0.1 mM~5.0 mM) and CO32- (0.05 mM~0.5 mM) could also promote the reaction. Eight transformation products (TPs) were identified, and the potential degradation pathways mainly involved hydroxylation, demethylation and decarbonylation processes. The variation in the genotoxicity was investigated using the umu-test, and the results indicate that the genotoxicity of TTC after the MPUV/PMS treatment significantly increased during the initial stage. In addition, the ecotoxicity and mutagenicity of TTC and its TPs were predicted using quantitative structure-activity relationship (QSAR) analysis, and the results revealed that some TPs could have equivalent and even higher toxicity than TTC. MPUV/PMS showed better performance in TTC degradation in real waters than in Milli-Q water. MPUV/PMS is concluded to be an efficient method for removing TTC, but more attention should be paid to the changes of toxicity during this process.
关键词： Tetracycline,Toxicity,Hydroxyl radical,Sulfate radical,Transformation products
更新于2025-09-23 15:23:52
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Mass Spectrometric Imaging Reveals Photocatalytic Degradation Intermediates of Aromatic Organochlorines Resulting from Interfacial Photoelectron Transfer and Hydroxyl Radical Abstraction on Semiconductor Nanoparticles
摘要： Organochlorines are highly persistent and toxic contaminants that are widely distributed and accumulated in various aquatic or soil environments as well as food chains. Heterogeneous photocatalytic degradation of such pollutants by using semiconductor nanoparticles has been recognized as one of the effective purification ways. Understanding of degradation mechanisms and designing of highly efficient semiconductor nanoparticles require structural identification of various degradation intermediates that are difficult to achieve with current spectroscopic techniques. Herein a mass spectrometric approach was developed to tackle interfacial photoelectron transfer and hydroxyl radical abstraction on different semiconductor nanoparticles. Chlorobenzenes (including hexachlorobenzene and chlorothalonil) adsorbed on the surfaces of nanoparticles were found to instantly undergo dechlorination and ring dissociation through photoelectron capture dissociation and abstraction of a chlorine atom from aromatic C-Cl bond by hydroxyl radicals. Different intermediates have been unambiguously identified with experimental evidences provided by a Q-TOF mass spectrometer. It has been demonstrated that both electron density around atoms and steric effects of side chains contribute to the site selectivity for photoelectron capture and hydroxyl radical abstraction. But the energies needed for chemical bond cleavages and the stabilization of acquired charges play important roles in degradation efficiency. By using mass spectrometric imaging, photocatalytic differences of different semiconductor nanoparticles have been revealed.
关键词： Photoelectron Capture Dissociation,Interfacial Photoelectron Transfer,Chlorobenzenes,Mass Spectrometry,Hydroxyl Radical
更新于2025-09-23 15:23:52
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The efficiency and mechanism in a novel electro-Fenton process assisted by anodic photocatalysis on advanced treatment of coal gasification wastewater
摘要： A novel dual-chamber photo-electrochemical oxidation system with Fe@Fe2O3/CF cathode was constructed by combining cathodic electro-Fenton and anodic photocatalysis for advanced treatment of biologically pretreated coal gasification wastewater (CGW). In the electro-Fenton cathode chamber, maximal chemical oxygen demand (COD) removal efficiency of 84.2% was arrived within 120 min at current density 10 mA/cm2, initial pH 3 and air flow rate 0.4 L/min for its initial concentration of 200 mg/L. Correspondingly, the effluent concentration of COD, BOD5, TOC and total phenols were 31.5, 3.9, 8.4 and 13.8 mg/L respectively, satisfying the stringent wastewater discharge standard. Moreover, the H2O2 concentration change and wastewater acute toxicity were analyzed. Furthermore, a reasonable degradation mechanism was proposed based on the contribution of hydroxyl radicals (%OH), and thus degradation pathway of phenol as typical pollutant was also speculated. The integrated system is confirmed to be high-effective and stable, and thus it is a potentially promising alternative for treatment toxic refractory industrial wastewater.
关键词： COD removal,Hydroxyl radical,Electro-Fenton,Fe@Fe2O3/CF,Coal gasification wastewater
更新于2025-09-23 15:23:52
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Photocatalytic Degradation of Estriol Using Iron-Doped TiO2 under High and Low UV Irradiation
摘要： Iron-doped TiO2 nanoparticles (Fe-TiO2) were synthesized and photocatalitically investigated under high and low ?uence values of UV radiation. The Fe-TiO2 physical characterization was performed using X-ray Powder Diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Diffuse Re?ectance Spectroscopy (DRS), and X-ray Photoelectron Spectroscopy (XPS). The XPS evidenced that the ferric ion (Fe3+) was in the TiO2 lattice and unintentionally added co-dopants were also present because of the precursors of the synthetic method. The Fe3+ concentration played a key role in the photocatalytic generation of hydroxyl radicals (?OH) and estriol (E3) degradation. Fe-TiO2 accomplished E3 degradation, and it was found that the catalyst with 0.3 at.% content of Fe (0.3 Fe-TiO2) enhanced the photocatalytic activity under low UV irradiation compared with TiO2 without intentionally added Fe (zero-iron TiO2) and Aeroxide? TiO2 P25. Furthermore, the enhanced photocatalytic activity of 0.3 Fe-TiO2 under low UV irradiation may have applications when radiation intensity must be controlled, as in medical applications, or when strong UV absorbing species are present in water.
