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Study on heterogeneous photocatalytic ozonation degradation of ciprofloxacin by TiO2/carbon dots: Kinetic, mechanism and pathway investigation
摘要： In this study, the objective was mainly focusing on the mechanism investigation of ciprofloxacin (CIP) degradation by photocatalytic ozonation process which carried out by ozone and TiO2 with a low content of carbon-dots (CDs) under simulated sunlight irradiation. The physicochemical properties of the prepared photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM) X-ray photoelectron spectroscopy (XPS) and zeta potential. Comprehensive investigation has proven the process to be efficient in the removal of CIP with high yield of reactive species (?OH, O2 ?—, h+, etc.). Kinetic model on pH investigation found out a repulsive force between the photocatalysts and CIP intensified with the increasing pH, so did the production rate of hydroxyl radicals (?OH), while eventually reached a balance and achieved a maximum degradation rate. The results indicated that the enhancement mechanism was triggered by the photoexcited electron accumulated on CDs and transferred by ozone, resulting in the continuous generation of h+, O3 ? — and O2 ? —. Possible photocatalytic ozonation degradation pathways of CIP were proposed according to the identifications of intermediates using high-resolution accurate-mass spectrometry (HRAM) LC-MS/MS.
关键词： ciprofloxacin,reactive species,carbon-dots,photocatalytic ozonation,transformation pathway
更新于2025-11-14 15:15:56
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Kinetics and modeling of artificial sweeteners degradation in wastewater by the UV/persulfate process
摘要： The frequent detection of artificial sweeteners (ASs) in wastewater and surface water gives rise to concerns about their removal, Acesulfame (ACE) and sucralose (SUC) are two ASs that are difficult to remove. The ultraviolet/persulfate (UV/PS) advanced oxidation technology (AOT) is being considered as an effective process for the degradation of micropollutants in wastewater. However, the study of the degradation of ASs in real wastewater by the UV/PS is minimal. This study investigated the kinetics and modeling of ACE and SUC degradation in wastewater by the UV/PS process. Both ACE and SUC could be degraded effectively using this process. The degradation of ACE was mainly attributed to UV photolysis (51%), HO· (26%) and SO4·- (16%), while that of SUC was mainly attributed to HO· (68%) and SO4·- (27%). The second-order rate constants of ASs with SO4·- were significantly lower than that with HO·. Three major transformation products (TPs) of ACE and four major TPs of SUC were identified. Additionally, the effects and mechanisms of the water matrices, such as HCO3-, Cl-, NO3- and natural organic matter (NOM), on ASs degradation were investigated through response surface methodology (RSM). NOM and Cl- significantly inhibited the degradation of ACE in the UV/PS system, whereas NOM and HCO3- played a main inhibition role on the degradation of SUC. A water matrices parameter model for predicting ASs degradation in real wastewater was established by RSM for the first time, and the removal of ACE and SUC was well predicted by the model.
关键词： reactive species,UV/persulfate,real wastewater,predicting model based on water matrices,artificial sweeteners
更新于2025-09-11 14:15:04
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Ciprofloxacin degradation in UV/chlorine advanced oxidation process: Influencing factors, mechanisms and degradation pathways
摘要： Ciprofloxacin (CIP) is a widely used third generation fluoroquinolone antibiotics, and has been often detected in wastewater treatment plants. Finding an effective way to remove them from wastewater is of great concern. Ultraviolet (UV)/chlorine advanced oxidation process (AOP) has many advantages in micropollutant removal. In this study, CIP degradation in UV/chlorine process was investigated. Only 41.2% of CIP was degraded by UV photolysis and 30.5% by dark chlorination in 30 min, while 98.5% of CIP was degraded by UV/chlorine process in 9 min. HCO3- had markedly inhibition, NO3- and SO42- had slight inhibition, and Cl- had a marginal inhibition on the CIP degradation in UV/chlorine system. The degradation of CIP in UV/chlorine process was mainly attributed to the attack of reactive species. The relative contributions of hydrated electrons (eaq-), hydroxyl radicals (HO.), chlorine atoms (Cl.), and UV photolysis were investigated. Under neutral condition in aqueous solution, CIP degradation had highest pseudo first-order reaction rate constants, in which eaq- followed by Cl., HO., and UV photolysis. The intermediates and byproducts were identified and the degradation pathway was proposed. The total organic chlorine (TOCl) and biotoxicity were further assessed. CIP and natural organic matters (NOMs) were removed efficiently in real water. UV/chlorine showed the potential for the wastewater treatment containing CIP.
