Investigation of the Photocatalytic Oxidation of Low-Level Carbonyl Compounds

Though the bulk of research involving photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) has involved the remediation of pollutants at high inlet concentrations, there has been some implication that PCO can be used to reduce exposure to low concentrations of VOCs and improve the quality of indoor air. The high conversion rates previously reported for PCO of VOCs in theparts-per-million (ppm) range may not, however, be applicable to concentrations in the parts-per-billion (ppb) range that are more typical of indoor air quality (IAQ) issues. This paper reports on an examination of the operational characteristics of four PCO reactor designs used for the oxidation of VOCs in the ppb concentration range. Reactor efficiency is examined for three low molecularweight carbonyl compounds commonly associated with IAQ issues: formaldehyde, acetaldehyde, and acetone. The measured response is the destruction of carbonyl reactants. Variables include flow stream velocity and reactor residence time. Oxidation of carbonyl compounds is also examined as a function of ultraviolet (UV) radiation intensity. PCO of the formaldehyde and acetone was nearly 100% for allreactor designs. To assist comparison of the reactor designs, oxidation efficiency of trichloroethylene (TCE) was evaluated at inlet concentration in the parts-per-million by volume (ppmv) range.