Photocatalytic degradation of VOCs on various commercial titanium dioxides: Impact of operating parameters on removal efficiency and by-products generation

• Published in: Building and environment Vol. 138; pp. 275 - 282
• Main Authors: Mamaghani, Alireza Haghighat, Haghighat, Fariborz, Lee, Chang-Seo
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.06.2018; Elsevier BV
• Subjects: Acetaldehyde; Acetone; Air purification; Aromatic compounds; By-products; Byproducts; Catalytic activity; Commercialization; Continuous flow; Efficiency; High-performance liquid chromatography; Hydroxyl groups; Identification methods; Indoor air quality; Indoor environments; Ketones; Light intensity; Liquid chromatography; Luminous intensity; Methyl ethyl ketone; Methyl ethyl ketone (MEK); Oxidation; Photocatalysis; Photocatalysts; Photocatalytic oxidation (PCO); Photodegradation; Photooxidation; Relative humidity; Surface area; Titanium; Titanium dioxide; Titanium dioxide (TiO2); Toluene; VOCs; Volatile organic compounds; Photocatalytic oxidation (PCO); Air purification; By-products; Titanium dioxide (TiO2); Toluene; Methyl ethyl ketone (MEK)
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2018.05.002

Ultraviolet photocatalytic oxidation (UVPCO) is regarded as one of the promising technologies for indoor air remediation. The present study examines the photocatalytic activity of four commercialized titanium dioxide photocatalysts (P25, PC500, UV100, and S5-300A) in a small-scale single-pass continuous flow reactor. Challenge compounds have been chosen from two prevalent VOC families in indoor environment: toluene (aromatics) and methyl ethyl ketone (ketones). The influence of key experimental conditions including concentration (100–1000 ppb), relative humidity (0–50% at 23 °C), light intensity (1.25–5 W m−2), and residence time (0.02–0.1 s) on removal efficiency are evaluated. Due to the fact that one of the main shortcomings of PCO air purifiers is by-products generation, a special emphasis is put on identification and quantification of gaseous by-products using HPLC and GC-MS methods. The obtained efficiencies on various photocatalysts are explained considering crystalinity, crystalline phase, crystal size, surface area, and population of surface hydroxyl groups. Despite possessing lower crystalinity, PC500, UV100 and S5-300A outperformed P25 in toluene and MEK removal efficiency, primarily owed to their larger surface area, smaller crystal size, and higher concentration of surface hydroxyl groups. Acetone, acetaldehyde, and formaldehyde were identified as the main gaseous by-products in PCO of toluene and MEK. •The photocatalytic performance of four commercial TiO2 photocatalysts was examined.•Removal efficiency and by-product generation were assessed on various TiO2 samples.•Impacts of relative humidity, flow rate, concentration and light intensity were studied.•Interconnections between catalysts features and PCO activity were highlighted.