Treatment of Air Containing Volatile Organic Carbon: Elimination and Post Treatment

The degradations of toluene (with a concentration of 2–20 ppmv) in the gas phase by UV, O3, O3/UV, TiO2/UV, O3/TiO2, 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 were followed. The experimental results showed that UV and O3 alone did not eliminate a significant amount of toluene. However, the combination of these two processes (UV/O3) could improve the conversion of toluene. Further, toluene conversion, at high inlet concentration, can be achieved when a catalysis was added to this process (UV/O3/TiO2). Toluene decomposition was found to be inversely dependent on flow rate (i.e., retention time); low conversion at high flow rate, and high conversion at low flow rate. The UV/O3 process was found to be more affected by gas relative humidity, and an optimal humidity of 50%, under experimental condition was determined. The conversion levels obtained with UV254 + 185 nm photo-irradiated were much higher than those with conventional UV sources (UV emits light at a wavelength at λ = 365 nm and UV emits light at a wavelength at λ = 254 nm). The products from the photodegradation of volatile organic compounds were water-soluble organics. The water-soluble organics were found to have noticeable biodegradability. Thus, a post-treatment of a washing technique followed by biological treatment can be proposed.