Performance extrapolation of an ultraviolet-based photocatalytic air purifier against near-ambient-level formaldehyde

The practical utility of an air purifier (AP) with built-in adsorbent/catalyst-based filtration systems is assessed for the treatment of indoor volatile organic compounds (VOCs) through extrapolation of its performance based on a lab-scale chamber study. The feasibility of a commercial prototype AP unit with TiO2-based filters is tested in this work against 0.5-5 ppm formaldehyde (FA) in a 17 L chamber with an air recirculation rate of 565 h(- 1) under the control of key process variables (e.g., initial FA concentration, flow rate, and dark/light conditions). The performance of the AP unit is evaluated by the clean air delivery rate (CADR), quantum yield, and space time yield in diverse operation settings (e.g., photocatalysis only or along with adsorption). The effects of ultraviolet (UV) irradiation are evident as the CADR value of 5 ppm FA sharply increases from 5.67 (UV-off) to 15 L/min (UV-on): however, the CADR values increase only slightly (12 to 15 L/min) as the recirculation flow rate changes from 100 to 160 L/min, respectively. Further, FA concentration vs. time relationship exhibit an apparent bimodal exponential decay, with the fastest and near 100 % removal at [FA] <0.5 ppm. The performance of the proposed AP platform in relatively large real-world volume (e.g., 4 m(3), 2.4 h- 1 air recirculation rate) is further estimated through extrapolation to offer valuable guidelines for the construction of AP systems in real-world applications.