Application of Graphene Oxide Aerogel to the Adsorption of Polycyclic Aromatic Hydrocarbons Emitted from the Diesel Vehicular Exhaust

Abstract

For reducing the carcinogenic BaP and polycyclic aromatic hydrocarbons (PAHs) from the moving and stationary pollution source in the atmosphere, this study demonstrated useful adsorbent of graphene oxide aerogel (GOA). The application of GOA to the adsorption of polycyclic aromatic hydrocarbons (PAHs) emitted from diesel vehicular exhaust via the dynamometer was investigated. The surface morphology and microstructure of GOA were characterized by SEM, TEM, elemental analysis, Raman, and TGA. According to the result of XRD, the grain size of GOA after 5 hours of oxidation time increased to 28.0 nm with 38 layers estimated. It demonstrated that more oxidation time greatly enhanced the crystalline structure and reformation between the GOA sheets. The GOA sheets possessed the molecular sieving property for the filtration and adsorption of carcinogenic PAH molecules due to the strong hydrogen bonding interaction along the edges and the Van der Waal's force interactions. Naphthalene, acenaphthene, benzo[a]pyrene (BaP), and dibenz[a,h]anthracene, were chosen to carry out the pre-test adsorption experiments. Especially, the BaP compound was known to be carcinogens and mutagens for humans because of their carcinogenicity and genotoxicity. From the result of pre-test adsorption of PAHs, the BAP adsorption capacity of the GOA adsorbent (310 ng BaP / 1 g GOA) in 1 hour was much better than that of XAD16 resin (0.060 ng / 1 g XAD16), which is the standard adsorbents of PAHs announced by the Environmental Protection Administration of Taiwan. Furthermore, the sample collection of PAHs emitted from the diesel exhaust was performed by using the vehicle dynamometer. At the idling speed, the best adsorption capacity of total PAHs per gram GOA was 12.1 μg g−1, and better than that of XAD16 (1.03 μg g−1). Moreover, the adsorption sleeve and adsorbent of GOA material could be recycled and reused repeatedly. The structure of the GOA adsorbent has maintained after three runs of the Soxhlet extraction and drying. Nevertheless, the structure of XAD16 resin is decomposed obviously and decreased after the Soxhlet extraction. Owing to the superior adsorption capacity of PAHs and low synthesis cost, the GOA material is possible to be one of the excellent environmental and air pollution adsorbent material in the future.