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1.
A simple and reproducible UPLC‐MS/MS method for the determination of itraconazole (ITZ) and its photodegradation products formed during exposure to UV‐A radiation was developed. Chromatographic separations were carried out using an Acquity UPLC BEH C18 column (2.1 × 100 mm, 1.7 μm particle size). The column was maintained at 40°C, and eluted under gradient conditions from 100% to 50% of eluent A over 13 min, at a flow rate of 0.3 mL min?1. Eluent A was 0.1% (v/v) formic acid in water; eluent B was 0.1% (v/v) formic acid in acetonitrile. The linear regression analysis for the calibration curve showed a good linear correlation over the concentration range 0.0066–0.15 mg mL?1 with determination coefficient > 0.99. The activities of some photocatalysts during degradation process of ITZ were compared. It was found that indirect photodegradation of ITZ was more effective than direct photolysis. Under our experimental conditions the photodegradation rate constant depended on the applied catalysts with catalytic activity decreasing in the following pattern: FeCl3 > TiO2/FeCl3 > TiO2. The kinetic analysis of the photodegradation data revealed that the degradation of the ITZ follows first‐order kinetics. The photodegradation products of ITZ were identified, and their fragmentation pathways, derived from MS/MS data, were proposed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

2.
The degradation behaviours of five straight‐chain dicarboxylic acids (from ethanedioic acid to hexanedioic acid) were compared in aqueous TiO2‐based photocatalysis. When all other conditions were identical, the degradation rates were found to fluctuate regularly with the parity of the number of carbon atoms. Dicarboxylic acids with an even number of carbon atoms (e‐DAs) always degraded more slowly than those acids with an odd number of carbon atoms (o‐DAs). This unusual fluctuation in the reactivity for the degradation of dicarboxylic acids by TiO2‐based photocatalysis is very closely related to the different pre‐coordination modes of the acids with the photocatalyst. Attenuated total reflection FTIR (ATR‐FTIR) of e‐DAs labelled with 13C showed that both carboxyl groups of the acid coordinate to TiO2 through bidentate chelating forms. In contrast, only one carboxyl group of the o‐DAs coordinated to TiO2 in a bidentate chelating manner, whereas the other formed a monodentate binding linkage. The bidentate chelating form with bilateral symmetric coordination did not favour degradation. Isotope‐labelling experiments were performed with 18O2 to observe the different ways in which incorporated oxygen entered the initial decarboxylated products of e‐ and o‐DAs. For the degradation of butanedioic acid, (45.9±0.5) % of the oxygen in the formed propanedioic acid came from H2O, whereas for pentanedioic acid, (97.4±0.2) % of the oxygen in the formed butanedioic acid came from H2O. Our results demonstrate that in TiO2‐based photocatalysis, the reactivity of active species, such as . OH/hvb+, is far from non‐selective and that the attacks of these active species on organic substrates are significantly affected by the coordination patterns of the substrates on the TiO2 surface.  相似文献   

3.
A series of Ag‐enhanced TiO2–x/C composites (Ag/TiO2–x/C composites) with metal‐organic frameworks (MOFs) as precursors were prepared, and their photocatalytic activities were evaluated by the UV‐light driven photodegradation behaviors of methyl blue (MB). The as‐obtained samples were characterized by several techniques such as SEM, XRD, N2‐adsorption, XPS, UV/Vis spectrophotometry and UV/Vis diffuse‐reflectance spectra. The best photocatalytic performance was achieved in Ag/TiO2–x/C composite pyrolyzed at 1000 °C (ATC‐P10) due to rapid capture of electrons caused by silver doping, higher density of TiO2–x lattice oxygen vacancies for better trapping of electrons, and high surface area due to reduction and evaporation of metallic Zn. No obvious deactivation was observed after 10 cycles of UV‐light degradation of MB under the same experimental conditions. This report reveals a new approach to prepare stable and highly efficient UV‐light‐driven photocatalysts for organic pollutants in water.  相似文献   

4.
In this paper, TiO2 loaded on activated carbon fibers (ACF) was prepared by a coating treatment, followed by calcination at different temperatures in air atmosphere. The photocatalyst developed was characterized by SEM, XRD, XPS and UV-Vis adsorption spectroscopy. It was observed from SEM images that TiO2 loaded on ACF was in the form of small clusters with nanometer size. As confirmed by XRD and XPS determinations, the crystalline pattern of immobilized TiO2 was still anatase-form after calcination, and the micrographic structure and surface properties of ACF have not been damaged by the deposition process and calcination at different temperatures. Photocatalytic degradation of methylene blue (MB) in aqueous .solution was investigated using TiOE/ACF as photocatalyst. The comparison of photolysis, absorption and photocatalysis was carded out. The results indicated that the photocatalysis process of combined photocatalyst showed much higher degradation rate than that of photolysis and absorption processes. In addition, the possibility of cyclic usage of the photocatalyst was also confirmed.  相似文献   