关键词： hydroxyl radical,estriol,iron-doped TiO2,photocatalytic activity,low UV irradiation
更新于2025-09-23 15:22:29
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Degradation of carbamazepine by vacuum-UV oxidation process: Kinetics modeling and energy efficiency
摘要： Vaccum-ultraviolet (VUV) is effective for elimination of organic contaminants in aqueous environment and degradation of carbamazepine (CBZ) by VUV irradiation was systematically investigated in this study. A dynamic kinetic model was developed to simulate the destruction of CBZ that is mainly initiated by hydroxyl radicals (HO?). The second-order rate constant of the reaction between CBZ and HO? was determined to be 1.4×109 M-1 s-1. Effect of initial CBZ concentration, VUV irradiation intensity and natural organic matter (NOM) were further investigated in several batch experiments. The predicted CBZ removal rates increased with the increasing VUV intensity, while decreased with the increasing initial CBZ and NOM concentrations. Based on the electrical energy per order (EE/O) calculation, the optimal VUV intensity was determined to be 7.5×10-8 Einstein s-1. Meanwhile, several intermediates/products were identified and their time-dependent evolution profiles were determined, and finally a plausible degradation pathway of CBZ was proposed. Ecotoxicity assessment indicated that the potential toxicity of CBZ and its oxidation products should be paid more attention in the VUV process.
关键词： Kinetic model,Degradation pathway,Energy efficiency,Hydroxyl radical
更新于2025-09-19 17:15:36
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Microwave discharge electrodeless mercury lamp (Hg-MDEL): an energetic, mechanistic and kinetic approach to the degradation of Prozac?
摘要： A photochemical reactor composed of an Hg-MDEL was applied in photodegradation studies of fluoxetine (Prozac?). The reactor exhibited to be an efficient hydroxyl radical generation system, since constant of formation of OH? formation is optimized through the adjustment of this parameter. An increase in the initial hydroxycoumarin (4HC) and 7-hydroxycoumarin (7HC) solutions resulted in the kinetics constant value, the mean kinetic constant was k = 10.64 ± 1.25 min -1 and R 2 = 0.943 ± 0.131. The Prozac? photodegradation studies showed that the application of the pseudo-first-order applied for degradation of Prozac?, the study of variation of the microwave power allowed a concentration of Prozac from 33 to 134 μmol L-1 resulted in a 21% decrease in the kinetic significant increase in the rate of degradation of the Prozac?, indicating that the hydroxyl radical the OH? quantification studies conducted with coumarin (COU), 4- kOH = 3.14 ± 0.18 min-1. When the Hg-MDEL reactor was 100% for its highest concentration (134 μmol L-1) at the time of 0.75 min. As for the solution of Prozac? 101 μmol L-1, the energy consumption was 6 kWh g-1, achieving a removal of 99%. formation of hydroxyl radicals, a high degradation rate of organic compounds (Prozac?, COU influence exerted by the transformation products. In general, the total removal of Prozac? was kinetics should be limited to the time of up to 0.50 min for the respective system, due to the Finally, the photochemical system presented in this work demonstrates a high efficiency in the and 7HC) and low energy consumption.
关键词： hydroxyl radical,direct photolysis,fluoxetine,pharmaceuticals,and kinetics,degradation mechanism
更新于2025-09-19 17:15:36
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Photocatalytic degradation of acetaminophen over Ag, Au and Pt loaded TiO2 using solar light
摘要： The sustainability and feasibility of using solar irradiation instead of UV light in photocatalysis is a promising approach for water remediation. In this study, photocatalytic degradation (PCD) of a widely used analgesic and antipyretic drug, acetaminophen (AP), with noble metal loaded TiO2 photocatalysts (Ag/TiO2, Au/TiO2 and Pt/TiO2) was investigated in aqueous suspension using solar light. The deposition of noble metals (Ag, Au and Pt) onto the TiO2 surface enhanced the PCD of AP under different operating conditions including pH, surfactants and drug excipients. However, lower degradation rate constants of AP were obtained under simulated and direct solar light as compared to UV light. The degradation mechanism of AP under UV as well as simulated solar light was found to follow similar, though not identical, reaction pathways leading to hydroxylated intermediates (e.g. 4-acetamidoresorcinol (4-AR), 4-acetamidocatechol (4-AC) and hydroquinone (HQ)) through competitive routes. The PCD of AP followed a pseudo first order kinetics according to Langmiur-Hinshelwood model. Noble metal (Ag, Au and Pt) loaded TiO2 photocatalysts can be used effectively to degrade AP in water under both solar and UV light.
