Novel Materials for Combined Nitrogen Dioxide and Formaldehyde Pollution Control under Ambient Conditions

Abstract

Formaldehyde (HCHO) and nitrogen dioxide (NO2) often co-exist in urban environments at levels that are hazardous to health. There is a demand for a solution to the problem of their combined removal. In this paper, we investigate catalysts, adsorbents and composites for their removal efficiency (RE) toward HCHO and NO2, in the context of creating a pollution control device (PCD). Proton-transfer-reaction mass spectrometry and cavity ring-down spectrometry are used to measure HCHO, and chemiluminescence and absorbance-based monitors for NO2. Commercially available and lab-synthesized materials are tested under relevant conditions. None of the commercial adsorbents are effective for HCHO removal, whereas two metal oxide-based catalysts are highly effective, with REs of 81 ± 4% and 82 ± 1%, an improvement on previous materials tested under similar conditions. The best performing material for combined removal is a novel composite consisting of a noble metal catalyst supported on a metal oxide, combined with a treated active carbon adsorbent. The composite is theorized to work synergistically to physisorb and oxidize HCHO and chemisorb NO2. It has an HCHO RE of 72 ± 2% and an NO2 RE of 96 ± 2%. This material has potential as the active component in PCDs used to reduce personal pollution exposure.

Perturbation of the UV transitions of formaldehyde by TiO2photocatalysts and Aunnanoclusters

“…One method for controlling formaldehyde pollution is using photocatalytic oxidation; 14 a recent trend is to add noble metal nanocatalysts to the photocatalyst for improved performance 15 or to use the nanocatalyst on a metal oxide support. 13 Ideally formaldehyde would be oxidized to carbon dioxide and water after being adsorbed on a catalyst surface, [16][17][18] although some CO will also be formed as an unwanted byproduct.…”

“…12 An effective method for formaldehyde removal could thus potentially benefit the health of many. 13 Further, an efficient mechanism for removing formaldehyde could be applicable to other VOC's containing ketone or aldehyde functional groups.…”

Formation of Formaldehyde and Other Byproducts by TiO2 Photocatalyst Materials

“…For another, few groups report the yield of CO 2 and H 2 O relative to the amount of pollutant consumed. Moreover, monitoring many byproducts including formaldehyde and multiply-oxygenated species requires special techniques that are not always available [53]. A full picture can only be given by considering the mass or atom budgets that describe how much reagent has been lost and which products have been formed, including byproducts.…”