Performance of ultraviolet photocatalytic oxidation for indoor air cleaning applications

Abstract

Implementation of air cleaning technologies for both VOCs and particles in office buildings may improve indoor air quality, or enable indoor air quality levels to be maintained with reduced outdoor air supply and concomitant energy savings. One promising air cleaning technology is ultraviolet photocatalytic oxidation (UVPCO) air cleaning. For the prototype device evaluated here with realistic mixtures of VOCs, conversion efficiencies typically exceeded the minimum required to counteract predicted VOC concentration increases from a 50% reduction in ventilation. However, the device resulted in the net generation of formaldehyde and acetaldehyde from the partial oxidation of ubiquitous VOCs. Further development of the technology is needed to eliminate these hazardous air pollutants before such a UVPCO device can be deployed in buildings.

Effect of key parameters on the photocatalytic oxidation of toluene at low concentrations in air under 254+185nm UV irradiation

“…In that range, the toluene conversion efficiency increased from ~ 30 to 90%, indicating that, under all the experimental conditions, the system did not achieve complete conversion. Previous studies showed that at such low toluene concentrations, the removal efficiency was shown to be independent of the initial concentration [13,15] which suggested low coverage of the catalyst surface and first-order dependence on toluene concentration. In our case, for a given flow rate, the removal efficiency observed at the longest reactor length (L = 10 cm) was significantly higher than that observed for L = 5 cm (Figure 3-A).…”

“…Recently, a few studies investigated the removal performance of UVPCO at low VOC concentrations comparable to those encountered in buildings [11][12][13][14][15]. With VOC concentrations in the ppbv range, the low catalyst surface coverage led to different kinetics and mechanisms with respect to reactions using high gas phase concentrations (in the ppmv range), and the competition between different VOCs for reactive surface sites was shown to be insignificant.…”

“…With VOC concentrations in the ppbv range, the low catalyst surface coverage led to different kinetics and mechanisms with respect to reactions using high gas phase concentrations (in the ppmv range), and the competition between different VOCs for reactive surface sites was shown to be insignificant. Results from a full-size UVPCO air cleaner prototype, which was sized to meet the requirements of a small office building, indicated that: a) the UVPCO unit was able to reduce VOC concentrations in the 20-80% range for a wide range of typical indoor pollutants, being more efficient for polar, hydrophilic compounds (e.g., alcohols); b) formation of partial oxidation byproducts was significant, and included indoor pollutants of concern such as formaldehyde and acetaldehyde; and c) the generation of these harmful byproducts could be controlled by post-treatment with sorbent and chemisorbent materials placed downstream of the UVPCO unit [12,13].…”

Efficiency of Clay−TiO2 Nanocomposites on the Photocatalytic Elimination of a Model Hydrophobic Air Pollutant

“…Recently, photocatalytic 6 performance with ppbv-level VOC concentrations has also been reported (4,42). Here, we investigate the potential of these reactions at VOC concentrations that occur in buildings (in the low ppb range), by applying sampling and analytical techniques commonly used in indoor air quality characterization (43).…”

Preparation of TiO2-Coated Polyester Fiber Filter by Spray-Coating and Its Photocatalytic Degradation of Gaseous Formaldehyde

“…The application of heterogeneous photocatalytic oxidation (PCO) for air purification has been investigated intensively in the past two decades, particularly in converting indoor air volatile organic compounds (VOCs) into less toxic minerals, carbon dioxide and water (Zhao and Yang, 2003;Hodgson et al, 2007). This technique carries certain advantages such as: utilizing UV and/or visible light as initialization energy; non-selectivity of organic pollutants; potential to complete mineralization into CO 2 and H 2 O; and persistent effectiveness throughout the lifetime of the photocatalyst under ambient temperature.…”