Photo-Regeneration of Zeolite-Based Volatile Organic Compound Filters Enabled by TiO2 Photocatalyst

Abstract

Indoor air filtration received significant attention owing to the growing threat to the environment and human health caused by air pollutants such as volatile organic compound (VOC) gases. However, owing to the limited adsorption capacity of VOC adsorbents, such as activated carbon, a rapid breakthrough can occur, reducing the service life of the filter. Therefore, TiO2-coated zeolite (TiO2/zeolite) was utilized as a photo-regenerative VOC adsorbent to increase the service life of VOC filters. In particular, with photoactive TiO2 forms on zeolite, efficient and repetitive photo-regeneration is attainable through the dissociation of VOC molecules by the photocatalytic reaction. We optimized the TiO2 coating amount to obtain TiO2/zeolite particles with a high surface area (BET surface area > 500 m2/g) and high adsorption capacity. A VOC filter with an adsorption efficiency of 72.1% for formaldehyde was realized using TiO2/zeolite as the adsorbent. Furthermore, the TiO2/zeolite filter exhibits a photo-regeneration efficiency of >90% for the initial two regeneration cycles using ultraviolet illumination, and >60% up to five cycles. Based on these observations, we consider that TiO2/zeolite is a potential adsorbent candidate for photo-regenerative VOC filters.