Photo-Catalytic Oxidation Technology for VOC Control: Evaluation and Risk Characterization of Intermediates of Benzene Degradation Adsorbed on Catalyst

Abstract

Abstract

A sol-gel-based TiO₂-coated photo-catalytic device was developed and demonstrated for field applications for controlling volatile organic compounds (VOCs) in three varying indoor environments: (i) laboratory using benzene (efficiency >99%), (ii) conference room of an industry producing organic solvents (mono, di, and tri chloro benzene) (efficiency >70%), and (iii) chemistry laboratory using multiple solvents/VOCs (efficiency >88%). The VOC degradation rate constant for coexisting multiple VOC was estimated to be 1.06/min/m², which was about 34% less than that of benzene. A VOC mass balance model was developed to describe interaction between indoor air and kinetics of VOC degradation to estimate required extent of treatment for safe VOC concentration in the indoor air. Toxic intermediates of benzene that were adsorbed on the catalyst surface (solid phase) were identified and quantified with GC/GC-MS (gas chromatography-mass spectroscopy). Intermediates accounted for less than 5% of the total mass of benzene treated. The overall hazard index of the toxic intermediates released from regeneration of catalyst is estimated in the range 0.11–0.74, which is less than 1, and, thus, poses no significant risk to the occupants.