Formaldehyde Abatement by Photocatalysis: Fast Detection by PTR- MS

Formaldehyde is the simplest aldehyde and belongs to the family of VOCs (Volatile Organic Compounds), which consistently contribute to the increase of the atmospheric pollution, both outdoor and indoor; Formaldehyde in particular is easily found in the indoor environments, being a molecule present in a lot of substances of common use. Recently, the regulations about its dangerousness have been modified: it has been added to the mutagenicity hazard class and passed from category 2 (suspected carcinogen) to category 1B (carcinogen); therefore, all the obligations about health and safety are now much more stringent [1]. Several analytical techniques have been developed to detect atmospheric formaldehyde even if, if the aim is following a photocatalytic reaction in a short time interim, the time requested for the analysis, the very low stability of the molecule and the by-products formation as well, could be a problem. Proton transfer reaction mass spectrometry (PTR-MS) is an online technique that allows measurement of VOCs at the sub-ppbv level with good time resolution; recently, it was used to measure concentration of HCHO [2,3] with a lot of advantages including high time resolution and the ability to simultaneously detect a large number of VOC compounds [4]. The photocatalytic abatement by three TiO2 commercial samples and some photoactive industrial tiles prepared using a micrometer titania, were tested by means of a PTR-MS instrument. All the formaldehyde photodegradation kinetics have been followed successfully. The results are consistent with the typical features of the different samples of titania, in particular related to their particles dimensions. Formaldehyde, methanol, and formic acid have been contemporarily and constantly monitored, checking the humidity and the temperature inside the reactor. The possibility to use the PTR-MS instrument for studying a photocatalytic process is shown, introducing several new possibilities related to its high sensitivity, the high time resolution and the possibility to monitor several compound simultaneously.