UV and visible activation of Cr(III)-doped TiO2catalyst prepared by a microwave-assisted sol-gel method during MCPA degradation.
Photocatalytic degradation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in aqueous solution using Cr(III)-doped TiO2under UV and visible light was investigated. The semiconductor material was synthesized by a microwave-assisted sol-gel method with Cr(III) doping contents of 0.02, 0.04, and 0.06 wt%. The catalyst was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), nitrogen physisorption, UV-Vis diffuse reflectance spectroscopy (DRS), and atomic absorption spectroscopy (AAS). The photocatalytic activity for the photodegradation of MCPA was followed by reversed-phase high-performance liquid chromatography (HPLC) and total organic carbon (TOC) analysis. The intermediates formed during degradation were identified using gas chromatography-mass spectrometry (GC-MS). Chloride ion evolution was measured by ion chromatography. Characterization results showed that Cr(III)-doped TiO2materials possessed a small crystalline size, high surface area, and mesoporous structure. UV-Vis DRS showed enhanced absorption in the visible region as a function of the Cr(III) concentration. The Cr(III)-doped TiO2catalyst with 0.04 wt% of Cr(III) was more active than bare TiO2for the degradation of MCPA under both UV and visible light. The intermediates identified during MCPA degradation were 4-chloro-2-methylphenol (CMP), 2-(4-hydroxy-2-methylphenoxy) acetic acid (HMPA), and 2-hydroxybuta-1,3-diene-1,4-diyl-bis (oxy)dimethanol (HBDM); the formation of these intermediates depended on the radiation source.
Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, UANL, Cd. Universitaria, C.P. 66455, San Nicolás de los Garza, Nuevo León, Mexico.
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Mendiola-Alvarez
Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, UANL, Cd. Universitaria, C.P. 66455, San Nicolás de los Garza, Nuevo León, Mexico.
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Guzmán-Mar
Department of Chemistry, University of the Balearic Islands, 07122, Palma de Mallorca, Spain.
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Turnes-Palomino
Department of Chemistry, University of the Balearic Islands, 07122, Palma de Mallorca, Spain.
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Maya-Alejandro
Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, UANL, Cd. Universitaria, C.P. 66455, San Nicolás de los Garza, Nuevo León, Mexico.
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Hernández-Ramírez
Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, UANL, Cd. Universitaria, C.P. 66455, San Nicolás de los Garza, Nuevo León, Mexico. laura.hinojosary@uanl.edu.mx.
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Hinojosa-Reyes
D002384:Catalysis; D003408:Cresols; D008872:Microwaves; D014025:Titanium / Q000737:chemistry*
D003408:Cresols; C009495:titanium dioxide; C019292:4-chloro-2-cresol; D014025:Titanium
Cr(III)-doped TiO2; Heterogeneous photocatalysis; MCPA; Microwave-assisted sol–gel method