关键词： advance oxidation process,UV/chlorine process,UV photolysis,reactive species,wastewater,Ciprofloxacin
更新于2025-09-10 09:29:36
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Reactive Species Detection in Biology || UV–Vis Absorption and Chemiluminescence Techniques
摘要： Spectrophotometric techniques involving ultraviolet and colorimetric detection offer a convenient way of detecting reactive species (RS) formation due to the prevalence of UV-Vis spectrophotometer in research laboratories. Conventional spectrophotometric measurement of RS exploits their unique chemical reactivity with a small organic molecule and/or enzyme that has specificity to these RS where formation (or disappearance) of absorption peak/s at a particular wavelength is observed at the UV to the visible region of the electromagnetic spectrum. Direct detection of O2 from xanthine oxidase in the past involves rapid-freeze technique using electron paramagnetic resonance (EPR) spectroscopy. At the same time, spectrophotometric detection of O2 generated from xanthine oxidase/xanthine system was also employed for the investigation of the enzymatic property of superoxide dismutase (SOD) where the O2 levels were measured through reduction of ferricytochrome c, tetranitromethane, or oxidation of epinephrine to adenochrome. Several approaches have been developed since then to improve sensitivity with the use of submicromolar probe concentration thus allowing minimal interferences of the probe on the biological process being investigated. Specificity has also been improved to increase the reaction rate of probes to certain RS through synthesis of new and innovative analogues that exploit the unique chemistry between the probe and RS. Chromophore stability was also achieved through improved molecular design, optimized experimental conditions, or addition of supramolecular reagents since chromophores impart inherent thermodynamic stability as a function of its chemical structure, solvent polarity, pH, temperature, or due to presence of oxido-reductants or other reactive substances. Improved sample preparation and high-throughput analysis were also developed in order to maximize efficiency in the measurement markers of oxidative stress and determination of antioxidant capacity (AOC) of known molecules, food, biological fluid, or tissue. Therefore, spectrophotometric techniques for RS measurement have found broad application in the fields of biomedical research, clinical chemistry, plant biology, food chemistry, environmental chemistry, radiation chemistry, pharmaceuticals, toxicology, or material science to name a few, or just simply for the investigation of RS production in simple chemical systems. However, unlike the fluorescence probes, spectrophotometric as well as most applications of chemiluminescence probes do not provide spectrospatial image of the RS localization in cells, hence, one cannot deduce the site of radical production unless multiple probes and/or inhibitors are used with varying compartmentalization property (i.e., extracellular or intracellular). For example, in the investigation of radical production in cellular NADPH oxidase, several methods had been suggested such as measurement of O2 consumption, use of SOD-ferricytochrome c and horseradish peroxidase (HRP)/inhibitable probe such as Amplex Red for extracellular O2 and H2O2, respectively, and the HPLC analysis of the 2-OH-E marker for the quantification of intracellular O2.
关键词： Clinical Chemistry,Oxidative Stress,Spectrophotometric Techniques,Environmental Chemistry,Reactive Species,Antioxidant Capacity,Biomedical Research,Chemiluminescence,Superoxide Dismutase,UV-Vis Absorption
更新于2025-09-04 15:30:14
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Global model of an atmospheric-pressure capacitive discharge in helium with air impurities from 100 to 10000 ppm
摘要： Helium is a common working gas for cold atmospheric plasmas (CAPs) and this is often mixed with other gases, such as oxygen and nitrogen, to increase its reactivity. Air is often found in these plasmas and it can be either introduced deliberately as a precursor or entrapped in systems that operate in open atmosphere. In either case, the presence of small traces of air can cause a profound change on the composition of the plasma and consequently its application efficacy. In this paper, a global model for He+Air CAPs is developed, in which 59 species and 866 volume reactions are incorporated, and a new boundary condition is used for the mass transport at the interface between the plasma and its surrounding air gas. The densities of reactive species and the power dissipation characteristics are obtained as a function of air concentrations spanning from 100 to 10000 ppm. As the air concentration increases, the dominant cation changes from O2+ to NO+ and then to NO2+, the dominant anion changes from O2- to NO2- and then to NO3-, the dominant ground state reactive oxygen species changes from O to O3, and the dominant ground state reactive nitrogen species changes from NO to HNO2. O2(a) is the most abundant metastable species and its density is orders of magnitude larger than other metastable species for all air concentrations considered in the study. Ion Joule heating is found important due to the electronegative nature of the plasma, which leads to the fast decrease of electron density when the air concentration is larger than 1000 ppm. The generation and loss pathways of important biologically relevant reactive species such as O, O2-, O3, OH, H2O2, NO, HNO2, HNO3 are discussed and differences with the pathways observed in He+O2, He+H2O, Ar+Air and pure air plasmas are highlighted. Based on the simulation results, a simplified chemistry set with 47 species and 109 volume reactions is proposed. This simplified model greatly reduces the computational load while maintaining the accuracy of the simulation results within a factor of 2. The simplified chemistry model is computationally much less intensive, facilitating its integration into multidimensional fluid models for the study of the spatio-temporal evolution of He+Air CAPs.
关键词： helium,simplified chemistry model,reactive species,global model,cold atmospheric plasmas,power dissipation,air impurities
更新于2025-09-04 15:30:14