Investigation of the photocatalytic oxidation of low-level carbonyl compounds

Though the bulk of research involving photocatalytic oxidation (PCO) of vol atile organic compounds (VOCs) has involved the remediation of pollutants a t high inlet concentrations, there has been some implication that PCO can b e used to reduce exposure to low concentrations of VOCs and improve the qua lity of indoor air. The high conversion rates previously reported for PCO o f VOCs in the parts-per-million (ppm) range may not, however, be applicable to concentrations in the parts-per-billion (ppb) range that are more typic al of indoor air quality (IAQ) issues. This paper reports on an examination of the operational characteristics of four PCO reactor designs used for th e oxidation of VOCs in the ppb concentration range. Reactor efficiency is e xamined for three low molecular weight carbonyl compounds commonly associat ed with IAQ issues: formaldehyde, acetaldehyde, and acetone. The measured r esponse is the destruction of carbonyl reactants. Variables include flow st ream velocity and reactor residence time. Oxidation of carbonyl compounds i s also examined as a function of ultraviolet (UV) radiation intensity. PCO of the formaldehyde and acetone was nearly 100% for all reactor designs. To assist comparison of the reactor designs, oxidation efficiency of trichlor oethylene (TCE) was evaluated at inlet concentration in the parts-per-milli on by volume (ppmv) range.