Effect of VOC loading on the ozone removal efficiency of activated carbon filters

Activated carbon (AC) filters are used widely in air cleaning to remove volatile organic compounds (VOCs) and ozone (O3). This paper investigates the O3 removal efficiency of AC filters after previous exposure to VOCs. Filter performance was tested using coconut shell AC and two common indoor VOCs, toluene and d-limonene, representing low and high reactivities with O3. AC dosed with low, medium and high loadings (28–100% of capacity) of VOCs were exposed to humidified and ozonated air. O3 breakthrough curves were measured, from which O3 removal capacity and parameters of the Elovich chemisorption equation were determined. VOC-loaded filters were less efficient at removing O3 and had different breakthrough behavior than unloaded filters. After 80 h of exposure, VOC-loaded AC samples exhibited 75–95% of the O3 removal capacity of unloaded samples. O3 breakthrough and removal capacity were not strongly influenced by the VOC-loading rate. Toluene-loaded filters showed rapid O3 breakthrough due to poisoning of the AC, while pseudo-poisoning (initially higher O3 adsorption rates that rapidly decrease) is suggested for limonene-loaded filters. Overall, VOC loadings provide an overall reduction in chemisorption rates, a modest reduction in O3 removal capacity, and sometimes dramatic changes in breakthrough behavior, important considerations in filter applications in environments where both O3 and VOCs are present.