Photocatalytic Degradation of Polycyclic Aromatic Hydrocarbons in Fine Particulate Matter (PM2.5) Collected on TiO2-Supporting Quartz Fibre Filters

Airborne fine particulate matter (PM2.5) pollution is known to have adverse effects on human health, and owing to their carcinogenic and mutagenic nature, polycyclic aromatic hydrocarbons (PAHs) are of particular concern. This study investigated the effect of ultraviolet (UV)-induced photocatalysis on the degradation of PAHs in PM2.5, employing titanium dioxide (TiO2)-supporting quartz fibre filters. A TiO2 layer was formed on the quartz fibre filters, and airborne PM2.5 was collected using an air sample at a flow rate of 500 L/min for 24 h. The PM2.5 samples were subsequently irradiated with ultraviolet rays at 1.1 mW/cm(2). The amounts of nine targeted PAHs (phenanthrene, PHE; anthracene, ANT; pyrene, PYR; benzo[a]anthracene, BaA; chrysene, CHR; benzo[b]fluoranthene, BbF; benzo[k]fluoranthene, BkF; benzo[a]pyrene, BaP; and benzo[g,h,i]perylene, BgP) gradually decreased during the treatment, with half-lives ranging from 18 h (PHE) to 3 h (BaP), and a significantly greater reduction was found in comparison with the PAHs collected in the control (non-TiO2 coated) quartz fibre filters. However, the degradation rates were much faster when the PAHs were in direct contact with the TiO2 layer. As PM2.5 is a mixture of various kinds of solids, co-existing components can be a rate-determining factor in the UV-induced degradation of PAHs. This was demonstrated by a remarkable increase in degradation rates following the removal of co-existing salts from the PM2.5 using water treatment.