Search results for "Photodegradation"
showing 10 items of 153 documents
The Photocatalytic Activity of Novel, Substituted Porphyrin/TiO2-Based Composites
2010
Four novel porphyrins, 5-[3-(3-phenoxy)-propoxy]phenyl porphyrin, 5,15-di-[3-(3-phenoxy)-propoxy] phenyl porphyrin, 5,10,15-tri-[3-(3-phenoxy)-propoxy]phenyl porphyrin, 5,10,15,20-tetra-[3-(3-phenoxy)- propoxy]phenyl porphyrin, and their corresponding Cu(II) porphyrins, were synthesized and characterized spectroscopically. The photodegradation of 4-nitrophenol in aq. suspension was used to determine the photocatalytic activity of polycrystalline TiO2 samples which had been impregnated with the Cu(II) porphyrins, as sensitizers. The photocatalytic activity of the composite depends mainly on the amount of sensitizer on the TiO2 surface rather than the nature of the substituted porphyrins.
Toward the Understanding of the Photophysics and Photochemistry of 1-Nitronaphthalene under Solar Radiation: The First Theoretical Evidence of a Phot…
2015
1-Nitronaphthalene belongs to the class of nitrated polycyclic aromatic hydrocarbons, and constitutes an atmospheric pollutant commonly found in urban environments due to its production during incomplete combustions. On the basis of CASPT2//CASSCF quantum chemical calculations, the photophysics and photochemistry of the system under solar exposure have for the first time been studied. According to the characteristics of the incident radiation (either UVA or UVB, both present in the portion of the solar spectrum reaching the earth), a different excited state will be mainly populated. In both cases, the main decay path undertaken by the corresponding bright state leads to an efficient intersy…
Photocatalytic degradation of nitrophenols in aqueous titanium dioxide dispersion
1991
Abstract The results are reported of an investigation into the photodegradation of nitrophenol isomers carried out in aqueous titania (anatase) dispersions under various experimental conditions. We investigated the influence of various parameters on the photodegradation rate, such as the concentrations of the catalyst, dissolved oxygen and organic compound, and the presence of various anions in the dispersion. A plausible explanation is proposed for the influence of these parameters, both mechanistic and kinetic factors being accounted for. Gas chromatography and mass spectrometry were used as analytical methods in order to determine intermediate products. Spectroscopic methods (UV-vis and …
Theoretical prediction of the photoinduced chemiluminescence of pesticides
2007
Although it is relatively easy to find chemiluminescent (CL) molecules working on the field of direct liquid phase (especially employing strong oxidants), the molecules found as chemiluminescent are normally very weak CL compounds for developing suitable analytical CL-procedures. Therefore, it is mandatory to develop new strategies to enhance in a simple way the native chemiluminescence of such a compounds, and even to increase the number of compounds to be determined by direct chemiluminescence. Photoinduced chemiluminescence (Ph-CL) results in a simple and easily on-line accessible strategy to solve these disadvantages. In the present paper, molecular connectivity, a topological method wh…
The impact of TiO2 modifications on the effectiveness of photocatalytic processes [REVIEW]
2018
This paper outlines the recent studies on the application of photocatalysis using semiconductors, with modified titanium dioxide (TiO2) in the process of reducing chemical contamination of surface and ground waters. During the last forty years, an increasing interest in catalysts of this type is noticeable. Hence, a wide range of methods of TiO2 modifications have been proposed so far by using its various polymorphs, composites with metals and non-metals and polymer-coatings or impregnating it with dyes that effectively absorb sunlight.
Environmental Organic Photochemistry: Advances and Perspectives
2013
This review is a survey of recent advances in environment related aspects of organic photochemistry. Besides presenting gen- eral concepts, the manuscript is mainly focused on the photoreactivity of natural organic matter, and on the photochemistry of anthropo- genic substances under natural light irradiation.
Degradation of Lincomycin in aqueous medium: coupling of solar photocatalysis and membrane separation
2005
Abstract The photocatalytic oxidation of a common antibiotic, the lincomycin was carried out in aqueous suspensions of polycrystalline TiO 2 Degussa P25 irradiated by sunlight. In order to improve the performance of the lincomycin degradation a hybrid system consisting of a solar photoreactor with the photocatalyst in suspension coupled with a membrane module, used to confine both photocatalyst and pollutants in the reaction environment, was tested. A preliminary study was carried out in order to determine some kinetics parameters of the drug photodegradation. The influence of initial substrate concentration on the lincomycin photooxidation rate was investigated. The photooxidation rate fol…
Heterogeneous photocatalytic degradation of pharmaceuticals in water by using polycrystalline TiO2 and a nanofiltration membrane reactor
2006
Abstract A study of the photodegradation of different pharmaceuticals [furosemide, ranitidine (hydrochloride), ofloxacine, phenazone, naproxen, carbamazepine and clofibric acid] in aqueous medium at various pHs by using a batch photoreactor and a photocatalytic membrane reactor working in recirculation regime was carried out. Polycrystalline TiO 2 was used as the photocatalyst, and different membranes (NTR 7410, PAN GKSS HV3/T, N 30 F, NF PES 10) were tested. A different adsorption of the substrates onto the catalyst surface was observed owing to the hydrophilic/hydrophobic character of the catalyst, depending on the pH. The photodegradation of the seven molecules in the batch reactor was s…
TiO2-based photocatalysts impregnated with metallo-porphyrins employed for degradation of 4-nitrophenol in aqueous solutions: role of metal and macro…
2007
Photodegradation of organic compounds in water solutions by means of economically advantageous and environment-friendly processes is a topic of growing interest. In recent years a great attention has been devoted to TiO2-based photocatalysts for the oxidative degradation of various organic pollutants. In this context, we have prepared new photo-catalytic polycrystalline TiO2 systems impregnated with sensitizers, i.e., copper, iron or manganese porphyrins, and investigated their photoactivity for 4-nitrophenol oxidation compared with that of bare TiO2. A significant improvement of the photoreactivity was observed in the case of TiO2 impregnated with copper porphyrin, while only a slight bene…
Influence of accelerated ageing conditions on the process of polyolefines degradation
2003
The process of polymers weathering and the methods of polymers weathering and accelerated ageing investigations were characterized. Accelerated ageing tests of polyethylene and polypropylene samples have been done in laboratory conditions. The ageing time (up to 400 h) influence, at various levels of ageing factors: UV radiation intensity (80—190 W/m2), temperature (35—55 °C) and humidity (30—90%), on the changes of the structures of polymers investigated (shares of carbonyl and olefinic groups from FT-IR spectra — Fig. 1, 2, 4 and 5), on the changes of polymers molecular weights (Fig. 3 and 6, Table 1) and on the changes of mechanical properties during tension (Table 1) has been investigat…