关键词： Solar light,Hydroxyl radical,Noble metal,Acetaminophen,TiO2
更新于2025-09-19 17:15:36
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Simultaneous measurement of CO and OH in flames using a single broadband, femtosecond laser pulse
摘要： In this short communication, we report simultaneous measurement of CO and OH in flames using a single femtosecond (fs)-duration laser source. Two-photon excitation of CO A 1 (cid:2) ←← X 1 ?+ (3,0), (4,0) and (5,0) bands and single-photon excitation of OH A 2 ?+ ← X 2 (cid:2) (1,0) band are achieved simultaneously using one fs-duration laser pulse near 283 nm. Subsequently, crosstalk-free, laser-induced fluorescence (LIF) emissions are detected from the v’ = 3, 4 and 5 upper vibrational levels of CO in the 200–230 nm region, and (1,1) and (0,0) bands of OH near the 310-nm region. A detailed spectroscopic investigation of CO in a gas cell is followed by simultaneous detection of CO and OH in C 2 H 4 /air flames. The measured CO and OH profiles as a function of flame equivalence ratio agree well with equilibrium calculations. The present study extends the applicability of broadband fs-LIF imaging of OH in flames, and reveal an alternate method to obtain heat release rate in turbulent flames via simultaneous OH and CO measurements.
关键词： Femtosecond diagnostics,Carbon monoxide,Laser-induced fluorescence,Hydroxyl radical
更新于2025-09-19 17:13:59
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Treatment of Trichloroethylene with Photocatalyst-Coated Optical Fiber
摘要： In this present study, we investigated the effect of photocatalyzation on the degradation of trichloroethylene (TCE) in the aqueous phase by a photocatalyst-coated plastic optical fiber (POF). Two light-emitting diodes (LEDs) with low light intensity were used as the light source and TiO2 and ZnO were used as photocatalysts, which were characterized by scanning electron microscope (SEM) and UV-Vis diffuse reflectance spectroscopy (DRS). The para-chlorobenzoic acid (pCBA) was used as the hydroxyl radical probe for kinetic study and for the calculation of hydroxyl radical conversion rate (ROH,UV ). Experimental results show that POF coated with TiO2 exhibited higher degradation efficiency of TCE in basic solution, but POF coated with ZnO performed better in acidic solution. The increase of coating times resulted in the decrease in degradation efficiency of TCE due to increased thickness of the photocatalyst layer. The enhancement of light intensity contributed to the improvement of photocatalytic treatment efficiency. The ROH,UV for TiO2 and ZnO coated POF increased from 2 × 103 to 8 × 103 M s cm2 mJ?1 and from 8 × 102 to 2 × 103 M s cm2 mJ?1, respectively, as the pH increased from 4 to 10.
关键词： trichloroethylene (TCE),optical fiber,photocatalysis,groundwater,hydroxyl radical
更新于2025-09-12 10:27:22
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Protective characterization of low dose sodium nitrite on yak meat myoglobin in a hydroxy radical oxidation environment: Fourier Transform Infrared spectroscopy and laser Micro-Raman spectroscopy
摘要： The effect of NaNO2 in hydroxyl radical-mediated oxidative damage of yak meat myoglobin was investigated. Laser micro-Raman spectroscopy and Fourier Transform Infrared spectroscopy were used to assess protein (carbonyls, total sulfhydryl and Disulfide bonds) oxidation, atomic (or molecular) interactions and secondary structural changes. The addition of NaNO2 during the oxidation of myoglobin significantly reduced the content of carbonyl and disulfide bonds and protected the sulfhydryl groups from hydroxyl radical oxidation (P < 0.05). There was no significant difference in the secondary structure of myoglobin between the control group and the SN treatment group(P > 0.05). At the same time, NaNO2 had an inhibitory effect on the expansion of the hemoglobin center size and the transition of Fe from a low spin state to a high spin state caused by radical-oxidized. These findings suggest that NaNO2 has potential for treatment effects in a hydroxyl radical-oxidized myoglobin.
关键词： Secondary structure,Hydroxyl radical,Raman spectroscopy,NaNO2,Myoglobin
更新于2025-09-11 14:15:04