A comparative study on decomposition of gaseous toluene by O3/UV, TiO2/UV and O3/TiO2/UV

The degradations of trace toluene (1.0–20 ppmv) in the gas-phase by O3/UV, TiO2/UV and O3/TiO2/UV were studied. The effects of the inlet concentration of toluene, flow rate (retention time), relative humidity and ultraviolet (UV) light wavelength on the conversion of toluene in the three processes were examined, respectively. The experimental results showed that the addition of ozone to the photocatalysis process could greatly increase the conversion of toluene. In particular, the deactivation of the photocatalyst at high inlet concentration of toluene was avoided in the presence of ozone. The O3/TiO2/UV process was more efficient than the O3/UV in decomposing toluene in most cases. And the residual ozone concentration in the O3/TiO2/UV process was much lower than that in the O3/UV process. Among them, combined photocatalysis and ozonation (O3/TiO2/UV) was the most prospective process for removing trace volatile organic compounds (VOCs) such as in indoor air.