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1.
Environ Sci Pollut Res Int ; 30(54): 116078-116090, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37906333

RESUMO

Carbamazepine is a widely used antiepileptic drug to control and treat a variety of disorders that is frequently detected in surface water, and in municipal and urban wastewater. This recalcitrant pollutant could be removed by alternative advanced oxidation technology such as heterogeneous photocatalysis. Ce-modified ZnO and Pd-modified TiO2 were synthesized by a microwave-assisted sol-gel method. According to the characterizations (Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy), a mixture of oxides was determined in both materials: CeO2/ZnO and PdO/TiO2. Photocatalytic degradation of carbamazepine in pure water under visible light (3 h) was assayed. The degradation percentage obtained with each catalyst was 80%, 53%, 20%, and 9% for ZnO, Ce-modified ZnO, TiO2, and Pd-modified TiO2, respectively. The leaching of Zn as a possible source of water contamination was tested, finding the lowest value for Ce-modified ZnO by adjusting the initial pH up to neutrality. Later, an environmentally relevant concentration of carbamazepine (228 µg L-1) was assayed, using local surface water (pH = 8.3). Despite the presence of other compounds in the real water matrix, after 5 h of photocatalysis, a 56% of degradation of the pharmaceutical and low leaching of Zn were achieved. The use of Ce-modified ZnO activated by visible light is a promising strategy for the abatement of pharmaceutical active compounds.


Assuntos
Água , Óxido de Zinco , Óxido de Zinco/química , Luz , Titânio/química , Carbamazepina/química , Preparações Farmacêuticas , Catálise
2.
Photochem Photobiol Sci ; 22(1): 47-58, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36112308

RESUMO

Pure (TiO2) and 0.1 nominal atomic percent of palladium-modified TiO2 (Pd-TiO2) films were synthesized via a sol-gel method and compared through their physicochemical properties and photocatalytic activity in the degradation of an emerging contaminant, 17-α-ethinylestradiol (EE2). The activity of the films was studied using a continuous flow, planar microreactor under simulated sunlight. Catalysts characterization included X-ray diffraction, UV-Visible diffuse reflectance and transmittance spectroscopy, atomic force microscopy, transmission electron microscopy, Raman spectroscopy, N2 physisorption analysis, and X-ray photoelectron spectroscopy. The modification of TiO2 with palladium confined the size of anatase phase crystallites, increased the specific surface area and improved radiation absorption. PdO domains on TiO2 were observed. In all the tested conditions, higher conversion of EE2 was achieved with the Pd-TiO2 film compared with the TiO2 film, presenting an 80% increase in the reaction rate. The performance of the catalytic films was also assessed by the calculation of two efficiency parameters: radiation absorption efficiency and quantum efficiency of reaction. The Pd-TiO2 film showed a notable enhancement of the absorption of the incident radiation and a more efficient utilization of the absorbed photons to degrade the target pollutant.


Assuntos
Absorção de Radiação , Paládio , Microscopia Eletrônica de Transmissão , Titânio/química , Catálise
3.
Environ Sci Pollut Res Int ; 28(19): 24112-24123, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33471310

RESUMO

V-doped TiO2 materials (0.01, 0.05, 0.10, and 1.00 nominal atomic %) were synthesized by the sol-gel method and characterized by X-ray diffraction, Raman spectroscopy, UV-visible diffuse reflectance spectroscopy, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and H2-temperature programmed reduction. Two vanadium precursors (vanadyl acetylacetonate and ammonium metavanadate) and three calcination temperatures (400, 500, and 600 °C, with and without air circulation) were assayed. The efficiency of the materials as photocatalysts was studied by the degradation of phenol with UV and visible lamps. The photocatalyst prepared from vanadium acetylacetonate, with a vanadium content of 0.01 nominal atomic %, calcination at 400 °C without air circulation (0.01VTi-400), showed the best performance, reaching 100% and 30% degradation of phenol (50 µM) by irradiation with UV lamps (3 h) and visible lamps (5 h), respectively. To evaluate the efficiency of this catalyst in the degradation of other structurally related compounds, two substituted phenols were selected: 4-chlorophenol and 4-nitrophenol. The 0.01VTi-400 photocatalyst showed to be applicable to the degradation of phenolic compounds when the substituent was an activating group or a weakly deactivating group (for electrophilic reactions). Additionally, the selectivity of 0.01VTi-400 for phenol degradation in the presence of Aldrich humic acid was tested: phenol degradation reached 68% (3 h, UV lamps). The performance of 0.01VTi-400 indicated that it is a promising material for further applications.


Assuntos
Poluentes Ambientais , Catálise , Fenol , Titânio , Difração de Raios X
4.
Environ Sci Pollut Res Int ; 24(7): 6013-6021, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26875823

RESUMO

The degradation of phenol was used as a model reaction to investigate the photocatalytic properties of cerium-doped (0.1 nominal atomic percent) TiO2 catalysts in the presence and in the absence of oxidants: persulfate (PS) or hydrogen peroxide (HP). Experiments were performed in batch reactors using either artificial light (ultraviolet or visible) or solar exposure during spring-summer seasons in La Plata City (34.90° S, 57.92° W, 15 MASL). The formation of hydroquinone, catechol, and p-benzoquinone was observed in all the experiments. Additionally, for the experiments with PS (with or without catalyst), evidence of the formation of dimers and trimers was found. Total degradation of phenol (250 µM) was achieved with doped material and 7 mM of PS (two doses) after 3 h of solar exposure (H SUV, T = 2.9 ± 0.6 105 J m-2).


Assuntos
Oxidantes/química , Fenóis , Fotólise , Luz Solar , Titânio/química , Cério , Modelos Químicos , Fenóis/análise , Fenóis/química
5.
J Colloid Interface Sci ; 251(1): 151-9, 2002 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-16290713

RESUMO

Molybdosilicic acid solutions acidified with HCl were impregnated on carbon and silica by the equilibrium adsorption technique. From the equilibrium adsorption isotherms performed at 20 degrees C, it was established that the heteropolyacid amount adsorbed on carbon is higher than that on silica. Differences in shape and initial slope of the isotherm were observed. The interaction of the molybdosilicate anion was higher with carbon surface groups than with silanol groups. The physicochemical characterization of the solids has shown that the molybdosilicic acid presents an undegraded Keggin structure in the supported samples up to 250 degrees C. The surface acidity, mainly related to heteropolyacid adsorbed amount, was higher for samples on carbon. However, the silica-supported acid showed a bulk acidity higher than that on carbon, due to its lower interaction degree.

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