Granular-activated carbon adsorption followed by annular-type photocatalytic system for control of indoor aromatic compounds

An adsorbent coupled with other control devices may enhance the removal of various indoor pollutants, including indoor benzene, toluene, ethyl benzene, and xylene (BTEX). In addition, the regeneration of adsorbent is subsequently required for reusing and lowering disposal cost. Accordingly, this study investigated the technical feasibility of an activated carbon (AC)–photocatalytic oxidation (PCO) hybrid system connected in series for AC regenerations as well as for controls of indoor air levels of BTEX. The hybrid system presented higher removal efficiencies (close to 100%) compared to the AC unit alone. Unlike the AC unit alone, the relative humidity or inlet concentration dependence was insignificant for the hybrid system. The desorption efficiency of the AC unit was between 75 and 94% for the desorption temperature of 300 °C. PCO efficiencies of BTEX desorbed from the AC unit represented relatively high degradation efficiencies for low loadings ≤5000 ng (above 70%). An elevated CO concentration by PCO processes was a negligible addition to indoor CO levels. The hybrid system could enhance control efficiency of BTEX in indoor air levels compared with AC adsorption alone, without a significant CO generation. Under certain conditions, the PCO unit located downstream from the adsorbent unit could effectively be employed for AC regeneration.