Titanium Dioxide (TiO2)-assisted Photocatalytic Degradation of Volatile Organic Compounds at ppb Level

Abstract

Titanium dioxide (TiO2)-assisted photodegradation of volatile organic compounds (VOCs), especially malodorous substances at ppb level in closed air are reported. As target VOCs we selected acetaldehyde, dimethyl disulfide (DMDS), dimethyl sulfide (DMS) and methyl mercaptan, because of their toxicity and unpleasant odor at low concentration in closed air. The initial concentrations were fixed at 0.4-5.0 ppm for acetaldehyde, 0.03 ppm for DMDS and DMS and 0.02 ppm for methyl mercaptan respectively. A blacklight UV-lamp was employed as a light source and the intensity of UV-light was controlled at 1.0 mW/cm2 (351 nm). The half life of these odorous substances was from 20 min to 120 min and pseudo-first-order reaction rates were 1.1×10-2 min-1 (acetaldehyde), 1.4×10-2 min-1 (DMDS), 4.8×10-2 min-1 (DMS) and 8.0×10-3 min-1 (methyl mercaptan). One of the by-products of TiO2 photodegradation of acetaldehyde was identified as formaldehyde by liquid chromatography/mass spectrometry (LC/MS). These basic data of TiO2 photodegradation for odorous substances will be useful for the construction of an air purification system using TiO2 photodegradation in closed air, for example in living rooms, hospitals and care rooms.