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Effect of the preparation method and metal content on the synthesis of metal modified titanium oxide used for the removal of salicylic acid under UV light
摘要： Titanium dioxide modified with Ag and Fe was synthesized using two preparation methods, characterized and applied to the photocatalytic degradation of salicylic acid in aqueous solution. The modified TiO2 samples were prepared by the sol-gel and wet impregnation methods starting from titanium(IV) isopropoxide and using AgNO3 and Fe(NO3)3·9H2O as precursors of the modifiers, with their content varying between 0 and 5 wt.%. Catalysts characterization was based on powder X-ray diffraction (PXRD), nitrogen physisorption at 77 K, temperature programmed reduction (H2-TPR), chemisorption of NH3 at 343 K and X-ray photoelectron spectroscopy (XPS). The photocatalytic degradation of salicylic acid by modified TiO2 was investigated under ultraviolet irradiation at 298 K considering various concentrations of the catalyst, between 100 and 1000 mgcatalyst/dm3, and of the organic molecule, between 0 and 15 mg/dm3. The catalysts most active in the degradation of salicylic acid were those having the highest Fe content.
关键词： salicylic acid removal,photocatalysis,sol-gel method,Doped titanium oxide,wet impregnation method
更新于2025-09-09 09:28:46
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Salicylic acid complexed with TiO2 for visible light-driven selective oxidation of amines into imines with air
摘要： The interplay of salicylic acid (SA) and reactive oxygen species (ROS) can modulate biotic and abiotic stress of plants, essential biological aerobic oxidation processes. Meanwhile, ROS plays a critical role in TiO2 photocatalytic system for the degradation of organic species. Herein, we developed a system consisted of SA and TiO2 aiming at the selective oxidation of organic molecules by ROS. Interestingly, SA complexed with TiO2 leads to ligand-to-metal charge transfer (LMCT) under visible light irradiation. The charge transfer from ligand (chemically adsorbed SA) to metal (conduction band of TiO2) activates O2 to ROS, superoxide (O2?). The positive charge located at ligand SA is connected with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) catalysis for direct two-electron oxidation of amines and later regenerated by O2. SA and its derivatives were screened as ligands of TiO2 for the selective aerobic oxidation of amines into imines under blue light-emitting diode (LED) irradiation in which 5-CH3O-SA (5-methoxysalicylic acid, 0.8 mol%) complexed with anatase TiO2 and coupled with TEMPO (5 mol%) confers significantly better results than the others. By this visible light LMCT route, both primary amines and secondary amines can be selectively oxidized into corresponding imines with atmosphere O2 as the terminal oxidant. Importantly, the desired product of N-benzylidenebenzylamine can be isolated in 92% yield.
关键词： Salicylic acid,Titanium dioxide,Amines,Photocatalysis,Surface complex
更新于2025-09-04 15:30:14
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Selective recognition of salicylic acid employing new fluorescent imprinted membrane functionalized with poly(amidoamine) (PAMAM)-encapsulated Eu(TTA)3phen
摘要： Selective fluorescent molecularly imprinted membrane (FMIM) for salicylic acid (SA) was successfully prepared by phase inversion technique with SA as template molecule, chitosan (CHI) as functional polymer, and Eu(TTA)3phen/PAMAM composed of Eu(TTA)3phen and the dendrimer (PAMAM) as the fluorophore, which was characterized by SEM, AFM, and XPS techniques. The introduction of the hydrophilic Eu(TTA)3phen/PAMAM into FMIM was able to improve the flux and the adsorption capacity of SA with good fluorescent stability. Among the FMIM, the FMIM2 prepared with 2.0% Eu(TTA)3phen/PAMAM in the cast membrane fluid was the optimal fluorescent imprinted membrane for selective detection of SA, which displayed a relatively wider linear range and lower limit of detection (LOD) (24 mg L-1). The imprinted FMIM2 could selectively detect the SA from complicated samples without obvious interference from analogues compared to the non-imprinted FNIM2. Moreover, the FMIM had promising recycling performance. It can be potentially used as an alternative imprinted membrane for selective detection and separation of trace SA in water.
关键词： Salicylic acid,Selective detection and separation,Europium,Dendrimer,Fluorescent molecularly imprinted membrane
更新于2025-09-04 15:30:14
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Kinetic spectrophotometric method for real-time monitoring of ultraviolet photoreactions: A mini-photoreactor
摘要： Photoreactors in research laboratories generally consist of UV-C or UV-A mercury lamps and vessels of volume ranging up to about 1.0 L of solutions (suspensions, solvents, reactants and catalysts). This photoreactor’s design implies in large amounts of chemicals - cost problems, considerable amount of co-generated waste - environmental issues, safety problems and the need of large laboratory space. Currently, there is an effort by the scientific community to apply the principles of “green chemistry”, tending to miniaturize reactors and formats [1-8] and use modern sources of radiation such as light-emitting diodes (UV-LEDs), which are much more environmentally friendly than mercury lamps [9-13]. Another disadvantage of classical photochemical reactors is the withdrawal of aliquots at several times intervals. This procedure modifies the total volume of solutions and, consequently, the total number of absorbed photons per chromophore. Besides that, this methodology is time and labor consuming, and sometimes it is unsafe. In this way, a low amount of experimental points can limit the full kinetic description and lead to misinterpretations in kinetic parameters such as reaction order and rate constants. Accurate determinations are also limited by temperature control, which is not commonly effective in classical photoreactors. Here in it is proposed an interesting mini-photoreactor constituted by one UV-LED and a traditional quartz cuvette of 1.00 cm optical length that allows the reaction execution and, simultaneously, continuous monitoring via UV-Vis spectrophotometry (real-time kinetic analysis). In order to validate the use of this new mini-photoreactor we employed the photodegradation of methylene blue (MB) and salicylic acid (SA) in homogeneous and heterogeneous systems. For the proposition, it is necessary a specific spectrophotometer apparatus with a detection system that is not influenced by external light [14] and a Peltier system for controlling temperature with a mini-bar magnetic agitation. Continuous kinetic monitoring was performed in a spectrophotometer with a xenon flash lamp and silicon diode detectors, which emit flashes only during data collection, which prevents extra photodegradation for very photosensitive samples. Another spectrophotometer’s type that can be employed is that one based on diode-array system, whose external light also does not affect the spectrophotometric measurement.
关键词： methylene blue,mini-photoreactor,UV-LED,real-time monitoring,salicylic acid,ZnO,photodegradation
更新于2025-09-04 15:30:14