UV and visible activation of Cr(III)-doped TiO2 catalyst prepared by a microwave-assisted sol–gel method during MCPA degradation

• Published in: Environmental science and pollution research international Vol. 24; no. 14; pp. 12673 - 12682
• Main Authors: Mendiola-Alvarez, S. Y., Guzmán-Mar, J. L., Turnes-Palomino, G., Maya-Alejandro, F., Hernández-Ramírez, A., Hinojosa-Reyes, L.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2017; Springer Nature B.V
• Subjects: Absorption spectroscopy; Acetic acid; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Atomic absorption analysis; Atomic absorption spectroscopy; Atomic beam spectroscopy; Atomic structure; Catalysts; Catalytic activity; Chloride ions; Chromatography; Chromium; Degradation; Diffuse reflectance spectroscopy; Diffusion; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental Photocatalysis and Photochemistry for a Sustainable World: A Big Challenge; Environmental science; Gas chromatography; High performance liquid chromatography; Intermediates; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Organic carbon; Photocatalysis; Photodegradation; Scanning electron microscopy; Sol-gel processes; Spectral analysis; Spectroscopy; Titanium dioxide; Total organic carbon; Ultraviolet radiation; Waste Water Technology; Water Management; Water Pollution Control; X ray powder diffraction; MCPA; Cr(III)-doped TiO; Heterogeneous photocatalysis; Microwave-assisted sol–gel method
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-016-8034-x

Photocatalytic degradation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in aqueous solution using Cr(III)-doped TiO 2 under 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 TiO 2 materials 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 TiO 2 catalyst with 0.04 wt% of Cr(III) was more active than bare TiO 2 for 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.