5.
A photodegradation study of Aflatoxin B1 (AFB1) in water solution was performed under UV irradiation at different AFB1 initial concentrations and UV irradiation intensities. The effect of UV intensity on the AFB1 photodegradation ratio is dominative, when compared with AFB1 initial concentration. The photodegradation of AFB1 was proved to follow first‐order reaction kinetics (R2 ≥ 0.99). Three photodegradation products, i.e. P1 (C17H14O7), P2 (C16H14O6) and P3 (C16H12O7), were identified on the basis of low mass error and high matching property by ultra‐performance liquid chromatography–quadrupole time‐of‐flight mass spectrometry (UPLC–Q‐TOF MS), and the degradation pathway was proposed. This study first reports the appearance of these photodegradation products and the proposed degradation pathway in aqueous media. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

6.
A magnetized nano‐photocatalyst based on TiO2/magnetic graphene was developed for efficient photodegradation of crystal violet (CV). Scanning electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy and elemental mapping were used to characterize the prepared magnetic nano‐photocatalyst. The photocatalytic activity of the synthesized magnetic nano‐photocatalyst was evaluated using the decomposition of CV as a model organic pollutant under UV light irradiation. The obtained results showed that TiO2/magnetic graphene exhibited much higher photocatalytic performance than bare TiO2. Incorporation of graphene enhanced the activity of the prepared magnetic nano‐photocatalyst. TiO2/magnetic graphene can be easily separated from an aqueous solution by applying an external magnetic field. Effects of pH, magnetized nano‐photocatalyst dosage, UV light irradiation time, H2O2 amount and initial concentration of dye on the photodegradation efficiency were evaluated and optimized. Efficient photodegradation (>98%) of the selected dye under optimized conditions using the synthesized nano‐photocatalyst under UV light irradiation was achieved in 25 min. The prepared magnetic nano‐photocatalyst can be used in a wide pH range (4–10) for degradation of CV. The effects of scavengers, namely methanol (OH? scavenger), p‐benzoquinone (O2?? scavenger) and disodium ethylenediaminetetraacetate (hole scavenger), on CV photodegradation were investigated.  相似文献   

7.
A novel electrode was prepared by forming TiO2 thin films using a commercially available TiO2 powder (Degussa P25) on graphite plates for water photoelectrocatalytic decontamination. In addition to, for the first time the photoelectrochemical degradation of 3,4‐dichlorophenol was investigated. The effects of applied potential, pH, and initial 3,4‐dichlorophenol concentration on the photoelectrocatalytic (PEC) degradation of 3,4‐dichlorophenol using ultraviolet (UV) illuminated TiO2/graphite (TiO2/C) thin film electrode was examined and discussed. Also, direct photolysis (DP), electrochemical oxidation (EC), photocatalytic (PC) and photoelectrocatalytic (PEC) degradation of 3,4‐dichlorophenol were compared. Results show that the best responses for PEC are obtained at applied potential 1.2 V versus reference electrode, pH 8.0 and initial 3,4‐dichlorophenol concentration 6.7 mg L?1.  相似文献   

8.
UV filters as emerging contaminants are of great concern and their wide detection in aquatic environments indicates their chemical stability and persistence. This review summarized the photolytic and photocatalytic degradation of UV filters in contaminated water. The findings indicated that limited research has been conducted on the photolysis and photocatalysis of UV filters. Photolysis of UV filters through UV irradiation in natural water was a slow process, which was accelerated by the presence of photosensitisers e.g. triplet state of chromaphoric dissolved organic matter (3CDOM*) and nutrients but reduced by salinity, dissolved organic matter (DOM) and divalent cations. UV Photocatalysis of 4-methylbenzylidene camphor and 2-phenylbenzimidazole-5-sulfonic acid was very effective with 100% removal within 30 min and 90 min using medicated TiO2/H2O2 and TiO2, respectively. The radiation source, type of catalyst and oxygen content were key factors. Future research should focus on improved understanding of photodegradation pathways and by-products of UV filters.  相似文献   

