Ozonation and ozone-enhanced photocatalysis for VOC removal from air streams: Process optimization, synergy and mechanism assessment

• Type: Article in International Scientific Journal
• Date: 2019

Authors

Batuira M. da Costa Filho (Author) Other; Gabriela V. Silva (Author) Other; Rui A. R. Boaventura (Author) Other; Madalena M. Dias (Author) FEUP; José Carlos B. Lopes (Author) FEUP; Vítor J. P. Vilar (Author) Other

Journal

Title: Science of the Total Environment

Vol. 687

Pages: 1357-1368

ISSN: 0048-9697

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 0 Citations

Scopus - 28 Citations

Associated Projects

LSRE-LCM - Laboratório de Processos de Separação e Reacção - Laboratório de Catálise e Materiais

Other information

Authenticus ID: P-00Q-RAY

DOI: 10.1016/j.scitotenv.2019.05.365

Abstract (EN): The present work evaluates ozone driven processes (O-3, O-3/UVC, O-3/TiO2/UVA) in the NETmix mili-photoreactor, as a cost-effective alternative for the removal of volatile organic compounds (VOCs) from air streams, using n-decane as a model pollutant. The network of channels and chambers of the mili-photoreactor was coated with a TiO2-P25 thin film, resulting in a catalyst coated surface per reactor volume of 990 m(2) m(-3). Ozone and n-decane streams were fed to alternate chambers of the mili-photoreactor, promoting a good contact between O-3/n-decane/catalyst. Initially, direct reaction between n-decane and ozone (ozonation) was assessed for different O-3/n-decane (O-3/dec) feed molar ratios and total feed flow rates. Under the best conditions, ozonation process achieved total n-decane conversion (below the limit of detection), yielding a reaction rate (r(dec)) of 6.8 mu mol min(-1) or 6.7 mmol m(reactor)(-3) s(-1). However, the low reactivity of ozone with the degradation by-products resulted in a quite poor mineralization (similar to 10%). For the O-3/UVC system, an increase on relative humidity from 7 to 40% slight improved the n-decane oxidation rate, mainly associated with the generation of HO center dot from the reaction of active oxygen radicals (O center dot) and water molecules. A strong synergistic effect was observed when coupling TiO2/UVA photocatalysis with ozonation (O-3/TiO2/UVA), enhancing substantially the mineralization of n-decane molecules up to 100% under O-3/dec feed molar ratio of 15, photonic flux of 2.67 +/- 0.03 J s(-1) and a residence time of 2.0 s. Different reaction intermediates were detected for O-3, TiO2/UVA and O-3/TiO2/UVA oxidative systems, indicating the participation of different oxidant species (O-3, HO center dot, O center dot, etc.).

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 12