UV-PCO device for indoor VOCs removal: Investigation on multiple compounds effect

Current design models for ultraviolet photocatalytic oxidation (UV-PCO) devices often assume that the air contains only one volatile organic compound (VOC) species or all the VOCs in the air can be treated on a non-interacting basis. However, trace-level multiple VOCs co-exist in most indoor environments. This paper assesses the significance of interference effects among different VOCs for indoor applications by full-scale “pull-down” experiments assisted with model simulations. Multiple versus single VOC tests were performed on selected groups of compounds under low concentration levels. Removal efficiency for each compound was calculated. It was found that the interference effect among test VOCs were generally small in the 2-VOC and 3-VOC mixture tests performed on toluene, ethylbenzene, octane, decane and dodecane with initial concentration of approximate 1 mg/m³ for each compound. However, in the 16 VOC mixture test, the interference effect among different VOCs became quite obvious, and compounds with lower removal efficiency in the single compound test appeared to also have relatively lower efficiency and more obvious delay period in the initial reaction. The L–H model appears to be able to account for this effect if reaction rate constants can be accurately estimated. Results, although limited, indicate that interference between multiple VOCs may not be neglected for the PCO reactor for indoor applications where the number of VOCs species is large and the TVOC concentration is high.