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

Hugo S Russell,Magdalena E G Hofmann,Marten In ‘T Veld,Matthew S Johnson,Jakob B Pernov,Hasse C Knap,James Bonomaully,Rossana Bossi

doi:10.3390/catal10091040

Hugo S Russell, Magdalena E G Hofmann + Show 6 more

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https://doi.org/10.3390/catal10091040

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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.

Highlights

Harmful levels of air pollution are a reality across the globe, and excess mortality due to all air pollutants is estimated at 8.8 million deaths per year [1,2]
Prior to the quantitative tests, an initial removal efficiency (RE) screening was performed in the chamber and single-pass setups for all of the materials described above
This sample was uncharacterized, but, in the literature, it is seen to have pores with an average diameter in the mesopore region, which may be too large for effective physisorption of HCHO, as well as a low surface area and minimal functional groups [36]

Summary

Introduction

Harmful levels of air pollution are a reality across the globe, and excess mortality due to all air pollutants is estimated at 8.8 million deaths per year [1,2]. Air pollution has many components in both the gas and particulate phase. Both formaldehyde (HCHO) and nitrogen dioxide (NO2 ) are of specific concern and are linked with health impacts due to their elevated levels in indoor environments including homes, offices and cars. Products have been developed with the aim of removing these pollutants individually. While reasonable NO2 control systems exist, only limited success has been achieved for HCHO removal, and a solution has not been found for the combined removal of NO2 and HCHO.

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