Carbon Nanotube Filters for Removal of Air Pollutants from Mobile Sources

The aim of this work was the assessment of the removal of air pollutants from mobile sources by commercial carbon nanotubes (CNTs). For this, the nano-material was characterized by different techniques: SEM, EDS, TEM, XRD, BET, and Raman. Subsequently, the CNTs were packed in stainless steel filters which were designed from different prototypes developed during the investigation. Tests were performed in the TO-913 Verificenter Macrover Auto SAQ. Inc. de CV. The results revealed that particle type and CNTs loading had greater effects on the efficiencies than the membrane type and pore sizes tested. When collecting NOx, efficiencies were observed to be relatively lower, below 20% for loadings of 0.3 - 1.5 mg/cm². The studied CNTs were multi-walled: two layers, showed nonlinear growth and varied morphology due to different diameters and lengths; half of the nanotubes were coated with amorphous carbon. The composition is mainly carbon and oxygen, with iron also present. The adsorption capacity of CNTs was significantly influenced by factors such as model, brand, fuel, year, and conditions of each car. The removal efficiencies of CNT filters ranged from 10% to 95% on average for CNT loadings of 0.2 - 1.6 mg/cm², while efficiencies for CO, CO2, NOx, and HC ranged from 5% to 60% under similar CNT loadings.