Air pollution from, for example, exhaust gases and cigarette smoke have a harmful effect on the environment and human health. For example, cigarette smoke can lead to heart and lung diseases, such as stroke, chronic obstructive pulmonary disease, emphysema, and lung cancer for both smokers and non-smokers who breathe in the secondhand smoke. In particular, cigarette smoke contains over 4,000 chemical compounds, which can bind with DNA to either kill human cells or cause genetic mutations in the DNA leading to cancer. Cigarette smoke includes many common carcinogens, such as polynuclear aromatic hydrocarbons produced by the pyrolysis of tar, acroleins, nitrosamines, nicotine, and ammonia, as well as large amounts of nitric oxide (NOx) and sulfur oxide (SOx).
Various methods for filtering exhaust gases and cigarette smoke have previously been disclosed. For example, micron-sized ceramic powders, such as aluminum titanate (Al2TiO5), mullite (3Al2O3-2SiO2), spodumene (LiAl(SiO3)2), eucryptite (LiAlSiO4), potassium titanate (K2Ti6O13), silica (SiO2), alumina (Al2O3), and clay mineral have been disclosed for removing soot from exhaust gases. In another example, activated carbon and graphite, both in granular and ball-shaped morphologies, have been disclosed to remove soot. In yet another example, heated porous ceramic membranes, such as porous zirconia (“zirconium dioxide”; ZrO2), alumina (“aluminium oxide”; Al2O3), silicon nitride (Si3N4), and/or a combination thereof, have been used to remove carbon particles. In addition, photocatalysts including titanium oxide (TiOx), zinc oxide (ZnOx), and iron oxide (FeOx), supported by activated carbon fiber have been used in air filters.
More recently, carbon nanotubes have been suggested for removing dust and adsorbing chemical vapors, such as ammonia (NH3), hydrofluoric acid (HF), hydrochloric acid (HCl), and organic gases. In addition, zeolites have been used for nitric oxide reduction.
However, previous filtering methods are relatively expensive and require frequent filter replacement. As such, a new, more efficient and economical filtering method for removing harmful airborne compounds is needed.