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Open AccessArticle

Improved Photocatalyzed Degradation of Phenol, as a Model Pollutant, over Metal-Impregnated Nanosized TiO2

1
Laboratoire de Physico-Chimie des Matériaux et Nanomateriaux, Faculté des Sciences, Université Mohammed V, Avenue Ibn Battouta, Rabat BP 1014, Morocco
2
International Iberian Nanotechnology Laboratory, 4715-330 Braga, Portugal
3
Grupo React!, Departamento de Química, Facultade de Ciencias & CICA, Universidade da Coruña, E-15071 A Coruña, Spain
*
Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(5), 996; https://doi.org/10.3390/nano10050996
Received: 7 April 2020 / Revised: 10 May 2020 / Accepted: 18 May 2020 / Published: 22 May 2020
(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)
Photocatalyzed degradation of phenol in aqueous solution over surface impregnated TiO2 (M = Cu, Cr, V) under UV-Vis (366 nm) and UV (254 nm) irradiation is described. Nanosized photocatalyts were prepared from TiO2-P25 by wet impregnation, and characterized by X-ray diffraction, X-ray fluorescence, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy, Raman spectroscopy, and adsorption studies. No oxide phases of the metal dopants were found, although their presence in the TiO2-P25 lattice induces tensile strain in Cu-impregnated TiO2-P25, whereas compressive strain in Cr- and V-impregnated TiO2-P25. Experimental evidences support chemical and mechanical stability of the photocatalysts. Type IV N2 adsorption–desorption isotherms, with a small H3 loop near the maximum relative pressure were observed. Metal surface impregnated photocatalysts are mesoporous with a similar surface roughness, and a narrow pore distribution around ca. 25 Å. They were chemically stable, showing no metal lixiviation. Their photocatalytic activity was followed by UV-Vis spectroscopy and HPLC–UV. A first order kinetic model appropriately fitted the experimental data. The fastest phenol degradation was obtained with M (0.1%)/TiO2-P25, the reactivity order being Cu > V >> Cr > TiO2-P25 under 366 nm irradiation, while TiO2-P25 > Cu > V > Cr, when using 254 nm radiation. TOC removal under 366 nm irradiation for 300 min showed almost quantitative mineralization for all tested materials, while 254 nm irradiation for 60 min led to maximal TOC removal (ca. 30%). Photoproducts and intermediate photoproducts were identified by HPLC–MS, and appropriate reaction pathways are proposed. The energy efficiency of the process was analysed, showing UV lamps are superior to UVA lamps, and that the efficiency of the surface impregnated catalyst varies in the order Cu > V > Cr. View Full-Text
Keywords: phenol; photocatalysis; titania; surface impregnation; photodegradation; reaction mechanism; adsorption analysis; energy efficiency phenol; photocatalysis; titania; surface impregnation; photodegradation; reaction mechanism; adsorption analysis; energy efficiency
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MDPI and ACS Style

Belekbir, S.; El Azzouzi, M.; El Hamidi, A.; Rodríguez-Lorenzo, L.; Santaballa, J.A.; Canle, M. Improved Photocatalyzed Degradation of Phenol, as a Model Pollutant, over Metal-Impregnated Nanosized TiO2. Nanomaterials 2020, 10, 996.

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