9.
The photodegradation (λ=365 nm) of the biomolecule vitamin B12, catalyzed by the photocatalyst TiO2 nanoparticles (NPs), has been investigated in aqueous suspension. The photodegradation process of vitamin B12 has been monitored by means of electronic absorption (Abs), Fourier‐transform infrared (FT‐IR), and resonance Raman (RR) spectroscopies, respectively. The results show that only under UV illumination in the presence of TiO2 is there effective degradation, and the photocatalytic degradation of vitamin B12 is strongly influenced by the amount of TiO2 NPs, the pH, and the initial concentration of vitamin B12. The photocatalytic reaction kinetics of vitamin B12 conforms to a Langmuir‐Hinshelwood isotherm model. Changes involving the three structural units of the carbon‐metal bond C–Co, the organic corrin macrocycle combined with the benzimidazole nucleotide, and the inorganic CN in the vitamin B12 molecule during the photocatalytic degradation are also discussed.  相似文献   

10.
Pharmaceuticals of different therapeutic classes are found in the environment. Captopril is used worldwide as an antihypertensive drug, and it has been found in the influent, effluent and secondary sludge of wastewater treatment plants. Advanced oxidation processes, such as direct photolysis (UV-C) and heterogeneous photocatalysis (TiO2/UV-C), are alternatives to enhance mineralisation of pharmaceuticals and their removal during water treatment. In this article, it was evaluated the degradation of captopril in aqueous solution induced by UV-C and TiO2/UV-C systems. The process focused on the identification and monitoring of the by-products formed under these conditions by applying direct-infusion electrospray ionisation high-resolution mass spectrometry in the negative ion mode (ESI(-)-HRMS) and high-performance liquid chromatography coupled to high-resolution mass spectrometry (HPLC/HRMS). To evaluate the by-products toxicity, acute ecotoxicity tests were performed with the crustacean Artemia salina, and the cytotoxicity was evaluated with (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using HepG2 cells. It was observed by ESI(-)-HRMS that after 120 min of light exposure, there was almost complete removal of captopril, with 93.5% removal efficiency during photolysis and 99.9% during photocatalysis. At these conditions, the rate of mineralisation, by total organic carbon (TOC), was only 2.92% for photolysis and 9.09% for photocatalysis, evidencing the formation of degradation by-products. Nine by-products of captopril photodegradation were identified, and their respective chemical structure elucidations were proposed. The treated samples were nontoxic to A. salina and HepG2 cells, indicating that both oxidative treatments (photocatalytic or photolytic processes) can be conveniently employed to remove captopril from aqueous media.  相似文献   

11.
The objective of this study was to highlight the potential application of the corona discharge at atmospheric pressure for the surface activation of polyester (PES) fabrics in order to improve the binding efficiency of colloidal TiO2 nanoparticles. The obtained nanocomposite textile materials provide desirable level of UV protection, self‐cleaning properties, and photodegradation activity. The measured UV protection factor (UPF) of fabrics corresponds to UPF rating of 50+, designating the maximum UV protection. Additionally, the total photodegradation of methylene blue in aqueous solution was achieved after 24 hr of UV illumination and this capability was preserved and even improved after four repeated cycles. The results showed that the corona treated PES fabrics loaded with TiO2 nanoparticles had considerably enhanced the overall efficiency compared to PES fabrics loaded only with TiO2 nanoparticles. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

12.
Carbon‐doped titania (C‐TiO2) nanoparticles were synthesized by the sol–gel method at different calcination temperatures (300–600°C) employing titanium tetraisopropoxide (TTIP) as the titanium source and polyoxyethylene sorbitan monooleate (Tween 80) as the carbon source. The physical properties of C‐TiO2 samples were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activities were checked through the photodegradation of phenolphthalein (PHP) under ultraviolet irradiation. The UV spectrum showed that the carbon doping extends the absorption range of TiO2 to the visible region. However, the photocatalytic activity is affected by the electron–hole recombination phenomenon, as revealed by the photoluminescence (PL) study. According to the PL spectra, carbon doping reduces the edge‐to‐edge electron–hole recombination. Nevertheless, the number of defect sites is greatly influenced by the calcination temperature of C‐TiO2. C‐TiO2 that was calcined at 400°C showed the highest photodegradation percentage of PHP, which was mainly attributed to the synergic effect of the low direct edge‐to‐edge electron–hole recombination, high content of defect sites, and retention of active electrons on the surface hydroxyl group.  相似文献   

