Removal of hazardous pollutants from air is an important application area with significant impact on human health and quality of life. Portable home air filters, personal protection respirators, and large scale filtration systems installed in buildings are examples of air filtration products widely used to improve air quality and prevent exposure to harmful pollutants. Air filters removing chemical pollutants, gases, or vapors, are frequently used in facilities using toxic chemicals or in buildings where such pollutants may be present.
The majority of air systems only focus on particle filtration. These devices may use a combination of traditional Minimum Efficiency Reporting Value (MERV) rated filters and high-efficiency particulate air (HEPA) filtration. Some devices add in solid sorbents, most commonly carbons, which capture air pollutants by means of physical absorption. Such filters have only limited removal capacities and often no destructive capabilities resulting in the odor chemical contaminates being released back into the environment which is a major drawback of traditional carbon-based filtration systems and the main factor limiting their wider applications effectiveness.
Comparison to Carbon
Carbon is a commonly used material in odor control applications. It absorbs odors; however it does have several serious disadvantages. Most significantly, carbon only physisorbs toxic, noxious, and other odor causing molecules, meaning that the unwanted chemicals do not react chemically with the carbon and can be released them later and cause the re-emergence of an odor believed to have been initially neutralized or eliminated. Changes in humidity or temperature can hasten this process, causing the odors and other unwanted chemicals to be released back into the air.
Multiple studies exposing NanoActive metal oxides and carbon compounds to common odor-causing chemicals through breakthrough and packed bed reactors have been conducted. These included exposure at ambient conditions with variable vapor and gaseous chemicals of different classes including acids, bases, organics, and noxious chemicals.
The filtration capabilities of NanoActive metal oxides were compared to carbons where the chemically exposed solids were heated and the identities of the evolved vapors were determined by infrared spectroscopy. The process of heating the sample accelerates the off gassing (or release) of the chemical if it is not chemically broken-down or bonded to the media. Table 2 illustrates the desorption results carbon has with a variety of chemical classes in comparison to NanoActive materials. NanoActive materials can be combined, blended, and added to other compounds to increase or optimize efficacy against a particular chemical or odor.
Table 2: Comparisons of Agent Desorption/Offgassing Properties of NanoActive and Carbon Media.