13.
Hierarchical macro‐/mesoporous N‐doped TiO2/graphene oxide (N‐TiO2/GO) composites were prepared without using templates by the simple dropwise addition mixed solution of tetrabutyl titanate and ethanol containg graphene oxide (GO) to the ammonia solution, and then calcined at 350 °C. The as‐prepared samples were characterized by scanning electron microscopy (SEM), Brunauer‐Emmett‐Teller (BET) surface area, X‐ray diffraction (XRD), Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and UV‐Vis absorption spectroscopy. The photocatalytic activity was evaluated by the photocatalytic degradation of methyl orange in an aqueous solution under visible‐light irradiation. The results show that N‐TiO2/GO composites exhibited enhanced photocatalytic activity. GO content exhibited an obvious influence on photocatalytic performance, and the optimal GO addition content was 1 wt%. The enhanced photocatalytic activity could be attributed to the synergetic effects of three factors including the improved visible light absorption, the hierarchical macro‐mesoporous structure, and the efficient charge separation by GO.  相似文献   

14.
In this project, microwave (MW) irradiation, photolysis, and photo catalyst were used for degradation of 4-chloro-2-nitro phenol (4-C2NP) in aqueous environment. The influence of main operating parameters such as initial pH, initial concentration of 4C2NP, power dissipation and the dosage of TiO2 on the degradation efficiency has been investigated. The optimum conditions was obtained such as initial concentration of 4C2NP at 30 mg L?1, initial pH at 6, power dissipation at 16 W for UV irradiation, and the amount of TiO2 at 0.2 g L?1. The removal of 4C2NP and chemical oxygen demand (COD) after 100 min of reaction in the combined method (MW/UV/TiO2) was obtained as 80.5% and 47.3%, respectively. Almost all processes are followed from the pseudo first order kinetics and the degradation rate of 4C2NP obeyed the following order: UV/TiO2/MW > UV/TiO2 > MW/UV > UV>MW.  相似文献   

15.
An improvement in the photodegradation performance for dyes due to interaction between carbon and titania in a self‐assembled mesoporous C? TiO2 composite catalyst, even for the difficult degradation of azo dyes, is reported herein. The dye removal process involves adsorption of the dye from water by the mesoporous carbon–titania, followed by photodegradation on the separated dye‐loaded solid. Such adsorption–catalysis cycles can be carried out more than 80 times without discernible loss of photocatalytic activity or the anatase content of the composite. In each run, about 120 mg dye per g catalyst can be degraded. The mesoporous carbon–titania catalyst also exhibits a high capacity for converting methyl orange in aqueous solution under visible light. Characterization by XRD, TEM, and N2 sorption techniques has revealed that the self‐assembled composite catalyst has an ordered mesostructure, uniform mesopores (4.3 nm), a large pore volume (0.30 cm3 g?1), and a high surface area (348 m2 g?1). The pore walls are composed of amorphous carbon and anatase nanoparticles of size 4.2 nm, which are well dispersed and confined. X‐ray photoelectron spectroscopy (XPS), surface photovoltage spectroscopy (SPS), and UV/Vis absorption results indicate doping of carbon into the anatase lattice and a change in the bandgap of the semiconductor. The synergistic improvement in the composite catalyst can be attributed to the following features: (1) carbon doping of the anatase lattice modifies its bandgap and enhances its activity under visible light; (2) confinement within carbon pore walls prevents aggregation of tiny anatase nanoparticles, improving their activity and stability; (3) the mesopores provide a confined space for photocatalysis; and (4) the strong adsorption ability of porous carbon for organic substances ensures that large quantities can be processed and inhibits further diffusion of the adsorbed organic substances, thereby enhancing the mineralization on anatase.  相似文献   

16.
Atomic‐layer deposition (ALD) is a thin‐film growth technology that allows for conformal growth of thin films with atomic‐level control over their thickness. Although ALD is successful in the semiconductor manufacturing industry, its feasibility for nanoparticle coating has been less explored. Herein, the ALD coating of TiO2 layers on ZnO nanoparticles by employing a specialized rotary reactor is demonstrated. The photocatalytic activity and photostability of ZnO nanoparticles coated with TiO2 layers by ALD and chemical methods were examined by the photodegradation of Rhodamine B dye under UV irradiation. Even though the photocatalytic activity of the presynthesized ZnO nanoparticles is higher than that of commercial P25 TiO2 nanoparticles, their activity tends to decline due to severe photocorrosion. The chemically synthesized TiO2 coating layer on ZnO resulted in severely declined photoactivity despite the improved photostability. However, ultrathin and conformal ALD TiO2 coatings (≈0.75–1.5 nm) on ZnO improved its photostability without degradation of photocatalytic activity. Surprisingly, the photostability is comparable to that of pure TiO2, and the photocatalytic activity to that of pure ZnO.  相似文献   

17.
Present work mainly focuses on experimental investigation to improvement of hydrogen production by water photoelectrolysis. An experimental facility was designed and constructed for visible light photocatalysis. A series of N‐TiO2 photocatalysts impregnated with platinum on the surface of N‐TiO2 were prepared. Hydrogen production upon irradiating aqueous Pt/N‐TiO2 suspension with visible light was investigated. The shift in excitation wavelength of TiO2 was 380 nm improved the yield of hydrogen production by N‐TiO2 and Pt/N‐TiO2. We used a 400 W mercury arc lamp combined with a 400 nm cutoff filter eliminating all the wavelengths under 400 nm. Pt/N‐TiO2 material was characterized with TPR, reflective UV/Visible spectroscopy and TEM. The best hydrogen production rate obtained for this setup for N/Ti = 10, 0.05 wt% Pt/N‐TiO2, through water splitting was about 772 μmolh?1g?1.  相似文献   

18.
We have synthesized a nitrogen‐doped activated carbon (NAC) derived from oak using KOH and N2 thermal treatment at 400 °C as well as CuS nanoparticles. The NAC was decorated with the synthesized CuS to apply as a photocatalyst for degradation of norfloxacin (NOR). Before its application for photodegradation, the adsorbent/photocatalyst structural properties were investigated using X‐ray diffraction, X‐ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy. The photocatalytic degradation of NOR was successfully done under visible light using NAC–CuS. The results revealed that the investigated fluoroquinolone degraded very efficiently and pseudo‐first‐order kinetics was adopted for the photodegradation process. In addition, isothermal studies showed that the adsorption process in darkness followed the Langmuir model. The degradation characteristics of the NAC–CuS photocatalyst were studied for 120 min and 15 h under visible light for degradation of NOR, exhibiting a good efficiency for NOR removal. During 120 min of degradation, some intermediate degradation products that can be considered as secondary pollutants were produced. Then, to degrade these pollutants the radiation time was increased up to 15 h. The results displayed a perfect degradation of NOR and its secondary pollutants. The effective variables including pH, degradation time and photocatalyst dosage were optimized and studied in a multivariate method using Design Expert 7. Determination of photodegradation products was carried out using liquid chromatography–mass spectrometry. The results are of significance for estimating the environmental fate of NOR in aqueous media.  相似文献   

19.
Summary. The degradation of imazapyr, an imidazolinone herbicide, in aqueous solution has been investigated with TiO2 slurry as photocatalyst at 30°C under UV radiation. The depletion of imazapyr concentration in an aqueous suspension followed 1st order kinetic behavior. The influence of pH and the charge densities of imazapyr geometries were calculated at the semi-empirical AM1 level, and the effect of temperature was investigated. The addition of electron acceptors such as potassium persulfate and hydrogen peroxide showed that the rate constant doubled at least. At higher persulfate concentrations the herbicide degradation was more efficient in direct photolysis than TiO2-photocatalysis. The degradation rate constant increased by 38% upon variation of the temperature between 20.0 and 50.0°C and displayed non-Arrhenius behavior.  相似文献   

20.
The photodegradation of paliperidone in aqueous and methanol media under UVA and UVC irradiation was investigated. The identification and structural elucidation of its photodegradation products were performed by the use of the reversed‐phase liquid chromatography coupled with accurate mass hybrid Q‐TOF mass spectrometry and an atmospheric pressure chemical ionization source. Five degradation products were found and their masses were obtained with high accuracy (1.10–5.26 ppm) based on the TOF (MS) spectra. For the structural elucidation of unknown degradation products MS/MS spectra were also registered. However, for the identification of the main photodegradation product (3‐{2‐[4‐(6‐fluoro‐1,3‐benzoxazol‐2‐yl)piperidin‐1‐yl]ethyl}‐9‐hydroxy‐2‐methyl‐6,7,8,9‐tetrahydro‐4H‐pyrido[1,2‐a]pyrimidin‐4‐one) in‐source fragmentation connected with collision‐induced dissociation was used and MS3 spectra were finally performed. The photodegradation of paliperidone yields the first‐order kinetics in all tested conditions. The aqueous medium was in this case much less stable than the methanol solvent regardless of the irradiation source. Additionally, the toxicity of the analyzed photodegradation products was predicted by the use of ECOSAR software and comparable values of LC50 for the main degradants and the parent compound were obtained. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

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